Y.-T. Yang / Earth-Science Reviews 126 (2013) 96–115 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev An unrecognized major collision of the Okhotomorsk Block with East Asia during the Late Cretaceous, constraints on the plate reorganization of the Northwest Pacific Yong-Tai Yang ⁎ CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China article info abstract Article history: Interactions at plate boundaries induce stresses that constitute critical controls on the structural evolution of Received 28 February 2013 intraplate regions. However, the traditional tectonic model for the East Asian margin during the Mesozoic, invoking Accepted 30 July 2013 successive episodes of paleo-Pacific oceanic subduction, does not provide an adequate context for important Late Available online 8 August 2013 Cretaceous dynamics across East Asia, including: continental-scale orogenic processes, significant sinistral strike- slip faulting, and several others. The integration of numerous documented field relations requires a new tectonic Keywords: model, as proposed here. The Okhotomorsk continental block, currently residing below the Okhotsk Sea in Continental collision Continental transform boundary Northeast Asia, was located in the interior of the Izanagi Plate before the Late Cretaceous. It moved northwest- East Asia ward with the Izanagi Plate and collided with the South China Block at about 100 Ma. The indentation of the Northwest Pacific Okhotomorsk Block within East Asia resulted in the formation of a sinistral strike-slip fault system in South China, Okhotomorsk Block formation of a dextral strike-slip fault system in North China, and regional northwest–southeast shortening and Late Cretaceous orogenic uplift in East Asia. Northeast-striking mountain belts over 500 km wide extended from Southeast China to Southwest Japan and South Korea. The peak metamorphism at about 89 Ma of the Sanbagawa high- pressure metamorphic belt in Southwest Japan was probably related to the continental subduction of the Okhotomorsk Block beneath the East Asian margin. Subsequently, the north-northwestward change of motion direction of the Izanagi Plate led to the northward movement of the Okhotomorsk Block along the East Asian margin, forming a significant sinistral continental transform boundary similar to the San Andreas fault system in California. Sanbagawa metamorphic rocks in Southwest Japan were rapidly exhumed through the several- kilometer wide ductile shear zone at the lower crust and upper mantle level. Accretionary complexes successively accumulated along the East Asian margin during the Jurassic–Early Cretaceous were subdivided into narrow and subparallel belts by the upper crustal strike-slip fault system. The departure of the Okhotomorsk Block from the northeast-striking Asian margin resulted in the occurrence of an extensional setting and formation of a wide magmatic belt to the west of the margin. In the Campanian, the block collided with the Siberian margin, in Northeast Asia. At about 77 Ma, a new oceanic subduction occurred to the south of the Okhotomorsk Block, ending its long-distance northward motion. Based on the new tectonic model, the abundant Late Archean to Early Proterozoic detrital zircons in the Cretaceous sandstones in Kamchatka, Southwest Japan, and Taiwan are interpreted to have been sourced from the Okhotomorsk Block basement which possibly formed during the Late Archean and Early Proterozoic. The new model suggests a rapidly northward-moving Okhotomorsk Block at an average speed of 22.5 cm/yr during 89–77 Ma. It is hypothesized that the Okhotomorsk–East Asia collision during 100–89 Ma slowed down the northwestward motion of the Izanagi Plate, while slab pull forces produced from the subducting Izanagi Plate beneath the Siberian margin redirected the plate from northwestward to north-northwestward motion at about 90–89 Ma. © 2013 Elsevier B.V. All rights reserved. Contents 1. Introduction...............................................................97 2. GeologicalsettingoftheOkhotomorskBlockandJapanIslands........................................98 3. Thenewtectonicmodel......................................................... 103 3.1. ThecollisionoftheOkhotomorskBlockwiththeEastAsianmargin.................................. 103 3.2. Strike-slipmotionoftheOkhotomorskBlock............................................ 105 ⁎ Tel.: +86 0551 63607193. E-mail address: [email protected]. 0012-8252/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.earscirev.2013.07.010 Y.-T. Yang / Earth-Science Reviews 126 (2013) 96–115 97 3.2.1. Thesinistraltransformfaultzone............................................. 