| Stephen G. Peters,Gregory C. Ferdock,Maria B. Woitsekhowskaya,Robert Leonardson,Jerry Rahn.美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续)[J].地质找矿论丛,2000,(2):115-132 |
| 美国内华达Goldstrike矿区卡林型贝茨金矿同变形的富矿分带(续) |
| ORESHOOT ZONING IN THE CARLIN-TYPE BETZE OREBODY, GOLDSTRIKE MINE, EUREKA COUNTY, NEVADA |
| 投稿时间：1999-09-30 |
| DOI：10.6053/j.issn.1001-1412.2000.2. 003 |
| 中文关键词: 卡林型金矿 同变形 富矿分带 内华达 美国 |
| 英文关键词:Carlin type gold depopsit syndeformation oreshoot zoning Nevada U.S. |
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| The giant Betze gold ore body, the largest Carlin typ deposit known in the northcentral Carlin trend, Nevada is composed of individual high grade oreshoots that contain different geologic, mineralogic and textural characteristics. The orebody is typical of many structurally controlled Carlin type deposits, and is hosted in thin-bedded, impure carbonate or limy siltstone, breccia bodies, and intrussive or calc-silicate rock. Most ores in the Betze orebody are highly sheared and brecciated and show evidence of syndeformational hydrothermal deposition. Hydrothermal alteration is scale dependent, either in broad, pervassive alteration patterns or in areas related to various oreshoots. Alteration includes decarbonitization(~decalcification) of carbonate units, argillization(illite clay), and silicification. Patterns of alteration zoning in and surrounding the Betze orebody define a large porous dilated volume of rock where high fluid flow predominated. Local restriction of alteration to narrow illite-and clay-rich selvages around unaltered marble of calc-silicate rock phacoids implies that fluid flow favored permeable structures and deformed zones. Gold mainly present as disseminated sub-micron-sized particles, commonly associated with As-rich pyrite although one type of oreshoot contais micron-size free gold. Oreshoots form a three dimensional zoning pattern in the orebody within a WNW-striking structural zone of shearing and shear foloding, termed the Dillon deformation zone(DDN). Main types of oreshoots are;(1)rutile bearing siliceous oreshoots; (2)illite-clay-pyrite oreshoots; (3)realgar-and orpiment-bearing oreshoots; (4)stibnite-bearing siliceous oreshoots; (5)polymetallic oreshoots. Ore textures, gouge. phylloitic rock, alteration style and previously documented isotopic and fluid inclusion data, all indicate a weakly to moderately saline fluid that ascended and cooled during structural displacement. Carlin-type deposits are characterized by relatively uniform, low gold grades. However, recent open pit exposures in deep hypogene parts of the Betze orebody and other gold deposits in the Carlin trend suggest that some orebodies are composed of distinct high-grade oreshoots that are zoned complexly in three dimensions. |
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