Gold Quarry Research Articles

Estimates of pit-lake evaporation and its potential effects on groundwater interactions with the Humboldt River

The Humboldt River, in northern Nevada supplies water mostly for irrigation of nearby croplands. Groundwater pumping both near and distant from the river has increased over the past 50 years. The primary use of groundwater is for irrigation of croplands but it is also an important source for municipalities, mining and other industries. Large gold deposits that require dewatering were discovered in the mountains of the central part of the drainage basin in the 1970’s and 1980’s. Much of the water pumped to dewater the mines is recharged back to groundwater in the valleys or is released to the Humboldt River or one of its tributaries. Of concern is the long-term loss of groundwater from pit-lake evaporation and how those losses could affect groundwater interactions with the Humboldt River once mine operations cease. Flows in the Humboldt River are mostly dependent on snowmelt runoff from the mountains, particularly from mountains in the drainage area upstream of the Palisade gaging station. The mean flow increases with drainage area between the gaging stations upstream of Elko and at Palisade, whereas the mean flow decreases downstream of the Palisade gaging station. Much of the decrease in mean flow downstream of Palisade is caused by: (1) minimal additional contributions from runoff and groundwater flow; (2) spreading of water to native pastures on the floodplain; and (3) infiltration of river water into its associated alluvium. During low-flow periods, particularly during periods of drought, the Humboldt River between Battle Mountain and Comus gaging stations often has flows less than 1 cubic foot per second (cfs) even before there was any mine dewatering. Estimated groundwater loss to evaporation for the five largest pit lakes in the drainage area between the Palisade and Comus gaging stations is about 5,400 acre-feet per year (afy) (7.6 cfs or five times less than the estimated net annual evaporation loss from the Rye Patch and the Pitt-Taylor Reservoirs upstream of Lovelock, Nevada. The groundwater loss to three of the pit lakes (Goldstrike Mine, Cortez operations, and Twin Creeks Mine) is unlikely to affect river flow because even prior to mine dewatering, groundwater flow from the low-lying mountains was lost to evapotranspiration near the base of the alluvial fans and did not contribute flow to the river. The Lone Tree Mine ceased dewatering in December 2006 and since then a lake has formed in the pit. The floodplain of the Humboldt River in the reach between Battle Mountain and Comus is underlain by a layer of blue clay at shallow depth. Between 2007 and 2019, the net mean annual streamflow loss between Palisade and Comus is nearly the same as during a period of little groundwater pumping from 1946 to 1969 suggesting that even the relatively large amount of water pumped from the mine has had a little effect on Humboldt River flows. Groundwater evaporation from the eventual pit-lake at the Gold Quarry Mine is estimated at 740 afy (about 1 cfs) and could perhaps decrease the gain in the Humboldt River upstream of Palisade. How much of a decrease is uncertain because some of it could be lost to evapotranspiration at the edge of the floodplain prior to reaching the river. Even if the groundwater loss from the pit lake at Gold Quarry Mine were to reduce the gain of river flow between Carlin and Palisade, the loss would be too little to measure accurately.

Fe-oxides in jasperoids from two gold districts in Nevada: Characterization, geochemistry, and (U-Th)/He dating

This study examines the whole-rock geochemistry, Fe-oxide texture and crystal morphology, and Fe-oxide (U-Th)/He date variation of jasperoids, as well as the relationships between these characteristics, in order to evaluate jasperoids as an indicator for gold mineralization. Jasperoid samples with a range of textures, appearances, and expected gold concentrations were collected from two gold districts in Nevada: the northern Carlin trend (Gold Quarry Mine), and the Battle Mountain district (Marigold Mine; Battle Mountain prospect). In our jasperoid samples, whole-rock concentrations of Au are positively correlated with As, Ag, Pb, Sb, U, W, and Tl. The following Fe-oxide textures are associated with anomalous gold concentrations: disseminated, submicron crystals; feathery and acicular crystal morphologies; concentric zonation from hematite to goethite; and botryoidal textures. Calculated closure temperatures for the (U-Th)/He system in observed jasperoid Fe-oxide morphologies within our dataset range from 26 to 136 °C, indicating variable susceptibility to He diffusion at near-surface conditions. Fe-oxide (U-Th)/He dates range from 29.4 ± 0.5 Ma to 0.11 ± 0.01 Ma, displaying intra- and intersample variation. We attribute the date variation to multiple factors including He implantation, parent isotope exchange, and He loss through closure temperature sensitivity and alpha-ejection. The intra- and intersample variation within the Fe-oxide (U-Th)/He dates limits our ability to make geologic interpretations. Our case study identifies important limitations of the (U-Th)/He method in jasperoids and provides insight on how He date variation might be avoided in future studies.

