论从俯冲增生杂岩带重建洋板块地层主要类型与序列: 以青藏特提斯二叠系为例

Reconstruction of main types for oceanic plate strata in the subduction-accretionary complex and feature of sequence for each type:an example from the Qinghai・Tibet Tethyan Permian strata

洋板块地层学是对具洋壳的盆地(大洋盆地、弧后和弧间盆地)在各种构造环境中形成的火成-沉积原生建造序列重建的地层学分支学科。洋板块地层(简称OPS)是指洋壳从洋中脊一直到海沟俯冲带之间形成的火成岩基底序列,以及沉淀在洋底基底序列之上的沉积岩和火山岩的盖层序列。OPS生成后在洋盆关闭历程中被传送进入海沟。在海沟中,部分被俯冲消减进入地幔,部分通过刮削拼贴、底劈拼贴和构造折返等方式堆积在海沟与弧前之间,形成俯冲增生杂岩(楔)带(简称SAC)。因此,如何从SAC中重建OPS序列是当前国际地学研究热点。OPS序列重建的关键是从SAC中划分出属于不同构造环境的亚类,在精细划分亚类的基础上,按不同的亚类分别进行OPS序列重建。本文以青藏特提斯二叠纪OPS为例,提出并论述了从SAC中划分OPS亚类的方案和各亚类的OPS序列模型。

The oceanic plate stratigraphy is a branch of stratigraphy and focuses on the reconstruction of igneous-sedimentary primary sequences in oceanic basins(including oceanic basin,back-arc basin and inter-arc basin).The oceanic plate strata(OPS)are defined as strata including the basement sequence of volcanic rocks formed in between mid-oceanic ridge and trench subduction zone,and the sedimentary cover of sedimentary and volcanic rocks on the oceanic floor.The OPS were transported into a trench system during the closure of an oceanic basin.In the trench system,the OPS were partly subducted into themantle,or partly accumulated between the trench and fore-arc basin by the scraping or bottom-splitting collage,and tectonic reentry,forming a subduction-accretionary complex(SAC)belt or wedge.Therefore,how to reconstruct the sequence of OPS ina SAC belt is now a hot topic in the world.The key for the sequence reconstruction of OPS is to recognize and divide different tectonic settings from the SAC,and to reconstruct the strata sequence for each setting.This paper proposes the scheme of OPS subdivisions in the SAC,taking the Permian Tethyan strata of the Qinghai-Tibet Plateau as an example,and discusses the OPS sequence model.