Characteristics and genesis of phillipsite grains in a sediment core from the Central Indian ocean basin

Present study is the phillipsite grains present in a siliceous sediment core (water depth 5100 m) recovered near a seamount from the Central Indian Ocean Basin (CIOB). Phillipsite occurs as single grains, cruciform crystals and as simple to complex twinned forms. Chemical composition (av SiO2 56 wt%, Al2O3 19 wt%, Na2O 3 wt%, K2O 9 wt%) and the Si/Al ratio (av 2.58) of the phillipsite are comparable with those reported from the Pacific Ocean. The formation of phillipsite depends on parameters such as the availability and type of precursors, the pH-Eh conditions, formation time and temperature, and type of processes. Low temperature halmyrolysis of precursors such as altered basaltic fragments and palagonite resulted in intra-sedimentary diagenesis and formation of abundant phillipsite grains