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Executive Summary of the 
Bureau of Mines Investigations in the 
Valdez Creek Mining District, Alaska 


a ely 
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COVER - View of Denali and the Chulitna River Valley from the top of Indian Mountain. 


Executive Summary of the 
Bureau of Mines Investigations in the 
Valdez Creek Mining District, Alaska 

By Michael D. Balen and others 

Manuel Lujan, Jr., Secretary 


T S Ary, Director 
BLM Library 
Denver Federal Center 
Bldg. 50, OC-521 
PO. Box 25047 
Denver, CO 80225 

Special Publication 

FIGURE 1. - Bureau geologist collects a rock sample near the terminus of the Maclaren Glacier. 


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3. The Black River looking towards the eastern Talkeetna Mountains ........ 











View up the Susitna River looking towards the Alaska Range, Clearwater 
Mountains areas 34 06 ee ee Be oe ee ee 
The original adit on the Tammany paleochannel, circa 1915 ........... 
Gold sluicing operation'on Valdez: Creek, circasl915 7 
Placer'mining on Valdez.Creek, circasl920 So 203 meer eee reer 
Denali gold placer open-pit mining operation on Valdez Creek, 1989 ...... 
Mineral property location map for selected mineral deposits in the 

Valdez Creek Mining District, -Alaska yes ee eee 
Actial view of the GoldenrZone* mine, 1988s 9 nee ee 
Mining operation on Busch Creek showing the jig plant gold recovery system . 
Generalized geologic terrane map for the Valdez Creek Mining District 

Bureau geologist collecting a sample near the headwaters of the Black River, 
Tatkeetna Mountains physiographic province = 577). 2-5) 
Bureau geologist at the discovery outcrop of the McCallie Glacier occurrence . 
Bureau geologist examining the ultramafic occurrence in the Butte 

Creek: drainages ycviaecuce on Sar ee ec ee eee ee 
View up the Maclaren River valley from the Denali highway at the Maclaren 
River Crossing *, 3 SP i fA ye oe eee ee ee 
Regions favorable for the occurrence of placer gold” 7.33.) nee 
Regions favorable for the occurrence of metamorphic gold veins, basalt-hosted 
copper, sediment-hosted and basalt-related copper, and volcanogenic massive 
SULETAES vc “Wer Re eee eee nats eg cet ll, pa Ss ae oh 
Regions favorable for the occurrence of plutonic associated gold-bearing 

veins, ultramafic associated podiform chromite, and carbonate-hosted gold- 
SIIVET. ooh tbat Vers Veen ake etek miata ee ee a 
Regions favorable for the occurrence of porphyry molybdenum and copper, 
tin-bearing polymetallic veins, copper-gold skarns, and ultramafic 

associated nickel-copper-PG My SULiId eS yay tame sues ee 
Bureau geologist collecting a placer sample from a tributary to the Susitna 
Glaciety oi. Beka ek ee eee dese 5 a ae este ne ee 
Bureau geologist collecting a rock sample near the source of the Susitna 

RIVOD Ee 60.3 gk Sve gous he othe oe Pete es ee =e a te 

VGMD‘deposititypes andidescriptions sana. see eee 

Publications, by Bureau authors, resulting from the VCMD investigation... . 
Summary of results from samples collected at the Devils Canyon occurrence 


— Re RS eS 
\O en hey (oer fen Oorni idm i 












Mineral deposit models and associated mine models used in the mining 
feaSiDILiivestUCVsOCMINCAV CIV Be ae ee Meter. Siete ss. ue. tac so 29 
Estimated total endowment for the most significant metals in the VCMD .... 31 
Estimated summary endowment for the VCMD, by deposit type, expressed as 

10° oz gold equivalents 



Symbol | Definition 

_ degree Fahrenheit 


of the 

in the 


By Michael D. Balen’ and others 


Duns the years 1987 through 1989, the 

Bureau of Mines Alaska Field Opera- 
tions Center (Bureau) in cooperation with 
the Western Field Operations Center and the 
Alaska Division of Geological and Geo- 
physical Surveys (ADGGS), conducted 
mining, geological, and geochemical investi- 
gations in the 5.7 million-acre Valdez Creek 
Mining District (VCMD). This investigation 
was conducted as part of the Bureau’s 
continuing Mineral Land Assessment (MLA) 
mining district studies program. 

The Bureau’s MLA program is designed to 
provide reliable and comprehensive mineral 
resource information that supports mineral 
resource policy and land use decisions made 
by Congress and Federal land management 
agencies. The information also provides the 
basis for decisions that would expand the 
domestic supply of important mineral 

resources, primarily strategic and critical 
minerals. Much of the MLA work is done 
jointly with cooperating State or U.S. 
geological surveys. 

Section 1010 of ANILCA? authorizes the 
Secretary of the Department of the Interior 
to assess the oil, gas, and other mineral 
potential on all public lands in the State of 
Alaska in order to expand the data base with 
respect to the mineral potential of such 

Sixty-seven mining districts in Alaska have 
been defined by Ransome and Kerns (1)’. 
After consultation with State and Federal 
land managers, mining districts selected for 
investigation are prioritized by the Bureau 
on the basis of availability of data, need for 
additional data, national need for contained 
commodities, and physical access. 

The Bureau’s investigative work for each 
district takes an average of 4 years to 
complete. The first year is spent in 

' Mining Engineer, Alaska Field Operations Center, Anchorage, Alaska. 

2 Alaska National Interest Lands Conservation Act. 

3 Underlined numbers in parentheses refer to citations that appear in references at the end of this report. 

literature search and data compilation, and 
initial field reconnaissance of the mining 
district. During the second and third years, 
field work to acquire all data necessary to 
establish the mineral data base on which the 
evaluation is based is conducted. The fourth 
year is devoted to compilation of all data, 
completion of complementary studies from 
data acquired in the first three years, and 
preparation of the final report. The final 
product is published as an _ executive 
summary and special publication. During 
the course of the project, open file reports 
(OFR) are published yearly which describe 
the work completed to date and the 
significant data collected. 

The objectives of the VCMD investigation 
were to (1) evaluate the mineral resources of 
the VCMD, (2) perform theoretical mining 
feasibility studies, (3) study the application 
of modern beneficiation technologies on 
known deposits, and (4) perform a 
probabilistic mineral resource and economic 
assessment of the mining district. 

During the course of the WCMD 
investigation, Bureau field personnel 
discovered 19 previously unreported mineral 
occurrences within the _ district. 
Reconnaissance placer sampling resulted in 
the identification of 10 previously unreported 
gold placer occurrences, some of which 
contain subsidiary placer platinum group 
metals (PGM) or tin, or _ both. 
Reconnaissance lode sampling resulted in the 
identification of 2 gold-silver occurrences, 3 
PGM occurrences that contain subsidiary 
chromium, nickel and/or cobalt, 3 copper 
occurrences that contain subsidiary 
molybdenum or zinc, and 1 zinc occurrence. 

This document (1) discusses pertinent 
recent and historical information about the 
VCMD, (2) summarizes the findings of 
Bureau work that has been performed in the 
VCMD to date, and (3) can be used as a 

principal reference to information on 
government geological research and mineral 
resource evaluation in the VCMD. 


Loe in the south-central portion of 

Alaska, the VCMD is geographically 
defined by the portion of the Susitna River 
drainage basin upstream from the Talkeetna 
River confluence (fig. 2). Bounded on the 
north by the crest of the Alaska Range, on 
the west by the Mt. McKinley massif, on the 
south by the Talkeetna Mountain Range, and 
on the east by the Lake Louise Plateau (2), 
the VCMD encompasses a vast, diverse 


Tp he VCMD comprises Federal, State, and 

private land holdings. Figure 2 shows a 
generalized land status map for the district. 
Current land status for specific areas can 
most accurately be determined by reviewing 
the Master Title Plats at the Bureau of Land 
Management (BLM) Public Lands Office in 
Anchorage, Alaska. Federal lands are 
administered by the BLM and the National 
Park Service (NPS); State lands are 
administered by the Department of Natural 
Resources (DNR), Division of Land and 
Water Management. 


ortions of the VCMD are accessible from 

the Parks, Denali, and Glenn Highways, 
which are the major roads within the 
district. Poorly maintained mining roads 
and hunting trails provide limited access to 
some back-country areas for 4-wheel-drive 
or off-road vehicles. The most practical 
method of access to most of the VCMD is 


147 °00' 


148°00' 147 

148 °30' 


149 °30' 


150 °30" 

151° 00° 

151" SO! 

Scale, mile 







Valdez Creek Mining District 







Mount McKinley a 




62 °45' 

62° 15° 




{62° 30° 


N 2 
‘S 2 
2 cc 
; oe 


Via State/Native selected lands 

to mineral entry 

Reg Federal/State lands closed 

146° 30’ 

147° 00’ 

147° 30° 

148 *00° 

148° 30° 

149 *00’ 

149 °30° 

150° 00’ 

150° 30’ 

151° 00" 









District, Alaska. 



FIGURE 2. - Land status map for the Valdez Creek 

FIGURE 3. - The Black River looking towards the eastern Talkeetna Mountains. 

by helicopter or small fixed-wing aircraft. 
Access by shallow-draft boat is possible on 
some of the larger rivers such as the Susitna, 
Chulitna, and Maclaren Rivers. The Alaska 
Railroad parallels the Parks Highway in the 
western portion of the district. 


he physical geography of the VCMD 
comprises a wide variety of features. 
Periglacial landforms predominate through- 
out the region. Rugged mountains with 
elevations as high as the 20,320-ft Mt. 
McKinley massif host the snow fields that 

inaugurate the descent of thick glaciers into 
"U"-shaped valleys. Some glaciers, such as 
the Ruth, stretch as far as 30 miles from 
their highest cirques. Approximately 63% 
(5,598 mi’) of the land surface within the 
VCMD is higher than 3,000 ft above mean 
sea level (m.s.1.), and 6% (536 mi’) lies 
higher than 6,000 ft above m.s.1. Treeline 
throughout the VCMD ranges from 2,500 to 
3,000 ft above m.s.1. 

The entire district lies within the boreal 
forest belt that surrounds the globe in the 
high latitudes of the Northern Hemisphere. 
Vegetation communities present in the 
district are classified as members of the taiga 

biome. Wetlands are vegetated with sedge 
grasses, tamarack, and stunted black spruce. 
Low-elevation valley bottoms are vegetated 
with cottonwood, birch, and white spruce. 
With increasing elevation, the mixed forest 
gives way to white spruce and aspen forests. 
An undergrowth of willow, alder, and 
sphagnum moss is ubiquitous below treeline. 
Above treeline, the forest gives way to 
shrubland and tundra. Figures 3 and 4 show 
typical views of the VCMD landscape. 
Nearly all Alaskan species of wildlife can 
be found within the VCMD. Moose, 
caribou, grizzly and black bear are the most 
visible animals; they range throughout the 
region. Beaver, muskrat, geese, and ducks 
populate the wetlands in valley bottoms and 
lower elevations. Dall sheep and ptarmigan 
inhabit the high peaks of the Talkeetna 
Mountains and the Alaska Range. Fox, 
coyote, wolf, porcupine, marten, mink, 
lynx, rabbit, grouse, wolverine, and several 
species of raptor are also VCMD residents. 
Cool, rainy summers and cold, snowy 
winters are the norm throughout most of the 

district. Average midwinter temperatures 
range from -10°F to +10°F, and average 
midsummer temperatures range between 
+40°F and +60°F. Temperatures as low 
as -64°F, and wind chill temperatures below 
-100°F, have been recorded in the district. 
At the opposite end of the scale, summer- 
time temperature extremes have exceeded 
+96°F. Seasonal snowfall in the VCMD 
has exceeded 21 ft in portions of the 
Chulitna River valley (3). 

