Wednesday, September 25, 2013

Thar's Gold In Them Thar Hills


Overlooking South Pass
South Pass was a place I loved and a place where I figured I would retire. The only problem was traffic congestion; but with practice, one can get around that problem.  
Overlooking Atlantic City, Wyoming - my summer home for at least five years
when I mapped about 400 square miles, eight quadrangles and several
underground mines. Note the elevation and population (photo by
Sharon Hausel).
If there were any ducks at South Pass, I suspect the Robertson clan would be there.

Over three decades, I led dozens of field trips to South Pass and other gold districts around Wyoming to educate the public on prospecting. But from 2004 to 2007, the Wyoming Geological Survey, was operated by - well how do you say ....? Ah, I know, a complete moron. I take off my hat to the university hiring him without a background check. At least what is left of the decimated WGS is now free to rebuild, but one has to feel sorry for the people at the university.

South Pass was Wyoming's first gold discovery. Most of the greenstone belt and its gold districts remained poorly explored. When I started at the Geological Survey, I heard many people claim the region was mined out. This is what most people and nearly every historian who knows nothing about geology say about mining districts. When I decided to map the district in the 1980s, much of the district was unmapped and there was practically no information on any of the mines. It had been overlooked just like the Seminoe Mountains greenstone belt where I found visible gold and started a gold rush in 1981 and also the Rattlesnake Hills greenstone belt, where the geology was so favorable for large gold deposits, I couldn't believe no one had ever looked for major disseminated and high-grade gold deposits. Anyone who has studied gold deposits should have been in these three areas.

Come to think of it, I have a start on my beard and
hair (actually I had long hair all though HS and college)
so maybe I could be an honorary Duck Dynasty
distant cousin.
So, is South Pass finally mined out? Nope! Since I investigated the district in the 1980s and published my book on the district in 1991, only a small amount of gold has been taken out. But get this - the Carissa gold mine, was only partially mined when the Wyoming State Legislature in the wisdom that can only be described as political, under-the-table, wisdom, decided to buy the mine from a private owner and place it in their South Pass City historical state park - a park that generates a few $hundred (maybe a few $thousand in some years) for the general fund. Yet, the Carissa still had gold. It had gold at the surface, enormous parts of its shear zone (the structure that contains the gold) remained unmined and unexplored, and it also had high-grade gold intercepts at depth beneath the mine workings. The geology of this mine (and nearly all mines in the district) is such that the gold is focused in steeply plunging ore shoots in shear zones. These shoots don't normally just give out. Similar shoots in other greenstone belts in Australia and Canada have produced gold to depths of 5000 or more feet. The Carissa shaft was only 400 feet deep. So, how many millions of ounces did the State of Wyoming take away from its citizens by withdrawing this mine?

And then there are the gold-bearing shear zones in the Atlantic City-South Pass City- Miners Delight trends and also in the Lewiston trend. These trends contain numerous historical mines and prospects, but more than 95% of the structures have never been sampled! Who knows what gold mine awaits discovery along these trends.

And then there are the giant gold paleoplacers - where gold is found in giant alluvial fans and reworked fans that were eroded from the South Pass area, or from a giant, hidden lode adjacent to the paleoplacers. The USGS suggested that just one of these - the Dickie Springs-Oregon Buttes paleoplacer contained at least 28.5 million ounces of gold. Where did all of the gold come from? I'm pretty sure I know, but it remains unexplored and buried.


Another unforgettable field trip to South Pass. The1989 International Geological Congress field trip to the Wyoming Craton which included South Pass.The lady was the Minnesota State Geologist. I'm the good looking guy second from the right. The other three guys were Russian geologists - one was a KGB agent (for those of you who did not grow up during the cold war, this is the same as a Democrat) who kept all of the money and everything else for the other Russian members (yep, sounds like Obamacare). Anytime the Russian geologists needed money for coffee etc, they had to go to the KGB agent and beg for money. 

Another South Pass field trip - trucks as far as the camera can see (photo by Dave Miller, 2004)


2002 photo of another field trip to South Pass (photo by Dave Miller, 2002). I'm in the center talking about geology.


Field trip for gold panning


South Pass field trip


Field trip to Snowy Range, Wyoming


Paleoplacer gold from the Dickie Springs area (photo courtesy of J. David Love).

