Since the Early Cenozoic, the Philippine Sea Plate (PSP) has undergone a complex tectonic evolution. During this period the Parece Vela Basin (PVB) was formed by seafloor spreading in the back-arc region of the proto-Izu-Bonin-Mariana (IBM) arc. However, until now, studies of the geological, geophysical, and tectonic evolution of the PVB have been rare. In this study, we obtained in situ trace element and major element compositions of minerals in basalts collected from two sites in the southern part of the PVB. The results reveal that the basalts from site CJ09-63 were likely formed via ∼10% partial melting of spinel-garnet lherzolite, while the basalts from site CJ09-64 were likely formed via 15%–25% partial melting of garnet lherzolite. The order of mineral crystallization for the basalts from site CJ09-64 was olivine, spinel, clinopyroxene, and plagioclase, while the plagioclase in the basalts from site CJ09-63 crystallized earlier than the clinopyroxene. Using a plagioclase-liquid hygrometer and an olivine-liquid oxybarometer, we determined that the basalts in this study have high H₂O contents and oxygen fugacities, suggesting that the magma source of the Parece Vela basalts was affected by subduction components, which is consistent with the trace element composition of whole rock.

中文翻译：

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Parece Vela 盆地玄武岩矿物中记录的源岩性和岩浆过程

自早新生代以来，菲律宾海板块（PSP）经历了复杂的构造演化。在此期间，Parece Vela 盆地 (PVB) 是由原始伊豆-博宁-马里亚纳 (IBM) 弧的弧后区域的海底扩张形成的。然而，到目前为止，对 PVB 的地质、地球物理和构造演化的研究还很少。在这项研究中，我们获得了从 PVB 南部两个地点采集的玄武岩中矿物质的原位微量元素和常量元素组成。结果表明，CJ09-63 站位的玄武岩可能由约 10% 的尖晶石-石榴石二辉橄榄石部分熔融形成，而 CJ09-64 站位的玄武岩可能由 15%–25% 的石榴石二辉橄榄石部分熔融形成。CJ09-64站位玄武岩矿物结晶顺序为橄榄石、尖晶石、单斜辉石、和斜长石，而来自站点 CJ09-63 的玄武岩中的斜长石比单斜辉石更早结晶。使用斜长石液体湿度计和橄榄石液体氧气压计，我们确定本研究中的玄武岩具有高 H₂ O含量和氧逸度，表明Parece Vela玄武岩的岩浆源受俯冲成分影响，与全岩微量元素组成一致。