弧后盆地玄武岩(BABB)数据挖掘:与MORB及IAB的对比

弧后盆地玄武岩(BABB)全球分布有限,与板块俯冲有关,位于岛弧外侧,规模小,寿命短,现代BABB主要分布于西太平洋。通常认为,BABB地球化学成分变化较大,包括正常洋中脊玄武岩(N-MORB)、富集洋中脊玄武岩(E-MORB)、岛弧玄武岩(IAB)及少量洋岛玄武岩(OIB)组分。在玄武岩构造判别图中,BABB大多在洋中脊玄武岩(MORB)范围内,说明BABB类似MORB。新的全球MORB数据研究表明,MORB包含了从MORB到OIB及IAB的组分,而BABB相对于MORB更富集Cs,Rb,U,Ba,Th和Pb等不相容元素,有明显的Nb-Ta负异常,表明BABB兼具MORB和IAB的地球化学特征,是俯冲流体及沉积物参与其岩浆作用过程所致,大多是在湿的条件下部分熔融形成的。弧后盆地可分为初始弧后盆地和成熟弧后盆地,前者玄武岩具有明显的岛弧玄武岩的地球化学特征,而后者玄武岩更接近MORB的特征。

Back-Arc Basin Basalt(BABB) Data Mining: Comparison with MORB and IAB

Back-Arc Basin Basalts(BABB) distribute narrowly in the world. Currently, BABB are mainly distribute in the western Pacific Ocean outside the island arc in small scales and short lifespan which are related with subduction. It is generally considered that geochemical compositions of BABB vary in a large scale, including N-MORB, E-MORB, IAB, and a small amount of OIB. In most of basalt discrimination diagrams, BABB mainly fall into MORB area, suggested that BABB are similar to MORB. New data of MORB shows that MORB contain a series of constituents from MORB to OIB, also IAB, while BABB are mainly composed by MORB and IAB, rarely show OIB components. BABB is generally analogous with MORB whereas the former is enriched in Cs, Rb, U, Ba, Th, Pb, and other incompatible elements, exhibits an obvious Nb-Ta negative abnormal, suggesting that BABB is featured with both geochemical characteristics of MORB and IAB, with subuduction sediments partition during its magmatism process. It is mainly formed by partial melting in wet environment. Back-arc basins are divided into two groups: mature ones and immature ones. Primary back-arc basins share some geochemical characteristics of island arcs while mature back-arc basins exhibit few IAB features and is closer to MORB.