In the present work, we studied zircons from the less foliated granites of the Chail Group, which form a thrust sheet of the Lesser Himalayan Sequences, Garhwal region. Compositionally, these granites are S–type, formed in a collisional tectonic setting. Zircons possess an internal structure, mineral inclusions, and geochemical characteristics typical of magmatic origin. The U–Th–Pb geochronology and geochemistry were assessed using the laser ablation multi–collector inductively coupled plasma spectrometry (LA–ICP–MS) technique. U–Th–Pb isotope dating of zircons from two different samples revealed their age, estimated from the upper intersection of the discordia, to be 1845 ± 19 Ma. Zircons from one sample contained inherited cores belonging to three age groups: Paleoarchean (3.52 Ga), Neoarchean (2.78 Ga and 2.62 Ga), and Paleoproterozoic (2.1 Ga). Zircons with ages of 3.52, 2.62, and 2.1 Ga were interpreted as magmatic based on their geochemical characteristics. The 2.78 Ga core was interpreted as metamorphic. The observed inheritance is consistent with the melting of sedimentary rocks. The inherited zircons could have originated from Aravalli and Bundelkhand Craton and Paleoproterozoic Aravalli Fold Belt rocks. This confirms that the studied granites are S–type and could have been formed in a collisional environment at 1.85 Ga on the western flank of the Columbia Supercontinent.
The spatial and temporal characteristics of droughts were investigated to provide a framework for agriculture practices, engineering facilities and sustainable water resources management in the Tel river basin which is about 2756 km 2 and lies between 19817 0 and 20800 0 N and 82830 0 and 82859 0 E in Kalahandi district of Odisha, India. Using the Standardized Precipitation Index (SPI) as an indicator of drought severity for the period from 1965 to 2008, the characteristics of droughts were examined. The multiple-time scaled SPI values were evaluated for May-October months and point-wise indices were interpolated over the whole area using spatial interpolation technique in Arc GIS 9.2, in order to obtain areal extension of the drought severity. The results indicated that a dramatic and widespread drought event was recorded in the year 2002 at most of the stations and drought categories. However, regardless of the drought severity, an extraordinary dryness was experienced in the years 1966, 1972, 1979, 1987 and 2002 in the entire study area. It was observed that 10 years were successively dry during May at Jayapatna station from 1999 to 2008 in the 6-month drought category. The highest SPI value of 73.06 was observed in July 2002 in the Dharamgarh station in the 9-month drought category. The overall outcome of this study demonstrates that severe and extreme droughts were experienced from time to time across the study area leading to unfavourable results on agricultural practices and water resources in the area.
This study presents petrological and geochemical data on Neoarchean granitoids from the northern and central parts of the Bundelkhand Craton to discuss its crustal evolution and tectonic history. The study deals with two granitoid suites, i.e. tonalites–trondhjemites–granodiorites (TTG) and sanukitoids. TTGs are characterized by high SiO2, Na2O and mostly low to moderate Mg#. They display enrichment in light rare earth elements, low to moderately fractionated heavy rare earth elements (HREE) and low Sr/Y ratios, suggesting their high-HREE character or low-pressure origin from melting of a mafic protolith. The sanukitoid samples show relatively low SiO2, high K2O (2.1–4.6 wt%), Pb, Sr and Ba, and moderate to low Mg#, Cr, Ni. These granitoids probably generated from partial melting of hydrous mafic rocks followed by interaction with a mantle peridotite. Geochemical characteristics, tectonic discrimination using ratios like (Ce/Pb)PM, (La/Nb)PM and (Th/Nb)PM and regional rock association suggest that the Neoarchean TTGs and sanukitoids were emplaced in a subduction setting. Combining the existing knowledge base, a schematic model for generation and evolution of crust from Paleoarchean to Neoarchean has been proposed for the Bundelkhand Craton.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.