Dispersion and Upgradation of Limestone from new Umrangshu, Assam, India

North Cachor district of Assam, India is endowed with a vast deposit of limestone at New Umrangshu (25°31'51" to 25 '32'8" N latitude and 92°48'1" to 92 °48'7" E long-itude). The deposit contains about 116 million tones of limestone extended over an area of 3.5 square km, which is used presently for manufacturing cement. The limestone contains over 91% CaCO3 (— 51-52% CaO) with —2.1-2.7% MgO, —1.5-2.2% Si02 and —0.8-0.9% A1203 mostly in the form of calcite with small to trace amounts of impurities like kaolinite, pyrite, illite. It was earlier reported that size classification leads only to marginal improve-ment of the limestone. The coarser fraction contains the maximum amount of CaO and minimum amount of Si02, A1203 and Fe203,. whereas, the fine fraction contains the mini-mum amount of CaO and maximum amount of SiO2 and Fe,03. The impurities are evenly distributed in the limestone. The present communication reports the results of further works carried on beneficiation of the limestone. Fine grinding leads to liberation of the clay minerals; the major impurities of the limestone which may be removed by adopting dispersion-cum-settling technique resulting a fraction containing —97% CaCO3 (54.3% CaO) with —0.5% SiO2 and —0.6% A120

Geoenvironment and weathering of silicate minerals in sediments of the Brahmaputra river, India: Implications for heavy metal pollution assessment

We carried out detailed compositional studies on fifteen sediment samples from the Brahmaputra River that were collected in the pre-monsoon period, to obtain the inherent contamination factor. The present study demonstrates that the degrees of metal contamination in the sediments of the Brahmaputra river. Typical metals Fe, Al, Ti, Pb, Zn, Cu, Ni, Co, Mn and Cr, have been evaluated using several parameters like, enrichment factor (EF), contamination factor (CF), geo-accumulation index (Igeo) and pollution load index (PLI). The relative distributions of the contamination are found to be: Al > Fe > Ca > Mg > Ti > Mn > Cr > Cu > Zn > Ni > Pb > Co. The suspended sediments have been found to be moderately contaminated by the elements Cu, Pb, Cr, Mn and Ni. The nature of weathering is estimated using plagioclase index of alteration (PIA), chemical index of alteration (CIA), chemical index of weathering (CIW) and index of compositional variation (ICV). The studied suspended sediment samples indicate an intermediate silicate weathering of adjoins area

Occurrence of natural fullerene C60 from the iridium-rich Cretaceous-Paleogene (K-Pg) boundary layers of the Um-Sohryngkew river section, Meghalaya, India

The presence of fullerene C60 in the iridium-rich Cretaceous-Palaeogene (K-Pg) boundary layer from the Um-Sohryngkew river section of Meghalaya is reported here for the first time. Different analytical methods, including transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared (FT-IR), and X-ray diffraction(XRD) techniques, have been used to characterize the presence of toluene-insoluble high-pressure phase of fullerene C60 in the acid resistant carbonaceous matter extracted from the Um-Sohryngkew river section, Meghalaya, India. Strong absorption peaks at wavenumbers 1427, 1181, 574, and 525 cm−1, which are indicative of pristine fullerene C60, can be seen in the FTIR spectroscopic study. The Raman spectrum also independently confirms the presence of fullerene, by exhibiting the characteristics peaks of pristine fullerene C60. The XRD technique provides further, independent validation of fullerenes, and the XRD pattern demonstrates fullerene presence. Fullerenes, high-pressure fullerene, the amorphous phase of C60, and iridium all coexist and offer conclusive proof of impact at the Cretaceous-Palaeogene (K-Pg) boundary extinction event

Spectroscopic Investigations and Mineral Chemistry of Dunite from the Sargur Supracrustals (3 Ga) Greenstone Belt: Implications to Terrestrial Analogues for Lunar and Martian Dunite

Archean Serpentinised dunite is important not only for understanding the evolution of the ultramafic deposit of magnesium, but also serves as a possible sink material for the carbon dioxide sequestration. Future anti-pollution measures may include sequestering of waste CO2 as magnesite (MgCO3) by processing ultramafic rocks to obtain reactable Mg. For the first time, the Raman spectroscopic investigation of dunite is presented from the Karya, Sargur supracrustals (3Ga) Greenstone Belt. The Raman spectra of the sample reveal abundant presence of serpentine. Polymorphs of serpentine: lizardite, antigorite and chrysotile exhibit typical intense band at 685–692 cm–1 in the Raman spectrum. The Raman peaks in this study also indicates the presence of chromite and magnesite. The lunar dunite 72415, one of the oldest lunar samples of the Mg-suite, contains chromite symplectites indicative of crystallization at 40–50 km rather than at a shallow depth of <1 km, also having a olivine content of about 85%. The present study showed the dunite has about 85% olivine, which is almost identical to the Martian dunite, meteorite Northwest Africa (NWA) 2737 is the second known chassignite, an olivine-rich igneous rock with mineral compositions and isotopic ratios that suggest it formed on Mars. NWA 2737 consists of ~ 85% vol. The present study on the Karya dunite of Sargur supracrustals (3 Ga) greenstone belt, Western Dharwar Craton Karnataka, indicates a possibility of using this as a terrestrial analogue material for improving the Martian surface mineralogy and occurrence of hydrous minerals and life support system in Mars