CARRICK RANGE AU AND SB MINERALIZATION IN CAPLES TERRANE, OTAGO SCHIST, CENTRAL OTAGO, NEW-ZEALAND

被引：22

作者：

ASHLEY, PM ^{[1
]}

CRAW, D ^{[1
]}

机构：

[1] UNIV OTAGO,DEPT GEOL,DUNEDIN,NEW ZEALAND

来源：

NEW ZEALAND JOURNAL OF GEOLOGY AND GEOPHYSICS | 1995年 / 38卷 / 02期

关键词：

GOLD; STIBNITE; CARRICK RANGE; OTAGO SCHIST; CAPLES TERRANE; ISOTOPES; FLUID INCLUSIONS;

D O I：

10.1080/00288306.1995.9514646

中图分类号：

P5 [地质学];

学科分类号：

0709 ; 081803 ;

摘要：

Mineralised zones of the Carrick Range, bearing gold and stibnite veins, constitute one of the rare economically significant mineralised fields in the Caples Terrane. The mineralised zones have a polyphase hydrothermal history. Early low-angle shears are filled by milky quartz, with minor carbonate, sulphides, and gold. These are cut by steeply dipping hydrothermal breccias and veins with prismatic and fine-grained chalcedonic quartz +/- carbonate (calcite and ankerite). Gold is associated with some high-angle mineralised zones, and stibnite with spatially separated but texturally similar high-angle zones. Fluid inclusions in early milky quartz homogenise mainly between 145 degrees and 210 degrees C, with some higher temperature homogenisation up to 300 degrees C. Late prismatic quartz has inclusions that homogenise at 150-170 degrees C, and ice-melting temperatures suggest low salinity (2.4-4.8 wt% NaCl equivalent). Oxygen isotopic ratios of early milky quartz range from delta(18)O = +15.4 to +17.6 parts per thousand, whereas fine-grained late quartz ranges from +13.4 to +22.8 parts per thousand. Vein carbonates have delta(18)O between +13.8 and +19.9 parts per thousand, and delta(13)C between -1.6 and -3.6 parts per thousand. The isotopic data, combined with other geological and mineralogical evidence, imply that mineralisation occurred over a wide range of temperature (140 degrees-400 degrees C) with a fluid of constant isotopic composition similar to typical Otago Schist metamorphic fluid. Sulphide sulphur isotopic ratios fall in a narrow range of delta(34)S = -1.6 to +2.6 parts per thousand, consistent with a homogenised crustal sulphur source. Late stage mineralisation occurred at shallow crustal levels (upper 2 km?), but earlier mineralisation was probably deeper. Mineralisation may have occurred sporadically, or as a continuous event during progressive uplift, during Cretaceous and/or early Miocene extensional tectonics.

引用

页码：137 / 149

页数：13

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