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Twin Creeks - Chimney Creek |
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Nevada, USA |
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Au
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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 Chimney Creek and Rabbit 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 Chimney Creek gold mine of the Twin Creeks operation is located about 60 km to the north-east of the town of Winnemucca, Humboldt County, in north-central Nevada. The ore deposit occurs on the eastern flank of the Dry Hills, the northern segment of the Osgood Mountains. It is about 10 km to the north-east of the Getchell mine and 2.5 km due north of the Rabbit Creek orebody, within the Potosi Mining District.
The Chimney Creek orebody was discovered in early 1985 by Gold Fields Mining Corporation, a subsidiary of the London based Consolidated Gold Fields Plc. Following a feasibility study, stripping started during the summer of 1987, with some 380 000 t of overburden being removed to expose the ore prior to the commencement of production. Heap leaching commencing in October. Construction also commenced in the summer of 1986 and was completed in November 1987. Start-up of the mill was in mid November, with the first gold being poured on 23rd November 1987, less than 3 years after the orebody was discovered. The initial capital cost was $US 91 m, for a combined heap leach and milling operation with a planned production rate of 4.65 t Au per annum. The stripping ratio for the life of the mine was planned to have been 0.6:1, waste:ore. The work force in 1988 was 137 (E&MJ, 1988a).
A combination carbon-in-pulp and carbon-in-column circuit is used for the mill ore. A separate carbon-in-column circuit is utilised for the heap leaching operation while a common stripping circuit is used for gold recovery from both. A recovery rate of 92% was expected for the mill ore, and 60% for the heap leach operation (E&MJ, 1988a).
The Chimney Creek orebody was owned and operated by Gold Fields Mining Corporation until acquired by Santa Fe Pacific Corporation in mid 1993. It was then amalgamated with Santa Fe's Rabbit Creek mine to form the Twin Creeks operation (Amer. Mines H'book, 1994). During 1994 Santa Fe Pacific Gold (SFPG) was floated as a separate company and shares were distributed to the shareholders of Santa Fe Pacific Corporation, which now no longer owns the SFPG (Amer. Mines. H'book, 1995).
Historic published reserves include:
Mill Reserve, 1991 - 10.9 Mt @ 3.86 g/t Au = 42 t Au (Amer. Mines H'book, 1992).
Leach Reserve, 1991 - 38.5 Mt @ 0.98 g/t Au = 38 t Au (Amer. Mines H'book, 1992).
Feasibility Proven+Probable Reserve, 1986 - 20.4 Mt @ 1.99 g/t Au (E&MJ, 1988a).
Proven+Probable Reserve, 1988 - 24.5 Mt @ 2.33 g/t Au comprising 11 Mt - mill; 13.5 Mt - leach (E&MJ, 1988a).
Inferred Reserve 1988, Chimney Ck South - 12.7 Mt @ 1.68 g/t Au = 22 t Au (E&MJ, 1988a).
Sulphide Resource, Chimney Ck South, 1988 = 65 t Au (E&MJ, 1988b).
The Chimney Creek South deposit is the northern extension of the Rabbit Creek orebody across the property boundary, and is approximately 2 km to the south of the main Chimney Creek pit (Bloomstein, etal., 1990). It is possible that the two reserve/resource figures quoted for this deposit may 'overlap'.
Production from Chimney Creek in 1991-92 was approximately 12.5 t Au (Amer. Mines H'book, 1992).
The main Chimney Creek orebody is a sub-horizontal tabular body which apparently has surface dimensions of the order of 500 m in diameter, and may be 30 to 50 m thick ('Guestimate' from plans in Osterberg & Guilbert, 1990).
Geology
The Chimney Creek orebody is approximately 90% hosted by the upper Carboniferous to lower Permian Etchart Limestone and 10% by the underlying lower Carboniferous Goughs Canyon Formation. The Etchart Limestone is a shallow water mixed silici-clastic and carbonate unit of the Overlap Assemblage, while the Goughs Canyon Formation, which comprises meta-basalt lavas and intercalated chemical sediments, represents an eastward interfingering of mafic volcanics of the Havallah Sequence into the Overlap Assemblage. Both units are unconformably above the Ordovician Vinini Formation of the Western Assemblage, which was apparently thrust eastward during the Devono-Carboniferous Antler Orogeny (Osterberg & Guilbert, 1990).
