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Twin Creeks - Rabbit Creek |
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Nevada, USA |
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Super Porphyry Cu and Au
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The Twin Creeks operation consists of two separate mining areas, the former Rabbit Creek and Chimney Creek properties, located some 70 km to the north-east of Winnemucca in the NE-SW aligned Getchell trend. They are located on the eastern flank of the Osgood Mountains, ~10 km east of the Getchell deposit, with the Pinson and Preble deposits further to the SW. Chimney Creek to the north, includes the Vista and Discovery pits, whilst the Rabbit Creek and satellite Sage deposits to the south are mined from a large pit known as the Megapit. In the mid 1990's the complex was estimated to contain 125 Mt @ 2.1 g/t Au for 260 t of contained gold.
OVERVIEW
Gold mineralisation at Twin Creeks is hosted by a complexly deformed sequence, ranging in age from at least Ordovician to Permian (Bloomstein et al., 1990, Osterberg, 1990; Stenger et al., 1998). The oldest unit is an Ordovician sequence, possibly of the Comus or Valmy Formations, which contains black dolomitic to calcareous shale and siltstone, with interlayered basaltic to ultramafic(?) tuffs, sills and flows. These rocks have been folded into the NW-trending and shallowly plunging Conelea anticline and related folds, that are cut by the steeply dipping, NE-trending, dextral DZ and Twin Creeks faults.
These Ordovician rocks are overlain above a thrust sheet by the Leviathan allochthon, which includes probable Devonian-age basalt and related sedimentary rocks. The Leviathan allochthon is in turn overlain by the Upper Carboniferous (Pennsylvanian) to Permian Etchart Formation with a clear depositional contact. The Etchart Formation is followed by the allochthonous Golconda thrust wedge, which contains the Farell's Canyon, Gough's Canyon, and Havallah Formations. This latter sequence comprises interbedded limestone, chert, siltstone, and sandstone with minor basalt flows.
The Palaeozoic section is locally intruded by Cretaceous granodiorite dykes and sills, and by Tertiary tuffs and volcaniclastic sedimentary rocks, which are also present in the mine area. Superficial (alluvial) cover thickens from the NW to the SE, attaining thicknesses of > 250 m on the southern margin of the Megapit.
The Conelea anticline and related folds, which deform the Ordovician sequence, are the oldest structures in the Twin Creeks area. Thers structures, and at least one fault, the Lopear thrust, were probably formed during the Devonian to Lower Carboniferous (Mississippian) Antler orogeny. The Leviathan allochthon, which truncates the upper parts of the fold system, suggest it formed after folding, as did the Twin Creek and DZ faults. The Etchart Formation, unconformably overlying the Leviathan allochthon, suggests the thrusting was pre-Upper Carboniferous (pre-Pennsylvanian) in age. NE-trending faults, cutting the Chimney Creek part of the mine, displace Cretaceous dykes and sills in the Etchart Formation and could have formed during the Mesozoic Sevier orogeny, though they are probably older, reactivated structures (Bloomstein et al., 1990, Osterberg, 1990; Stenger et al., 1998).
Gold at Twin Creeks is present in a variety of host rock lithologies and ages. In the Chimney Creek North pit, the host comprises outcropping Permo-Carboniferous dolomite, calcareous sandstone and basalt, while in the Rabbit Creek-Chimney Creek South sector it falls within Ordovician calcareous shale, chert and basaltic tuff and lava, concealed below 165 m of piedmont gravels. The late Cretaceous Osgood Mountains granodiorite batholith is located 8 km to the west, although offshoot dykes are mapped at Chimney Creek. Twin Creeks represents a 5.6 km long, north-south trending belt of gold mineralisation some 300 to 450 m wide. Mineralisation within the Ordovician is localised in the nose of, and favourable lithologies in the limbs of, an overturned antiform, whereas the ore-bearing Permo-Carboniferous rocks dip gently. Gold mineralisation is associated with micron sized, very high As arsenian-pyrite that was deposited along with various combinations of quartz, adularia, sericite, realgar, orpiment and stibnite. The ore is associated with intense decalcification, silicification producing jasperoid, and sericitisation of basaltic units. Calcareous units at Chimney Creek underwent widespread "sanding". Twin Creeks differs from many other sediment hosted gold deposits in that it has large areas of high grade gold associated with adularia. During the Miocene, extensive supergene oxidation removed both carbon and sulphides from the upper parts of the orebody. The mine is operated by Newmont Gold Company.
