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Authors
Affiliations
1 Wadia Institute of Himalayan Geology, DehraDun - 248 001, IN
2 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, JP
3 Department of Geology, Delhi University , Delhi 110 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 70, No 5 (2007), Pagination: 780-786
Abstract
Microthermometric study of fluid inclusions in gabbro from the Nidar ophiolitic sequence revealed that brine rich fluid (34-45 wt% NaC1) at the temperature of more than 400°C were predominant throughout the gabbro High saline inclusion homogenized by halite dissolution at the temperature of 276-400°C. All the moderate to high temperature(l30-390°C) inclusions are liquid and vapour dominated, commonly secondary in origin, majority having seawater-Like salinity( 17- 8 wt% NaC1).
The highly saline fluid was probably derived by phase separation of hydrothermal seawater or an exsolved magmatic aqueous phase at the temperature of 250-412°C. The migration of the Phase-Separated along fractures resulted in segregation of the vapour and brines and preferential entrapment of High-Saline inclusions at depth. These brines may have originated when seawater approached the top of the magma chamber. The subsequent fracturing of the gabbro at the temperature of 130-390°C facilitated the entry of seawater which pervasively altered the gabbro. This hydration processes resulted into the formation of secondary minerals or by mixing with Phase-Separated fluid, resulting in salinities Two-Times higher than that of seawater.
Keywords
Brine, Fluld Inclusions, Nidar Ophiolite, Ladakh.
