地质学报2017，Vol.91Issue(2)：384-399,16.
西藏玛依岗日印支期增生杂岩透入性石英脉的变形期次及流体包裹体特征
Polyphase Deformation and Fluid Inclusion Characteristic of Pervasive Syntectonic Quartz Veins in the Mayer Kangri Indosinian Accretionary Complex, Tibet
摘要
Abstract
The establishment of the metamorphism and deformation stages of epimetamorphic elastic rock complex in orogenic belt will contribute to determining the forming mechanism of accretionary complex and constrain the accretion-exhumation process of oceanic crust subcution zone.Medium-or small-scale structure analyses on the Indosiniana ccretionary complex in the Mayigangri area of central Qiangtang suggest that the structural style is the coaxial superimposition of E W-trending simple shear deformation of Triassic subduction of oceanic crust and N S-trending compressional deformation during convergent stage,which was reformed slightly by the Cenozoic nearly N S-trending buckle folding on shallow tectonic level.The complex developed three distinct foliations which correspond to the above three stages,with the two earlier ones usually accompanied with epimetamorphism.The C-type foliation S1 of the first stage (M1D1) in the clastic rock is showed as penetrative syntectonic pressolution quartz veins on the regional scale.The microscopic temperature-measuring experiment for fluid inclusions found that a large amount of primary immiscible boiling inclusion groups occurred in the quartz veins and can be grouped into CO2-rich three-phase inclusions and NaCl-H2O solution two-phase (gas-liquid) inclusions.The both inclusions show a coincident complete homogenization temperature of 300 ～ 400℃ which represents the metamorphic temperature of the M1 D1.The salinity-P/T isochore diagram of non-boiling gas-liquid two-phase inclusions shows a mean trapping pressure of 0.28 GPa,indicating the depth of the M1D1 is ～ 11.3 km.The prograde metamorphism of accretionary complex shows varied metamorphic facies series,with the shallow part of subduction channel characterized by medium P/ T metamorphic facies series and the middle deep part feature high P/T metamorphic facies series.The exhumation retrometamorphic P-T-t paths of high-pressure metamorphic rocks exhibit as cooling type.Blueschists and eclogites exhumed into the epimetamorphic complex at late Triassic (211～221Ma),which was concurrent with the closure time of the paleo-Tethys ocean.After that,the transient convergence of North Qiangtang terrane and south Qiangtang accretionary terrane resulted in the second stage intense compressional deformation (M2D2) and syn-collision type intermediate-acid magmatism along the Longmu Co Shuanghu suture.关键词
羌塘/石英脉/增生杂岩/变质变形/流体包裹体Key words
Qiantang/quartz vein/accretionary complex/deoformation and metamorphism/fluid inclusion引用本文复制引用
崔玉良,王根厚,姚尧,梁晓..西藏玛依岗日印支期增生杂岩透入性石英脉的变形期次及流体包裹体特征[J].地质学报,2017,91(2):384-399,16.基金项目
本文为中国地质调查局项目(编号1212011221081、12121010818014、1212011221115)、中国地质大学(北京)优秀教师基金项目(编号2-9-2014-004)及国家自然科学基金青年基金项目(编号41402177)联合资助成果. （编号1212011221081、12121010818014、1212011221115）
