Crustal deformation and exhumation within the India-Eurasia oblique convergence zone: New insights from the Ailao Shan-Red River shear zone
Crustal deformation and exhumation within the India-Eurasia oblique convergence zone: New insights from the Ailao Shan-Red River shear zone
复制标题
印度-欧亚大陆斜交带内的地壳变形与折返：来自哀牢山-红河剪切带的新认识
DOI：
10.1130/b35975.1
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Peter Reiners
中科院分区：
文献类型：
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作者：
Zhang bo;Chen Siyu;Wang Yang;Peter Reiners
在印度与欧亚大陆碰撞期间，区域尺度的走滑剪切带在调节地块的侧向挤出、地块旋转以及变质岩的垂直剥露方面起到了关键作用，如喜马拉雅东构造结地区和中国云南西部的哀牢山 - 红河剪切带（ARSZ）所呈现的变形那样。我们报道了来自ARSZ中段点苍山地块的构造、云母氩/氩（Ar/Ar）、磷灰石裂变径迹（AFT）以及磷灰石（铀 - 钍）/氦（AHe）数据。这些构造数据显示，该地块形成一个区域尺度的背形，其东、西边缘分别以ARSZ的两个分支为界。片麻岩核部水平糜棱岩中部分熔融的构造证据表明，片麻岩在地壳中部经历了水平剪切变形。核部36 - 29 Ma的白云母Ar/Ar年龄代表冷却年龄。分别来自西部和南部剪切带绿片岩相糜棱岩的25 Ma和17 Ma的白云母Ar/Ar年龄被解释为记录了ARSZ中的变形。15 - 5 Ma的AFT年龄代表了地块中一个冷却/剥露缓慢的平静间隔。AHe结果表明，地块的快速冷却和最终剥露事件可能在3.2 Ma之前开始，或者可能在约5 Ma开始，并持续至今。核部的高温水平剪切层最初在印支地块上形成，沿构造边界局部形成背形，然后在始新世或早渐新世期间冷却通过云母Ar - Ar封闭温度，随后在早渐新世（约29 Ma）期间因沿ARSZ的左旋走滑运动而被改造并进一步剥露，一直持续到约17 Ma，然后自约5 Ma以来，因ARSZ两翼的维西 - 乔后和红河断层上的右旋正断层作用，地块发生最终剥露。背形的形成可能表明在与印 - 亚汇聚相对应的早期压扭环境下局部地壳增厚。浅地壳中沿ARSZ的大规模左旋韧性剪切容纳了印支地块的侧向挤出，并进一步促进了从晚渐新世到中中新世变质地块的垂直剥露。此外，自中中新世或早上新世以来沿ARSZ的运动学反转变化以及相关的冷却事件意味着构造从主要构造边界的应变局部化向与高原生长和扩张相对应的连续变形转变。
During the collision of India and Eurasia, .regional-scale strike-slip shear zones played .a key role in accommodating lateral extrusion of blocks, block rotation, and vertical exhumation of metamorphic rocks as presented .by deformation on the Ailao Shan-Red River .shear zone (ARSZ) in the Eastern Himalayan Syntaxis region and western Yunnan, .China. We report structural, mica Ar/Ar, .apatite fission-track (AFT), and apatite (UTh)/He (AHe) data from the Diancangshan .massif in the middle segment of the ARSZ. .These structural data reveal that the massif .forms a region-scale antiform, bordered by .two branches of the ARSZ along its eastern .and western margins. Structural evidence for .partial melting in the horizontal mylonites .in the gneiss core document that the gneiss .experienced a horizontal shear deformation .in the middle crust. Muscovite Ar/Ar ages .of 36–29 Ma from the core represent cooling .ages. Muscovite Ar/Ar ages of 25 and 17 Ma.from greenschist-facies mylonites along the .western and southern shear zones, respectively, are interpreted as recording deformation in the ARSZ. The AFT ages, ranging .from 15 to 5 Ma, represent a quiescent gap .with a slow cooling/exhumation in the massif. AHe results suggest that a rapid cooling .and final exhumation episode of the massif .could have started before 3.2 Ma, or likely .ca. 5 Ma, and continue to the present. The .high-temperature horizontal shearing layers .of the core were first formed across the Indochina Block, locally antiformed along the .tectonic boundaries, and then cooled through .the mica Ar-Ar closure temperature during .Eocene or early Oligocene, subsequently reworked and further exhumed by sinistral .strike-slip movement along the ARSZ during .the early Oligocene (ca. 29 Ma), lasting until.ca. 17 Ma, then final exhumation of the massif occurred by dextral normal faulting on the .Weixi-Qiaohou and Red River faults along .the limbs of the ARSZ since ca. 5 Ma. The .formation of the antiform could indicate local .crustal thickening in an early transpressional .setting corresponding to India-Asia convergence. Large-scale sinistral ductile shear .along the ARSZ in the shallow crust accommodated lateral extrusion of the Indochina .Block, and further contributed to the vertical .exhumation of the metamorphic massif from .the late Oligocene to the middle Miocene. .Furthermore, the change of kinematic reversal and associated cooling episodes along .the ARSZ since the middle Miocene or early .Pliocene imply a tectonic transfer from strain .localization along the major tectonic boundaries to continuous deformation corresponding to plateau growth and expansion.