祁连造山带东段早古生代葫芦河群变质碎屑岩中碎屑锆石LA-ICP-MSU-Pb年龄:源区特征和沉积时代的限定  

LA-ICP-MS U-Pb ages of detrital zircons from the meta-detrital rocks of the Early Palaeozoic Huluhe Group in eastern part of Qilian orogenic belt: Constraints of material source and sedimentary age

作　　者：裴先治[1,2] 李佐臣[1,2] 李瑞保[1,2] 裴磊[3] 刘成军[2] 高景民[2] 魏方辉[2] 吴树宽[2] 王银川[2] 陈有炘[2] 

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [2]长安大学地球科学与资源学院,陕西西安710054 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2012年第5期205-224,共20页Earth Science Frontiers

基　　金：国家自然科学基金项目(40972136;41172186;40572121);中国高等学校博士学科点专项科研基金项目(20110205110004);中央高校基本科研业务费专项资金项目(CHD2011TD020);中国地质调查局地质调查项目(200013000154)

摘　　要：祁连造山带东段葫芦河群的形成时代长期存在争议。选择葫芦河群变质碎屑岩为研究对象,运用LA-ICP-MS锆石U-Pb同位素年代学方法,探讨葫芦河群的形成时代和物源特征。结果表明,葫芦河群的2个样品碎屑锆石同位素年龄数据以及侵入其中的花岗岩同位素年龄表明,葫芦河群沉积时代限定为447～434Ma,其主体形成时代为早志留世。葫芦河群变质碎屑锆石年龄谱明显分为4组:(1)震旦纪—早古生代年龄组,426～595Ma,峰值为479Ma;(2)新元古代年龄组,738～981 Ma,峰值为887 Ma;(3)中元古代年龄组,1000～1 913Ma,峰值为1499Ma;(4)古元古代—新太古代年龄组,2053～2 872Ma,峰值为2448Ma。其中,早古生代年龄组可进一步细分为426～493 Ma和527～595 Ma两个年龄段,峰值分别为445 Ma和559Ma,前者年龄段指示其物源可能以邻近地区的北祁连造山带和西秦岭北缘构造带为主,是加里东期中南祁连和西秦岭微地块分别向北俯冲、碰撞产生的一系列火成岩在造山剥蚀后的沉积响应;后者年龄段则与北祁连造山带和西秦岭北缘构造带中泛非造山事件中的岩浆活动有关。新元古代年龄组可细分为738～799Ma、839～862Ma和902～981Ma 3个年龄段,峰值分别为768Ma、848Ma和948Ma,以902～981Ma年龄组为主;第一年龄段(738～799Ma)与北祁连造山带新元古代晚期岩浆事件的年龄大致相对应,与Rodi-nia超大陆的裂解事件相关;第二年龄段和第三年龄段(839～862 Ma、902～981 Ma)与中祁连地区和西秦岭北缘的新元古代早期构造岩浆事件年龄大致相对应,与Rodinia超大陆汇聚事件及岛弧型岩浆作用相关。中元古代年龄组可细分为1 000～1 197Ma和1 243～1 913Ma 2个年龄段,峰值分别为1 036Ma和1 593Ma,其物源可能来自祁连造山带和华北板块基底岩系。古元古代—新太古代年龄组反映了物源来自北祁连造山带和西秦岭北缘构造带的结晶基底,部分物源也有�There was much controversy for long over the formation age of the Huluhe Group in eastern part of Qilian orogenic belt.Choosing the meta-detrital rocks in the Huluhe Group as study objects,this article uses LA-ICP-MS zircon U-Pb isotope chronology to study the formation age and material source of the Huluhe Group.The results show that the detrital zircons isotope ages of the two samples from the Huluhe Group and the age of the granite intruded in it show that the sedimentary age of the Huluhe Group ranges from 447-434 Ma,mainly the early Silurian.The zircon age spectrum can evidently divided into four groups： Sinian-Early Paleozoic age group from 426-595 Ma,the peak value is 479 Ma;Neoproterozoic age group from 738-981 Ma,the peak value is 887 Ma;Mesoproterozoic age group from 1000-1913 Ma,the peak value is 1499 Ma;Paleoproterozoic-Neoarchaean age group from 2053-2872 Ma,the peak value is 2448 Ma.The Sinian-Early Paleozoic age group can further be divided into 426-493 Ma and 527-595 Ma,the peak values are 445 Ma and 559 Ma respectively.The former indicates that its material source mainly be the adjacent North Qilian orogenic belt and northern margin of the West Qinling tectonic zone,which is a sedimentary response to the orogenic erosion of a series of igneous rocks caused by the northward subduction and collision of the Middle-South Qilian and West Qinling micro-block in the Caledonian,respectively.The latter is related to the magmation of the Fan-African orogenic event in the North Qilian orogenic belt and northern margin of West Qinling tectonic zone.The Neoproterozoic age group can further be divided into 738-799 Ma,839-862 Ma and 902-981 Ma,the peak values are 768 Ma,848 Ma and 948 Ma respectively,and 902-981 Ma age datas have the largest proportion.The 738-799 Ma age datas are approximately corresponding to the age of Late Neoproterozoic tectonomagmatic event in the North Qilian orogenic belt,and are related to the breakup of the supercontinent Rodinia.The 839-862 Ma and 902-981 Ma age datas are approxima

关 键 词：碎屑锆石 LA-ICP-MS锆石U-PB年龄 物源 葫芦河群 祁连造山带 

分 类 号：P597[天文地球—地球化学]