Evidences for incipient hydrothermal event(s) in the Central Indian Basin: A review

The Central Indian Basin (CIB, 10 degrees-19 degrees S) encompasses morphotectonic features such as seamounts, abyssal hills, faults, fracture zones and lineations and basic to silicic volcanics that were derived from different sources. Instances of incipient hydrothermal event (s) occurred as evident from: (1) spilites that probably formed due to low-temperature hydrothermal action on the precursory basalts, (2) slabs and fragments of zeolitites which are the consequent products of palagonitization of the basaltic glasses, (3) chemical variations in the ferromanganese crusts, and (4) abundance of volcanogenic-hydrothermal material (vhm) that includes ochrous sediments and magnetite spherules. The vhm suggests its origin by interaction of Fe-rich hydrothermal solutions with surrounding sediments. The CIB spherules occur in sediments of similar to 10 ka and similar to 425 to 650 ka age and are orders of magnitude younger than the 50 to 60 Ma age of the basin. Incidentally, to the north of the basin at ODP Site 717-719 (1 degrees S/81 degrees E) hydrothermal precipitates of inorganic calcite and deposition of sulphide minerals (similar to 7.5 to 9 Ma and 0.5 Ma) occur as a result of the on-going intraplate deformation. This paper reviews the above evidences that possibly indicate episodes of localized hydrothermal events in the CIB.