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Ray, Jyotiranjan S.
- A Fluid-Rock Interaction Model for Carbon and Oxygen Isotopic Variations in Altered Carbonatites
Abstract Views :199 |
PDF Views:3
Authors
Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
1 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 54, No 2 (1999), Pagination: 179-186Abstract
A fluid-rock interaction model for treating the stable carbon and oxygen isotopic variations in altered carbonatites is presented and illustrated with an example using data from the ferrocarbonatites of Amba Dongar, Gujarat. The Amba Dongar ferrocarbonatites appear to have been altered by a fluid of magmatic origin at 100 to 200°C contrary to an earlier suggestion of meteoric groundwater alteration at ∼50°C.Keywords
Isotope Geology, Ferrocarbonatite, Fluorite, Fluid-Rock Interaction Model, Carbon and Oxygen Isotopes, Amba Dongar, Gujarat.- Origin of the Mile Tilek Tuff, South Andaman: Evidence from 40Ar-39Ar Chronology and Geochemistry
Abstract Views :232 |
PDF Views:83
Authors
Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
2 Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
2 Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN
Source
Current Science, Vol 108, No 2 (2015), Pagination: 205-210Abstract
The Mile Tilek Tuff is one of several consolidated volcanic ash deposits in the Andaman and Nicobar Islands that has preserved evidence of a large-scale volcanic eruption in Southeast Asia. Assumed to be of Mio-Pliocene age (~25-2 Ma), the tuff was thought to have been generated by the Andaman-Indonesia volcanic arc. Little was known about its source volcano because of absence of critical isotope data. To provide accurate age information and determine its source, we dated the tuff by 40Ar-39Ar method and measured its trace element contents and Sr-Nd isotopic ratios. The 40Ar-39Ar plateau age for the whole rock is 0.73 ± 0.16 (2σ) Ma, which suggests that the tuff got deposited much later than previously believed. Chemically, the tuff possesses typical characteristics of subduction zone magmatism. Its Sr-Nd isotopic compositions (87Sr/86Sr = 0.7073 and εNd ≤ 0.9) suggest substantial continental crustal contamination of its source magma, which points to a source volcano in Sumatra. Based on available age information on large-scale volcanic eruptions in Indonesia, we speculate that the Ranau volcano in south Sumatra could have been the source of the Mile Tilek Tuff.Keywords
40Ar–39Ar Dating, Geochemical Fingerprinting, Mile Tilek Tuff, Sumatra.- Stable Carbon and Oxygen Isotope Analysis of Natural Calcite and Dolomite Mixtures using Selective Acid Extraction
Abstract Views :178 |
PDF Views:2
Authors
Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380009, IN
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 52, No 3 (1998), Pagination: 323-332Abstract
Accurate analysis of coexisting calcite and dolomite for δ13C and δ18O is generally hindered by the difficulty in the physical separation of these minerals. The difference in the reaction rates of calcite and dolomite with phosphoric acid, has been used to chemically separate these carbonates. Previously established procedures are only suitable for samples containing 1:1 calcite-dolomite pairs. However, these are sometimes tedious and time-consuming. Using mixtures of calcite and dolomite, two different selective acid extraction procedures (for reactions at 25°C), one for calcite-rich and the other for dolomite-rich carbonates, have been developed. Reduction of grain size (to 37μm - 45μm) increased the reaction rate and hence decreased the total reaction time to a reasonable interval (≤72 hours for dolomite). Applying these procedures, δ13C and δ18O of calcite and dolomite/ankerite of carbonatites from Amba Dongar and Sung Valley carbonatite complexes of India were measured and their temperatures of crystallization determined. Accurate isotopic compositions of individual carbonates of calcite-dolomite mixtures can be determined for geological interpretations by these procedures.Keywords
Stable Isotopes, Carbonate Mixtures, CO2 Extraction Technique, Calcite, Dolomite, Ankerite, Carbonatite, Amba Dongar, Sung Valley.- Early 2017 Activity of the Barren Island Volcano:Facts Versus Hype
Abstract Views :326 |
PDF Views:82
Authors
Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
1 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Current Science, Vol 113, No 09 (2017), Pagination: 1657-1659Abstract
Barren Island is the northernmost active stratovolcano of the Sunda Volcanic Arc system in the northeastern Indian Ocean. It is the only active volcano in the Indian territory. The arc is a result of subduction of the Indian plate beneath the Burma plate, a sliver of the Eurasian plate. This subduction zone is a southward extension of the Himalayan convergent boundary that takes a turn at the Eastern Syntaxial Bend. Located ~135 km northeast of Port Blair (12°70'N/93°51'E), the Barren Island volcano covers a subaerial area of ~8 km.References
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- Bandopadhyay, P. C., Ghosh, B. and Limonta, M., Episodes, 2014, 37, 192–205.