Reserve and resource figures published by Newmont for the Twin Creeks operation at Dec. 2005 were:
Proven + probable reserves - 62.4 Mt @ 2.26 g/t Au = 141 t Au
Measured + indicated resources - 20.28 Mt @ 1.5 g/t Au = 31 t Au
Inferred resources - 3.16 Mt @ 1.01 g/t Au = 3.2 t Au
Published reserves and resources for the Twin Creeks operation at Dec. 2013 (Newmont, 2014) were:
Proven + probable reserves - 35.7 Mt @ 2.05 g/t Au = 73.2 t Au
Measured + indicated resources - 29.0 Mt @ 2.36 g/t Au = 68.4 t Au
Inferred resources - 0.1 Mt @ 1.80 g/t Au = 0.18 t Au
DETAILED DESCRIPTION
The original Rabbit Creek gold mine of the Twin Creeks operation is located some 58 km to the north-east of the town of Winnemucca, Humboldt County, in north-central Nevada. The ore deposit occurs under 60 to 165 m of Quaternary cover on the eastern flank of the Dry Hills, the northern segment of the Osgood Mountains. It is about 8 km to the north-east of the Getchell mine and 2.5 km due south of the Chimney Creek orebody, and is within the Potosi Mining District.
The orebody continues to the north across the original section boundary to become the Chimney Creek South deposit on the former Gold Fields Mining Corporation property (Bloomstein, et al., 1990).
Histortic published reserves are as follows:
Initial Reserve, 1989 - 53 Mt @ 2.4 g/t Au = 128 t Au (Bloomstein, et al., 1990), including:
Oxide ore, 1989 - 45 Mt @ 1.7 g/t Au (Bloomstein, et al., 1990).
High grade sulphide ore, 1989 - 1 Mt @ 6 g/t Au ( Bloomstein, et al., 1990).
Proven+Probable Reserve, 1992 - 101 t Au (American Mines Handbook, 1994).
Geological Resource, 1990 - 249 t Au (Bloomstein, et al., 1990).
The reserves are distributed as follows from Bloomstein, et al., (1990):
Oxide Reserve, 1990 - 14 Mt @ 2.0 g/t Au = 28.0 t Au (North-Central Area).
Sulphide Res., 1990 - 4.98 Mt @ 6.4 g/t Au = 31.8 t Au (North-Central Area).
Total, Proven+Probable Reserve, 1990 - 14 Mt @ 1.5& g/t Au = 21.0 t Au (268 Area), including:
Sulphide Reserve, 1990 - 0.258 Mt @ 4.6 g/t Au (268 Area).
Oxide, Probable Reserve, 1990 - 17.3 Mt @ 2.0 g/t Au = 34.6 t Au (122 Area).
Sulphide Res., 1990 - 2.3 Mt @ 5.3 g/t Au = 12.2 t Au (122 Area).
Geology
The gold mineralisation at Rabbit Creek is hosted entirely by the upper Cambrian to lower Ordovician Comus Formation of the Transition Assemblage, below 12 to 200 m of Quaternary alluvial fan deposits. The orebody is covered by 60 to 165 m of this alluvium.
The orebody is hosted by black calcareous shales, siltstones, cherts and basaltic hydroclastic tuffs of the Comus Formation. The total thickness of the formation known from drilling is 370 m. Its age is based on fossil evidence.
The Comus Formation has been divided into a lower and an upper member on lithological and chemical criteria. These criteria are 1) the ratio of sediments to basaltic rocks; 2) the presence or absence of coarse volcaniclastic rocks; and 3) the content of TiO2, CaO and organic carbon. The two members are differentiated as follows:
* The proportion of sedimentary rocks in the lower member is about twice that of basalts, while in the upper member the basaltic rocks are similar in volume to the sediments;
* Beds of coarse volcaniclastics are only found in the upper member where they may represent as much as 20% of the total rocks;
* Sedimentary rocks of the lower member are more calcareous, more dolomitic and contain more organic carbon. The sediments of the lower member were apparently originally a calcareous mudstone, while those of the upper member were mostly a calcareous-silicic mudstone;
* The sediments of the upper member have a higher TiO2:Al2O3, ratio reflecting a greater contribution from mafic volcanism compared to those of the lower member (Bloomstein, et al., 1990).
