浙江沿海晚中生代典型花岗岩及其中暗色微粒包体和基性岩脉的成因：对壳幔相互作用深部过程的启示

As a major component of continental crust, granites have been served as the most important subject in geology. Meanwhile, mafic microgranular enclaves (MMEs) and mafic dykes within the granites can not only provide crucial clues for granite petrogenesis, but also become windows in probing the nature of deep mantle and crustal components. Based on our previous accumulation for intermediate-acid rock studies in Southeastern China, integrated investigations will be carried out on the Late Mesozoic representative granites (Qingtian, Xiaojiang and Putuoshan), their MMEs and mafic dykes along the Zhejiang coastal area in this project, with the aim to: (1) distinguish the relationships between the MMEs, mafic dykes and their host granite on the basis of the detailed field and petrography observations, the conventional geochemistry analysis, and their zircon U-Pb datings; (2) especially identify the nature of crustal and mantle components involved in rock-formation, and to unravel the deep dynamic process of the interaction between the crustal- and mantle-derived magmas via in-situ mineral trace elements and zircon Hf–O isotopic compositions research; (3) meanwhile discuss the diffusion and migration regularities of geochemical components between MMEs and their host granites during magmatic evolution, by means of the systematic sampling plan in profiling from the center of MMEs to inner parts of host granites. The scientific importance of the study depends on their facilitation of a better understanding of crust–mantle interactions during the magmatism along the southeastern coast of China, as well as their further clues to constraints the Late Mesozoic tectono-magmatic evolution of the area.

花岗岩是大陆地壳的重要组成，是地质学研究的重要课题。而产于花岗岩中的暗色微粒包体和基性岩脉不仅是研究花岗岩成因的重要线索，还是揭示深部地壳和地幔性状的窗口。本项目拟在中国东南部中酸性岩石研究积累的基础上，选择浙江沿海晚中生代典型花岗岩（青田、小将和普陀山）及其包体和基性岩脉为研究对象，(1)开展详细的野外地质和岩相学观察、常规地球化学研究和锆石U-Pb定年工作，以鉴别花岗岩、包体与基性岩脉的关系；(2)着重采用矿物原位微区元素和锆石Hf-O同位素分析方法以揭示参与成岩的壳幔端元性状，探索壳幔相互作用的深部过程；(3)利用从包体中心至寄主岩内部的系统剖面采样方案，藉此探讨包体与寄主岩浆之间的化学扩散迁移规律。本项研究既有助于深化对中国东南部晚中生代岩浆活动中壳幔相互作用的认识，也可为揭示区内晚中生代的构造-岩浆演化提供进一步线索，因而具有重要的科学意义。

花岗岩是大陆地壳的重要组成，是地质学研究的重要课题。而产于花岗岩中的暗色微粒包体和基性岩脉不仅是研究花岗岩成因的重要线索，还是揭示深部地壳和地幔性状的窗口。本项目拟在中国东南部中酸性岩石研究积累的基础上，选择浙江沿海晚中生代典型花岗岩（青田、小将和普陀山）及其包体和基性岩脉为研究对象，(1)开展详细的野外地质和岩相学观察、常规地球化学研究和锆石U-Pb定年工作，以鉴别花岗岩、包体与基性岩脉的关系；(2)着重采用矿物原位微区元素和锆石Hf-O同位素分析方法以揭示参与成岩的壳幔端元性状，探索壳幔相互作用的深部过程；(3)利用从包体中心至寄主岩内部的系统剖面采样方案，藉此探讨包体与寄主岩浆之间的化学扩散迁移规律。本项研究既有助于深化对中国东南部晚中生代岩浆活动中壳幔相互作用的认识，也可为揭示区内晚中生代的构造-岩浆演化提供进一步线索，因而具有重要的科学意义。通过对东南沿海铁质和镁质花岗岩及其包体和基性岩脉成因研究，为古太平洋板块俯冲提供进一步制约；结合本次研究及中国东南部白垩纪岩浆岩的已有数据，提出区内岩浆岩的地球化学特征分别在136和118 Ma发生明显变化，其中136–118 Ma时期岩浆岩的岩浆源区记录了最低的俯冲板片组分参与量，这恰恰为125–122 Ma时期古太平洋板块运动方向由南西（SW）转变为北西 (NW)提供了重要的岩石学证据。同时，本次研究在论述花岗岩成岩成矿进展的基础上，提出华南中生代大花岗岩省成岩成矿作用需要进一步研究的一些科学问题。