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Sachan, Himanshu K.
- Fluid Inclusion Evidence for Amphibolite-Granulite Facies Transitional Metamorphism in Delhi Supergroup of Rocks
Authors
1 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 43, No 5 (1994), Pagination: 529-537Abstract
The Deri-Ambaji massive sulphide deposits are associated with the Precambrian rocks of Delhi Supergroup. Detailed fluid inclusion studies of quartz associated with the host rock of sulphide deposit as well as with ores show high density CO2 (1.05-1.08 g/cm3) as the dominant fluid phase and C02-H20 (0.94-0.98 g/cm3) and minor H2O inclusions are also present. The isochore for the high density fluid inclusions indicate the pressure limit of 7.5 Kbars, at the upper temperature limit 800°C, which is in accordance with the estimation by mineralogic thermobarometery. The lower P-T limit is of 2.5 Kbar at 500°C, which indicates that the transition of upper amphibolite to granulite facies of metamorphism has taken place in the area. The P-T path delineated from combined mineralogical and fluid data is characterised by T-convex nature, which is indicative of isothermal crustal uplift, probably promoted by extensional tectonics.Keywords
Fluid Inclusions, Thermobarometry, Metamorphism, Deri-Ambaji, Delhi Supergroup, Gujarat, Rajasthan.- Fluid Inclusion Study of the Neoproterozoic Nagthat Siliciclastic Sediments, NW Kumaun Lesser Himalaya: Implications to Quartz Cementation History
Authors
1 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 47, No 1 (1996), Pagination: 107-114Abstract
The fluid inclusion study in quartz overgrowth in the siliciclastics of Neoproterozoic Nagthat Formation reveals that the quartz cementation took place in the range of 80°C to 130°C with a salinity range of 0.82 to 9.18 wt. % NaCl. The microthermometric data, combined with petrographic and geologic evidences pennitted to constrain the nature of cementing fluids and source of cement. The silica for quartz cementation was derived partly from both the internal source (quartz and feldspar dissolution) and external source (pore fluids). It can be further suggested that the quartz cementation in the lower stratigraphic level (near the Chandpur Formation) is mainly by marine water while in the upper stratigraphic level (near the Blaini Formation), meteoric water has played an important role for the same.Keywords
Fluid Inclusion, Neoproterozoic, Nagthat Formation, Lesser Himalaya, Uttar Pradesh.- Brine-Rich Hydrothermal Fluid Circulation in the Upper Level of Nidar Ophiolite Sequence, Ladakh:Evidences from Fluid Inclusions
Authors
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: 780-786Abstract
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.- Geochemical Characterisation of the Neoproterozoic Nagthat Siliciclastics, NW Kumaun Lesser Himalaya: Implications for Source Rock Assessment
Authors
1 Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road, Dehra Dun - 248 001, IN