南沙地块构造格局及其演化特征

TECTONIC FRAMEWORK AND EVOLUTIONARY CHARACTERISTICS OF NANSHA BLOCK,SOUTH CHI NA SEA

将南沙地块及其周边地块置于统一的地球动力学背景下,根据地球物理、地层展布、构造变形等特征,确立了南沙地块的一级构造边界,提出南沙地块的演化与古南海及现今南海的演化密不可分。古南海分隔了南沙地块和加里曼丹—巴拉望地块,随着古南海由西南往东北的剪刀状南向俯冲封闭和现今南海的张开,南沙地块和加里曼丹—巴拉望地块之间先后在始新世—晚中新世发生B型俯冲、A型俯冲及碰撞作用,形成沙捞越俯冲碰撞带,并在该带北侧形成南沙地块前陆盆地区、南沙地块隆起区及南海深海盆3个构造单元。

When the Nansha block and its adjacent areas is considered in a un if ying geodynamic background, the first level tectonic boundaries, consisting of t he spreading ridge of the SW subbasin of South China Sea (SCS), the Wanan-Yuedo ng strike slip fault, the Sarawak subduction-collision belt and the Manila tren ch, for Nansha block was established and the close link of the evolution history of Nansha block to that of the paleo-SCS and modern SCS was proposed in this p aper. The plaeo-SCS separated the Nansha block from the Kalimantan-Palawan blo ck. With the scissors-like southward subduction and closure of the paleo-SCS f rom SW toward NE and the opening of the modern SCS, B-type subduction, A-type subduction and succeeding collision occurred between the Nansha block and the Ka limantan-Palawan block in Eocene to Late Miocene, which results in the formatio n of Sarawak subduction-collision belt as well as three tectonic units located to the north of the Sarawak belt, including the foreland basin area and the upli fted area of the Nansha block as well as the SW subbasin of SCS.