Introduction Directory UMM :Data Elmu:jurnal:J-a:Journal of Asian Earth Science:Vol18.Issue6.Dec2000:

The Bentong–Raub Suture Zone I. Metcalfe Asia Centre, University of New England, Armidale, NSW 2351, Australia Received 7 February 2000; accepted 25 July 2000 Abstract It is proposed that the Bentong–Raub Suture Zone represents a segment of the main Devonian to Middle Triassic Palaeo-Tethys ocean, and forms the boundary between the Gondwana-derived Sibumasu and Indochina terranes. Palaeo-Tethyan oceanic ribbon-bedded cherts preserved in the suture zone range in age from Middle Devonian to Middle Permian, and me´lange includes chert and limestone clasts that range in age from Lower Carboniferous to Lower Permian. This indicates that the Palaeo-Tethys opened in the Devonian, when Indochina and other Chinese blocks separated from Gondwana, and closed in the Late Triassic Peninsular Malaysia segment. The suture zone is the result of northwards subduction of the Palaeo-Tethys ocean beneath Indochina in the Late Palaeozoic and the Triassic collision of the Sibumasu terrane with, and the underthrusting of, Indochina. Tectonostratigraphic, palaeobiogeographic and palaeomagnetic data indicate that the Sibumasu Terrane separated from Gondwana in the late Sakmarian, and then drifted rapidly northwards during the Permian–Triassic. During the Permian subduction phase, the East Malaya volcano-plutonic arc, with I-Type granitoids and intermediate to acidic volcanism, was developed on the margin of Indochina. The main structural discontinuity in Peninsular Malaysia occurs between Palaeozoic and Triassic rocks, and orogenic deformation appears to have been initiated in the Upper Permian to Lower Triassic, when Sibumasu began to collide with Indochina. During the Early to Middle Triassic, A-Type subduction and crustal thickening generated the Main Range syn- to post-orogenic granites, which were emplaced in the Late Triassic–Early Jurassic. A foredeep basin developed on the depressed margin of Sibumasu in front of the uplifted accretionary complex in which the Semanggol “Formation” rocks accumulated. The suture zone is covered by a latest Triassic, Jurassic and Cretaceous, mainly continental, red bed overlap sequence. q 2000 Elsevier Science Ltd. All rights reserved. Keywords: Bentong–Raub Suture Zone; Semantan basin; Permian–Triassic boundary

1. Introduction

The belt of Lower Palaeozoic rocks that extends from the Malay Peninsula northwards through Thailand, Burma and China was termed the Yunnan–Malaya Geosyncline by Burton 1967. Jones 1968, 1973 further interpreted the stratigraphy and north–south facies belts of the Malayan portion as representing “miogeosynclinal” shelf or platform facies in the west, and “eugeosynclinal” facies containing radiolarian cherts, basic igneous rocks and thick sections of deep-marine clastics in central Malaya. He also suggested the former presence of a large continental landmass to the west, which has since rifted away now interpreted as Gond- wanaland. Hutchison 1973a placed the data in a plate- tectonics context and interpreted the “eugeosyncline” as a former trench in a subduction system. Hutchison 1975, in his paper on ophiolites in Southeast Asia, named the central Malayan zone the “Bentong–Raub ophiolite line”, which then became widely quoted as the “Bentong–Raub Line”, or alternatively as the “Raub–Bentong Line”. Mitchell 1977, furthermore, interpreted the zone of “folded slates, radiolarian cherts and flysch, with vertical or overturned isoclinal folds, and minor ophiolitic bodies” his Zone 2 as representing oceanic crust and sediments, forming an accretionary complex produced by eastwards subduction. Establishment of this zone as a suture zone representing the site of a former ocean now seems beyond doubt, and it is now generally referred to as the Bentong–Raub Suture Zone. The north–south trending Bentong–Raub Suture extends from Thailand through Raub and Bentong to the east of Malacca, Peninsular Malaysia. Southwards extension of the suture is controversial see below. This suture represents the main Palaeo-Tethys Ocean which was destroyed by collision of the Sibumasu and Indochina continental terranes of Southeast Asia Fig. 1. This paper presents an overview of the Bentong–Raub Suture Zone, and reviews the evidence for the age-duration of the Palaeo-Tethys Ocean which it represents, and the age of suturing of the Sibumasu and Indochina terranes. Impli- cations for palaeogeographic reconstructions of the region are also discussed. Journal of Asian Earth Sciences 18 2000 691–712 1367-912000 - see front matter q 2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 6 7 - 9 1 2 0 0 0 0 0 0 4 3 - 2 www.elsevier.nllocatejseaes E-mail address: imetcalfmetz.une.edu.au I. Metcalfe.

2. Geological setting of the Bentong–Raub Suture Zone