内蒙额济纳旗霍布哈尔地区构造片岩带的发现及其构造意义
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摘要
野外调查发现在靠近中蒙边界的额济纳旗霍布哈尔地区存在带状构造片岩,片理倾向南东,拉伸线理沿北东向,片岩内存在指示左行剪切的旋转碎斑系、不对称压力影等显微剪切组构。显微构造尺度上,片理结构由片理域与微片石组成,形成极易开裂的潜在破裂面。区内构造片岩是北东向韧性剪切带的组成部分,成因与韧性的剪切运动有关,经样品UY-1的LA-ICP-MS锆石U-Pb测年法测定,得到糜棱岩化的流纹斑岩年龄为286.3 Ma±2.0 Ma,后期侵入的闪长岩年龄为284.2 Ma±2.4 Ma,约束了构造片岩的形成时代为286.3 Ma～284.2 Ma(早二叠世)。结合区域地质资料,认为构造片岩带的形成与早二叠世阿尔金—东蒙古断裂的左行走滑剪切活动有关。
Field investigation shows that a structural schist zone occurs in Ejina Huobuhaer near the border of China and Mongolia.The schistosity in the zone dips toward the southeast with a northeast stretching lineation. Rotated porphyroclasts,pudding structures,mica fish as well as asymmetric pressure shadow indicate a sinistral shear deformation.The structural schist in the zone is composed of cleavage domain and microlithon domain and possesses easily splitted fractures.This deformation zone is actually part of the northeast trending ductile shear zone resulted from the ductile shear deformation in the area.LA-ICP-MS zircon U-Pb dating for sample UY-1 of mylonitized rhyolite porphyry yields an age of 286.3 Ma±2.0 Ma and the undeformed later intrusive diorite has an age of 284.2 Ma±2.4 Ma,indicating that the formation age of the structural schist is 286.3 Ma～284.2 Ma.It is considered that the structural schist zone is resulted from sinistral shear movement of Alty Tagh-East Mongolia fault in early Permian period.
Field investigation shows that a structural schist zone occurs in Ejina Huobuhaer near the border of China and Mongolia.The schistosity in the zone dips toward the southeast with a northeast stretching lineation. Rotated porphyroclasts,pudding structures,mica fish as well as asymmetric pressure shadow indicate a sinistral shear deformation.The structural schist in the zone is composed of cleavage domain and microlithon domain and possesses easily splitted fractures.This deformation zone is actually part of the northeast trending ductile shear zone resulted from the ductile shear deformation in the area.LA-ICP-MS zircon U-Pb dating for sample UY-1 of mylonitized rhyolite porphyry yields an age of 286.3 Ma±2.0 Ma and the undeformed later intrusive diorite has an age of 284.2 Ma±2.4 Ma,indicating that the formation age of the structural schist is 286.3 Ma～284.2 Ma.It is considered that the structural schist zone is resulted from sinistral shear movement of Alty Tagh-East Mongolia fault in early Permian period.
引文
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[22] 郑荣国,吴泰然,张文,等.阿拉善地块北缘雅干花岗岩体地球化学、地质年代学及其对区域构造演化制约[J].岩石学报,2013,29(8):2 666-2 675.
(1)甘肃省地质局地质力学区域测量队.中华人民共和国雅干幅、拐子湖幅1∶5×104区域地质调查报告[R].甘肃省地质局地质力学区域测量队,酒泉:1981.
(2)武警黄金第二支队.内蒙古额济纳旗生格嘎顺、霍布哈尔1∶5×104区域地质矿产调查报告[R].2017.
[2] 刘俊来.辽吉古裂谷内带顺层构造片岩的变形构造与变形机制[J].吉林地质,1991,4:1-8.
[3] 王根厚,贾建称,万永平,等.藏东巴青县北部酉西岩组构造片理形成及构造意义[J].地学前缘,2006,13(4):181-187.
[4] 孟元库,许志琴,马士委,等.藏南冈底斯地体谢通门—曲水韧性剪切带40Ar/39Ar年代学约束[J].地质论评,2016,62(4):795-805.
[5] 王廷印,刘金坤,王士政,等.阿拉善北部中蒙边界地区晚古生代拉伸作用及构造岩浆演化[J].中国区域地质,1993,(4):317-327.
[6] 吴泰然,何国琦.内蒙古阿拉善地块北缘的构造单元的划分及各单元的基本特征[J].地质学报,1993,67(2):97-108.
[7] 郭彦如,陈文,穆剑,等.阿尔金断裂系及其邻区中一新生代构造演化[J].地质论评,2002,48(增刊):169-176.
[8] YongjunYue,Juhn G.Liou.Two-Stage evolution model for the Altyn Tagh fault,China[J].Geology,1999,27(3):227-230.
[9] Molnar P and Tapponnier P.Cenozoic tectonics of Asia:Effects of a continental collision[J].Science,1975,189:419-426.
[10] Passchier C W,Trouw R A J.Microtectonics.2ed[M].Berlin:Springer-Verlag,2005.
[11] 徐畅,赵珊茸,何煦,等.大别山朱家冲二云石英片岩中石英双晶及交生特征[J].矿物岩石,2016,36(3):1-6.
[12] 凌贤长,刘春华.构造片岩评述[J].世界地质,1995,14(3):28-33.
[13] 王全伟,梁斌,谢启兴,等.青川地区青川断裂带的显微构造及其变形条件研究[J].矿物岩石,2000,20(1):87-90.
[14] 葛肖虹,任收麦,刘永江,等.中国西部的大陆构造格架[J].石油学报,2001,22(5):1-6.
[15] 陈柏林,崔玲玲,白彦飞,等.阿尔金断裂走滑位移的确定-来自阿尔金山东段构造成矿带的新证据[J].岩石学报,2010,26(11):3 397-3 394.
[16] Cowgill E,A Yin,X F Wang,et al.Is the North Altyn fault part of a strike-slip duplex along the Altyn Tagh fault system?[J].Geology,2000,28(3):255-258.
[17] Suvorov A I.Structural map and faults of Mongolia[M] Izvestiya Akademii Nauk SSSR,Seriya Geologicheskaya,1982,6:122-136.
[18] 李海兵,杨经绥,许志琴,等.阿尔金断裂带的形成时代—来自于同构造生长锆石U-Pb SHRIMP定年证据[J].地质论评,2001,3:315-316.
[19] 李海兵,杨经绥,许志琴,等.阿尔金断裂带印支期走滑活动的地质及年代学证据[J].科学通报,2001,46(16):1 333-1 338.
[20] 王云斌,丁雪峰,赵志刚,等.甘肃省三危山断裂带东段-片石山一带的韧性变形特征[J].西北地质,2005,38(4):8-13.
[21] 陈文彬,徐锡伟.阿拉善地块南缘的左旋走滑断裂与阿尔金断裂带的东延[J].地震地质,2006,28(2):319-323.
[22] 郑荣国,吴泰然,张文,等.阿拉善地块北缘雅干花岗岩体地球化学、地质年代学及其对区域构造演化制约[J].岩石学报,2013,29(8):2 666-2 675.
(1)甘肃省地质局地质力学区域测量队.中华人民共和国雅干幅、拐子湖幅1∶5×104区域地质调查报告[R].甘肃省地质局地质力学区域测量队,酒泉:1981.
(2)武警黄金第二支队.内蒙古额济纳旗生格嘎顺、霍布哈尔1∶5×104区域地质矿产调查报告[R].2017.