珠江口盆地中——新生代热隆升格局的磷灰石和锆石裂变径迹反演  

Meso-Cenozoic tectonothermal pattern of the Pearl River Mouth Basin:constraints from zircon and apatite fission track data

作　　者：李庶波[1,2] 王岳军 吴世敏[1,2] 

机构地区：[1]中山大学地球科学与地质工程学院,广东广州510275 [2]广东省地球动力作用与地质灾害重点实验室,广东广州510275

出　　处：《地学前缘》2018年第1期95-107,共13页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目(2014CB440901);国家重点研发计划项目(2016YFC0600303);国家自然科学基金项目(41190073;41372198);中山大学高校基本业务费资助项目

摘　　要：珠江口盆地作为南海北部陆缘典型的裂陷沉积区,是中国最大的中生代海相残留盆地之一,其构造-热演化对南海张开时限及华南构造格局有重要指示作用。在钻孔资料限定和地质格局约束下,文中综合运用磷灰石和锆石裂变径迹对珠江口盆地内钻孔基底花岗质岩石开展了低温热年代学研究,通过径迹年龄分析和径迹长度统计,反演了该区中—新生代基底构造-热演化历史,恢复了珠江口盆地多阶段热运动和基底隆升格局。研究表明,珠江口盆地基底花岗质岩石锆石裂变径迹表观年龄分布于131.7~97.9 Ma,多小于其成岩年龄。样品磷灰石裂变径迹表观年龄多集中在79.7~61.9 Ma,径迹长度变化于11.37~13.16μm,属中等长度,磷灰石裂变径迹多为"冷却"至"混合"类型。珠江口盆地基底热史反演存在明显区域性特点,南(西)部地区抬升记录早,新生代冷却速率相对较低。珠江口盆地基底晚白垩世以来隆升幅度在6km左右,主要发生在晚白垩世、古近纪神狐运动阶段、渐新世珠琼运动Ⅱ幕及南海运动阶段(26 Ma之前)。其中,南海运动表现出东早西晚的特点。基底抬升与盆地形成、红河断裂走滑相耦合。盆地基底的热演化历史为南海的演变历程研究提供了限定条件,是太平洋板块俯冲、印度-欧亚板块碰撞及南海构造运动的综合反映。As a representative of the epicontinental rift basin in the northern South China Sea, the Pearl River Mouth Basin is an ideal study area for a better understanding of the tectonic evolution of the South China Block and time limit of the opening of the South China Sea. This paper presents the apatite and zircon fission track dating results from basins Paleozoic gneissic and Cretaceous granitic drill samples. The zircon fission track apparent age ranges from 131.7 to 97.9 Ma, younger than their formation time; the apatite track apparent age falls between 79.7 and 61.9 Ma; at 11.3713.16 μm, the apatites fission track lengths show a cooling or mixing pattern. The geothermal simulation show that distinctive uplifting and cooling processes were present in different sites, cooling event took place earlier, and the uplifting rate was slower in the south than in the north in the Cenozoic. It is inferred that the basins basement uplifted about 6 km since the late Cretaceous when it experienced several episodes of rapid uplift in the late Cretaceous, the Shenhu tectonic event at Paleocene, the second scene of the Zhuqiong tectonic event, and the Nanhai tectonic event at Oligocene （before 26 Ma）. During the Nanhai tectonic event, the uplift began earlier in the east than in the west. The timing of the rapid uplift is consistent with the timing of slipstrike of the Red River Fault, and the uplift shows good correlation with the basin formation. Our data provide important constraints on the extension of the South China Sea. It is confirmed that the basement uplift of the Pearl River Mouth Basin was a result of a conjuncture of the subduction of the Pacific Plate, collision of the IndianEurasian Plate and extension of the South China Sea.

关 键 词：裂变径迹年龄 中-新生代隆升 构造-热历史 珠江口盆地 盆地基底 

分 类 号：P542[天文地球—构造地质学]