Volcanogenic-hydrothermal iron-rich materials from the southern part of the Central Indian Ocean Basin

We report the occurrences of magnetite-rich spherules, Ti-rich particles an d possibly nontronite recovered at 19 degrees S and 76 degrees E from the p elagic clay in the Central Indian Ocean Basin (CIOB). It is proposed that t he magnetite spherules were formed as a result of volcanic activity in this part of the CIOB, while the presence of nontronite suggests localized hydr othermal activity. The magnetic spherules and the associated materials are compared with similar occurrences 555 km to the north in the vicinity of th e 76 degrees 30'E fracture zone. Considering radiolarian age dating of the sediment, the age of the volcano-hydrothermal episode responsible for the f ormation of these materials seems to be between 425 and 650 ka. It is infer red that there could have been widespread local volcanism in the CIOB. (C) 1999 Elsevier Science B.V. All rights reserved.