南海及邻区岩浆岩时空分布特征及机制

Spatio-temporal distribution pattern of magmatic rocks and mechanism in the South China Sea and adjacent areas

南海的岩浆作用自始至终高度活跃,岩浆活动规模远远超出以前的想象。根据地壳发展阶段及其产生的岩浆作用强度和类型的差异,结合岩石同位素年龄资料,将南海及邻区划分为前吕梁期、吕梁期、晋宁期、加里东期、海西期、印支期、燕山期、喜马拉雅期等8个岩浆作用时期,主要分布于南海及周缘的广东、广西、海南岛、台湾岛、中南半岛、加里曼丹岛、菲律宾群岛,时代从前吕梁期至喜马拉雅期均有出露。南海及邻区最老的岩浆岩是在中南半岛出现的太古代黑云母花岗岩、紫苏花岗岩和辉长岩;最新的现代岩浆岩海陆均有发现,南海西南部和菲律宾等地区至今还有火山喷发岩浆活动。南海海区岩浆岩以燕山期和喜马拉雅期为主,燕山期以中酸性侵入岩为主,广泛分布于南海陆缘,尤其南海北部和西南部最甚;喜马拉雅期以强烈的基性、超基性岩浆活动为主,遍布于整个南海海区,以玄武岩为主。总体上,海区岩浆活动要比陆区晚。

Magmatism in the South China Sea has been active for long.According to the evolutionary stage of the crust and the difference in the intensity and type of the magmatism,combined with the isotopic age data from magmatic rocks,the magmatic activities in the South China Sea and its adjacent areas can be divided into eight stages,i.e.the pre-Luliang,Luliang,Jinning,Caledonian,Hercynian,Indosinian,Yanshanian and Himalayan stages.Magmatic rocks from pre Luliang to Himalayan period are widely distributed in the South China Sea and its surrounding areas such as Guangdong,Guangxi,the Hainan Island,the Taiwan Island,the Indochina Peninsula,the Kalimantan island and the Philippine islands.The oldest magmatic rocks,the Archean biotite granite,perilla granite and gabbro,are outcropped in the Indochina Peninsula;while the latest modern magmatic rocks occur both on land and in the sea.Volcanic eruption remains active up to present.The region of the South China Sea is dominated by the Yanshanian intermediate-acid intrusive magmatic rocks,which are mainly distributed on the continental margin of the South China Sea,especially in the north and southwest.In the Himalayan period,however,the region is dominated by strong basic and ultrabasic magmatic activities,mainly consisting of basaltic rocks.In general,the magmatic activity in sea area is lagged behind that on land.