The stratigraphy within the Dry Hills is as follows (Osterberg & Guilbert, 1990), from the structural base:
Upper Cambrian to Lower Ordovician, Comus Formation - This unit belongs to the Transition Assemblage. See the Getchell description, above.
Roberts Mountains Thrust - formed during the Devono-Carboniferous Antler Orogeny. The Western Assemblage may have been thrust eastward over this structure, or one of its upper imbricates onto the Transition Assemblage. The evidence for such thrusting on the Getchell Trend is not conclusive. The overlying Valmy Formation may be an eastern depositional finger of the Western Assemblage into the Transition Assemblage.
Ordovician, Valmy Formation - which consists of chert, shale, sandstone, minor limestone, greywacke, basalt and greenstone and belongs to the Western, or Siliceous Assemblage. These volcanics and sediments outcrop to the south and south-west of Chimney Creek.
Non-conformity .
Lower Carboniferous (Mississippian), Goughs Canyon Formation, >425 m thick - a sequence of predominantly basalts which have been metamorphosed and variably altered and now range from greenschists which retain their volcanic textures, to intensely hydrothermally altered rocks. The basalts are fine to medium grained, felty to ophitic assemblages of albite, chlorite, kaolinite, sericite, calcite and amphibole with accessory leucoxene, quartz, pyrite, augite, epidote and limonite. Albite replaces calcic plagioclase, while chlorite, epidote, amphibole and a fine grained equi-granular mosaic of quartz and K-feldspar replaces the glassy groundmass. Stockwork calcite veining is ubiquitous. Sericite and quartz-sulphide veins, as discussed below, overprint this assemblage in the mine area. The deepest drill holes have intersected 250 m of pillow basalts with well formed hyaloclastite rims. Interflow chemical sediments (cherts?) which range from 0.1 to 1 m in thickness occur sporadically within the basalts, with poorly preserved upper Palaeozoic radiolaria. A 20 m variolite unit is found near the base and a 20 to 25 m hyaloclastite unit near the top. Stratigraphically below the pillow basalts are 150 m of massive, undivided basalts. These basalts are petrographically similar to the pillow basalts and contain similar interflow hyaloclastites and chemical sediments.
Non-conformity .
Upper Carboniferous (Pennsylvanian) to Lower Permian, Etchart Limestone, >850 m thick - a mixed silici-clastic and carbonate sequence of interpreted shallow water origin. This sequence belongs to the Overlap Assemblage, and is also known as the Etchart Formation. Four informal lithologic members have been mapped at Chimney Creek, with the bulk of the economic mineralisation being within the basal member. These are:
Basal Member, 175 m thick - with a non-conformable basal contact marked by a conglomerate lag bed with cobbles of basalt. Above the lag there are 4 metres of thick bedded, coarse grained, poorly sorted, quartz, chert, feldspar, illite and lithic fragment rich pebbly litharenite with a thin siltstone bed at the top. The next 100 m are coarse grained sandy dolomite and dolomite. These rocks have been traced laterally into partially dolomitised calcareous sandstones and sandy biosparites. Coarse grained, turbid, subhedral to euhedral rhombs with rims of exsolved Fe-oxide characterise the dolomites. The dolomites are commonly bound together by calcite while 10% have bioclastic nuclei. Thin siltstone interbeds made up of quartz grains in an illitic matrix are intercalated at 10 to 30 m intervals throughout the member. Hydrothermal alteration has converted the illite to sericite, kaolinite, dickite, alunite and natroalunite. The top of the member is 35 m of light grey, massive to thin bedded biosparite and sandy biosparite.
Lower-Middle Member, 230 m thick - composed of equal amounts of calcareous sandstone, and sandy biosparite with 10% conglomerate. The lithologies are intercalated and rarely exceed 15 m in thickness. The calcareous sandstones and biosparites are similar to those of the Basal Member. The conglomerates contain clast supported sub-mature to mature pebbles and cobbles of all of the resistant older lithologies in the Osgood Mountains and are cemented by fine to coarse grained quartz and calcite.
