董岭杂岩的物质组成、形成时代及其对扬子陆块前寒武纪地壳演化的启示

The Dongling complex occurs in the Middle-Lower Yangtze Metallogenic Belt, NW Yangtze Block. It has long been considered as a counterpart of the Kongling complex from the central Yangtze Block. However, little is known about the age, genesis, and tectonic setting of the Dongling complex, hampering our understanding of the Precambrian crustal evolution of the Yangtze Block, and petrogenesis of the Mesozoic igneous rocks and formation of magma-related ore deposits over the Middle-Lower Yangtze Metallogenic Belt. .In this proposal, we aim to conduct an intensive study on the field relationships, petrography, bulk-rock geochemistry and Sr-Nd-Pb systematics, and zircon U-Pb ages and Hf-O isotopes of representative lithological components of the Dongling complex. The objectives are to precisely constrain the timing, protolith, and tectonic setting of the complex, information important for unraveling the tectono-thermal history of the NW Yangtze Block. The results will provide significant insights into the early Precambrian tectonic evolution of the whole Yangtze Block and its possible link to the supercontinent Columbia and Rodinia. This study will also contribute to a better understanding in the petrogenesis of widespread Mesozoic magmatism that has been responsible for the large-scale Cu-Fe-Mo-Au mineralization in the Middle-Lower Yangtze Metallogenic Belt.

董岭杂岩位于扬子陆块东北缘的长江中下游成矿带，通常被认为可能是扬子陆块内部与崆岭杂岩相似的古老基底。但迄今为止对董岭杂岩时代归属和构造属性的研究还十分薄弱，制约了对扬子陆块前寒武纪地壳演化的全面认识和长江中下游中生代岩浆活动及成矿作用的深入理解。本申请拟对董岭杂岩开展系统的岩石学、元素地球化学、全岩Sr-Nd-Pb同位素及锆石U-Pb定年和Hf-O同位素组成的综合研究，系统厘定董岭杂岩的形成时代、原岩性质和大地构造属性，查明本区古老基底记录的多期次构造-热事件，进一步揭示扬子陆块前寒武纪变质基底的时空分布及早期地壳的形成和演化历史，为认识扬子陆块与Columbia和Rodinia超大陆聚合-裂解事件的关系及古老地壳基底对长江中下游中生代侵入岩和多金属矿床物质来源的贡献和作用方式等提供新的资料和证据。

董岭杂岩位于扬子陆块东北缘的长江中下游成矿带，通常被认为可能是扬子陆块内部与崆岭杂岩相似的古老基底。但迄今为止对董岭杂岩时代归属和构造属性的研究还十分薄弱，制约了对扬子陆块前寒武纪地壳演化的全面认识和长江中下游中生代岩浆活动及成矿作用的深入理解。本项目主要对董岭杂岩开展系统的岩石学、元素地球化学、锆石U-Pb定年和Hf-O同位素组成的综合研究，取得如下成果：①在董岭杂岩中识别出古元古代基底岩石，并首次确认了在扬子陆块东北缘存在双层基底地壳结构；②通过对基底岩石的地球化学性质的梳理，认为它们具有A-型花岗岩的特征，即在1.85 Ga之后，扬子陆块全面开启了克拉通稳定化过程；③通过系统收集扬子陆块上已存的古元古代构造-岩浆事件并与相关大陆开展对比，认为扬子陆块在Columbia超大陆重建过程中可能位于西澳和南非之间。