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Gold Quarry - Mineralisation |
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Nevada, USA |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Gold Quarry mine is located some 11 km to the north-west of the town of Carlin in Eureka County, north-eastern Nevada, USA. It lies on the Carlin Trend of deposits and is part of the Carlin operations of Newmont.
Continued from the Gold Quarry Geology record
Mineralisation
The Gold Quarry ore deposit is constrained by the Gold Quarry Fault system to the north-west and by the parallel Challenger Fault System to the south-east. As such it is elongated parallel to these faults, and as a consequence to the regional Humboldt Lineament which occurs immediately to the south. This elongation however, is roughly normal to that of the Carlin Trend within which it falls (Rota, 1993; Wright, 1993).
Economic mineralisation at Gold Quarry is located within i). the upper 90 m of the Devonian carbonate section, mainly the autochthonous Un-named (Popovich equivalent) Devonian Limestone; ii). an overlying 300m thick sequence of para-allochthonous Devonian siltstone, shale, sandstone, silty limestone and chert of the Rodeo Creek Unit; and iii). up to 90 m of allochthonous Ordovician siliceous mudstone, chert and interbedded siltstone and shale of the Vinini Formation. The highest local concentrations of gold are found within coarser siltstones, highly fractured siltstone and de-calcified silty limestones (Rota, 1991). The vertical extent of the ore is of the order of 675 m (Andrew, 1993).
Extensive drilling undertaken from 1986 to 1990 revealed that the Gold Quarry deposit could be divided into two distinct ore zones, the Main and the Deep West. The Maggie Creek Mine was developed on the upper extension of the Deep West ore zone, localised in steeper structures, and was separated from the shallower dipping Deep West by a thinned neck of lower grade mineralisation (Rota, 1991).
The main ore zones at Gold Quarry are:
Main Orebody - The principal host to the Main Orebody at Gold Quarry is a 335 m thick assemblage of silici-clastics, the Rodeo Creek Unit (Rota, 1991). Structural preparation by high angle normal faults and fracturing along both the north-easterly trending Gold Quarry Fault and the north-westerly striking Good Hope Faults was very important in ore location. The ore zone is located in the hangingwall of both faults where the Rodeo Creek Unit has been strongly fractured (Heitt, etal., 1991). Tabular to irregular high grade ore shoots are controlled by NNW trending fault systems (Rota, 1991 & 1993). North-east structural intersections usually host significant ore pods (Rota, 1991 & 1993). The high grade zones are connected, or enveloped by overlapping lower grade zones. The distribution of gold is controlled by structural stockworks at all scales, from preferential localisation along faults up to 5 m wide, to micro-fractures 50 mm apart. From these micro-fractures gold is disseminated outwards into the siltstone matrix. The average grade of this ore zone is approximately 1 g/t Au (Rota, 1991).
The Main orebody generally strikes north-east and dips at 45 to 50°SE. Mineralisation is continuous over a strike length of 2000 m. Until 1991 the majority of the ore mined had been from the oxidised portion of this orebody (Rota, 1991).
Deep West Orebody - This is a highly silicified, stratabound, silica replacement zone averaging around 75 m in thickness, which has been traced over a strike length of 750 m. It strikes at 20° and dips at 30 to 35°SE. The average grade is more than twice that of the Main Orebody. Mineralisation follows the structural contact, formed by the Chukar Gulch Thrust, between the Devonian carbonate units and the overlying silici-clastics of the Rodeo Creek Unit. Sediments within this thrust have been extensively shattered and milled (Rota, 1991). Deep ores below the zone of oxidation are carbonaceous and pyritic (Christensen, 1989).
Gold barren thin bedded grey limestone immediately below the Deep West ore are interpreted as belonging to the middle Roberts Mountains Formation. Mineralisation is hosted by the lower Quarry Member siltstone and continues through the underlying James Creek Member, both of the Rodeo Creek Unit, the full thickness of the Un-named (Popovich equivalent) Devonian limestones and gradually declines in the upper portions of the Roberts Mountains Formation (Rota, 1991). Both the upper and lower limits of ore grade mineralisation are marked by abrupt grade boundaries (Christensen, 1989).
The intensity of alteration is sufficient to obscure the contact between the siliceous and carbonate rocks. Carbonate host lithologies have been extensively de-calcified in the lower portions of the ore zone, which may have originally contained 5 to 10% carbonate. The ore was apparently preferentially concentrated in de-calcified silty limestone. Alteration in the Deep West has also however obscured the original nature of the host lithologies. Gold mineralisation within the Deep West can be characterised as more passively introduced and more continuous than the Main orebody (Rota, 1991; Rota, pers. comm., 1993).
