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RESEARCH Tectonic Processes, from Rifting To RESEARCH Tectonic processes, from rifting to collision via subduction, in SE Asia and the western Pacifi c: A key to understanding the architecture of the Central Asian Orogenic Belt Koji Wakita1,*, Manuel Pubellier2,*, and Brian F. Windley3,* 1DIVISION OF PHYSICS AND EARTH SYSTEM SCIENCES, GRADUATE SCHOOL OF SCIENCE AND ENGINEERING, YAMAGUCHI UNIVERSITY, YOSHIDA 1677-1, YAMAGUCHI 753-8512, JAPAN 2UNIVERSITY TEKNOLOGI PETRONAS, UTP, PERAK, MALAYSIA, AND CNRS-UMR 8538, LABORATOIRE DE GÉOLOGIE DE L’ECOLE NORMALE SUPÉRIEURE, 24 RUE LHOMOND, 75231 PARIS, CEDEX 5, FRANCE 3DEPARTMENT OF GEOLOGY, UNIVERSITY OF LEICESTER, LEICESTER LEI 7RH, UK ABSTRACT We review the processes of accretion of continental blocks during the Tertiary in SE Asia and the western Pacifi c with the aim of better under- standing the evolution of the Central Asian Orogenic Belt, which is a Neoproterozoic to mid-Phanerozoic orogenic collage surrounded by the East European, Siberian, Tarim, and North China cratons. In the western Pacifi c, there is abundant evidence of sequential plate-tectonic pro- cesses from accretion to continent-arc/continent collision, via exhumation and suprasubduction. Early processes involve seafl oor spread- ing, subduction, accretion, arc formation, and back-arc extension. Two important types of tectonic setting and evolution are recognized along the present Pacifi c convergent margin: sediment/crust accretion and tectonic erosion. Five major accretionary complexes are well illustrated in the Japanese Islands. Tectonic erosion removes material by underscraping the lower part of the upper plate. Subduction is also associ- ated with back-arc extension, particularly in Indonesia and the SW Pacifi c region. Arc-arc collisional complexes are present in Taiwan, the Philippines, and Japan. The geological record of SE Asia and the western Pacifi c provides a robust modern analogue for the geological and tectonic history of the Central Asian Orogenic Belt, before it was affected by high-temperature metamorphism. LITHOSPHERE; v. 5; no. 3; p. 265–276 | Published online 20 March 2013 doi: 10.1130/L234.1 INTRODUCTION lier et al., 2005; Pubellier, 2008; Metcalfe, 2010; Yin, 2010). In order to help unravel the complex accretionary framework and evolution of the The Central Asian Orogenic Belt (or Altaids, 600–250 Ma) is a ca. Central Asian Orogenic Belt, we review the modern analogue of the Pha- 1.0 Ga–250 Ma tectonic collage of oceanic and continental fragments that nerozoic geology of SE Asia and the western Pacifi c (Fig. 2). This paper includes ophiolites, island arcs, Andean-type magmatic arcs, subduction- relates the main tectonic processes that have taken place in the western accretion complexes, passive margins, seamounts, and microcontinents Pacifi c through Phanerozoic time, from ocean formation and arc creation (Şengör and Natal’in, 1996; Jahn, 2004; Kröner et al., 2007; Windley, 2007; to subduction-accretion and the formation of suture zones, with those that Wilhem et al., 2012). It also contains high-pressure (HP) blueschists and probably took place in the Central Asian Orogenic Belt during the early eclogites, high-temperature (HT) metamorphic rocks, postaccretionary Paleozoic. Hence, the examples selected hereafter are located between the granitic-alkaline-peralkaline rocks, and important mineral deposits of, for Central Asian Orogenic Belt and the present-day plate boundary (Sunda example, Au and porphyry Cu. The Central Asian Orogenic Belt (COAB) Trench and India-Eurasia collision zone). is widely regarded to have evolved in a tectonic setting like that of modern Indonesia (e.g., Xiao et al., 2010); however, because of the late HT overprint CONTINENTAL BREAKUP, DISPERSAL, AND FORMATION OF and the old age of the Central Asian Orogenic Belt’s construction, the original OCEANIC PLATES paleogeographic architecture and tectonic evolution are still poorly known. SE Asia and the western Pacifi c are no doubt the best world laboratory Microcontinents, detached from Gondwana, moved northward to col- for understanding the geological and tectonic processes that take place in lide with the margins of the Asian continent, which became larger with the oceans and during accretion (Fig. 1) before any continent-continent time (Metcalfe, 2010). The early history of the breakup of Gondwana in collision has occurred (Lallemand et al., 2001; Hall, 2002, 2010; Pubel- the Devonian and the start of the Paleo-Tethys Ocean are recorded, for example, in Chiang Dao, north Thailand (Hara et al., 2010), where anoxic *E-mails: [email protected]; [email protected], brian sediments were deposited in confi ned basins along the Gondwana margin [email protected]. (Fig. 3). Once the continental fragments detached and drifted away from Editor’s note: This article is part of a special issue titled “Comparative evo- Gondwana, oxidized seawater fl owed into the basins, enabling growth of lution of past and present accretionary orogens: Central Asia and the Circum- Pacifi c,” edited by Robert Hall, Bor-Ming Jahn, John