Volcanic-hypabyssal rock geochemistry of a subduction-related marginal basin ophiolite: Southeast Bohol Ophiolite-Cansiwang M？ange Complex, Central Philippines

• Published in: Geosciences journal (Seoul, Korea) 2006, 10(3), , pp.291-303
• Main Authors: D.V. Faustino, G.P. Yumul, Jr, C.B. Dimalanta, J.V. de Jesus, M-F. Zhou, J.C. Aitchison, R.A. Tamayo, Jr
• Format: Article
• Language: Korean
• Subjects: 지질학
• ISSN: 1226-4806; 1598-7477

The Early Cretaceous Southeast Bohol Ophiolite-Cansiwang Mlange Complex and the Alicia Schist form thebasement of southeastern Bohol Island in central Philippines.New geochemical data show that four discrete groups consti-tute the volcanic and associated hypabyssal rocks of the ophi-olite-mlange complex: boninitic rocks (BON), enriched andnormal mid-ocean ridge basalt-like rocks (E-MORB; N-MORB) and high-magnesian andesites (HMA). Of these fourgroups, the BON are the most depleted in REEs and with themost pronounced negative Nb anomalies. Both MORB-liketypes exhibit subduction-zone influence as reflected in theirslight negative Nb anomalies. Characteristically with flat andLREE-depleted patterns, the HMA samples apear to mimicN-MORB patterns but with lower REE concentrations. Thisgeochemical diversity is best explained by a suprasubductionzone environment of formation as is also evident from field geo-believed to have ben concurrent with the ophiolite’s emplace-ment by subduction-accretion along a forearc margin. This tec-tonic boundary was later jammed into inactivity with the entryof the Alicia Schist that most likely was an oceanic bathymetrichigh. The intercalation of both tufaceous materials and pelagicchert with the pillow basalts are consistent with a marginalbasin tectonic setting. KCI Citation Count: 12