LIU Xin-xing1, WANG Zhi-hui1, ZHANG Juan1*, ZHAO Zheng2, ZUO Ming-hui3, DING Ming4
（1.School of Resources, Hebei GEO University, Shijiazhuang 050031, China;
2. Institute of Mineral Resource, Chinese Academy of Geological Sciences, Beijing 100037, China;
3. School of Earth Science, China University of Geosciences, Wuhan 430074, China;
4. Gannan Geological Survey Party of Jiangxi Province, Ganzhou 341000, China）
Abstract: This paper presents LA-ICP-MS zircon U-Pb ages, whole-rock major and trace elements geochemical data of the Qianchang dioritic intrusion in Ganzhou City, Jiangxi Province, in order to constrain the emplacement age, property of magmatic source, petrogenesis of the intrusion, and geological significances of those geochemical data. Zircon grains from those diorite samples are euhedral-subhedral crystals, with obvious oscillatory growth zoning and Th/U ratios of 0.69- 1.17, indicating a magmatic origin. Zircon U-Pb dating results show that the emplacement age of Qianchang diorite is 463.5±5.0 Ma. The Qianchang diorite samples are characterized with stable SiO2 concentrations of 54-56% and high potassium ( K2O > Na2O) features, with Rittmann indexes of 2.28-2.55 (< 3.3) and the mean A/CNK value of 0.69. The diorite belongs to the high potassium calc-alkaline metaluminous rock series. The diorite samples have average REE content of 182.04 ug/g, with enriched light rare earth elements (LREEs) and large ion lithophile elements (LILEs), depleted heavy rare earth elements (HREEs) and high field strength elements (HFSEs), and weak negative Eu anomalies (？Eu = 0.71-0.75), suggesting the existence of residual plagioclase in the source area. These rocks are obviously enriched in LILE (such as Pb and K), but relatively depleted in HFSE (such as Nb, Ta, and Ti). Petro-geochemical results show that the magma of Qianchang diorite could be sourced from the subduction fluid metasomatized mantle wedge which was formed in association with the subduction of oceanic slab in the active continental margin setting.
Keywords: Zircon U-Pb chronology; Petrochemical feature; Trace element characteristics; petrogenesis; The Qianchang diorite
ACTA MINERALOGICA SINICA Vol. 39, No.3, 2019, page 271-280
