中文摘要:在世界各大锡矿区中普遍存在矽卡岩型锡矿床和锡石硫化物矿床共生的现象,且前者靠近花岗岩接触带,后者产出于矽卡岩之外的大理岩或大理岩化灰岩中。为探讨这一成矿机制,笔者模拟了柿竹园锡矿的形成条件,进行了实验研究。实验表明,在高温矽卡岩阶段成矿溶
液中的锡大部分被石榴石等造岩矿物所捕获,或生成锡的钙硅酸盐矿物马来亚石,只有在相当于晚期矽卡岩阶段或石英硫化物阶段的温度条件下,溶液中的锡才以锡石形式晶出,出现锡石一石英一硫化物组合。由此,笔者认为温度是控制这类矿床的主要因素。
Abstract:Located at the contact of Qianlishan Yamshanian granite with Devonian limestone(Fig.1), the Shizhuyan tungsten, tin, molybdenum and bismuth skarn deposit is composed mainly of andradite, hedenbergite hornblende, vesuvianite, wolframite, scheelite and some sulfides, with no cassiterite visible in thin sections. Distribution-equilibrium calculations of tin in ores show that about 65 percent of tin is dispersed in garnet which has a tin concentration range from 0.1% to 0.394%, whereas only less than 15 percent of tin is present in cassiterite(Table 1, Fig.2). Electron probe and chemical analyses reveal that isomorph is the main occurrence mode of tin in garnet. Results of experimentation imitating the formation conditions of the skarn in this ore district are given in Table 4. Some skarn minerals such as andradite, hedenbergite, malayaite and magnetite were synthesized in these experiments. The synthetic andradite may contain up to 5.1 4% SnO2, a component which is evenly distributed in their lattice(Photos 3-4). The experiments show that, at the high temperature skarnization stage, silicon oxide, as an active component, tends to combine with calcium and iron to form andradites which will capture tin ions in ore-forming solutions. In solutions with high tin concentrations, excessive tin will prefer to form malayaite, a silicate of tin and calcium, rather than form cassiterite. At the late-skarn stage or the quartz-sulfide stage, however, silicon oxide will become all inert component, and garnet and malayaite will not be formed, thus resulting in the possible appearance of cassiterite-quartz assemblage.
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陈骏,吴厚泽.1988.柿竹园矽卡岩型钨锡钼铋矿床成矿实验研究[J].矿床地质,7(1):32~41.1988.Imitation experimentation on the Shizhuyuan tungsten, tin, molybdenum and bismuth skarn deposit in southeastern Hunan province[J].Mineral Deposits7(1):32~41
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