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1. Introduction
Active continental margins record the evolutionary history of subduction-related magmatic events (Murphy, 2006; Xiao et al.2016; Lallemand & Heuret, 2017) and can be considered the central region of continental crustal growth (Franz et al.2006; Vogt et al.2012) in continental collision zones. The Karakoram terrane forms the southern margin of the Asian plate (Jain & Singh, 2008; Searle & Hacker, 2018), which has witnessed periodic episodes of continental arc magmatism since Early Cretaceous time (Weinberg et al.2000; Fraser et al.2001; Heuberger et al.2007; Upadhyay, 2008; Jain & Singh, 2009; Ravikant et al.2009; Kumar et al.2017). The accretion of the Karakoram with Asia was the result of the separation and northward drifting of the Karakoram from Gondwana that occurred during Permian time (Boulin, 1981; Tapponnier et al.1981). Further, the closure of the Tethys ocean between the Indian and Asian plates along two suture zones, the Indus Tsangpo Suture Zone (ITSZ) in the south and Shyok Suture Zone (SSZ)/Main Karakoram Thrust (MKT) in the north, led to the formation of magmatic arcs during Mesozoic–early Tertiary times (Fig. 1a) (Windley, 1988; Jain & Singh, 2008).
Fig. 1.
Overview map of the Himalayan–Tibetan orogenic belt and geologic map across the Karakoram and Ladakh. (a) Map showing the main tectonic structures and sutures in the Himalaya, Tibet and the Karakoram region. (b) Simplified map showing the regional geology of the eastern Karakoram region (after Phillips, 2008) with the location of the study area in the rectangle. (c) Geological map of the SE Karakoram with the locations of collected samples from the Karakoram Batholith. The Longmu–Ghoza Co fault (LGF) and Angmong fault (AF) are from van Buer et al. (2015) (modified after Phillips et al.2004; Jain & Singh 2008; Ravikant et al.2009). (Sample location SM 9 includes both SM 9A and SM 9B).
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A significant amount of data have been published to constrain the magmatic evolution of the Ladakh and Karakoram regions, which has helped to understand the geodynamic evolution of the India–Asia collision zone (e.g. Searle et al.1987; Klootwijk et al.1992; Rowley, 1996; Najman et al.2010; Hu et al.2016). However, the timing of suturing along the SSZ is still not...