Maggie Creek Deposit - This deposit comprises the upper extension of the Deep West Orebody in the west and south-west portions of the Gold Quarry open pit. The two are only continuous at depth to the east. Mineralisation also continues to the south of Maggie Creek, along the Gold Quarry/Les Fault system into a geologic setting similar to that at the Main Orebody, although on a smaller scale. This is known as the MC Leach deposit (Ekburg, etal., 1990).
Mineralisation is hosted by highly argillised and locally silicified, de-calcified silty limestone, siltstone and massive limestone of the James Creek Member of the Rodeo Creek Unit. High angle faults synthetic to the Gold Quarry Fault system serve as the main controlling structures. These structures intersect the underlying, flatter Chukar Gulch Thrust of the Deep West Orebody (Ekburg, etal., 1990).
The deposit can be divided into two distinct ore zones. Ore in the northern section is hosted by argillised siltstone, chert and shale of the transitional sequence, while to the south it is within a highly argillised and silicified, thin bedded silty limestone. Bedding generally strikes at 40° and dips to the south-east at 20° to 80°. Both orebodies are hosted by the north-east striking high angle faults which are interpreted to be south-westward 'horsetail' continuations of the Gold Quarry Fault system (Ekburg, etal., 1990).
Decalcification was the most extensive and characteristic alteration style at Maggie Creek. The central section of the ore zone showed a funnel shaped calcite low. Argillisation was more extensively developed than in the other mines of the Carlin Trend, with much of the deposit containing between 10 and 55% clays, mainly illite. In general the higher concentrations of illite are associated with higher quantities of gold. Kaolinite, montmorillonite and alunite are present locally. Silicification, the major alteration product in the Main orebody at Gold Quarry, becomes progressively less prominent in the Maggie Creek orebody to the west. However silicification, while less intense, is still an important alteration feature. Further west in the Maggie Creek West pit, argillisation was the dominant alteration (MacFarlane, 1987).
Gold occurs as very fine particles of native gold disseminated throughout the rock. Gold from the oxidised ore zones has been reported to occur in the 2µm to 200µm size range, significantly bigger than at Carlin (MacFarlane, 1987).
The Maggie Creek ore was mined from a larger north-south elongated Main pit to the east that had final dimensions of 450 x 750 m and was 100m deep (Ekburg, etal., 1990). The smaller West pit to the south and west was approximately 200 m in diameter (Ekburg, etal., 1990).
The north-east trending Deep Sulphide Feeder structural system is interpreted to be the primary feeder conduit for both the Main and the Deep West orebodies. The Deep Feeder system is a steeply dipping breccia 'pipe' formed at the intersection of the north-east striking Challenger/Grey Faults and the north-west trending Hangfire Fault. This zone of mineralisation passes into the 320° Hangfire Fault from its intersection with the Deep Sulphide Feeder, and to both the shallow north-east trending Chukar Gulch Thrust and the intersecting 350° striking Kristalle faults (Rota, 1991 & 1993; Heitt, etal., 1991).
These faults control the distribution of the higher grade, milling ore shoots which are enveloped by the lower grade leach ore. Within the mill grade shoots there are some thin high grade pods developed along faults which carry from 30 to 60 g/t Au. One such pod in the Maggie Creek orebody had dimensions of 75 x 15 x 25 m with an average grade of 12 g/t Au and was responsible for 1.4 t Au. This shoot was rootless, but was on a fault which intersected the underlying Chukar Gulch Thrust (Rota, pers. comm., 1993).
Gold ore at Gold Quarry consists of minute (<1 mm diameter) particles of native gold finely disseminated within the host rocks, with a lesser amount on fracture surfaces (Rota, 1991). Silicification and pyrite typically accompany higher grade ore zones. The silicified hosts are generally strongly fractured, with spacings visible in outcrop of 1 cm or less in several different directions. In places these strongly fractured zones are brecciated with clasts varying from 1 to 100 mm. Microscopic studies have revealed that fracturing is accompanied by micro-fracture quartz-stock-works throughout the ore zone with fracturing as close as 50 mm spacing. Several generations of fracturing are recognised. Some are early and have been annealed, while others are late stage and post-ore (Rota, 1991; Rota, pers. comm., 1993).
