内蒙古锡林郭勒杂岩解体及表壳岩系年代确定  

Dissolution and supracrustal rocks dating of Xilin Gol Complex,Inner Mongolia,China

作　　者：葛梦春[1] 周文孝[1] 于洋[1] 孙俊俊[1] 鲍建泉[1] 王世海[1] 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《地学前缘》2011年第5期182-195,共14页Earth Science Frontiers

基　　金：中国地质调查局1:5万锡林浩特市等4幅区域地质调查项目(1212010811005)和1:25万锡林浩特市区域地质调查项目(1212010510507)

摘　　要：近年来,对中亚造山带中是否存在微地块有诸多不同看法,其中对广泛出露的锡林郭勒杂岩的时代和原岩认识存在较大的分歧。经大比例尺填图和详细露头解剖发现,它囊括了不同岩类、不同变质程度、不同构造样式和形成时代的地质体。文中建议将其解体,对其中被厘定的表壳岩命名为"锡林浩特岩群",这是一套达到角闪岩相变质的夹有火山岩和磁铁石英岩的富铝质的泥质碎屑岩,被SHRIMP U-Pb年龄为739.6Ma的变辉长岩和奥陶纪"S"型片麻状电气石二云母花岗岩所侵位,其中锆石变质核年龄集中在1 005～1 026Ma。同位素年代学研究还表明,该岩群分别受到后期一系列热事件的改造。结合区域和研究区地质构造演化年表分析,本文将锡林浩特岩群的形成时代推定为中元古代,它证明了研究区存在前寒武纪变质基底岩系,同时也佐证了锡林郭勒微地块的存在。There are different opinions on the existence of microcontinents in Central Asian Orogenic Belt（CAOB） and on the formation age and original rock property of the widely outcropped Xilin Gol Complex.The Xilin Gol complex comprises geologic bodies of different rock types,different metamorphic degrees,various structural styles and different forming ages.We proposed to disintegrate the Xilin Gol Complex and select the supercrustal rocks there among to be named as ＂Xilinhot Group＂,which are aluminum-rich argillaceous clastic rocks with amphibolite facies metamorphism and with volcanic and magnetite-quartzite intercalated.The group was emplaced by a metagabbro at 739.6 Ma（SHRIMP age） and by an S-type gneissose tourmaline two-mica granite formed during the Ordovician with the zircon metamorphotic cores of U-Pb ages concentrated in 1005-1026 Ma.The study of isotopic geochronology also shows that the group was reformed by a series of thermal events later.In combination with the regional tectonic evolution,it is suggested that the Xilinhot Group was possibly formed during the Mesoproterozoic,which may prove the existence of Precambrian metamorphic basement rock series in the region,and provide the corroboration for the existence of Xilinhot microblocks.

关 键 词：内蒙古 锡林郭勒杂岩 锡林浩特岩群 SHRIMP 

分 类 号：P597.3[天文地球—地球化学] P588.3[天文地球—地质学]