Neodymium, Hf, Os, and U Pb isotope study of Permian Komatiites from Mashhad, Iran

We present new Sm Nd, Lu Hf, Re Os, and U Pb zircon isotopic and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance data for komatiites from the Mashhad–Fariman region in Iran, and use these data to constrain their petrogenesis and the compositions of their mantle source. A new, robust Re Os isochron age of 270.4 ± 2.1 Ma (Permian) confirms their status as one of only two occurrences of post-Precambrian komatiites with olivine spinifex textures. The Re Os emplacement age is identical to the U Pb zircon age of 274 ± 4 Ma obtained in this study for the gabbro layer from a differentiated komatiite lava flow. Based on their lithophile trace element systematics, Mobasheri et al. (2025) divided the komatiites into two groups: D-type (light REE-depleted) and E-type (light REE-enriched). The initial εNd (+6.4 to +11.1) and εHf (+12.1 to +18.2) values are all positive in both groups. The D-type samples plot on the terrestrial DMM (depleted MORB mantle) evolution curve, whereas the E-type samples are isotopically less depleted and plot below the DMM curve. Combined, these observations suggest long-term heterogeneity in the trace element composition of the Mashhad komatiite mantle source. The initial γ 187 Os value of −0.92 ± 0.05 derived from the Re Os isochron is within the range of Os isotopic compositions of chondritic meteorites at the time of the Mashhad komatiite magma emplacement. This indicates derivation of these magmas from the mantle source that evolved with a time-integrated near-chondritic Re/Os ratio, further confirming the decoupling of the Nd Hf and Os isotope systematics reported for many Archean komatiites. The HSE concentrations and CI chondrite-normalized HSE patterns of the Mashhad komatiites are broadly similar to those of late Archean komatiites. Collectively, the data support formation of the Mashhad komatiites by moderate degrees of partial melting in a heterogenous mantle plume containing components with variable extents of long-term depletion in incompatible lithophile trace elements. • First Sm Nd, Lu Hf, Re Os, U Pb zircon, and HSE dataset for komatiites Iran. • Re Os isochron age of 270.4 ± 2.1 Ma, confirms status as a rare vpost-Precambrian komatiite. • Variable Nd and Hf isotopic composition indicate long-term mantle source heterogeneity. • Magma formed by moderate degrees of partial melting within a heterogeneous mantle plume.