Petrochemical Characteristics and Timing of Middle Eocene Granitic Magmatism in Kooh-Shah, Lut Block, Eastern Iran

The Kooh‐Shah region located in a Tertiary volcanic–plutonic belt of the Lut Block in eastern Iran comprises several subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, which have intruded into volcanic rocks. The Kooh‐Shah granitoid rocks are characterized by enrichment in large ion‐lithophile elements (LILE: e.g. Sr, Ba, Rb) and depletion in high field‐strength elements (HFSE: e.g. Nb, Ta, Ti). The chondrite‐normalized REE patterns are characterized by moderate LREE enrichment (La/Yb)_N=6.01–10.01, medium‐heavy REE enrichment, and absence of Eu anomalies. The Kooh‐Shah intrusive rocks are metaluminous, shoshonitic with calc‐alkaline affinity and high values of magnetic susceptibility, and classified as the magnetite‐series of oxidant I‐type granitoids. The age of Kooh‐Shah granitoid rocks based on zircon U–Pb age dating is 39.7±0.7 Ma (=Middle Eocene) and the ranges of their initial ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios are from 0.704812 to 0.704920 and 0.512579 to 0.512644, respectively, when recalculated to an age of 39 Ma. The initial cNd isotope values for the Kooh‐Shah intrusive rocks range from ?0.18 to 1.09. This geochemical data indicates that the Kooh‐Shah granitoid rocks formed from depleted mantle in an island arc setting. The geochemical signature of the studied granitoid rocks represents a characteristic guide for future exploration of copper‐gold porphyry‐type deposits in the Lut block.