兴蒙造山带中段锡林浩特跃进地区石炭纪岛弧型侵入岩:年代学、地球化学、Sr-Nd-Hf同位素特征及其地质意义  

Geochronology,Geochemistry,Sr-Nd-Hf Isotopic Characteristics and Geological Significance of Carboniferous Yuejin Arc Intrusive Rocks of Xilinhot,Inner Mongolia

作　　者：王树庆 胡晓佳 杨泽黎 赵华雷 张永 郝爽 何丽[2] Wang Shuqing1 , Hu Xiaojia1, Yang Zeli1 , Zhao Hualei1, Zhang Yong1 , Hao Shuang1 , He Li2(1.Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China 2.Regional Geology and Mineral Resources Survey Institute of Hebei Province, Langfang 065000, Chin)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]河北区域地质矿产调查研究所,河北廊坊065000

出　　处：《地球科学》2018年第3期672-695,共24页Earth Science

基　　金：中国地质调查"华北重大岩浆事件及其成矿作用和构造背景综合研究"(No.1212014121079);中国地质调查"二连-东乌旗成矿带西乌旗和白乃庙地区地质矿产调查"(No.DD20160041);中国地质调查"兴蒙造山带中段古生代花岗岩的组成;性质;时代和成矿作用研究"(No.1212011121079)

摘　　要：兴蒙造山带中段锡林浩特跃进地区出露一套石炭纪侵入岩,具有类似岛弧侵入岩的岩石组合(花岗闪长岩、英云闪长岩、石英闪长岩)和地球化学特征.锆石LA-MC-ICP-MS U-Pb测年结果表明,这套侵入岩形成时代为310~330Ma,属于石炭纪中晚期.岩石地球化学分析表明,跃进侵入岩属于钠质钙碱性系列岩石;A/CNK范围为0.86~1.17,大多属于准铝-弱过铝质系列;样品均具有较高的Mg~#值,范围为47.5~55.8;微量元素分析表明,跃进侵入岩具有Rb、Ba、Th、U、K等大离子亲石元素的富集,Nb、Ta、P、Ti等高场强元素的亏损;稀土总量较低(3.62×10^(-6)~172.33×10^(-6),平均值为118.33×10^(-6)),具有轻稀土富集的配分模式,(La/Yb)_N大于1,范围为2.48~9.44,重稀土分馏较弱,(Gd/Yb)_N范围为1.19~1.96,具有弱的Eu负异常(δEu值0.70~1.04).跃进侵入岩均具有亏损的Hf同位素组成,^(176) Hf/^(177) Hf范围为0.282 651~0.282 870,ε_(Hf)(t)均为正值,范围为+2.0^+9.9,地壳存留模式年龄T_(DM)~C范围为829~1 536Ma,集中于900~1 200Ma;(^(87)Sr/^(86)Sr)i范围为0.703 7~0.704 8,(^(143) Nd/^(144) Nd)_i范围为0.512 320~0.512 401,ε_(Nd)(t)均为正值(+2.1^+3.6),二阶段Nd模式年龄T_(DM2)较集中,为新元古代(793~918Ma).跃进侵入岩是在石炭纪活动大陆边缘的背景下,由中元古代晚期-新元古代早期的新生基性下地壳物质,在俯冲流体及岛弧基性岩浆的共同作用下部分熔融形成的,表明石炭纪中晚期兴蒙造山带中段仍然存在板块俯冲,古亚洲洋并未关闭.The study of magmatism can reveal the structure and tectonic evolution of the orogeny.In this paper,we present zircon LA-MC-ICP-MS U-Pb dating,Hf-Sr-Nd isotopic compositions and whole rock geochemical data of the Carboniferous Arc intrusive rocks from Yuejin region of Xilinhot,central part of the Xingmeng Orogenic Belt.The rock suit consists of three major rock types,i.e.,granodiorite,tonalite and quartz-diorite,with zircon U-Pb ages ranging from 310±1 to 330±1 Ma.Geochemically,these rocks show moderate SiO_2,high and variable Na_2O,Al_2O_3,and CaO contents,but low K_2O,FeO tand MgO contents.The Na_2O/K_2O ratios are all higher than 1（1.05-2.68,average of 1.95）,while these rocks are of Calc-Alkalineseries.The A/CNK ratios range from 0.86 to 1.17,indicating most of samples are meta-to weak per-aluminous series.The Mg~#are moderately high,from 47.5-55.8.The trace elemental data of these rocks display enrichment of LILEs,such as Rb,Ba,Th,U,K,but depletion of HFSE,i.e.,Nb,Ta,P and Ti.The total REE contents are low（3.62×10^（-6）-172.33×10^（-6）,average of 118.33×10^（-6））with moderate fractionation between LREE and HREE（（La/Yb）_Nrange from 2.48-9.44）,while weak negative Eu abnormity are observed（δEu range from 0.70 to 1.04）.The in-situ zircon Hf isotopic analysis show depleted compositions with ^（176） Hf/^（177） Hf ratios varying from 0.282 723 to 0.282 863,ε_（Hf）（t）values from ＋2 to ＋9.9 and Hf two stage model ages（T_（DM）~C）from 829 to 1 536 Ma（concentrating from 900 to 1 200 Ma）.The whole rock Sr-Nd isotopic analysis of（^（87） Sr/^（86） Sr）irange from 0.703 7 to 0.704 8,（^（143） Nd/^（144） Nd）_i range from 0.512 320 to 0.512 401,with positiveε_（Nd）（t）（＋2.1 to＋3.6）,indicating depleted source,and the Nd two stage model ages（T_（DM2））are of Neoproterozoic（793-918 Ma）.The rock suit,whole rock geochemistry,Hf-Sr-Nd isotopic characteristics indicate that Yuejin Carboniferous intrusive rocks were formed in act

关 键 词：石炭纪 岛弧型侵入岩 活动大陆边缘 兴蒙造山带 大洋俯冲 新生地壳 

分 类 号：P583[天文地球—岩石学]