Extensive hydrocarbon rich zones are spatially associated with the gold deposits below the zone of surface weathering and oxidation. Organic carbon and sulphides (typically pyrite) occur in concentrations of 1 to 2% within the un-oxidised zones, although more strongly pyritic zones are recorded. Rota, (1991) stated that detailed studies of un-oxidised ore determined that over 68% of the gold in the Deep West ore can be sub-microscopically associated with iron sulphides. However Rota (pers. comm., 1993) advised that all gold was associated with pyrite. Auriferous pyrite typically occurs as fine anhedral grains of less than 30 mm in diameter. Euhedral grains apparently do not contain significant gold, irrespective of grain size. The anhedral pyrite grains may contain over 100 ppm Au and 1 to 6% As (Rota, 1993). The gold occurs in high arsenic rims to the fine pyrite. Some of the more pyritic sections of the ore zone contain 'thousands of ppm' As. However it must be noted that the Au content is not directly proportional to the pyrite content, as a number of varieties of pyrite are present and not all have associated gold. Pyrite types include clasts within the sediments, coarser diagenetic, generally euhedral grains and aggregates, and as very fine disseminations and aggregates, including anhedral grains. Only the latter, which are typically sooty, generally have associated gold (Rota, 1991; Rota, pers. comm., 1993). Two stages of pyrite overgrowth are noted in the Deep West ore zone while none have been recorded in the Main Ore Zone. Coarse grained diagenetic pyrite cubes were found to contain colloidal gold particles. It has been suggested that surficial oxidation may have released gold particles, resulting in a weak supergene enrichment of gold in hematite stained clays at the top of the deposit (Rota, 1993).
Un-oxidised ores at Gold Quarry are defined as those ores that have not been subjected to either late hydrothermal oxidation or supergene weathering and which contain >0.5% organic hydrocarbons and/or base metals. This material is highly refractory to conventional cyanide treatment, and due to the presence of 'active hydrocarbons' are capable of removing more gold from cyanide solution than that solution can liberate by direct cyanidation, This requires neutralisation by an oxidising process such as roasting or chlorinisation (Rota, 1991).
Un-oxidised material has two sub-classifications, i). silica-sulphide, and ii). carbon-sulphide, based on their major mineralogical components. Refractory conditions may be due to gold locked in either silica or pyrite, and/or by contamination from activated hydrocarbons. The 'activated' hydrocarbons are interpreted as originating in the underlying sequences and to have been thermally maturated in the 250 to 300°C range. Textural relationships indicate that the hydrocarbons were introduced into the host sequence from outside, but were present prior to the arrival of silica and gold. The subsequent multi-stage pulses of hydrothermal activity brought in silica and additional pyrite in association with gold. Chemical interaction between these hydrothermal fluids and the activated hydrocarbons of the pre-existing reservoirs within the structurally prepared host rocks may have been in part responsible for the deposition of gold. Remobilisation of some carbon along feeder faults during main-stage gold deposition is regarded as having led to the higher grade shoots along these structures. These shoots contain high gold/silica/pyrite and low organic carbon. They are the silica-sulphide refractory ores. In these highly siliceous and pyritic ores carbon is generally lower or absent, but envelopes them on their margins. This also implies that the carbon preceded the introduction of silica, but was over-printed, remobilised and expelled by the silicification and deposition of additional sulphides. Similarly the upper levels of the deposit became enriched as remobilised carbon was concentrated and redeposited to form the carbon-sulphide refractory ore (Rota, 1991 & 1993; Rota, pers. comm., 1993). Oxidation of the near surface carbonaceous portions of Gold Quarry occurred as a result of late stage acid leaching and surficial weathering (Rota, 1991). This oxidation removed carbon and pyrite leaving non-refractory ore to the base of oxidation.
Some placer mineralisation is treated from the lower sections of the Tertiary Carlin Formation sediments adjacent to the mine (Rota, pers. comm., 1993).
The distribution of elements within and adjacent to the ore zones is as follows:
Arsenic - is one of the better geochemical indicators of gold at Gold Quarry, reflecting the body with a slightly larger halo than gold itself. The arsenic distribution is apparently controlled by the same structures and lithologies as the gold. Locally values of 300 ppm As were found at the surface. Arsenic bearing minerals found in the pit are arsenopyrite, orpiment and realgar (Rota, 1991).
