Petrography,mineralogy and geochemistry of Cretaceous sediment samples from western Khorat Plateau,Thailand, and considerations on their provenance |
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| Institution: | 1. A.P. Karpinsky Russian Geological Research Institute, V.O., Srednii pr. 74, St. Petersburg, 199106, Russia;2. A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, 630090, Russia;3. Novosibirsk State University, Novosibirsk, ul. Pirogova 2, 630090, Russia;1. School of Earth Sciences and Engineering, Sun Yat–sen University, Guangzhou 510275, China;2. Guangdong Key Lab of Geodynamics and Geohazards, Guangzhou 510275, China;3. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;4. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;5. Department of Applied Geology, Curtin University, Perth 6102, Australia |
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| Abstract: | At Mo Hin Khao on the western flank of Khorat Plateau, Thailand, the Phra Wihan Formation reveals litharenite and sublitharenite with some subarkose and arkose. A cuesta in the eroded sedimentary sequence exhibits spectacular rock pillars of considerable geotourist potential. The rock sequence is high in silica (SiO2 67–98 wt%) and contains quartz, mica, magnetite, chert fragments and accessory minerals such as zircon and tourmaline and amphibole species. These accessory minerals suggest felsic rocks, such as granite, granodiorite and pegmatite, were sources for the sandstones. Geochemical analyses of the sedimentary sequence suggest that source rocks may lie in the passive continental margin, before sediment transport and deposition in the Khorat Basin by rivers flowing across a large flood plain. Many depositional sequences/episodes formed thick beds of cross bedded clastic rocks. A high average maturity index (>5) indicates sedimentary reworking/recycling. Chemical Index of Alteration (CIA) values range from 47 to 98, suggesting variable chemical weathering within the source area rocks, largely representing moderate to high degrees of weathering. The average CIA value of these sediments (78) suggests that relatively extreme alteration factors were involved. |
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| Keywords: | Mineralogy Geochemistry Provenance Khorat Group Phra Wihan Formation Chemical Index of Alteration Mo Hin Khao |
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