The host sediments of the Rabbit Creek gold mineralisation are classified as claystones or siltstone. Sandstones are rare or absent. Although the claystones and siltstones are calcareous, limestones with >75% calcite are rare. Most of the claystones and mudstones have <50% calcite. Bedded micro-crystalline siliceous rocks such as chert and siliceous mudstone are also present at Rabbit Creek. Siliceous mudstones are defined as having more than 30% silt-sized detrital grains (Bloomstein, et al., 1990).
The principal lithologies of the two members of the Comus Formation are as follows:
Lower Member - which contains 75% sediments and 25% igneous rocks. It ranges from 170m in thickness in the north to 240 m in the south (Bloomstein, et al., 1990). The individual rock types that constitute the member are as follows:
Black Shales, Mudstones and Siltstones - The shales of the lower member are thinly laminated and typically fissile. The laminated nature decreases as the rock becomes more siliceous or calcareous. They exhibit non-planar and disturbed bedding, commonly with slump features, shale breccias and shale conglomerates. Interbedded light grey to yellowish grey siltstones are present in places. The shales are made up of calcite, dolomite, illitic clay, pyrite, organic carbon, quartz and radiolaria. Calcite comprises on average 16% of the shales, and occurs as lenses of from 20 µm to 6 mm long, and as grains of 30 µm to 5 mm across, occurring in layers with detrital silt and sand grains, and pyrite cubes. Dolomite is characterised by 10 µm rhombs and accounts for 1 to 3% of the shales. The clays are diagenetic illite and are about 17% of the rock, occurring as random flakes in mudstones, and as oriented flakes in shales. Pyrite occurs as framboidal, disseminated-amorphous and cubic forms. The diagenetic framboidal pyrite is 4 to 30 µm in size and accounts for 5 to 15% of the shale. The disseminated-amorphous variety makes up 5% of the sediment and is 2 to 20 µm in diameter, while the pyrite cubes amount to only 1% of the rock and are 2 µm to 2 mm across (Bloomstein, et al., 1990).
Organic carbon comprises 0.6 to 1.5% by weight of the black shales of the lower member and have been subjected to a high degree of thermal maturation. Organic matter occurs as micro-lenticular concentrations parallel to bedding. Megascopic organic matter is present as opaque clots in organic rich bands and as translucent coatings in organic rich veinlets. About 90% of the organic matter is represented by thermally mature kerogen. Some textures resemble algae remnants. The kerogen has undergone very strong heating and thermal maturation measured from 4 to 5 units of vitrinite reflectance, corresponding to meta-anthracite coal rank. Organic matter also contains white fragments of solid pyro-bitumen which occur in stylolites and in gash fractures in calcareous shales. Micro-fractures are abundant in the main anticlinal axis. Flooding of pyro-bitumen veinlets in calcareous shale makes the rock sooty, soft and very black. The shales also contain visible translucent veinlets of pyro-bitumen. Carbon enhancement and bitumen enrichment apparently predated gold mineralisation. In addition to the mature organic carbon, the lower member shales contain both light and heavy bitumens, or saturated hydrocarbons, which are respectively indigenous and remobilised (Bloomstein, et al., 1990).
Not all of the dark colouration is due to hydrocarbons. In places it is due to a very fine grained powdering of sulphides, principally pyrite. In parts of the orebody the rock has a strong odour resulting from the combination of hydrocarbons and sulphur (Bloomstein, et al., 1990).
Quartz occurs as both detrital and micro-crystalline forms, and accounts for up to 12% of the rock, averaging 8%. Rounded detrital grains range in size from silt to sand and are commonly concentrated in layers (Bloomstein, et al., 1990).
Radiolarian Chert - occurs with silicified mudstones and contains radiolaria as oval and balls which have been silicified and/or pyritised (Bloomstein, et al., 1990).
Basalts - Two basalt flows, as described below in the Upper Member description, are found within the Lower Member. These are the Main Sill and the HGO Flow which are 10 to 30 m and 1 to 10 m thick respectively. The lowest 'basaltic' band is the Mafic Porphyry, a peridotite sill near the base of the section which is described below (Bloomstein, et al., 1990).
Mafic Porphyry - which occurs near the base of the section and is 2 to 3 m thick in the north and 70 m thick in the south of the property. It is a distinctive igneous rock with large phenocrysts, up to 1 cm across, of hypersthene and Ca-poor pigeonite. It also contains 2 to 5% phlogopite and 1% apatite and is a two pyroxene peridotite or lherzolite which has been subjected to chloritisation and carbonate veining (Bloomstein, et al., 1990).