Gold-bearing fanglomerate at Dickie Springs south of South Pass.



Friday, June 1, 2012

The Carissa Gold Mine in the South Pass greenstone belt

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.



Mineralized terrains in Wyoming modified from Hausel (1997). The South Pass
greenstone belt lies in western Wyoming at the southern tip of the Wind River Mountains.
The initial gold discovery was in Strawberry Creek near the eastern edge of the greenstone belt.


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.
7.5 ounce nugget recently found in tributary of Rock Creek
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.
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.

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.


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.




Pit dug into gold-bearing
paleoplacer at Dickie Springs















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.

Gold from tailings
in Rock Creek.
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.




Gold-rich shear zone at the Carissa mine in the
South Pass Archean greenstone belt. Such shear
structures show distinct 'nugget effects' where
steeply plunging ore shoots are identified by
gold enrichment and/or fold closures. When found,
such ore shoots plunge steeply down into the earth
possibly for a few thousand or more feet. These
kind of ore shoots are common in greenstone belts
worldwide and are known as 'saddle reefs'.


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.
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.
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).


The Duncan mine. Another gold deposit
sits under this property, but it too is
being made into a govenment monument.
It sits on
private property but this did not stopped
the state of Wyoming to invest tax-payer
funds to rebuild this as a monument
to mining where no man can mine again.
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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Thursday, September 1, 2011

New GOLD BOOK tells you how and where to find GOLD

Available at Amazon. Gold - Field Guide for Prospectors and Geologists. How to identify gold and the other precious metals, where to find gold and what clues can lead you to gold.

Understanding geology can lead to incredible treasures. This book tells you in layman's terms about gold deposits in the Western US with emphasis on Wyoming. Written by two geologists - one found >100 gold deposits, mapped >dozen gold districts and even found a whole new district with similarities to the world-class gold camps of Red Lake, Canada and Cripple Creek, Colorado combined (Rattlesnake Hills) that was entirely overlooked by everyone else. This same individual was one of seven members on the Donlin Creek, Alaska gold discovery - a deposit with drilled and inferred resources of 39.5 million ounces worth >$75 billion in gold! Reported by the Canadian Northern Miner as one of the largest undeveloped gold deposits in the world and the largest undeveloped gold deposit in North America!

And for those who are interested in rock and mineral identification in Wyoming - we have a book for you! Published in 2009 and available at Amazon.


Several other books by are also available at Amazon and other outlets.




About Dan Hausel
Every year for 29 years, Hausel provided free public field trips to teach the public, rock hounds & prospectors about geology & gold & diamond prospecting methods. He presented >400 field trips and lectures & was recognized by several regional, national and international organizations for his contributions.
He was presented >100 honors & awards including the AAPG's President's Award, the Wyoming Geological Association's Distinguished Service Award, the National Rock hound and Lapidary Hall of Fame's Education Award, the PDAC's Thayer Lindsley Economic Geology Award for a Major International Gold Discovery, the IBC's Archimedes's Geoscience Award & was recognized as Distinguished Lecturer by the University of Wyoming and Laramie Lyceum. He was often in demand for talks on geology, gold, diamonds, colored gemstones & prospecting & brought international-recognition to the Wyoming Geological Survey following discoveries of dozens of mineral deposits, occurrences, and a new gold district. But in 2007, politics took their toll and he took early retirement and moved to Arizona taking on position of VP of Exploration of DiamonEx Ltd based out of Australia. After leaving DiamonEx, he now consults on projects for various mining companies and focuses on writing books and articles for the ICMJ Prospecting and Mining Journal. Those years of working with prospectors and conducting research were the best years of his life.

About Eric Hausel
Eric is following in his father's footsteps and now works for a geological resource company in Denver, Colorado. Eric graduated from the University of Wyoming with degrees in geology, physics, astronomy and astrophysics.

Saturday, November 21, 2009

Gold at South Pass Wyoming

Reconstructed head frame at the Carissa Mine at South Pass
(Photo taken during field trip in 2010). Possibly
one of the few good uses for the AML funds in Wyoming. AML
funds are used to reclaim old mines and bury shafts, yet not one
person has fallen down a shaft in Wyoming that we are aware of.
Hundreds of millions of dollars used only to bury prospects and
mines. This program should be investigated!
SUMMARY
Every year for 29 years, one geologist at the Wyoming Geological Survey (W. Dan Hausel) volunteered time to lead free field trips for the public and geological associations to teach them about geology & gold & diamond prospecting methods, gem-hunting and methods used to find new gold deposits. He was in high demand for talks to prospecting groups, mineralogical associations, business organizations and geology federations throughout the country.