Upper-Middle Member, 120 m thick - which is dominated by dolomitic rocks. The lower 100 m are dolomite, sandy dolomite and silty dolomite, while the upper 20 m is dark grey massive to thin bedded bio-micrite. The Carboniferous to Permian boundary is some 80 m above the base of the member. The lithologies are the same as those of the Basal Member.
Upper Member, >335 m thick - This member is decapitated by the Farrel Canyon Thrust. It carries Permian conodonts. The lower 200 to 225 m are dolomitic siltstone and argillite, passing upwards into 50 to 75 m of calcareous sandstone and then 65 m of dolomitic siltstone. Thin bio-micrites are present at irregular intervals.
Farrel Canyon Thrust - which belongs to the Permo-Triassic Golconda Thrust package. The Havallah Sequence was over-thrust eastwards above this structure onto the rocks of the Roberts Mountains Allochthon and the overlying Overlap Assemblage during the Sonoma Orogeny.
Lower Carboniferous (Mississippian), Farrel Canyon Formation - This unit is very similar to the upper member of the Etchart Limestone, although limestones in its lower sections carry lower Carboniferous conodonts. Siltstone is predominant with interbeds of sandstone, chert, shale and limestone.
Tertiary, Volcanics - overlie the sequence.
Igneous rocks are present in the form of two trachyandesite dykes which cut both the volcanics and carbonates. These dykes have a similar composition to those that radiate outwards from the Osgood Mountain Stock at Getchell. They are 1 to 7 m thick and are composed of coarse grained plagioclase and quartz set in a fine grained matrix of plagioclase, quartz, hornblende, biotite and ilmenite. Within the orebody the groundmass of the dykes is altered with complete replacement of the original minerals by very fine grained sericite and pyrite. This in turn is overprinted by disseminated smectite/montmorillonite and kaolinite. Both dykes have a metamorphic aureole of around 3 m, in some places up to 10 m, in width within the carbonates, mainly producing marble (Osterberg & Guilbert, 1990).
Structure
The Chimney Creek and Rabbit Creek deposits lie along a range front fault similar to the Getchell Fault 10 km to the west along which the Getchell, Pinson and Preble deposits are aligned. This 100 m wide range front fault zone dips steeply and is composed of numerous sinuous and anastomosing flanking structures along which movement has been individually negligible, but collectively significant (Osterberg & Guilbert, 1990).
Bedding plan faults in the Etchart Limestone are commonly marked by 1 to 2 m wide zones of intense brecciation and are especially prevalent along siltstone units. Movement appears to be predominantly pre-mineral (Osterberg & Guilbert, 1990).
North trending oblique slip faults displace sections of the orebody. The most important of these is a 30 m thick fault which juxtaposes the basal and upper members of the Etchart Limestone. It is marked by a topographic depression and corresponds to isolated on-strike jasperoid outcrops. This fault has a sinistral displacement of 300 m and vertical west side down component of 30 m (Osterberg & Guilbert, 1990).
The covered areas east of the main outcrop of Etchart Limestone were separated into discrete blocks by post-mineral faulting. Gravel cover varies from 30 m over horsts to 30 to 200 m over grabens. Broad open folds with wavelengths of several hundred metres and amplitudes of tens of metres are evident within the Etchart Limestone. These have not apparently influenced the emplacement of ore or subsequent erosion (Osterberg & Guilbert, 1990).
Alteration and Mineralisation
Zones of intense phyllic wall rock alteration, separated by weakly propylitic altered basalt, are apparently continuous from the deepest drill holes within the Goughs Canyon Formation, coalescing upwards near the contact with the Etchart Limestone to form a sub-horizontal zone of pervasive alteration and Au-Ag mineralisation. Wholesale dissolution and replacement of carbonate beds in the Etchart Limestone occurred immediately above the zones of intensely altered basalt. Farther away only selective replacement of individual beds took place (Osterberg & Guilbert, 1990).
