Petrogenesis and geological significance of Late Mesoproterozoic gabbro in the western Yangtze Block:Constrains from zircon U-Pb-Hf isotopes and whole-rock geochemistry
This study presents systematic analysis of zircon U-Pb-Hf isotopes,whole-rock major and trace ele-ments,and Sr-Nd isotopes of the Jinchuan gabbros,aiming to explore its petrogenesis and geological signifi-cance.The Jinchuan gabbros has Zircon U-Pb age of 1 041.1±1.1 Ma,it has moderate SiO2(50.26％to 51.16％),CaO(6.59％to 7.64％),K2O(1.22％to 1.96％)contents,with high Al2O3(16.38％to 17.15％)and TiO2(2.61％to 2.80％)contents,belonging to low-K tholeiite rocks.These gabbros were en-riched in light rare earth elements and large ionic lithophile elements(e.g.,Ba,Sr),as well as depleted in heavy rare earth elements and high field strength elements(e.g.,Nb,Ta,Th),with weak Eu anomalies(8Eu=0.99 to 1.11).They have negative εNd(t)values(-3.61 to-2.75)and positive zircon εHf(t)(+1.62 to+7.58)contents.These geochemical features indicate the Jinchuan gabbros were originated from the enriched mantle source that metasomatized by middle Mesoproterozoic subduction fluids preserved in the lithosphere mantle.Combined with the coeval A-type granites and intra-plate basaltic magmatism,the Jin-chuan gabbros formed in an intracontinental rift environment under a passive continental margin,representing the magmatic response of the Rodinia supercontinent under local extensional tectonic mechanism during the late Mesoproterozoic.
western Yangtze BlockLate Mesoproterozoicgabbropetrogenesisgeological implications
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