In his office in Laramie at the University of Wyoming, he met with hundreds of visitors and prospectors and identified rocks and minerals for the general public and mining companies. Over the years, hundreds of books, documents and maps on geology were published and Hausel was presented national and international awards for research.


SOUTH PASS - LAND OF GOLD and IRON
Very little modern research was conducted at South Pass, until this geologist (Dan Hausel) mapped the greenstone belt and identified hundreds of gold anomalies and produced eight 1:24:000 scale maps of the geology and 1:48,000 scale summary geological map and several 1:120 and 1:240 geological maps of accessible underground mines.

The South Pass greenstone belt produced nearly all of the known historical gold in Wyoming, yet it remained mostly unmapped until the 1980s and early 1990s, when the entire greenstone belt and all accessible underground mines were mapped and hundreds of samples were collected for assay, geochemistry and mineralogical studies. .This resulted in several publications culminating with a report on the greenstone belt and its mining districts (Hausel, 1991). It was clear that considerable gold remained unmined and very little modern exploration was conducted in this region other than a few, piecemeal drilling and trenching studies due to the investigations by Hausel (1991).

Some mysteries that remained to be resolved was how extensive was the Carissa ore deposit,, which appears to have potential to be a multi-million ounce deposit, how extensive was the Miners Delight, Duncan, Diana, Tabor Grand, Wolf and other significant mines. Additionally, how much placer and eluvial gold have been missed by earlier prospectors. At least one diamond was reportedly found in this belt, thus was there potential for diamonds in this region?

Other problems that remain to be resolved include the sources of the giant Oregon Buttes and McGraw Flats paleoplacers. The Oregon Buttes paleoplacer appears to be  mostly eluvial with some reworking into modern placers at Dickie Springs.

The closure of areas by the State and Federal government based on very sketchy data is of great concern. In particular, the closure of the Willow Creek placer, which is likely a major gold deposit, is purportedly filled with mercury from a mysterious source. There are no known natural sources for mercury in this region, and the introduction of so much mercury by mankind is highly unlikely: the environmental data is likely flawed. This placer along with the significant gold mineralization at the Carissa mine was withdrawn by the State of Wyoming and should be made available to the taxpayers rather than kept in government holding.
While exploring the surface and underground workings at the Carissa mine along with drilling by mining companies, it was more than apparent that a major, untapped gold deposit remained. Evidence of commercial gold was found throughout the surface workings over a minimum of 1000 by 980 feet as well as to depths of 970 feet. BUT, the mineralization was open in every direction and undoubtedly continues hundreds of not thousands of feet below the mine workings.

Placer gold from Smith Gulch at South Pass - about 20 ounces recovered
in a week.
On the 350-foot level at the Carissa mine. Steve Gyorvary stands in mined out stope to provide scale of size of the primary shear (look for his mine lamp). All of the open space that Steve is standing in is the former gold-bearing shear structure that was mined out. This structure continues 350 feet to the surface; another 640 feet beneath this level (based on drilling) and likely a few thousand feet deeper.

It also continues along strike (trend) for a minimum of 1,000 feet and is enclosed in a envelope shear that is about 1,000 feet wide. This could have been one of the great gold deposits of Wyoming. But the Wyoming legislature supported its purchase by the state, withdrawal and placed the property within Wyoming's version of a Disneyland at the South Pass City historical site. One should ask why their taxes are being used to purchase economical gold mines and reconstructing historical facilities. This property could have been developed, mined and reclaimed then donated to the South Pass City historical site instead of taking the mine from the public as well as a major gold resource, jobs and a tax base.
For example, the primary shear structure has a average gold grade of 0.15 to 0.3 ounces per ton based on sampling, mining and drilling. For comparison, properties currently being mined in Nevada yield average ore grades of 0.03 to 0.15 ounces per ton. The Carissa shear has one of the highest average gold grades for a gold mine in North America. This primary shear is enclosed by a larger low-grade shear zone that is as much as 1000 feet wide and much of it is unexplored but it yielded gold values of 0.01 to 0.09 ounce per ton where it was sampled.
The development of the Carissa mine would have led to other exploration and likely development of other properties. Unlike other greenstone belts in Canada and Australia, the shear zones at South Pass remain relatively unexplored and it is estimated that only about 5% of the exposed shears have been sampled and tested for gold!

