Age, trace elements and Hf-isotope composition of zircon in eclogites from the sulu UHP belt, East-Central China: Neoproterozoic intrusion and subsequent Paleozoic and Early Mesozoic metamorphism

Abstract

The Sulu (苏鲁)-Dabie (大别) orogen in East-Central China formed during the subduction and collision of the Yangtze block with the North China block in Early Mesozoic (240-225 Ma). Constraints on the nature and derivation of eclogites, which are a significant component of the orogen, can provide useful information about subduction-zone metamorphism and crust-mantle interaction. The U-Pb ages, Hf-isotope ratios and trace-element compositions of zircons in eclogites from the Jiangzhuang (蒋庄) (Jiangsu (江苏) Province) and Rongcheng (荣成) (Shandong (山东) Province) areas indicate that the protoliths of the eclogites derived from ultramafic-mafic complexes or mafic intrusion in the subducted continental lithosphere. The upper intercept age of 852±10 Ma and high ε Hf (up to 14.7) of the Neoproterozoic zircons in a Jiangzhuang sample indicate that the protoliths represent products of the Neoproterozoic addition of juvenile materials to the older (i.e., Paleo-Mesoproterozoic) continental crust. The zircon ages of eclogites from both localities mainly record the Triassic (230-220 Ma) metamorphism, consistent with the formation of the Sulu orogen in Early Mesozoic. The lower intercept age of 316±4 Ma in a Jiangzhuang sample suggests that thermal activity relating to the paleoTethyan in Late Carboniferous also affected the eclogitic protolith. INTRODUCTIONThe Sulu-Dabie orogenic belt is one of the largest ultrahigh-pressure (UHP) metamorphic belts in the world. Sm-Nd geochronology of silicate minerals and zircon U-Pb dating have been widely used to reveal the metamorphic history of the collisional belt (Tang et al.

Geochemical fingerprints and pebbles zircon geochronology: Implications for the provenance and tectonic setting of Lower Cretaceous sediments in the Zhucheng Basin (Jiaodong peninsula, North China)

“…The rocks in the Jiaonan Orogen are mainly composed of ultrahigh-pressure metamorphic rocks from the Paleoproterozoic Fenzishan Group and Neoproterozoic granitic gneiss and granitic gneiss (Ni et al 2013). Granitic gneiss is the largest component of the ultrahigh-pressure metamorphic complex, accounting for 75% of the entire complex's outcropping area (Liu et al 2008;Zheng et al 2010). This observation agrees with the results obtained from the geochemical discrimination diagram, indicating that the sandstone's provenance includes intermediate rocks and felsic igneous rocks.…”

Linking continental deep subduction with destruction of a cratonic margin: strongly reworked North China SCLM intruded in the Triassic Sulu UHP belt

“…Late Mesozoic ages (160 ± 5 Ma), including one from Yangkou and two in the Hujialing samples, have also been found in peridotite xenoliths from the central part of the southern edge of the North China craton (i.e., the Xinyang basaltic-andesitic volcaniclastic diatremes, see Fig. 1a) and are interpreted as due to the reheating of the mantle during the Xinyang magmatism (Zheng et al 2008b) after the early stage of the exhumation of the Sulu-Dabie UHP belt (218 Ma, Wan et al 2005;Zheng et al 2010). …”

“…Raobazhai, the UHP garnet peridotite terrane from the prepilot hole of the Chinese Continental Scientific Drilling project CCSD-pp1 in the Sulu belt Yang and Jahn 2000) and Raobazhai in the Dabie belt (Zheng et al 2008a); both are Type A (Mantle) peridotite; c CCSD-MH ? Bixiling, the UHP garnet peridotite terrane from CCSD-MH in the Sulu belt Li and Yang 2007) and Bixiling in the Dabie belt (Zheng et al 2008a); both are Type B (Crustal) peridotite; d Phanerozoic (Shanwang and Nushan), the newly accreted lithospheric mantle derived from the cooling of the upwelled asthenosphere Xu et al 1998); e Archean (Hebi and Mengyin), the refractory mantle (Zheng et al 2001(Zheng et al , 2006c gneisses in the NCC, especially in the trans-North China orogen, Khondalite Belt and Jiao-Liao-Ji Belt (i.e., Guan et al 2002;Guo et al 2002;Wan et al 2005;Zhao et al 2010). Similar ages have been found in the northern part [i.e., Hannuoba peridotite and intermediate-granulite xenoliths (Zheng et al 2004d)], in the eastern margin (i.e., Fuxian mafic-granulite xenoliths, Zheng et al 2004b) and in the central part of the southern margin (i.e., Xinyang mafic-granulite xenoliths, Zheng et al 2008b) of the North China craton.…”