The paleozoic Jalal Abad mafic complex (Central Iran): Implication for the petrogenesis

Abstract

The Jalal Abad magmatic rocks are located at the southeastern edge of the Kashmar-Kerman tectonic zone, which includes Cadomian magmatic rocks and sedimentary strata intruded by several Silurian alkaline plutons and associated dikes. They have typical alkaline kaersutite and alkaline to per-alkaline pyroxene and are characterized geochemically by enrichment in LREE, Nb and Ta, and high concentrations of incompatible trace elements, demonstrating alkaline features with typical ocean island basalt signatures. Chondrite-normalized REE and multi-element spider diagrams along with High 206Pb/204Pb ratios (18.46–19.83) for the Jalal Abad gabbro, diorite, and dibasic dikes indicate involvement of an OIB-like source during the formation of these rocks. Modeling of bulk–rock trace elements and Sr–Nd isotopes suggest that magmas were generated by a pair of HIMU-EM1- like mantle source, consistent with a plume mantle origin in a within-plate rift zone. The melting took place in garnet stability field and the fractional crystallization played a major role in magmatic evolution of the mantle-derived parental magma. The Jalal Abad mafic rocks have U–Pb zircon ages of 425.5 ± 8.6 Ma and along with other Ordovician to Silurian rocks in different parts of the Iranian plate are related to the extensional tectonic regime responsible for the rifting of Cadomian fragments from northern Gondwana and the opening of Paleo-Tethys. Our findings indicate that the rifting and seafloor spreading of Paleo-Tethys and the formation of its oceanic crust were intensely influenced by a mantle plume activity in the early Paleozoic.