Steve Gyorvary poses on the 350 foot level
of the Carissa mine (photo by W. Dan
Hausel).
FIELD TRIP TO SOUTH PASS

In 2004, >100 prospectors, members of the general public, and 8 dogs (considered to be first class rock hounds) toured South Pass. For Hausel, this area has special meaning as he spent 5 field seasons living in a tent in South Pass in order to map the 450 mi2 granite-greenstone belt along with 3 dozen underground mines. While all other state employees received full per diem to cover food and lodging, the WGS allowed Hausel to use his personal tent and refunded the cost of groceries. The last two mapping seasons, he was provided a government tent.

Welcome to Atlantic City (population "About" 57). Photo
by Sharon Hausel.
South Pass was Wyoming’s principal gold district, and could potentially produce significant amounts of gold and iron ore again – not to mention the possibility of finding colored gemstones and diamonds. Both aquamarine and a diamond have been reportedly found in the district in the past.

Members of a South Pass field trip listen to Hausel discuss
 geology and mining history of the former Atlantic City iron
ore mine (photo by Sharon Hausel).
During mapping hundreds of gold anomalies and some iron ore resources were identified and/or discovered. The project resulted in the mapping and sampling of several gold-bearing structures that could potentially host some very large gold deposits – by far the best of these, based on sampling and mapping is the Carissa mine near South Pass City. The Carissa mine could easily represent a Million plus ounce gold deposit.

HISTORY
Folded banded iron formation from the Atlantic City
 iron ore mine. Imagine the tectonic forces needed
to deform this rock. If you were to use this rock and
rotate it 90 degrees on end, enlarge it hundreds of times,
 this is what present day South Pass would look like based
on mapping. So think of this as a small scale South Pass.
According to historical records, the first report of gold at South Pass was made on Strawberry Creek as early as 1842 by a trapper from the American Fur Company. Several years later (in 1855), a group of 40 prospectors entered South Pass to follow up on the discovery and reported gold nearly everywhere at South Pass. This expedition was followed by a group of 9 prospectors who returned to the area in 1858 and commenced mining on Strawberry Creek. The decayed remains of their sluices were later found in 1870.

In 1861, another expedition to South Pass included a group of 52 prospectors who began mining on Willow Creek, when they were attacked by Indians and driven out. Two years later (1863), gold was discovered on the Oregon Trail immediately south of South Pass in the vicinity of Oregon Buttes (Oregon Buttes was studied more than a century later by the US Geological Survey, and is now recognized as one of the largest undeveloped gold occurrences in North America - the source of the gold is thought by some to be the South Pass greenstone belt).
Oregon Buttes from South Pass includes a giant gold
paleoplacer and placer. The paleoplacer (the ridge in the
lighted area on the horizon below Oregon Buttes) was
suggested by the US Geological Survey to host >28.5 million
ounces of gold, making it one of the larger undeveloped gold
deposits in the US. The source of the gold for Oregon
Buttes has never been identified but in all probability lies at depth
beneath the sedimentary cover and eroded from the
greenstone belt hidden under those younger sedimentary
rocks. Drilling by Hecla Mining Company verified
the presence of the greenstone belt under the sedimentary rocks;
 and identified what may be a hidden, gold-bearing sulfide-rich
iron formation at depth.

In June 1867, the richest lode in the district was discovered that is currently known as the Carissa. These miners were attacked by Indians, three were killed and the rest were driven out, but returned later in late July. In the winter of that year, 400 ounces of gold were recovered from the lode using very primitive tools. Four 4 tons of ore were shipped to Springfield, Utah a short time later, which yielded an incredible 1,400 ounces of gold!

Because of the continual hostilities between the Whites and Indians, the US Army established Camp Stambaugh near the towns of Atlantic City and Miners Delight in 1870. However, many of the recruits deserted to search for gold.


