郯庐断裂带渤海湾北段早新生代逆冲推覆的生长褶皱证据  

Magma Source of the A-Type Granite and Slab Break-Off in the Middle Segment of the Bangonghu-Nujiang Suture , Tibet Plateau

作　　者：李志刚[1] 陈伟[2,3] 贾东 李世琴[2,3] 许强[4] 周小军 金柯[5] 

机构地区：[1]南京大学地球科学与工程学院,南京210093 [2]西南石油大学资源与环境学院,成都610500 [3]油气藏地质及开发工程国家重点实验室,成都610500 [4]中国科学院青藏高原研究所,北京100085 [5]中国石油天然气股份有限公司辽河油田分公司,辽宁盘锦124000

出　　处：《地质学报》2013年第6期759-772,共14页Acta Geologica Sinica

基　　金：本文为国家“973”计划（编号2008CB425702）和国家自然科学基金项目（编号409721/12）共同资助的成果.

摘　　要：高分辨率的地震剖面显示辽河盆地西部凹陷深部存在-生长断层转折实褶皱。本文对地震剖面的构造变形以及褶皱两翼的生长前、生长和生长后地层的变形几何关系进行详细构造解析；利用断层转折褶铍几何变形的计算机模拟技术分别对西部凹陷南段、北段的生长断层转折褶皱进行几何变形过程的模拟，提取构造特征并与实际地震反射剖面进行对比。研究结果表明．郯庐断裂带渤海湾北段分支断层台安大洼断层在早新生代就存在逆冲推覆过程．构造活动主要发生在沙河街组三段下至馆陶组沉积前（E2s^3下～N1g前），其逆冲推覆速率为0．116mm／a。During the geological investigation of last several years , agroup of A-type granitic plutons has been found in the middle segment of the Bangonghu-Nujiang suture.These granitic plutons occur as stocks with an exposed area of less than1km 2 and lithologically include two types of biotite granite and granodiorite porphyry , which intrude into Cretaceous sedimentary rocks.A systematic analysis of whole-rock element geochemistry and Nd , Sr , Pb isotope for these A-type granites indicates that they contain high SiO2 content varying from 68.62% ～75.36%.Moreover they have relatively high K2O＋Na2O （ 8.03% ～ 9.37% ） and Fe 2 O 3T （ 0.86% ～5.39% ） and low Al 2 O 3 （ 12.76% ～15.54% ） content , appearing weak peraluminous and metaluminous features.Trace elements N-MORB-normalized spider diagram displays apparent enrichment in large ion lithophile element （ LILE ） Rb , Th , U , K , Pb with Ba and Sr of marked depletion.High field strenth element （ HFSE ） Nb , Ta and Ti are sharply depleted with Zr and Hf of relative enrichment.All of these are characteristic of A-type granite and different from arc granite.These granites have high REE contents （ ∑REE=122.37×10 -6 ～291.19×10 -6 , with an average of 201.31× 10 -6 ） .Light REE are rich relative to heavy REE （ LREE / HREE=4.89～9.58 , with an average of 5.93 ） and negative Eu anormalies are sharp （ δ Eu =0.14～0.54 , with mean value of 0.34 ）, making their chondritenormalized rare earth element patterns appear slightly right-dipping V-type.Nd , Sr and Pb isotope results indicate that the A-type granites from the middle segment of the Bangonghu-Nujiang suture are rich in radioactive isotope.Their 87 Sr / 86 Sr and I Sr ratio values vary from 0.719842～0.786395and 0.706900～0. 710378 , respectively. 143 Nd / 144 Nd ratio values are from 0.512123～0.512392 , with large negativeε Nd values （ -3.37～ -10.34 ）, reflecting important involvement of crustal components.Pb isotope composition 206 Pb / 204 Pb , 207 Pb / 204 Pb ,

关 键 词：辽河箍地 生长断层转折褶皱 郯庐断裂带 台安-大洼断层 

分 类 号：P542.2[天文地球—构造地质学]