冀北晚古生代侵入岩的矿物学及Os-Nd-Sr同位素研究

There are reports on Late Paleozoic intrusive rocks at the northern margin of the North China Craton (NCC), recently, but the geodynamic setting for their formation is still controversial, and little is known about the magmatic process in the depth, which is critical to understand the inducement of lithospheric thinning. This project will study systematically on the Xianghuangqi-Wudaoyingzi and Lingying complexes from the northern Hebei Provice, which are characterized by presence of abundant hornblend and sucessive rock association. On the base of geochronology, geochemsitry and Sr-Nd isotopic analysis, it will focus on (1) microstructure and mineral composition study of the hornblendes, which are commom development in different lithology, and other minerals, and (2) Os isotopic data of the ultramafic-mafic plutons, with an attempt to reveal their petrogenesis, parent magma nature and magmatic evolution of the two complexes, to put more insights into the nature of the lithospheric mantle beneath the northern margin of the NCC, and to understand the continental property of the NCC during the Late Paleozoic.

近期学者们对华北克拉通北缘晚古生代侵入岩进行了报道，但是有关其形成构造背景尚存在争议，且对其深部岩浆作用过程研究较少，而后者可能对探究华北克拉通中生代减薄的诱因具有重要意义。本项目拟对以富含角闪石为特征且岩性出露较齐全的冀北厢黄旗-五道营子、凌营岩体展开系统研究。将在年代学、地球化学和Sr-Nd同位素地球化学研究的基础上，侧重于：（1）在不同岩性中普遍发育的角闪石及其它单矿物的结构和成分研究；（2）基性-超基性岩的Re-Os同位素分析，从而探究其岩石成因、母岩浆特征、岩浆演化过程，确定华北克拉通北缘晚古生代的岩石圈地幔性质，并厘定华北克拉通北缘晚古生代的陆缘性质。

近年来在华北克拉通北缘有一些晚古生代侵入岩被报道，但是有关其形成构造背景尚存在争议，且对其深部岩浆作用过程研究较少，而后者可能对探究华北克拉通中生代减薄的诱因具有重要意义。本项目选取冀北地区的晚古生代以富含角闪石为特征且岩性出露较齐全的厢黄旗-五道营子、凌营岩体以及东湾子岩体作为研究对象，经过详细的野外地质调查与系统的室内测试分析，获得重要的数据资料。取得的成果主要包括：（1）冀北地区以东湾子岩体为代表的晚古生代镁铁质—超镁铁质岩是普遍为堆晶成因，岩体中的正长岩代表了岩浆残余的成分。（2）冀北地区晚古生代岩体的母岩浆都具有富水的特征，母岩浆富水的性质可能与受到俯冲带流体/熔体交代的地幔楔有关。推测它们来源于石榴石稳定的富集型岩石圈地幔。东湾子岩体母岩浆是由亏损的软流圈地幔熔体和富集的岩石圈地幔熔体混合形成，并含有少量的地壳物质的混染（≤ 2.5%）（3）晚古生代岩体普遍具有富集大离子亲石元素(e. g., Sr, Ba, K)，亏损高场强元素(e. g., Nb, Ta, Ti)的特征，同时透辉石和角闪石的矿物成分也证实为弧堆晶成因，这些证据表明它们的母岩浆是弧岩浆。它们可能形成于活动陆缘环境；东湾子岩体则代表了弧后伸展环境。.相关成果已发表在《International Geology Review 》上，为后续研究奠定了坚实的基础。