View of the primary, high-grade gold-
bearing shear zone at the Carissa mine.
Note the geologist for scale.
The Carissa mine (see photo to left) was Wyoming’s principal gold mine & produced more than 180,000 ounces of gold (worth about $300 million at today's gold prices) based on incomplete production records. Missing production records over a period of several years suggest that the gold production could have been considerably more. Mapping by Hausel and drilling by various companies indicates that a sizable gold resource remains unmined. However, the mine was incorporated into the South Pass City historic site.

By 1872, 12 stamp mills were operating in the district. In 1878, the Army abandoned Camp Stambaugh, even so, the Oregon Trail had to be abandoned for a safer route to the south due to increased hostilities. South Pass continued to be a battle ground until 1882 following the signing of the Treaty of Five Nations.

In 1884, significant placer operations were proposed and the Granier ditch was constructed to haul water from Christina Lake (12 miles away) to South Pass. Start up of the hydraulic operation did not occur until 1890. In 1891, 6,720 ounces were recovered from the operation. Today, scattered and sporadic prospecting operations continue to produce minor amounts of gold. However, the South Pass district hosts significant hidden and exposed gold deposits – nearly all are unevaluated. For example, the shear zone structure at the Carissa Mine may host a very sizable gold deposit based on geology and sampling. The Carissa shear zone. The Carissa mine was developed into an intensely folded and faulted structure known as a shear zone. The primary shear structure containing high-grade gold is 1.5 to 80 feet wide. This high-grade ore shoot is enclosed in a major shear envelope that is as much as 1000 feet wide!!! This envelope is almost completely untested even though samples show potential for a major gold deposit! A 97-foot composite chip sample taken on the south side of the high-grade shear yielded 0.023 ounces per ton. Another 30-foot sample taken on the north side of the high-grade shear yielded 0.07 ounces per ton of gold! Thus the remainder of this envelope (about 850 to 900 feet) remains untested!.
Looking along reconstructed ore tram at the Carissa.


The Carissa ore deposit is structurally controlled and appears to represent a saddle reef deposit where high-grade gold is localized in fold closures and rehealed fractures similar to the Homestake mine. Thus geological evidence suggests that the Carissa ore body undoubtedly continues to great depths. Support for the presence of a major ore deposit includes drilling that tested the mineralized shear below the mine workings. Drilling by Consolidated McKinney Resources identified a highly anomalous zone that was up to 80 feet wide. Assays of drill core from this zone ranged from 0.03 to 2.54 ounces per ton gold (the shear envelop was not tested). This mineralized structure was intersected at depths up to 930 feet. Based on similar deposits in other greenstone terrains around the world, it is likely that the deposit continues to depths of 2,000 to 10,000 feet. In addition, Carissa Gold Inc. made the following reserve estimates on the property using an extraordinary high reserve cutoff grade. They reported 208,000 tons of ore that had an average grade of 0.343 ounces per ton and a geological reserve of 37,000 tons of ore averaging 0.85 ounces per ton!

Anaconda Minerals Company also drilled the property and all of their reported 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 ounces per ton gold at depths up to 700 feet. There are many unknowns about this mine, but it is clear that the Carissa is a viable exploration target for gold that could potentially host a very sizable, untapped gold deposit!

GREENSTONE BELT & GEOCHRONOLOGY
Schematic geological map of the South Pass greenstone belt
generalized from Hausel (1991).
The attendees of the field trip learned that South Pass is a fragment of a larger greenstone belt. Greenstone belts are found at a number of places worldwide including Canada, Australia, and Africa where a very large percentage of the world’s gold is produced.

The term greenstone belt is often considered to be synonymous with the phrase Gold Belt. This is because most greenstone belts are important sources for significant amounts of gold as well as other metals including iron and nickel, and gold anomalies have been detected over very large areas of the South Pass greenstone belt. In particular in a distinct belt running from South Pass City, through the Carissa mine, through Atlantic City and to the Miners Delight mine over a belt of more than 6 miles in length.
The Miners Delight headframe
At the Miners Delight mine a 3 to 16 foot wide shear zone was traced over 2500 feet on the surface. Gravels in Spring Gulch draining this shear zone produced 1500 ounces of gold including several 1 ounce, >2 ounce nuggets, a 6 oz nugget, and a sample of auriferous quartz described as “the size of a water bucket that was filled with gold”. Samples collected across the shear zone by Hausel ranged from 0.01 to 0.36 ounce per ton gold. A historic prospectus reported that there were 2,400 feet of drifts accessed from a 250 foot deep shaft and that the mine produced 60,000 ounces and that the gold tenor ranged from 0.3 to 110 ounces per ton of gold. Little is known about the mine.
View of the Duncan mine. Significant gold
 mineralization was detected in a distinct
 fold at this mine by Hausel. A 2.5
channel sample yielded 0.96 ounce per
 ton gold!
Several mines along this belt contain anomalous gold. The Duncan, Mary Ellen, Tabor Grand, St. Louis, and Diana are some of the better known mineralized properties and mines. Common specimens containing visible gold attest to their potential.

