Petrogenesis and tectonic setting of the Shanzhuang monzogranites in central Jiangxi Province, South China: Evidence from lithology, geochemistry and zircon U-Pb geochronology
This paper presents a systemic study on geochronology, geochemistry and Sr-Nd isotopes of the northern monzogranite from Shanzhuang granitic pluton located on the southern part of the Qinhang Metallogenic Belt in central Jiangxi Province which comprises monzogranite and granodiorite to constrain its emplacement age, petrogenesis and tectonic setting. All zircons from the monzogranite are confirmed to be of magmatic origin by CL imaging, Th/U ratio and diagrams of (Sm/La)(N)-La and Ce/Ce*-(Sm/La)(N) and are divided into three groups. The weighted mean age (420 similar to 419Ma) of the first group is interpreted as crystallization age of the monzogranite. The Shanzhuang monzogranite, which has SiO2 content of 71.48% similar to 66.20%, K2O/Na2O ratio of 1.24 similar to 0.99 and A/CNK ratio of >1.1, with the emergences of muscovite and garnet as well as ACF diagram and negative correlations of Rb with Th and Y, belongs to high K calc-alkaline, strongly peraluminous S-type granite. Meanwhile, this type rock defined by a depletion in large ion lithophile elements Ba and Sr and high field strength elements Nb and Ta is interpreted as a product of partial melting of the crust-derived materials. The ratios of CaO/Na2O (0.14 similar to 0.07), Rb/Sr (8.27 similar to 3.83) and Rb/Ba (1.48 similar to 0.82), the content of FeOT + MgO + TiO2 (2.4 similar to 1.8) and the t(2DM) ages (2031 similar to 1971Ma) together suggest that the protolith of the monzogranite is Paleoproterozoie clay-rich argillaceous rocks. Moreover, the monzogranite is likely formed at a temperature condition (722 similar to 720 degrees C) constrained by saturation- and Ti temperatures of zircon, and a pressure condition of 2.71 similar to 3.21kbar constrained by the Ti-in-biotite geothermometer. Combined with the Paleozoic tectonic development of South China, the diagram of Rb-(Y + Nb) shows that the geological setting of Shanzhuang granitic pluton is post-collision. In summary, the Shanzhuang pluton was formed by partial melting of Paleoproterozoic clay-rich argillaceous rocks at a low temperature and a low pressure condition under post-collisional setting
