Dating thin zircon rims by NanoSIMS: the Fengtien nephrite (Taiwan) is the youngest jade on Earth

Age determination of nephrite by in-situ SIMS U–Pb dating syngenetic titanite: A case study of the nephrite deposit from Luanchuan, Henan, China

“…Therefore, accessory zircon in nephrite could be inherited from an igneous precursor and does not necessarily reflect the time of nephrite formation. The age of zircon can be considered as the upper limit for the age of nephrite (Liu et al, 2015;Yui et al, 2014;Zhou and Cheng, 2011). Radiometric dating of nephrite remains a subject of debate.…”

Ages of ophiolitic rocks along plate suture in Taiwan orogen: Fate of the South China Sea from subduction to collision

“…The island is divided in two parts ( Fig. 1): east of the Longitudinal Valley (plate suture), the Coastal Range is the accreted Luzon Arc belonging to the Philippine Sea Plate; west of the suture, the Eurasian part of the island is composed of (from west to east) (1) the Coastal Plain as the foreland basin (Lin et al 2003), (2) the Western Foothills and the Slate Belt as the fold-thrust belt (Chen et al 2011), (3) the Tailuko Belt as the exhumed continental margin basement (Yui et al 2012), and (4) the Yuli Belt as an exhumed blueschist-facies subduction complex (Yui et al 2014;Chen et al 2017b). The Lichi Mélange is distributed along the western flank of southern Coastal Range, with its matrix composed of sheared forearc sedimentary sequence (Chang et al 2001;Chen et al 2017a).…”

“…The type, tectonic settings and paleogeographic origin of the ophiolitic rocks are essential in plate reconstructions of the associated mountain building (e.g., Dilek and Furnes 2014;Xu et al 2015). As the obducted or exhumed remnants of the intervening oceanic lithosphere, the ophiolite-bearing belts offer invaluable evidences and insights to the subduction processes preceding arc-continent or continent-continent sutures, as well as the deformation and metamorphic overprint during successive orogenic processes (e.g., Ernst 2010;Yui et al 2014;Malavieille et al 2016). Therefore, the ophiolite-bearing belts are key components in discerning the overall architecture and evolution of convergent plate boundaries, whereas records of the processes responsible for the emplacement and exhumation of ophiolite-bearing belts are often obscured by later orogenic deformation and erosion.…”

“…The Lichi Mélange is an unmetamorphosed collisional mélange due to forearc closure, and is exposed along the western border of the accreted arc (Chang et al 2000;Chen et al 2017a). The Yuli Belt, previously considered to be the Mesozoic subduction zone of the paleo-Pacific Plate (the "Kula Plate"; Yui et al 1988), is recently re-interpreted as a blueschistfacies Miocene subduction complex juxtaposed east of the exhumed continental margin basement (Tsai et al 2013;Yui et al 2014;Chen et al 2017b). From initial subduction to final arc-continent collision, two major oceanic domains have been consumed and are the source candidates for ophiolites found in these belts: the South China Sea along the subducting plate interface, and the Philippine Sea Plate oceanic lithosphere in the Luzon forearc region.…”

“…The destruction of the ~100 km-wide Luzon forearc crust is essential in bringing the Luzon Arc to collisional contact with the exhumed continental margin (Lu and Hsu 1992;Shyu et al 2005); tectonic erosion through underthrusting beneath the arc is the currently favored mechanism (Chang et al 2001;Shyu et al 2011;Chen et al 2017a). Of the Taiwan ophiolite-bearing belts, only the Kenting Mélange was the direct product of South China Sea subduction and the ophiolitic rocks within are mostly of South China Sea affinity (e.g., Lu and Hsu 1992;Chang et al 2003;Zhang et al 2016;Tian et al 2019); debates remain for the origin of the ophiolitic rocks in the Lichi Mélange as either Philippine Sea Plate/Luzon forearc (e.g., Juan et al 1980;Malavieille et al 2002;Chang et al 2009;Huang et al 2018) or South China Sea (e.g., Chung and Sun 1992;Hsieh et al 2017); the mafic blocks within the Yuli Belt have been inferred from the South China Sea (Yui et al 2014;Chen et al 2017b;Beyssac et al 2008) but lack further constraints. Such ambiguities made tectonic interpretation and reconstruction difficult and fraught with uncertainties, especially for the Lichi-Yuli pair on the opposing sides of the active plate boundary, the Longitudinal Valley (Fig.…”