Upper Member - which contains 50% basaltic rocks, 20% hydroclastic tuffs and coarse volcaniclastics, and 30% fine grained siltstones, cherts and shales. It is around 170 m thick (Bloomstein, et al., 1990). The principal lithologies are as follows:
Basalts - occur as a series of conformable units which may be correlated between drill holes on the basis of their texture and chemical composition. They have vesicles, pillow structures and impart load structures on the underlying sediments. They are consequently interpreted to be flows. Six principal flows are recognised within the Rabbit Creek section. Three are within the upper member. These are the Upper Sill/341 Porphyry, the Top Sill/311 Porphyry and the Northern Sill/316 Porphyry, which have thicknesses of 20 to 30 m, 20 m and 30 m respectively. The basalts are mainly tholeiitic, with lesser alkalic basalt. They contain coarse phenocrysts of plagioclase from 0.25 to 5 mm in size, with smaller grains of clinopyroxene between them, giving the rock a doleritic texture. All of the basalts are metamorphosed and altered, containing two separate assemblages. The first is an early metamorphic phase of albitisation and propylitisation (chlorite, calcite and minor epidote), followed by a late alteration related to gold mineralisation consisting of silicification, and argillisation (Bloomstein, et al., 1990).
Hydroclastic Tuffs and Associated Coarse Volcaniclastics - which comprise around 20% of the upper members thickness. The coarse grained hydroclastic (hyaloclastite) breccias are interbedded with fine grained hydroclastic siltstones and basaltic lavas. A large variety of hydroclastic rocks types are represented. The hydroclastic rocks of the upper member contain of a large percentage of angular, vesicular, glassy clasts which apparently originated from pillow basalts. The hydroclastic tuffs and breccias are all highly altered, with volcanic glass being converted to clay and iron oxides, pyroxene and olivine phenocrysts are altered to serpentine, while plagioclase phenocrysts are now clay and quartz. Veinlets of carbonate, minor pyrite with sericite and quartz veins developed in the volcaniclastics after the hydroclastic disaggregation (Bloomstein, et al., 1990).
Reworked volcaniclastics occur as beds ranging in thickness from several cm's to 4 m. Typically they comprise several types of fragments that include vesicle-rich altered glass, clear vesicle-poor glass and siltstone. The clasts are cemented together by hematite stained carbonate. The rock is interpreted to be epiclastic (Bloomstein, et al., 1990).
Siltstone, Mudstone and Shale - The poorly sorted siltstones are greenish-grey to orange-grey in colour, typically composed of quartz silt approximately 60 µm in diameter, with carbonate clasts of up to 300 µm in a matrix of micro-crystalline quartz, carbonate, clay and cubic pyrite. The beds are typically 0.6 to 1.3 cm thick, but may be up to 10 cm. They are calcareous and may have up to 1.5% organic carbon. The thin bedded siltstones have an association with hydroclastic and volcaniclastic rock which contain lapilli sized fragments. The fine siltstones however have no basaltic clasts, glass shards or broken crystals, and their common source is only evident in geochemistry. Most of the Ti in the siltstones and shales is as rutile intergrown with illite, although anatase, leucoxene and ilmenite are also present (Bloomstein, et al., 1990).
Cherts - distinct bedded primary or early diagenetic cherts are present, but are difficult to discern from hydrothermally silicified products. The primary cherts are micro-crystalline and homogeneous in contrast to the spongy, crustiform and honey-comb textures of the rocks produced by hydrothermal silicification (Bloomstein, et al., 1990).
Massive Sulphide - an 8 m thick stratabound lens is contained within a Ti rich hydroclastic tuff band which has been silicified and sericitised. Grades of up to 9.35% Zn, 4.35% Pb and 228 g/t Ag have been recorded. The sulphide content is up to 75%, mostly pyrite/marcasite which occurs as sub-parallel large, anhedral masses, with lesser sphalerite, galena, chalcopyrite, tetrahedrite and enargite. Most of the latter sulphides occur in discontinuous veinlets cross-cutting the pyrite/marcasite masses (Bloomstein, et al., 1990).
Structure
Three major periods of deformation and corresponding stress fields have been interpreted at Rabbit Creek (Bloomstein, et al., 1990). These are:
Ordovician Extension - which is taken to be reflected by the basaltic volcanics which comprise a significant proportion of the sequence at Rabbit Creek (Bloomstein, et al., 1990).
