Petrogenesis Of Intermediate-Felsic Intrusive Rocks And Mafic Microgranular Enclaves From Dongleiwan Deposit In Jiurui Ore District, Jiangxi Province

In order to constrain the petrogenesis of the intermediate-felsic intrusive rocks and mafic microgranular enclaves (MMEs) from the Dongleiwan deposit in Jiurui ore district, Jiangxi Province, a detailed study on zircon U-Pb geochronology, mineral chemistry, whole rock geochemistry and Sr-Nd-Pb-Hf isotopes have been performed. LA-ICP-MS zircon U-Pb dating yields crystallization age of 144.3-148.7 Ma for the felsic rocks and 146.4-147.1 Ma for the MMEs, indicating they are coeval. All the intrusive rocks from the Dongleiwan deposit are metaluminous with high Mg# (42.5-68.0, with an average of 56.0) and high contents of compatible elements such as V, Cr, Co and Ni. The REE characteristics are LREE enriched and lack any significant Eu anomaly. The trace elements are characterized by enrichment of LILE and depletion of HFSE. The MMEs are characterized by microgranular texture, and contain acicular apatites and K-feldspar phenocrysts. The Dongleiwan rock samples have a narrow Sr-Nd isotopic ratio range with initial 87Sr/86Sr ratios from 0.7064 to 0.7079, SNd(t) values from-5.80 to-3.31 and t2DM(Nd) values from 1.2 to 1.4Ga. The samples show initial radiogenic Pb isotopic ratios with values of 206Pb/204Pb (17.3333-18.2600),207Pb/204Pb (15.5135-15.6210) and 208Pb/204Pb (37.4041-38.3954). The zircon Hf isotope analysis shows εHf(t) values of-15.9 to-3.5. These data suggest that the MMEs were probably produced by mixing of mafic and felsic magmas, and the mafic magma was derived from partial melting of delaminated lower crust and may have reacted with surrounded mantle peridotites during its ascent. While the felsic intrusive rocks of this area have been formed by the upwelling of magma which have experienced strong crust-mantle interaction after the delamination of lower crust into the asthenosphere.