Petrogenesis and mineralization of intermediate-basic intrusive rocks in the Late Mesozoic in the Tongling area,Anhui:Evidence from apatite mineralogy and geochemistry
Pyroxene diorite is an important type of Late Mesozoic intrusive rock in the Tongling area of Anhui,closely associated with copper and polymetallic mineralization.This study focuses on the pyroxene diorite of the Baimangshan and Shujiadian plutons as research subjects,emphasizing the mineralogical and geochemical studies of apatite,to explore the genesis of intermediate-basic intrusive rocks and their relationship with mineralization.The results show that the apatite particles are highly enriched in REE,with a clear differentiation between LREE and HREE,a weak to moderate Eu negative anomaly,enrichment in HFSE such as Th and U,and depletion in Ta,Nb,Ti,Zr,Hf,and LILE like Rb,Ba,Sr.The characteristics of REE and trace elements indicate that the materials of their host rocks are mixed source of crust and mantle.Petrographic features show that the apatite particles have two categories with different crystal morphologies,occurrences and microstructures:one is long columnar,inclusion phase,homogeneous structure,and another is short columnar,intercrystalline phase,core-rim/banded structure.Their elemental geochemical characteristics show significant differences,these features indicate that the host rocks have undergone a complex process consisting of crustal-derived felsic magma condensation and crystallization → high-temperature mantle-derived mafic magma injection and dissolution of already crystallized minerals → mixed magma emplacement and crystallization.The core-rim/zonal structure of apatite shows fluctuating SO3 and Cl contents from the core to the rim,indicating the curtain-style injection of mafic magma,which triggers the rise and emplacement of mixed magmas conducive to fluid exsolution and hydrothermal mineralization.The high content of halogen elements(F,Cl)and SO3 in apatite provides evidence of a subduction zone environment,indicating that the mafic end-member arc magmas originate from the mantle wedge metasomatized by fluids released from the subducting slab,the curtain-style injection of mafic magma is conducive to fluid exsolution and hydrothermal mineralization.
Pyroxene dioriteIntermediate-mafic intrusive rockMineralogy and geochemistry of apatiteLate MesozoicTongling area of Anhui Province
万方数据
维普
