遥感与地理信息系统学报

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A Revisit to Vityaz Transform Fault Area, Central Indian Ridge: IsotopicEvidence of Probable Hydrothermal Activity

Shirodkar PV*, Banerjee R, Xiao YK

Boron and chlorine isotopes have been used as a proxy for tracing the presence of hydrothermal activity in the CIR area. Isotopic compositions of boron (δ¹¹B) and chlorine (δ³⁷Cl) measured from seawater in a 2000 m water column at Vema (VM3: 10o 43.23’S and 66o 36.5’E) and Vityaz, (VT4: 5o 39.55’S and 68o 03.77’E and VT6: 5o 38.83’S and 67o 27.39’E) transform fault areas in the Central Indian Ridge showed significant variations below 300 m water depth at VT6 relative to VT4 and VM3. An appreciable decrease in δ¹¹B (av. 38.9%o) with a concomitant increase in δ³⁷Cl (av. 1.15%o) by ∼1%o below 300 m water depth at VT6, relative to normal seawater value and those at VM3 and VT4, indicated the presence of hydrothermal activity at VT6. This study coupled with earlier studies on serpentinite peridotites from the Vityaz transform fault area showed signatures of low temperature alteration, signifying the presence of hydrothermal activity at around this slow spreading ridge area. The observed features support the possible presence of hydrothermal activity at Vityaz transforms fault area in the Central Indian Ridge.