中国阿尔泰造山带多期次变质-变形组构形成和演化研究

Deciphering the deformational-metamorphic evolution of internal orogenic fabrics is key to the understanding of the dynamic evolution of the Central Asian Orogenic Belt (CAOB). The Chinese Altai Orogenic Belt, located in the heartland of the CAOB, is characterized by the occurrence of a series of metamorphic zones, metamorphosed at greenschist- to granulite-facies conditions, with multiple generations of deformation. Such polyphase petro-structural features make the region perfect for understanding the complicated tectonothermal processes of the CAOB. This region has been the subject of considerable geochemical research in recent years and great progresses have been achieved. However, the deformational history and associated metamorphic evolution in this region has not been investigated in sufficient depth, which hinder a precise reconstruction of the tectonothermal evolution of the region. The proposed project will focus on links between deformational and metamorphic evolution of the Chinese Altai. The development of metamorphic fabrics associated with orogenic deformational episodes will be further studied by integrating critical data from structural observations, petrographic studies, equilibrium modeling as well as geochronological analyses. The project aims (i) to decipher the deformational patterns, mineral growth sequences, and genetic relationships between deformation and metamorphism, (ii) to provide age constraints on the related deformational episodes and/or metamorphic cycles, (iii) to resolve the pressure-temperature-time-deformation (P-T-t-D) paths for important metamorphic sequences, and (iv) to establish a comprehensive mode for the tectonometamorphic evolution for the region. The proposed project will significantly contribute to better understanding of the tectonic evolution of the Altai orogenic belt and greatly promote our understanding of the orogenic processes of the CAOB.

对造山带内部构造变形-变质演化开展深入研究，是揭示中亚造山带动力学演化过程的关键。位于中亚腹地的中国阿尔泰造山带，以多期次构造变形-变质作用为特征，是认识中亚造山带构造-热演化的一个重要窗口。近年来该区域在地球化学研究方面取得了令人可喜的进展，然而对多期次构造变形-变质作用的解译相对滞后，严重阻碍其构造-热演化重建工作的深入开展。本项目将立足于构造变形分析和变质岩石学研究，结合相平衡计算及同位素测年，对中国阿尔泰变质演化和构造变形开展系统研究。本项研究的特色是从变质-变形组构形成和演化的角度，来探究变质作用演化和构造变形的关系，以期建立区域构造变形框架，明确变质矿物组合和变形期次的关系，限定不同变质-变形期次的时代并获得其P-T-t-D演化轨迹，从而探究区内变质作用的成因机制及揭示多期次构造-热事件的历史，为重建整体阿尔泰造山带演化及理解中亚造山带内部造山过程提供重要制约。

造山带的形成和演化是地球科学研究的基本内容。变质岩记录了造山作用过程中复杂的物理化学过程，是造山动力学过程重建的核心研究对象。将变质作用与变形过程相匹配，是变质作用研究服务于造山动力学过程解析的重要趋势，但仍是全球范围内造山带研究的薄弱环节。位于中亚腹地的中国阿尔泰造山带，以多期次构造变形-变质作用为特征，是认识中亚造山带构造-热演化的一个重要窗口。由于在变质作用研究方面缺乏变质变形综合研究，使得该区域古生代构造-热演化重建工作难以深入开展。本项目以变质岩石学融合构造变形分析为基础，结合变质相平衡计算及同位素测年，对中国阿尔泰变质演化和构造变形开展了系统研究。项目取得了以下进展（1）明确了阿尔泰造山带的构造属性是增生楔而非微大陆，提出了蒙古增生体系发育于新元古-早古生代古太平洋构造域；（2）厘定了中国阿尔泰造山带变质组构的生长和演化与构造变形的对应关系及其形成时代，厘清了中国阿尔泰“中压型”与“高温低压型”变质组构的成因关联，构建了阿尔泰地区“多期次”构造热事件变质-变形过程和时空格局；（3）梳理了阿尔泰增生杂岩深熔作用与巨量花岗岩形成的因果关系，重塑了增生杂岩深熔与分异、深部物质的水平和垂向流动的动力学过程，揭示了造山带深熔-岩浆作用促成增生杂岩-成熟大陆地壳转换的内在机制。受项目资助，本研究团队共发表SCI论文10篇，中文核心2篇，研究成果为构建增生型造山带从俯冲增生、变质-变形改造到深熔花岗岩化的系统连续演化过程提供了参考范例。