Trace element abundances in clinopyroxene and whole-rock geochemistry:Implications for source characteristics of Xiangshanzhong mafic-ultramafic intrusion in the Central Asian Orogenic Belt,NW China

摘要

The Xiangshanzhong mafic-ultramafic intrusion is one of the important Ni-Cu sulfide-bearing mafic-ultramafic intrusions in eastern Tianshan located in the southern margin of the Central Asian Orogenic Belt (CAOB),NW China.The complex consists of diorite,gabbro,norite,lherzolite,harzburgite,and olivine websterite.Obviously pyroxene cumulate structure,high Mg,low Cr,Na,and Ti contents,consistent low trace element contents and relatively high crystallization temperature of clinopyroxenes,all imply that the cumulated phase olivine clinopyroxenite sample was the earliest crystal phase in Xiangshanzhong mafic-ultramafic complex.AlⅣ and TiO2 compositions,LREE enrichment,Nb,Ta,Zr and Hf primitive mantle-normalized negative anomalies of this clinopyroxene indicate that the characteristics of parental magma should be tholeiitic magma from the spinel peridotite mantle source.