Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

S (Solid Earth Sciences ) » S-MP Mineralogy & Petrology

[S-MP31] Supercontinents and Crustal Evolution

Tue. May 28, 2019 10:45 AM - 12:15 PM A08 (TOKYO BAY MAKUHARI HALL)

convener:Madhusoodhan Satish-Kumar(Department of Geology, Faculty of Science, Niigata University), Tomokazu Hokada(National Institute of Polar Research), Krishnan Sajeev(Centre for Earth Sciences, Indian Institute of Science), Yasuhito Osanai(Division of Evolution of Earth Environments, Faculty of Social and Cultural Studies, Kyushu University), Chairperson:M. Satish-Kumar(Niigata University), Tomokazu Hokada(National Institute of Polar Research)

11:45 AM - 12:00 PM

[SMP31-05] Geochemical characteristics of mafic and felsic igneous rocks (1.9-1.75 Ga) in the Lesser Himalaya: Regional variation and its implications for tectonic setting

*Ryuichi Shinjo1, Tomoki Amuro1, Kohei Oura1, Kazuya Oshiro1, Shiro Tahara1, Harutaka Sakai2 (1.Department of Physics and Earth Sciences, University of the Ryukyus, 2.Faculty of Science, Kyoto University)

Keywords:Nepal, Lesser Himalaya, tectonic setting

We present geochemical characteristics of mafic and felsic intrusive rocks (1.9-1.75 Ga) in the Lesser Himalaya and discuss about its tectonic setting. Rocks are taken from wide range of the Lesser Himalaya.

Models of tectonic setting for these rocks are controversial, which include subduction-zone setting (Kohn et al., 2010) and continental rift setting (Sakai et al., 2013).

Analyses of immobile trace element compositions suggest that mafic rocks (metagabbro) from the eastern Nepal have within-plate (or OIB) type composition, while the rocks from central and western Nepal have chemical compositions similar to subduction-related (active continental margin) basalt. It is noted that both types occur in the western Nepal. Based on these results, we suggest that plume-related rift system is more likely tectonic setting for these mafic magmatism than arc setting. Arc-like signature in western Nepal rocks may be derived from sub-continental lithospheric mantle.

Similar regional variation in trace element compositions for felsic rocks was observed. Initial 143Nd/144Nd and 176Hf/177Hf of felsic rocks are lower than those of mafic rocks; thus crustal component might involved significantly in generation of felsic magmas.