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Absar, Ahsan
- A Preliminary Conceptual Model of Nubra Valley Geothermal System, Ladakh, J & k, India
Authors
1 Geothermal Division, N. R. Geological Survey of India, Lucknow-226020, IN
2 Regional Geology Division, N.E.R. Geological Survey of India, Itanagar -791111, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 37, No 6 (1991), Pagination: 533-545Abstract
The hot spring areas in Nubra valley, Ladakh, J&K located at Changlung, Panamik and Pulthang lie in a 30 km long NNW-SSE trending stretch parallel to and on the left bank of the Nubra river. These hot springs are confined to the Karakoram Granite which is in tectonic contact with the overlying Shyok volcanics.
The local meteoric water, which is Ca-Mg-HCO3 type, alters to Na-HCO3, type before it emerges as hot springs. This chemical alteration of descending local meteoric water may largely be attributed to rock-water interaction and resultant ion-exchange. Application of chemical geothennometries indicates that the chemical mass transfer between rock and water could have taken place at temperatures approaching at the most 200°C.
An attempted conceptual model of the Nubra valley hot spring system suggests that the three thennal areas of Changlung, Panamik and Pulthang are fed from an 'outflow' aligned parallel to the Nubra valley and following the regional hydraulic gradient. The hot water 'outflow' lying at a depth of more than 2 km within the Shyok volcanics is characterised by a decrease in the temperature and dilution of the fluid in the direction of the flow.
The chemistry of the discharging fluid is apparently influenced more by the type of rock reacted (granite or volcanics) than by the residence time and reservoir temperature.
Keywords
Geothennal energy, Geochemistry, Nubra Valley, Ladakh, Jammu and Kashmir.
- Hydrothermal Epidote - An Indicator of Temperature and Fluid Composition
Authors
1 Geothermal Division, Geological Survey of India, Lucknow 226020, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 38, No 6 (1991), Pagination: 625-628Abstract
Epidote tends to form under a rather restricted temperature range, generally above 250° C. The thermal regime inferred by contouring the depths of the first occurrence of epidote in an area may be compared with fluid inclusion temperatures measured in associated quartz and calcite veins to work out temperature fluctuations during a mineral-depositing event. In geothermal areas, however, thermal regime depicted by the epidote-temperature map may also be compared with the present-day temperature distribution. A case-study is presented here from the Ohaaki-Broadlands geothermal field, New Zealand.
As epidote is deposited by high pH, CO2-deficient fluids, its association with minerals forming under relatively Low pH and high CO2 partial pressure conditions, i.e., clay minerals and calcite (only when there is a large scale precipitation) suggests disequilibrium and a possibility of more than one hydrothermal events.