Invisible Gold Paragenesis and Geochemistry in Pyrite from Orogenic and Sediment-Hosted Gold Deposits

LA-ICPMS analysis of pyrite in ten gold deposits is used to determine the precise siting of invisible gold within pyrite, and thus the timing of gold introduction relative to the growth of pyrite and related orogenic events. A spectrum of invisible gold relationships in pyrite has been observed which suggests that, relative to orogenic pyrite growth, gold introduction in some deposits is early at the start of pyrite growth; in other deposits, it is late toward the end of pyrite growth and in a third case, it may be introduced at the intermediate stage of orogenic pyrite growth. In addition, we report a distinct chemical association of invisible gold in pyrite in the deposits studied. For example, in the Gold Quarry (Carlin type), Mt Olympus, Macraes and Konkera, the invisible gold is principally related to the arsenic content of pyrite. In contrast, in Kumtor and Geita Hill, the invisible gold is principally related to the tellurium content of pyrite. Other deposits (Golden Mile, Bendigo, Spanish Mountain, Witwatersrand Carbon Leader Reef (CLR)) exhibit both the Au-As and Au-Te association in pyrite. Some deposits of the Au-As association have late orogenic Au-As-rich rims on pyrite, which substantially increase the value of the ore. In contrast, deposits of the Au-Te association are not known to have Au-rich rims on pyrite but contain nano- to micro-inclusions of Au-Ag-(Pb-Bi) tellurides.

Trace elements in fluid inclusions of sediment-hosted gold deposits indicate a magmatic-hydrothermal origin of the Carlin ore trend

Abstract The Carlin-type deposits in Nevada (western USA) constitute the world’s second-largest gold ore province. These structurally and stratigraphically controlled, sediment-hosted ore bodies are characterized by carbonate dissolution attending hydrothermal precipitation of gold-rich arsenian pyrite. The origin of the mineralizing fluids and the source of the gold remain debated. Conceptual models, favoring either sedimentary, metamorphic, or magmatic fluid sources, are based on isotopic tracers, giving ambiguous results. Here we use the trace element compositions of fluid inclusions to separate geochemical signals of the large-scale fluid source from effects of deposit-scale fluid interaction with the sedimentary host rocks. Specifically, we compare the ratios of Rb, K, B, As, Sr, and Ba between clearly magmatic-hydrothermal Cu-Au ores at Copper Canyon in the Battle Mountain–Eureka trend with the Gold Quarry and Chukar Footwall deposits on the Carlin trend that contain high-grade gold in similar sedimentary host rocks. Results indicate that both ore districts can be related to upper crustal hydrous magmatic intrusions, but are now exposed at different levels of erosion and formed at different distances from their magmatic fluid source. Fluid compositions are best explained by separation of a deep magmatic fluid into Rb-K–enriched brine and B-As-Au–enriched vapor, followed by cooling and contraction of the magmatic vapor phase to an epithermal liquid, which reacted with Sr-Ba–bearing sedimentary rocks during ascent and eventual precipitation of Au-rich arsenian pyrite.