The VCMD is sparsely populated; most 
residents live along the major highways. 
Talkeetna is the largest settlement near the 
VCMD and has a population of 269. 
Cantwell, with 150 residents, is the second 
largest population center near the VCMD. 
The Valdez Creek Mining Company camp 
has a population of about 130 persons when 
the Denali Mine is in operation, and repre- 
sents the largest settlement actually within 
the district. Other relatively significant 
population centers in the VCMD are located 
at Lake Louise, where less than 100 people 
live year round, at Busch Creek, where 3 to 

FIGURE 4. - View up the Susitna River looking towards the Alaska Range, Clearwater Mountains area. 

10 miners work during the summer, and in 
the Valdez Creek drainage above the Valdez 
Creek Mine, where 5 to 20 people work 
placer and lode mines during the summer. 


j Puusset exploration dominates the early 

historical record of exploitation of the 
natural resources in Alaska. However, the 
Russians had little to do with exploration in 
the VCMD except for a Russian American 
Company explorer named _ Rufus 
Serebrenikoff. Serebrenikoff led one of the 
last Russian exploration teams into the 
Alaskan interior in 1847-1848. Penetrating 
the wilderness further than any previous 
explorers, Serebrenikoff’s expedition 
traveled into the Copper River basin, 
possibly reaching the southeastern portion of 
the VCMD. The expedition ended when the 
explorers met their untimely deaths at the 
hands of the Natives. The loss of the 
Serebrenikoff party dampened the 
enthusiasm of the Russian American 
Company for exploration of interior Alaska, 
and was one of the contributing factors to 
the Treaty of Cession in 1867, which 
transferred sovereignty over Alaska to the 
United States. 

After the 1867 treaty, Russian interest in 
Alaska slowly diminished concurrent with an 
increase in interest by the United States. 
The earliest documented U.S. exploration in 
the VCMD was accomplished by W. G. 
Jack, who explored for gold in the upper 
Susitna River headwaters in 1897 (4). Jack 
reportedly discovered gold at a creek called 
"Galina" by the local Natives, but lacking 
excavation equipment, he returned to the 
Cook Inlet area later that year. Word soon 
spread of the gold strike on Galina Creek, 
which was renamed Swollen Creek 

reportedly in honor of the mosquito 
population that thrived there (5). 

The first documented mineral discovery in 
the district occurred on August 15, 1903, 
when a party led by Peter Monahan 
rediscovered placer gold in the gravel 
deposits on Swollen Creek (Monahan is 
given credit by most accounts for the Valdez 
Creek gold discovery, even though Jack 
apparently made the discovery several years 
earlier). Monahan renamed the creek 
Valdez Creek after the town of Valdez (6). 
The Valdez Creek placer gold strike sparked 
an influx of prospectors to the area during 
the succeeding years. The result of that 
small gold rush was the discovery of several 
lode gold deposits, including both the 
Timberline and Black Creek lodes, around 
1906 (6). Figures 5, 6, and 7 show scenes 
of early mining activity on Valdez Creek. 

In 1907, the first significant mineral 
discovery west of Broad Pass was made by 
John Coffee on Bryn Mawr Creek (7). 
Coffee attempted to mine placer gold on the 
creek, but was unsuccessful due to the low 
grade of the deposit. Bryn Mawr Creek 
drains the area around an arsenical gold- 
silver-copper-lead deposit now known as the 
Golden Zone Mine. The deposit was 
discovered in 1912 as a result of interest in 
the gold placers on Bryn Mawr Creek. The 
Golden Zone was developed into a mine 
shortly after its discovery and by 1917, 221 
ft of underground workings had _ been 
completed. The mine went into production 
in 1941 and produced gold, silver, copper, 
and lead during the years 1941 and 1942. 
World War II forced the shutdown of the 
mine in 1942. The latest attempt at 
development, which began at the Golden 
Zone Mine in 1980 and continued through 
1988, involved surface drilling, trenching, 
and underground development work. 

In 1913, a placer gold deposit was 

FIGURE 5. - The original adit on the Tammany 
paleochannel, circa 1915. View of the present 

location of the Denali placer mine (photo courtesy 
of U.S. Geological Survey). 

discovered on Albert Creek, a tributary to 
the Nelchina_ River. The discovery 
stimulated a gold rush into the Nelchina and 
Oshetna River drainages in 1914. Pros- 
pectors found no_ other — significant 
concentrations of gold and most gold seekers 
soon departed the country for more 
promising areas (8-9). 

Lode copper deposits in the Clearwater 
Mountains and the Maclaren River area were 
discovered in 1918. Although several 
copper deposits have undergone significant 
development work, notably the Denali 
Copper prospect, Zackly, and the Kathleen 
Margaret, only the Kathleen Margaret has 

FIGURE 6. - Gold sluicing operation on Valdez 
Creek, circa 1915 (photo courtesy of the U.S. 
Geological Survey). 

recorded very minor production. 

In 1922, a ruby silver prospect was 
discovered on Portage Creek, 3 miles above 
its confluence with the Susitna River (10). 
The prospect was slowly developed over 
many years to the point of production, until 
World War II forced suspension of 
development activity. The workings have 
since caved, and the mill building has 

Coal was discovered in the Costello Creek 
drainage around 1911. The Dunkle Coal 
Mine, located just east of the Golden Zone 
Mine, was eventually developed and 
produced 64,000 tons of coal between 1940 
and 1954. The mine supplied coal to local 
mining operations and to consumers along 
the Alaska Railroad. 

In 1984, placer gold prospecting and 
mining activity on Valdez Creek and its 
tributaries increased with the startup of the 
large-scale open pit Denali Mine operated by 
the Valdez Creek Mining Company 
(VCMC). Placer gold production from the 

Peter Gabby, Steve Iverson, Rick 
Johnson, Andy Leszcykowski, 
Terry Newman, Steve Schmauch, 
and Spencee Willett assisted with 
the field investigations during the 
first year of the study and deserve 
many thanks. Recognition for a 
professional contribution to the 
project also goes to field assistants 
Laurie Dilley, Vic Fisher, Gerald 
Harris, and Dan O’ Haire. 

The author gratefully 
acknowledges the expertise 
contributed to the VCMD project 
by ADGGS geologists Tom 
Bundtzen, Laurel Burns, Ellen 
Harris, Gerald Harris, Jeff Kline, 
Shirly Liss, Rainer Newberry, 
Chris Nye, Gar Pessel, Dick 

FIGURE 7. - Placer mining on Valdez Creek, circa 1920 (photo Reger, Thomas Smith, Diana 

courtesy of the Anchorage Museum of History and Art). 

Denali Mine over the past 5 years has been 
several times greater than the total previous 
production for the entire VCMD. 

Minor lode gold mining occurred on Black 
Creek at the Black Creek Lode and on 
Timberline Creek (tributaries to Valdez 
Creek) in 1984. Development work has 
continued at the Black Creek Lode since 
1984 through 1990. 


lec VCMD study was made possible by 

the effort and expertise contributed by 
many people. Anchorage Field Operations 
Center personnel Steve Fechner, Denise 
Herzog, Mark Meyer, Nathan Rathbun, 
Chris Roe, and Dennis Southworth added 
the benefit of their knowledge and the 
strength of their backs to the project. 
Western Field Operations Center personnel 

Solie, and Milt Wiltse, who 

conducted geologic mapping and 
geochemical sampling in the VCMD and 
assisted with their wide-ranging knowledge 
of geology and mineral deposits. 

The author also wishes to thank local 
geologists, prospectors, and miners, 
including Gerald Anderson, Lyle Beecroft, 
Joe Britton, Frank Celizic, John Dewan, 
Robert Dupere, Bill Elim, Lee Estes, John 
Galey, Jr., John Holmgren, John Jacobsen, 
Stan and Harry Kindblade, Howard and Ed 
Lightfoot, Paul Lindberg, Joe Malatesta, 
Leo Mark Anthony, Claude Morris, Daryl 
Pelke, Henry Peters, A. L. Renshaw, Jr., 
Earl Sikes, Bill Strauss, Jake Tansey, Danny 
Thomas, Kevin Thompson, Bob Titchemal, 
and Angel Vidal for sharing their specialized 
knowledge of the mining history, geology, 
and mineralization associated with the occur- 
rences with which they are familiar. The 
staff of the Valdez Creek Mining Co. 
provided the Bureau access to their operation 
on Valdez Creek. Wallace Toupe of Nerco 

Minerals Inc. conducted a tour of, and 
provided geological information about, the 
Zackly Prospect. Chuck Hawley of Golden 
Zone Developments, Ltd. provided access to 
the Golden Zone Mine. 


everal localities within the VCMD have 

experienced exploration and mineral 
development activity in the recent past. The 
most notable projects are the placer gold 
mining operation at the Denali Mine (fig. 
8), the Denali Copper copper-gold prospect, 
the Su Claims _ gold-copper- 
molybdenum quartz monzonite 
porphyry, the Golden Zone 
arsenical gold-silver-copper-lead 
breccia pipe, the Zackly copper- 
gold-silver skarn, the Kathleen 
Margaret copper-gold lode, the 
Tsusena Creek silver-tin lode 
prospect, the Coal Creek Tin tin- 
silver prospect, the Busch Creek 
gold-PGM placer, and the Tyone 
Creek-Yacko Creek area gold- 
PGM placer occurrences (fig. 9). 


he Valdez Creek area encom- 

passes those properties located 
within the drainage basin of 
Valdez Creek. Historically, the 
area has been and currently is the 
most active locality for mining 
and exploration in the VCMD. 
The area is known for the largest 
gold producer in the VCMD and 
one of the largest placer mines in 
Alaska: the Denali Mine. 
Located in the lower reaches of 

produced 243,908 oz of gold, and has 
moved over 20 million yd? of overburden to 
expose the  gold-rich pay _ gravel. 
Exploration for placer gold at the Denali 
Mine has identified resources of 627,000 oz 
of gold including measured reserves of 
316,000 oz (11). After an approximately 1 
year suspension of operations due to low 
gold prices in 1989, exploration has resumed 
and is planned to continue ahead of the open 
pit mining operation to further define 
reserves and provide data for the control of 
open pit development. The 5-year plan for 
the mine calls for diversion of Valdez Creek 
(which is necessary to continue mining the 

reek. the mine has FIGURE 8. - Denali Mine gold placer open-pit mining operation on 
Valdez Creek, t Valdez Creek, 1989. 


*00" 146 *30’ 
148 *30' 148°00° 147° 30’ Jel als = 
T T 

151°30" Aer fae, 
+ E5108 150 *30 150 ‘00! 149 *30" 149°00' 

*30'T- 63°30" 
“115% |= ) 63°15" 
*00"- 63°00" 

| Senali National 

62° 30’ 

Petersvilleo*, pale 




147° 00’ 

on 151° 30 fs | 
<a fe zl 
isos 150°30 150° 00" Tao 30 149 °00" 148° 30" 148 *00" 147° 30" 

FIGURE 9. - Mineral property location map for selected mineral deposits in the Valdez Creek Mining District, Alaska. 

East Fork Susitna River placer gold occurrence. 
Eureka Glacier lode PGM occurrence. 
Kathleen Margaret lode copper-gold prospect. 
Viking lode copper-gold occurrence. 
Zackly lode copper-gold-silver prospect. 
Gossan lode gold occurrence. 
Mex Claims lode gold occurrence. 
Little Clearwater Creek placer gold prospect. 

