Gold, silver, and mercury rock chemistry for the Adelaide Mining District, Sonoma Range, Humboldt County, Nevada

1989 ◽  
Author(s):  
T.M. Cookro ◽  
T.G. Theodore
Keyword(s):  
Mining District ◽  
Humboldt County ◽  
Gold Silver

Petrogenesis of amphibole – biotite – calcite – plagioclase alteration and laminated gold – silver quartz veins in four Archean shear zones of the Norseman district, Western Australia

1992 ◽  
Vol 29 (3) ◽  
pp. 388-417 ◽  
Author(s):  
Andreas G. Mueller
Keyword(s):  
Western Australia ◽  
Shear Zones ◽  
Wall Rock ◽  
Alteration Zone ◽  
Mining District ◽  
Low Grade ◽  
Fluid Temperature ◽  
Quartz Veins ◽  
The North ◽  
Gold Silver

The Norseman mining district in the Archean Yilgarn Block, Western Australia, has produced 140 t of gold and about 90 t of silver from 11.24 × 106 t of ore. The district is located within a metamorphic terrane of mafic and minor ultramafic greenstones, intruded by granite cupolas and swarms of porphyry dykes. The orebodies consist of laminated quartz veins, controlled by narrow (0.5–5 m) reverse shear zones that, in general, follow the contacts of metapyroxenite or porphyry dykes. Petrological studies of four shear zones, exposed on the Regent shaft 14 level, Ajax shaft 10 level, and in the stope above the North Royal shaft 5 level, show that the host rocks were metamorphosed to hornblende–plagioclase amphibolites and actinolite–chlorite rocks at temperatures of 500–550 °C prior to mineralization.At the localities studied, intense wall-rock replacement and low-grade (0.5 g/t) gold mineralization are confined to ductile or brittle–ductile shear structures. Alteration is similar in both ultramafic and mafic greenstones, and consists of an inner zone of biotite–quartz–calcite–plagioclase rock with minor actinolitic hornblende and quartz–calcite–actinolite veinlets, and an outer zone, locally developed, of chlorite–calcite–quartz rock. At an estimated pressure of 3 kbar (300 MPa), fluid temperatures during wall-rock alteration are constrained by the hydrothermal mineral assemblages to 480 ± 30 °C in two shear zones on the Regent shaft 14 level, and to 450 ± 20 °C in one shear zone in the North Royal shaft 5 level stope. The mole fraction of CO2 of the fluids is estimated at [Formula: see text], and the sulphur fugacity at 10−6 bar (10−1 kPa) (at 450 °C), based on the assemblage pyrrhotite + pyrite ± arsenopyrite. The development of an outer chloritic alteration zone at North Royal is related to the lower fluid temperature at this locality.High-grade (up to 75 g/t Au, 283 g/t Ag) veins formed within three of the shear zones studied at fluid temperatures of 400 °C and less, by the successive accretion of quartz laminae, separated by films of retrograde chlorite and sericite. The assemblage of ore minerals in the veins differs from that in the altered wall rocks, and includes disseminated galena, Pb–Bi–Ag tellurides, and native gold, which coprecipitated with the quartz. The orebodies at Norseman show affinities to Phanerozoic and Archean gold skarn deposits.

Geochronology of the Sleeper Deposit, Humboldt County, Nevada; epithermal gold-silver mineralization following emplacement of a silicic flow-dome complex

1993 ◽  
Vol 88 (2) ◽  
pp. 317-327 ◽  
Author(s):  
James E. Conrad ◽  
Edwin H. McKee ◽  
James J. Rytuba ◽  
J. Thomas Nash ◽  
William C. Utterback
Keyword(s):  
Epithermal Gold ◽  
Humboldt County ◽  
Gold Silver ◽  
Silver Mineralization

Recent Experiences With Prospector II

1994 ◽  
Author(s):  
Richard B. McCammon
Keyword(s):  
Mineral Resource ◽  
Precious Metal ◽  
Quantitative Assessment ◽  
Mineral Resources ◽  
Mining District ◽  
Silver Deposit ◽  
Gold Silver ◽  
Vein Deposits ◽  
Tin Deposit ◽  
Quantitative Assessments

Three recent case studies in which Prospector II was used illustrate a variety of constructive responses that contribute to regional mineral resource assessments. The case studies included a group of precious-metal vein deposits in the Quartzville Mining District in Oregon, United States; a stratabound gold-silver deposit in Manitoba, Canada; and an Archean tin deposit from Western Australia. In each case, the objective was to see how Prospector II would classify the deposit in terms of deposit models in the Cox-Singer compendium. The precious-metal vein deposits in the Quartzville Mining District were interpreted by Prospector II to be part of a larger system likely to contain porphyry copper deposits. The stratabound gold-silver deposit in Manitoba fit the description of the Homestake gold deposit model. The Archean tin deposit from Western Australia bore little resemblance to any of the tin deposit models in the Cox-Singer compendium. In recent years, quantitative mineral resource assessments have gained recognition among land managers and national policymakers, who have found that numerical measures of potential mineral values are essential when considering alternative strategies. Such quantitative assessments allow land managers to plan optimum use of public lands and allow national policymakers to assess the need for securing long-term mineral supplies from international sources. In addition, quantitative assessments encourage the discovery and development of new deposits. Significant advances have been made in developing new techniques for the quantitative assessment of metallic mineral resources (Drew et al, 1986; Reed et al., 1989). In large part, these techniques are based on an earlier method of regional mineral resource assessment proposed by Singer (1975) and subsequently applied to areas in Alaska. The technique is based on the size distribution of mineral deposits of specified geologic types and on the probability of deposit occurrence. This approach to the quantitative assessment of undiscovered mineral resources is being applied to many of the mineral resource assessments being carried out by the U.S. Geological Survey (USGS) (Singer and Cox, 1988). Critical in this approach to quantitative assessment is the geologist's ability to relate the geologic environment in an area to specific deposit types.

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