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Petrogenesis of mafic-ultramafic and associated rocks along Sa Kaeo and Pattani Sutures, Thailand

Thitiphan Assawincharoenkij^a,*, Chakkaphan Sutthirat^a, Piyaphong Chenrai^a, Suwapak Imsamut^b, Punya Charusiri^b

 
ABSTRACT:     Mafic-ultramafic rocks and other types of rocks were collected from Sa Kaeo and Pattani sutures. Both sutures are suspected to be a connection between the Nan suture in Northern Thailand and the Bentong-Raub suture that runs across the southern border of Thailand to Malaysia. Rocks were collected from four locations along Sa Kaeo suture: Khao Priwan (Location 1), Wang Somboon (Location 2), Khao Pun-Soi Dao (Location 3), and Pong Nam Ron (Location 4) and one location from Sai Buri River along Pattani suture (Location 5). Both Sa Kaeo and Pattani sutures mainly consist of serpentinite, gabbro, diabase, basalt, pillow basalt, limestone interbedded with sandstone, and shale. Geochemically, the basalts (found in Locations 2, 3) are believed to erupt from the back-arc basin, which is related to within-plate alkali composition; the serpentinite (found in Location 1) is believed to be originated similarly through the process of mafic magma; whereas the pillow basalt taken from Pattani suture (Location 5) is tholeiitic MORB derived from the mantle. All the collected rocks from Sa Kaeo suture appear to be originated from a back-arc basin that had undergone ancient subduction during the Permian-Triassic period. While rock suits in Pattani suture show a similar serpentinized peridotite accumulation process, the found pillow basalts also suggest a possible close relationship to MORB and the ocean floor.

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* Corresponding author, E-mail: thitiphan.a@chula.ac.th

Received 10 Dec 2020, Accepted 12 Jun 2021