Within the Goughs Canyon Formation a three dimensional network of 1 to 50 m wide phyllic envelopes flank fault and fracture zones (referred to as "feeder faults") and separate them from the propylitic altered basalts. These phyllic envelopes comprise fine grained massive sericite which pervasively replaces all primary and propylitic textures in the cores of the alteration zones. Outside of the core the intensity decreases, becomes less pervasive until only albite is dusted by sericite on its margins. Narrow 1 to 10 cm wide quartz-sulphide stockwork veins and veinlets are present within the envelopes, while fine pyrite is disseminated throughout the phyllic zones. The sericite envelopes coalesce near the contact with the overlying Etchart Formation carbonates to form a zone of pervasive and extensive phyllic alteration that contains ore grade mineralisation. Au and Ag mineralisation occurs along the "feeder faults" themselves in the areas most heavily sericitised and pyritised. Sparse, very fine, kaolinite-dickite and limonite overprint the greenschist and sericite assemblages, with kaolinite-dickite being found throughout the drilled stratigraphy, not just near the surface (Osterberg & Guilbert, 1990).
Alteration of the Etchart Limestone was most intense above and adjacent to the "feeder faults" which are marked within the underlying Goughs Canyon Formation by the phyllic envelopes. Precious metal mineralisation within the carbonate units is associated both temporally and spatially with carbonate dissolution and bedding conformable silicification, as follows:
Decalcification (or carbonate dissolution) - Primary carbonates were apparently dissolved and flushed out of approximately 1 cubic km of the Chimney Creek orebody, leaving large zones of insoluble silicates and dolomite to which barite, silver and gold were added. These zones of carbonate dissolution commonly have the consistency and competence of siliceous beach sands and are informally termed 'sanded limestone'. In the centre of the orebody dissolution was pervasive and intense with even dolomite removed (ie. what is termed 'decarbonatisation' on the Carlin Trend). Only calcareous beds of enhanced permeability and porosity were affected distally. Dissolution zones may be traced laterally along individual 1 to 3 m thick beds to the outer limits of development drilling, a maximum distance of 600 m. The highest Au and Ag grades are coincident with the most severe dissolution. These zones of most severe dissolution occur along upward projections into the Etchart Limestone of the "feeder faults" and their phyllic envelopes in the Goughs Canyon Formation below. Gold grades drop off slightly with distance from the projected "feeder faults" (Osterberg & Guilbert, 1990).
Silicification Two generations of silicification are evident at Chimney Creek, namely:
Bedded Jasperoids - which comprises the early phase stratabound silicification associated with carbonate dissolution. This is the most diagnostic alteration phase at Chimney Creek. Bedded jasperoids form tabular bodies from 30 to 50 m thick, extending at least 600 m outwards from the centre of Chimney Creek, and are invariably Au bearing. The decalcification and silicification is pervasive and intense, destroying the fine sedimentary textural details of the original calcareous sandstone and leaving only the detrital quartz grains and trace remnants of the calcite from that rock. The jasperoid is grey and massive, composed of very fine to fine grained detrital quartz grains in a grain supported or matrix supported framework with a very fine to fine grained alpha quartz matrix. Locally the pore space is filled by well developed quartz overgrowths on detrital grains. In hand specimen the altered silicified rock resembles lower Palaeozoic pebbly litharenites of the Osgood Mountains Quartzite (Osterberg & Guilbert, 1990).
In the core of the orebody, secondary silica within the bedded jasperoid was alternately precipitated and dissolved. In these areas it is composed of extremely angular, partly resorbed quartz grains in a hematite-limonite matrix. Sericite, kaolinite, pyrite, tourmaline and fluorite are finely disseminated throughout the bedded jasperoid. Very fine grained calcite remnants are caught up in the contacts between detrital grains and the overgrowths. Calcite is also present as late-stage, fine grained, euhedra (Osterberg & Guilbert, 1990).
Very fine grained barite was deposited throughout the cycles of dissolution and deposition of bedded jasperoid and in 'sanded' carbonate. Apatite is present as detrital grains, as discrete 1 to 10 mm wide hydrothermal veinlet fillings and as very fine grained anhedral replacement granules in the bedded jasperoid (Osterberg & Guilbert, 1990).
