南秦岭竹山混杂带的成因和形成时代研究

The east extension features of Mianlue tectonic belt, which is regarded as an important and controversial geological problem, is very significative for determining the nature of Mianlue tectonic belt and the tectonic attribution of South Qinling-Dabie orogenic belt. The extension of Mianlue belt between Daba mountain and Sanligang in Shuizhou has not yet been determined for a long time, and Zhushan melange belt provides a new way for solving this key problem. In this study, base on theory of mélange and tectonic facies, after systematic observing of petrotectonic assemblage and structural deformation, the genesis and formation age of Zhushan mélange belt is planning to be ascertained by using the methods of structural geology, isotope chronology and geochemistry. This study will provide new important informations and geological evidences for the reasonable interpretation tectonic evolution of Southern Qinling orogenic belt and the regional mineralization rule in Wudang-Tongbai-Dabie metallogenic belt.

勉略构造带的东延特征是一个十分重要但又存在较大争议的地质问题，对于研究该构造带的性质以及南秦岭—大别造山带的大地构造属性具有十分突出的意义。勉略带由大巴山向东至随州三里岗之间如何衔接，一直没有定论，竹山混杂岩带为解决这一关键问题提供了新的思路。本申请拟以南秦岭竹山混杂带为研究对象，运用混杂带研究的新理论和大地构造相的方法为指导，查明竹山混杂带的岩石组合类型和构造关系，在此基础上，进行构造地质学、同位素年代学和地球化学研究，旨在确定竹山混杂带的成因和形成时代，为下一步探讨其大地构造背景和构造演化服务。这不仅为探讨南秦岭造山带大地构造演化过程提供重要的新的信息，亦可为武当—桐柏—大别成矿带的找矿工作提供新的思路。

项目以南秦岭竹山混杂带为研究对象，通过详细的野外地质调查和重要地区大比例尺地质填图，查清竹山混杂带中基质和岩块的岩石组合类型和构造变形样式；在此基础上，运用沉积学、古生物地层学、构造地质学、地球化学、Hf同位素和锆石LA-ICP-MS或SHRIMP U-Pb测年等进行综合研究，确定竹山混杂带中基质和岩块的成因和形成时代，为下一步探讨其大地构造背景和构造演化服务。在项目研究过程中取得如下成果：.1、对竹山混杂带内物质组成进行甄别和细分，识别出主要的构造岩片填图单位；.2、通过同位素年代学对玄武岩岩块、变辉长岩岩块、酸性火山岩岩块、碱性火山岩岩块的形成时限进行约束；.3、通过同位素年代学竹山混杂带内基质形成时代进行约束；.4、初步确定竹山混杂带的成因及东延特征；并在此基础上探讨了其大地构造背景和成矿意义。