喀喇沁变质核杂岩形成时代的锆石年代学制约  

Formation Time of the Kalaqin Metamorphic Core Complex: Constraints from Zircon Dating

作　　者：林少泽 谢成龙[3] 向必伟[4] 赵田[4] LIN Shaoze1, 2, XIE Chenglong3, XIANG Biwei4 and ZHAO Tian4(1. Key Laboratory of New Technology for Construction of Cities in Mountain Area （Chongqing University）, Ministry of Education, Chongqing 400045, China; 2. School of Civil Engineering, Chongqing University, Chongqing 400045, China; 3. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, Anhui, China; 4. School of Resources and Environmental Engineering, Anhui University, Hefei 230601, Anhui, China)

机构地区：[1]重庆大学山地城镇建设与新技术教育部重点实验室,重庆400045 [2]重庆大学土木工程学院,重庆400045 [3]合肥工业大学资源与环境工程学院,安徽合肥230009 [4]安徽大学资源与环境工程学院,安徽合肥230601

出　　处：《大地构造与成矿学》2018年第3期570-586,共17页Geotectonica et Metallogenia

基　　金：中央高校基本科研业务费专项(106112016CDJRC000108;106112017CDJXY200004);国家自然科学基金项目(41772210;41472194)联合资助

摘　　要：喀喇沁变质核杂岩位于燕山构造带北缘,是认识华北克拉通晚中生代破坏过程的重要对象。通过对核杂岩内安家营子岩体与伴生花岗闪长岩脉的变形特征与锆石年代学研究,限定核杂岩的变形序列与时代。野外观察表明,安家营子岩体与伴生花岗闪长岩脉的侵位发生在早阶段伸展变形之后,属于晚阶段伸展的同构造岩浆活动。通过LA-ICP-MS锆石U-Pb定年,安家营子岩体2个样品分别给出133 Ma和131 Ma的年龄,而1个花岗闪长岩脉样品给出了135 Ma的年龄。结果显示该变质核杂岩的早阶段伸展活动发生在156～135 Ma之间,而不是过去认为的早白垩世。结合前人研究结果,可以限定这一早阶段伸展活动发生在晚侏罗世(156～150 Ma),形成了未完全剥露的变质核杂岩;在早白垩世再次经历伸展变形的叠加改造。对喀喇沁变质核杂岩形成时代的重新厘定,为燕山构造带存在晚侏罗世伸展活动提供了证据,暗示华北克拉通破坏可能从晚侏罗世已经开始发生。The Kalaqin metamorphic core complex, located on the northern margin of the Yanshan Tectonic Belt, is an important structure to understand the Late Mesozoic destruction processes of the North China Craton. In this study, structural analysis and geochronological investigation were conducted for the Anjiayingzi pluton and associated granodiorite dikes that intruded the core complex. Field observations demonstrated that emplacement of the pluton and dikes took place after the early stage extensional deformation, and intrusions are products of syn-tectonic magmatism during the late stage extension deformation. LA-ICP-MS zircon U-Pb dating yielded ages of 133–131 Ma for the Anjiayingzi pluton and 135 Ma for the dike, which demonstrated that the early extensional deformation took place at 156–135 Ma, rather than the Early Cretaceous as proposed previously. By integrating with other dating results, the early extensional deformation occurred at 156–150 Ma（Late Jurassic） and led to the exhumation of the core complex. The core complex was overprinted by a late extension in the Early Cretaceous. The revision of formation time for the Kalaqin metamorphic core complex further confirms that the extensional deformation took place in the Late Jurassic in the Yanshan tectonic belt, and therefore, it is likely that the northern margin of the North China Craton might have destructed since the Late Jurassic.

关 键 词：燕山构造带 喀喇沁变质核杂岩 伸展变形 锆石U-PB定年 晚侏罗世 

分 类 号：P542[天文地球—构造地质学]