Visible gold in specimen from Mary Ellen Mine (courtesy of Steve
Gyorvary). Specimens containing visible gold are rare;
however on every field trip led by Hausel from 1985
to 2006, at least one person found a specimen with visible gold. It is
notable that shear zones produce 'nugget effects' where high-grade
gold is often encountered in ore shoots in shear zones that are restricted
in size along trend at the surface. But these shoots typically occur at
'saddle reefs' that steeply plunge into the earth for a few thousand feet
to as much as a mile or more. Such well formed ore shoot saddle reefs were
recognized at some mines in the South Pass greenstone belt, notably the
Carissa mine, which likely is a million ounce+ gold deposit - but more
work and drilling is necessary to confirm how deep the Carissa 'reef'
plunges. Based on drilling, very good gold mineralization was intersected
570 feet below the deepest mine level and there is no reason to suspect
that it does not continue deeper.

All of the drainages downstream from this belt have produced significant placer gold. Another parallel belt (about 4 miles in length) occurs in the Lewiston area. During geological mapping of the greenstone belt, Hausel also identified rock significant alteration that is characteristic of gold mineralization in the Crows Nest area between these two mineralized belts. In addition, the greenstone belt continues under rock to the northeast as well 6 miles to the south of South Pass City. It is notable that both of these regions are overlain by giant gold paleoplacers (McGraw Flats-Twin Creek to the north, and Oregon Buttes to the south) suggesting the presence of at least two major hidden gold deposits.

The rocks at South Pass are old! South Pass is an Archean (older than 2.5 billion years) greenstone belt. Gneiss in the early crystalline complex of the Wind River Mountains yields Rb-Sr dates of 2.8-3.8 Ga (billion years old), and granitic rocks of the Louis Lake Batholith (which intrude the greenstone belt) yield dates of 2.6 Ga. A Rb-Sr isochron for the Miners Delight Formation within the greenstone belt yielded a 2.8 Ga date. This latter age may represent a prograde metamorphic event, and the rocks could be older. One model lead date from the Snowbird vein at the Snowbird mine of 2.8 Ga, may suggest a temporal connection between metamorphism and mineralization.

STRATIGRAPHY OF THE GREENSTONE BELT
The Mary Ellen mine (about 1989)
Nearly everything that is known about the geology of the South Pass greenstone belt is due to the work of Hausel over a period of several years. Mapping showed that only a portion of the South Pass greenstone belt synform is preserved at the surface. Geophysical exploration and drilling by Hecla mining to the south supported that the greenstone belt continues under young sedimentary rocks to the south for at least 6 miles.

At the base of the South Pass synform (basin) gneiss referred to as an S-type gneiss complex, or the basement of South Pass, is interleaved with the Diamond Springs Formation, the oldest member of the South Pass greenstone belt. The Diamond Springs Formation consists primarily of primitive metamorphosed igneous rocks that include distinct peridotites with MgO contents ranging from 18 to 38%; chromium from 600-10,000 ppm (parts per million); and nickel from 160-2600 ppm. The CaO/Al2O3 ratios for these rocks are low (0.06-2.8) and they posses flat REE (rare earth element) patterns similar to komatiites. Thus these rocks are thought to represent primitive mafic and ultramafic basalts and komatiites (in other words, very high magnesium volcanic rocks).
Graded bedding in 2 billion year old meta-
graywacke at South Pass.
The Goldman Meadows Formation overlies the Diamond Springs Formation. These rocks include thick banded iron formations along with mica schists and quartzite. The average iron content for the iron formations is upwards to 40%, and a sizable resource is still present. In the past, US Steel Corporation operated a large open pit mine (Atlantic City mine) and recovered more than 90 million tons of iron ore prior to the closing of the mine in 1983. Even so, mapping suggests that at least 300 to 400 million tons of iron ore remain in place. The geology of the Goldman Meadows formation suggests that it was deposited in shallow water on a stable platform and was shed from a nearby shelf.

