南沙海区及其周缘中-新生代岩浆活动及构造意义  

MESOZOIC-CENOZOIC MAGMATISM IN SOUTHERN SOUTH CHINA SEA AND ITS SURROUNDING AREAS AND ITS IMPLICATIONS TO TECTONICS

作　　者：周蒂[1] 刘海龄[1] 陈汉宗[1] 

机构地区：[1]中国科学院边缘海地质重点实验室,中国科学院南海海洋研究所,广东广州510301

出　　处：《大地构造与成矿学》2005年第3期354-363,共10页Geotectonica et Metallogenia

基　　金：国家"十五"社会公益研究计划(2001DIA50041-01);国家重点基础研究发展规划(G2000046702);中国科学院知识创新项目(KZCX2-SW-117)资助.

摘　　要：通过对南沙海区及其周缘地区中-新生代以来4个主要地质时期即燕山期、喜山早期、喜山晚期一幕和二幕各种类型岩浆岩的发育特征(包括时空分布、地球化学及构造环境)的综合分析,重构了研究区中-新生代岩浆活动的演化历程:燕山期(侏罗纪到白垩纪)在南沙西面和西南面陆区以中酸性岩浆活动为主,代表中生代东亚陆缘火山岩带的南段。同时在南沙与加里曼丹之间广泛发育的是基性-超基性岩,是在俯冲过程中折返到浅部的古南海洋壳碎片。喜山早期(古新世至始新世)岩浆活动微弱。喜山晚期一幕(晚渐新世至中中新世)在加里曼丹—卡加延一带岩浆活动相对重新活跃,西段主要有英安岩、花岗闪长岩、安山岩、闪长岩等,东段主要为玄武安山岩,但规模较小,似乎不足以构成与古南海俯冲伴生的火山岩带。喜山晚期二幕(晚中新世至第四纪)岩浆活动出现高峰,为大规模的中基性火山喷发,与燕山期及喜山早期截然不同,在中南半岛南部和加里曼丹岛中-北部尤为广泛,可能是该区出现上涌的地幔热团的指示。The spatial-temporal distribution, geochemistry, tectonic environment of Mesozoic-Cenozoic magmatism in the region of Nansha sea area in southern South China Sea and its adjacent areas are summarized. The Yanshanian period （from Jurassic to Cretaceous） was characterized mainly by intermediate-acid magmatic activities in the west and south, representing the extension of the SE Asian Mesozoic magmatic belt in Sundaland. Meanwhile,basic-ultrabasic rocks in the south between Nansha Islands and Kalimantan are representative of the oceanic crust of the proto-South China Sea that was incorporated into mélanges during its southward subduction. The Early Himalayan period （from Paleocene to Eocene） was relatively quiet in terms of magmatic activity. Then during the first epoch of the Late Himalayan period （from Late Oligocene to Middle Miocene） , magmatism was active again but was restricted to a zone extending from Sarawak to Cagayan, and is represented mainly by dacite, granodiorite,andesite, diorite in the west and by basaltic andesite in the east. The intensity and scale were probably too small to lead to formation of a volcanic arc related to the subduction of the proto-South China Sea. During the second epoch of the Late Himalayan period （from Late Miocene to Quaternary） the magmatic activity reached its climax, as largescale intermediate-basic volcanic eruption occurred in most parts of the area, especially in southern Indochina Peninsula and northern Kalimantan Island. This is perhaps indicative of an upwelling mantle hot-blob in the area.

关 键 词：岩浆活动 构造变动 中-新生代 南沙群岛 南海 

分 类 号：P588.1[天文地球—岩石学]