Early Paleozoic basement diorite of arc-magmatism from Kutch basin, Western India

In this study, we report for the first time an Early Palaeozoic basement diorite from the drilled well Nirona-A in the Banni Half-Graben of the Kutch basin, western India. The ⁴⁰Ar–³⁹Ar dates provided a plateau age of 441.84 ± 2.66 Ma and another pseudo plateau of 441.28 ± 5.82 to 388.08 ± 16.65 Ma for the basement diorite. These ages constrain the basement formation age to the Late Ordovician-Early Silurian period. The obtained basement ages are correlatable with the later part of Cambro-Ordovician alkaline magmatism that has been reported from the Huqf area in Central Oman, whereas their lithological and petrographic correlativity with basement diorites occurring in the Dinsi Body of Nagar Parkar igneous complex in Pakistan can also be envisaged. The geochemical studies characterized the diorite with enrichment of LILE (Rb, Ba, and K) and LREE (La, Ce, Nd), strong depletion of HFSE (Nb, Sr, P, and Ti), along with weakly negative Eu anomalies. The geochemical signatures indicate their petrogenetic affiliation with mantle-derived magmas, as well as their tectonic setting to be arc-related, having post-collisional continental-arc type affinity. The ~ 440 Ma basement of Kutch, therefore, appears to represent the later thermal event associated with the reworked Neoproterozoic subduction-related suite from Greater India’s northwest edge, which has implications for Gondwana assembly in the northwest Indian subcontinent.