| 湖南锑矿成因探讨 |
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| 引用本文：.1984.An Investigation Into The Genesis Of The Antimony Deposits In Hunan[J].Mineral Deposits,3(3):13~26 |
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| An Investigation Into The Genesis Of The Antimony Deposits In Hunan |
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| Abstract:The antimony deposits in Hunan occupy an important place in antimony resources both in China and i71 the whole world. Twenty antimony deposits of different sizes have been discovered in this province which might be grouped into simple type (e.g. the Xikuangshan deposit) and complex type (e.g. the Woxi deposit). Ore bodies are mainly bedded, stratoid and occasionally veinlike in appearance. Wall rock alterations are quite simple. Some knowledge has been acquired about the genesis of antimony deposits in Hunan through the authors years of field work and looking into a great abundance of data The major characteristics of antimony deposits in Hunan can be summarized as follows: No intrusive body of significant size has been found in the main antimony prospects, indicating the nonexistence of obvious spatial and genetic relations between mineralization and magmatic rocks; Distributed in groups. the ore zones and ore deposits are confined respectively to pre-Sinian Xuefeng folded belt, Caledonian folded belt, Indo-Sinian folded belt and their subordinate structures; The ore deposits occur mainly in Devonian strata (possessing 67% of the discovered reserves), and secondarily in pre-Sinian, Sinian and Cambrian strata; ore-bearing wall rocks are predominantly carbonate rocks (containing 67% of the discovered reserves) and, to a less importance, slate and some other rocks; Ore-bearing strata have antimony abundances tens to hundreds times higher than antimony abundance in the earths crust; for example, Devonian Shetianquao Formation contains averagely 47—＞100 ppm Sb, Sinian slate has averagely 37.4 ppm, and pre-Sinian slate possesses 5—l000 ppm. This implies that strata might serve as ore sources of antimony. Stibnite in the Xikuangshan deposit contains similar sorts of minor elements as the wall rocks, though their contents are different. Pyrite from the Xikuaxigshan and Woxi deposits is characterized by Co/Ni ＜1, S/Se＞ 400,000, and that from the Xikuangshan and Longshan deposits by Sr/Ba ratios<1, suggesting sedimentary origin of these deposits; 242 sulfur isotope samples from different strata of 10 prospects gave δS34 values ranging from -32 to +16‰ with the values in a single deposit varying generally in the range of -10— +i0‰； these dispersed values suggest the participation of sulfur from the strata; Calcite of late mineralization stage in the Xikuangshan deposit has δC13 values of +0.18— +2.64‰, exhibiting the derivation of carbon from the seafacies limestone； In the Xikuangshan deposit, δO18 values of ore-bearing quartz are -0.69— +5.47‰ andδO18 values of calcite are -1.83 — +6.93‰, indicating a hot brine nature; in the Woxi deposit, δO18 values of quartz are +6— +13‰, δD values are -81 — -44‰, implying the nature of hot brine and metamorphic water; According to Stacey's two stage lead model ages, lead in the antimony ore of the Longshan deposit has an age of 900 m.y., which is older than the age of Sinian wall rocks (about 700 m.y. old), suggesting that lead in the ore-forming materials probably came from the underlying strata; Quartz associated with stibnite has a great many of minute inclusions (＜5 um). Of them, though pure liquid phase ones-are frequently seen, gaseous-liquid phase ones are dominant with gas/liquid ratios of 5-15%. These inclusions possess relatively high salinities (generally 7-19 wt%, some even reaching 30 wt%) and have homogeneous temperatures between 250℃ and 85℃. Inclusion components are of Na-Ca-Cl type for the Xikuangshan and Woxi deposits, and are of Na-K-Ca-CI type for the Longshan deposit, revealing a hot brine nature of the ore-forming fluids. One may clearly see from the foregoing descriptions that antimony deposits in Huuan have both characteristics of syzngenetic sedimentation and hot brine deposition, and that ore source bed, structure 'and hydrothermal fluids are three, indispensable prerequisites for ore deposition. Antimony deposits in Hunan, therefore, belong to stratabound ones of sedimentary-transformed type. |
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