塔里木西南中-新元古界研究进展  

Advances in Meso-to Neoproterozoic stratigraphy of the southwestern Tarim

作　　者：叶现韬[1] 张传林 YE Xian-tao;ZHANG Chuan-lin(College of Oceanography,Hohai University,Nanjing 210098,China)

机构地区：[1]河海大学海洋学院,南京210098

出　　处：《地质调查与研究》2020年第2期161-168,共8页Geological Survey and Research

基　　金：江苏省自然科学基金项目“敦煌地块古元古代晚期(1.85 Ga)基性岩墙群的成因和构造意义(BK20170873)”;中央高校基本科研业务费项目“中太平洋海山区玄武岩成因研究(B200202137)”;国家自然科学基金项目“敦煌地块1.85 Ga基性岩墙群与碱性岩的成因和地质意义(41702197)”。

摘　　要：本文总结了近年来塔里木西南地区前寒武系研究成果,重新建立了塔里木西南地区中-新元古界年代地层格架。结合岩石组合、地球化学特征概括了主要地层单元的沉积环境。研究表明,塔里木西南中元古界包含喀拉喀什群和桑株塔格群,沉积年龄分别为~1.52 Ga和1.4~1.5 Ga;原归属于长城系的塞拉加兹塔格群解体为两部分,下部为~890 Ma的大火成岩省,上部为850~840 Ma的火山沉积岩系。原划分为古元古界的埃连卡特群重新厘定为新元古界青白口系(~800 Ma)。新元古代中晚期的沉积包括丝路群(<800~830 Ma)和恰克马克力克群(~750 Ma)。其中恰克马克力克群中两次冰期大致可与塔里木北缘贝义西冰期和特瑞爱肯冰期进行对比。综合年代学、地球化学、碎屑锆石年龄谱、岩石组合以及岩石变质变形特征,塔里木西南地体在~1.9 Ga汇聚到Columbia超大陆之上,之后从~1785到~1117 Ma一直处于裂解、拉张构造背景。~1.0 Ga时,塔里木西南地体汇聚到澳大利亚北缘。几乎同时,大洋沿着塔里木西南地体北缘俯冲,大约850 Ma时形成了弧后盆地,在盆地中沉积了以碳酸盐岩为主夹少量火山碎屑岩的塞拉加兹塔格群;~800 Ma时弧后盆地关闭,在塞拉加兹塔格群的基础上形成了前陆盆地,沉积了埃连卡特群;最终在750 Ma以后,前陆盆地关闭,塔里木形成了统一的基底。而后被动大陆边缘和裂谷盆地开始发育,形成新元古代中期到寒武纪未变质和未变形的地层单元。The Precambrian sequences of the southwestern Tarim is re-examined in the light of new zircon U-Pb ages from the volcanic and clastic rocks,respectively.These data reveal that the Kalakashi Group(KG)deposited at ca.1.52 Ga and another Mesoproterozoic member Sangzhutage Group(SZG)deposited during 1.5~1.4 Ga.It is noted that the lower volcanic member and upper clastic member of the Sailajiazitage Group(SG)were deposited at ca.890 Ma and 850~840 Ma,respectively.The Ailiankate Group(AG)deposited at ca.800 Ma,and the unmetamorphosed and undeformed Silu Group(SLG)and the Qiakemakelieke Group(QG)deposited during 830-800 Ma and later than^750 Ma,respectively.Rock assemblages coupled with geochemistry of the KG bimodal volcanic rocks indicate its deposition in a rift basin.The huge thickness of continental flood basalt erupting in a short time period from lower member of SG argue for a new Neoproterozoic Large Igneous Province and the rock assemblages of the upper member suggest a back-arc basin due to oceanic slab southward subduction along the Central Tarim.Rock assemblages,detrital zircon age spectra and its metamorphism and deformation features suggest that the AG clastic sequence most likely deposited at a foreland basin on the backarc basin sedimentary package while the middle to late Neoproterozoic SLG and QG carbonate–clastic–tillite sequences deposited at a passive marginal and/or rift basins.The Neoproterozoic evolution process of the southwestern Tarim demonstrates that the Neoproterozoic assemblage of the Tarim basement could have lasted till 760 Ma and the basement could be composed of independent continental terranes.

关 键 词：中-新元古界 沉积时代 构造演化 塔里木西南 

分 类 号：P534.3[天文地球—古生物学与地层学]