Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-RD Resources, Mineral Deposit & Resource Exploration

[S-RD41] Developments in resource geology: Origin and evolution of ore fluids

Mon. May 25, 2015 11:00 AM - 11:45 AM 106 (1F)

Convener:*Kenzo Sanematsu(Mineral Resource Research Group, Institute for Geo-Resources and Environment, National Institute of Advanced Industrial Science and Technology), Tatsuo Nozaki(Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Ryohei Takahashi(Faculty of International Resource Sciences, Akita University), Chair:Ryohei Takahashi(Faculty of International Resource Sciences, Akita University), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University)

11:15 AM - 11:30 AM

[SRD41-08] Petrogenesis of granitoids in northern Palawan (Philippines) and its implications on rare-earth element mineralization

*Jenielyn PADRONES1, Akira IMAI2, Ryohei TAKAHASHI2, Jillian aira GABO3, Kenichiro TANI4 (1.Graduate School of Engineering and Resource Sciences, Akita University, Japan, 2.Faculty of International Resource Sciences, Akita University, Japan, 3.Department of Earth Resources Engineering, Kyushu University, Japan, 4.Department of Geology and Paleontology, National Museum of Nature and Science, Japan)

Keywords:Palawan Continental Block, Kapoas granitoids, rare earth element mineralization, monazite, allanite

Global attention brought about by the increasing demand of rare earth elements (REE) has paved the way for various exploration efforts worldwide. Areas with promising REE deposits were revisited. In the Philippines, explorations are now on-going with studies focused on several granitic intrusions. Some of these granitic bodies are distributed in northern Palawan, which is a rifted fragment of the southeastern Eurasian margin during the opening of the South China Sea basin in the Oligocene.

The granitic bodies were investigated for possible concentration of REE during magmatic differentiation. The Kapoas granitoids include granites and granodiorites that are metaluminous, high-K calc-alkaline, and belong to the I-type and ilmenite-series. The granitoids are mostly biotite-rich and contain xenoliths of schists and diorite, quartz xenocrysts, and mafic enclaves. Two separate intrusive bodies are observed: the Mt. Kapoas which is 13.2 Ma in age; and the Bay Peak granite which is dated 14.1 Ma. However, both intrusives have similar geochemical signature, which show LREE enrichment. These granitic rocks were more evolved or highly differentiated I-type, probably generated in the middle to lower continental crust . The REE-bearing minerals are allanite and monazite. The weathered crust also show LREE enrichment. Weathered crust profile shows Ce-anomaly in the B-horizon portion where kaolinite, muscovite and illite act as absorptive materials.

This study also confirmed the presence of the Cretaceous Daroctan granitoids aside from the well-studied Middle Miocene Kapoas granitoids. The Daroctan granitoids include granodiorites and granites which belong to ilmenite-series. The granodiorites contain xenoliths of metasedimentary rocks, quartz xenocrysts and mafic enclaves. It is also sporadically distributed in the northern part of the island but these different intrusive bodies have almost similar ages. The REE-bearing minerals are monazite. Enrichment of LREE in the weathered crust is relatively higher than that of the Kapoas.

Allanite and monazites in the study areas are enriched in Ce, La, Nd, and Sm with associated radioactive element Th. Heavy minerals concentrated in the beach in Erawan and Ombo, which is part of the Kapoas granitoids, contain up to >10,000 ppm of La, Ce, and Sm.