Grogg Creek gold placer prospect and Upper 
Valdez Creek gold placer occurrence. 

Eldorado Creek lode PGM occurrence and gold 
placer prospect. 

Gold/Lucky Hill lode gold prospect and Black 
Creek lode gold prospect. 

Denali Copper lode copper prospect. 

White Creek - Lucky Gulch - Rusty Creek gold 
placer mines and prospects. 

Timberline Creek lode gold prospects. 

Denali Mine placer gold mine. 

Windy Creek gold placer prospect. 

Su Claims lode gold prospect. 

Gold Creek East lode gold prospect. 

Peak 5532 lode PGM occurrence. 

Watana Creek placer gold occurrence. 

Devils Canyon lode  gold-copper-zinc-PGM 


Key for figure 9 - names of mineral properties discussed in this report 


Tsusena Creek lode tin-silver prospect. 
Green Spike lode copper-silver occurrence. 
Honolulu Creek placer gold occurrence. 
Treasure Creek lode molybdenum prospect. 
Mint Mine lode silver prospect. 
Honolulu lode tin-silver prospect. 
East Fork Chulitna River placer gold occurrence. 


Colorado Creek area lode gold-silver occurrences 
and prospects. 

Golden Zone Mine. 
Christy Creek Chromite occurrence. 
Ready Cash lode tin-silver prospect. 
Ohio Creek lode tin prospect. 
McCallie Glacier lode gold occurrence. 
Shotgun Creek lode PGM occurrence. 
Partin Creek lode gold occurrence. 
Coal Creek Tin prospect. 


Peters Hills area placer gold mines, prospects, and 

Busch Creek gold-PGM-placer mine. 

Tyone Creek - Yacko Creek area gold-PGM-placer 
mines, prospects, and occurrences. 

deposit) and for full capacity production. 
Figure 8 shows the open-pit mining opera- 
tion at Denali Mine as it was in 1989. 

Other important placer gold producers or 
exploration projects in the area exist on 
White Creek, Lucky Gulch, Eldorado Creek, 
Grogg Creek, Rusty Creek, upper Valdez 
Creek, and Windy Creek (fig. 9). 

The Gold Hill-Lucky Hill area, also 
known as the Rainbow Hill property, is 
located upstream of the Denali Mine and has 
been identified as a possible source for the 
placer gold that exists in the Valdez Creek 
drainage. The property is currently being 
explored for economic lode gold resources. 

Minor lode gold mining occurred at the 
Black Creek Lode on Black Creek near the 
headwaters of Valdez Creek, in 1984. 
Bureau personnel observed development 
work and small scale lode mining there in 
1987 through 1989. The mine has recorded 
production of small quantities of gold. Mine 
operators commenced the development of a 
new adit in 1990. 


T he historical record of the Denali Copper 

prospect includes references to the many 
early prospectors who set foot on the 
deposit, or saw signs of copper mineral- 
ization from the air or nearby mountains 
(12). However, the deposit was not well 
known until 1964 when the occurrence was 
first reported in literature published by the 
State of Alaska, Department of Natural 
Resources (13). Between 1964 and 1971, 
the occurrence was subjected to a concerted 
attempt at development through surface 
trenching, diamond drilling, and an under- 
ground exploration program (12). The 
exploration efforts indicated that the Denali 
Copper prospect is a series of at least six 
stratiform, volcanogenic, massive sulfide 


copper deposits of the Kuroko or Besshi type 
(14). The property has essentially had little 
development work performed since 1971, 
and only maintenance level work is currently 
being conducted. Most of the surface facil- 
ities were destroyed by a large avalanche 
during the winter of 1989. 


he Su Claims overlie a mineralized 

quartz monzonite stock that cuts horn- 
felsed and propylitized siltstone and argillite. 
The prospect is located in the Butte Creek 
region of the Central Talkeetna Mountains. 
The Su Claims have drill holes scattered 
across the property, which were drilled 
during the period between 1975-1990. The 
latest exploration activity on the prospect 
involved a drilling, geophysical, and surface 
geochemical investigation. Drill results 
from one hole show a 10-ft thick mineral- 
ized intercept containing up to 0.39 oz/st 
gold. Trenching has exposed a 230-ft thick 
interval containing 410 ppb gold. 


4 pie Golden Zone Mine (fig. 10), located 

12 air miles southwest of Cantwell, is an 
arsenical  gold-silver-copper-lead-bearing 
intrusive breccia pipe that produced more 
than 1,500 oz of gold, 8,600 oz of silver, 21 
st of copper, and 3,000 Ib of lead during the 
years 1941-1942 (15). World War II forced 
the closure of the mine by Executive order 
in 1942. Exploration over the years 
following the end of the war involved 
sporadic episodes of trenching, geophysics, 
and drilling by both private organizations 
and by the Bureau. During the years 1949- 
1952, the Bureau was involved in drilling 
and metallurgical testing of the ore (16). 
Additional drilling and underground 

FIGURE 10. - Aerial view of the Golden Zone Mine, 

development occurred on the property 
between 1980-1989. 

The development of the Golden Zone to 
its full potential has suffered because the ore 
in the deposit is a complex sulfide with high 
concentrations of arsenic. This combination 
of factors causes very low metal recoveries 
using conventional vat leach and flotation 
milling processes. 


4 pas Zackly copper-gold-silver skarn 

deposit has been subjected to intensive 
exploration between its 1979 discovery and 
1987 (17). The deposit, located in the 
Eastern Alaska Range, was originally located 
aS a copper prospect, however, subsequent 
drilling has shown that there are 
considerable precious metal concentrations in 
the ore. Development and exploration 


activity at the deposit has been minimal over 
the past few years. 


T he Kathleen Margaret prospect is a basalt 
hosted copper-gold quartz vein located 
west of the terminus of the Maclaren 
Glacier. The prospect was discovered in 
1952 (18-19), and underwent development 
work that included trenching, drilling, and 
underground excavation during the years 
1953-1959. Small amounts of copper, gold, 
and silver were recovered from the deposit 
during this period. Exploration (trenching) 
occurred again in 1965, and also in 1988. 
The property is currently idle, and the portal 
to the underground workings has caved. 
The Bureau conducted beneficiation testing 
of the ore in the 1950’s, and reported that 
the ore was readily amenable to standard 
flotation beneficiation methods for copper 
ores (16). 


he Tsusena Creek prospect was 

discovered in 1973 after a reconnaissance 
geological exploration team _ collected 
samples from a tributary to Tsusena Creek 
that contained anomalous silver 
concentrations (20). The occurrence was 
staked by Resource Associates of Alaska in 
1979 when silver prices rose and the mineral 
resource potential of the area became more 
clearly understood. Detailed geologic 
mapping and _ geophysical exploration 
occurred on the property during 1980 and 
1981. Four mineralized areas exhibiting 
suifide-bearing veins and shear zones were 
discovered as a result of the work. The 
Tsusena Creek property is currently idle, 
and Resource Associates have dropped their 
claims on the prospect. 


4p Coal Creek Tin prospect is a tin- 

bearing sheeted greisen vein system 
associated with aplite granite (21). Mineral- 
ization consists of tin-silver-copper-zinc- 
bearing greisen veins. The prospect was 
drilled in 1983, and the results indicate a 5 
million ton deposit grading 0.2% tin (22). 
The prospect is currently idle. 


rior to 1977, small scale placer gold 

mining had occurred intermittently on 
Busch Creek since the early 1900’s. In 
1977, a medium sized mining operation 
began that, when in operation, produced up 
to 1,000 bank cubic yards of pay gravel per 
day (fig. 11). Mine operators recovered a 
total of approximately 150 oz of gold prior 


FIGURE 11.- Mining operation on Busch Creek showing the jig plant gold recovery system. 


to 1989 when the operation ceased mining 
activity. The property is currently idle. 
Placer platinum and gold were first 
documented on Busch Creek by the U.S. 
Geological Survey in 1978 (23). 


P lacer gold was discovered in the Yacko- 

Tyone Creek area around 1914 (8). 
Since that time, there has been considerable, 
but sporadic exploration and mining activity 
in the area. Small scale placer mining has 
taken place on Tyone Creek, Daisy Creek, 
and Yacko Creek resulting in approximately 
10,000 oz of gold production. Both Tyone 
Creek and Yacko Creek currently have 
active mining claims staked over nearly their 
entire length. All mining activity on both 
creeks has recently ceased. 


Tt VCMD lies generally south of the 

east-west trending Denali Fault and is cut 
by the Talkeetna Fault system trending 
northeast-southwest through the center of the 
district (fig. 12). These major structural 
features roughly separate distinct geologic 
regions, or tectonostratigraphic terranes, 
interpreted to have evolved under different 
geologic conditions. To the north, rock 
units north or within splays of the Denali 
Fault represent Paleozoic through earliest 
Mesozoic oceanic sediments of the Dillinger 
Terrane (24), Aurora Peak Terrane (25), and 
North American craton or Yukon Tanana 
Terrane (24). The region immediately south 
of the Denali Fault lies within the Kahiltna 
Terrane (24), and is composed of Jura- 
Cretaceous marine clastic sedimentary rocks 
intruded by upper Mesozoic and Cenozoic 
granitic plutons. Sediments of the Kahiltna 
Terrane are thought to represent a flysch 
basin formed as the land mass south of the 
Talkeetna Fault system, termed the 
Talkeetna Superterrane (26), converged with 
the North American Continent in Mesozoic 
time. Stratigraphy of the Talkeetna 
Superterrane represents several volcanic 
arcs, which range from pre-Permian through 
Jurassic in age; the Talkeetna Superterrane 
includes Wrangellia Terrane (24) to the 
north and Peninsular Terrane (24) to the 
south. Wrangellia and Peninsular Terranes 
may at one time have been discrete land 
masses. Since the accretion of the Talkeetna 
Superterrane to North America and the 
closing of the intervening flysch basin in 
Mesozoic time, Tertiary volcanism and 
shallowly emplaced intrusives have affected 
the region. Other evidence of young 

tectonism in the region is found in the 
displacement of the Denali Fault system, 
where more than 240 miles of right-lateral 
movement is possible (27), mostly from late 
Mesozoic through Cenozoic time, and in the 
continental fluvial deposits of Tertiary age 
found, in some places, perched well above 
present streams. Glacial drift from at least 
five glaciations, ranging in age from pre- 
Illinoian (more than 1.7 million years ago) 
to Holocene (less than 9,500 years ago), cap 
the bedrock geology (28). 


T he mineral deposits that occur within the 

VCMD were described and classified 
into a scheme that resulted from the 
probabilistic mineral assessment of the 
VCMD (29). The classification system is 
based on the geology, standard chemical 
analyses, thin section studies, major/minor 
oxide rock analyses, lead and sulfur isotope 
studies, trace element studies, and 
microprobe analyses of key ore and 
alteration minerals from samples collected at 
the mineral occurrence. Where there was 
insufficient field, petrographic, trace 
element, and/or isotopic data to arrive at a 
definitive classification for a mineral 
occurrence, a mathematical discriminant 
analysis was employed based on_ the 
geochemistry of samples collected from the 
occurrence. Table 1 shows the 14 unique 
types of mineral deposits that were identified 
by the discriminant analysis classification 


Tre VCMD investigation was initiated by 
collecting available historical data 

: By K. H. Clautice, Geologist, Alaska Division of Geological and Geophysical Surveys, Fairbanks, Alaska. 