Discovery of low aluminium nevadaite from the Kara-Chagyr Area, Kyrgyzstan

The rare phosphate—nevadaite has been found at Kara-Chagyr (Batken region, Kyrgyzstan) in a zone of alteration of vanadium bearing “black shales”. It occurs as blue crusts of spherulitic aggregates of tiny tabular crystals (0.1–10 μm). It is associated with metahewettite, hummerite, carnotite, minyulite, fluellite, crandallite, variscite, and woodhouseite. Optical properties: n = 1.542–1.555, D meas (for aggregates) = 2.58(1) g/cm3, D calc = 2.582 g/cm3. The most intense X-ray powder reflections are as follows: [d/n, A, (I meas), (hkl)]: 9.54 (80) (020), 6.03 (100) (200), 5.61 (100) (130), 3.91 (60) (310), 3.41 (80) (041), 2.982 (100) (241), 2.804 (60) (331), 2.672 (70) (061), 1.845 (60) (352) 1.507 (70) (243). Calculated cell dimensions are: a = 12.072(10) A, b = 18.958(15) A, c = 4.969(5) A, α = β = γ = 90°, V = 1137.2 A3. Electron microprobe analyses gives (wt %): (observed (average of 8 analyses); (calculated for 22H2O)): P2O5 34.69 (31.85), SiO2 0.25 (0.24), Al2O3 25.61 (23.50), V2O 5.58 (5.13), Fe2O3 0.48 (0.46), MnO 0.03 (0.03), CuO 10.79 (9.90), ZnO 0.69 (0.65), CaO 0.18 (0.15), MgO 0.17 (0.17), K2O 0.08 (0.08), F 7.40 (6.79), H2O 17.16 (by diff.) (23.90), −F2 =O $$ \bar 3 $$ .11 ( $$ \bar 2 $$ .86), total 100.00 (100.00).The crystal-chemical formula of the mineral is (Cu 2.2 +2 □2.03V 1.21 +3 Al0.15Zn0.14Fe0.10Mg0.07Ca0.05K0.03Mn0.01)6.00(Al8.00(P7.93Si0.07O32)F6.32(OH)2.98 · 22(H2O) for the ideal number of water molecules. Nevadaite from Kara-Chagyr differs from that from the type locality, Gold Quarry (Nev., USA), by its lower Al content. The IR-spectrum, and microphotographs of nevadaite and associated minerals are given.

Matioliite, the Mg-analog of burangaite, from Gentil mine, Mendes Pimentel, Minas Gerais, Brazil, and other occurrences

Matioliite, ideally NaMgAl 5 (PO 4 ) 4 (OH) 6 ·2H 2 O, occurs as a secondary hydrothermal mineral in the Gentil mine granite pegmatite, Mendes Pimentel Co., Minas Gerais, Brazil. Some crystals are zoned to more Fe-rich compositions with an Fe 2+ :Mg ratio of approximately 1:1, corresponding to an intermediate member of the burangaite-matioliite solid-solution series. Matioliite is intimately associated with fluorapatite, crandallite, and zoned gormanite-souzalite cystals. The mineral forms prismatic to tabular crystals, up to 1 mm long. Matioliite is transparent and displays a vitreous luster; it is blue to colorless with a white streak. It is non-fluorescent. Mohs hardness is about 5. Calculated density is 2.948 g/cm 3 . Matioliite is biaxial negative, η α = 1.597(2), η β = 1.627(2), η γ = 1.632(1) (white light), 2V (meas.) = 43(2)°, 2V (calc.) = 44°, dispersion r > v, orientation X = b, Z ^ c = 6°. Pleochroism is Y > X > Z, X = light blue to colorless, Y = blue, Z = colorless. The empirical formula is (Na 0.94 Ca 0.01 ) Σ0.95 (Mg 0.88 Fe 2+ 0.11 Mn 0.01 ) Σ1.00 (Al 4.84 Fe 3+ 0.13 ) Σ4.97 (PO 4 ) 4.03 (OH) 5.76 ·2H 2 O. The mineral is monoclinic, space group C2/c, a = 25.075(1) Å, b = 5.0470(3) Å, c = 13.4370(7) Å, β = 110.97(3)°, V = 1587.9(4) Å 3 , Z = 4. Crystal-structure determination was carried out and showed it is isostructural with burangaite, dufr énite, and natrodufrénite. Both the description and the name were approved by the CNMMN-IMA (Nomenclature Proposal 2005-011). The .magnesium analog of burangaite. described from the Gold Quarry mine, Carlin-trend, Eureka County, Nevada; “burangaite” from Hochgosch, Millstätter See-Rücken, Kärnten, Austria; and .burangaite. described from Córrego Pomarolli, Linópolis, Divino das Laranjeiras, Minas Gerais, Brazil, are probably matioliite.

