| 芦西战,何鹏,刘晓,张焕,翁红波.阿尔金断裂北侧英格里克韧性剪切带地质特征、锆石U-Pb年龄及其对加里东运动时限的讨论[J].矿产勘查,2021,12(2):208-220 |
| 阿尔金断裂北侧英格里克韧性剪切带地质特征、锆石U-Pb年龄及其对加里东运动时限的讨论 |
| Geological characteristics and zircon U-Pb age of ductile shear zone in the Angelic, North Altun Tagh Fault: Constrains to the timing of Caledonian Movement |
| 投稿时间：2020-06-11 |
| DOI： |
| 中文关键词: 锆石U-Pb年龄 韧性剪切带 加里东运动早期 英格里克 阿尔金断北侧 |
| 英文关键词: zircon U-Pb age, ductile shear zone, Early Caledonian Period, Angelic, North Altun Tagh Fault |
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| 摘要点击次数: 1490 |
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| 中文摘要: |
| 阿尔金断裂带是中亚大陆内部、出露于青藏高原北部边缘的一条重要的走滑断裂带,为古生代经历过陆壳俯冲碰撞而形成的高压-超高压变质岩带。笔者在阿尔金断裂北侧发现了近东西向分布的英格里克韧性剪切带,这其中发育有大量韧、脆韧性变形构造,对其进行岩石学、运动学及年代学研究可为阿尔金断裂带研究提供一定依据,也为了解中国西部地区构造发展史提供了参考。通过岩石学分析,韧性剪切带内卷入岩石可分为2种,一是早期地质体经裂解作用形成的大型岩块,如新太古代-古元古代石英片岩岩块、长城纪大理岩岩块、蓟县纪角闪岩岩块和震旦纪角闪岩岩块,又有小型大理岩岩块、角闪岩块；二是经强烈挤压形成的基质,如糜棱岩化角闪岩、石英片岩、含炭质绿泥片岩,二者中“网结状构造”。在剪切带内发现有剪切透镜体,长英质条带,强直片麻理,鞘褶皱、紧闭同斜褶皱,左行不对称褶皱、石榴子石残斑、斜长石残斑。通过观察薄片可发现岩石中普遍发育有σ、δ型旋转碎斑、S-C组构,“云母鱼”“长石鱼”“拉丝”状石英,波状消光、亚晶粒旋转重结晶及核幔构造,眼球状长石斑晶形成“旋转雪球构造”,显示两期变质事件的石榴子石的环带状构造,石榴石变斑晶的斜长石、石英冠状边。在韧性剪切带中识别出韧性剪切褶皱、糜棱岩带(韧性剪切带)和脆性断裂三期构造,分别代表了构造期次的早晚。应用LA-ICP-MS锆石U-Pb定年法对3件样品进行分析,年龄峰值分别为1850~1950 Ma、900~1100 Ma和300~600 Ma；1450~1550 Ma、950~1150 Ma和400~500 Ma；550~650 Ma。由此可确定英格里克韧性剪切带形成于加里东运动早期,为陆壳俯冲产物,并经受了多期次构造运动。 |
| 英文摘要: |
| The Altun fault belt is an important strike-slip fault belt in the central Asian continent and outlying the northern edge of the qinghai-tibet plateau. The author in the north of the Altun Tagh Fault found nearly east-west distribution of Angelic ductile shear zone, the development has a huge number of ductile and brittle ductile deformation structure on the petrology, kinematics and chronology studies to provide a certain basis for the study of the Altun Tagh Fault zone, and provides reference to know the development of construction in western China. Through petrology analysis, in the ductile shear zone in rock can be divided into two kinds, one is formed by the early geological body by pyrolysis of a large rock, such as new Archean - Paleoproterozoic quartz schist rock, the Great Wall of Jixian marble rock, amphibolite rocks and sinian period amphibolite rocks, and there was a small flash block marble rock, angle. The second is the matrix formed by strong extrusion, such as mylonitized hornblende, quartz schist, carbonaceous green mud schist, in which the “network structure”. In the shear zone, there are shear lens body, long cellophane strip, ankylotic lamination, sheath fold, tightly closed synclinal fold, left asymmetric fold, garnet residual spot, plagioclase residual spot. By observing the chip can be found in rocks are widespread sigma, the delta type rotating mortar, S-C fabric, “mica fish”“feldspar fish”“drawing” quartz, wavy extinction, subgrain rotation recrystallization and nuclear curtain structure, figured out the formation of augen “rotating snowball structure”, according to two metamorphic events of garnet ring banded structure, garnet change of plagioclase phenocryst, Shi Yingguan shape edge. In the ductile shear zone, ductile shear fold, mylonite belt (ductile shear zone) and the three-stage brittle fracture structures are identified, which represent the tectonic period respectively. Three samples were analyzed by LA-ICP-MS zircon U-Pb dating, with peak ages of 1850-1950 Ma, 900-1100 Ma and 300-600 Ma, respectively 1450-1550 Ma, 950-1150 Ma and 400-500 Ma, 550-650 Ma. It can be concluded that the Angelic ductile shear zone was formed in the early caledonian period and is a subduction product of continental crust and has undergone several stages of tectonic movement. |
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