1502 147° 

Yukon Tanana Terrane 
a sea 


Aurora Peak oe 
Dillinger a 
? ie Terrane ~~. 

Scale, miles 

/ Kahiltna Terrane 

ae? El, 
5 O\C Se eae —Ulg o. { 
eg 5 on We 
a Pe aety Oo 
~ iA & as 
Sy a i % Superterrane ( 
on ee : Ne x 
/ ‘ o& 

Ne | \ i = 
\ Ve oe 
wees, LEGEND \ aS 
. ? 
Talkeetna —— = Fault, dashed where \ a 
inferred iS S 7s 
O Village or town ‘ < 

FIGURE 12. - Generalized geologic terrane map for the Valdez Creek Mining District, Alaska. 



Deposit type 

Plutonic related vein and 
re lacement gold deposits. 

in-silver-base metal polymetalli 

Tin greisen deposits. 

Porphyry copper + gold deposits. 

Kuroko type volcanogenic 
massive sulfide deposits. 

Carlin-type gold deposits. 

Basalt-associated, sediment-hosted 
copper deposits. 

- Podiform chromite deposits. 

Mafic-ultramafic-hosted platinum- 
group-metal sulfide deposits. 

TABLE 1. - 

s Polymetallie veins patially. associated 

- platinum-grou ca | 


Vein and replacement deposits are spatially associated with granitic rocks. 
features arsenopyrite, Byte, p rrhotite, and UL, 

Ore mineralogy 

ith = tops of a evolved "tin granites". Ore 

Stockwork and disseminated vein aggregate ores associated with the tops of highly evolved 
"tin granites". Ore mineralogy features cassiterite, stannite, arsenopyrite, sphalerite, galena, 
pyrite, and chalcopyrite. 

Deposits are hosted above, and/or in the tops of granitic bodies that exhibit porphyry 

textures. Some deposits are associated with porphyry dikes. Ore mineralogy includes 

yrite chalcopynite, bomite, ae magnetite. 

at: exhibit -porhyey 
and scheelite. sagas ee 

Deposits are hosted at the interface region between submarine volcanic and sedimentary 
rocks. Ore mineralogy includes pyrite, pyrrhotite, sphalerite, chalcopyrite, galena, and 

Carlin-type deposits occur in silty to sandy thin-bedded carbonaceous siltstone or carbonate 
rock. High-angle faults have been identified as conduits for hydrothermal fluids. 
Intermediate composition plutonic rocks are spatially associated and may represent a fluid 
source. Ore mineralogy includes native gold, pyrite, cinnabar, stibnite, realgar, orpiment, 
and scheelite. 

Deposits occur in association with copper-rich, rift-related basalt. Deposits are thought to 
form during low-grade metamorphism. Most occurrences are hosted in overlying copper- 
bearing sedimentary rocks. Ore mineralogy includes chalcocite or pyrite and chalcopyrite, 
depending on the type of host HS 

Ore mineralogy includes chromite, magnetite, 
f may also” be present. 

Magmatic sulfide deposits are associated with mafic-ultramafic sills and dikes. Ore 
mineralogy includes pyrrhotite, pentlandite, chalcopyrite, and nickel, platinum and palladium 
sulfide minerals. 

MD, pneet deposits ¢ can ¢ cc 

Ore mineralogy. includes native gold and” 

VCMD deposit types and descriptions. 


concerning the exploration and mining 
history, geology, and mineral occurrences 
associated with the district. This 
information was organized into a data base 
that was used throughout the project. 
Through the use of the data base, Bureau 
personnel were able to locate and field check 
the existence of reported mineral 

Field work performed by the Bureau 
encompassed district-wide reconnaissance 
geochemical rock and placer sampling and 
the detailed examination of 176 of the 218 
previously known mineral occurrences in the 
district. Of the 42 occurrences not visited, 
13 were located inside Denali National Park 
and Preserve, 11 were located but could not 
be investigated safely due to rugged terrain, 
and 18 could not be located on the ground. 
The Bureau collected and analyzed 1,632 
rock and 781 placer samples, and had 7 bulk 
samples tested for beneficiation 

Bureau field personnel were 
responsible for discovering 19 
previously unreported mineral 

Bureau personnel have written 8 of the 24 
documents that have been published as a 
result of the VCMD investigation. Table 2 
summarizes the names of these documents. 
Included is a comprehensive compilation of 
the geochemical sampling results (32), and 
a detailed discussion of the Bureau’s 
investigation of each mineral occurrence, 
prospect, mine, and previously unreported 
occurrence in the district (33). 

The ADGGS conducted geologic mapping 
and geochemical sampling of selected areas 
in the VCMD and produced several new 
geologic and geochemical reports concerning 
portions of the mining district, including the 
first-ever published geologic map of the 
entire district (28, 37-49). The Bureau and 
the ADGGS participated jointly in 
conducting a probabilistic mineral resource 
and economic assessment of the mining 
district in 1990 (29). 


occurrences within the VCMD 
during the course of the 
investigation. Reconnaissance 
placer sampling resulted in the 
identification of 10 previously 
unreported gold placer 
occurrences, some of which 
contain subsidiary placer platinum 
group metals (PGM) or tin, or 
both. Reconnaissance lode 
sampling resulted in the 
identification of 2 gold-silver 
occurrences, 3 PGM occurrences 
that contain subsidiary chromium, 
nickel and/or cobalt, 3 copper 
occurrences that contain 
subsidiary molybdenum or zinc, 
and 1 zinc occurrence. 

. Results of 1988 Bureau of} Mines 
Valdez Creek Mining District, Alaska GD 

VCMD investigation. 

Results of 1987 Bureau of Mines Investigations in the 
Valdez eid Mining District, Me Gd 

Geochemical Sampling Results From Bureau of Mines 
Investigations in the Valdez Creek Mining District, 

ae GD 

‘District, South- Central Alaska (Final Report) G3) 

Industrial Minerals of the Valdez Creek Mining 

District, Alaska gets) 

The Feasibility of Mining in the Valdez Creek Mining 
District, Alaska (36) 


es Investigations in the 

i we Pou. best ee ee 
Creek Mining District, Alaska 

- Publications by Bureau authors resulting from the 


Th Bureau collected two basic types of 
samples: (1) rock samples, and (2) placer 
samples. Rock samples consisted of fresh, 
altered, or mineralized material and were 
collected from outcrop, rubble crop, 
underground workings, or float. Placer 
samples were collected from river bars, 
flood plains, alluvial fans, colluvial fans, or 
alluvial benches. Two basic types of 
procedures were employed when collecting 
either rock or placer samples: (1) 
reconnaissance sampling, and (2) 
sampling previously known 
mineral occurrences. Recon- 
naissance sampling procedures 
involved collection of placer or 
rock samples, or both, from those 
regions in the VCMD where little 
or no_ historical information 
existed about mineral occurrences. 
Sampling previously known 
mineral occurrences involved 
geologic mapping of _ the 
occurrences and the collection of 
rock or placer samples, or both, 
depending on the type of mineral 
occurrence. A complete compila- 
tion of results of the geochemical 
analysis of samples collected by 
the Bureau in the VCMD is 
available in an OFR (32). 
Bureau personnel also collected 
7 bulk mineralogical samples from 
select mineral occurrences in the 
district. These samples were 
analyzed at the Bureau of Mines 
Salt Lake Research Center in Salt 
Lake City, Utah. Results of the 
analysis of the bulk mineralogical 
samples are published in the final 
report (33). 


he Clarence Lake Upland is a sub- 
physiographic province within and along 
the eastern edge of the Talkeetna Mountains 
physiographic province (fig. 13). Within the 
Clarence Lake Upland region, there are 
several significant gold- and PGM-placer 
deposits in the Tyone Creek-Yacko Creek 
area, and on Busch Creek (fig. 9). 
The Bureau conducted _ site-specific 
evaluations of the Tyone Creek- Yacko Creek 
area to investigate the occurrence of gold 

FIGURE 13. - Bureau geologist collecting a sample near the head- 

waters of the Black River, Talkeetna Mountains physiographic 


and PGM in the placers (35). The 
investigation focused on sampling the 
Jurassic and Tertiary conglomerate rock 
units found throughout the area to test the 
theory that these rocks are the source of 
precious metals in the local placer 
occurrences. Bureau stream placer sampling 
in the Tyone Creek-Yacko Creek area 
recovered as much as 0.0212 oz/yd* gold. 
Samples that contained the highest placer 
gold grades were collected from mining cuts 
on Upper Red Fox Creek, a tributary to 
Tyone Creek. PGM grains existed in 
samples collected from several creeks in the 
area, however, the quantity recovered was 
too small to estimate a PGM ore grade. 
Stream drainages that contain PGM- and 
gold-bearing gravel correlate well with 
drainages that have eroded Jurassic and 
Tertiary conglomerate rock units. 

Samples collected from the Jurassic 
conglomerate rock unit in the Tyone Creek- 
Yacko Creek area contained as much as 
0.0001 oz/yd? gold, but contained no visible 
PGM. Trace concentrations of PGM were 
detected in the analysis of the heavy mineral 
concentrate portion of the samples. 

The Tyone Creek-Yacko Creek area 
Tertiary conglomerate rock unit generally 
contained more gold and PGM than its 
Jurassic counterpart. Gold was recovered in 
quantities as high as 0.0027 oz/yd* and 
platinum grains were visible in some 
samples. Analysis of the heavy mineral 
portion of the samples resulted in the 
detection of as much as 280 ppb platinum 
and 6 ppb palladium. 

The Bureau investigated the gold-PGM 
placer deposit at Busch Creek in 1987 and 
1988 and confirmed the existence of the 
reported placer platinum (30-31). Samples 
collected at the Busch Creek gold-PGM 
placer mine contained as much as 0.012 
oz/yd> gold. Placer sample concentrates 


contained as much as 120 ppb palladium and 
1,060 ppb platinum. The Bureau 
investigation also noted that the deposit 
contains abundant amounts of magnetite. 
The large amounts of magnetite impeded the 
efficiency of both the Bureau’s sampling 
equipment and the gold recovery system 
employed by the mine operators by over- 
loading concentrate collection points. The 
Bureau’s sampling procedure was easily 
modified to account for the large quantity of 
magnetite. However, the mining operation 
suffered because of the difficulty experi- 
enced in extracting small particle size gold 
from the large volumes of concentrate that 
were recovered from the deposit. 

In the Granite Creek headwaters, the 
Bureau investigated the occurrence of 
hydrothermal mineralization that occurs 
along a narrow, steeply dipping gouge zone 
at the fault contact between intrusive and 
volcanic rocks. Samples collected from the 
3.5 ft wide by 350 ft long zone contained up 
to 0.87% zinc and 0.87% copper. Select 
pieces of float contained up to 1.5 oz/st 
silver, 5.8% copper and 2.4% zinc. 


Th Peters Hills area is located in the 

western most region of the VCMD, 
south of Mt. McKinley and west of 
Talkeetna (fig. 9). The Bureau collected 
placer samples from creeks and from 
conglomerate bedrock outcrops to evaluate 
the gold-PGM-placer resources and to 
investigate the reportedly auriferous Sterling 
Formation conglomerate unit that exists 
throughout the area (35). Samples collected 
from the alluvial gravel in the Peters Hills 
area contained as much as 0.014 oz/yd° 
gold. The highest grade placer gold was 
recovered from samples collected from small 
areas in the creeks where mining had not 

taken place. Visible PGM was not 
recovered from any of the samples collected 
in the Peters Hills area. PGM was detected 
however, in some sample concentrates at 
levels up to 800 ppb platinum. In 1919, 
platinum grains were reportedly observed in 
samples collected from two creeks in the 
area, namely Canyon Creek and Poorman 
Creek (50). 