105 3.2.2. Effectsinamuchbroaderregion............................................. 106 3.2.3. Extensionandmagmatismfollowingthetranspressionalregime.............................. 107 3.3. ThecollisionoftheOkhotomorskBlockwiththeSiberianmargin.................................. 108 4. EvidencesofArcheanandEarlyProterozoiczircons............................................ 108 4.1. U–Pbdatingofdetritalzircons.................................................. 108 4.2. Newinterpretations....................................................... 109 5. EvolutionoftheSanbagawaHPmetamorphicbelt............................................. 109 6. Discussions.............................................................. 110 6.1. TheOkhotomorskBlockbeforetheLateCretaceous......................................... 110 6.2. Constraints on the plate reorganization of the Northwest PacificduringtheCNS............................ 110 6.3. The Okhotomorsk–EastAsiacollisionandtheEarlyCretaceousandCenozoicextensionaleventsinEastChina.............. 111 7. Conclusions.............................................................. 112 Acknowledgments............................................................. 112 References................................................................. 112 1. Introduction Tectonic Line (MTL) (Taira et al., 1983; Takagi, 1986; Otsuki, 1992), Tanakura Tectonic Line (TTL) (Taira et al., 1983; Otsuki, 1992), and Cen- Reconstructing tectonic processes operating along the East Asian tral Sikhote-Alin Fault (CSAF) (Zonenshain et al., 1990), etc. (Figs. 1 and margin (Figs. 1 and 2) during the Cretaceous is important for under- 2). Moreover, a series of small NE–SW trending pull apart basins devel- standing the geologic evolution of East Asia, especially in extensive oped in Southeast China during the Late Cretaceous (Charvet et al., intraplate regions, and for constraining plate reconstructions of the 1994; Lapierre et al., 1997; Ma et al., 2009). Structural studies indicated paleo-Pacific Ocean (Engebretson et al., 1985; Lithgow-Bertelloni and that Japan Islands (Taira et al., 1983; Kanaori, 1990; Otsuki, 1992)and Richards, 1998; Smith, 2003; Norton, 2007; Seton et al., 2012), particu- South Korea (Hwang et al., 2008) are subdivided into many blocks by larly during the Cretaceous Normal Superchron (CNS) (125–84 Ma), a strike-slip faults and the Late Cretaceous igneous rocks are mainly dis- time of no magnetic reversals. It is generally accepted that the East tributed around these faults. However, the current oceanic subduction Asian margin has experienced successive oceanic subduction with model is unable to reconcile these ubiquitous strike-slip features with occasional oceanic ridge collision since the Paleozoic (Isozaki, 1996; the subhorizontal internal structure of the crust in SW Japan, as imaged Maruyama et al., 1997; Isozaki et al., 2010). However, a series of geolog- by seismic data (Ito et al., 2009)(Fig. 2c). Because of this, the idea ical events occurred in East Asia during the early Late Cretaceous are of strike-slip-fault-controlled tectonics in Japan (Taira et al., 1983; poorly explained by this successive oceanic subduction model. Kanaori, 1990; Otsuki, 1992)(Fig. 4) has been completely abandoned Many thermochronologic, structural, and stratigraphic studies have (Isozaki et al., 2010). indicated that a continental-scale NW–SE shortening event occurred Other features unaccounted for in the traditional tectonic model in East Asia during the early Late Cretaceous (Charvetetal.,1994; include: ubiquitous thrusting features, high metamorphic pressure and Lapierre et al., 1997; Ratschbacher et al., 2003), which was intervened fast exhumation of Sanbagawa high-pressure metamorphic rocks, and cer- between two widespread extensional episodes in the Early Cretaceous, tain geochemical characteristics of granites in SW Japan (Fig. 2), which and in the latest Cretaceous–Cenozoic, respectively (Watson et al., are best explained by episodic collision and underthrusting of micro- 1987; Ren et al., 2002). During this period, major mountains and basins continents (Charvet, 2013). Although various relatively small-scale conti- were rapidly uplifted and exhumed, including: the Nanling Mountains nental collisional events during the Late Jurassic–Cretaceous have been (NL) (Chen, 2000), Wuyi Mountains (WY) (Chen, 2000), Yellow proposed at the proto-Japan margin (Jolivet et al., 1988; Otsuki, 1992; Mountains (Y) (Zheng et al., 2011), Xuefeng Mountains (XF) (Yan et al., Charvet, 2013) and at the SE China margin (Charvet et al., 1994; Lapierre 2011), Sichuan Basin (SB) (Shen et al., 2009), Qinling–Dabie mountain et al., 1997;