NEVADAITE, (Cu2+, , Al, V3+)6 [Al8 (PO4)8 F8] (OH)2 (H2O)22, A NEW PHOSPHATE MINERAL SPECIES FROM THE GOLD QUARRY MINE, CARLIN, EUREKA COUNTY, NEVADA: DESCRIPTION AND CRYSTAL STRUCTURE

Nevadaite, (Cu 2+ , □, Al, V 3+ ) 6 (PO 4 ) 8 F 8 (OH) 2 (H 2 O) 22 , is a new supergene mineral species from the Gold Quarry mine, near Carlin, Eureka County, Nevada, U.S.A. Nevadaite forms radiating clusters to 1 mm of prismatic crystals, locally covering surfaces more that 2 cm across; individual crystals are elongate on [001] with a length:width ratio of >10:1 and a maximum diameter of ~30 μm. It also occurs as spherules and druses associated with colorless to purple-black fluellite, colorless wavellite, strengite–variscite, acicular maroon-to-red hewettite, and rare anatase, kazakhstanite, tinticite, leucophosphite, torbernite and tyuyamunite. Nevadaite is pale green to turquoise blue with a pale powder-blue streak and a vitreous luster; it does not fluoresce under ultraviolet light. It has no cleavage, a Mohs hardness of ~3, is brittle with a conchoidal fracture, and has measured and calculated densities of 2.54 and 2.55 g/cm 3 , respectively. Nevadaite is biaxial negative, with α 1.540, β 1.548, γ 1.553, 2 V (obs.) = 76°, 2 V (calc.) = 76°, pleochroic with X pale greenish blue, Y very pale greenish blue, Z blue, and with absorption Z ≫ X > Y and orientation X = c , Y = a , Z = b. Nevadaite is orthorhombic, space group P 2 1 mn , a 12.123(2), b 18.999(2), c 4.961(1) A, V 1142.8(2) A 3 , Z = 1, a:b:c = 0.6391:1:0.2611. The strongest seven lines in the X-ray powder-diffraction pattern [ d in A(I)( hkl )] are: 6.077(10)(200), 5.618(9)(130), 9.535(8)(020), 2.983(6)(241), 3.430(4)(041), 2.661(4)(061), and 1.844(4)(352). A chemical analysis with an electron microprobe gave P 2 O 5 32.54, Al 2 O 3 27.07, V 2 O 3 4.24, Fe 2 O 3 0.07, CuO 9.24, ZnO 0.11, F 9.22, H 2 O (calc.) 23.48, OH ≡ F–3.88, sum 102.09 wt.%; the valence states of V and Fe, and the amount of H 2 O, were determined by crystal-structure analysis. The resulting empirical formula on the basis of 63.65 anions (including 21.65 H 2 O pfu ) is (Cu 2.00 2+ Zn 0.02 V 0.98 3+ Fe 0.01 3+ Al 1.15 ) ∑ 4.16 Al 8 P 7.90 O 32 [F 8.37 (OH) 1.63 ] ∑10 (H 2 O) 21.65 . The crystal structure of nevadaite was solved by direct methods and refined to an R index of 4.0% based on 1307 observed reflections collected on a four-circle diffractometer with Mo K α X-radiation. The structure consists of ordered layers of vertex-sharing octahedra and tetrahedra alternating with layers of disordered vertex-sharing and face-sharing octahedra in the b direction. [Alϕ 5 ] chains of octahedra are decorated by (PO 4 ) tetrahedra that share vertices with octahedra adjacent in the chain. These chains link in the c direction by sharing vertices between octahedra and tetrahedra to form an ordered layer of the form [Al 8 (PO 4 ) 8 F 8 (H 2 O) 8 ]. In the disordered layer, octahedral containing positionally disordered Cu 2+ , V 3+ , Al and □ (vacancy) share trans faces to form columns that link by sharing octahedron vertices to form ribbons extending in the c direction; the resulting layer has the form {(Cu 2 2+ □ 2 V 3+ ,Al) ∑6 (H 2 O) 12 (OH) 2 (H 2 O) x }, x ≈ 2. The layers link in the b direction by sharing vertices between octahedra and tetrahedra. Although decorated chains topologically equivalent to that in nevadaite are common in many oxysalt minerals, its chain is geometrically distinct from those topologically equivalent chains. The M – M linkage along the [ M ϕ 5 ] chains in most minerals take place through trans vertices of the octahedra, with one example of linkage through cis vertices; in nevadaite, the M – M linkage involves both trans and cis vertices, as does the chain in slavikite. In most of these decorated chains, alternate tetrahedra along the chain occur either in a trans or a cis arrangement. In nevadaite and slavikite, the tetrahedra are arranged in both trans and cis arrangements; the arrangements in these two minerals are geometrically distinct, however.