A 7.5 ounce nugget found in Rock Creek
gold placer at South Pass.
The Goldman Meadows Formation is overlain by the Roundtop Mountain Greenstone. The Roundtop Mountain Greenstone consists primarily of thoeiitic oceanic basalts that in places have well preserved pillow structures. One of the more popular stops on the South Pass field trips is overlooking the iron ore mine where some excellent pillow basalts are preserved under the power line.
The Roundtop Mountain Greenstone is overlain by the Miners Delight Formation, which is estimated to be 5,000 to 20,000 feet thick. Determination of the thickness of this unit is complicated because the entire belt has been intricately folded and faulted almost like an accordion. This formation consists primarily of metagraywacke that contains a trace to 0.051 ppm Au (gold) (compared to average of 0.002 ppm). Essentially all of the rock units at South Pass exhibit above average gold content and are interpreted to have been deposited in a moderately deep oceanic basin. However, the spatial association of proximal facies metagraywacke with meta-andesites near Miners Delight suggests that there was also a contribution from an Archean age island arc. Portions of the South Pass greenstone belt are overlain by Tertiary age, gold-bearing conglomerates in the Wasatch, White River, Arikaree, and South Pass Formations. It is obvious that South Pass is highly anomalous in gold!

GOLD GEOCHEMISTRY

One of dozens of gold-bearing samples found at the Carissa
mine during field trips from the early 1980s until 2005. This sample
is a rehealed breccia with vugs (open spaces). All of the open spaces are
 filled with wire gold and closely associated with quartz.
Note the foot print on the blue cloth.
The gold geochemistry was studied by the US Geological Survey. The Au/Ag ratios are high & Au/Cu ratios are low for some of the gold at South Pass. The trace metal contents (Bi, Pb, As, Sb, V, Mo, W, B, Nb, Zn, Cr, Co, Ni) are typical of hypothermal veins in other greenstones worldwide. Stable isotopes and fluid inclusion studies support that the South Pass gold is similar to that of a hypothermal vein system. The carbon and oxygen isotopes in shear zones along with hydrogen isotopes from fluid inclusions support that the much of the gold solutions were derived from the dewatering of the Mineral Delight Formation during compaction.

Structurally, the major gold systems at South Pass are located adjacent to a distinct group of metagabbos, metatholeiites, and actinolite schists (metakomatiites) that trend from South Pass City to Miners Delight. The localization of gold in this region is believed to be due to competency contrasts between the metagabbros and adjacent Miners Delight metagraywackes. During folding, it is thought that these were favorable for the development of numerous fractures and faults. Much of the ore is found in these shear structures contain enriched ore shoots developed in folds suggestive of a reef-type structural control. Placers downstream from the shear structures are highly enriched in gold.

PLACERS
Gold from dredge tailings on Rock Creek from Gerald Stout
(photo by Hausel). It is interesting to note that the last dredge
that operated in Rock Creek terminated operations
because of world war II, not because they ran out of gold.
If the placer was commercial at $35/ounce of gold - one
would anticipate that it is still commercial at $1900/ounce.
And what about the parallel Willow Creek that drains
off of the Carissa mine to the south of Rock Creek?
It has much less gravel, but possibly is much richer in gold.
It remains unmined due to state withdrawal. Based on today's gold
price, the Rock Creek placer produced more than $115 million.
Some of the placers at South Pass contain significant coarse gold. For example, XL Dredging mined portions of Big Atlantic Gulch about 1910 and recovered nuggets weighing 0.07 to 1 ounce. The ET Fisher Company dredged Rock Creek from 1933 to 1941 and produced 11,000 to 30,000 ounces: 75% of the gold was found within 3 feet of bedrock. Some of the gold was coarse and several nuggets were recovered. Nuggets recovered from Rock Creek include many small nuggets and some large nuggets.

Boulders containing as much as 630 ounces of gold were also reported in the historical record. Much of this coarse gold was found during dredging of various drainages.

