Geochemical investigations of weathered amphibolite enclave from southern Bundelkhand region, central India

The present study investigates the chemical weathering characteristics of an amphibolite enclave within granite from Bundelkhand region, central India. The mineral composition varies from core to rind with depletion of hornblende and plagioclase and enrichment of clay minerals and oxyhydroxides. The chemical index of weathering (CIA) indicates an incipient stage of weathering, within the enclave (CIA = 52.22 – 54.74). A-CN-K (Al2O3-CaO + Na2O-K2O) plot reveal samples plot along the A-CN line, indicating the removal of Ca and Na, due to plagioclase destruction. The weathering trend progresses towards the formation of smectite, a significant component within the clay composition of the enclave. The results of mass balance calculation reveal a substantial mass decrease of approximately 50% to 82% in the amphibolite. Furthermore, major oxides in the amphibolite enclave, experience significant losses. Trace elements display general losses in the enclave. This study provides valuable insights into the complex dynamics of elemental behavior during weathering by shedding light on the processes shaping the geochemical evolution of these rock types and their response to weathering conditions.