Zircon U-Pb Geochronology and Geochemistry of the Gneissic Granodiorite inManite Area from East Kunlun, with Implications for Geodynamic Setting
Zhao Feifei
Sun Fengyue
Liu Jinlong
Abstract：In order to determine the formation time, magma source, and tectonic setting of the gneissic granodiorite in Manite area, East Kunlun, zircon U-Pb dating, Hf isotope data and geochemistry of the gneissic granodiorite are studied in this paper.The chronology indicates that the magmatic zircon LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) U-Pb weighted mean age of the Manite gneissic granodiorite in the East Kunlun is 495.6±1.1Ma (MSWD=0.13), belonging to the Late Cambrian.The gneissic granodiorites have SiO2 of 61.47%-63.99%, Na2O of 2.91%~3.64%, K2O of 0.93%-2.31%, CaO of 4.29%-6.52%, ALK of 3.92%-5.69% and A/CNK=0.83~0.97.Chemically, they are metaluminous and belong to calc-alkaline rock series.The gneissic granodiorite is characterized by the enrichment of LILEs (Rb and K) and incompatible elements(Th and U), and depletion of HFSEs(Nb, Ta, Zr and Ti).The ratios of Nb/Ta, La/Nb, Th/Nb and Th/La show crustal characteristics.The εHf(t) values of zircons from the gneissic granodiorite range from 12.2-15.0, their Hf two-stage model ages vary from 506 to 662Ma.The initial materials are mainly derived from the juvenile crust.The gneissic granodiorite falls into the volcano arc granite area with the determination of trace elements in Rb-(Y+Nb) tectonic discrimination diagram and falls into the zone of pre-plate collision with the characteristics of active continental margin before the collision.Combined with the geochronological data, geochemical characteristics and the regional tectonic evolution, it is concluded that the gneissic granodiorite in the Manite area was formed in the environment of Proto-Tethys Ocean crust subduction, presumably it belongs to the southward subduction of oceanic crust.The crust between the Qaidam massif and Wanbaogou oceanic plateau occurred bidirectional subduction to the south and the north.
Keywords：gneissic granodioritegeochemistryzircon U-Pb datinggeochronologyManite areaEast Kunlun
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：15( 927-940,1044 )