海南岛周邻新生代沉积盆地构造与差异性演化特征

Tectonics and discrepant evolution of Cenozoic sedimentary basins adjacent Hainan Island

海南岛周邻发育有4个重要的新生代沉积盆地,即莺歌海盆地、北部湾盆地、琼东南盆地和珠江口盆地珠三凹陷。根据最新的地球物理数据,重新厘定这些盆地的构造与沉积演化及其与海南岛陆上构造的关联。这些盆地发育NE和NW向断裂构造,但存在极大差异性。前者受红河哀牢山断裂构造影响,表现为张扭性的拉分盆地。而后三个盆地则总体表现为裂陷盆地,夹于江绍-博白断裂与丽水-南澳断裂南段之间。伸展始于古新世,具有四次裂陷作用,并发育NW向走滑伸展断层。晚期岩浆对沉积盆地具有一定改造作用,表现岩浆喷发、热流值高。我们厘定了这些NE向断裂在海南岛延伸,滨海断裂可能延至海南岛东南缘,并表现出明显的地震活动性,推断海南岛新生代构造演化与南海北部陆缘演化具有一致性。

The four Cenozoic sedimentary basins adjacent to Hainan Island have undergone significant development.These basins include Yingehai basin,Beibuwan basin,Qiongdongnan basin,and ZhuⅢsag of the Zhujiangkou basin.Based on the latest geophysical data,we have redefined the structure and evolution of the Mesozoic-Cenozoic basins,as well as their relation to Hainan's onshore geological structures.The basins have well-developed NE and NW structures,but significant differences exist between them.The former NW-trending Yinggehai basin,influenced by the Red River fault,is characterized by tension and compressive torsion,resembling a pull-apart basin.On the other hand,the NE basins,located in the southern part of the continental margin of South China,are sandwiched between the Jiangshao-Bobai Faults and the southern Lishui-Nanao faults.The evolution of the Baisha basin is consistent with the Mesozoic basin in the continental margin of South China.The extensionalprocesses began in the Late Cretaceous,resulting in four instances of rifting.Subsequent magma activity led to the reconstruction of the sedimentary basin,exhibiting magma eruptions and high heat flow values.This tectonic distribution is extremely incompatible with the surrounding basins.Theoffshore fracture could extend to the southernmost region,showing obvious seismic activity.We infer that the tectonics of Hainan Island exhibit consistency with the northern South China Sea margin.