The Precambrian shields and associated suture zones of the globe preserve important records of continental growth and destruction, the formation and closure of ocean basins, and the early evolution of the Earth in ter...The Precambrian shields and associated suture zones of the globe preserve important records of continental growth and destruction, the formation and closure of ocean basins, and the early evolution of the Earth in terms of tectonics, resources, and environment. They also offer critical clues on the nature and style of plate tectonics, mantle dynamics and crust-mantle interaction. In this thematic section of Geoscience Frontiers, a set of four contri- butions are assembled that provide a window to the mechanisms and processes in Precambrian shields and associated suture zones from a geological and geophysical perspective.展开更多
This study demonstrates the compositional and structural analysis of surface sediments in natural depositional environment of the Brahmaputra River using X-ray fluorescence, Raman spectroscopic and Fourier transform i...This study demonstrates the compositional and structural analysis of surface sediments in natural depositional environment of the Brahmaputra River using X-ray fluorescence, Raman spectroscopic and Fourier transform infrared spectroscopic techniques. The main peaks in the Raman and infrared spectra reflected Al-OH, Al-O and Si-O functional groups in high frequency stretching and low frequency bending modes. The Raman and infrared spectra reveals the nature of clay (kaolinite) associated with quartz. The infrared spectra are indicative to the weathered metamorphic origin of the silicate minerals. The relative distributions of the contaminations in the sediment are: Si > Al > Fe > Mg > Ca > K > Ti > Mn > Cr >Ni > Zn > Cu > Co. The metal contaminations in the sediments are investigated by calculating the enrichment factor, contamination factor, geo-accumulation index and pollution load index. The relative distributions of the contamination among the samples are: Cu > Si > Mn > Mg > Ni > Cr > Ti > Al > Co > Pb > K > Ca > Zn. The investigating factors suggest the significant contamination in the sediment is due to Cu. The strong positive correlation among Al, Fe, Mg and K suggests association of sediments with clay. The elemental correlation is indicative to the metamorphosed pyrophanite (MnTiO3) deposition.展开更多
We present a brief overview of meteorites from the north-eastern India, with a focus on falls, finds, and research developments. To date, out of a total 150 numbers of meteorites fall/find in India (in Meteoritical Bu...We present a brief overview of meteorites from the north-eastern India, with a focus on falls, finds, and research developments. To date, out of a total 150 numbers of meteorites fall/find in India (in Meteoritical Bulletin Database), only six meteorites from north-eastern region have received official international recognition from the Nomenclature Committee of the Meteoritical Society. Among these six meteorites, 2 finds and 4 falls, including one ureilite, two H chondrites and three L chondrites. The first meteorite from north-eastern India (Assam L5, Find) was documented in 1846. After a lack of 153 years, the first fall (Sabrum LL6 chondrite) was documented in 1999. The most recent fall is Kamargaon (L6) chondrite in 2015. Intensively researched meteorites of this region are Goalpara and Dergaon. The reported most massive meteorite of north-eastern India is Mahadevpur (H4/5) chondrite, 70.5 kg of total known weight, and the rest are <13 kg of total known weight. The researches on these meteorites from north-east India can be applied to the newly recovered meteorites to understand the astrophysical enigma.展开更多
文摘The Precambrian shields and associated suture zones of the globe preserve important records of continental growth and destruction, the formation and closure of ocean basins, and the early evolution of the Earth in terms of tectonics, resources, and environment. They also offer critical clues on the nature and style of plate tectonics, mantle dynamics and crust-mantle interaction. In this thematic section of Geoscience Frontiers, a set of four contri- butions are assembled that provide a window to the mechanisms and processes in Precambrian shields and associated suture zones from a geological and geophysical perspective.
文摘This study demonstrates the compositional and structural analysis of surface sediments in natural depositional environment of the Brahmaputra River using X-ray fluorescence, Raman spectroscopic and Fourier transform infrared spectroscopic techniques. The main peaks in the Raman and infrared spectra reflected Al-OH, Al-O and Si-O functional groups in high frequency stretching and low frequency bending modes. The Raman and infrared spectra reveals the nature of clay (kaolinite) associated with quartz. The infrared spectra are indicative to the weathered metamorphic origin of the silicate minerals. The relative distributions of the contaminations in the sediment are: Si > Al > Fe > Mg > Ca > K > Ti > Mn > Cr >Ni > Zn > Cu > Co. The metal contaminations in the sediments are investigated by calculating the enrichment factor, contamination factor, geo-accumulation index and pollution load index. The relative distributions of the contamination among the samples are: Cu > Si > Mn > Mg > Ni > Cr > Ti > Al > Co > Pb > K > Ca > Zn. The investigating factors suggest the significant contamination in the sediment is due to Cu. The strong positive correlation among Al, Fe, Mg and K suggests association of sediments with clay. The elemental correlation is indicative to the metamorphosed pyrophanite (MnTiO3) deposition.
文摘We present a brief overview of meteorites from the north-eastern India, with a focus on falls, finds, and research developments. To date, out of a total 150 numbers of meteorites fall/find in India (in Meteoritical Bulletin Database), only six meteorites from north-eastern region have received official international recognition from the Nomenclature Committee of the Meteoritical Society. Among these six meteorites, 2 finds and 4 falls, including one ureilite, two H chondrites and three L chondrites. The first meteorite from north-eastern India (Assam L5, Find) was documented in 1846. After a lack of 153 years, the first fall (Sabrum LL6 chondrite) was documented in 1999. The most recent fall is Kamargaon (L6) chondrite in 2015. Intensively researched meteorites of this region are Goalpara and Dergaon. The reported most massive meteorite of north-eastern India is Mahadevpur (H4/5) chondrite, 70.5 kg of total known weight, and the rest are <13 kg of total known weight. The researches on these meteorites from north-east India can be applied to the newly recovered meteorites to understand the astrophysical enigma.