PALEOPLACERS
           
A 34 ounce gold nugget from Rock Creek!
Gold paleoplacers (old dry placers) cover large areas at South Pass. The paleoplacers have been studied primarily by the US Geological Survey. These are found within and on the edge of the greenstone belt. For example, one paleoplacer sits immediately south of Atlantic City in the South Pass Formation. This gold-bearing paleoplacer remains unevaluated.

At Oregon Buttes, the Wasatch Formation conglomerates are estimated to be 1300 feet thick and cover 8 mi2 and to host a major gold resource estimated to be as high as 28.5 million ounces (US$30 billion). Some gold-bearing oil well cuttings were recovered from depths of 6500-7000 feet just 0.5 mile north of the Continental Fault adjacent (north) of Oregon Buttes indicating the presence of a buried auriferous shear zone at that location. Geophysical exploration in this area by Hecla Mining Company identified what appears to be a iron formation (at depth). Hecla interpreted this to be a gold-bearing iron formation. The paleoplacers at Oregon Buttes have been reworked producing some enriched dry placers.

SUMMARY
All of the field trip attendees had a good time in the sun and learned about the mining history and methods used to find gold. Many of them also became aware of the tremendous gold potential of this district and the possibilities that some mines and some high-paying jobs could result from exploration and development in this region. One should note that this district is still only in its infancy for exploration and it is estimated that only about 5 to 10% of the shear structures have been sampled. This means that dozens of rich ore shoots are likely hidden under a few inches to a few feet of dirt and eluvium.

Hausel (right) speaks of the potential for significant gold deposits at the
 Carissa mine shear zone. Based on sampling, mapping, and
drilling, the Carissa property is probably one of the better gold targets
in Wyoming and potentially in the West. Hausel is the author of more
 than 50 professional papers, books and maps on South Pass.

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RECOMMENDED READINGHausel, W.D., 1989, The geology of Wyoming's precious metal lode and 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.
One of hundreds of gold mines and prospects at South Pass
that yielded several significant gold anomalies.
Hausel, W.D., 1993, Mining history and geology of some of Wyoming's metal and gemstone districts: Wyoming Geological Association Jubilee Anniversary Field Conference Guidebook, p. 39-63.
• Hausel, W.D., and Hull, J., 1990, Guide to gold mineralization and Archean geology of the South Pass greenstone belt, Wind River Range, Wyoming, in Roberts, S., Geologic field trips to western Wyoming: Geological Survey of Wyoming Public Information 29, p. 178-191.
• Hausel, W.D., 1994, Mining history of Wyoming's gold, copper, iron, and diamond districts: Mining History Association 1994 Annual, Reno, Nevada, p. 27-44.
• 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.
• Hausel, W.D., and Love, J.D., 1991, Guide to the geology and mineralization of the South Pass area: Wyoming State Geological Survey Reprint 49, 20 p.
• Snyder, G.L., Hausel, W.D., Klein, T.L., Houston, R.S., and Graff, P.J., 1989, Precambrian rocks and mineralization, Wyoming Province: 28th International Geological Congress guide to field trip T-332, July 19-25, 48 p.

Also, see our websites at: GOLD
at GEMSTONES
and at GEOLOGY
Gold in Arizona
Gold in Alaska
Gold in California
Mountain of Gold

GOLD - Geology, Prospecting & Exploration

Available at Amazon and CREATESPACE. Gold - Field Guide for Prospectors and Geologists. How to identify gold and the other precious metals, where to find gold and what clues can lead you to gold.


Understanding geology can lead to incredible treasures that others miss. This book tells you in layman's terms about gold deposits in the Western US with emphasis on Wyoming. Written by two geologists - one who found >100 gold deposits, mapped >dozen gold districts and even found a whole new district with similarities to the world-class gold camps of Red Lake, Canada and Cripple Creek, Colorado combined (Rattlesnake Hills) that was entirely overlooked by everyone else.


Also, one of 7 members on the Donlin Creek, Alaska gold discovery - a deposit with drilled and inferred resources of 39.5 million ounces worth >$75 billion in gold! Reported by the Canadian Northern Miner as one of the largest undeveloped gold deposits in the world and the largest undeveloped gold deposit in North America! 


And for those who are interested in rock and mineral identification in Wyoming - we have a book for you! Published in 2009 and available at Amazon.


Several other books by Hausel are also available at Amazon and other outlets.