点苍山-哀牢山变质杂岩带中、北段多期花岗质岩浆事件及其构造意义
发布时间：2019-07-23 12:50
【摘要】：点苍山-哀牢山变质杂岩带位于青藏高原东南缘扬子板块与印支板块的结合部位。杂岩带经历了多期构造-岩浆-变质事件的叠加,带内物质组成极其复杂,是研究古特提斯演化、印度-欧亚板块俯冲-碰撞-隆升以及渐新世印支地体沿红河-哀牢山左行走滑侧向挤出的关键地区。本文对点苍山-哀牢山变质杂岩带中、北段戛洒地区11件花岗质岩石进行了LA-ICPMS锆石年代学和岩石地球化学分析,研究揭示出新元古代、中三叠世、始新世和渐新世四期不同类型的花岗质岩浆活动。其中4件花岗质岩石中锆石206Pb/238U加权平均年龄为780.0±6.3Ma~743.6±6.7Ma,部分岩石内发育有渐新世深熔锆石;1件花岗质片麻岩内27颗锆石的206Pb/238U加权平均年龄为234.3±2.0Ma;3件花岗斑岩锆石U-Pb测年获得36.67±0.54Ma~33.01±0.39Ma的加权平均年龄;3件花岗质片麻岩/糜棱岩中获得渐新世(28.58±0.57Ma~24.53±0.29Ma)侵位年龄。岩石地球化学研究揭示新元古代花岗质岩石具有较高的Cu、V、Zn、TiO_2含量及较高铝指数,A/CNK变化范围为1.09~1.13,TiO_2含量为0.44~0.60;中三叠世花岗岩具有钙碱性特征,A/CNK1.0,R1-R2图解中落入深熔花岗岩范围内;始新世花岗岩具有高Sr、Ba、K_2O含量,高Sr/Y、Sr/Nd、Ba/Th比值,低Nd、Na)2O含量的特点,岩石中全碱含量为9.2%~10.4%,Sr/Y值为48.8~94.5,Sr/Nd值为30.4~65.3,Ba/Th值为151~358;渐新世花岗岩全碱含量较低变化范围为3.25~9.03,A/CNK范围为1.09~1.14,属富铝质S型花岗岩。花岗质岩石野外产状、锆石年代学与岩石地球化学综合研究揭示新元古代花岗质岩石可能属扬子板块西缘原特提斯洋俯冲形成的陆缘岩浆弧,印支期造山作用过程中卷入到杂岩带内,新生代区域性走滑剪切使岩石进一步发生变形和深熔;中三叠世花岗岩为古特提斯洋闭合后扬子板块与印支板块碰撞后伸展构造热事件的响应;始新世花岗质岩石为印度-亚欧板块碰撞后伸展背景下地幔上涌交代下地壳进而产生的富钾花岗质岩石,且侵位年代由北向南逐渐变新记录了印度-亚欧板块汇聚角度的调整过程;渐新世花岗质岩石为红河-哀牢山剪切-走滑抬升过程中变沉积岩、新元古代和晚二叠世-三叠纪花岗质岩石的部分熔融而成。
[Abstract]:The point Cangshan-Ailaoshan metaphorical complex belt is located at the junction of Yangtze plate and Indochina plate in the southeast margin of Qinghai-Xizang Plateau. The complex rock belt has experienced the superposition of multiple tectonic-magmatic-metaphorical events, and the material composition in the belt is extremely complex, which is the key area for the study of the evolution of ancient Tethys, the subduction-collision-uplift of the Indochina-Eurasian plate and the lateral extrusion of the Oligocene Indochina along the left walking and sliding of Honghe-Ailaoshan. In this paper, LA-ICPMS zircon chronology and petrogeochemistry analysis of 11 granitic rocks in the Cangshan-Ailaoshan metamorphic complex belt in the northern section of the North Section have been carried out. The study reveals different types of granitic magmatic activities in Neoproterozoic, Middle Triassic, Eocene and Oligocene. The weighted average age of zircon 206Pb/238U in 4 granitic rocks is 780.0 卤6.3 Ma~743.6 卤6.7 Ma, and Oligocene deep melting zircon is developed in some rocks, and the 206Pb/238U weighted average age of 27 zircon in 1 granitic gneiss is 234.3 卤2.0 Ma. The weighted average age of zircon U-Pb is 36.67 卤0.54Ma~33.01 卤0.39Ma. The emplacement age of Oligocene (28.58 卤0.57 Ma~ 24.53 卤0.29 Ma) was obtained from three granitic gneiss / mylonite. The study of petrogeochemistry shows that the Neoproterozoic granitic rocks have high Cu,V,Zn,TiO_2 content and high aluminum index, the variation range of A/CNK is 1.09 鈮，
本文编号：2518164
[Abstract]:The point Cangshan-Ailaoshan metaphorical complex belt is located at the junction of Yangtze plate and Indochina plate in the southeast margin of Qinghai-Xizang Plateau. The complex rock belt has experienced the superposition of multiple tectonic-magmatic-metaphorical events, and the material composition in the belt is extremely complex, which is the key area for the study of the evolution of ancient Tethys, the subduction-collision-uplift of the Indochina-Eurasian plate and the lateral extrusion of the Oligocene Indochina along the left walking and sliding of Honghe-Ailaoshan. In this paper, LA-ICPMS zircon chronology and petrogeochemistry analysis of 11 granitic rocks in the Cangshan-Ailaoshan metamorphic complex belt in the northern section of the North Section have been carried out. The study reveals different types of granitic magmatic activities in Neoproterozoic, Middle Triassic, Eocene and Oligocene. The weighted average age of zircon 206Pb/238U in 4 granitic rocks is 780.0 卤6.3 Ma~743.6 卤6.7 Ma, and Oligocene deep melting zircon is developed in some rocks, and the 206Pb/238U weighted average age of 27 zircon in 1 granitic gneiss is 234.3 卤2.0 Ma. The weighted average age of zircon U-Pb is 36.67 卤0.54Ma~33.01 卤0.39Ma. The emplacement age of Oligocene (28.58 卤0.57 Ma~ 24.53 卤0.29 Ma) was obtained from three granitic gneiss / mylonite. The study of petrogeochemistry shows that the Neoproterozoic granitic rocks have high Cu,V,Zn,TiO_2 content and high aluminum index, the variation range of A/CNK is 1.09 鈮，
本文编号：2518164
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