Exploring Boron Isotopes In Indian Thermal Springs
Geochemical analysis gives us a clear idea about the various chemical elements present in the rocks and soils through which the water flows and acquires certain elements from the rocks and in some cases precipitates certain elements.
Geochemical interaction takes place at certain temperatures. If the temperature of a reaction is high, then more elements enter into the geothermal waters. A very good example is the exchange of oxygen isotope between geothermal fluids and the rocks. Rocks give away oxygen isotopes to the geothermal fluids only at temperatures above 200°C.
An investigation on boron isotopes was carried out for the first time on the Indian thermal springs. Isotopes of boron (10B and 11B) give information about the geothermal reservoir that is hosting the geothermal fluids. In the present case, even though the geothermal springs are flowing through the Deccan basalts, the isotopes indicate that the geothermal waters are interacting with the granitic rocks below the Deccan basalts and also indicate the presence of marginal sedimentary basins filled with ancient sediments along the western coast of Maharashtra.
The geothermal fluids ascend to the surface through interlinked faults and fractures in the subsurface strata. The geothermal springs along the western coast of Maharashtra flow along liner faults, that lie parallel to the west coast and were formed about 65 million years ago, the time when all of western India experienced intense volcanic activity. There are more than two faults running the full length of the west coast and hence is termed as the west coast faults.
Along with the Boron Isotopes, REE’s were also studied for the first time in Indian thermal waters. These elements are useful tools in tracing the evolution of the geothermal fluids in terms of interaction with the rocks through which they ascend and the temperatures of interaction.
This study indicates the existence of a medium enthalpy geothermal reservoir along the West coast of Maharashtra.
From a geothermal direct use perspective, west coast geothermal provinces serve as a ready platform for developing natural greenhouses (in line with similar systems currently in place at Turkey, Russia, Hungary, China, and Italy), dehydration units for perishable food products (widely used in Middle East and Schengen region), aquaculture centres and Natural health spas (Wairaki New Zealand, Blue Lagoon Iceland), thus promoting the growth of secondary and tertiary industries along with its associated direct and indirect job. In addition to these uses, the heat from the earth can also be utilized for space cooling and space heating.
The current investigation indicates that the geothermal development in the state of Maharashtra, India, should be divided into short, mid, and long-term developmental plans. The short-term development plans should be focused on direct uses (space heating and cooling, greenhouses, dehydration), which shall promote the concept of geothermal energy to the masses as well as creating small-scale sustainable small to medium enterprise businesses. Mid and long-term development plan should be centered around the use of geothermal energy for generating cheap, clean and base power generation systems, beginning with the drilling of ten to fifteen deep exploration along the identified locations.
These findings are described in the article entitled Understanding the evolution of thermal fluids along the western continental margin of India using geochemical and boron isotope signatures, recently published in the journal Geothermics. This work was conducted by Trupti Chandrasekhar from the Indian Institute of Technology Bombay, A. Minissale from C.N.R. Institute of Geosciences and Earth Resources, O. Vaselli from the University of Florence, D. Chandrasekharam from the Indian Institute of Technology Hyderabad, and H.K. Singh from the Rajiv Gandhi Institute of Petroleum Technology.