We present new 40Ar-39Ar plagioclase crystallization ages from the dykes exposed at the northern slope of the Satpura Mountain range near Betul-Jabalpur-Pachmarhi area, - 800 km NE of the Western Ghats escarpment. Amo...We present new 40Ar-39Ar plagioclase crystallization ages from the dykes exposed at the northern slope of the Satpura Mountain range near Betul-Jabalpur-Pachmarhi area, - 800 km NE of the Western Ghats escarpment. Among the two plateau ages, the first age of 66.56 ± 0.42 Ma from a dyke near Mohpani village represents its crystallization age which is either slightly older or contemporaneous with the nearby Mandla lava flows （63-65 Ma）. We suggest that the Mohpani dyke might be one of the feeders for the surrounding lava flows as these lavas are significantly younger than the majority of the main Deccan lavas of the Western Ghats （66.38-65.54 Ma）. The second age of 56.95 -- 1.08 Ma comes from a younger dyke near Olini village which cuts across the lava flows of the area. The age correlates well with the Mandla lavas which are chemically similar to the uppermost Poladpur, Ambenali and Mahabaleshwar Formation lavas of SW Deccan. Our study shows that the dyke activities occurred in two phases, with the second one representing the terminal stage.展开更多
The giant plagioclase basalts (GPBs) with plagioclase phenocrysts that reach up to 3 cm in length are found near Jabalpur in the northeastern part of the Deccan Volcanic Province (DVP). The thickness of the basalt flo...The giant plagioclase basalts (GPBs) with plagioclase phenocrysts that reach up to 3 cm in length are found near Jabalpur in the northeastern part of the Deccan Volcanic Province (DVP). The thickness of the basalt flow (flow 6) that contains the GPBs is ~ 20 m. Plagioclase phenocysts (An58 - An64) in the GPBs display many features of magma mixing (e.g., resorption, reverse zoning). Of the nine flows in the Jabalpur section, the GPBs (flow 6) with lowest Mg#s (38 - 43) and MgO (4.16 - 5.08 wt%), Ni and Cr abundances are the most evolved compositions. In addition, these GPBs have highest abundances of incompatible elements (TiO2, P2O5, Nb, Zr, Sr and Ba). The GPBs are compositionally similar to the well-studied Mahabaleshwar lavas of the western DVP. This new occurrence of GPBs has implications for existence of local crustal magma chambers, feeders and vents in the northeastern part of the DVP.展开更多
基金Department of Science and Technology,Government of India for financial support to this work(Project Grant No.ESS/16/286/2006)Post-Doctoral,D.S. Kothari Fellowship for financial support
文摘We present new 40Ar-39Ar plagioclase crystallization ages from the dykes exposed at the northern slope of the Satpura Mountain range near Betul-Jabalpur-Pachmarhi area, - 800 km NE of the Western Ghats escarpment. Among the two plateau ages, the first age of 66.56 ± 0.42 Ma from a dyke near Mohpani village represents its crystallization age which is either slightly older or contemporaneous with the nearby Mandla lava flows （63-65 Ma）. We suggest that the Mohpani dyke might be one of the feeders for the surrounding lava flows as these lavas are significantly younger than the majority of the main Deccan lavas of the Western Ghats （66.38-65.54 Ma）. The second age of 56.95 -- 1.08 Ma comes from a younger dyke near Olini village which cuts across the lava flows of the area. The age correlates well with the Mandla lavas which are chemically similar to the uppermost Poladpur, Ambenali and Mahabaleshwar Formation lavas of SW Deccan. Our study shows that the dyke activities occurred in two phases, with the second one representing the terminal stage.
文摘The giant plagioclase basalts (GPBs) with plagioclase phenocrysts that reach up to 3 cm in length are found near Jabalpur in the northeastern part of the Deccan Volcanic Province (DVP). The thickness of the basalt flow (flow 6) that contains the GPBs is ~ 20 m. Plagioclase phenocysts (An58 - An64) in the GPBs display many features of magma mixing (e.g., resorption, reverse zoning). Of the nine flows in the Jabalpur section, the GPBs (flow 6) with lowest Mg#s (38 - 43) and MgO (4.16 - 5.08 wt%), Ni and Cr abundances are the most evolved compositions. In addition, these GPBs have highest abundances of incompatible elements (TiO2, P2O5, Nb, Zr, Sr and Ba). The GPBs are compositionally similar to the well-studied Mahabaleshwar lavas of the western DVP. This new occurrence of GPBs has implications for existence of local crustal magma chambers, feeders and vents in the northeastern part of the DVP.