Meurigite, a new fibrous iron phosphate resembling kidwellite

AbstractMeurigite is a new hydrated potassium iron phosphate related to kidwellite and with structural similarities to other late-stage fibrous ferric phosphate species. It has been found at four localities so far — the Santa Rita mine, New Mexico, U.S.A.; the Hagendorf-Sud pegmatite in Bavaria, Germany; granite pegmatite veins at Wycheproof, Victoria, Australia; and at the Gold Quarry Mine, Nevada, U.S.A. The Santa Rita mine is the designated type locality. Meurigite occurs as tabular, elongated crystals forming spherical and hemispherical clusters and drusy coatings. The colour ranges from creamy white to pale yellow and yellowish brown. At the type locality, the hemispheres may reach 2 mm across, but the maximum diameter reached in the other occurrences is usually less than 0.5 mm. A wide variety of secondary phosphate minerals accompanies meurigite at each locality, with dufrenite, cyrilovite, beraunite, rockbridgeite and leucophosphite amongst the most common. Vanadates and uranates occur with meurigite at the Gold Quarry mine.Electron microprobe analysis and separate determination of H2O and CO2 on meurigite from the type locality gave a composition for which several empirical formulae could be calculated. The preferred formula, obtained on the basis of 35 oxygen atoms, is which simplies Qualitative analyses only were obtained for meurigite from the other localities, due to the softness and openness of the aggregates. Because of the fibrous nature of meurigite, it was not possible to determine the crystal structure, hence the exact stoichiometry remains uncertain. The lustre of meurigite varies from vitreous to waxy for the Santa Rita mine mineral, to silky for the more open sprays and internal surfaces elsewhere. The streak is very pale yellow to cream and the estimated Mohs hardness is about 3. Cleavage is perfect on {001} and fragments from the type material have a mean specific gravity of 2.96.The strongest lines in the X-ray powder pattern for the type material are (dobs,Iobs,hkl) 3.216(100)404; 4.84(90)111; 3.116(80)205; 4.32(70)112; 9.41(60)201; 3.470(60)800. The X-ray data were indexed on the basis of a monoclinic unit cell determined from electron diffraction patterns. The cell parameters, refined by least squares methods, are a = 29.52(4), b = 5.249(6), c = 18.26(1) Å, β = 109.27(7)°, V = 2672(3) Å3, and Z = 4. The calculated density is 2.89 gcm−3. The space group is either C2, Cm or C2/m. X-ray powder data for meurigite are closely similar to those for kidwellite and phosphofibrite, but meurigite appears to be characterised by a strong 14 Å reflection. The relationship between these three minerals remains uncertain in the absence of structural data. On the available evidence, meurigite and kidwellite are not the respective K and Na-endmembers of a solid solution series. The meurigite cell parameters suggest it belongs to a structural family of fibrous ferric phosphates, such as rockbridgeite, dufrenite and beraunite, which have a discrete 5 Å fibre axis. Meurigite occurs in widely varying environments, its formation probably favoured by late-stage solutions rich in K rather than Na.

Geology of the Gold Quarry mine

The Gold Quarry mine has developed a large, epithermal, disseminated gold deposit hosted by Paleozoic siliciclastic sediments. The deposit consists of two, easterly tilted, stacked orebodies; an upper structural stockwork and a lower stratabound replacement. Anomalous crustal heat flow associated with Oligocene volcanic rocks appears responsible for the formation of a large hydrothermal system at Gold Quarry. Wallrock alteration and mineral concentration are spatially and temporally associated with this event. Rock alteration types include decalcification, silicification, alunitization, argillization and oxidation. Complex and repeated compressional and extensional tectonic events combined with litho-chemical characteristics of the host sediments to form sites favorable to mineral deposition. A dominant elemental association of AuAsSbHgTl is directly associated with mainstage Oligocene mineralization. A subordinate association of AgPbZnCuNi appears to represent earlier mineralizing events. A continuing deep exploration program has shown that mineralization remains open to the south.

