桂东北志留纪花岗岩W-Mo-Cu-Pb-Zn成矿作用及其地质背景研究

It is generally believed that the Caledonian granitoids in south China contributed little in metallogic mineralization. However, recent discoveries of several large-scale Caledonian W-Mo deposits in south China make us rethink Caledonian mineralization and ask several important questions. For example, what is the difference between the Caledonian mineralization and the Yanshanian massive W-Sn mineralization? Was there any contribution from mantle material to the Caledonian mineralization and how? These questions become important scientific questions that need to be answered. In this proposal, we will investigate several deposits located in northeastern Guangxi, such as Jiepai W-Cu, Niutangjie W, Baishiding Mo, and Zhanggongling Pb-Zn deposits. Their timing of granitic emplacement and mineralization will be determined with high-precision geochronological methods. Nd-Sr-Pb and zircon Hf-O isotopic analyses of the granitoids and their enclaves and trace elemental analysis of the granitoids will be performed to delineate their contribution to the mineralization. S, Pb, and O isotopic analyses of ore minerals, as well as O and H isotopic analyses of hydrous minerals will be also performed to trace sources of metals and fluids. Indicator minerals such as scheelite will be studied to reveal evolution history of ore-forming elements. Single fluid inclusions and SEM-CL technology will be utilized to characterize ore fluid evolution of different ore-forming element associations and their mineralization mechanisms. The goal is aimed at revealing metallogenic specialization of the Caledonian granitoids and constrains of granitic magmatic process on the mineralization, and at answering the question of why granitic metallogenic process was peaked at the Silurian time of the Caledonian.

以前研究认为华南加里东期花岗岩一般不成矿。然而近年来加里东期W-Mo大型矿床的发现促使人们重新思考这个问题。加里东期花岗岩志留纪成矿的原因何在？地幔（或深部）物质对成岩成矿的贡献如何？是一个悬而未决的重要科学问题。申请人拟以桂东北界牌W-Cu矿、牛塘界W矿、白石顶Mo矿和张公岭Pb-Zn矿为研究对象，在精确厘定成岩成矿时代的基础上，利用岩石（包体）Nd-Sr-Pb-Li同位素和锆石Hf-O同位素和微量元素示踪深部岩浆作用对成矿的制约；利用矿石矿物S、Pb、O同位素以及含水矿物的O、H同位素示踪成矿物质和成矿流体来源；利用指示矿物（如白钨矿等）示踪成矿元素的迁移演化历史；利用单个流体包裹体和SEM-CL技术示踪不同成矿元素组合成矿流体演化特点及成矿机制的差异性。最终揭示加里东期花岗岩的成矿专属性以及深部岩浆作用对成矿的关键制约因素，探讨其志留纪集中成矿的原因及其在华南区域成矿中的地位。

以前研究认为华南加里东期花岗岩一般不成矿,人们比较着重燕山期花岗岩成矿作用的研究，而对加里东期和印支期花岗岩的成矿作用研究相对较少，甚至认为加里东期花岗岩即使成矿也不具有重要的经济意义。近年来，随着一系列与加里东期和印支期花岗岩有关的W-Mo 矿床的相继发现，该地区加里东期花岗岩的成矿作用逐渐得到人们的重视。加里东期花岗岩志留纪成矿的原因何在？地幔（或深部）物质是否成岩成矿有贡献？这些问题制约了对花岗岩成矿的认识。项目以桂东北界牌W-Cu 矿、牛塘界W 矿、白石顶Mo 矿和张公岭Pb-Zn 矿为研究对象，开展成岩成矿年代学、深部岩浆作用对成矿的控制，成矿物质和成矿流体来源的研究。取得的主要成果如下：（1）厘定了桂东北地区越城岭地区复杂的岩浆-构造-热液活动演化历史与W-Mo-Cu-Pb-Zn多阶段成矿作用。该地区主要存在晚奥陶世、早志留世、晚三叠世、晚侏罗世等多时代的花岗岩和相应的成矿作用，同时还存在白垩世的岩浆热液事件；发现苗儿山地区同样存在多种类型的金属成矿作用，但花岗岩的类型、时代及其与成矿的关系尚需进一步研究。（2）提出了桂东北地区花岗岩地质地球化学数据不支持该地区存在早志留世洋陆俯冲的观点，该地区加里东期主要为陆内造山运动。（3）查明了界牌铜钨矿床和牛塘界铜钨矿床层间夕卡岩是热液流体交代的结果，可能与韧性剪切变质变形作用有关；（4）探讨了桂东北地区加里东期花岗岩的成因与成矿的耦合关系。发现该地区加里东期花岗岩及其成矿具有明显的地域性；加里东期基性岩浆参与成岩成矿的程度和方式明显不同，因而成矿的类型也明显不同（如桂岭岩体白石顶Mo-W矿床、界牌W-Cu矿床等）；虽然越城岭和苗儿山地区花岗岩主体为加里东期花岗岩，但是由于晚期花岗岩侵入的类型不同，因而与之成矿类型也明显不同。.项目共发表科学论文8篇，其中国际SCI论文3篇。培养博士后1名，博士生1名，硕士生2名。