Salem dolerites were collected across the dyke from various parts of the studied area for identifying the differentiation process of magma in the conduits from the compositional profile. The thick dolerites show NNW-SSE, NE-SW, and NW-SE trends. The studied dyke shows systematic composition increasing and decreasing in the chilled margin and centre of the dyke as the texture and concentration of plagioclase and pyroxene increase. Chilled margins show microcrystalline to intersertal, and the centre of the dyke show sub ophitic textures. The compatible oxide MgO, element Ni and the Mg number (100Mg/(Mg+FeT)) increased and the incompatible oxides TiO2, P2O5, and elements Zr decreased from the chilled margin to the centre of the dyke in the compositional profile show reverse fractionation trends (opposite to fractional crystallization) in the studied dykes except for Seeliyampatti dyke. The Seeliyampatti dolerites show opposite compositional variations indicating a normal fractionation trend from the other dykes of the study area. The reverse fractional trends in dykes resulting in the progressive increase of cumulate minerals growth against the dyke wall called the «cumulate process», however, the normal fractional trend in Seeliyampatti resulting in the progressive increase of more evolved magma successively removes the early chilled margin and fills the thick dyke with less compatible and more incompatible components toward the centre of the dyke. Although the normal trend in thick dyke considered the exceptional liquid process of magma differentiation that was formed more like fractional crystallization. Factor analysis also supports the differentiation process of magma. The first factor accounts total variance of 57.68% showing the positively loaded incompatible element and negatively loaded compatible elements.
The demand for iron ore has increased recently and employing geochemical and hyperspectral remote sensing techniques for discovering new ore and mineral resources have primarily been concentrated on the economic phases. The present study aimed to characterize the hyperspectral spectral signatures of iron ores of field samples to map the deposits that occurred in the Tirthamalai hill region, which lies in the parts of Harur Taluk, Dharmapuri district of Tamil Nadu state, India The measurement and study of spectral signatures of the different samples of the deposits showed strong spectral absorptions near 500 nm, 900 nm and 2400 nm wavelength regions and were confirmed with the Fourier Transform Infrared (FTIR) spectroscopy method. The spectral absorption characteristics of the samples were evaluated by the study of the physical, optical, and chemical characteristics of the samples. The study of hyperspectral and FTIR spectral signatures with petrographic and major chemical elements revealed the best absorption characteristics of the iron ore deposits of the study region and can be used elsewhere in the world. This report presents preliminary findings on the use of hyperspectral imaging to characterize iron ore. The mineralogical products produced from hyperspectral images may improve in situ grade control on an iron ore mine face. It will be extremely useful for businesses in measuring large numbers of commodities quickly and objectively.
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