The cycles of dissolution and precipitation have left the deposit core dominated by sanded units, with isolated blocks of bedded jasperoid surrounded by an annulus of intensely silicified rock. The silicification over all is conformable and rootless (Osterberg & Guilbert, 1990).
Cross-cutting Jasperoid - which comprises later silicification along faults. This style of silicification dissects the orebody and cuts decarbonatised rock, bedded jasperoid and quartz-sulphide veinlets. Cross-cutting jasperoid is reddish-brown, very fine grained and massive. Subsequent fault movement brecciated this jasperoid, and in many cases, late stage calcite has re-cemented the rock. Cross-cutting jasperoid is composed of very fine grained, or silt sized, angular quartz grains in a cryptocrystalline quartz-hematite-limonite matrix. Hematite and limonite form 0.1 to 1 mm wide veinlets and stockworks in cross-cutting jasperoid. Such jasperoid is generally barren, but can contain up to 3.7 g/t Au. Indistinguishable bedded and cross-cutting jasperoid d18O values suggest that silica dissolved from bedded jasperoid was re-precipitated as cross-cutting jasperoid (Osterberg & Guilbert, 1990).
Marble - is developed as a selvage, up to 7 m thick, flanking the trachyandesite dykes that cut the orebody. It comprises very fine grained calcite, quartz, kaolinite and smectite/montmorillonite. The dykes cross cut and refracts along the zones of carbonate dissolution in the orebody. Gold grades in the dyke are erratic and significantly lower than in the carbonates. In one case a 30 cm xenolith of mineralised carbonate within the dyke assayed 1.66 g/t Au, while the surrounding dyke yielded 0.08 to 0.15 ppm Au. The adjacent 'carbonate' hosted ore varied from 0.38 to 7.6 g/t Au. This is taken to indicate that the dyke intruded and marbleised already mineralised and altered carbonate, ie. the dykes are post-ore (Osterberg & Guilbert, 1990).
Calcite Veining - is found in the hangingwall carbonate units where it occurs in sparse tension gashes and as narrow 1 to 10 cm wide veins. Similar tension gashes have not been observed cutting the silicified or 'sanded' carbonate units. d13C and d18O isotopes indicate that the carbonate was flushed from the sanded zones and re-deposited as late stage veins (Osterberg & Guilbert, 1990).
Oxidation - The Chimney Creek orebody is almost completely oxidised, although auriferous sulphides are locally preserved in bedded jasperoids and in quartz-sulphide stockwork veins in the phyllic altered zones. Oxidation forms a tabular zone, roughly parallel to the present surface. It cuts across primary alteration and mineralisation in both the Goughs Canyon Formation and Etchart Limestone (Osterberg & Guilbert, 1990).
Silicate Alteration - Detrital illite, plagioclase and K-feldspar were replaced by hydrothermal sericite and kaolinite-dickite in a zone extending 500 m outward from the centre of the Chimney Creek orebody. The zone of feldspar destruction is cut off to the east and west by regional faults and corresponds to the zone of fracture density of >0.2 per cm. There is also an outward shift from the centre of the orebody from sericite+kaolinite-dickite+alunite, to sericite+kaolinite-dickite+natroalunite (Osterberg & Guilbert, 1990).
K-Ar age dating of sericite in the Echart Limestone in the orebody yielded an age of 98.6±3.5 Ma, which is virtually identical to that from the phyllic alteration in the Goughs Canyon Formation. Un altered detrital illite from the Etchart Formation was dated at 250 Ma.
Since large volumes of carbonate were removed from the orebody, and only partially replaced by bedded jasperoid, some solution collapse is expected. Fracture densities in excess of 0.2 per cm (up to 0.4 per cm) were formed directly over the orebody in contrast to lower values at the margins of the mineralised area of <0.1 per cm. Persistent east-west orientations are oblique to the dominant north-east structural trend in the mineralised area.
For detail consult the reference(s) listed below.
See also Twin Creeks - Rabbit 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.
Chimney 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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