Antimony - elevated antimony values are concentrated above the arsenic anomaly, mostly near and extending to the surface. Peak values of >500 ppm were irregularly clustered above the Deep West orebody and within the surface jasperoid. The antimony minerals found in the mine are stibnite and stibiconite (Rota, 1991).
Copper - is sparsely distributed throughout the deposit, often as irregular, structurally controlled zones of 100 to 500 ppm Cu. Erratic small patches of 1000 ppm Cu are reported. Local supergene coatings of malachite and azurite have been identified on fracture surfaces, while a weak supergene enrichment "blanket" averaging 175 ppm Cu is suggested near the base of oxidation (Rota, 1991).
Gold - levels within the surface jasperoid averaged 100 ppb, with peak values of 1 to 2 ppm in the discovery outcrop which was several hundred metres from the orebody. Gold was found to be the best geochemical pathfinder. In general, sampling of soil, outcrop and stream sediments all provided surface indications of the mineralisation (Rota, 1991; Rota, pers. comm., 1993).
Lead - lead-antimony oxides are found in the upper levels of the system, with values of >100 ppm being common. A galena vein in the upper parts of the orebody assayed 3000 ppm Ag. Lead decreases with depth to minor values only. Minerals detected include galena, cerussite, bindheimite, monimolite, plumbogummite and mimetite (Rota, 1991).
Mercury - values average between 1 and 3 ppm throughout the deposit, ranging as high as 200 ppm Hg in the Gold Quarry discovery jasperoid area. Distribution within the deposit is irregular, with the highest values occurring within major fault zones. No mercury minerals have been identified (Rota, 1991).
Nickel - is widespread throughout the lower portions of the deposit. In particular the Deep West Orebody is underlain by an anomaly that ranges up to 0.5% Ni within the upper 30 m of the carbonates (Heitt, etal., 1990; Rota, 1991).
Silver - is present in anomalous amounts within the Gold Quarry orebody, but is associated with the Zn-Pb-Cu-Ni mineralisation and has a different distribution to that of the Au. Values of 0.3 to 3.5 g/t Ag accompany the high grade gold ore zones. The mill grade ore appears to have an Au:Ag ratio of 1:2, while the leach ore has 3:1. Limited data suggests that the Ag precedes the introduction of gold. No silver minerals have been identified, although high values occur in rare galena veins (Rota, 1987; Rota, 1991; Rota, pers. comm., 1993).
Thallium - concentrations are generally lower than at Carlin, with up to 3 ppm having been found in the pit. No thallium bearing minerals have been identified (Rota, 1991).
Zinc - the quantity of sphalerite within the pit increases and becomes more pervasive with depth. Zinc concentrations are generally low in the Main Orebody, usually no more than 200 to 300 ppm. Anomalous zinc values are associated with carbonate lithologies within and below the Deep West Orebody and may be weakly related to gold deposition. The highest values are at the base of the Deep West Orebody, below the Chukar Gulch Thrust, where levels of around 0.5% Zn are recorded, with peaks of up to 4% (Rota, 1991; Rota, pers. comm., 1993).
Elements directly associated with gold mineralisation at Gold Quarry are arsenic, antimony and mercury. Their distribution often parallels the gold ore zones, with local concentrations along structures. A second trace element pattern of silver, lead, zinc, copper and nickel also occurs within the Gold Quarry deposit. Distribution of the latter is widespread and not directly correlatable with gold. It has been suggested that there were two events of metal introduction, i). an earlier Ag-Pb-Zn-Cu-Ni phase, followed and overprinted by ii). a multi-pulse Au-As-Sb-Hg event which has a different pattern of distribution (Rota, 1991; Rota, pers. comm., 1993).
The oldest mineralised event in the sub-district is the stratabound Ba-Pb-Zn-Ag enrichments of regional extent within lower to middle Palaeozoic sediments of the Western Assemblage. These base metal occurrences are developed within lower-Middle Ordovician quartz and chert sandstones, sand sized bio-clastic carbonates, sand-sized phosphates, limestone clast conglomerates, black graptolite rich shales and bedded cherts, and in lower Silurian black, white and brightly coloured cherts. Intersections of up to 12 m containing up to 4% Pb, 1% Zn and 12 g/t Ag having been intersected elsewhere in north-eastern Nevada (Ketner, 1990). This mineralisation is accompanied by silicification, dolomitisation and sulphidation with fluid inclusion studies suggesting a formation temperature of 250 to 210°C (Rota, 1993).
