The Philippine Mobile Belt is a complex plate boundary with multiple terranes in Southeast Asia, yet its early tectonic evolution is still not fully understood due to a scarcity of solid evidence. Here we report new whole rock geochemical, Sr-Nd isotopic, and zircon U-Pb-Hf isotopic data for Cretaceous-Miocene arc magmatic rocks from the Cebu and Bohol Islands, Philippine Mobile Belt. Bulk geochemical data display arc affinities with enriched large ion lithophile elements (e.g., Sr and Ba) and depleted high field strength elements (e.g., Nb, Ta, and Ti). The high positive εNd(t) (+4.6 to +9.1) values and low initial 87Sr/86Sr ratios (0.7032–0.7048) suggest that these igneous rocks were generated by partial melting of mantle wedge in an arc setting. U-Pb dating of zircons revealed Cretaceous (ca. 120–90 Ma), middle Eocene to early Oligocene (ca. 43–30 Ma), and middle Miocene (ca. 14 Ma) crystallization ages for the arc magmatism with abundant Permian-Triassic zircon xenocrysts clustering at ca. 250 Ma. The Permian-Triassic grains show dominantly negative εHf(t) values ranging from −16.2 to −6.6, which are similar to those of coeval rocks in Eastern Indochina. Combined with previous paleomagnetic studies, we propose that an Eastern Indochina-derived continental fragment was involved during the formation of arcs in the Cebu and Bohol Islands, which highlights the potential contribution of ancient continental materials in the formation of intra-oceanic arcs. This scenario does not support the previously proposed model that the Cretaceous arc in the Philippine Mobile Belt formed in the northern margin of the proto-Philippine Sea Plate and Australian margin.

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东印度支那碎片对菲律宾移动带岛弧系统形成的贡献

菲律宾移动带是东南亚多地体的复杂板块边界，但由于缺乏确凿证据，其早期构造演化仍不完全清楚。在这里，我们报告了菲律宾移动带宿务岛和薄荷岛的白垩纪-中新世弧岩浆岩的新全岩地球化学、Sr-Nd 同位素和锆石 U-Pb-Hf 同位素数据。大量地球化学数据显示了富集大离子亲石元素（例如 Sr 和 Ba）和耗尽的高场强元素（例如 Nb、Ta 和 Ti）的电弧亲和性。较高的正 εNd(t)（+4.6 至 +9.1）值和较低的初始 87Sr/86Sr 比值（0.7032-0.7048）表明这些火成岩是由地幔楔在弧形环境中部分熔融形成的。锆石的 U-Pb 定年揭示了白垩纪（约 120-90 Ma）、始新世中期至渐新世早期（约 43-30 Ma）和中中新世（约 14 Ma）的弧岩浆作用结晶年龄，在约 250 毫安。二叠纪-三叠纪颗粒显示出显着的负 εHf(t) 值，范围从 -16.2 到 -6.6，与东印度支那的同期岩石相似。结合之前的古地磁研究，我们提出宿务岛和薄荷岛弧形成过程中涉及到东印度支那大陆碎片，这突出了古代大陆物质对洋内弧形成的潜在贡献。该情景不支持先前提出的菲律宾移动带中的白垩纪弧形成于原菲律宾海板块北缘和澳大利亚边缘的模型。14 Ma) 弧岩浆作用的结晶年龄，在大约 250 毫安。二叠纪-三叠纪颗粒显示出显着的负 εHf(t) 值，范围从 -16.2 到 -6.6，与东印度支那的同期岩石相似。结合之前的古地磁研究，我们提出宿务岛和薄荷岛弧形成过程中涉及到东印度支那大陆碎片，这突出了古代大陆物质对洋内弧形成的潜在贡献。该情景不支持先前提出的菲律宾移动带中的白垩纪弧形成于原菲律宾海板块北缘和澳大利亚边缘的模型。14 Ma) 弧岩浆作用的结晶年龄，在大约 250 毫安。二叠纪-三叠纪颗粒显示出显着的负 εHf(t) 值，范围从 -16.2 到 -6.6，与东印度支那的同期岩石相似。结合之前的古地磁研究，我们提出宿务岛和薄荷岛弧形成过程中涉及到东印度支那大陆碎片，这突出了古代大陆物质对洋内弧形成的潜在贡献。该情景不支持先前提出的菲律宾移动带中的白垩纪弧形成于原菲律宾海板块北缘和澳大利亚边缘的模型。