Evidences for seawater-rock hydrothermal interaction in the serpentinites from Northern Central Indian Ridge

Abstract

Serpentinites and serpentinized harzburgites were collected from a ridge-transform intersection at 6 ddgrees 39 minutes S-68 degrees 19 minutes E from the Northern Central Indian Ridge. The degree of serpentinization is extensive and varies from 90 to 100%. Olivine and orthopyroxene are largely pseudomorphed to lizardite-chrysotile ‘mesh’ and ‘bastite’ respectively. Numerous serpentine vein network associated with clusters of magnetite are also present. On the basis of mineralogical paragenesis, mineral chemistry and bulk rock analyses, we infer that the present serpentinites might have formed due to the interaction of harzburgites and seawater at a low temperature. Additionally, positive Eu anomaly, higher La/Sm and low Nb/La ratios suggest substantial hydrothermal input during the onset of serpentinization