新疆西准噶尔中基性岩墙的年代学和地球化学研究

Carboniferous to Permian is a critical period for tectonic evolution and ore-forming processes of the Central Asian Orogenic Belt. However, as a key to understand the evolution of the CAOB, metallogenetic geodynamic setting is still hotly debated. The extensively exposed late Paleozoic mafic-intermediate dikes in the West Junggar are pivotal in understanding the tectonic evolution and ore-forming setting of this area. However, these dikes have not been well dated because of the absence of isotopic age data with high precision. High precision Ar-Ar dating of hornblende provides a chance to solve the age problem of the mafic-intermediate dikes. These dikes in the West Junggar are composed of diabase, high-Mg diorite and low-Mg diorite. Recent petrology and geochemical studies have emphasized the diabase and low-Mg dioritic dikes limitedly exposed in Keramay. Meanwhile, the petrology and geochemistry of the diabase dikes in other areas and the high-Mg dioritic dikes have not been well studied. In this project, we focus on the petrogeochemical studies on the mafic-intermediate dikes (especially high-Mg dioritic dikes) in the West Junggar. Ar-Ar dating of hornblende, petrology and geochemistry are used to constrain the crystallization age, petrogenesis and tectonic setting of these mafic-intermediate dikes, which will shed light on the tectonic evolution and geodynamics of the West Junggar during the Carboniferous and early Permian.

石炭-二叠纪是中亚造山带构造演化和成矿作用的一个关键时期，但对这一关键时期的地球动力学背景仍然存在着争议。西准地区出露有大量晚古生代的岩墙，是了解该区成矿背景和构造演化的重要窗口。前人用锆石U-Pb、Rb-Sr等时线、全岩Ar-Ar和K-Ar法对岩墙进行测年，缺乏高精度的定年数据。角闪石Ar-Ar测年为解决中基性岩墙定年这一难题提供可能。此外，这些岩墙由高Mg、低Mg、辉绿质岩石组成。已有的岩石学和地球化学研究主要针对辉绿岩和低Mg闪长质岩墙，且仅仅局限在克拉玛依地区。而对西准噶尔的其它地区的岩墙以及克拉玛依地区的高Mg质岩墙的岩石学和地球化学研究是相对缺乏的。本项目拟以西准地区中基性岩墙（尤其高镁质岩墙）为研究对象，对其开展角闪石Ar-Ar测年，结合岩石学和地球化学研究，有望制约中基性岩墙的结晶年龄、岩石成因以及构造背景，揭示西准地区石炭纪-早二叠纪的构造演化和地球动力学过程。

石炭-二叠纪是中亚造山带构造演化和成矿作用的一个关键时期，但对这一关键时期的地球动力学背景仍然存在着争议。本项目以西准准噶尔晚古生代的中-基性岩墙和花岗岩为研究对象，开展岩石学、年代学、元素地球化学和Sr-Nd-Hf同位素研究。研究中基性岩墙和花岗岩的年龄、岩浆源区，分析其岩石成因，进而探讨中基性岩墙和花岗岩形成的动力学机制及其对大陆地壳生的启示。取得了如下重要成果：（1）厘定西准噶尔南部岩墙的岩石组合，形成时限，提出洋脊俯冲在中亚造山带大陆地壳生长中发挥了重要作用；（2）厘定西准噶尔晚古生代两类赞岐岩的成因机制；（3）对西准噶尔北部早石炭世的构造演化提出新的认识。（4）厘定西准噶尔地区晚古生代花岗岩形成时限和构造环境。(5) 厘定西准噶尔早-晚古生代过渡期侵入岩的岩石组合、形成时限，提出板片回撤模式来解释其动力学过程。以第一作者身份在Lithos，Tectonophysics和Gondwana Research等刊物发表论文10篇。