Abstract
<p>Airborne geophysical data were used to analyze the complex structures of eastern Thailand. For visual interpretation, the magnetic data were enhanced by the analytical signal, and we used reduction to the pole (RTP) and vertical derivative (VD) grid methods, while the radiometric data were enhanced by false-colored composites and rectification. The main regional structure of this area trends roughly in northwest-southeast direction, with sinistral faulting movements. These are the result of compression tectonics (sigma<span style="font-size: 8px;">_1</span> in an east-west direction) that generated strike-slip movement during the pre Indian-Asian collision. These faults are cross-cut by the northeast-southwest-running sinistral fault and the northwest-southeast dextral fault, which occurred following the Indian-Asian collision, from the transpession sinistral shear in the northwest-southeast direction. Three distinct geophysical domains are discernible; the Northern, Central and Southern Domains. These three domains correspond very well with the established geotectonic units, as the Northern Domain with the Indochina block, the Central Domain with the Nakhonthai block, the Upper Southern Sub-domain with the Lampang-Chaing Rai block, and the Lower Southern Sub-domain with the Shan Thai block. The Indochina block is a single unit with moderate radiometric intensities and a high magnetic signature. The direction of the east-west lineament pattern is underlain by Mesozoic non-marine sedimentary rock, with mafic igneous bodies beneath this. The Nakhonthai block has a strong magnetic signature and a very weak radiometric intensity, with Late Paleozoic-Early Mesozoic volcanic rock and mélange zones that are largely covered by Cenozoic sediments. The boundaries of this block are the southern extension of the Mae Ping Faults and are oriented in the northwest-southeast direction. The Lampang-Chaing Rai and Shan Thai blocks, with very weak to moderate magnetic signatures and moderate to very strong radiometric intensities are dominated by marine clastic and igneous rocks or a northwest-southeast trending deformation zone of inferred Precambrian complexes, respectively. It is suggested that these tectonic plates collided against one another in a west-east direction.</p>
Highlights
It is widely accepted that the eastern Thailand region has complex geology and structures [Hada 1990]
An Early Mesozoic accretionary complex developed in the Sra KaeoChanthaburi area [Hada et al 1997, Chutakositkanon et al 2003] and it has been interpreted as having formed as a result of the accretion of oceanic and terrigenous materials that were mixed along the western margin of the Indochina block during Late Paleozoic to Early Mesozoic times [e.g., Metcalfe 1999, Charusiri et al 2002]
Lineaments related to tectonic features Comparisons between the airborne geophysical lineaments and the tectonic features proposed by Charusiri et al [2002] and with the subsequent studies by Chutakositkanon et al [2003] and Ridd [2012], have revealed that the major lineaments of the Northern and Central Domains correspond well with the MPF zone (MPFZ), while the Southern Domain is bound to the east by a fault that conforms well with TPF, which is believed to extend from western Thailand to the east (Figure 1B)
Summary
It is widely accepted that the eastern Thailand region has complex geology and structures [Hada 1990] This region is characterized by the Sra Kaeo Suture Zone [Bunopas and Vella 1978], which was earlier interpreted as the site of a significant collision zone between the Shan-Thai (or Sibumasu) and Indochina blocks [Bunopas and Vella 1978, Hada et al 1997, Metcalfe 1999] (Figure 1A). Several minerals that have been deposited along these sutures can result in magmatism between the plate boundaries, such as gold, gem, chromite, magnesite, stibnite and fluorite ores [e.g., Suwanasing 1969, Hinthong 1995] These sutures are not clearly defined, for their locations. The northwest-tosoutheast trending Mae Ping Fault (MPF) extends from
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