Missing ophiolitic rocks along the Mae Yuam Fault as the Gondwana–Tethys divide in north‐west Thailand

Abstract

Thailand comprises two continental blocks: Sibumasu and Indochina. The clastic rocks of the Triassic Mae Sariang Group are distributed in the Mae Hong Son-Mae Sariang area, north-west Thailand, which corresponds to the central part of Sibumasu. The clastic rocks yield abundant detrital chromian spinels, indicating a source of ultramafic/mafic rocks. The chemistry of the detrital chromian spinels suggests that they were derived from three different rock types: ocean-floor peridotite, chromitite and intraplate basalt, and that ophiolitic rocks were exposed in the area, where there are no outcrops of them at present. Exposition of an ophiolitic complex denotes a suture zone or other tectonic boundary. The discovery of chromian spinels suggests that the Gondwana-Tethys divide is located along the Mae Yuam Fault zone. Both paleontological and tectonic aspects support this conclusion.

Nd isotopic composition of Late Devonian seawater in western Thailand: Geotectonic implications for the origin of the Sibumasu terrane

“…While the origin of Sibumasu as a Gondwana-derived continental crustal block is widely accepted (e.g., Metcalfe, 1991Metcalfe, , 1996Hisada et al, 2004;Golonka et al, 2006;Metcalfe, 2006;Ridd, 2009b), various primary positions along the Northwest Australian margin of Gondwana have been suggested. Early reconstructions placed Sibumasu near the Canning Basin of NW Australia (Bunopas, 1982;Burrett and Stait, 1985).…”

“…It is widely accepted that the two principal microcontinents, Sibumasu in the west and Indochina in the east, had formerly been a part of Gondwana. There is, however, still an ongoing debate on the overall plate tectonic model and the position of the Paleotethys suture (e.g., Ueno and Hisada, 2001;Hisada et al, 2004;Ferrari et al, 2008;Kamata et al, 2009;Metcalfe, 2009). The tectonic framework of Thailand is formed of four units (Fig.…”

“…2). This fault zone is interpreted to represent the boundary between Sibumasu and the Inthanon Zone, and thus the biogeographic Gondwana-Paleotethys divide (e.g., Hisada et al, 2004;Ferrari et al, 2008;Kamata et al, 2009). According to Metcalfe (2006Metcalfe ( , 2009, however, the entire Mae Sariang area belongs to the Inthanon Zone and the Mae Yuam Fault, because of its Tertiary age, cannot be related to the destruction of the Paleotethys.…”

マントル岩起源砕屑物の解析

“…Lockwood Lockwood, 1971a, b, 1972Lockwood 1971a, 1975, 1983Hisada et al, 2004Hisada et al, , , 19421983 Fig. 1e Okuzawa and Hisada 2008Lenaz 2008, 1992 Fig Irvine, 1965Irvine, , 1967Arai, 1992;Arai et al, 2011 Ti Mn Co Zn Ni , Gahlan andArai, 2007;Arai and Ishimaru, 20112 3 Fe Ballhaus et al, 1990Wood et al, 1990 Cr chromian spinels…”

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