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Permian radiolarian cherts and their geochemical characteristics in the Central Plain of Thailand: Implications for the geological affiliation and origin of the Permian chert. |
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| รหัสดีโอไอ | |
| Creator | Waraphorn Phromsuwan |
| Title | Permian radiolarian cherts and their geochemical characteristics in the Central Plain of Thailand: Implications for the geological affiliation and origin of the Permian chert. |
| Contributor | Yoshihito Kamata, Thasinee Charoentitirat, Katsumi Ueno, Apsorn Sardsud |
| Publisher | Department of Mineral Resources of Thailand |
| Publication Year | 2568 |
| Journal Title | Thai Geoscience Journal |
| Journal Vol. | 6 |
| Journal No. | 10 |
| Page no. | 26-50 |
| Keyword | Back-arc basin, Central Thailand, Geochemistry, Permian, Radiolarian chert |
| URL Website | https://ph03.tci-thaijo.org/index.php/TGJ |
| Website title | THAI GEOSCIENCE JOURNAL |
| ISSN | 2730-2695 (Print)3056-9370 (Online) |
| Abstract | Improved geological constraints refine our understanding of Southeast Asia's and Thailand's geotectonic evolution. This study investigates Permian chert successions in the Central Thailand, where are the Sawan Khalok and the Nakhon Sawan–Uthai Thani areas,to elucidate their genesis, depositional environment, and implications for the tectonic evolution. The Sukhothai Zone exhibits island arc signatures, including Permian-Triassic volcanic rocks, formed by the subduction of the Paleo-Tethys Ocean with the Indochina Block. Permian cherts, previously considered enigmatic, are irregularly distributed in this zone. The research examines four chert sections, identifying the Early Permian radiolarians (Asselian) in TS13, specifically Pseudoalbaillella simplex and Pseudo-albaillella cf. annulata, and late Early –early Middle Permian (Kungurian–Roadian) in TS14, comprising Albaillella sinuata and Albaillella cf. asymmetrica. The Middle Permian radiolarians (Roadian–Capitanian) identified include Pseudoalbaillella scalprata, Parafollicucullus fusiformis, Parafollicucullinoides cf. globosus, Parafollicucullus monacanthus, Follicucullus cf. scholasticus, and Follicucullus cf. bipartitus form NS07. For NS11, the identified radiolarians are Pseudoalbaillella cf. lomentaria, Pseudoalbaillella scalprata,Parafollicucullus monacanthus, and Follicucullus cf. scholasticus indicating Wordian–Capitanianages. Geochemical analyses (ICP-OES and ICP-MS) of chert samples from the four sections provide insights into their origin and depositional setting. Samples of TS13 and TS14 exhibit origins of hydrothermal influence and show a negative Ce anomaly, suggesting depositing nearby a spreading ridge environment with limited hydrothermal activity. Samples of NS07 and NS11 plot close to biogenic chert origin and display a depleted Ce anomaly, indicating decreased hydrothermal material input or deposition near a continental margin. Based on lithological characteristics and radiolarian ages, chert successions in the Sawan Khalok and the Nakhon Sawan–Uthai Thani areas are considered to have same origins of the Khanu Chert and the Khao Gob Chert. In terms of depositional time intervals and geochemistry characteristics, those of the cherts can correlate with cherts from the Sa Kaeo area, representing the Early and Middle Permian chert sequences, originated in a back-arc basin setting rather than formed in a vast oceanic setting of the Paleo-Tethys Ocean. This study confirms an existence evidence of a back-arc basin chert in the Central Thailand, extending the known distribution of the Sa Kaeo suture zone northwestward from the Uthai Thani and Nakhon Sawan areas into the Sawan Khalok area, and continues toward the Nan suture. These stratigraphic relationships can be explained by the fact that the bedded cherts were thrust onto the structurally higher rocks of the Sukhothai Zone, due to lateral shortening tectonics associated with the closure of the back-arc basin. |