Samples collected from the Sterling 
Formation contained as much as 0.007 
oz/yd’ gold. The Bureau has concluded that 
the Sterling Formation is clearly a source of 
the placer gold in the local drainages, and 
has inferred that there are 21,000,000 yd? of 
subeconomic gold-bearing conglomerate in 
the area (35). 


T he southern portion of the Central Alaska 
Range physiographic province 
incorporates the northwest third of the 
VCMD, and is one of the most geologically 
diverse and mineralogically significant areas 
in the district. The area encompasses the 
Chulitna trend (51), which has a strong 
northeasterly trending grain demonstrated by 
the orientation of sedimentary rock layers, 
faults, and elongated intrusive bodies. 
Sedimentary rock units in the area include 
argillite, greywacke, red beds, limestone, 
and chert. Portions of the sedimentary rock 
package are interlayered with volcanic rocks. 
The sedimentary rocks have been intruded in 
many areas by plutonic rocks ranging in 
composition from ultramafic to felsic (51). 
A total of 46 mineral occurrences are known 
in the Central Alaska Range area (fig. 9). 
Epigenetic mineral occurrences associated 
mainly with plutonic rocks are found 
throughout the entire area. The mineral 
occurrences in the Colorado Creek and the 
Long Creek localities have been shown to be 


associated with small diorite porphyry stocks 
or small quartz porphyry plugs, and are 
known for vein, breccia, stockwork, and 
disseminated deposits that can contain gold, 
or copper and silver in addition to zinc, 
molybdenum, tin, cadmium, or bismuth 
(51). The mineralized areas of the Colorado 
Creek locality were not evaluated by the 
Bureau during the VCMD investigation 
because of access restrictions into Denali 
National Park and Preserve. Occurrences of 
note in the Long Creek vicinity are the 
Golden Zone arsenical gold-silver-copper- 
lead bearing breccia pipe deposit, the 
Lookout Mountain silver-lead-zinc quartz 
porphyry, and the Copper King massive 
sulfide copper-silver replacement deposit. 
The Golden Zone was not evaluated in great 
detail during the VCMD investigation 
because of the large volume of previously 
written information that exists about the 
deposit. Several samples, however, were 
collected from rock faces exposed during 
development work that took place in 1988. 
The highest grade samples contained greater 
than 0.29 oz/st gold, and as much as 1.67 
oz/st silver, 0.21% copper, 0.04% lead, and 
0.01% zinc. 

Cyanide amenability tests were conducted 
by the Bureau’s Salt Lake Research Center 
on a bulk sample of ore from the Golden 
Zone Mine. Test results show that 22% of 
the gold is encapsulated in particles smaller 
than -325 mesh, indicating that special 
techniques will have to be employed to 
liberate the gold. 

Mining feasibility studies have been 
conducted for a "generic" deposit modeled 
after the Golden Zone deposit. The 
feasibility studies have shown that the 
"generic" deposit is sub-economic due 
mainly to the difficulty in recovering metals 
from refractory ore. The mining operation 
model that was applied to the deposit model 


OW x 

FIGURE 14. - Bureau geologist at the dis 

exceeded a 15% rate of return when the 
value of the metal recovered from the ore 
exceeded $262/st of ore (36, 52). 

A tin-silver-base metal polymetallic vein 
occurrence known as the Ready Cash, and a 
tin greisen known as the Ohio Creek Tin 
occurrence are mineral deposits of signifi- 
cance in the Ohio Creek drainage. The 
Ready Cash is a system of sheeted sulfide 
veins as wide as 9 ft and of undetermined 
length. Bureau samples contained concen- 
trations as high as 0.205 oz/st gold, 54.9 
oz/st silver, 0.39% tin, 1.8% copper, 4.11% 
lead, and 9.19% zinc. The Ohio Creek Tin 
occurrence was not visited by the Bureau 
during this study because of access 
restrictions into Denali National Park and 
Preserve, however, the Bureau has 
previously investigated the occurrence (53). 

The Partin Creek polymetallic sulfide vein 

covery outcrop of the McCallie Glacier occurrence. 


occurrence is associated with plutonic rocks, 
and is known mainly as a gold prospect. 
The Bureau collected samples at the prospect 
that contained as much as 1.602 oz/st gold, 
21.9 oz/st silver, and 1.7% copper. 

A discovery made by the Bureau known as 
the McCallie Glacier occurrence (fig. 14) is 
located at the head of McCallie Creek. The 
occurrence consists of disseminated sulfides 
and stockwork veinlets hosted in silicified 
metavolcanic rocks. The area affected by 
sulfide mineralization is as much as 100 ft 
wide, and of undetermined length. Bureau 
samples collected from the occurrence 
contained as much as 0.878 oz/st gold, 4.41 
oz/st silver, 1.79% lead, 1.2% zinc, and 
4.03% antimony. 

Magmatic mineral occurrences associated 
with the ultramafic and mafic rocks in the 
Central Alaska Range exist in a northeasterly 

FIGURE 15. - Bureau geologist examining the ultramafic occurrence in the Butte Creek drainage. 

trending belt that lies on the outer flanks of 
the southern edge of the central Alaska 
Range. The occurrences consist of small 
pods of sulfide minerals intimately 
associated with serpentenites. Mineralization 
can include chromite- and nickel-bearing 
minerals as well as copper, arsenic, gold, 
and trace amounts of platinum. Bureau 
samples collected from the Shotgun Creek 
Lode contained the highest levels of copper 
(4.79%), nickel (2,178 ppm), platinum (30 
ppb), and palladium (16 ppb) that were 
detected in magmatic mineral occurrences 
associated with mafic and ultramafic rocks in 
the area. The Christy Creek Chromite 
occurrence located at the head of Christy 
Creek contained ultramafic rocks with 
chromium concentrations exceeding 1.0%. 



ee VCMD includes within its boundary, 
the northern half of the Talkeetna 
Mountain physiographic province. Mineral 
occurrences of significance in this area 
include the PGM-chromium-nickel-copper 
ultramafic magmatic-sulfide occurrence in 
the Butte Creek drainage (fig. 15), the Su 
Claims gold-molybdenum-copper porphyry, 
the Gold Creek East gold-silver occurrence, 
and the Devils Canyon occurrence (fig. 9). 
The occurrence known as Peak 5532 was 
discovered by the Bureau and exists in a belt 
of ultramafic rocks that trend for 7.5 miles 
in a northeasterly direction through the 
mountains south of Butte Creek. Samples 
collected at the Peak 5532 occurrence 

contained as much as 0.41% chromium, 
0.15% copper, 0.11% nickel, 28 ppb 
palladium, and 140 ppb platinum. 

Porphyry mineralization at the Su Claims 
prospect is associated with a quartz 
monzonite stock that has intruded and altered 
siltstone and sandstone. Alteration products 
include hornfelsed and _ propylitized 
sedimentary host rocks. The deposit appears 
to be concentrically zoned, and _ has 
associated gold-bearing veins and shear 
zones (33). Concentrations as high as 265 
ppb gold, 282 ppm copper, and 60 ppm 
molybdenum were detected in samples 
collected from the property. 

The Gold Creek East lode gold occurrence 
exists 2.5 miles east of the Su Claims. 
Samples collected from a silicified fault zone 
contained as much as 0.25 oz/st gold, 
0.57% copper, and 71 ppm molybdenum. 

The Bureau collected 5 placer samples 
from stream gravel and 3 rock samples from 
outcrop or float in a series of tributaries that 
flow north into the Susitna River at Devils 
Canyon. Three placer samples were 
anomalous in silver, arsenic, gold, platinum, 
and/or tin, and 2 rock samples were 
anomalous in silver, arsenic, gold, copper, 
molybdenum, lead, and/or zinc. Table 3 
summarizes the highest magnitude anomalies 
with respect to the sample type. 

Bureau samples collected from two 
locations in the Watana Creek drainage were 
found to contain anomalous levels of placer 
gold. Placer gold values as high as 
0.002 oz/yd? were recovered in a sample 
collected at the mouth of Delusion Creek, a 
tributary to Watana Creek. The lower 
portion of Delusion Creek drains through a 
Tertiary conglomerate rock unit (42), which 
could represent the lode source for the 
placer gold. Values as high as 0.002 oz/yd? 
were recovered in a sample collected several 
miles upstream on Watana Creek where the 
creek also erodes through the same Tertiary 
conglomerate unit. 


Tt" Chulitna Mountains are a part of the 

northern Talkeetna Mountains and 
comprise an area in the VCMD where few 
known mineral occurrences exist. 
Consequently, the Bureau spent a significant 
amount of time collecting reconnaissance 
samples from the area in an effort to locate 
new, and evaluate the few known 
occurrences. As a result of the Bureau’s 
reconnaissance effort, several new 
occurrences were discovered. The new 
occurrences of significance are the Green 
Spike copper-zinc-silver-tin-molybdenum 

Anomalous geochemical analyses 

Type Ag As Au Au Cu Mo Pb Pt Sn 
(ppm) | (ppm) (ppb) oz/yd° (ppm) (ppm) (ppm) (ppb) (ppm) 

rer | m [ve | wo [om [wm [wa | wn | oo | om 
5 180 N/A N/A 1 264 N/A N/ 


TABLE 3. - Summary of results from samples collected at the Devils Canyon occurrence. Note. - Only the 
highest anomalous values are listed. N/A = not anomalous. 

granite porphyry, the Honolulu Creek gold 
placer, and the East Fork Chulitna River 
gold placer (fig. 9). 

The Green Spike occurrence is a granite 
porphyry that outcrops prominently in the 
headwaters of the East Fork Chulitna River. 
Samples collected there contained as much 
as 0.48% copper, 819 ppm zinc, 0.39 oz/st 
silver, 13 ppm tin, and 25 ppm 

The Bureau collected placer samples over 
the entire length of Honolulu Creek, and 
discovered several areas that contain high 
concentrations of placer gold. The highest 
grade sample contained 0.010 oz/yd’ gold 
and was collected near the headwaters. 

Several placer samples collected from the 
lower portion of the East Fork Chulitna 
River contained anomalous gold. The 
highest grade sample contained 0.003 oz/yd? 

Previously known mineral occurrences of 
significance in the Chulitna Mountains are 
the Tsusena Creek lode tin-silver prospect, 
the Honolulu lode tin silver prospect, the 
Mint Mine lode silver prospect, and the 
Treasure Creek lode molybdenum prospect 
(fig. 9). 

The Bureau visited the Tsusena Creek tin- 
silver vein and mineralized shear-zone 
prospect and collected 48 samples from the 
occurrence. The highest grade samples 
contained as much as 26.5 oz/st silver, 
0.55% tin, 1.21% lead, 5.45% zinc, and 
0.66% copper. 

The Honolulu prospect exists in a tributary 
drainage to Honolulu Creek. Outcrops in 
the tributary valley bottom exhibit highly 
altered granitic rock and sulfide-rich quartz 
veinlets. One sample collected across a 60 
ft exposure of altered granite contained 1.09 
oz/st silver, 0.032 oz/st gold, 1.55% 

copper, and 250 ppm tin. The highest grade 
samples contained as much as 141.7 oz/st 
silver, 0.05 oz/st gold, 6.33% lead, 6.04% 
zinc, 1.55% copper, and 795 ppm tin. 

The main mineralized zone at the Mint 
Mine consists of a quartz-filled shear zone 
exhibiting minor sulfides and intense 
footwall alteration. The highest grade 
samples collected from the vein contained as 
much as 56.6 oz/st silver and 0.09 oz/st 
gold. One sample averaged 28.0 oz/st silver 
across 3 ft of vein exposure. 

The Treasure Creek molybdenum prospect 
exists near the Mint Mine, approximately 2 
miles upstream. The prospect consists of 
highly altered granite porphyry stock 
containing massive molybdenite in at least 
one exposed vein. The highest grade 
samples collected from the occurrence 
contained greater than 1.0% molybdenum 
and as much as 1.7 oz/st silver, 0.02 oz/st 
gold, 2.56% zinc, 0.42% tungsten, and 17 
ppm tin. 


he Clearwater Mountains area extends 

northeasterly from the Susitna River at 
the Valdez Creek confluence to the 
headwaters of the West Fork Maclaren River 
(figs. 9 and 16). The area contains many 
significant types of mineral occurrences. 
The area is also known for the Denali Mine, 
which is in the Valdez Creek drainage and is 
the largest gold producer in the VCMD. 
The Valdez Creek drainage also contains the 
largest known gold resources in the VCMD. 
The majority of production in Valdez Creek 
comes from buried interglacial bedrock 
channels in the lower portion of Valdez 
Creek. Sampling by both private industry 
and the Bureau indicates potential for placer 

; By Joseph M. Kurtak, Physical Scientist, Alaska Field Operations Center, Anchorage, Alaska. 


FIGURE 16. - View up the Maclaren River valley from the Denali highway at the Maclaren River crossing. 

gold deposits in ice-marginal and medial 
moraine deposits in the upper part of the 
Valdez Creek drainage. Placer samples 
collected on benches along Valdez Creek 
upstream from White Creek contained as 
much as 0.017 oz/yd? gold. Placer samples 
from bench gravel along White Creek 
contained as much as 0.007 oz/yd? gold and 
in Grogg Creek up to 0.004 oz/yd’ gold. 
Drilling by private industry along lower 
White Creek indicates potential for deeply 
buried placer deposits. 

In the Gold Hill-Lucky Hill vicinity 
between upper Valdez Creek and White 
Creek, placer samples collected from soils 
and colluvium contained as much as 0.03 
oz/yd> gold. A soil geochemical survey 
done on Gold Hill and Lucky Hill in 1988 
by private industry led to the discovery of 
lode gold in 1989. Subsequent drilling has 


intersected zones of quartz-carbonate veining 
as wide as 15 ft containing as much as 0.811 
oz/st gold. Potential exists in the area for 
further discoveries of quartz-carbonate vein 
stockwork-type mineralization. 

A contact between altered quartz diorite 
and argillite can be traced for 1 mile across 
Timberline Creek, a tributary to Valdez 
Creek. Samples of the diorite contain as 
much as 410 ppb gold, and quartz breccia 
float found nearby contains as much as 0.13 
oz/st gold. Potential exists in the area for 
vein and stockwork-type mineralization 
similar to that found in the Lucky Hill-Gold 
Hill area. Some shallow drilling has been 
done along the contact, but the results were 

In the Eldorado Creek drainage, a 
tributary to upper Valdez Creek, float 
samples of alkali gabbro contained as much 

as 45 ppb platinum and 92 ppb palladium. 
An alkali gabbro body at the head of the 
drainage is probably the source of the float. 

The Bureau collected rock samples and a 
bulk metallurgical sample from the Denali 
Copper prospect, at the head of Windy 
Creek. The highest grade samples contained 
as much as 0.39 oz/st silver, 0.11 oz/st 
gold, 12.5% copper, and 94 ppm 
molybdenum. Metallurgical testing has 
shown that approximately 50% of the metals 
in the ore can be recovered using standard 
sulfide flotation techniques. The low metal 
recovery rates experienced during milling of 
the ore is the most detrimental variable 
affecting the likelihood for development and 
subsequent mining of the deposit. A mining 
feasibility study conducted for a "generic" 
deposit modeled after the Denali Copper 
prospect has shown that a mining operation 
would be subeconomic due to (1) the metal 
recovery problems associated with the large 
quantity of sulfides in the ore, (2) the actual 
grade of the modeled deposit, and (3) the 
requirements for ore extraction given the 
deposit structure and known engineering 
characteristics. The best case mining 
scenario that was applied to the deposit 
model yielded a 15% rate of return when the 
value of the metal recovered from the ore 
exceeded $65/st of ore (36). 

At the Mex Claims and the Gossan 
occurrence near the headwaters of Little 
Clearwater Creek, polymetallic veins are 
anomalous in antimony, gold, tungsten, 
mercury, and arsenic. Metasediments in the 
area are also anomalous in mercury, arsenic, 
silver, and gold. Samples of altered 
metasediments contain as much as 0.79 oz/st 
silver and 50 ppb gold. The area has 
potential for low-grade silver and gold 
deposits, but detailed geochemical sampling 
and drilling are necessary to determine if 
such deposits exist. Placer samples collected 


along lower Little Clearwater Creek 
contained as much as 0.015 oz/yd? gold and 
were anomalous in tungsten and mercury. 


he Eastern Alaska Range physiographic 

province encompasses the northeastern 
portion of the VCMD. The areal extent of 
the VCMD within the province includes the 
West Fork and the Middle Fork of the 
Maclaren River, the Susitna Glaciers and 
contributing icefields, and the Maclaren 
Glacier and contributing icefields. Mineral 
occurrences of significance within this 
region are the Zackly copper-gold-silver 
skarn, the Kathleen Margaret basalt hosted 
copper-gold vein, the Viking basalt hosted 
copper-gold-magnetite veins, the Eureka 
Glacier ultramafic associated PGM-chrome- 
nickel occurrence, and the East Fork Susitna 
River placer gold occurrence (fig. 9). 

The Bureau performed a_ minimal 
investigation at the Zackly copper-gold-silver 
skarn mainly because of the existence of 
previous data and the record of extensive 
exploration performed by private industry on 
the prospect. Bureau work on the prospect 
included the collection of a bulk sample for 
metallurgical testing purposes, and the col- 
lection of several samples from a high grade 
zone of mineralization. The highest grade 
samples contained as much as 0.18 oz/st 
gold, 2.44 oz/st silver, and 7.1% copper. 

The metallurgical test evaluated the 
amenability of the ore to standard gold- 
copper-sulfide ore processing. Fine-grain 
gold and complex sulfide structures caused 
recovery rates below 50% for gold and 
copper under test conditions. Test results 
show that metal recoveries increase when the 
ore is ground to sizes smaller than -325 
mesh. (33). 

A mining feasibility study conducted by 

the Bureau for a_ geologically and 
metallurgically analogous "generic" deposit 
has shown that the "generic" deposit is 
currently subeconomic, primarily due to the 
relatively low amounts of metal that can be 
recovered from the ore, and secondarily due 
to the type of mining methods that must be 
employed to extract the ore. The mining 
scenario that was applied to the "generic" 
deposit model yielded a 15% rate of return 
when the value of the metal recovered from 
the ore exceeded $258/st of ore (36). 

The Kathleen Margaret prospect consists 
of a sulfide-rich quartz vein that is exposed 
on the surface and in underground workings. 
The Bureau collected samples from several 
trenches, and from a 10-ft-wide exposure of 
sulfide-rich quartz vein in the main zone of 
mineralization. The highest grade samples 
contained as much as 2.07 oz/st silver, 
0.119 oz/st gold, 38.4% copper, 0.43% 
antimony, and 0.19% zinc. 

A short distance south from the Kathleen 
Margaret is the Viking copper-gold- 
magnetite vein occurrence. Mineralization 
occurs in lenticular veins oriented in echelon 
across an undetermined thickness of host 
metabasalt rocks. Bureau samples collected 
from the veins contained as much as 14.4 
oz/st silver, 1.258 oz/st gold, 3.17% 
copper, and 0.01% gallium. 

On the far eastern boundary of the VCMD 
is the Eureka Glacier ultramafic associated 
PGM-chrome-nickel occurrence. The 
occurrence mainly consists of narrow zones 
of intermittently exposed rubblecrop that 
extends across several hundred acres of high 
mountainous _ terrain. Bureau samples 
collected from the occurrence contained as 
much as 0.38% chromium, 0.36% nickel, 
0.011 oz/st palladium, and 0.017 oz/st 

Bureau geologists discovered gold-placer 
occurrences in two adjacent tributaries to the 
north side of the East Fork Susitna River. 
The highest grade samples that were 
collected from the occurrence contained as 
much as 0.01 oz/yd*® gold and 58 ppm 
cobalt. The cobalt sulfide mineral linnaeite 
was identified in one sample. 


| Beeeen: within the VCMD are potential 

economic sources of argillite, limestone, 
intrusive rock, basalt, perlite, zeolite, and 
gravel. At least six potentially economic 
limestone deposits are known to exist within 
the VCMD. Adjacent to the Parks Highway 
and marginal to the VCMD, a limestone 
deposit is currently being mined as a source 
of agricultural lime. Deposits of argillite, 
granitic rock, and basalt of commercial 
grade are known to exist within the VCMD, 
and some of these were exploited during the 
construction of the Alaska Railroad and the 
Parks and Denali Highways. 

A perlite occurrence near Yacko Creek 
was evaluated by the Bureau in 1989. 
Analyses have shown that the occurrence is 
not of commercial grade (34). 

Large zeolite deposits of potentially 
commercial grade exist in the Talkeetna 
Formation, which is located in the Horn 
Mountains of the upper Matanuska Valley. 
Commercial extraction of the resource in the 
near term is unlikely due to the remote 
location of the occurrences and the distance 
from the area to potential markets. 

There are large deposits of glacially- 
derived gravel within the VCMD. High silt 
content and distance to construction sites 
render much of this material subeconomic. 

® By D. D. Southworth, Physical Science Technician, Alaska Field Operations Center, Anchorage, Alaska. 


M ining feasibility investigations were 
conducted for eight mineral deposit 
models (Table 4) (36). The models were 
based on real and hypothetical deposits that 
occur in the VCMD. Sixty-six mine models 
were developed for application to the 
mineral deposit models and capital and 
operating costs were calculated for each 
mine model. From the cost data for each 
mine model, a capital investment schedule 
(CIS) was developed to show the timing of 
capital investment into the mining model. A 
cash flow analysis was performed for the 
CIS data for each mine model, and the 
discounted cash flow rate of return on 
investment (DCFROR) versus the recover- 
able metal value’ (RMV) distribution was 
The goal of the feasibility study was to 
determine the monetary value per metric ton 
of minable ore that would cause the 

Deposit model 

Metamorphic gold vein ee 
: Copper-gold skarn deposits 

Plutonic related vein and replacement gold He SEIS 

Basalt hosted copper deposits So ee 
Carlin- -type gold deposits 
‘Plutonic : related tin greisen deposits _ 

SiG silver, Couper, breccia pipe deposit | 

simulated cash flow of each of the mine 
models to achieve certain predefined rates of 
return for the invested capital. 

The result of the cash flow analysis is a 
graphical representation of the economic 
performance of the mine model, expressed 
in terms of expected DCFROR. All of the 
results are estimated to be within + 25% of 
real costs. 

The cash flow analysis for each mine 
model covered a range of RMV’s that 
caused the DCFROR result of the cash flow 
analysis to exceed an arbitrary 15% 
DCFROR economic threshold. The 15% 
DCFROR threshold was chosen to represent 
the level of return on investment that would 
be considered an acceptable minimum for 
economic viability of a mine model. 

Given the "generic" nature of the mining 
feasibility study, and the number of vari- 
ables involved in performing an economic 
analysis for a mineral property, it is difficult 
to arrive at any concrete summation of what 
is or is not feasible. Factors that behave as 

Mine model(s) 
(extraction method depends 
upon mining rate) 
Overhand or cut-and-fill 
Overhand, cut-and-fill, or longhole-sublevel 
Shrinkage, overhand, or longhole-sublevel 
Longhole-sublevel or Vertical crater retreat — 
Open pit 
Open. pit. 
Open pit and cut-and-fill 

Open pit 

TABLE 4. - Mineral deposit models and associated mine models used in the mining feasibility study of the Valdez 

Creek Mining District, Alaska. 

1 The recoverable metal value is the gross monetary value of the metal recovered from the mineral deposit, less 

shipping costs, and less smelter royalty. 

dominant functions in the equation for 
economic viability are ore grade, deposit 
size, deposit structure, and ore mineralogy. 
A mineral deposit becomes more economi- 
cally viable when ore grade is high, deposit 
size is large, deposit structure is favorable 
for the application of low cost ore extraction 
techniques, and the ore is amenable to 
current metals extraction technology. 
Generally and from the engineering point of 
view, small, high-grade, easily accessible 
vein-type lode gold deposits are likely to be 
economic at the present time, based on the 
mining feasibility study. Large tonnage, 
low grade, sediment-hosted disseminated 
precious metal deposits are also likely to be 
economic if open pit mining methods can be 
used for mining, and if the ore yields to 
current milling technology. It may be 
evident from this discussion that there are 
innumerable variables that effect the 
economic viability of an ore deposit. Given 
the proper qualifiers and conditions, it is 
possible to describe nearly any mining 
scenario that could be economic. 

A likely application of the mining feasi- 
bility study is to compare the results of the 
economic analysis of a model to a real min- 
eral prospect that possesses geological and 
structural characteristics that are similar to 
the model. The results of the mining feasi- 
bility analysis of these mine models could be 
used in a preliminary manner to evaluate the 
mining potential of real mineral deposits that 
are similar to the deposit models. 


ineral resources in the VCMD were 
assessed using a modified version of a 

computer simulation model (ROCKVAL) 
developed jointly by the Bureau and the 
ADGGS (29, 54). The assessment was 
accomplished as part of a cooperative 
agreement between the ADGGS and the 
Bureau. An assessment committee was 
composed of geologists and engineers from 
the Bureau, ADGGS, and the University of 
Alaska, Fairbanks (UAF). The committee 
members were participants in the collection 
and analysis of samples during the field 
investigation portion of the VCMD study, 
and are intimately familiar with the district. 

The computer simulation made extensive 
use of "generic" deposit-based models for 
initial estimations of deposit parameters. 
The number of mineral deposits and their 
associated grades and tonnages were 
estimated by using generic probability 
distributions for particular deposit types, 
based on compilations derived from world- 
wide literature. Specific knowledge about 
the occurrence of deposits within the VCMD 
was used to modify these parameters, where 
appropriate, by the assessment committee. 
The results of the assessment represent a 
mineral resource endowment for the VCMD. 
The assessment results can be used to derive 
an estimate of the economic value of the 
mineral resources in the study area, using an 
appropriate economic model. 

The results of the ROCKVAL analysis can 
be described in several ways. Table 5 gives 
the total estimated endowment for each 
major element present in major concentration 
at three probability levels. This data 
indicated that gold is the element of greatest 
significance (at present-day metal values), 
accounting for approximately one-half of the 
present-day gross metal value in the district. 
At high probability fractiles (high levels of 
certainty), the elements copper (Cu), tin 

3 By Rainer Newberry, Professor of Geology, University of Alaska, Fairbanks, Alaska. 


Element (units) fractile 

Gold (10° oz) 
“Silver (06 02) 

Copper (1 

Molybdenum (10? st) | 1 | 16 | 160 
Tee oes 
Palladum 06a) | 0 | ae 
"Nickel (10° st) _ 

_ Chromium (10° st) _ 

TABLE 5. - Estimated total endowment for the most 
significant metals in the VCMD. 

(Sn), and zinc (Zn) also make an appreciable 
contribution to the district endowments’ 
gross metal value. 

In order to show and compare the 
contributions of the various deposit types to 
the overall metal endowment of the VCMD, 
contained metals are presented on a deposit 
type by deposit type basis, with each metal 
converted to 1 million ounce gold 
equivalents (using summer 1990 metal 
prices) in Table 6. This tabulation provides 
a measure of the relative value of each 
deposit type, highly simplified because the 
elements in many cases are not present in 
high enough concentrations or appropriate 
mineralogy for presently economic extraction 
and beneficiation. The results shown in 
Table 5 are arranged in descending order of 
gold-equivalent endowment at the 95% 
probability level. The areas judged 
favorable for the various deposit types are 
shown on figures 17-20. 

The estimated endowment as presented in 
Tables 4 and 5 is biased towards those 
deposit types with the greatest amount of 
drilled reserves or other strong indications of 
existence. Placer gold deposits are the pre- 


eminent source (~40%) of the metal value 
of the endowment at the 95% probability 
level not only because it represents the 
single deposit type for which there has been 
appreciable mining, but also because placer 
resource estimates can be semiconfidently 
made based on limited surface sampling and 
comparison with known production. The 
order of endowment contribution following 
placer gold mostly reflects the published 
amounts of metal determined thus far from 
drilling and underground sampling at the 
major known deposits in the VCMD. These 
are: (1) Coal Creek tin-silver-zinc greisen; 
(2) Denali Copper sediment hosted copper- 
silver; (3) Golden Zone plutonic related 
gold; and (4) Zackly copper-gold-silver 

Also present in Table 6 is the estimated 
metal endowment for the different deposit 
types for the 50% and 5% probability levels. 
The sometimes large disparities between the 
95% probability level and the lower 
probability levels reflects the speculative 
nature of the endowment estimations at the 
lower probability levels. Placer gold is still 
the pre-eminent contribution to _ the 
endowment at the 50% probability level 
(=~ 23%), but as there is a distinctly limited 
amount of gold-bearing gravel present, and 
an almost unlimited amount of unexposed 
and buried rock below the surface, there is 
a low probability for a large contribution to 
the endowment caused by several other 
deposit types. 

The bulk of the present-day gross metal 
value of the endowment (except placer gold) 
lies in plutonic-related deposits, including 
skarns, vein-replacement gold, plutonic tin- 
silver-zinc, various porphyry-type deposits, 
and ultramafic-hosted deposits. This partly 
reflects the large amount and variety of 
plutonic rocks in the district and the variety 
of plutonic-related deposits known to exist, 

Probability fractile 
Deposit type/contained metal (units) 

Placer gold deposits 
Gold (10° oz) Se 
platinum (106 one 
Tin-silver deposits _ 
Tin (4X10 st) 
- Silver (10* OZ) SS Q =e aes 
“Zine (2X10° st) 
Sediment hosted copper deposits _ 
! Copper (2X10* sy 
Silver (10802) 
~ Gold (10° oz) J 
Plutonic related gold deposits 
Gold (10° oz) 
Silver melt oz) 8 
Metamorphic gold deposits 
23 Gold de ee Ss ae 
"Silver (10° on i. 
-Copper-gold-skarn deposits. 
Gold (10° oz) sae 
‘Silver (10% oz) ee 
Copper (2X10° st) 
“Porphyry molybdenum deposits/ molybdenum X10" st) 

Podiform chromite eme chromite ae ih 
_ Porphyry copper deposits — A 
Copper ae av 
cect a = ee SE: 
- Molybdenum (SX10* st) _ 
Basalt related eobee deposits 
Copper. (2X10° st) 
Silver (10* oz) 
Carbonate hosted gold deposits 
Gold (10° oz) 
‘Sivecd0to2  . 
PGM sulfide deposits 
: Platinum (10% oz) 
Palladium (3X10° 02) 
- Copper (2X10% st) eS ee Serer 
Nickel (5X10* st) did 
= Volcanogenic massive sulfide deposits — 
Copper, X10" os 


TABLE 6. - Estimated summary endowment for the VCMD, by deposit type, expressed as 10° oz gold equivalents. 




=I Low favorability RTolkeetna . 
20159 F j 




' GY 


a be Scale, miles : 7 2 
a "< oA YY ee 
c ‘ Ss y GUY —-— 
Valdez Creek Mining District a ey ly G ‘ 

1 ~ yy zl A = 
‘ PE ~ Yl“ iN City. —- 
j DZ pS SLI QYYP™ 4 fp 
ig ; De y y, a “ia 2 “ 


Y = 
iver Up HD pa 
Sz We 8 






E ; bn, oe 
Petersvillee ¢ pj Wiz 
etersvillee ot s } ‘ a Via 
: S f % GO 
LEGEND : , 5 

ZG righ tavorability 


‘ es 

FIGURE 17. - Regions favorable for the occurrence of placer gold. 




1511530" *00° . 5 ered 30: 147 °00" 
T oe 150°30 15000" 149 *30° 149°00" 148 "30" 148°00 1a50 T ui 
T T T Ty Ir T T 
C 4 
peek) 3 by +{63°30" 
63°30" ( Ls 
Ns )) 
5 10 15 } 
{] Cantwell 
Scale, mile: = 
. , be 
BSNS ve 
Valdez Creek Mining District 
=a AVA 
Waal tia a aS 
Mount McKinley a 
63°00’ 63°00 
62°30°L AD AALS 
etersvillee’, OY 7) 
Metamorphic gold veins WAV AVAVAVAY, 
y ~ 
Vj Basalt—hosted copper cikealne 
° 162° Vo: 
62°15'F Sediment—hosted, basalt— 
related copper ig a 
[MM] Volcanogenic massive sulfide ' 
Sie SS. < 
an - -_— 
é \ _——— 
2 oje® ; 
e 2800 157° 30" n N ( L ! 1 1 st 146°30" a 
00" = 1 Le 5 2340" 147° 00’ 
151° 00 150° 30’ 150° 00 749 °30" 749 °00° 748° 30° 148°00 147° 30 

FIGURE 18. - Regions favorable for the occurrence of metamorphic gold veins, basalt-hosted copper, sediment-hosted and basalt-related 

copper, and volcanogenic massive sulfides. 

— 62° 30° 




151° 30° 

Scale, miles 




eee as \ 

63 *30'T 


& qb 
0 |— 
JE e 
a ia | 
ag i 
#3 | 5 
NZ os = 
On SF 
see Is, 
‘ S 
Lo ogy Sa 
FX “Wen. 
Sat and Sp) oat 
= i 
oie Ochs ve Ss 
i = £ S +", 
| | +R ES o 
Oo Uo a if 2 fe 
ozo vU co 
D2 O29 5 Y5 
fee HRS t 
we} — le 5 
= 2 we 3 oc 
2 = ~*%& +O Oo v ese 
= a Col2 oko © E 
a © —>—O WH ioe o? 
a - S90 YU> y ” Po * 
4 a Of OD Gg ° oo 2 
= Pe ” Oo = 39 c 
E = oS Gz v a i 
< ae 
: : 2 oéses Se 
— Oo+ 
; : Syecbes #2 
(a) 5 OYO% 06 4 ie 
° Qa Soe Stes ore 56 
S z 2 295 SSS g0 
= Q@>Q>550 06 gag 
> SY ©@o 
+ ° 
4 N a oe 
Le wo 
ee ea = 
5 2 I ai 
79) Ss 5 = 
& © < 8 ra) =) 
@ PA) w . : = 
© © ts PS N 

FIGURE 19. - Regions favorable for the occurrence of plutonic associated gold-bearing veins, ultramafic associated podiform chromite, 

and carbonate-hosted gold-silver. 







