HR: 0800h
AN: T31B-0470    [Abstracts]
TI: Quaternary volcanic rocks from Central Burma: Geochemical characteristics and petrogenesis
AU: * Yang, H
EM: r95224110@ntu.edu.tw
AF: National Taiwan University, No.1, Sec.4, Roosevelt Road, Taipei, 106, Taiwan
AU: Chung, S
EM: sunlin@ntu.edu.tw
AF: National Taiwan University, No.1, Sec.4, Roosevelt Road, Taipei, 106, Taiwan
AU: Chu, C
EM: julie0104@yam.com
AF: National Taiwan University, No.1, Sec.4, Roosevelt Road, Taipei, 106, Taiwan
AU: Gallet, S
EM: gallet@ntu.edu.tw
AF: National Taiwan University, No.1, Sec.4, Roosevelt Road, Taipei, 106, Taiwan
AU: Mitchell, A
EM: imhle@mptmail.net.mm
AF: Ivanhoe Myanmar Holdings, Ltd., 321-323, U Wisara Road, Sanchaung Township, Yangon, 095, Myanmar
AB: Burma is located in the eastern margin of the India-Asia collision zone. The most significant geologic feature in the region is arguably the Sagaing Fault representing a dextral strike-slip fault system that links the eastern Himalayan Syntaxis in the north and the Andaman Sea in the south. This region is situated in a unique or ¡§transitional¡¨ position between contractional (Himalayan) and extensional (Andaman Sea) tectonic settings, and furthermore characterized by the eruption of a series of Middle Miocene to Quaternary volcanoes along the Sagaing Fault. Here we report geochemical and Sr-Nd isotopic analyses of Quaternary basalts and basaltic andesites recovered from Mt. Popa and Monywa areas, Central Burma. Major element data of the Burmese rocks show a potash-rich nature, with most of the Mt. Popa samples (8 out of 12 analyses) plotting in the high-K calc-alkaline suite and the Monywa samples (5 out of 7 analyses) in the shoshonitic suite. The latter may be further specified as absarokite based on their mineral constituents and trace element characteristics. All these rocks display significant depletions in the high field strength elements (HFSE; e.g., Nb, Ta and Ti), enrichments in the large ion lithophile elements (LILE; e.g., Cs, Rb, Ba, Th, U) and light rare earth elements. Thus, the overall incompatible trace element distribution patterns are similar to those of arc magmas formed in the subduction zone. Moreover, the Burmese rocks show high Nd and low Sr isotopic ratios, with εNd = +1 to +4 and ⁸⁷Sr/⁸⁶Sr~ 0.7045. Consequently, we propose that the magma source of the high-K calc-alkaline rocks from Mt. Popa is a juvenile mantle wedge in the region despite the Indian Ocean slab beneath this part of the Asian continent has already ceased its subduction. Under this framework, the Monywa absarokites represent small-degree melting products of a phlogopite-bearing peridotite source in the mantle wedge.
DE: 3618 Magma chamber processes (1036)
DE: 3619 Magma genesis and partial melting (1037)
DE: 8108 Continental tectonics: compressional
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8185 Volcanic arcs
SC: Tectonophysics [T]
MN: 2007 Fall Meeting