古老造山带洋板块地层

Reconstruction of Ocean Plate Stratigraphy from the ancient orogen

重点分析和总结了由前寒武纪增生复合体和造山带混杂岩重建的古老造山带洋板块地层,包括由英国威尔士安格尔西岛新元古代莫纳超群混杂岩重建的太平洋洋板块地层、由澳大利亚西北部皮尔巴拉早太古代克里夫维尔绿岩带重建的古印度洋洋板块地层。澳大利亚东皮尔巴拉地块大理石坝地区早太古代玄武岩—硅质岩—碎屑岩序列与日本二叠纪—三叠纪洋板块地层在岩石组成和地球化学特征方面具有高度的相似性,这一认识将为早太古代洋板块地层的沉积环境从高热流洋脊扩张区经过热点向低热流海沟陆源碎屑沉积区转变这一过程提供有力支持。从增生造山带洋板块地层保存的岩石记录看,不同年代洋板块地层的主要物质组成和岩石类型相似,因此在地球38亿年的演化进程中,洋壳扩张、海洋沉积、俯冲及增生的过程并没有显著变化;但随着时间推移,年轻造山带洋板块性质和洋板块地层组成与古老造山带相比,可能会发生一些变化。就古老造山带洋板块地层而言,前寒武纪的地幔温度略高,太古代局部熔融显著,熔融量大大超过洋壳扩张速率,因而没有形成席状岩墙群。

The paper focuses on reconstruction of the Oceanic Plate Stratigraphy(OPS)from the Precambrian accretionary complexes and mélange of ancient orogenic belts,including the Pacific OPS reconstructed from the Neoproterozoic Mona Supergroup mélange in Anglesey,Wales,United Kingdom,and the Paleo-Indian OPS reconstructed from the Early Archean Cleaverville greenstone belt,Pilbara,northwest Australia.The early Archean basalt-silicate-clastic sequence in the Marble Bar area of the East Pilbara Block of Australia is highly similar to the Permian-Triassic ocean plate strata of Japan in rock composition and geochemical characteristics.This conclusion will provide strong support for evolution of the sedimentary environments of the early Archean OPS from the high-heat flow ridge spreading area,through the hot spot,to the low-heat flow trench,terrigenous clastic depositional zone.According to the rock records of the OPS in the accretive orogenic belt,the main composition and rock types of the OPS strata from the Archean to the present are similar.Therefore,the processes of ocean spreading,deposition,subduction and accretion have not changed significantly during the Earth's 3.8-byr-history.However,the oceanic plate properties and the oceanic plate stratigraphic composition of young orogenic belts may have changed with time.Precambrian mantle temperature was slightly high,and the degree of partial melting was high in the Archean.The melting amount greatly exceeded the expansion rate of the ocean crust,so the sheet dike group did not form in ancient oceanic crust.