北山石板井地区英云闪长岩-石英闪长岩体锆石U-Pb年龄、成因及对古洋盆俯冲作用时限的制约  

Zircon U-Pb age and petrogenesis of tonalite-quartz diorite in the Shibanjing area,central Beishan orogenic belt,and its constraint on subduction of the ancient oceanic basin

作　　者：修迪 陈超 专少鹏 申宗义 王金贵 程洲 张立国 王硕 杨鑫朋 侯德华 石光耀 张鹏程 XIU Di;CHEN Chao;ZHUAN Shaopeng;SHEN Zongyi;WANGJingui;CHENG Zhou;ZHANG Liguo;WANG Shuo;YANG Xinpeng;HOUDehua;SHI Guangyao;ZHANG Pengcheng(Hebei Regional Geological Survey Institute,Langfang 065000,Hebei,China)

机构地区：[1]河北省区域地质调查院,河北廊坊065000

出　　处：《地质通报》2018年第6期975-986,共12页Geological Bulletin of China

基　　金：中国地质调查局项目<阴山成矿带小狐狸山和雅布赖地区地质矿产调查>(编号:DD20160039)

摘　　要：北山造山带中部石板井地区出露早古生代英云闪长岩-石英闪长岩体。用LA-ICP-MS技术测得该岩体石英闪长岩中锆石的206Pb/238U年龄为464.4±2.1Ma。岩石地球化学分析结果显示,岩石属钙碱性至高钾钙碱性、准铝质I型花岗岩。通过岩石成因分析,英云闪长岩-石英闪长岩体为来自地壳的岩浆与来自深部的亏损地幔岩浆,在高压(>1.5GPa)、低温(719~792℃)条件下,经不均匀混合作用形成,同时有俯冲流体的加入,残留相为石榴子石+金红石(无角闪石)。岩石富集Rb、Ba、Th、U、K等大离子亲石元素,亏损Ta、Nb、P、Ti等高场强元素,显示出典型岛弧型花岗岩的地球化学特征。微量元素构造环境判别图进一步证明,岩体形成于岛弧环境。与南侧的红柳河-牛圈子-洗肠井古生代洋盆构成"沟-弧"体系,表明红柳河-牛圈子-洗肠井古洋盆在中奥陶世晚期已经向北俯冲,该洋盆闭合时限应晚于中奥陶世。The Early Paleozoic Yingyyn d io rite-quartz diorite is exposed in the Shibanjing area of central Bpaper, LA-ICP-MS zircon U-Pb dating of the rock mass was conducted, and the 206Pb/238U average age is 464.4X2.IMa. According to geochemical data,the rocks belong to the calc-alkaline to high potassium calc-alkaline, quasi-aluminous I type granite. Inview of its petrogenesis,the authors hold that the magma source of tonali te-quartz diorite was formed by mixed magma from the crust and magma from the depleted mantle under the conditions of high pressure （〉1.5GPa） and lowtemperature （719-792℃）,wi th the residual minerals of garnetruble （wi thout amphibole）. Moreover , trace element composition is characterized by enrichment of large ion lithophie ele-ments （LILEs）, such as Rb, Ba, Th, U and K, and depletion of high field s trength elements （tlFSEs）, Ta, Nb, P, and Ti, showing the geo-chemical features of the typical island arc granite. It is further proved that the rock mass was formed in an island arc environment on the discriminant map of trace elements tectonic environment. It constitutes ^oceanic trench-arc,system with the south suhe Niuquanzi^Xichanging Paleozoic oceanic basin, indicating that the Hongl iuhe Niuquanzi^Hidaging Paleozoic basin had sub-ducted nor thward in the late Midcde Ordovician. The closure time of the ocean basin should be later than Midcde Ordovician.

关 键 词：北山造山带 石板井 英云闪长岩-石英闪长岩 锆石U-Pb定年 岩石成因 构造背景 

分 类 号：P588.123[天文地球—岩石学] P597.3[天文地球—地质学]