Compressional Stress Field - which is post Ordovician, but pre-Tertiary, possible related to the Devono-Carboniferous Antler Orogeny. This deformation is responsible for the majority of the structure at Rabbit Creek. The principal structural elements of the Rabbit Creek mine area, based on drilling data, are (see plan no. AMNa nbh):
Conelea Antiform - which dominates the structure of the Rabbit Creek mine. It is an overturned, asymmetric, conjugate fold with a sharp, sub-angular hinge zone. The axis strikes at 330° to 340°, dips south-west at 20° to 30° and plunges at 5° to the north-west. The beds of the lower limb strike at approximately 330° and dip 60° to the south-west, while the upper limb may dip at up to 30°, but averages 10°, also to the south-west. To the south of the DZ Fault the anticline becomes isoclinal, with the upper limb being thrust eastward over the lower limb by as much as 180 m.
Un-named Synform - whose axis is sub-parallel to, and about 300 m to the east of that of the Conelea Antiform. The axial plane of the synform strikes at 345° and dips at around 50° to the south-west. The western limb beds are also the lower limb of the Conelea Antiform and dip steeply to the south-west. The eastern limb of the synform is not uniform. The lower parts of this limb dip steeply to the south-west at 70° to 80°, while the upper parts are only 10° to 15°.
Broad Open Folds - are developed in the flatter limbs. These include the Tapper and Owen antiforms, with north-west to north-north-west axial trends, similar to that of the Conelea Antiform.
Small Scale Folds and Faults - Small scale folds are common, with wavelengths of a few cm's to a few metres. They generally have parallel limbs and curved hinges. Small scale plastic and brittle deformation is evident in a range of lithologies. Micro-faulting, both reverse and normal, is present and in places is abundant in core. The micro-faulting is most frequent in areas of brittle deformation where the sense of movement is predominantly reverse. Many of the micro-faults and micro-fractures have not been sites of ore deposition, although they do commonly contain veinlets.
North-east Trending Faults - Three such faults offset the Conelea Antiform. The northern-most of these, the 25° striking DZ Fault has about 600 m of dextral offset is a zone of left stepping, 40° striking shears that dip north-west at 50°. At its thickest the DZ Fault zone is 90 m wide. The other two faults are the Wry Tail and Bills Faults, each progressively further to the south. The Wry Tail strikes at 45° and dips at 50° NW, while Bills Fault strikes at 55° and dips 50° NW. Both have 90 m of dextral strike slip movement.
North to North-north-west Trending Fault - which is a normal structure dipping at 40° to 60° W in the northern part of the mine area, north of the DZ Fault, along the projection of the Conelea Antiformal axis.
These structures are consistent with a major north-south basement fracture with dextral displacement which has formed and rotated the conjugate Conelea Antiform and produced the three north-east trending faults as Reidel shears. This north-south trend is the lineament passing through Chimney Creek and Rabbit Creek mentioned in the 'General' section above (Bloomstein, et al., 1990).
Miocene Extension and Uplift - of the Basin and Range episode. This phase appears to have had little influence on the mineralisation other than allowing it to be buried.
Mineralisation and Alteration
The Rabbit Creek gold deposit is located within a north-south oriented trend of gold mineralisation that is at least 5.6 km long and 300 to 450 m wide. This structural trend is considered to be the first order control of mineralisation (Bloomstein, et al., 1990).
The Rabbit Creek deposit consists of three intensively drilled areas of mineralisation, namely the North-Central, 268 and 122 Areas. These comprise a continuous zone of ore grade mineralisation to the northern boundary of the property and continue north into the Chimney Creek South deposit drilled by Gold Fields. Two additional areas of mineralisation, the West-Central and East-Central are located outside of, and flanking, the main north-south belt of ore. Drilling in these has been limited, and only primary sulphide ore is known within them (Bloomstein, et al., 1990).
While mineralisation is continuous over the interval described above, in detail it is present as a number of disconnected, overlapping zones in different structural and stratigraphic positions (Bloomstein, et al., 1990). The main areas and zones may be summarised as follows:
North-Central Area - which contains six different mineralised zones, based on their structural and stratigraphic settings. The reserves outlined within the North-Central Area in 1990 comprised, oxide ore - 14 Mt @ 2.0 g/t Au, and sulphide ore - 4.98 Mt @ 6.4 g/t Au. This was contained within six different mineralised zones, three within the Lower Member of the Comus Formation, the HGO, SWS and Main Chert Zones; and three within the Upper Member, the DZ, LGO and Upper Sill Zones (Bloomstein, et al., 1990).
