全吉地块北缘变质地体中-新元古代岩石的成因与构造演化研究

The Quanji massif is a remnant of cratonic fragments detached from the Tarim Block and has a metamorphic terrane with records of multipole tectonothermal events occurring on its northeastern border. This proposed project will carry out comprehensive studies of geology, petrography, mineral chemistry, whole-rock petrochemistry and Nd-Sr-Pb isotope, geochronology and zircon Hf isotope for granites including the ca.1.1 Ga I-type, 0.9-1.0 Ga high-K2O type and 0.5-0.60 Ga S-type granites, and metamorphosed Meso- to Neoproterozoic superacrustal rocks from this metamorphic terrane. The investigation subjects will cover petrogenesis, crustal growth and reworking history, tectonic settings for magmatism and deposit basin, compositional features of the provenance, tectonic affinity and metamorphic processes and geodynamics. For comparation, a study will also be made on the Wandonggou Group metamorphic Mesoproterozoic greensichsists of the basement and sandstone and basic volcanic rocks of the Nanhua-Cambrian Quanji Group covers. The research progresses will serve to understand the formation and evolution of the Northeastern metamorphic terrane, to determine the estern extension of the ca.1.1 Ga and 0.5-0.6 Ga granitoid and metamorphic belts, and to provide constraitions for deeper recognizing relationship of the Tarim Block with the global supercontinents during the Meso- to Neoproterozoic times.

全吉地块是从塔里木陆块离解出来的一个克拉通残片，该地块东北缘出露一个保存多期构造热事件的变质地体。本项目对该变质地体中约1.1 Ga的I－型花岗岩、0.9-1.0 Ga的钾质花岗岩和0.5-0.60 Ga的S-型花岗岩等花岗岩体和变质中、新元古代表壳岩系，开展地质学、岩相学、矿物化学、岩石化学和Nd-Sr-Pb同位素地球化学、同位素地质年代学和Hf同位素地球化学等综合研究。研究内容包括岩石成因、地壳生长与再造史、岩浆作用和沉积盆地的构造环境、物源区组成、构造属性、变质作用过程及其地球动力学特征等。项目还将与全吉地块的变质基底中元古代火山岩系和南华纪盖层全吉群的砂岩和基性火山岩进行对比研究。本研究成果将有助于了解全吉地块北缘变质地体的形成和演化，确定塔里木陆块约1.1 Ga和0.5-0.6 Ga两个花岗岩带和变质带的东延展布，深化认识塔里木陆块与全球晚中-新元古代末超大陆事件的演化关系。

项目综合研究了祁连地块西南缘乌北地体的变质表壳岩系和变质花岗岩的岩石单元、形成年龄、岩石成因、形成环境、物源区性质和表壳岩系的变质作用特征，以揭示祁连地块的早期演化和与邻区塔里木克拉通和全吉地块的亲缘性及其与全球古大陆演化的构造关系。.研究结果将乌北地体的变质表壳岩系由早-中期中元古代单元、晚中-早新元古代单元和晚新元古代-早古生代单元等三个构造岩性单元构成，厘定出1.6–1.5 Ga、1.1–0.9 Ga和~0.5 Ga，产有中元古代~1.5 Ga低压奥长花岗岩和~1.1 Ga巨斑状花岗闪长岩和新元古代~1.0 Ga似斑状二长花岗岩、~0.9 –0.8 Ga石榴子石花岗岩和~0.54 Ga花岗岩等五期花岗岩，认为乌北地体可能是卷入祁连造山带中的年龄最老、组成最复杂的前寒武纪地块。碎屑锆石年龄谱和地球化学特征揭示早-中期中元古代单元的沉积物源来自于因而亲缘于塔里木克拉通，沉积于大陆裂谷沉积环境，晚中-早新元古代单元的物源主要来自乌北地体早-中期中元古代单元和远程的东欧陆块和北美陆块的Laurentia或Baltica古大陆的碎屑物质混入，为弧前俯冲板片上堆积的沉积-火山物质。~1.5 Ga奥长花岗岩指示裂谷作用的进一步发展，随后~1.3–1.2 Ga洋壳俯冲弧相关变质作用和~1.1 Ga弧-陆碰撞变质作用催生了弧相关的花岗岩浆作用。碰撞后花岗岩浆作用则发生在~0.9 Ga之后。.乌北地体的形成与演化的新认识大大深化了祁连地块早期响应全球Columbia超大陆裂解和再汇聚过程中的长期俯冲、增生和碰撞形成下一个超大陆Rodinia超大陆的构造演化过程的了解。祁连地块不包括比它年老得多的全吉地块。