投稿时间：2023-06-20
修订日期：2023-11-05
网络发布日期：2023-12-29
中文摘要:位于海南岛西南部的抱伦金矿产于尖峰岩体外接触带，与辉绿岩脉密切伴生，这些侵入岩蕴含了金矿成矿作用与岩浆活动-构造演化-成矿体系关系的重要信息。文章报道了对抱伦尖峰花岗岩和辉绿岩开展岩石学、锆石U-Pb年代学、元素和Sm-Nd同位素地球化学研究的成果。本次工作获得了尖峰花岗岩的LA-ICP-MS方法锆石U-Pb年龄为(234.9±2.8) Ma，与辉绿岩构成双峰式侵入杂岩组合。辉绿岩属亚碱性玄武岩系列，相对富集Th、Nb、Ta等强不相容元素，无Nb、Ta、Ti亏损，显示与富集洋中脊玄武岩（E-MORB）相似的地球化学特征，其εNd (t)值为4.11，指示了亏损的源区性质；尖峰花岗岩属高钾钙碱性岩系的铝质A型花岗岩，相对富集K、Rb、Th、Ce等元素，相对亏损Sr、Ba、Nb、Ta、P、Ti等元素，其εNd (t)值为-7.61~-7.80，指示了再循环地壳源区。抱伦辉绿岩为交代型地幔降压熔融的产物，而尖峰花岗岩起源于中元古界泥质和杂砂岩地壳源岩于低压、高温环境下的部分熔融，该双峰式侵入杂岩与金成矿作用形成于造山后伸展-减薄构造背景。双峰式侵入杂岩的侵位分别提供了壳源、幔源成矿物质和运移载体，壳-幔源含矿岩浆热液沿白沙断裂上升，运移过程中不断萃取围岩成矿物质，导致成矿流体变为变质热液主导，最终在NNW向拉张性断层破碎带就位。导致金沉淀成矿的主要因素是含矿热液发生降压，归因于造山后伸展-减薄构造环境。区域牵引构造发育的部位是含矿热液运输通道和主要的成矿空间，应是深部找矿的主要勘查方向。
Abstract:The Baolun gold deposit in SW Hainan formed in the outer contact zone of the Jianfeng intrusive complex and is closely associated with diabase dyke in space, which contains important information about the magmatictectonic-metallogenic evolution system of the gold deposit. An integrated study of Petrology, zircon U-Pb geochronology, elemental and Sm-Nd isotope geochemistry was carried on the Jianfeng granite and diabase. The Jianfeng granite and diabase intrusions comprise a bimodal intrusive complex, and the granite intrusion was dated at (234.9±2.8)Ma by LA-ICP-MS method of zircon U-Pb. The diabase is sub-alkaline basaltic in composition, its REE pattern is generally right-inclined with weakly LREE enrichment. It is relatively enriched in highly incompatible elements of Th, Nb and Ta, and shows no depletion in HFSE of Nb, Ta and Ti. Along with its εNd(t) value of 4.11, it is suggestive of geochemical characteristics of enriched mid-ocean ridge basalt (E-MORB) for the diabase. The Jianfeng granite is high-K calc-alkaline with an affinity of aluminous A-type granite. Its REE pattern is highly right-inclined and its multi-elements spider pattern displays enrichment in K, Rb, Th, Ce, Y and Yb and depletion in Sr, Ba, Nb, Ta, P and Ti. Its εNd(t) values varied between -7.61~-7.80, indicative of recycled crust derivation. It is revealed that the Baolun diabase was derived from decompression melting of metasomatic mantle, whereas the Jianfeng granite was originated from the partial melting of the Middle Proterozoic argillaceous and greywacke crust under low pressure and high temperature. The bimodal intrusive magmatism and gold mineralization were formed in a tectonic setting of post-orogenic extensional-thinning. The bimodal magmatism provided both the crust- and mantle-derived ore-forming materials and migration carriers. The crust- and mantle-derived ore-bearing magmatic hydrothermal fluids are thought to have ascended along the Baisha fault. During this migration process, the ore-forming materials were continuously extracted from the country rocks, resulting in the oreforming fluid developed into a metamorphic affinity, and finally precipitated in the extensional zone of NNWtrending fault fractures. The key factors dominating the gold mineralization is depressurization, which is attributed to the post-orogenic extensional-thinning tectonic environment. It is suggested the regional traction structures were the ore-bearing hydrothermal transport channels and the main metallogenic locations, which are indicative of main prospecting direction of the deep mineralization in the region.
keywords:bimodal intrusive complex E-MORB aluminum A-type granite post orogenic extension-thinning Baolun gold deposit
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基金项目:本文得到海南省海洋地质资源与环境重点实验室开放课题（编号：HNHYDZZYHJKF014）、海南省自然科学基金（编号：421RC1109）和中国地质调查局项目（编号：1212011220710）联合资助
引用文本：
林弟,宛胜,胡在龙,吕常艳,单强,梁晓,魏昌欣,袁勤敏,高鹏.2023.海南岛抱伦金矿床双峰式侵入杂岩地球化学特征及对金成矿作用的启示[J].矿床地质,42(6):1229~1246LIN Di,WAN Sheng,HU ZaiLong,LÜ ChangYan,SHAN Qiang,LIANG Xiao,WEI ChangXin,YUAN QinMin,GAO Peng.2023.Geochemical characteristics of bimodal intrusive complex in Baolun gold deposit, Hainan island and its implications for regional gold mineralization[J].Mineral Deposits42(6):1229~1246
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