Processing Gold Quarry refractory ores

The Gold Quarry deposit is the largest sediment-hosted gold deposit yet discovered on the Carlin trend in northern Nevada. However, despite the locale’s vast reserves, the gold is difficult to extract from portions of the deposit. Detailed, ongoing mineralogical analyses assure proper treatment of the ore.

Comparative elemental and oxygen isotope geochemistry of jasperoid in the northern Great Basin; evidence for distinctive fluid evolution in gold-producing hydrothermal systems

This comparative geochemical study of jasperoid in the northern Great Basin is based on 65 samples from 10 Carlin-type gold deposits and 22 similar but apparently barren hydrothermal systems. Multielement geochemistry coupled with oxygen isotope data indicate that hydrothermal fluids in barren and mineralized systems evolved in different ways, and that there are fundamental geochemical differences among the various gold-producing deposits of the area.Much of the variation in the jasperoid geochemical data can be explained in terms of seven abstract end-member components obtained through factor analysis. Three of these components (factors) dominate the results and are related to common products of alteration and mineralization in epithermal systems of the northern Great Basin. Element associations for these factors are: factor 1: TiO 2 , Al 2 O 3 , La, K 2 O, Sr, Fe 2 O 3 , Th; factor 2: Au, Ag, Sb, SiO 2 , As, Pb; and factor 3: W, B, V, Zn, Co, Au, CaO, Ni, Mn, Cu.Samples from barren systems are predominantly associated with high factor 1 loadings, whereas samples from mineralized systems are generally characterized by high loadings of factor 2 and/or factor 3. Factor 1 is related to residual, argillically altered, noncarbonate constituents in original host rocks. Factor 2 is related to hydrothermal silica (jasperoid) and is characterized by many of the so-called pathfinder elements used in Great Basin exploration. Factor 3, although characterized by a transition metal assemblage, is related to syngenetic inclusions of hydrothermal calcite within jasperoidal silica.High factor 2 loadings are associated with samples from the Windfall and Northumberland deposits but not with samples from other gold-producing systems in the study. Factor 3, on the other hand, is the dominant component in most samples from the Carlin, Gold Quarry, Maggie Creek, Pinson, and Preble deposits. It therefore appears that there are at least two geochemically discernible types of gold deposits in the northern Great Basin. These types are represented in this study by the Windfall deposit (factor 2) at one extreme and by the Gold Quarry deposit (factor 3) at the other. Other deposits, including Alligator Ridge and Tonkin Springs, are intermediate between these extremes. In this study, the hydrothermal geochemistry of the Jerritt Canyon samples is obscured by a chert-related compositional factor.Jasperoid samples from gold-producing ore deposits have delta 18 O values ranging from 3 to 20 per mil, whereas jasperoid samples from analogous barren systems have delta 18 O values ranging from 3 to 11 per mil. This indicates that at least some fluids in ore-related hydrothermal systems were relatively 18 O rich compared to those in barren systems. Jasperoid samples having high delta 18 O values invariably have high factor 3 loadings.The elemental and isotopic geochemistry of jasperoid samples indicates that hydrothermal fluids in individual gold-producing systems of the northern Great Basin evolved in different ways. It appears that high CO 2 contents were a critical distinguishing feature of deeply circulating fluids in the hydrothermal systems associated with high factor 3 loadings. Within the scope of this study, it therefore appears that the systems located on the Carlin and Getchell trends (mineral belts) must have been relatively CO 2 rich. Fluids in these systems would have been relatively reactive and perhaps more efficient at extracting gold and other metals from rocks in fluid exchange reservoirs. Moreover, the generally high 18 O character of ore-stage fluids in these systems, as inferred from jasperoid compositions, is indicative of extensive water-rock exchange.The largest gold deposits in the jasperoid study area appear to have been high CO 2 , high 18 O systems. The primary source of CO 2 in these systems is uncertain. It does appear, however, that deep crustal structure, rather than the lithologic character of fluid exchange reservoirs, was probably a dominant factor governing the distribution of high CO 2 systems in the northern Great Basin.