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):Wallace A.R.
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
Выпуск 83
Автор(ы):Cinda Graubard, David A.Giles, Miles L.Silberman
Издание:Economic geology, 1988 г., 9 стр.
Characteristics of gold deposits on Nortern Sonora, Mexico: a preliminary report

The geology of northwestern Mexico is complex and is similar in many respects to that of southeastern California and southern Arizona. The region (Fig. 1), typical of the southern basin-and-range physiographic province of which it is a part, is characterized by elongate, northwest-trending ranges separated by wide alluvial valleys. Basement rocks in the area include Precambrian gneisses, metamorphosed andes-ites, and granites. These rocks are overlain by younger Proterozoic quartzites and limestones, Paleozoic and Mesozoic carbonate rocks, and Mesozoic volcanic, clastic, and carbonate sedimentary rocks. Mesozoic plutonic rocks and Tertiary extrusive and intrusive rocks related to volcanic activity of the Sierra Madre Occidental are widely distributed. Broad areas are underlain by plutonic and associated volcanic rocks of the Sonora-Sinaloabatholith of Cretaceous to early Tertiary (Laramide) age. The outcrop areas of the plutonic rocks are smaller in northwestern Sonora, west of Magdalena de Kino where many of the gold deposits are concentrated, than they are farther to the east and south (Fig. 2).

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Nortern Sonora, Золото
Выпуск 83
Автор(ы):Charles G.Cunningham, Huang Zushu, I-Ming Chou, Li Wenkang, Roger P.Ashley, Wan Chaoyuan
Издание:Economic geology, 1988 г., 6 стр.
Newly discovered sedimentary rock-hosted disseminated gold deposits in the People's republic of China

Sedimentary rock-hosted disseminated gold deposits (Carlin-type deposits) have recently been recognized in the People's Republic of China. Five deposits discovered in Guizhou Province, Yata, Getang, Sanchahe, Ceyang, and Banqi are described here for the first time in Western literature (Fig. 1). The deposits have geologic features and geochemical signatures that are remarkably similar to those of sedimentary rock-hosted precious metal deposits in the United States. The sizes of the deposits are as yet undetermined, but they each contain significant reserves at average grades of 4 to 5 g of gold per metric ton. Exploration and drilling are in progress at all of the deposits, and other areas where the geologic setting and geochemical anomalies are similar are being tested.

The deposits are located in a relatively inaccessible region in the southern part of the People's Republic of China. Four of the five deposits described in this report were visited in September 1986 as part of a cooperative study between the U. S. Geological Survey and the Ministry of Geology and Mineral Resources of the People's Republic of China. Transportation and logistical support for site visits were provided by the Bureau of Geology and Mineral Resources of Guizhou Province, the organization primarily responsible for mineral exploration in the region.

Very little has been published about sedimentary rock-hosted disseminated gold deposits in the People's Republic of China (Li et al., 1986). The Chinese literature sometimes refers to them as "underground hydrothermal (brine) leaching gold deposits" (Cai Changjin and Li Zhixiang, unpub. data, 1986). Analytical information from samples collected in the course of this study is available in Dean et al. (1988)

Выпуск 83
Автор(ы):Angel A.A., Donald C.Noble
Издание:Economic geology, 1988 г., 11 стр.
Sedimentary Rock-Hosted Disseminated Precious Metal Mineralization at Purisima Concepcion, Yauricocha District, Central Peru

Sedimentary rock-hosted disseminated gold ores lithologically and chemically similar to those of Carlin-type deposits of the western United States are present in the Yauricocha district, central Peru. The Purisima Concepcion deposit is located in the core of a steeply plunging anticline several hundred meters beyond large pipe-shaped Cu-Zn-Pb-Ag-Au replacement orebodies in limestone bordering a late Miocene granodiorite stock. The central part of the stock is potassium-silicate altered and contains high-salinity fluid inclusions.

ТематикаПолезные ископаемые
МеткиCarlin type gold, Gold, Yauricocha district, Золото
Выпуск 82
Автор(ы):Parry W.T., Paul W.Jewell
Издание:Economic geology, 1987 г., 9 стр.
Geology and hydrotermal alteration of the Mercur gold deposit, Utah

The term "Carlin-type" deposit has been applied to a number of low-grade, sedimentary rock-hosted gold deposits that have been discovered and brought into production in the western United States since the 1960s. Carlin-type deposits are characterized by replacement of carbonate and silty carbonate rocks by silica, pyrite, barite, various arsenic, mercury, antimony, and thallium minerals and by introduction of micron-size gold (Radtke and Dickson, 1974). These deposits are believed to have formed in the upper few kilometers of the earth's crust under conditions that are similar in some respects to present-day geothermal systems.

