Integrated analyses of in situ zircon U-Pb ages and geochemistry were conducted on both granitic and metasedimentary borehole samples from immediately below the Cenozoic sedimentary cover of the northern South China Sea basin. Our work suggests that basement rocks of the South China Sea basin are not Proterozoic or Paleozoic rocks, as previously speculated based on gravity-magnetic inversion work. The analyzed metavolcaniclastic and metasedimentary rocks were likely deposited at or soon after ca. 145 Ma but prior to ca. 85 Ma. A nearby source in coastal South China is proposed based on the generally immature nature of the metasedimentary rocks and the lack of detritus from older basement rocks farther inland. The vast majority of the metavolcaniclastic samples have sparse ca. 250–190 Ma (particularly 200–190 Ma) zircons. This magmatic quiescence is consistent with the existence of a coastal magmatic gap to the east of Hainan Island during this time, previously interpreted as reflecting a period of flat-slab subduction. Metaclastic samples mostly exhibit a dominant ca. 180–120 Ma zircon population, indicating extensive magmatism along the coastal areas. This finding, together with previously reported ca. 190–180 Ma I-type coastal granites and our newly dated ca. 115–98 Ma volcanic and granitic rocks under the western part of the South China Sea basin can best be interpreted by the former presence of an Andean-type continental arc during the Middle Jurassic – Early Cretaceous. Magmatism along this arc ceased soon after 90 Ma or before ca. 85 Ma, with its last pulse represented by a small group of ca. 100–85 Ma granitic intrusions in the eastern part of the northern South China Sea basin. The arc appears to have jumped toward the Western Pacific Ocean at or soon after 90 Ma, starting the development of the Western Pacific-type plate margin.

对南海北部新生代沉积盖层正下方的花岗岩和变沉积钻孔样品进行了原位锆石 U-Pb 年龄和地球化学的综合分析。我们的工作表明，南海盆地的基底岩石不是元古界或古生界岩石，正如先前基于重磁反演工作推测的那样。分析的变质火山碎屑和变质沉积岩很可能在大约 10 年或之后不久沉积。145 Ma，但在大约之前。85 马。由于变沉积岩的性质普遍不成熟，而且缺乏来自更远内陆的较旧基底岩石的碎屑，因此提出了华南沿海附近的一个源。绝大多数变质火山碎屑样品具有稀疏的约。250–190 Ma（尤其是 200–190 Ma）锆石。此次岩浆静止与海南岛东部沿海岩浆裂隙的存在相一致，此前被解释为板块俯冲时期。金属碎屑样品大多表现出显着的 ca。180-120 Ma 锆石种群，表明沿海地区存在广泛的岩浆作用。这一发现，连同先前报道的约。190-180 Ma I 型沿海花岗岩和我们新约会的约。南海盆地西部的 115-98 Ma 火山岩和花岗岩可以通过中侏罗世-早白垩世安第斯型大陆弧的存在来最好地解释。沿着这条弧的岩浆活动在 90 Ma 之后或大约之前不久停止了。85 Ma，它的最后一个脉冲由一小群大约代表。南海北部盆地东部 100～85 Ma 花岗岩侵入体. 该弧似乎在 90 Ma 或之后不久跃向西太平洋，开始了西太平洋型板块边缘的发育。