西秦岭北缘秦岭杂岩变质作用:副片麻岩岩石学、相平衡模拟及其地质意义  

Metamorphism of Qinling Complex in Northern West Qinling Orogen:Petrology,Phase Equilibria Modelling of Paragneiss and Their Geological Implication

作　　者：毛小红[1,2] 张建新[1] 于胜尧[3,4] 李云帅 喻星星 路增龙[1] 周桂生 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]中国海洋大学海洋地球科学学院海底科学与探测技术教育部重点实验室,山东青岛266100 [4]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,山东青岛266235 [5]天津大学表层地球系统科学研究院,天津300072

出　　处：《地球科学》2018年第1期278-295,共18页Earth Science

基　　金：国家自然科学基金项目(Nos.41630207;41572180);中国地质调查局项目(No.DD20160022)

摘　　要：造山带中的高级变质岩是研究造山带形成和演化历史的重要窗口.西秦岭北缘秦岭杂岩主要由正片麻岩、副片麻岩、少量变基性岩(基性麻粒岩)和大理岩组成.岩相学、矿物化学和相平衡模拟结果表明副片麻岩经历了3个变质演化阶段:(1)进变质阶段,以石榴子石核部包裹细粒片状黑云母和大小不等的石英为代表;(2)峰期变质阶段,矿物组合为石榴子石+斜长石+钾长石+夕线石+黑云母+金红石+石英.石榴子石变斑晶幔部成分在视剖面图上确定出峰期温压条件为T=793~803℃,P=8.8~9.5kbar;(3)降温降压的退变质阶段,主要由石榴子石的最边部及后期斜长石记录.结合已有研究资料,表明西秦岭北缘秦岭杂岩可能经历了早古生代晚期与碰撞造山作用有关的变质作用与深熔作用.Studies of high-grade metamorphic rocks in an ancient orogenic belt can provide important constraints on the formation and tectonic evolution of orogen.The Qinling complex in the northern West Qinling orogen mainly consists of orogneiss,paragneiss,minor metabasite（mafic granulite）and marble.The petrography,mineral chemistry and phase equilibria modelling in this study show that paragneiss has experencied three metamorphic evolution stages.Stage 1 is the prograde stage,characterized by biotite and quartz occurring as inclusions in garnet.Stage 2 is the peak metamorphic stage,and mineral assemblage in this stage is interpreted to be garnet＋sillimanite＋K-feldspar＋plagioclase＋biotite＋quartz＋rutile,which formed in P-Tcon-ditions of 793-803℃ and 8.8-9.5 kbar.Stage 3 is the retrograde stage with decrease in temperature and pressure,which is recorded by garnet and plagioclase.Combining with previous data,it is suggested that the Qinling complex in the northern West Qinling orogen has experienced Early Paleozoic metamorphism and anataxis related to collision orogenesis.

关 键 词：西秦岭 秦岭杂岩 副片麻岩 变质作用 相平衡模拟 岩石学 

分 类 号：P581[天文地球—岩石学]