The Mercur mining district in west-central Utah contains a number of gold deposits of this type. The district is located approximately 90 km southwest of Salt Lake City in the southwest portion of the Oquirrh Mountains, a typical north-south-trending range of the Basin and Range physiographic province (Fig. 1). Two major orebodies, Mercur-Sacra-mento and Marion Hill, are present in small hills in the center of the steep, east-west-trending Mercur Canyon. Initial production of silver in the Mercur district was from an interval of silicified limestone known as the "Silver ledge" (Spurr, 1895), a term which was later changed to "Silver chert." Fine gold was discovered in 1883 in a stratigraphic interval 30 m above the Silver chert. Production terminated in 1917 after more than 1.2 million ounces of gold had been produced (Butler et al., 1920). The district was reopened in 1983 with the Getty Mining Company as the principal operator.

The first geologic description of the Mercur district was given by Spurr (1895). Butler et al. (1920) gave a concise, accurate review of the geology, stratigraphy, and mineral production at Mercur. Gilluly's (1932) work remains the most comprehensive published study of the southern Oquirrh Mountains. Lenzi (1973) published data on the background geochemistry at Mercur. Tafuri (1976) described the general geology and mineralization at Mercur.

This communication gives a detailed discussion of the hydrothermal alteration of the Mercur deposits. The discussion will provide a framework for continuing studies of the paragenesis and geochemistry at Mercur as well as allowing comparison with alteration assemblages of other Carlin-type deposits.

ТематикаПолезные ископаемые
Выпуск 98
Автор(ы):Arehart G.B., Chakurian A.M., Christopher J.N., Donelick R.A., McInnes B.A., Tretbar D.R.
Издание:Economic geology, 2003 г., 14 стр.
Evaluation of Radioisotope Dating of Carlin-Type Deposits in the Great Basin, Western North America, and Implications for Deposit Genesis

A variety of techniques have been used in attempts to date the mineralization in Carlin-type deposits in the Great Basin, with highly variable results. These techniques and results are reviewed in this paper, along with presentation of two new dates, for the Rodeo deposit on the Carlin trend and for the Barneys Canyon deposit in Utah. Complete resetting of sericite by hydrothermal fluids of the temperature and duration of hydrother-mal activity that form Carlin-type deposits is considered highly unlikely. Therefore, dates from sericite are generally of questionable value unless that sericite can be shown to have formed during the same hydrothermal event during which Au was deposited. For the deposits that have been investigated to date, sericite dates rarely, if ever, record the age of Au mineralization. However, sericite ages do appear to record pre-Au events in some districts. Such events may have contributed to ground preparation and, to a much lesser extent, to the tenor of the ore. Fission-track and U/Th-He techniques provide important age constraints on mineralization in some districts but also suffer from a less than clear association with Au. Rb-Sr dating of galkhaite, an Hg sulfosalt, provides the only direct age of mineralization, but galkhaite has been recognized in only a few locations (and dated in only two deposits). In a similar manner, adularia is contemporaneous with Au at Twin Creeks, but Twin Creeks is the only Carlin-type deposit where adularia has been reported. Several other techniques (U-Pb, Re-Os, Sm-Nd) have been used in attempts to date the deposits but with limited success.

ТематикаПолезные ископаемые
Выпуск 92
Автор(ы):Christian J.Grainger, David I.Norman, Heizler M.T., McIntosh W.C.
Издание:Economic geology, 1997 г., 22 стр.
40Ar/39Ar Dating and Mineral Paragenesis for Carlin-Type Gold Deposits along the Getchell Trend, Nevada: Evidence for Cretaceous and Tertiary Gold Mineralization

The orebodies at the Getchell and Twin Creeks mines were studied through mineral paragenesis, geologic relationships, and 40Ar/39Ar dating. Mineral paragenetic relationships are based on observations made during the logging of 18,000 m of drill cuttings and core and crosscutting relationships recognized in the field and Main pit at the Getchell mine. Ages for igneous and mineralizing events were determined through 40Ar/39Ar incremental heating analyses of 15 samples of biotite, K feldspar, sericite, and vein adularia. A thermal history for the area was also developed using K feldspar multiple diffusion domain results and age determinations on cogenetic minerals, which have different argon closure temperatures.

ТематикаПолезные ископаемые
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