兴安地块南段霍布林岩体成因及其对蒙古-鄂霍茨克洋演化的启示  

Petrogenesis of the Huobulin granite in the southern part of the Xing'an Block and its insight into the evolution of the Mongol-Okhotsk Ocean

作　　者：李猛兴 王丽娟[2] 张利明[1] 王志强 罗栋[1] 李珍[1] LI Mengxing;WANG Lijuan;ZHANG Liming;WANG Zhiqiang;LUO Dong;LI Zhen(Shanxi Institute of Geological Survey Co.,Ltd.,Taiyuan 030006,Shanxi,China;Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences,Shijiazhuang 050061,Hebei,China)

机构地区：[1]山西省地质调查院有限公司,山西太原030006 [2]中国地质科学院水文地质环境地质研究所,河北石家庄050061

出　　处：《地质通报》2023年第9期1541-1555,共15页Geological Bulletin of China

基　　金：中国地质调查局项目《15万哈达图等四幅区域地质调查》(编号:12120113056400);自然资源部项目《我国典型地区大气水-地表水-地下水资源综合评估与水平衡研究——以滹滏平原为例》(编号:B201905)。

摘　　要：兴安地块在中晚侏罗世—早白垩世岩浆活动强烈,深入了解该时期的花岗岩成因和岩浆演化过程,对完善该地区中生代构造演化的认识及指导找矿具有重要的指示意义。从锆石U-Pb测年、地球化学特征等角度对兴安地块南段的霍布林岩体进行了全面研究。研究结果表明,霍布林岩体由正长斑岩、二长斑岩2种岩性组成,且以前者为主。二者的侵位年龄分别为157±1 Ma和139±1 Ma,形成于晚侏罗世、早白垩世2个阶段,是晚中生代早期构造岩浆事件的反映。地球化学研究表明,2种岩石均具有分异程度中等、富碱、富钠、准(弱)铝质及SiO_(2)与P_(2)O_(5)负相关的特点,再结合偏高的Zr含量(276.3×10^(-6)~499.5×10^(-6))及锆石饱和温度(788~881℃),将这2种岩石归属为高钾钙碱性-钾玄岩系列的I型花岗岩,并向A型过渡;岩体稀土元素总量中等—偏高,弱负Eu异常,轻稀土元素富集而重稀土元素亏损,富集大离子亲石元素Rb、Ba、Th、U、K,亏损高场强元素Ta、Nb、P、Ti,尤以正长斑岩更明显。地壳加厚和部分熔融作用可能是岩体主要形成机制,结合区域构造演化,认为其形成于蒙古-鄂霍茨克洋闭合后的后碰撞环境,区域应力场由挤压向伸展转变,进一步推测蒙古-鄂霍茨克洋在兴安地块南段的闭合时限早于157±1 Ma。The magmatic activity of the Xing'an Block was strong in the Middle and Late Jurassic-Early Cretaceous.A thorough understanding of the genesis and magmatic evolution of the granite in this period,which is of great significance for improving the understanding of the Mesozoic tectonic evolution and guiding the prospecting in this area.In this paper,the Hublin pluton in the southern part of Xing'an Block is comprehensively reported from the perspectives of zircon U-Pb chronology and geochemical characteristics.The study shows that the Hoblin rock body is composed of syenite porphyry and monzonite porphyry,and the former is the main lithology.The emplacement ages are 157±1 Ma and 139±1 Ma respectively,which were formed in the Late Jurassic and Early Cretaceous,reflecting the tectono-magmatic events of the early Late Mesozoic.In terms of geochemical characteristics,the two lithologies are characterized by moderate degree of differentiation,rich alkali,rich sodium,quasi(weak)aluminum and SiO_(2)-P_(2)O_(5)negative correlation,combined with the features of high Zr content(276.3×10^(-6)~499.5×10^(-6))and high zircon saturation temperature(788~881℃),the granite is classified as I-type granite of high potassium calc-alkaline potassium basalt series,which is transitioned to A-type granite.The total rare earth content of rock mass is medium to high,and weak negative europium is abnormal.The light rare earth is enriched while heavy rare earth is deficient,the large ion lithophile elements(Rb,Ba,Th,U,K)are enriched and the high field-strength elements(Ta,Nb,P,Ti)are depleted,especially in enesite porphyry.The crustal thickening and partial melting may be the main formation mechanism of the rock mass,combined with regional tectonic evolution,which was formed in the post-collision environment after the closure of the Mongolian-Okhotz Ocean,and the regional stress field changed from compression to extension.It is further inferred that the closing time of the Mongolian-Okhotz Ocean in the southern part of the Xing'an Block w

关 键 词：兴安地块 蒙古-鄂霍茨克洋 Ⅰ型花岗岩 岩石成因 霍布林岩体 地质调查工程 内蒙古 

分 类 号：P581[天文地球—岩石学] P534.5[天文地球—地质学]