In situ determination of U-Pb ages and Sr-Nd-Hf isotopic constraints on the petrogenesis of the Phalaborwa carbonatite Complex,South Africa
作者单位：Department of GeologyLakehead UniversityOntarioCanada P7B 5EI Council for GeoscienceLimpopo UnitP.O.Box 620Polokwane 0700South Africa Department of Earth System ScienceFaculty of ScienceFukuoka UniversityJonanFukuoka 814-0180Japan
会议名称：《中国科学院地质与地球物理研究所第11届（2011年度）学术年会》
会议日期：2012年
学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学]
基 金：supported by the Natural Science Foundation of China(Grant 49634019)
关 键 词：U-Pb ages Zircon and baddeleyite Sr-Nd-Hf isotopes Carbonatite Phalaborwa
摘 要：The Phalaborwa carbonatite Complex,situated in the northeastern part of South Africa,is characterized by copper and zirconium mineralization,and is composed principally of pyroxenites,phoscorite and carbonatite (banded and transgressive).The complex is transected by mafic dykes,and is geographically associated with a satellite syenite and minor granite *** and baddeleyite U-Pb isotopic age determinations using CAMECA 1280 secondary ion mass spectrometry have shown that the outer pegmatitic pyroxenite at the Loolekop pipe was emplaced at 2060±4 Ma,and the main phoscorite at 2062±2 *** ages are identical to those of 2060±2 and 2060±1 Ma for the banded and transgressive carbonatites,*** satellite syenite,which forms plug-like bodies outside of the border of the main complex,and the later mafic dyke have similar emplacement ages of 2068±17 and 2062±53 Ma,indicating that these intrusions were apparently near-synchronously *** contrast to other carbonatites,the Phalaborwa Complex is characterized by high initial Sr and low initial Nd and Hf isotopic *** situ isotopic analyses of apatite, calcite,zircon and baddeleyite indicate that the primary magma was derived from an enriched mantle. As the complex was emplaced slightly earlier at～2060 Ma than the nearby mafic phase of the Bushveld Complex (-2055 Ma),it is proposed that the Phalaborwa carbonatite magmatism was triggered by the same mantle plume activity,which partially melted the overlying lithospheric *** contribution also highlights that isotopic studies used to constrain the genesis of ancient igneous complexes should concentrate on minerals with low parent/daughter elemental ratios,such as apatite and calcite for Sr isotopes,and zircon and baddeleyite for Hf isotopes.