The late mesozoic granodiorites from the southwest basin in the South China Sea and its tectonic implication
The late mesozoic granodiorites from the southwest basin in the South China Sea and its tectonic implication
复制标题
DOI：
10.1007/s12583-012-0252-7
复制
发表时间：
2012-06
影响因子：
3.3
通讯作者：
Zhenguo Zhang;Yuansheng Du;Lian-feng Gao;Nian-qiao Fang;Shengxiong Yang;Jian Liu;Chengbing Song
中科院分区：
文献类型：
--
作者：
Zhenguo Zhang;Yuansheng Du;Lian-feng Gao;Nian-qiao Fang;Shengxiong Yang;Jian Liu;Chengbing Song
西南海盆是研究南海中国海起源与发展的关键。我们对它的边界、地质历史和海底的形成知之甚少，因为它具有复杂的区域构造背景，显著的沉积活动，但底岩很少。本文在南海中国海西南海盆南缘采集了花岗闪长岩样品。结果表明，样品中黑云母的40Ar-39Ar年龄为110.3±0.5 Ma，表明它们是早白垩世岩浆侵入的产物。样品的地球化学性质表明，其SiO_2、K_2O、Al_2O_3含量较高，而二氧化钛含量较低。构造判别图解表明，该样品可能代表了南海弧或弧前环境中与挤压有关的岩浆作用，样品主要属于同碰撞类型，其形成与造山作用有关。样品可能是构成裂谷系统边界的主要岩石的一部分。拉张裂解过程类似于红海的发育过程，在此过程中陆壳发生了裂陷和凹陷。西南盆地可能不是原始大洋，而是陆壳基底有限伸展形成的裂谷。当裂谷的宽度和深度达到一定规模时，就形成了洋壳。我们采集的花岗闪长岩样品提供了确定西南盆地边界的手段和线索，可能有助于研究人员扩展相关模式。它为分析南海的形成和发展提供了重要资料。
The southwest basin is a key to study the origin and development of the South China Sea (SCS). We do not know much about its boundaries, geological history, and the formation of its sea floor because it has a complex and highly regional structural background, notable sediment activity, and yet few floor rocks. Here a granodiorite sample was collected from the southern margin of the southwest basin of the South China Sea. The results indicated that the40Ar-39Ar ages of biotites in the sample are 110.3±0.5 Ma, suggesting that they were products of magmatic intrusion during the Early Cretaceous period. The sample’s geochemistry showed it had high SiO2, K2O, and Al2O3but low TiO2levels. Tectonic discriminant diagrams suggested that the sample might represent extrusion-related magmatism, either in an arc or forearc setting in the SCS area and that the sample mainly belonged to the syncollision type, whose formation was related to orogenies. The sample may be part of the main rock that made up the boundaries of rift system. The process of tension cracking was similar to the development of the Red Sea, in which the rifting and sagging occurred in the continental crust. The southwest basin may not be an original ocean, but a rift developed through finite extension on continental crust basement. The oceanic crust came into being when the width and depth of the rift valley reached a certain scale. The granodiorite sample we collected provides a means of determining the boundary of the southwest basin and the clues that may help researchers expand relevant models. It constitutes an important datum regarding the analysis of the formation and development of the SCS.