Geological understanding of plate tectonics: Basic concepts, illustrations, examples and new perspectives

Abstract

Publisher's copyright statement:This article is available under CC-BY-NC Creative Commons Attribution Non-Commercial Licence, which permits users to use, reproduce, disseminate or display the article provided that the author is attributed as the original creator and that the reuse is restricted to non-commercial purposes i.e. research or educational use. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. With 16 figuresAbstract: In this paper, I have reviewed some basic concepts of the plate tectonics theory in a plain geological language with the aim of encouraging geologists to correctly understand this theory in its applications to geological problems. I emphasized the decisive role of subduction as the ultimate (dominant) driving force of all the plate tectonics phenomena. Hence, my discussion has focused on major issues such as the origin of subduction zones, slab rollback, trench retreat, trench suction and driving mechanism of plate motion (both oceanic and continental) by means of illustration with hypothetical and real examples. As much of the discussion is heavily based on my personal (original) perspectives, some of the concepts, interpretations and hypotheses may not be familiar to many and may not be readily found in the existing literature. Mantle plume hypothesis is not the focus of this paper and is thus only mentioned in passing.

Assembly of the Lhasa and Qiangtang terranes in central Tibet by divergent double subduction

“…This synthesis corroborates the southward subduction of Bangong Ocean lithosphere beneath the Lhasa Terrane and argues that this subduction is analogous to the westward subduction of the Pacific lithosphere that led to the development of back-arc basins in the western Pacific (Schellart et al, 2006;Cawood et al, 2009;Niu, 2014), providing a good example to evaluate mantle geodynamics operating during Gondwana dispersion and Asian accretion.…”

“…120 Ma mafic dykes (Fig. 1) leads to the rupture propagating from the south to the north, eventually resulting in its complete detachment from the overlying crust (Soesoo et al, 1997) and/or breakoff due to continued slab pull through mineral phase changes at depth producing excess negative buoyancy (Niu, 2014) (Fig. 5d).…”

“…retreating subduction zone beneath the eastern Australian and Eurasian plate causing the overriding plate to extend (corresponding to the Lhasa Terrane) (Schellart et al, 2006;Cawood et al, 2009;Niu, 2014). In particular, the northward retreat of the southward-dipping subduction zone may have driven the separation of the Lhasa Terrane from Gondwana margin during the Late Triassic (Sengör, 1979;Zhu et al, 2011Zhu et al, , 2013Pan et al, 2012;Metcalfe, 2013) and the development of back-arc basins represented by the Shiquan River-Nam Tso mélange zone during the Mid-Late Jurassic (Zhu et al, 2011Pan et al, 2012).…”

Slab breakoff: a causal mechanism or pure convenience?

“…The continued India-Asia convergence since the collision is actually a consequence of active subduction of different parts of the same giant "rigid" Indo-Australia plate [12]. The active subduction of the same "rigid" plate at the Sumatra-Indonesia trench drags the India-Asia convergence, thus the continued underthrusting of the Indian mantle lithosphere beneath the Tibetan lithosphere [12], which also explains why the position of the India-Asia suture has migrated northward from ~ 21°N at ~ 50 Ma to ~ 29°N at present [20]. The Indian + Tibetan mantle lithosphere doubling explains the thickened lithosphere and high elevation beneath the greater Tibetan plateau (Fig.…”

“…The latter is further supported by the fact that arc magmas are geochemically more depleted if the mantle-wedge material has been previously depleted beneath a back-arc basin (vs. settings without back-arc spreading). Subduction would stop (or stop shortly) upon continental collision [8,12]. It follows that mantle wedge corner flow would diminish and flux-melting would also diminish if they do not stop immediately.…”