庐山地区晚中生代深源岩浆与浅表构造变形 的相互作用  

Interaction between magmatism and deformation in the Mesozoic of the Lushan area,eastern China

作　　者：莫佳君 徐义刚[1,2,3] 何斌 Jiajun Mo;Yi-Gang Xu;Bin He(State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Center for Excellence in Deep Earth Science,Chinese Academy of Sciences,Guangzhou 510640,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广州510640 [2]中国科学院深地科学卓越研究中心,广州510640 [3]中国科学院大学地球与行星科学学院,北京100049

出　　处：《科学通报》2024年第2期301-316,共16页Chinese Science Bulletin

基　　金：中国科学院战略性先导科技专项(XDB18000000)资助。

摘　　要：本文在对庐山地质构造细致解剖的基础上,根据研究区岩浆岩的同位素年代学、锆石Hf同位素和元素地球化学特征,提出了研究区基性岩浆的高分异作用;结合对变质作用和构造变形时间的约束,揭示了研究区晚中生代深源岩浆演化与逆冲推覆构造和片麻岩穹隆的共生关系.庐山地区晚中生代构造格架主要为飞来峰构造和星子片麻岩穹隆,两者在时空上存在一致性.星子片麻岩穹隆中心发育大量晚中生代岩浆岩,岩石类型从基性岩脉到高分异花岗岩,包括斜长角闪片麻岩、角闪石岩、黑云母角闪闪长岩、石英闪长岩、黑云母(二长)花岗岩、白岗岩和伟晶岩,这些侵入岩的锆石年龄在误差范围内一致(141±2 Ma).不同类型岩石的锆石εHf(t)值为−10.5~+2.2,推测白岗岩和伟晶岩是基性岩浆高分异作用的结果.岩浆侵位和演化明显受到北东向逆冲推覆构造的控制,自南西向北东,岩浆的演化程度逐渐增强.本文认为,由岩浆热弱化地壳强度是庐山地区发育逆冲推覆构造的关键条件.与此同时,推覆构造和韧性剪切带隔热作用是基性岩浆发生高程度分异的重要因素.因此,庐山地区晚中生代地质演化是深源岩浆与浅表构造变形相互作用的一个实例,代表了板内强烈变形和造山运动的一种方式,与早白垩世太平洋板块俯冲作用密切关联.The interaction between lithospheric deformation and magmatism is pivotal for understanding the structure and evolution of continents.However,the underlying mechanism remains elusive.This study presents an example of the coupling and feedback between magmatism and deformation during the Late Mesozoic in the Lushan area of eastern China.The Lushan area is composed of a Mesozoic Xingzi gneiss dome consisting of core,mantle,and cover.Numerous plutons and dikes are distributed in the core of the gneiss dome.The mantle is a 2–3 km thick contact metamorphic zone(sillimanite,staurolite,garnet,and mica)with migmatites in localities where strongly deformed zones(amphibolite facies)and ductile shear zones(greenschist facies)have developed from base to top.The cover of the gneiss dome is an unmetamorphosed and undeformed structural klippe named Hanyangfeng.We dated all types of plutons and dikes in the core.The results show that the emplacement ages of these intrusive rocks are essentially same within error(141±2 Ma),and no age difference is observed between the deformed and undeformed rocks.40Ar/39Ar dating of hornblende from the migmatite in the strongly deformed zone yielded a deformation age of 138.62±0.32 Ma.Interestingly,the timing of the deformation and metamorphism(approximately 140 Ma)of the Xingzi gneiss dome is similar to that of the magmatism.Another major geological feature of the Lushan area is highly fractionated magmatism in the core of the Xingzi gneiss dome.The rocks exhibit considerable variation,ranging from amphibolite gneiss,amphibolite,biotite hornblende diorite,quartz diorite,biotite monzogranite,alaskite,and pegmatite.Alaskite and pegmatite have significantly high Rb/Sr and low Zr/Hf values,indicating their highly fractionated nature.All intrusive rocks,irrespective of their silica content,display similar ages and a similar range of zircon Hf isotope ratios(εHf(t)=−10.5 to+2.2),suggesting a fractionation relationship between different rock types and a derivation of their primary basic magmas

关 键 词：庐山 晚中生代 逆冲推覆构造 片麻岩穹隆 岩浆高分异演化 深源岩浆与浅表构造 

分 类 号：P548[天文地球—构造地质学] P534.5[天文地球—地质学]