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引用本文:姚晓峰1,2 叶天竺1 唐菊兴3 郑文宝3 丁 帅4 李永胜1 甄世民1. 西藏甲玛矿床硅钙界面对矽卡岩成岩及多金属成矿的影响[J]. 中国地质, 2014, 41(5): 1577-1593.
YAO Xiao-feng1, 2, YE Tian-zhu1, TANG Jv-xing3, ZHENG Wen-bao3, DING Shuai4, LI Yong-sheng1, ZHENG Shi-min1. The effect of Si-Ca interface on skarn formation and pollymetallic mineralization in the Jiama deposit, Tibet[J]. Geology in China, 2014, 41(5): 1577-1593(in Chinese with English abstract).
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西藏甲玛矿床硅钙界面对矽卡岩成岩及多金属成矿的影响
姚晓峰1,2 叶天竺1 唐菊兴3 郑文宝3 丁 帅4 李永胜1 甄世民11,2,3,4
1.中国地质调查局发展研究中心, 北京 100037;2.中国地质大学(北京), 北京 100083;3.中国地质科学院矿产资源研究所, 国土资源部成矿作用与资源评价重点实验室, 北京 100037;4.成都理工大学地球科学学院, 四川 成都 610059
摘要:
提要:西藏甲玛铜多金属矿床为冈底斯成矿带的超大型矿床之一, 其矽卡岩型主矿体受林布宗组砂板岩、角岩(硅铝质岩石)和多底沟组大理岩(钙质岩石)的岩性界面所控制。基于岩、矿心地质编录, 开展矽卡岩岩石、矿物分带及矽卡岩地球化学、矿物化学研究, 探讨硅钙岩性界面对矽卡岩及多金属矿体形成的影响。从顶板至底板由石榴子石矽卡岩、硅灰石石榴子石矽卡岩至硅灰石矽卡岩表现出SiO2、CaO逐渐增加和Al2O3、Fe2O3+FeO逐渐减少的趋势, 石榴子石矽卡岩、硅灰石矽卡岩的稀土元素和微量元素特征对顶板、底板岩石表现出明显的继承性。靠近顶板的矽卡岩中石榴子石属于钙铝-钙铁过渡系列, 由石榴石核部向外环带具有Al含量减少、Fe含量增加的特点; 靠近底板矽卡岩相对于靠近顶板具有钙铁榴石比例增加、钙铝榴石比例减少特征, 由核部向外围未见明显的环带成分演变特征。矽卡岩是流体与硅铝质、钙质岩石水岩反应的产物, 沿硅钙界面流体减压沸腾、地下水混合作用和界面内垂向的流体地球化学障是主要的致矿机制。硅、铝质岩石化学性质、物理性质差异是界面控矿的主要因素, 硅钙面复合张性构造带、岩浆热事件增加界面渗透率差异有利于矿体规模的增加和品位提高。
关键词:  甲玛  硅钙界面  矽卡岩  岩石地球化学  矿物化学  成矿作用
DOI:
分类号:
基金项目:中国地质调查局西藏大型矿床成矿专属性研究(资[2012]03-002-055) 、重点成矿区带矿产勘查跟踪与成果集成研究 (1212011085534)、青藏专项(1212010818089)、全国地质勘查进展分析(1212011121126)联合资助。
The effect of Si-Ca interface on skarn formation and pollymetallic mineralization in the Jiama deposit, Tibet
YAO Xiao-feng1, 2, YE Tian-zhu1, TANG Jv-xing3, ZHENG Wen-bao3, DING Shuai4, LI Yong-sheng1, ZHENG Shi-min11,2,3,4
1. Development Research Center, China Geological Survey, Beijing 100037, China;2. China University of Geosciences, Beijing 100083, China;3. Key Laboratory of Metallogeny and Mineral Assessment of Ministry of Land and Resources, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;4. Chengdu University of Technology, Chengdu 610059, Sichuan, China
Abstract:
Abstract: The Jiama deposit is a superlarge copper-polymetallic deposit inGangdise metallogenic belt in Tibet, and its main skarn type orebody is distributed along the interface between Early Cretaceous Linbuzong Formation hornfels (salic) and Late Jurassic Duodigou Formation marble (calc). Based on the zonation of skarn between the Si-Ca interface, the authors studied petrological geochemistry and mineral chemistry of skarns in different zones, with the purpose of studying the effect of Si-Ca interface on the formation of skarn and orebody. It is shown that the values of SiO2 and CaO increase and the values of Al2O3 and TFe decrease downwards from garnet skarn through garnet wollastonite skarn to wollastonite skarn along the interface belt. The rare and trace elements geochemical characteristics of garnet skarn and wollastonite skarn are restricted by hornfels and marble respectively. Garnets within skarn near the roof of the Si-Ca interface are transition series between grossular and allochroite, in which values of Al decrease and values of Fe increase from core outwards, while garnets within skarn near the bottom of the interface have more Fe values and less Al content than the former garnet series, in which values of Al and Fe change a bit from core outwards. Skarns are hydrothermal reaction products through alteration of salic and calc rocks. Fluid decompression boiling and groundwater mixing along the Si-Ca interface and vertical fluid geochemical barrier along the interface belt seem to have been the main factors influencing orebody formation in the Jiama deposit. The difference of chemistry and physical characteristics between salic and calc rocks had important effect on the ore-forming process along Si-Ca interface. The interface overlap extension structure and magmatic thermal event that increased permeability from roof to bottom along the interface belt contributed to the scale increase and grade enrichment of the orebody.
Key words:  Jiama  Si-Ca interface  skarn  petrological geochemistry  mineral chemistry  ore-forming process