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| 桂西北明山卡林型金矿床热液矿物的显微组构与化学成分特征及其对成矿作用的指示 | |
| 引用本文： | 庞保成,肖海,付伟,张青伟,陈宏毅.桂西北明山卡林型金矿床热液矿物的显微组构与化学成分特征及其对成矿作用的指示[J].吉林大学学报(地球科学版),2014,44(1):105. |
| 作者姓名： | 庞保成 肖海 付伟 张青伟 陈宏毅 |
| 作者单位： | 1.桂林理工大学广西矿冶与环境科学实验中心，广西 桂林541004; 2.桂林理工大学广西隐伏金属矿产勘查重点实验室，广西 桂林541004; 3.桂林理工大学地球科学学院，广西 桂林541004 |
| 基金项目： | 广西自然科学基金项目(2012GXNSFAA053187,2013GXNSFAA019275);广西科技基础条件平台建设项目(11-031-20) |
| 摘 要： | 桂西北明山金矿是滇黔桂地区代表性的卡林型金矿之一，矿体受平行于区域性断裂右江断裂的北西西向次级断层控制，赋存于二叠系灰岩之上的中三叠统钙质细砂岩、碳钙质泥质粉砂质岩中。地质、岩相学特征和阴极发光、背散射电子影像、电子探针等分析研究表明，明山金矿发育了3个成矿阶段的热液矿物组合，不同热液矿物普遍具有多世代的特点。热液矿物中见有波状消光、带状消光、毕姆纹、压溶劈理、位错滑移等韧性剪切带粒内应变特征，坑道中也见有黄铁矿石英脉发生韧性变形、又被后期石英脉切断的现象，说明矿床经历了多次的脆-韧性变形。不同矿化期（阶段）的黄铁矿中Au和As的含量表明:沉积期黄铁矿Au、As的含量较低；成岩期黄铁矿中Au的含量高但As含量不高；而成矿期3个阶段的热液黄铁矿中都含较高的As和Au；热液黄铁矿核部包裹的交代残余黄铁矿Au、As含量较高，但变化范围较大，可能是变质成因。紧邻矿体的围岩中成岩黄铁矿从中心向外Au和As的含量逐渐降低，说明其中的As和Au在后来的构造和（或）热液事件中发生了活化迁移，越靠近颗粒边缘元素的活化迁移越强，这表明成矿物质来自于围岩。根据这些事实，推断明山矿区可能在成岩期发生了金的预富集，变形变质早期富含有机质的变质流体活动又使As发生了富集，主变质期流体的广泛渗透交代、活化出先存含金富砷黄铁矿中的Au和As，形成成矿流体。当成矿流体遇到富含活性铁的炭钙质泥质粉砂岩时，形成黄铁矿的同时发生Au的沉淀。 |
| 关 键 词： | 卡林型金矿 热液矿物 显微组构 变质作用 成矿作用 桂西北 |
| 收稿时间： | 2013-08-21 |
Microfabric and Composition of Hydrothermal Minerals from the Mingshan Carlin Gold Deposit in Northwestern Guangxi and Their Implication for Ore-Forming Process |
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| Pang Baocheng,Xiao Hai,Fu Wei,Zhang Qingwei,Chen Hongyi.Microfabric and Composition of Hydrothermal Minerals from the Mingshan Carlin Gold Deposit in Northwestern Guangxi and Their Implication for Ore-Forming Process[J].Journal of Jilin Unviersity:Earth Science Edition,2014,44(1):105. | |
| Authors: | Pang Baocheng Xiao Hai Fu Wei Zhang Qingwei Chen Hongyi |
| Institution: | 1.Guangxi Scientific Experiment Center of Mining, Metallurgy and Environment，Guilin University of Technology, Guilin541004, Guangxi，China; 2.Guangxi Key Laboratory of Hidden Metallic Ore Deposit Exploration, Guilin University of Technology, Guilin541004, Guangxi，China; 3.College of Earth Sciences, Guilin University of Technology, Guilin541004, Guangxi，China |
| Abstract: | The Mingshan gold deposit is related to NWW-trending faults that parallel to the regional Youjiang fault and hosted within the Middle Triassic calcareous argillaceous siltstone. Field work, petrography, cathodoluminescence, back scatter electron imaging and electron microprobe data indicate that hydrothermal minerals in Mingshan gold deposit can be classified into three forming stages. Most of these minerals have multiple generations. Hydrothermal minerals are featured by such as ductile intragranular characteristics as undulatory extinction, banded extinction, Behm lamellae, pressure solution of cleavage and dislocation glide. In the adit, pyrite-bearing quartz veins are characterized by ductile reformation and cut by later quartz veins, which indicates the deposit are influenced by multiphase brittle-ductile reformation. Au and As contents in the pyrite formed in different stage have regular patterns, i.e., there are lower Au and As content in the sedimentary pyrite. In contrary, there is higher Au content and lower As content in diagenesis pyrite. All three generation hydrothermal pyrites in the ore-forming period have abundant Au and As. The fact that the As content in relict pyrite in the core of banded pyrite is higher than those in diagenesis pyrites indicates that the relict pyrite is different in origin from diagenesis pyrite. The relict pyrite maybe belongs to the metamorphic genesis. As and Au contents in the diagenetic pyrite from country rocks near orebody decrease from center to edge, which suggests that elements of As and Au in the ore may have been derived from the country rocks. Based on these data, it can be deduced that there developed gold pre-enrichment in diagenetic stage, and enrichment of As element is caused by organic metamorphic fluid during the early reformation and metamorphism. During the major metamorphic period, wide infiltration metasomatism of the fluid caused the activation of Au and As from the gold-bearing and arsenic rich pyrite, which resulted in the formation of ore-forming fluid. When the ore-forming fluid met carbon calcareous argillaceous siltstone bearing the active iron, gold precipitated accompanying with the pyrite. These suggest that the metamorphic fluids may have played very important role in the formation of the Mingshan gold deposit. |
| Keywords: | Carlin gold deposit hydrothermal minerals microfabric metamorphism ore-forming process northwestern Guangxi |
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