Автор(ы):John F.H.Thompson, Richard M. Tosdal, Vanessa G.Gale, William A.Wright
Издание:Economic geology, 2004 г., 22 стр.
Characteristics and formation of the Jerónimo carbonate-replacement gold deposit, Potrerillos District, Chile

The Jerónimo sedimentary rock-hosted disseminated Au deposit is located within the Potrerillos district of the Atacama region of northern Chile, east of the Potrerillos porphyry Cu-Mo and El Hueso high-sulfidation Au deposits. Prior to development, the Jerónimo deposit contained a resource of approximately 16.5 million metric tons (Mt) at 6.0 g/t Au. Production began in the oxidized, nonrefractory portion of the deposit in 1997 and terminated in 2002. During that time, approximately 1.5 Mt at 6.8 g/t Au was mined by underground room-and-pillar methods, from which a total of approximately 220,000 oz of Au was recovered by heap-leach cyanidation.

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Jerónimo carbonate-replacement gold deposit, Potrerillos District, Золото
Выпуск 99
Автор(ы):Charles E.Barker, Charles G.Cunningham, Charles W.Naeser, Geoffrey H.Ballantyne, Gerry W.Austin, Robert G.Stamm, Robert O.Rye
Издание:Economic geology, 2004 г., 18 стр.
Formation of a paleothermal anomaly and disseminated gold deposits associated with the Bingham Canyon Porphyry Cu-Au-Mo system, Utah

The thermal history of the Oquirrh Mountains, Utah, indicates that hydrothermal fluids associated with emplacement of the 37 Ma Bingham Canyon porphyry Cu-Au-Mo deposit extended at least 10 km north of the Bingham pit. An associated paleothermal anomaly enclosed the Barneys Canyon and Melco disseminated gold deposits and several smaller gold deposits between them. Previous studies have shown the Barneys Canyon deposit is near the outer limit of an irregular distal Au-As geochemical halo, about 3 km beyond an intermediate Pb-Zn halo, and 7 km beyond a proximal pyrite halo centered on the Bingham porphyry copper deposit. The Melco deposit also lies near the outer limit of the Au-As halo. Analysis of several geothermometers from samples collected up to 22 km north of the Bingham Canyon porphyry Cu-Au-Mo deposit indicate that most sedimentary rocks of the Oquirrh Mountains, including those at the gold deposits, have not been regionally heated beyond the “oil window” (less than about 150ºC).

ТематикаПолезные ископаемые
МеткиBingham Canyon Porphyry Cu-Au-Mo system, Carlin type gold, Gold, Золото
Выпуск 55
Автор(ы):Wide A.
Издание:Economic geology, 2003 г., 5 стр.
The golden triangle of Southeast China: another Carlin Trend?

Numerous gold deposits and occurrences in southeast China are located in an area known as the “Golden Triangle,” mainly in Guizhou province (Fig. 1). Comparisons have been made with sedimentary rock-hosted or “Carlin-type” deposits of northeast Nevada (e.g., Li and Peters, 1998), and at least one major multinational mining company has explored for Carlin-type deposits in this area. Such deposits represent attractive mineral exploration targets owing to the size of the contained resources, high grades, and amenability to open-pit mining operations. Furthermore, the deposits tend to occur as clusters (or “trends”). Discovery of a new mineralized cluster would represent a major coup. In this paper I provide a short summary of aspects of the geology of the southwest Chinese deposits and comment on their similarities and differences compared to the deposits of Nevada.

ТематикаПолезные ископаемые
Выпуск 94
Автор(ы):Asadi H.H., Hale M., Voncken J.H.L.
Издание:Economic geology, 1999 г., 8 стр.
Invisible gold at Zarashuran, Iran

Although micron-size particles of metallic gold are observed at the Zarshuran gold deposit, northwest Iran, the quantities do not account for the gold concentrations determined by chemical analyses. The presence of invisible gold has been established by means of trace element electron microprobe analyses of pyrite, arsenian pyrite, orpiment, realgar, stibnite, getchellite, sphalerite, and lead sulfosalts. Quantitative point analyses indicate that invisible gold is present in anhedral pyrite, arsenian pyrite overgrowth rims on gold- and arsenic-free euhedral pyrite, in massive, network, and colloform arsenian pyrite, and in massive and colloform sphalerite intimately intergrown with colloform arsenian pyrite. Gold in these forms adequately explains the measured gold concentrations at Zarshuran. The invisible gold owes its origin to solid-solution deposition and/or encapsulation of submicron-size particles of metallic gold.

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Zarashuran, Золото
Выпуск 6
Издание:Economic geology, 1988 г., 6 стр.
Sediment hosted replacement gold deposit

Sediment hosted replacement gold deposits, also termed Carlin-type gold deposits from where they were first described, have been major gold producers in the western U.S. (98.8 million ounces discovered; Singer, 1993). Most deposits lie along deep crustal fracture systems which define the Carlin and Battle Mountain Trends (Madrid and Roberts, 1990). Significant new discoveries within the Carlin Trend include the Betze-Post and Meikle ore systems (Bettles and Lauha, 1991), with production of 7.1 million ounces andreserves of 28 million ounces of gold at the end of 1994 (Volk et al, 1995). Reviews of this style of gold mineralization by Bagby and Berger (1985), Sawkins (1984), Sillitoe and Bonham (1990), Berger and Bagby (1991), and Kuehn and Rose (1995) present geological models for this deposit type. Critical in the development of these models has been the recognition of similar deposit types in other settings (e.g., Bau, Sarawak; Wolfenden, 1965; Sillitoe and Bonham, 1990: China; Cunningham et al., 1988: Melco and Barney's Canyon deposits, Bingham District, U.S.; Babcock et al., 1992: Mesel, North Sulawesi; Indonesia; Turner et al., 1994; Garwin et al., 1995: and elsewhere in the eastern and western Pacific Rim, G. Corbett and T. Leach, unpub. data; Gemuts et al, 1996: Fig. S.l).

