Writers : R. Arjmandzadeh; M.H. Karimpour; S.A. Mazaheri; J.F. Santos; J.M. Medina; .M. Homam
Refference : 1st Symposium of Iranian Society of Economic Geology
Publishing Year : 1389

Abstract :

The Dehsalm and Chah Shaljami porphyritic granitoids belong to the volcanic-plutonic belt within the Lut Block, in central eastern Iran, and display geochemical features of high-K calcalkaline to shoshonitic volcanic arc granites. Primitive mantle normalized trace element spider diagrams show strong enrichment in LILE, such as Rb, Ba, and Cs, and depletion in some HFSE, e.g. Nb, Ti, Y and HREE. Chondrite normalized plots show a very marked REE fractionation, with high values of LREE/HREE ratios. Despite their shoshonitic affinity, these rocks also display some geochemical features similar to those of adakites, as revealed by plots on the Sr/Y–Y and La/Yb–Yb diagrams. Sr and Nd isotope compositions together with major and trace element geochemistry suggest that the parental magmas resulted from melting of a metasomatized mantle source mantle, and that garnet behaved as a residual phase, whilst phlogopite underwent decomposition. Contamination by the crustal materials seems to have played only a minor role. As a whole, the petrological, geochemical and isotopic evidence agrees with a geodynamic setting characterized by a subduction zone operating under the Lut block, in the Tertiary.