The first hydrothermal event, that associated with the Ag-Pb-Zn-Cu-Ni suite of elements, may have been either during the Palaeozoic, or the early to middle Cretaceous, associated with the 140 to 110 Ma Laramide intrusives mapped within the district. The second, or gold bearing phase, was most likely of Tertiary age, between 40 and 36 Ma. The latter is based on the presence of a 43 to 34 Ma volcanic/intrusive event in the district and age dating of post ore alunite alteration at 30 to 27 Ma. Fluid inclusion data suggests a temperature of 210 to 150°C for the introduction of Au (Rota, 1991; Rota, pers. comm., 1993).
Alteration
The intensity and distribution of alteration indicate a large hydrothermal system was spatially associated with the gold deposit at Gold Quarry. The principal wallrock alteration processes that have been recognised, from earliest to latest, are:
Decalcification (or de-carbonatisation) - the removal of carbonate minerals from limestone through hydrothermal processes was apparently the first alteration event to have occurred and may have predated the gold mineralisation. Although no calcite can be found within the siliceous sediments at Gold Quarry, replacement textures indicate an original carbonate content of the siliceous host that may have been as high as 10 to 15%. This process leads to a decrease in bulk density and an increase in both porosity and permeability. Evidence for decalcification is seen in the Maggie Creek Mine where abundant large calcite veins occur within fresh silty limestones, located directly up-dip from highly altered host beds of the Deep West orebody. More recent evidence of extensive de-calcification has been the discovery of fragment supported collapse breccias exposed in the open-pit on the southern end of the Carlin Window (Rota, 1991 & 1993).
The main zones of de-calcification have apparently been within the lower levels of the mine in the Deep West Orebody. As indicated earlier, it has been suggested that de-calcification has been a mechanism for producing vertically vectored fracturing in the Main Orebody in response to collapse and shrinkage of host lithologies in the (lower) Deep West ore zone. Possible sources of acid to produce this decalcification are i). prograde expansion of the hydrothermal system, and/or ii). magmatic contributions to, or thermal degradation of organics in the host lithologies (Rota, 1993).
Silicification - quartz is the most abundant alteration mineral and the most common vein type at Gold Quarry (Ekburg, etal., 1990; Rota, 1991). It accounts for up to 70% of the composition of the hosts in the orebody (from Andrew, 1993). Consequently, silicification is the most pervasive style of alteration associated with the deposit and has been superimposed on all lithologies. The degree of silicification is proportional to the bulk density and resistivity of the rock. Multi-episodic veining and breccia stages of silica flooding have produced a wide variation in the degree of secondary silicification, occurring as i). replacement of fine grained silt matrix; ii). overgrowths on detrital quartz grains; iii). veinlets <1 mm thick; iv). veins; v). sub-rounded fragments in hydrothermal breccias; vi). replacement of barite in hydrothermal breccia matrix; and vii). as late supergene, fibrous chalcedony in breccia matrix. Studies have shown however that there is a lack of multiple banded, crustiform veins. Multiple-stage breccia events, including fluidised textures with both clast and matrix supported breccias were observed in all gold bearing samples. Precipitation of quartz by rapid cooling/quenching and fluid mixing is said to be supported by the observation of fine quartz crystals coating siltstone breccia fragments, followed by the deposition of coarsely crystalline quartz, and then by barite crystal growth (Ekburg, etal., 1990; Rota, 1991 & 1993).
The majority of the gold in the deposit is associated with slightly to highly silicified rock. The upper portions of the orebody are more silicified, with the quartz content falling off with depth to an argillised acid-sulphate (alunite rich) core before passing down into the very highly silicified Deep West Orebody (Rota, 1993).
Alunite formation - the formation of hypogene alunite veins shortly followed the main stage of silicification and gold deposition and was closely associated with advanced argillisation. As such this phase is late stage hydrothermal and may be related to descending fluids resulting from mixing with meteoric/surface waters. "Acid-sulphate" alunite development takes the form of cross-cutting, coarsely crystalline alunite veins and breccia fillings to depths of over 300 m. A second phase of alunite formation probably occurred during the late surficial oxidation of the deposit. An amorphous mixture of alunite±kaolinite±silica was deposited along open fractures and joints, and as "replacement" pods. In both cases deposition appears to have been from descending waters. These and other coarse white, earthy upper level veins may be supergene in origin, while fine grained, pink, compact veins in the un-oxidised lower levels of the deposit are probably hypogene. These pink veins are a mixture of hematite and alunite. Alunite veins range in thickness from <1 to 150 mm (Heitt, etal., 1990; Rota, 1991 & 1993). Alunite accounts for up to 10% of sections of the orebody (from Andrew, 1993).
