中国东部在晚中生代时(晚侏罗世-早白垩世)有广泛的中酸性岩浆活动,按照花岗岩的地球化学特征,大致可以划分为东北、华北和华南3个岩区。本文研究表明,按照 Sr 和 Yb 的含量,大致可以将花岗岩分为5类,即:高 Sr 低 Yb 型(Sr >400μg/g...中国东部在晚中生代时(晚侏罗世-早白垩世)有广泛的中酸性岩浆活动,按照花岗岩的地球化学特征,大致可以划分为东北、华北和华南3个岩区。本文研究表明,按照 Sr 和 Yb 的含量,大致可以将花岗岩分为5类,即:高 Sr 低 Yb 型(Sr >400μg/g,Yb<2μg/g)、低 Sr 低 Yb(Sr<400μg/g,Yb<2μg/g)、低 Sr 高 Yb(Sr<400μg/g,Yh>2μg/g)、高 Sr 高 Yb 型(Sr>400μg/g,Yb>2μg/g)以及非常低 Sr 高 Yb 型(Sr<100μg/g,Yb=2-18μg/g)花岗岩。东北和华南以发育低 Sr 高 Yb 花岗岩为主,有少量高 Sr 低 Yb 和非常低 Sr 高 Yb 类型的花岗岩分布;而华北则以高 Sr 低 Yb 型花岗岩(埃达克岩)最发育,低 Sr 高Yb、低 Sr 低 Yb 型和非常低 Sr 高 Yb 型花岗岩有少量分布。本文着重探讨了华北和华南花岗岩的特征,认为华北和华南花岗岩地球化学的区别可能主要与花岗岩源区成分和深度有关,且主要受源区深度的控制。如果花岗岩熔融的源区残留相由榴辉岩组成(石榴石+辉石+金红石+/-角闪石),则花岗岩明显亏损 HREE、Nb、Ta 和 Ti,而富集 Sr 和 Al,无明显的负铕异常,属于高 Sr 低 Yb(埃达克岩)类型;如果源区深度浅,由斜长角闪岩或麻粒岩组成(斜长石+辉石+角闪石),则花岗岩相对贫Sr 富 Yb。作者认为,华北和华南花岗岩地球化学特征上的上述差异,表明在晚中生代时(晚侏罗世-早白垩世),华北和华南的地壳厚度不同:华北较厚,华南较薄;华北经历了下地壳拆沉而华南无;华北和华南的下地壳成分不,华北较基性的下地壳拆沉后,留下的地壳平均成分与华南比偏中性。展开更多
During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacif...During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic （Type I） and intra-continental extensional basins （Type II）. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tufts and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous-Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geo- dynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc exten- sional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range tectonics between both shores of the Pacific, such as mantle plume展开更多
文摘中国东部在晚中生代时(晚侏罗世-早白垩世)有广泛的中酸性岩浆活动,按照花岗岩的地球化学特征,大致可以划分为东北、华北和华南3个岩区。本文研究表明,按照 Sr 和 Yb 的含量,大致可以将花岗岩分为5类,即:高 Sr 低 Yb 型(Sr >400μg/g,Yb<2μg/g)、低 Sr 低 Yb(Sr<400μg/g,Yb<2μg/g)、低 Sr 高 Yb(Sr<400μg/g,Yh>2μg/g)、高 Sr 高 Yb 型(Sr>400μg/g,Yb>2μg/g)以及非常低 Sr 高 Yb 型(Sr<100μg/g,Yb=2-18μg/g)花岗岩。东北和华南以发育低 Sr 高 Yb 花岗岩为主,有少量高 Sr 低 Yb 和非常低 Sr 高 Yb 类型的花岗岩分布;而华北则以高 Sr 低 Yb 型花岗岩(埃达克岩)最发育,低 Sr 高Yb、低 Sr 低 Yb 型和非常低 Sr 高 Yb 型花岗岩有少量分布。本文着重探讨了华北和华南花岗岩的特征,认为华北和华南花岗岩地球化学的区别可能主要与花岗岩源区成分和深度有关,且主要受源区深度的控制。如果花岗岩熔融的源区残留相由榴辉岩组成(石榴石+辉石+金红石+/-角闪石),则花岗岩明显亏损 HREE、Nb、Ta 和 Ti,而富集 Sr 和 Al,无明显的负铕异常,属于高 Sr 低 Yb(埃达克岩)类型;如果源区深度浅,由斜长角闪岩或麻粒岩组成(斜长石+辉石+角闪石),则花岗岩相对贫Sr 富 Yb。作者认为,华北和华南花岗岩地球化学特征上的上述差异,表明在晚中生代时(晚侏罗世-早白垩世),华北和华南的地壳厚度不同:华北较厚,华南较薄;华北经历了下地壳拆沉而华南无;华北和华南的下地壳成分不,华北较基性的下地壳拆沉后,留下的地壳平均成分与华南比偏中性。
基金funded by the National Basic Research Program of China(973 Program,No.2012CB416701)National Natural Science Foundation of China(Grant 40972132)was partly supported by the State Key Laboratory for Mineral Deposits Research of Nanjing University(No.2008-Ⅰ-01)
文摘During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic （Type I） and intra-continental extensional basins （Type II）. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tufts and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous-Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geo- dynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc exten- sional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range tectonics between both shores of the Pacific, such as mantle plume
