Abstract
The Hesar pluton in the northern Urumieh-Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves(MMEs).Whole rock geochemistry,mineral chemistry,zircon U-Pb and Sr-Nd isotopes were measured.It is suggested that the rocks are metaluminous(A/CNK=1.32-1.45),subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures.The host rocks yielded an U-Pb crystallization age of 37.3±0.4 Ma for gabbro-diorite.MMEs have relatively low SiO2 contents(52.9-56.6 wt％)and high Mg#(49.8-58.7),probably reflecting a mantle-derived origin.Chondrite-and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment,HREE and HFSE depletion with slight negative Eu anomalies(Eu/Eu*=0.86-1.03).The host rocks yield(87Sr/86Sr)i ratios of 0.70492-0.70510,positive εNd(t)values of+1.55-+2.06 and TDM2 of 707-736 Ma,which is consistent with the associated mafic microgranular enclaves((87Sr/86Sr)i=0.705014,εNd(t)=+1.75,TDM2=729 Ma).All data suggest magma-mixing for enclave and host rock formation,showing a complete equilibration between mixed-mafic and felsic magmas,followed by rapid diffusion.The TDM1(Nd)and TDM2(Nd)model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantle-derived magmas in a pre-collisional setting of Arabian-Eurasian plates.Clinopyroxene composition indicates a crystallization temperature of～1000℃ and a depth of～9 km.
基金项目
Iran National Science Foundation(INSF)(98012578)
国家自然科学基金(41473033)
国家自然科学基金(41673031)
国家科技期刊平台
NSTL
万方数据