- Sheth, H. C., Ray, J. S., Bhutani, R., Kumar, A. and Smitha, R. S., Bull. Volcanol., 2009, 71, 1021–1039.
- Sheth, H. C., Ray, J. S., Bhtani, R., Kumar, A. and Awasthi, N., Curr. Sci., 2010, 98, 620–626.
- Ray, J. S., Pande, K. and Bhutani, R., Bull. Volcanol., 2015, 77, 57; doi: 10.10.1007/s00445-015-0944-9.
- Awasthi, N. et al., Bull. Volcanol., 2010, 72, 1131–1136.
- Awasthi, N., Ray, J. S., Singh, A. K., Band, S. T. and Rai, V. K., Geochem. Geophys. Geosyst., 2014, 15, 3890–3906.
- Koshy, J., Why did Barren Island volcano erupt again? The Hindu, 26 February 2017.
- Arora, M., India’s Barren Island volcano active again. The CNN, 21 February 2017.
- Sayed, N., Barren Island volcano erupts again in Andaman Sea. The Times of India, 17 February 2017.
- Volvoikar, H., NIO scientists observe volcanic eruption on Barren Island in Andaman Sea, 19 February 2017; http://indiatoday.intoday.in
- Sheth, H. C., Ray, J. S., Kumar, A., Bhutani, R. and Awasthi, N., J. Volcanol. Geotherm. Res., 2011, 202, 73–82.
- Principles of Radiometric Dating
Abstract Views :377 |
PDF Views:82
Authors
Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
Source
Current Science, Vol 114, No 02 (2018), Pagination: 397-398Abstract
Even after more than 100 years of the initial discovery of isotopes, we are yet to fully utilize their potential in science and technology. The unique properties of isotopes of elements covering the entire periodic table have wide-ranging applications. The modern earth and planetary sciences owe a lot to such exploits for understanding of the fundamental aspects of evolution of the solar system and planetary interiors. Isotopes have remained the most advanced tools in determining the timescales of various events that shaped the solar system and understanding the nature of processes that occur in it. Isotopes are either stable or radioactive. Stable isotopes are powerful tracers of geochemical processes, whereas radioactive isotopes and their products (radiogenic isotopes) are the basis of geochronology or radiometric dating.- Rengaswamy Ramesh (1956–2018)
Abstract Views :355 |
PDF Views:71
Authors
Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
Source
Current Science, Vol 114, No 10 (2018), Pagination: 2199-2200Abstract
Rengaswamy Ramesh was a man of extraordinary scientific latitude with countless important contributions to stable isotope geochemistry, palaeoclimatology, oceanography, biogeochemistry and solid earth studies. He was mentor to a long list of Master’s and Ph D students, postdoctoral fellows and university teachers, and had inspired many young minds to take up science as a career. He was instrumental in shaping stable isotope research activities in numerous universities and institutions in India. He was extremely intelligent and a scholar in the true sense.- Tracking Indian Monsoon Variability from Changes in Sediment Provenance
Abstract Views :225 |
PDF Views:68
Authors
Affiliations
1 Department of Earth and Planetary Sciences, Prof. Rajendra Singh (Rajju Bhaiya) Institute of Physical Sciences for Study and Research, VBS Purvanchal University, Jaunpur 222 003, IN
2 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
1 Department of Earth and Planetary Sciences, Prof. Rajendra Singh (Rajju Bhaiya) Institute of Physical Sciences for Study and Research, VBS Purvanchal University, Jaunpur 222 003, IN
2 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN