Gold was initially reported in the Wyoming Territory in 1842 by a fur trapper from
the American Fur Company who had been working a trap line along the Sweetwater River near the Wind River
Mountains. The location of this discovery may have been along Strawberry Creek,
a tributary of the Sweetwater River located near the eastern edge of the South
Pass greenstone belt. South Pass lies south of the town of Lander.
Greenstone belts form
geological (structural) basins filled with primitive volcanic flows and sediments that were intruded by
dikes, sills and stocks and deposited along the margins of
ancient proto-continents. These were later deformed and metamorphosed. To many geologists and prospectors,
‘greenstone
belts’ are synonymous with
‘gold belts’ since they provide
excellent places to search for gold. Such basins are typically >2 billion
years old: the majority of rocks in the South Pass greenstone belt were
metamorphosed >2.8 billion years and were likely deposited 3+ billion years
ago. Some of the more notable greenstone belts in the world are located in the
Slave and Abitibi regions of Canada, the Pilbara and Yilgarn regions in Western
Australia, and the Kaapvaal and Barberton regions of Africa – all are well known
for significant gold deposits.
Essentially all rocks in
greenstone belts have slightly higher than normal gold content. Those in the
South Pass greenstone belt
typically average 2 to 10 times the amount of gold as average crustal abundance,
thus these provided an excellent source for gold deposits that likely formed during regional metamorphism
and deformation (Hausel, 1991).
When circumstances are right, greenstone belts
provide good source beds for lode gold. What is required is hot metamorphic fluids to migrate through the basins and leach
enough rock and then focusing the gold-bearing hydrothermal fluids in
faults, veins or similar traps to produce
ore shoots (enriched pockets)
of gold. This happened in several greenstone belts around the world simply
because mother earth was brutal to these basins but she provided several opportunities to leach gold from the layered rocks and focus
the gold into traps. Such traps include fractures, intersecting fractures and
veins, shear zones, stockworks, fold closures and chemically reactive rocks. For the most
part, fractures, or zones of lower pressure, were ideal for gold-bearing fluids
that were squeezed from the adjacent ductile rocks under great pressure and
temperature.
 |
A tight fold in mica-rich quartzite (meta-graywacke) at South Pass.
The knife sits along a fracture. The rock above this fracture
has graded bedding – coarser sand grains that decrease in size
towards the top similar to what is found in modern streams. This
tells geologists that the top of this rock was towards the top of the photo
3 billion years ago. Below this fracture we have contradictory
evidence. Cross beds, (also found in modern streams), typically are cut (terminate)
by stream action. The small cross bed at the bottom indicates the top of this part
of the outcrop was in the opposite direction as the graded beds. The only explanation
is the fracture represents a fold axis and the outcrop below & above the fracture was
at one time facing in the same direction until folded along a very tight (isoclinal) fold.
The nose of the fold lies either somewhere at depth in the rock outcrop perpendicular
to the fracture, or lies somewhere in space and long since been removed by erosion. |
To see how this works, take
your hands, place them in front of you. Now touch your finger tips together. The
top of each hand would represent the top of the rock unit when it was deposited.
Now let your finger tips act as a hinge and bring your palms together: the top
of your right hand should be in the opposite direction as your left hand.
 |
A 34-ounce nugget found in the
Rock Creek drainage during
dredging prior to World War II. Specimen from the
Los
Angeles Museum |
All greenstone belts exhibit many
very tight folds, many faults, fractures, and shear zones as a result of the
tectonic processes that crushed and mangled these regions over eons of time. In
places, greenstone belts are almost like accordions because of the many folds
stacked on top of one another. Often, it is difficult to tell which rocks are
right side up and which are overturned. So intense is the deformation that we
can actually map rock sitting right side up adjacent to rock that is completely
overturned within inches of one another. To complicate matters further, these
belts are often intruded along their margins by large granite batholiths. They
also inter-finger (and lie on) with much older gneissic terrains that were the
basement complexes that the greenstones were deposited on. To most geologists,
these belts are a nightmare to map, as the geology and geological history are
very complex and never obvious. The gneissic complex for the South Pass
greenstone belt was mapped along Anderson Ridge and Lewiston Lakes areas. These
gneisses are undated, but may be as old as 3.5 to 3.8 billion
years.
Wyoming has four greenstone belts (
Elmer’s
Rock, Rattlesnake
Hills, Seminoe
Mountains and
South Pass)
and one large metasedimentary belt with similarities to greenstone belts (Copper
Mountain). All remained unmapped and only partially explored until the 1980s and
1990s. The author mapped all of them with the exception of Elmer’s Rock, which
was mapped by Graff and others (1982). For the most part, greenstone belts are
formed of dark to black rocks with some dark green rocks that are difficult to
differentiate and only a handful of geologists find great joy in the challenge
of unraveling these complex geological puzzles.
 |
Dark meta-basalt folded into an isoclinal fold in which the fold is so tight that the
fold limbs parallel one another. Below – fold in banded iron formation displaying very tight folds, almost like an accordion. |
Along
with complex geology, there is usually gold in many fractures, faults, veins and
folds. The problem is finding where the gold has been enriched enough to produce
‘ore shoots’ that contain minable quantities of gold. Often, ore bodies in
greenstone belts sit right under our noses and are consistently missed by
geologists and prospectors because of the complex geology. It takes considerable
detective work to figure out where ore shoots are located in lodes and how they
are oriented. When the lodes
are located, rich placers are
almost always found immediately downstream.
In
1855, territorial records show that a group of 40 prospectors including the
original fur trapper traveled back to South Pass from Georgia in search of the
gold in the Sweetwater River or Strawberry Creek. The group reportedly found
gold everywhere in the Sweetwater River and its tributaries. In the winter, they
traveled from South Pass to a more hospitable environment at Ft Laramie to the
east (a distance of 220 miles as the crow flies). For some unknown reason, they
were arrested upon arrival at Ft. Laramie. Three years later in 1858, one member
of this group along with 8 other prospectors ventured back to South Pass, and in
1860 commenced mining along Strawberry Creek near the site of the original
discovery site.
.jpg) |
Carissa mine shear zone show location of the
primary gold shear that averages 0.15 to 0.3 opt Au,
a geologist for scale, and the surrounding rock for
at least 1,000 feet is also highly fractures and
mineralized. Samples in this structure yield gold
values of 0.02 to 0.07 opt Au over 300 feet, the
rest of it remains to be sampled. |
In 1861, another group of prospectors began mining
along Willow Creek, 15 miles west of Strawberry Creek. This group of 52
prospectors was attacked by Shoshone Indians and driven out. In 1863, another
group of prospectors discovered gold in dry placers near Dickie Springs adjacent
to the Oregon Buttes along the Overland trail several miles south of Willow
Creek and worked the area for 3 months before being attacked by Indians. Most of
the prospectors were killed. At this time in history, little could be done to
provide security for prospecting groups as the nation was in the grips of civil
war.
Over the next several years, hostilities between prospectors and the
Shoshone intensified requiring that the Overland Trail be abandoned for a more
southerly route (Hausel and Love, 1993). These kinds of hostilities were common
in Wyoming and were one of many reasons why Wyoming remained relatively
unprospected compared to other territories in the West. Wyoming remained a
wilderness that few settlers dared to journey into. Today, instead of Indian
hostilities, both the State and Federal Government bureaucrats have taken on
hostilities against prospectors and miners.
Another group of prospectors
entered South Pass in 1866 to mine gold in Willow Creek. In the following year,
this group traced gold up Willow Creek to Carissa Gulch, which was rich in gold.
From the mouth of the gulch, the precious metal was traced further up slope to
the Carissa lode. Claims were filed on the lode on June 8th, 1867. Within a
short time, this group of prospectors was attacked by Indians and three were
killed: the surviving members fled, but returned more than a month later on July
28th. During the ensuing winter, more than 400 ounces of gold were recovered
using very primitive hand tools and mortars. Four tons of high grade ore was
hauled to Springville, Utah and milled yielding an astounding 1,400 ounces of
gold! News of the discovery reached the outside world and a rush
followed.
 |
Generalized geological map of
the South Pass-Atlantic City district (from
Hausel, 1989,
1991) |
The district was initially called the
Shoshone district. Then it was divided into smaller districts that included an
area east of the Carissa near Rock Creek which became known as the California
district. Four towns erupted along the pediment at South Pass. South Pass City
boasted 5,000 citizens – most living in tents (some reports suggested as many as
10,000 people were in South Pass City). Hamilton City (Miners Delight) grew to
1,500 people and Atlantic City had 500 citizens. Pacific City in the Pacific
district to the south near Oregon Buttes claimed 600 people. In 1870, the US
Army established Camp Stambaugh a few miles east of Atlantic City and Hamilton
City to add stability in the area. The camp was abandoned eight years
later.
In 1872, the district had 12 operating stamp mills. A few years
later, in 1879, another town was established east of South Pass City near the
original gold discovery. This town became known as Lewiston (Lewiston, Miners
Delight and Pacific City are now ghost towns). In 1884, an engineering project
was initiated with the construction of the Granier Ditch. The ditch was built to
haul water from Lake Christina 12 miles to the west in the high peaks of the
Wind River Mountains to the South Pass area for hydraulic mining. This project
was finished in 1890. In the following year, 6,720 ounces of gold were recovered
at the hydraulic mine.
 |
Oregon Buttes on the horizon.
Nearly
all of the land in the sunlight on the
horizon is part of a giant
gold deposit
known as the Dickie Springs-Oregon
Buttes paleoplacer
estimaed to
contain >28.5 million ounces of gold
according to the
USGS. |
When I began mapping in the
South Pass greenstone belt
in the 1980s, I was quite impressed by the size of the belt and amazed that such
an important district had remained mostly unmapped and poorly explored in modern
times. Little information was available on the historical mines and mineralized
zones in the district. Thus over the course of several years, I mapped 250
square miles of the complex, identified a
few hundred gold anomalies,
mapped all of the old mines I could get access to, and divided the greenstone
belt into two separate districts based on geology: the Lewiston district along
the eastern limb of the basin and the South-Pass-Atlantic City district along
the western limb (Hausel, 1991). Two other districts were recognized in Tertiary
and Recent sediments by the US Geological Survey that eroded from the South Pass
greenstone belt. These were McGraw Flats to the north and Oregon Buttes-Dickie
Springs to the south. Both contain large dry paleoplacers (fossil placers) with
minor modern placers.
The
greatest gold concentrations in the greenstone belt occur in faults (shear
zones) in the Lewiston district and in similar structures in the South
Pass-Atlantic City district. These structures that geologists refer to as shear
zones, were identified by past prospectors and miners. Even though the shear
zones all have anomalous gold, only sporadic ore shoots of limited strike length
contain minable quantities of gold. But these ore shoots occur primarily in fold
closures (known as
saddle reefs)
that steeply plunge down into the earth to unknown depths (possibly a few
thousand feet or more). Thus in some cases, some of these saddle reefs likely
host hundreds of thousands to millions of ounces of gold. But all past
exploration focused only on two dimensions at the surface (the length and width)
when exploration should have emphasized the forgotten third dimension, which is
potentially the greatest of the three. The third dimension is that of the plunge
of the ore shoots which continues down dip into the earth to unknown depths.
Past drilling at the Carissa mine suggests these may plunge to very great
depths. Ore shoots at South Pass have the appearance of dipping rods that pinch
and swell as they continue down into the earth.
 |
Gold panned from Dickie
Springs
(photo from J.D. Love). |
The richest stream
placers in the belt lie immediately downstream from these structures. The nearer
the placer gravels lie to shear zones, the greater the amount of gold is found
in the gravel. Immense amounts of gold were described by the US Geological
Survey in giant paleoplacers near Oregon Buttes to the south and in the McGraw
Flats area to the north. The amount of gold estimated for the Oregon Buttes
paleoplacer by the US Geological Survey was 28.5 million ounces (Figure 5). All
eroded from the South Pass greenstone belt.
 |
| Rock Creek placer with old
tailings |
Within the greenstone belt are many significant
ore shoots. The richest discovered to date, was that of the Carissa lode near
South Pass City. This mine lies a short distance southeast of State Highway 28.
During mapping, I was impressed by the immensity
of this gold-bearing structure. This structure consists of a prominent,
relatively narrow, shear zone that has high-grade gold values. The structure
averages 0.15 to 0.3 ounces per ton gold, which is not bad considering that the
Homestake mine averaged about 0.3 opt throughout its lifetime. The principal
structure at the Carissa is contained in a larger fracture envelope that is
essentially untested and was missed by nearly every mining company. Composite
chip samples collected within this larger structure over a width of many feet
ranged from 0.02 to 0.07 ounce per ton gold, considered to be potentially
economic and comparable to many operating gold mines in Nevada.
Past
gold production from the mine is poorly documented, but available statistics
suggest 50,000 to more than 180,000 ounces of gold were produced prior to 1950.
The Carissa shaft was sunk to a depth of 350 feet with more than 2,300 feet of
drifts on four levels over a strike length of 750 feet. A winze was later sunk
to a 5th level at a depth of 400 feet below the surface.
 |
Steve Gyorvary standing in mine-out
portion of the Carissa shear zone. The
empty space is where the shear zone was
located. |
The mined ore
contained a trace to 2.6 ounces per ton of gold (opt Au). Some specimen-grade
samples were recovered that assayed as high as 260 opt Au. An assay map of the
mine compiled in 1926 indicates the mine terminated in mineralized rock in every
direction. Later drilling in the 1970s and 1980s proved that the ore shoot
continued below the mine workings suggesting the mine to have considerable
potential.
The
mine was developed in a shear zone in dark rock known as metagraywacke (a
metamorphosed, micaceous sandstone) of the Miners Delight Formation and a mafic
dike (metamorphosed igneous rock or gabbro). Essentially, all prospecting
efforts concentrated on the primary shear, as it contained ore shoots of
high-grade gold. The structure averaged about 6 feet wide, is 2 to 3 feet wide
at the surface, but swelled to 50 feet at depth. More importantly, this primary
shear lies within a much larger shear that isn’t quite as distinct and was
essentially overlooked. This larger structure forms an envelope surrounding the
primary shear that is >1,000 feet wide. The envelope is expressed by numerous
parallel fractures with numerous quartz veinlets.
.jpg)
The results
of the sampling suggest that the Carissa lode is a large-tonnage gold deposit
that could have been developed by open pit and underground operations. The gold
ore continues below the mine workings based on drilling by Anaconda Minerals
Company in 1974. Anaconda intersected 16.1 feet of gold-bearing shear beneath
the mine workings that averaged 0.13 opt Au. A small section in this zone
assayed 1.6 opt Au! At 700 to 970 feet, the mineralized shear was intersected in
four drill holes. These assayed 0.11 to 0.36 ounce per ton gold over widths of
2.3 to 11.9 feet.
In
the 1980s, Consolidated McKinney Resources intersected an 80-foot mineralized
zone beneath the mine workings that assayed 0.031 to 2.54 ounces per ton gold!
In addition, one intercept contained >5 opt over several feet. All of these
are verifiable and provide evidence for a significant to major gold deposit at
the Carissa. Based on drilling, mining and surface sampling, the Carissa ore
shoot has a minimum strike length of 950 feet that is open at either end. This
shoot is more than 1000 feet wide and continues to a minimum depth of 970 feet
and is open at depth. This shear structure is traced on the surface to the
northeast and southwest for several thousand feet and most of it remains
unsampled. Such shear zones typically continue to a few thousand feet deep in
similar greenstone belts worldwide.
.jpg) |
Right- folded parallel veins in the Carissa Shear Envelop. This rock
covers >1,000 feet of width surrounding the primary Carissa Shear
and is also highly mineralized forming an ore zone that is economic and
could easily be mined by open pit. Channel samples collected in this zone
by the author ranged from 0.02 to 0.07 opt Au. |
Beeler
(1908) reported the ore in the primary shear to average 0.3 opt Au. Composite
chip samples in the giant low-grade shear envelope enclosing this primary
structure yielded anomalous gold over a width of 300 feet: these samples yielded
0.02 to 0.05 opt (Curran, 1926; Hausel, 1989). A 97-foot composite sample in
this zone assayed 0.023 opt Au and a 30-foot composite assayed 0.07 opt Au
(Hausel, 1991a): at today’s gold prices these would be considered economic. The
remaining envelope (700 feet) remains unsampled, but undoubtedly contains gold
based on the structure and presence of secondary quartz.
Based on
sampling, the Carissa has a distinct mineralized zone that is likely a few
thousand feet deep, as much as 1,000 feet wide, and 1,000 feet along strike.
However, the mineralized zone is open in all three directions and could be
enlarged considerably with additional drilling.
This would suggest, that
at an average ore grade of 0.1 opt Au, this zone potentially hosts
3.7 million ounces of unmined gold worth $4.4
billion dollars. This does not include potential resources
deeper than 1,000 feet or further along the strike length of the shear. In
effect, the Wyoming State legislature and Governor removed (nationalized) a
major gold deposit from the public sector that would have created numerous jobs
in Fremont County and provided a significant tax base to Wyoming and Fremont
County. Instead, in the wisdom we have come to love in government, Wyoming now
has a mining Disneyland sitting on a major ore deposit. This Disneyland may
produce a few thousand dollars in revenue for the state while at the same time
it sucks out a few $hundred thousand for budget and salaries to operate the
Wyoming Disneyland park.
The people who operate the South Pass City
historic site are very good at what they do and should be respected for their
knowledge. But the legislature and governor should have their heads
examined. This Disneyland appears to be spreading in a district that could provide many future jobs.
Dollars set aside for Federal abandoned mine reclamation programs were used to
rebuild the Carissa surface buildings and are being used to rebuild buildings on
private land at the Duncan mine, another probable ore body. When will government
ever be required to pay for their
actions?
_________________________________________________________________________
Table
1. Chip channel and channel sample analyses in the South Pass greenstone belt
(Hausel,
1989a).
_________________________________________________________________________
SAMPLE
DESCRIPTION Au
Carissa Mine (low-grade
envelope) (ppm)
0 to 10 ft north of shear
0.4
10 to 20 ft north of shear 1.05
20 to 37 ft north of shear 2.5
0 to 10 ft south of
shear 0.65
10 to 20 ft south of shear
0.25
20 to 30 ft south of shear 0.30
30 to 60 ft south of
shear 0.35
30 ft composite north of shear
2.4
_________________________________________________________________________
 |
The State of Wyoming purchased
the Carissa mine
(which sits on a major gold deposit) and
withdrew the
property from mining to reconstruct
a monument to mining where no man can
mine again. This
was done by the State Legislature without considering the
geology and ore deposits. Now the old workings attract a
few hundred
people a year while they sit on top of a gold
deposit estimated to contain
more than a few $billion in gold |
The Carissa ore is
structurally controlled and is interpreted as a saddle reef deposit where
high-grade gold is localized in fold closures and rehealed fractures similar to
the Homestake. The geological evidence suggests the ore-body continues to great
depth. Support for the presence of a major ore deposit includes drilling by
Consolidated McKinney Resources who identified a highly anomalous 80-foot wide
mineralized zone. Carissa Gold Inc. made the a reserve estimate years ago
without knowing there was a major shear envelope and had no data on the
mineralized structure beneath the mine working. Using an extraordinary high
reserve cutoff grade: 208,000 tons of ore at an average grade of 0.343 opt Au;
and geological reserves of 37,000 tons of ore averaging 0.85 opt
Au.
Anaconda Minerals Company drilled the property prior to Consolidated
McKinney Resources and all of their drill holes interested ore grade material.
They intersected a high grade ore zone over widths of 2.3 to 16.1 feet that
yielded 0.11 to 0.36 opt Au to depths of 700 feet.
The Wyoming
legislature & governor did what the Shoshone Indians of the past could not
do. The Wyoming legislature
‘nationalized’ this mine by purchasing
private property and incorporating it into the South Pass City historical site
without considering geological studies or scientific testimony. This was likely
one of the two best gold targets in the state. The other is located within the
Rattlesnake Hills where a
multi-million ounce gold deposit is currently being drilled.
Adjacent to the
mine is a dry gulch locally known as Carissa gulch. This gulch drains into
Willow Creek from the western extent of the lode. The eastern extent of the lode
is sampled by nearby Hermit Gulch. Both gulches should provide excellent places
to hunt for nuggets with metal detectors, but again, these have been withdrawn
from exploration as has been Willow Creek. Willow Creek is purported to have
dangerous mercury levels based solely on here say, yet it would likely produce
significant gold values.
Other
properties of interest at South Pass include Miners Delight and the Wolf mine
along with thousands of feet of unexplored shear zones in the South
Pass-Atlantic City district, the Lewiston district, and in the Crows nest.
The Miners Delight mine has a very attractive shear structure that yielded a
0.68 opt Au channel sample across about 8 feet and the Wolf mine yielded a grab
sample that assayed 0.5 opt Au. This shear is poorly exposed by was trenched by
one company that showed a shear that was 160 feet wide (Steve Gyorvary, personal
communication, 2010).
Other interesting deposits in Wyoming
include the Rattlesnake Hills and Seminoe greenstone belts. The author
identified a few hundred gold anomalies at South Pass, found the first several
significant gold anomalies in the Rattlesnake Hills, identified a significant
gold anomaly in the Seminoe Mountains and identified another gold anomaly at
Copper Mountain. The Elmer’s Rock greenstone belt remains essentially unexplored
for mineralization even though several indicator minerals have been found in
that region that suggest the presence of several hidden diamond deposits. In
addition,
two world-class
colored
gemstone deposits were found
along the flanks of the Elmer’s Rock belt that remains relatively unexplored.
The author also identified excellent gold targets in the Sierra Madre, southern
Laramie Range, Bearlodge Mountains and Mineral Hill (Hausel,
1987).
However, due to the lack of regard for the mining sector and
prospectors, the author recommends that companies and prospectors come to
Arizona, Nevada or Canada to search for
gold.
Recommended
Reading
Blackstone,
D.L., and Hausel, W.D., 1991, Guide to the geology and mineralization of the
Seminoe Mountains, Wyoming, in S. Roberts, editor, Mineral Resources of Wyoming:
Wyoming Geological Association 42nd Annual Field Conference Guidebook, p.
201-210.
Graff,
P.J., Sears, J.W., Holden, G.S., and Hausel, W.D., 1982, Geology of Elmer’s Rock
greenstone belt, Laramie Range, Wyoming: Geological Survey of Wyoming Report of
Investigations 14, 22 p.
Hausel,
W.D., 1987, Structural control of Archean gold mineralization within the South
Pass greenstone terrain, Wyoming (USA), in The Practical Applications of Trace
Elements and Isotopes to Environmental Biogeochemistry and Mineral Resources
Evaluation, Theophrastus Publications, Athens, Greece, p.199-216.
Hausel,
W.D., 1989, The Geology of Wyoming's Precious Metal Lode & Placer Deposits:
Geological Survey of Wyoming Bulletin 68, 248 p.
Hausel,
W.D., 1991, Economic Geology of the South Pass Granite-Greenstone Belt, Wind
River Mountains, Western Wyoming. Geological Survey of Wyoming Report of
Investigations 44, 129 p.
Hausel,
W.D., 1993, Mining History and geology of some of Wyoming’s metal and gemstone
districts: in Wyoming Geological Association Jubilee Anniversary Field
Conference Guidebook, p. 39-64.
Hausel,
W.D., 1994, Economic Geology of the Seminoe Mountains Mining District, Carbon
County, Wyoming: Wyoming State Geological Survey Report of Investigations 50, 31
p.
Hausel,
W.D., 1996, Economic Geology of the Rattlesnake Hills Supracrustal Belt, Natrona
County, Wyoming: Geological Survey of Wyoming Report of Investigations 52, 28
p.
Hausel,
W.D., 1997, The Geology of Wyoming's Copper, Lead, Zinc, Molybdenum and
Associated Metal Deposits: Geological Survey of Wyoming Bulletin 70, 224
p.
Hausel,
W.D., 2009,
Gems, Minerals and Rocks of Wyoming - A Guide for Rock Hounds,
Prospectors & Collectors. Booksurge, 175 p.
Hausel, W.D., and Hausel, E.J., 2011, GOLD - Field
Guide for Prospectors and Geologists (Wyoming Examples). CreateSpace,
366 p.
Hausel,
W.D., and Love, J.D., 1991, Guide to the geology and mineralization of the South
Pass area, in S. Roberts, editor, Mineral Resources of Wyoming: Wyoming
Geological Association 42nd Annual Field Conference Guidebook, p.
181-200.
Snyder,
G.L., Hausel, W.D., Klein, T.L., Houston, R.S., and Graff, P.J., 1989,
Precambrian Rocks & Mineralization, Wyoming Province: 28th International
Geological Congress guide to field trip T-332, July 19-25, 48 p.
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