ТематикаПолезные ископаемые
Выпуск 92
Автор(ы):David A.Mako
Издание:Economic geology, 1997 г., 2 стр.
Characterization and dating of argillic alteration in the Mercur gold district, Utah - a discussion

Wilson and Parry (1995) present data pertaining to clay alteration and K-Ar age dates for samples from the Mercur gold district. Their data record a wide spread of K-Ar ages for illite ranging from 98.4 to 226 Ma. They estimate the age of gold mineralization to be between 140 and 160 Ma and explain the wide range of ages as functions of partial thermal resetting of the clay minerals and the distance from the hydrothermal conduits. Morris and Tooker (1996) in their discussion of this paper, point out that a Mesozoic age for gold mineralization at Mercur is incompatible with several lines of long-standing regional geologic evidence that suggest a Tertiary age. In their reply, Wilson and Parry (1996) defend their position for a Mesozoic age of mineralization in part by relying on new 40Ar/39Ar age data and the fact that none of the 22 age dates is Tertiary. Although the research by Wilson and Parry may represent a good study of samples in the laboratory, there are several tenuous assumptions and contradictions of the geologic observations at Mercur that must be addressed.

ТематикаПолезные ископаемые
Автор(ы):Parry W.T., Paula N.Wilson
Издание:Economic geology, 1996 г., 3 стр.
Characterization and dating of argillic alteration in the Mercur gold district, Utah—a reply

We would like to extend our appreciation to Morris and Tooker for their comments, discussion, and additional information that they provide pertaining to the geologic environment of the Mercur gold district, Utah. Their review of the characteristics of the Sevier orogenic belt are particularly relevant; however, such characteristics must be interpreted within the context of the additional geologic events of the region, which include the Jurassic compressional event that has been described from northern Utah and western Nevada. For this purpose, we offer the following reply.

Morris and Tooker have two main points of disagreement with our paper. First, they find the range of K-Ar ages we reported as disturbing and indicate that they date neither tectonic, hydrothermal, nor gold mineralization events; and second, they contend that all mineralized structures at Mercur must be younger than Late Cretaceous in age.

ТематикаПолезные ископаемые
Выпуск 91
Автор(ы):Parry W.T., Ricardo D.Presnell
Издание:Economic geology, 1996 г., 16 стр.
Geology and geochemistry of the Barneys Canyon gold deposit, Utah

Barneys Canyon is a sediment-hosted, disseminated gold deposit located 7 km from the large, gold-rich, Bingham porphyry copper deposit. Host rocks for gold mineralization are the Permian Park City dolomite and siltstone and the Kirkman-Diamond Creek sandstone. The gold deposit is approximately 430 m long, 370 m wide, up to 90 m thick and contains 8.5 million metric tons (t) of reserves averaging 1.6 g/t gold. Intrusive igneous rocks are conspicuously absent. The gold deposit is located on the northern flank of the northeast-trending Copperton anticline, an overturned box fold. A small east-striking, south-dipping thrust fault, the Barneys Canyon thrust fault, with 200 m displacement, repeats the Park City Formation, and north-south-striking steep normal faults form a graben in which the gold deposit is located. The Barneys Canyon thrust fault predates mineralization and the Phosphate normal fault postdates mineralization.

ТематикаПолезные ископаемые
МеткиBarneys Canyon, Carlin type gold, Gold, Золото
Выпуск 90
Автор(ы):Parry W.T., Paula N.Wilson
Издание:Economic geology, 1995 г., 20 стр.
Characterization and dating of argillic alteration in the Mercur gold district, Utah

The Mercur gold district of north-central Utah includes several sediment-hosted disseminated gold deposits which are located in the lower member of the Mississippian Great Blue Limestone. Argillic alteration of host limestone consists of illite (R3 illite-smectite <10% S) + kaolinite + quartz ± Fe oxides or pyrite. Argillized limestone has identical clay mineralogy in both oxidized and unoxidized rock. Unlike some other sediment-hosted disseminated gold deposits, variations in the Kubler index and illite/kaolinite ratios show no spatial relationship to faults or to gold distribution within the mineralized areas.

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Mercur gold district, Золото
Выпуск 84
Автор(ы):Alan R.Wallace
Издание:Economic geology, 1989 г., 12 стр.
The Relief Canyon gold deposit, Nevada: a mineralized solution breccia

The Relief Canyon gold deposit in the Humboldt Range of western Nevada is a low-grade, high-tonnage orebody of Tertiary or younger age. The host rocks include limestones of the Triassic Cane Spring Formation, which are overlain by shales of the Triassic Grass Valley Formation. The rocks were folded and metamorphosed to greenschist grade during Jurassic and Cretaceous regional tectonic activity. Mesozoic thrusting may have occurred along the shale-limestone contact, but evidence has been obscured by later hydrothermal activity. The sedimentary rocks were nominally offset along several Late Tertiary normal faults related to uplift of the range.

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Humboldt Range, Relief Canyon, Золото
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