南秦岭地体狭窄带的地壳再造与穹隆作用：佛坪穹隆地区早中生代花岗岩和基底岩石研究

Early Mesozoic magmatism of granitic composition took place strongly in the Foping dome, central part of the Qinling orogenic belt. It is characterized by wide-spreading of large plutons, various rock types and multiple magmatic stages. These granitoids are important research objects for understanding orogenic processes and formation and reworking of the crust in the Qinling orogen during the Early Mesozoic time. This project aims in the granitoid rocks, metamorphic rocks and migmatite of the basement rocks exposed in the dome, to reveal the relationship between the magmatism in deep crustal section and tectonic response in the shallow crustal section of the orogenic belt. Major research contents of this project are: (1) to acquire Sr-Nd-Pb-Hf radiogenic isotopic composition of major granite plutons for compositional diversification in magma sources beneath the orogen; (2) to acquire formation ages of the granitoids for the temporal limit of the magmatic activities and genetic relationship in the Foping dome; (3) to acquire time record of metamorphism and partial melting of metamorphic rocks and migmatite in the Foping basement. The research results of the magmatism, metamorphism and doming could help us to clear genetic relationship between the magmatism in the deep lithosphere, to answer why strong crustal reworking and doming took place in the narrow zone of the orogenic belt and to better understand the tectonic response of the shallow crust in the narrow part of the South Qinling orogenic belt.

南秦岭造山带中部佛坪穹隆地区早中生代花岗质岩浆作用强烈，岩石类型和岩浆作用期次多。这些花岗岩类岩石记录着中生代秦岭造山带演化过程、地壳形成和再造作用，是理解造山作用的重要介质。基于造山带的狭窄区出现强烈的岩浆-穹隆作用的现象，项目以穹窿地区花岗岩类岩石、基底变质岩和混合岩为研究对象，研究造山带地壳深部岩浆作用与浅部构造响应。重点研究内容有：(1) 获取主体花岗岩Sr-Nd-Pb-Hf同位素地球化学组成，分析岩浆源区特征；(2) 获取花岗岩形成时代，厘清早中生代岩浆作用期次和时限，明确多期次大规模岩浆作用与造山过程的成因联系；(3) 获取基底岩石和混合岩变质作用和部分熔融作用的时间记录。探讨南秦岭造山带的狭窄区的岩浆作用、变质作用和穹窿作用之间的成因联系，回答为何在造山带狭窄地带发生强烈的地壳再造作用和穹隆构造作用，为进一步认识在秦岭造山带的岩石圈深部岩浆作用与浅部构造响应的成因联系提供重要

研究项目以佛坪穹窿地区早中生代岩浆岩、佛坪群基底岩石和混合岩为重点研究对象，以邻区早中生代花岗岩类岩石为对比研究，厘定基底岩石物质组成和来源及其形成时代、基底岩石变质时代和岩浆作用期次和地球化学组成特征及其成因问题。基于项目获得的数据资料,确定佛坪群形成于新元古代，强烈的混合岩化作用发生于早中生代，与穹窿地区和邻区强烈的岩浆作用基本同步，探讨了南秦岭造山带内岩浆作用和构造-变质作用的成因关联。同时，结合穹窿地区东、西部几个代表性早中生代大型的花岗岩体，如糜署岭岩体、东江口岩体等地球化学组成特征研究，观察到南秦岭造山带内花岗岩类岩体的成分多样性特征，进而探讨其不同的成因机制问题。在项目执行过程中，已发表与项目的研究内容相关的SCI学术论文4篇，另有2篇文稿尚在SCI期刊审稿。另外，已发表项目资助标注的学术论文13篇，其中SCI论文11篇。13名硕/博士研究生和两名博士后参与项目研究工作，其中毕业并获得学位的硕士和博士研究生各4名、两名博士后晋升为副高级职称，充实了造山带内岩浆作用和地壳演化的研究团队。