62° 1/5" 


fat 151° 00' 150 *30° 150°00" 149 °30' 146008 148 °30" 148°90' 147°30' Sie Os T 
iF ot = | 79 ar T 
‘ —S 
ee c eae 
im ( Si NS 
) — oe 8 ve NC 63°30 
L } Re i S 
f x 
Sy ' om : 
5 Io 8 ) aN 
S er ‘ \ 
Scale, miles rer ih 
ee aA 
yr : Yy ., ; 
: e : a YA jf 63°15’ 
ee aS : b We (7 lps yp 
Valdez Creek Mining District 5 . 
» s Yd e Zack! 
Ne Ohio Creek Copper—gold skarn =) 
Tin greisen— —— 
See iatl ve 
“3 In po.ymela allic veins 
Mount McKinley a wa Bs \ 
le ae ) 63°00" 
r= ¢ 
o We 
& y) 
& Wi 
x ’ 
a Pa 
\ 62 °45' 
IE x 
Lake N _|62*30° 
Petersvillee’, ee Su x 
= Susitna : ) 
LEGEND Lake » 
Ee Porphyry molybdenum ( 
Lake \ 
Porphyry copper Louise J] alee, 
ir GEES Tin polmetallic veins je a ; 
r ° 
LZ. Copper—gold skarns : 
FE Ultramafic associated nickel— % 
ed COopper—PGM sulfide Roag 
Note: Deposits that were specifically modeled é HIgh oY 
in the probabilistic assessment are identified 3 
by name. ver 
a { i ea 62° 00° 
=30" 1 Nl 00" 146°30' 
151° 30 ASANO: SEGRE? EE saatio 147° 00 

FIGURE 20. - Regions favorable for the occurrence of porphyry molybdenum and copper, tin-bearing polymetallic veins, 
skarns, and ultramafic associated nickel-copper-PGM sulfides. 


and partly reflects the fact that many 
plutonic-related deposit types contain huge 
amounts of metal. Much of this plutonic- 
related endowment is highly speculative, 
however, because so little is known about 
the plutonic rocks in the district. 

An economic assessment of the 
endowment in the VCMD is beyond the 
scope of this report, but it should be noted 
that placer deposits not only constitute the 
bulk of the "near-certain" component of the 
endowment, but they also constitute that 
portion most amenable to ready extraction. 
Of the lode deposit types, the plutonic- and 
metamorphic-gold deposits are probably 
most minable at the present. It is unlikely, 
given current transportation and metal prices 
that the other components to the endowment 
could be economically recovered in large 
amounts at the present time. 


hes VCMD contains many areas that are 

geologically favorable for the existence 
of a considerable variety of mineral deposits. 
Many areas within the district are under- 
explored, and deserve greater attention. 
Even though the Bureau invested three field 
seasons in the VCMD, the immense size and 
location of the district precludes complete 
coverage of the entire surface area. The 
remoteness of the district, like much of 
Alaska, is the greatest hindrance to 
geologists and prospectors in their mineral 
exploration efforts, and is the main reason 
that the district has a good potential for 
containing undiscovered mineral deposits. 
As a result of the Bureau’s investigation, the 
land has relinquished some of its geological 
secrets, and the Bureau has shown that there 
are areas that do indeed _ contain 
undiscovered mineral occurrences. There 


are many areas in the district that show 
promise for future mineral discoveries. 
Some of these deserve special mention here. 

The McCallie Glacier disseminated sulfide 
and polymetallic stockwork vein occurrence, 
located in the central Alaska Range, should 
be thoroughly prospected throughout the 
entire head-wall area of the McCallie 
Glacier. Samples collected at the occurrence 
in 1989 show that the mineralization 
discovered the previous year continues in a 
southwesterly trend for at least ‘2 mile. 
Technical climbing expertise and gear will 
be needed to thoroughly investigate the 

The Ready Cash prospect, located in the 
Ohio Creek drainage, has had some 
development work in the past, but not to the 
degree necessary to determine if there is an 
economic ore body present. The prospect 
needs to be systematically mapped, sampled, 
and drilled in order to adequately determine 
the true nature of the deposit. 

Across the Chulitna River valley from the 
Ready Cash is the Honolulu prospect. The 
prospect has had some drilling, but the work 
done was not sufficient to fully evaluate the 
prospect. The prospect needs to be further 
investigated through geologic mapping, 
detailed sampling, and drilling. 

The Bureau collected numerous samples 
that were anomalous in gold, silver, lead, 
and zinc at the head of the drainage in which 
the Honolulu prospect is located. This area 
also deserves a close look for sulfide veins 
that could possibly contain  tin-silver 

At the headwaters of Honolulu Creek, 
several placer samples were collected that 
contained highly anomalous levels of placer 
gold. It has not been determined where the 
possible lode source for the placer gold is 
located, hence the area deserves a greater 
prospecting effort to locate placer gold and 

possible lode gold resources. 

Based on several placer samples collected 
from the lower reaches of the East Fork 
Chulitna River, there is a potential gold- 
placer resource downstream from _ the 
terminal moraine in the East Fork valley. It 
appears that erosion of the East Fork 
through the terminal moraine is 
concentrating a gold-placer that exists in the 
moraine. Prospecting should be 
concentrated on the benches and gravel bars 
below the moraine. The use of a backhoe 
would enable proper evaluation of the 

The Bureau collected several samples from 
a series of tributaries that flow north into the 
Susitna River in the Devils Canyon area that 
were anomalous in platinum, gold, silver, 
arsenic, copper, molybdenum, lead, tin, and 
zinc. The samples could represent minerals 
that are being disseminated downstream 
from a lode source in the granitic highlands 
to the south. There are few rock exposures 
in the region south of the sample sites, and 
the area has been largely unexplored. 
Therefore, a significant potential exists for 
mineral discoveries in the region if a 
systematic geological, geochemical, and 
geophysical investigation is conducted in this 

The Tsusena Creek prospect exhibits high- 
grade tin-silver mineralization in 
hydrothermal polymetallic veins and 
mineralized shear zones. The prospect has 
previously been geologically mapped and 
sampled by private industry, and additional 
sampling by the Bureau has confirmed the 
presence of high-grade mineralization. The 
prospect could represent tin-silver vein type 
mineralization associated with a tin granite. 
Further geologic mapping, geochemical 
sampling, and drilling is needed to properly 
assess the mineral development potential of 
the prospect. 


In the Watana Creek drainage, the lower 
reaches of the creek drain through a Tertiary 
conglomerate unit. The Delusion Creek 
tributary to Watana Creek also drains 
through areas of Tertiary conglomerate. 
Both creeks contain potential gold-placer 
resources. There have been gold-placer 
claims staked on both creeks in the past, and 
the Bureau documented the presence of 
significant placer gold in the fluvial gravel. 
Both of these drainages should be further 
explored for gold-placers. A suction dredge 
or backhoe would enable the proper 
examination of the potential resource. 

Reconnaissance placer exploration in the 
East Fork Susitna River drainage resulted in 
the discovery of two tributary creeks that 
contain significant levels of placer gold. 
Prospecting in the hanging valleys of the 
tributary creeks showed that the source for 
the placer gold is located below the lip of 
the hanging valley. A sample collected from 
the lateral moraine along the north valley 
wall of the East Fork Susitna River 
contained placer gold in significant, but un- 
weighable quantity. This suggests that the 
lateral moraine contains a disseminated gold- 
placer resource, and that the tributaries are 
concentrating the disseminated gold by 
eroding through the lateral moraine. The 
entire drainage of the East Fork should be 
prospected for occurrences of placer gold, 
and for the lode source of the disseminated 
gold that exists in the lateral moraine. The 
alluvial fans of the tributaries should be 
evaluated as a potential economic source of 
placer gold. 

The Viking copper-gold-magnetite vein 
occurrence exists 3 miles northeast of the 
Zackly skarn prospect, and is hosted in 
metavolcanic rocks. This occurrence 
contains areas of high-grade gold-copper 
mineralization as documented by Bureau 
sample results. Little is known about the 


FIGURE 21. - Bureau geologist collecting a placer sample from a tributary to the Susitna Glacier. 

extent of mineralization at the Viking, hence a detailed geological mapping and geo- 
it 1s recommended that the occurrence be chemical sampling program. 
geologically mapped and sampled in detail. Related to the Eureka Glacier occurrence 
The Eureka Glacier ultramafic-associated is the Peak 5532 (Butte Creek) ultramafic- 
PGM-nickel-chrome occurrence is an associated copper-nickel-PGM disseminated 
attractive exploration target for many sulfide occurrence. Like the Eureka Glacier 
reasons. The occurrence is centered along a occurrence, Butte Creek ultramafic rocks 
trend of ultramafic rocks that outcrop also outcrop over a large area, and should be 
infrequently over a distance that extends to mapped and sampled in detail. 
Slate Creek 60 miles to the southeast, and to The Mex and the Gossan mineral 
Butte Creek 55 miles to the southwest (55). occurrences, near the head of Little 
The Broxon Gulch occurrence, located Clearwater Creek, have potential for 
several miles to the east, is genetically disseminated and stockwork-type precious 
related, and has associated massive copper- metal deposits. Altered carbonate sediments 
nickel-sulfide mineralization. Aerially, the and Carlin-type metal assemblages at the 
ultramafic rocks associated with the Eureka Mex and the Gossan occurrences suggest the 
Glacier occurrence cover close to 100 acres, presence of a sediment-hosted low-grade, 
and contain sulfide mineralization in several large-tonnage precious-metals deposit. As 
locations. A thorough examination of this with other geochemically anomalous and 
occurrence is warranted and should involve geologically favorable areas in the VCMD, 


these occurrences should be mapped and 
sampled in detail. Mapping and sampling 
completed to date at these occurrences could 
possibly provide drilling targets. 

The Windy Creek drainage flows parallel 
to and just south of the Valdez Creek 
drainage. Even though a small section of 
the lower portion of Windy Creek has been 
drilled on a widely spaced grid for gold- 
placer deposits (33), the creek has potential 
for placer gold beyond those areas already 
drilled, and represents a significant gold 
placer exploration target. 

A newly discovered area at the headwaters 

of the West Fork Maclaren River (33) has 
potential for placer and lode gold 
occurrences. Reconnaissance placer samples 
collected at the confluence of three glacial 
tributaries (also known as "Three Glaciers") 
to the West Fork contained anomalous 
quantities of placer gold, and indicate that 
there is potential for a gold-placer deposit 
and related lode gold deposit(s). The area 
should have additional reconnaissance 
geochemical sampling and geologic mapping 
performed to locate potential gold-bearing 
rocks, and the streams should be investigated 
for gold-placer resources. 

FIGURE 22. - Bureau geologist collecting a rock sample near the source of the Susitna River. 



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BLM Library 
Denver Federal Center 

Bldg. 50, OC-521 
PO. Box 25047 
Denver, CO 80225 

TN Balen, Michael D. 

174 Executive summary of the 
.A4 bureau of mines 

B3 investigations in the Valdez 
199f Creek mining districe, 


ABOVE - The "Mountain" is known locally by its Athapaskan name Denali, meaning "the great one". The 
mountain is otherwise known as Mt. Mckinley. This view is of the south face with the Ruth Glacier in the 
foreground. Denali can be seen from many locations with the Valdez Creek Mining District. 

BACK COVER - Bureau geologist is dwarfed by the high rugged mountains of the Alaska Range.