| 四川东北寨微细浸染型金矿床成矿物理化学条件和成矿过程分析 |
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| 引用本文：.1990.An analysis of metallogenic physicochemical conditions and metallogenic processes of the Dongbeizhai micro-disseminated gold deposit in Sichuan province[J].Mineral Deposits,9(2):129~140 |
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| 中文摘要:东北寨金矿床是产于碳酸盐岩一碎屑岩建造中的微细浸染型（卡林型）金矿床。矿化严格受控于垮石崖断裂下盘富含有机质和成岩黄铁矿的黑色岩系地层。包裹体研究和热力学计算表明，成矿温度为220—120℃，压力为4.05×107—3.04 ×107pa，形成深度小于2km。成矿流体具弱酸一弱碱性、还原性较强和Cl-活度较低等特点。矿源层中的金以硫氢络合物Au(HS)2-形式活化进入溶液，促使金沉淀富集的机制是溶液中总硫活度的降低、氧逸度的下降和有机质的还原吸附作用等。矿床形成包括四个阶段。 |
| 中文关键词:微细浸染型金矿床 物理化学条件 成矿过程 东北寨 |
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| An analysis of metallogenic physicochemical conditions and metallogenic processes of the Dongbeizhai micro-disseminated gold deposit in Sichuan province |
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| Abstract:The Dongbeizhai gold deposit is a micro-disseminated(Carlin type)one which is hosVed by slightly metamorphosed sedimentary rocks. The orebodies are confined in the black sedimentary formation which serves as the footwall of the Kuashiya thrust fault. The footwall rocks rich in organic matter and diagenetic pyrite are overlain by carbonate rocks that form the hanging wall of the fault and also the soIzrce bed. Fluid inclusion studies and thermodynamic calculations indicate that ternperatures for ore deposition were from 220℃ to 120℃, pressures from 400 to 300 bar, and depth not in excess of 2 km. Ore forming solutions were weakly acid to weakly basic, relatively I'eduetive and low in Cl- activity. The gold in source rocks was mobilized and entered the convecting meteoric Water through the following chemical reaction：Au+H2S+MS- =Au(HS)2-+1/2H2 and migrated as the hydrosulfide complex Au(HS)2-. A decrease in reduced sulfur activity caused by deposition of sulfides such as pyrite, realgar and stibnite in hydrothermal oze solutions and a depline in O2 fngacity as well as the reduction and absorption of organic matter were the effective mechanism responsible for gold deposition. The metallogenic process of the Dongbeizhai gold deposit can be summarized as follows: (1) the formation of carbonate and clastic sedimentary rocks zich in organic matter and dilagenetic pyrite, the development of thrust faults and the intrusion of subvolcanic dikes; (2) the increase in geother-real gradient, the convection of heated meteoric water, the mobilization of metallogenic elements and the formation of ore-forming solutions; (3) the variation in physIicochemical conditions and the precipitation of gold in fracture zones and /or suitable rocks; and(4)the erosion and slight oxid ation of the upper orebodies after ore formation. |
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