摘要
黑马河岩体位于西秦岭北缘青海南山构造带内,岩体中发育大量闪长质包体,但对其成因却有一定的争议.从岩石学、矿物学、地球化学和年代学等方面对黑马河岩体花岗闪长岩及其中的闪长质包体进行了详细研究.包体的野外产出状态、形态、结构构造和矿物学特征均显示出,它们是基性岩浆注入到中酸性岩浆中快速冷凝结晶的产物.在主量元素协变图解中,花岗闪长岩和闪长质包体显示出壳幔岩浆混合作用的趋势.另外,两者稀土总量和相似的稀土元素配分模式及Eu负异常程度,也显示二者具有岩浆混合的特征.LA-ICPMS锆石U-Pb定年结果显示,花岗闪长岩形成于246 Ma,闪长质包体形成于245 Ma,两者具有几乎一致的结晶年龄,排除了包体为源区难熔残余或围岩捕掳体的可能性,也排除了基性岩浆在花岗质岩浆固结后再侵入的可能性.结合区域地质资料,认为黑马河岩体形成于西秦岭北缘有限小洋盆向南的俯冲阶段,青海南山构造带与天峻南山一带具有相同的构造岩浆演化历史.
The Heimahe pluton is located in the Qinghai Nanshan tectonic belt,northern margin of the West Qinling orogeny.Mafic microgranular enclaves(MMEs) are widely distributed in the Heimahe pluton. However, the petrogenesis of the MMEs is an issue of debate. We present the petrology,mineral chemistry, rock geochemistry and geochronology of the granodiorite and MMEs from the pluton in this paper. The outcrop conditions,shapes, structural and mineral characters of the MMEs reflect that they were products of rapid crystallization when mafic magma injected into the intermediate-acid magma. In the binary diagram of major elements, the granodiorites and MMEs show a mixing trend between mantle-and crust-derived magmas. Besides,their total REE contents and similar REE patterns and Eu anomalies also support the magma mixing model. LA-ICPMS zircon U-Pb dating results show that the granodiorite formed at 246 Ma, and the MMEs formed at 245 Ma. The same crystallization age suggests that the MMEs were not restites or host-rock xenoliths. Combined with regional geology, we suggest that the Heimahe pluton formed by the southward subduction of the limited oceanic basin in the northern margin of the West Qinling, and the Qinghai Nanshan tectonic belt experienced the same evolutionary process with the Tianjun Nanshan belt.
作者
王盟
裴先治
刘成军
张永明
李佐臣
李瑞保
裴磊
陈有炘
陈国超
Wang Meng;Pei Xianzhi;Liu Chengjun;Zhang Yongming;Li Zuochen;Li Ruibao;Pei Lei;Chen Youxin;Chen Guochao(Key Laboratory of Western China’s Mineral Resources and Geological Engineering,Ministry of Education,Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,MNR/School of Earth Science and Resources,Chang’an University,Xi'an 710054,China;Faculty of Resources and Environmental Engineering,Shandong University of Technology,Zibo 255049,China;School of Civil Engineering,Nanyang Institutte of Technology,Nanyang 473000,Chirm)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2019年第7期2490-2504,共15页
Earth Science
基金
中国博士后科学基金项目(No.2016M592726)
国家自然科学基金项目(Nos.41872235,41872233,41472191,41502191)
中国地质调查局地质调查项目(Nos.12120114041201,12120114018219)
西安市科协青年人才托举计划项目
关键词
青海南山
西秦岭北缘
黑马河岩体
暗色微粒包体
岩石成因
地球化学
Qinghai Nanshan
northern margin of West Qinling
Heimahe pluton
mafic microgranular enclaves
petrogenesis
geochemistry