Geochemistry, petrogenesis, zircon U-Pb geochronology and Sr-Nd isotopic composition of Kuh-e-Shah volcanic rocks: Implications for an active continental margin along with eastern Iran during the Paleogene

Abstract

The Kuh-e-Shah complex includes the Paleogene volcano-plutonic belt of the Lut Block, eastern Iran. The volcanic rocks which outcropped in this complex mainly consist of trachy-andesites, andesites, and basaltic-andesites that mineralogically contain plagioclase, pyroxene, hornblende, and minor biotite and olivine. Geochemically, they have features typical of high-K calc-alkaline to shoshsonitic magmas with enrichment in large ion lithophile elements (LILE), and depletion in high field strength elements (HFSE) and heavy rare earth elements (HREE). Chondrite-normalized REE plots show enrichment in light REE (4.9 < LaN/YbN < 11.6), Nb depletion and the slight negative Eu anomalies (Eu/Eu* = 0.80–0.99). Tectonic discrimination diagrams are used to infer a volcanic arc setting related to a continental subduction zone. It is concluded that the studied volcanic rocks have resulted from FC of a parental magma which formed by partial melting of the subducted oceanic crust and the overlying mantle wedge with spinel-lherzolite composition. Zircon Usingle bondPb dating indicates an age of 38.6 to 38.9 Ma for volcanic rocks (Middle Eocene, Bartonian). Initial 87Sr/86Sr and 143Nd/144Nd ratios (0.704350–0.704820 and 0.512619–0.512779, resp.), are compatible with parental melts formation in a subduction mantle wedge. The ɛNdi values (+0.60 to +3.73) are in the range of mantle-derived melts. We suggest that volcanic rocks of the Lut Block are part of the Paleogene volcanism resulted from the Sistan oceanic crust subduction under the Lut Block during the Cretaceous.