摘要
对延边地区棉田花岗闪长岩岩体进行了锆石 U-Pb 年代学、岩石地球化学以及 Hf 同位素的研究,以便对其岩石成因和古太平洋板块俯冲作用的开始时间给予制约.棉田岩体主要由花岗闪长岩和次要的花岗岩组成,花岗闪长岩中锆石 LA-ICP-MS U-Pb 定年结果表明,该岩体形成于早侏罗世（177＆#177;2 Ma,MSWD=1.13）.在地球化学研究方面,它们属于高钾钙碱性-钙碱性系列,A/CNK 值介于0.88~1.12之间,属准铝质,为 I 型花岗岩,并且明显富集大离子亲石元素（如 K、Ba、Rb）、轻稀土元素（LREE）以及 Th、U,相对亏损高场强元素（如 Ta、Nb、Ti、P）.岩石的εHf （t ）值和二阶段模式年龄（T DM2）分别介于＆#177;8.72~＆#177;12.28和437~663 Ma 之间.结果表明,岩体的原始岩浆源于新增生陆壳的部分熔融.综合区域同时代火成岩的研究成果,认为棉田花岗闪长岩岩体形成于古太平洋板块向欧亚大陆俯冲下的火山弧环境.
This paper presents LA-ICP-MS zircon U-Pb dating,geochemical and Hf isotopic data of the granodiorite from Mian-tian intrusion in Yanbian region,with the aim of constraining its petrogenesis and beginning time of subduction of the Paleo-Pacific plate beneath the Eurasian continent.The Miantian intrusion consists mainly of granodiorite with minor diorite.The LA-ICP-MS U-Pb dating results of zircons from the granodiorite indicate that the intrusion formed in the Early Jurassic （1 77 ＆#177; 2 Ma,MSWD=1.13）.Geochemically,these rocks fall into the calc-alkaline to high-K calc-alkaline series,with A/CNK ratios of 0.88-1.12,which are sub-aluminous granites,being of the characteristics of I type granitoids,enrichment in LILE （such as K,Ba,Rb）,LREE,Th and U,relatively depleted in HFSE （such as Ta,Nb,Ti,P）.TheεHf （t ）values of the granodiorite vary from ＆#177;8.72 to ＆#177;12.28,and two-stage model ages （T DM2 ）vary from 437 to 663 Ma.These characteristics suggest that the primary magma was derived from the remelting of juvenile crustal materials （Neoproterozoic to Early Paleozoic）.It is conclu-ded that granodiorite from Miantian intrusion formed in compressional structure setting similar to volcanic arc which could be related to the subduction of the Paleo-Pacific plate beneath the Eurasian continent.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2015年第1期49-60,共12页
Earth Science-Journal of China University of Geosciences
基金
吉黑东部区域成矿规律综合研究(No.1212011085485)
国家自然科学基金项目(No.41272093)资助
