Revisiting the tectonic evolution of the Triassic Palaeo-Tethys convergence zone in northern Thailand inferred from detrital zircon U–Pb ages

Abstract

Detrital zircon U–Pb ages for sediments in and around the Palaeo-Tethyan convergence zone in northern Thailand provide constraints for tectonic interpretations of the Indochina Block, the Sibumasu Block, the Inthanon Zone accretionary complex and the Nan Back-arc Basin during the Triassic. In sedimentary rocks of the Indochina Block, almost all of the Palaeozoic and Triassic zircons were sourced from the collision zone between the Indochina and South China blocks, and an active continental margin in the western Indochina Block. Sediments of the Sibumasu Block were supplied by erosion of Archaean basement and from the Grenville and the Pan African orogenies, but show no record of Permian to Triassic igneous activity. Accretionary complex sediments have provenances of both the Sukhothai Arc and the Indochina and South China blocks, with detrital zircons of various ages being supplied from crustal uplift and erosion related to the Indosinian I orogeny. Sedimentary rocks of the Nan Back-arc Basin are widely distributed not only in the Nan–Uttaradit but also in northern Sukhothai areas. The origin of the Pha Som Metamorphic Complex and associated formations can be traced to basin-filling sediments in the Nan Back-arc Basin. These detrital zircon U–Pb ages have also allowed identification of the changing tectonic setting in the Palaeo-Tethys convergence zone from the ‘erosion of Proterozoic continental basement’ to ‘Palaeozoic active continental margin in the western Indochina Block’ and ‘Palaeozoic, Permian to Triassic collision zone between the South China and Indochina blocks’ through to ‘Triassic active Sukhothai Arc’.

Zircon U-Pb geochronology of the Lan Sang gneisses and its tectonic implications for the Mae Ping shear zone, NW Thailand

“…Moreover, the age cluster of ~508 Ma suggests that the sediments of these paragneiss protoliths primarily came from the Sibumasu terrane rather than the Indochina terrane (Lin et al, 2013;Kawakami et al, 2014;Dew et al, 2018). The age spectrum of detrital zircon cores in this study is also similar to that of Paleozoic sedimentary rocks from the Sibumasu terrane (Dew et al, 2021;Hara et al, 2021). Considering that the MPSZ is flanked by Cambrian quartzite and Permian limestone (Figure 3), it seems reasonable to infer that the protoliths of these paragneisses should be Paleozoic sedimentary rocks around the Sibumasu terrane.…”

“…500 Ma, revealing that the Sibumasu terrane was in a magmatic arcrelated regime on the Gondwana India-Australia margin (Lin et al, 2013;Kawakami et al, 2014;Dew et al, 2018). The exact location of the Precambrian basement rock remains unknown, with only clues from inherited and detrital zircon ages (Ahrendt et al, 1993;Watkinson et al, 2011;Cai et al, 2017;Dew et al, 2018;Österle et al, 2019;Dew et al, 2021;Hara et al, 2021). The majority of detrital zircon age spectra obtained from sedimentary and metasedimentary rocks in the Sibumasu terrane also exhibit a prominent peak either at 500 Ma or within 1,000-900 Ma (Cai et al, 2017;Dew et al, 2021;Hara et al, 2021).…”

“…The exact location of the Precambrian basement rock remains unknown, with only clues from inherited and detrital zircon ages (Ahrendt et al, 1993;Watkinson et al, 2011;Cai et al, 2017;Dew et al, 2018;Österle et al, 2019;Dew et al, 2021;Hara et al, 2021). The majority of detrital zircon age spectra obtained from sedimentary and metasedimentary rocks in the Sibumasu terrane also exhibit a prominent peak either at 500 Ma or within 1,000-900 Ma (Cai et al, 2017;Dew et al, 2021;Hara et al, 2021). This finding strongly indicates the presence of Neoproterozoic basement rocks in the Sibumasu terrane.…”

The Truong Son, Loei-Phetchabun, and Kontum Terranes in Indochina: Provenance, Rifting, and Collisions

“…Speculatively, the early Norian Indosinian I/II events picked on seismic sections (Booth and Sattayarak, 2011) may be due to the collision of South China and Truong Son possibly subsequent to the deeply subducted eclogite of the Song Ma Suture at about 233 Ma (Nakano et al, 2008(Nakano et al, , 2010. The Indosinian III Unconformity was probably due to the final consolidation of the terranes in the late Norian with the closure of the Nan Suture and the collision of Sukhothai, Inthanon, and Sibumasu terranes (Chaodumrong and Burrett, 1997;Hirsch et al, 2006;Barber et al, 2011;Kamata et al, 2013;Arboit et al, 2016;Hara et al, 2021).…”

Geology and petrochemistry of volcanic rocks in the Lam Sonthi area, Lop Buri province

“…Tuffaceous siltstone is locally observed along with the road cut (Road No .4069 location: 748660E and 1702700N). The Khao Luak Formation age is recently reported as 276±7 Ma (Early Permian) from the detrital zircons using the U-Pb zircon age dating technique of sandstones, which was collected from Nong Phai district, Phetchabun province (Hara et al, 2020) far north from the Lam Sonthi area. The Khao Luak Formation was interpreted as formed as the southern continuation of Nam Duk Formation (Ueno and Charoentitirat, 2011) which was a part of back arc basin that has been closed in the end of Permian (Malila et al, 2008;Sone and Metcalfe, 2008).…”