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A bigger tent for the Southeast Asian volcanic province

Kwan-Nang Pang 1, Tai Truong Nguyen1,3, Liekun Yang2, Fei Wang2, Ngo Xuan Thanh3, Hao-Yang Lee1

  • Affiliations: 1Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan; 2State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 3Department of Geology, Hanoi University of Mining and Geology, Hanoi, Vietnam 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 16

  • Programme No: 3.7.23

  • Theme 3 > Session 7

Abstract

The Southeast Asian volcanic province refers mainly to massive outpourings of basaltic magmas in southern Indochina and the Hainan Island over the Late Cenozoic, yet many small-scale volcanic fields scattering over Thailand and Vietnam might be related to the same magmatic system but remain poorly known and studied. In this work, we revisited the Dien Bien Phu volcanic field, and investigated another two volcanic fields, one at Thanh Hoa and the other at Lao Cai close to the Vietnam-China border, where no published data have yet been available. Representative 40Ar/39Ar dates of fresh, hand-picked matrix of volcanic rocks indicate eruption ages of ~510 ka (Thanh Hoa), ~5.6 Ma (Dien Bien Phu), and 418--442 ka (Lao Cai). The rocks display fractionated rare-earth element patterns without negative Nb-Ta-Ti anomaly, generally similar to OIB-like magmas. They have Sr-Nd isotopic compositions overlapping with the high-87Sr/86Sr, low-143Nd/144Nd end of the array shown by basaltic rocks elsewhere in the Southeast Asian volcanic province. The new data confirm an earlier view that volcanism did not follow any systematic spatial-temporal patterns, and extend the known extent of the Southeast Asian volcanic province to ~22.7 ºN near the Vietnam-China border. Lastly, we address two competing models of magma genesis: localized lithospheric extension and passive upwelling of asthenosphere-derived melts, and active migration of plume-derived melts from the Hainan Island along trans-lithospheric structures such as the Red River Fault and related NW-SE-trending strike-slip faults.