南海大洋钻探及海洋地质与地球物理前沿研究新突破

南海是西太平洋地区规模最大且具有代表性的边缘海盆地之一。经过近几十年的研究积累,尤其是通过实施5个国际大洋钻探航次(1999–2018年)与国家自然科学基金委“南海深海过程演变”重大研究计划(2011–2019年),我国科学家获得了大量宝贵的第一手资料,取得了一系列创新进展与重大突破,标志着南海海洋地质与地球物理研究正走向国际前沿。重要研究成果包括:(1)新提出南海是“板缘张裂”盆地,与经典的大西洋型陆缘模式不同;(2)大洋钻探首次获取了基底玄武岩样品,结合中国在南海首次深拖地磁测量实验,精确测定了南海海盆玄武岩年龄,揭示南海海盆从东向西分段扩张;(3)大洋钻探结果发现南海陆缘岩石圈减薄之初岩浆迅速出现,未发现缓慢破裂造成的蛇纹岩出露;(4)发现南海扩张结束后仍存在大量岩浆活动,可能受控于多种构造与地幔因素;(5)地球化学证据与地球动力学模拟都显示南海岩浆的形成受到周边俯冲带的影响。目前我国的海洋地球科学正在进入崭新的发展阶段,有望以南海为基点,开始拓展到周边大洋,通过主导大型研究计划以及建设我国大洋钻探平台,以提升我国在南海、西太平洋与印度洋海洋地质科学研究的实质性影响力与引领地位。

Ocean drilling and major advances in marine geological and geophysical research of the South China Sea

The South China Sea (SCS) is the largest marginal sea in the Western Pacific Ocean. Major advances in understanding SCS tectonic processes have been made in the last several decades, especially through the implementation of five international ocean drilling expeditions during 1999-2018 and the "South China Sea Deep" major research program of the National Natural Science Foundation of China (2011-2019). Critical data have been acquired and important scientific results have been obtained, which have changed our view of how the SCS marginal sea basin developed and evolved. Major progresses have been made in multiple aspects:(1) the SCS is proposed as a new type of "plate-edge rifting" model, which differs from the classic Atlantic-type "intra-plate rifting" model; (2) Ocean drilling obtained the SCS basement basalt samples for the first time, which together with the first deep-towed magnetic survey, enabled the determination of SCS basin ages and revealing that the SCS seafloor spreading propagated stepwise from east to west; (3) Magmatism appeared rapidly during thinning of lithosphere in the SCS northern margin, in sharp contrast to serpentinite exposure by relatively slow rifting of the Atlantic Ocean; (4) Magmatic activity is still significant after the cessation of SCS seafloor spreading, being controlled by multiple tectonic and mantle processes; (5) Geochemical evidence and geodynamic simulations show that the SCS magmatism is affected by the surrounding subduction zones. At present, marine geoscience research of the SCS is being extended to studies of its interaction with surrounding ocean basins. Through conducting large-scale research programs, building ocean drilling platform, and strengthening international collaboration, China''s contributions to marine geoscience research are expected to increase.