【摘要】 藏东嘉玉桥变质杂岩分布于班公错-怒江缝合带南西,出露宽度约15～20km,延伸长度约120km。藏东嘉玉桥变质杂岩与上覆中侏罗统呈滑脱断层接触,滑脱带内发育各种韧性剪切组构。滑脱带内钠长石英构造片岩中石英呈矩形条带,多硅白云母与石英矩形条带构成S-C组构,石英颗粒应变测量表明Flinn图解K=∞,代表近水平伸展滑脱。获得多硅白云母变质条件相当于蓝片岩相,压力属于高压变质相,多硅白云母测年结果为167.27±0.99 Ma,为中侏罗世高压剪切作用,暗示班公-怒江缝合带中侏罗世伸展与高压剪切作用密切相关。更多还原

【Abstract】 Jiayuqiao metamorphic complex is located at the southwestern of Bangong-Nujian suture with a width of 15～20km and a length of more than 120km.A detachment fault,which includes variable of ductile shearing fabrics,separated the Jiayuqiao metamorphic complex in the core from the middle Jurassic in the cover.Phengite was first identified in this detachment fault.Within the detachment fault,the rectangle quartz ribbons form the S-foliation and Phengites form the C-foliation,and both combining produce typical S-C fabric.Strain measurements for the quartz grain give K=∞when plotting in Flinn diagram,which indicates a strongly sub-horizontal detachment deformation.The rectangle quartz ribbons indicate a metamorphic grade of high-greenschist to low amphibolite facies,while EMP analyzed results of the phengite plot in the metamorphic grade of blueschist with a high pressure.The separated phengite was dated at 167.27±0.99 Ma using the ⁴⁰Ar/³⁹Ar method,and thus revels a middle Jurassic high-pressure shearing tectonic event occurred in eastern Tibetan,and might implicate that the Banggong-Nujiang suture first formed at middle Jurassic.更多还原