The Red River Shear Zone (RRSZ), which extends from eastern Tibet to the South China Sea, plays a central role in the hypothesis that strike\|slip extrusion of Indochina accommodated a significant portion of Indo\|Asi...The Red River Shear Zone (RRSZ), which extends from eastern Tibet to the South China Sea, plays a central role in the hypothesis that strike\|slip extrusion of Indochina accommodated a significant portion of Indo\|Asian convergence. The massifs of the RRSZ, the only known mid\|crustal section exposed through a transform plate boundary, contain high\|grade metamorphic rocks that are believed to have been plastically deformed in a left\|lateral sense during the mid\|Tertiary. While the history of diachronous transtension along the RRSZ was previously obtained for temperatures below the brittle\|ductile transition from argon thermochronometry, the precise timing of high temperature deformation and the magnitude of strain have not been directly determined. This is a significant limitation to testing the extrusion model as magnetic anomalies from the South China Sea, interpreted to be a pull apart basin at the SE termination of the RRSZ, specifically predict that slip occurred between 35～17Ma at a rate of 3～5cm/a.展开更多
哀牢山—红河断裂带位于青藏高原东南缘,由青藏高原延入南海,是一条分割华南地块与印支地块的构造分界线,在地貌上也是一条醒目的分界线。纵向上由4个北西向的长条状变质带组成（雪龙山、点苍山、哀牢山和Day Nui Con Voi变质带）,长约1...哀牢山—红河断裂带位于青藏高原东南缘,由青藏高原延入南海,是一条分割华南地块与印支地块的构造分界线,在地貌上也是一条醒目的分界线。纵向上由4个北西向的长条状变质带组成（雪龙山、点苍山、哀牢山和Day Nui Con Voi变质带）,长约1 200 km。横向上分高级变质带和低级变质带,二者之间为倾向北东的哀牢山逆冲断裂带,其中高级变质带主要由元古界高级片麻岩、混合岩.展开更多
越南西北部Pu Sam Cap高钾碱性杂岩位于哀牢山剪切带南段西侧,由粗面岩、煌斑岩、碱性正长岩与碱性花岗岩组成。其中粗面岩不整合于晚白垩世陆相沉积岩之上,碱性侵入岩侵入到三叠纪陆源沉积岩、侏罗纪流纹岩及40～35Ma含角闪石二长岩-...越南西北部Pu Sam Cap高钾碱性杂岩位于哀牢山剪切带南段西侧,由粗面岩、煌斑岩、碱性正长岩与碱性花岗岩组成。其中粗面岩不整合于晚白垩世陆相沉积岩之上,碱性侵入岩侵入到三叠纪陆源沉积岩、侏罗纪流纹岩及40～35Ma含角闪石二长岩-花岗岩中。该杂岩的岩石具有低TiO2(<0.8%)、P2O5(<0.64%)和FeO*(<7.74%),高Na2O(1.41%～4.5%)和K2O(5.22%～9.4%)的地球化学属性,属于高钾碱性玄武质到高钾碱性长英质岩浆岩类型与钾质至超钾质岩浆系列。这套岩石富集大离子亲石元素LILE、轻稀土元素LREE和一组相容元素,具有明显的Ta、Nb和Ti异常,表明Pu Sam Cap高钾碱性杂岩形成于与俯冲带有关的大陆弧和后碰撞弧构造环境。锆石LA-ICPMS U-Pb年代学研究表明碱性正长岩与碱性花岗岩分别形成于32.70±0.24Ma、35.1±0.06Ma,上述年龄代表了Pu Sam Cap高钾碱性杂岩的侵入岩结晶年龄。两个样品中锆石的εHf(t)变化范围分别为-2.8～2.5和-4.9～0.1,在t-εHf(t)相关图上分析点落在下地壳和亏损地幔演化线之间,两阶段模式年龄变化范围为950～1286Ma和1107～1421Ma。该杂岩的εNd(t)变化范围-5.63～-3.26,具有低143Nd/144Nd比值(0.512336～0.512447)和高87Sr/86Sr比值(0.706254～0.707273),Sr-Nd同位素相关图上接近于EM2地幔端元趋势线,与大理地区新生代高钾岩浆岩十分相似,表明PuSamCap高钾碱性杂岩的岩浆是幔源岩浆和壳源岩浆的混合结果,同时可与大理地区新生代高钾岩浆岩对比,它们形成于哀牢山-红河左行走滑活动之前,墨江古特提斯洋盆的消减与印度-欧亚陆陆碰撞活动提供了宏观区域性构造背景。展开更多
文摘The Red River Shear Zone (RRSZ), which extends from eastern Tibet to the South China Sea, plays a central role in the hypothesis that strike\|slip extrusion of Indochina accommodated a significant portion of Indo\|Asian convergence. The massifs of the RRSZ, the only known mid\|crustal section exposed through a transform plate boundary, contain high\|grade metamorphic rocks that are believed to have been plastically deformed in a left\|lateral sense during the mid\|Tertiary. While the history of diachronous transtension along the RRSZ was previously obtained for temperatures below the brittle\|ductile transition from argon thermochronometry, the precise timing of high temperature deformation and the magnitude of strain have not been directly determined. This is a significant limitation to testing the extrusion model as magnetic anomalies from the South China Sea, interpreted to be a pull apart basin at the SE termination of the RRSZ, specifically predict that slip occurred between 35～17Ma at a rate of 3～5cm/a.
文摘越南西北部Pu Sam Cap高钾碱性杂岩位于哀牢山剪切带南段西侧,由粗面岩、煌斑岩、碱性正长岩与碱性花岗岩组成。其中粗面岩不整合于晚白垩世陆相沉积岩之上,碱性侵入岩侵入到三叠纪陆源沉积岩、侏罗纪流纹岩及40～35Ma含角闪石二长岩-花岗岩中。该杂岩的岩石具有低TiO2(<0.8%)、P2O5(<0.64%)和FeO*(<7.74%),高Na2O(1.41%～4.5%)和K2O(5.22%～9.4%)的地球化学属性,属于高钾碱性玄武质到高钾碱性长英质岩浆岩类型与钾质至超钾质岩浆系列。这套岩石富集大离子亲石元素LILE、轻稀土元素LREE和一组相容元素,具有明显的Ta、Nb和Ti异常,表明Pu Sam Cap高钾碱性杂岩形成于与俯冲带有关的大陆弧和后碰撞弧构造环境。锆石LA-ICPMS U-Pb年代学研究表明碱性正长岩与碱性花岗岩分别形成于32.70±0.24Ma、35.1±0.06Ma,上述年龄代表了Pu Sam Cap高钾碱性杂岩的侵入岩结晶年龄。两个样品中锆石的εHf(t)变化范围分别为-2.8～2.5和-4.9～0.1,在t-εHf(t)相关图上分析点落在下地壳和亏损地幔演化线之间,两阶段模式年龄变化范围为950～1286Ma和1107～1421Ma。该杂岩的εNd(t)变化范围-5.63～-3.26,具有低143Nd/144Nd比值(0.512336～0.512447)和高87Sr/86Sr比值(0.706254～0.707273),Sr-Nd同位素相关图上接近于EM2地幔端元趋势线,与大理地区新生代高钾岩浆岩十分相似,表明PuSamCap高钾碱性杂岩的岩浆是幔源岩浆和壳源岩浆的混合结果,同时可与大理地区新生代高钾岩浆岩对比,它们形成于哀牢山-红河左行走滑活动之前,墨江古特提斯洋盆的消减与印度-欧亚陆陆碰撞活动提供了宏观区域性构造背景。