Oxidation and mineralisation are strongly influenced by structure and stratigraphy, with the primary control being structure. The oxidation-reduction boundary is relatively uniform and shallow in flat lying beds, but occurs as tongues which can be quite deep in steeply dipping beds. Alteration, especially decalcification, along with brecciation and a relatively high permeability are all important controls promoting extensive oxidation (Bloomstein, et al., 1990).
268 Area - The majority of the mineralisation in this area is hosted by the Lower Member of the Comus Formation, with most of the reserves in one ore zone, the Jackrabbit. The Main Chert Zone hosts abundant low grade and minor high grade mineralisation in both the upper and lower limbs of the Conelea Antiform. There is only minor ore in the volcaniclastics of the Upper Member, in the sparsely drilled eastern parts of the area. Total proven and probable reserves in 1990 were 14 Mt @ 1.5 g/t, including a sulphide reserve of 0.258 Mt @ 4.6 g/t Au (Bloomstein, et al., 1990).
122 Area - Two mineralised zones, the Jackrabbit and Snowshoe host the majority of gold in the 122 Area. Both are within the lower limb of the Conelea Antiform and are commonly associated with deep oxidation. The reserves outlined within the 122 Area in 1990 comprised, oxide ore - 17.3 Mt @ 2.0 g/t Au, and sulphide ore - 2.3 Mt @ 5.3 g/t Au (Bloomstein, et al., 1990). The main ore zones are:
Gold is associated with anomalous As, Sb and Hg values which contrast with low Ag. The levels of these elements is higher than in most other deposits on the Carlin, Cortez-Battle Mountain and Getchell Trends, with the exception of Getchell. Ag, As, Sb and Hg values are three times higher in sulphide, compared to oxide ore. The North-Central ore zones have As averages in the range 6030 to 17 700 ppm in the sulphide zone versus 1100 to 3380 ppm in the oxide zone, with maximum values of 38.5% and 3.6% As respectively. Equivalent Hg levels are from 18 to 69 ppm and 2.5 to 36 ppm, with maximum values of 895 and 400 ppm Hg respectively. Sb values in the same area averaged from 85 to 720 ppm in the sulphide ore and 200 to 270 ppm in the oxide ore, with respective maxima of 2.25 and 0.7% Sb. Ag average values similarly are 7.2 to 200 g/t in sulphide ore zones and 0.4 to 1 g/t in the oxide ores, with respective maxima of 200 g/t and 11.5 g/t Ag. Trace element contents are also dependant upon the host lithology, with un-oxidised ores hosted by Lower Member shales having twice the As and Sb of the basaltic volcaniclastic hosted ores of the Upper Member. Oxidation lowers high As values, although Sb and Hg are not depleted to the same degree (Bloomstein, et al., 1990).
For detail consult the reference(s) listed below.
See also Twin Creeks - Chimney Creek
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.
Rabbit Creek
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Selected References:
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Cline, J.S., Hofstra, A.H., Muntean, J.L., Tosdal, R.M. and Hickey, K.A., 2005 - Carlin-Type Gold Deposits in Nevada: Critical Geologic Characteristics and Viable Models: in Hedenquist, J.W., Thompson, J.F.H., Goldfarb, R.J. and Richards, J.P. (eds.), Economic Geology, 100th Anniversary Volume, Society of Economic Geologists, pp. 451-484.
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Fortuna J, Kesler S E, Stenger D P 2003 - Source of iron for sulfidation and gold deposition, Twin Creeks Carlin-type deposit, Nevada: in Econ. Geol. v98 pp 1213-1224
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Groff J A, Heizler M T, McIntosh W C, Norman D I 1997 - 40Ar/39Ar dating and mineral paragenesis for Carlin-type Gold deposits along the Getchell Trend, Nevada: evidence for Cretaceous and Tertiary Gold mineralization: in Econ. Geol. v92 pp 601-622
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Hall C M, Kesler S E, Simon G, Fortuna J 2000 - Overlapping Cretaceous and Eocene alteration, Twin Creeks Carlin-type deposit, Nevada: in Econ. Geol. v95 pp 1739-1752
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Simon G, Kesler S E, Chryssoulis S 1999 - Geochemistry and textures of Gold-bearing Arsenian Pyrite, Twin Creeks, Nevada: implications for deposition of Gold in Carlin-type deposits: in Econ. Geol. v94 pp 405-422
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Stenger D P, Kesler S E, Peltonen D R, Tapper C J 1998 - Deposition of Gold in Carlin-type deposits: the role of sulfidation and decarbonation at Twin Creeks, Nevada: in Econ. Geol. v93 pp 201-215
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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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