Wakabayashi, and Wenjiao small organisms such as plankton, radiolarian, and pelagic foraminifera. Xiao. More papers on this subject will follow in subsequent issues, and these will The rifting of an ocean is traditionally considered to be triggered by be collected online at http://lithosphere.gsapubs.org/ (click on Themed Issues). the subduction of an existing ocean. For example, Neo-Tethys opened LITHOSPHEREFor permission to| Volumecopy, contact 5 | Number [email protected] 3 | www.gsapubs.org | © 2013 Geological Society of America 265 Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/5/3/265/3050653/265.pdf by guest on 24 September 2021 WAKITA ET AL. Figure 1. Major tectonic features in East Asia and the western Pacifi c (modifi ed from Pubellier, 2008), (A) Cenozoic accretionary complexes, (B) Pre- Cenozoic orogenic belts (terranes), Legend for Figures 1, 2, 5 and 6 is as follows. Gray—Proterozoic consolidated craton, Yellow—Pliocene-Quater- nary accretionary wedge or Fold-and-Thrust Belt (FTB), Light brown—Late Neogene-accreted terrane, Orange—Tertiary accretionary wedges or FTB, Ochre—Alpine/Himalayan-accreted terrane, Green—Mesozoic Continental accreted terrane, Bluish-green—late Mesozoic accretionary wedges or FTB, Mauve: Indonesian/Early Mesocoic-accreted terrane or FTB, Brown—Late Paleozoic/Hercynian accreted terrane or FTB, Blue—Early Paleozoic/Caledo- nian-accreted terrane or FTB, Black—reported ophiolitic occurrences. Figure 2. Comparison between Central Asian Orogenic Belt (A: left) and present tectonic setting of East Asia (B: right: top to the west) (modifi ed from Pubellier, 2008). 266 www.gsapubs.org | Volume 5 | Number 3 | LITHOSPHERE Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/5/3/265/3050653/265.pdf by guest on 24 September 2021 Tectonic processes from rifting to collision via subduction | RESEARCH Figure 3. Initiation of Paleo-Tethys Ocean and its record in the stratigraphic column of northern Thailand (stratigraphic column after Hara et al., 2010). in response to the subduction of Paleo-Tethys (Şengör, 1987). In mod- graptolites. In ascending order, the sequence consists of thinly bedded ern examples, the trench pull is responsible for the formation of back-arc black shale, thinly bedded black siliceous shale, interbeds of black sili- basins fl oored with a large oceanic crust in the upper plate (Karig and ceous shale and white chert, and bedded white chert; the overall change Sharman, 1975), or in the downgoing plate as observed for the South from black shale to chert is gradual. The black shales decrease in thickness China Sea (Bénard et al., 1990; Pubellier et al., 2003). According to toward the stratigraphic top, as do the numbers of interbeds of black shale Stampfl i (2000) and Wang et al. (2010), the opening of Paleo-Tethys took in bedded chert. This lithologic change from black shale to white bedded place in the Late Ordovician and Silurian. On the other hand, Metcalfe chert represents the biological recovery from anoxic to oxic conditions in (2010) suggested that several Chinese continental blocks, including Indo- the opening basin. Paleo-Tethys started to open, not in the Late Devonian, china, separated in the Late Devonian from Gondwana. The history of the but in the Early Devonian. The sequence from northern Thailand to Penin- Paleo-Tethys Ocean from birth to death is recognizable in the pelagic and sular Malaysia records the early stage of opening of Paleo-Tethys (Fig. 3), hemiplegic sequences of ocean plate stratigraphy, which record the ridge- and the Lower Devonian–Late Triassic stratigraphy represents the history trench transition from the Devonian to the Triassic (Wakita and Metcalfe, of Paleo-Tethys from its opening to closure. 2005). The Cimmerian continent including the Sibumasu block collided with Indochina in Triassic time. However, the age of opening of Paleo- Ocean Plate Stratigraphy and the History of Paleo-Tethys Tethys was not clear until Wonganan and Caridroit (2005) revealed the presence of a continuous ocean-fl oor sequence from the Lower Devonian Ocean plate stratigraphy records the travel history of an oceanic plate to Lower Carboniferous in northern Thailand. from its “birth” at a mid-oceanic ridge to its “death” at a trench (Matsuda The Thailand sequence is composed of Lower Devonian black shale and Isozaki, 1991; Wakita and Metcalfe, 2005). Ocean plate stratigraphy and younger cherts (Fig. 3). The black shale contains Early Devonian is an idealized stratigraphic succession of an ocean-fl oor trench, obtained LITHOSPHERE | Volume 5 | Number 3 | www.gsapubs.org 267 Downloaded from http://pubs.geoscienceworld.org/gsa/lithosphere/article-pdf/5/3/265/3050653/265.pdf by guest on 24 September 2021 WAKITA ET AL. from protoliths in ancient accretionary complexes. However, in some Also, when seamounts arrive at a subduction zone, their upper volcanic cases in SE Asia, the generally dismembered ophiolites and their overly- rocks and sediments are commonly scraped off along deep-seated décol- ing stratigraphic oceanic series may represent relicts of back-arc basins lements.
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