海洋地质与第四纪地质2026，Vol.46Issue(3)：79-94,16.DOI:10.16562/j.cnki.0256-1492.2025092401
南海与典型弧后盆地基底岩石的地球化学对比
A geochemical comparison of basement rocks between the South China Sea and typical back-arc basins:Basin expansion in the context of big mantle wedge
摘要
Abstract
The South China Sea(SCS)is one of the largest marginal seas in the western Pacific.Its formation and evolution are of great significance to plate tectonic studies,particularly for understanding the formation and evolution of the western Pacific subduction zone.However,the dynamic background and mechanisms behind the formation of the SCS remain unclear.The oceanic crust basement rocks recorded critical information of the formation mechanism of the SCS.Resolving the diversity in petrogenesis and geochemistry of these oceanic crust basement rocks offers important clues to uncover the formation and evolution of the SCS.We conducted a geochemical comparison of oceanic crust basalts from the SCS with those from typical back-arc basins(such as the Mariana Trough and the Japan Sea)and mid-ocean ridge basalts(MORB)from open oceans.Compared to MORB from open oceans,the oceanic crust basalts of the SCS exhibit higher Al2O3 and K2O contents,lower FeOT and TiO2 contents,and similar trace elemental patterns.In contrast to typical back-arc basin basalts,the SCS basalts have higher MgO and CaO contents but different trace element patterns,indicating the unique geochemical characteristics of the SCS basalts.By excluding the effects of magmatic processes such as fractional crystallization,crustal contamination,and partial melting on the geochemical variations of the oceanic basalts,we further believe that the lithological and geochemical heterogeneity of the mantle source are the primary factors controlling the geochemical diversity of the SCS oceanic crust basalts,which distinguish them significantly from the source regions of typical back-arc basin basalts that are controlled by the evolution of small mantle wedge.In addition,by comparing the elemental and isotopic geochemical compositions of the SCS oceanic crust basalts with those of the Cenozoic intraplate basalts in SE China that formed under the influence of the big mantle wedge,we further revealed that the enriched mantle components within the mantle source of the SCS oceanic crust basalts exhibits similarities to those of the SE China basalts.Therefore,unlike typical back-arc basins that formed through geological processes involving a small mantle wedge,the formation and evolution of the SCS were primarily influenced by material circulation in the context of the big mantle wedge.The deep dynamic processes and formation of the SCS basin should be closely related to the evolution of a big mantle wedge.关键词
地球化学/边缘海盆地/地幔不均一性/玄武岩/南海Key words
geochemistry/marginal sea basin/mantle heterogeneity/basalt/South China Sea分类
海洋科学引用本文复制引用
蒋昊,俞恂..南海与典型弧后盆地基底岩石的地球化学对比[J].海洋地质与第四纪地质,2026,46(3):79-94,16.基金项目
国家自然科学基金"南海扩张初期洋壳增生的岩石地球化学研究(IODP-U1500站)"(41906051) （IODP-U1500站）