The majority of the alunite is concentrated in the central core of the deposit, between the upper silicified section of the Main Ore zone and the highly siliceous Deep West Orebody. No minerals were found replacing alunite and it was apparently the last mineral precipitated in the un-oxidised zone. Age dating of alunite returns values of 27 to 30 Ma, from samples taken at a depth of 1500 m, placing a probable latest date on the mineralisation. Associated kaolinite tends to occur more deeply than alunite within the core zone. Footwall limestones do not contain alunite.
Argillic alteration - accompanied alunite formation and may have continued late in the hydrothermal sequence, beyond the precipitation of alunite. Advanced argillisation, mainly occurring as illite and kaolinite, does not appear to be directly related to gold deposition. However euhedral pyrite occurs within veins of alunite and kaolinite. Clay alteration minerals near the top of the deposit consist predominantly of illite and kaolinite with traces of montmorillonite. Both the kaolinite and illite are found as white to iron-stained red clay veinlets and fracture coatings. Clay alteration fronts have been observed to penetrate 2 to 3 cm's into silicified rocks from post-silicification fractures, leaving a core of siliceous rocks surrounded by a clay rind. Clay within deeper parts of the deposit is mainly kaolinite. The vertical zonation of illite implies that it is hypogene at Gold Quarry, accentuated by near-surface acid-leaching and took place under highly acid conditions (Rota, 1991 & 1993).
Barite - is a common gangue mineral at Gold Quarry, occurring throughout the deposit and in peripheral jasperoids. Textural evidence suggests that the barite formed as a crystal mush in open space breccias of the Kristalle Fault system and was later re-brecciated.
Oxidation and acid leaching - oxidation and acid leaching are very pervasive in the upper sections of the deposit, and in part over-prints the hypogene alteration. This phase represents the final stage of development of the ore system, probably related to both late stage hypogene hydrothermal and to supergene weathering processes. Discrimination of the two styles is difficult. Extensive deposits of hematite in the upper levels and in feeder structures is taken as evidence of a hydrothermal origin (as hematite is unstable below 55°C). The effects of oxidation generally decrease at depths of between 120 and 180 m below the Palaeozoic to Tertiary unconformity, although they have been noted at depths of more than 465 m. The average depth of surface oxidation is of the order of 180 m. The base of oxidation follows the Deep West Orebody down, being shallower in the footwall Roberts Mountains Formation and in the Main Orebody (Rota, pers. comm., 1993).
Deep weathering, is indicated by pyrite moulds in siliceous rocks, lateritic soils and the abundance of limonitic clays on nearly all open fractures in the near surface zone. Oxidation fronts are commonly restricted by quartz and quartz-alunite veinlets and by silicified zones. Un-oxidised pyrite is frequently found in remnant cherts and highly silicified zones within near surface oxidised sections of the sequence (Heitt, etal., 1990; Rota, 1991 & 1993).
Rota (1991) suggests that advanced argillic alteration may have produced oxidised areas of wallrock during the waning stages of hydrothermal activity. He suggests that as hydrothermal fluids cooled and various minerals were precipitated, the solutions became more acid, thus encouraging the development of clays. Supergene weathering by oxygenated waters acting on the pyritic and marcasite bearing host rocks produced additional acid, promoting the formation of clays, weathering and oxidation.
The most recent source geological information used to prepare this decription was dated: 1996.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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McFarlane D N 1987 - Maggie Creek deposit: in Johnson J L (Ed.), 1987 Bulk Mineable Precious Metal Deposits of the Western United States - Guidebook for Field Trips Geol. Soc. Nevada pp 274-275
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Rota C R, 1988 - The Gold Quarry Mine: History and general geology: in Schafer R W, Cooper J J, Vikre P G (Eds), 1988 Bulk Mineable Precious Metal Deposits of the Western United States Geol Soc of Nevada, Reno, pp 49-56
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Rota J C 1987 - The Gold Quarry deposit: in Johnson J L (Ed.), 1987 Bulk Mineable Precious Metal Deposits of the Western United States - Guidebook for Field Trips Geol. Soc. Nevada pp 271-273
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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