Mineralogy and spectroscopy (VIS near infrared and micro-Raman) of chromite from Nidar ophiolite complex, SE Ladakh, India: Implications for future planetary exploration. (January 2019)

• Record Type: Journal Article
• Authors: Naveen, ; Sarkar, S.; Kumar, T. Nirmal; Ray, D.; Bhattacharya, S.; Shukla, A.D.; Moitra, H.; Dagar, A.; Chauhan, P.; Sen, K.; Das, S.
• Is Part Of: Planetary and space science. Volume 165(2019)
• Page Start: 1
• Page End: 9
• Publication Date: 2019-01
• Subjects: Chromite -- VNIR spectroscopy -- Micro-Raman spectroscopy -- Nidar ophiolite complex -- Planetary exploration; Space sciences -- Periodicals; Atmosphere, Upper -- Periodicals; Sciences spatiales -- Périodiques; Haute atmosphère -- Périodiques; 523
• DOI: 10.1016/j.pss.2018.12.007
• Languages: English
• ISSNs: 0032-0633

Abstract

Abstract: To determine the chemical composition of minerals on planetary surfaces from spectroscopic data, it is required to establish the link between mineralogy, spectroscopy and chemical composition of rock forming minerals on Earth. To meet this requirement, we performed integrated mineralogical and spectroscopic (Visible-Near Infrared and micro Raman) characterisation of chromite from the chromitite layer in the mantle section of the Nidar ophiolite complex, SE Ladakh, J&K, India. Chromite commonly occurs as monominerallic chromitite layers (up to 1 meter wide) and disseminated grains within the dunites and harzburgites. The Cr2 O3 content is generally high (>60 wt%) and chemically homogeneous across the grains. The X-ray Diffraction (XRD) analyses show highest peak intensity at ∼36° 2θ, followed by other diagnostic peaks for chromite. Micro-Raman of chromite yields very strong diagnostic Raman active vibrational modes at 685 cm −1 (A1g ), followed by 520 cm −1 (F2g(2) ). The other peaks, viz. 446 cm −1 and 610 cm −1 are rather weak and correspond to Eg and F2g, respectively. VNIR (0.4μ to 2.4μ) reflectance spectroscopy of chromite suggested strong absorption near 2 μm and could be useful to quantify the chemical composition (especially Cr2 O3, Al2 O3 and Cr#). We found a good correlation of VNIR absorption and chemical composition of chromite (e.g. band positions versus Al2 O3 and Cr# are well within 95% correlation interval). The intense Raman peak at 685 cm −1 corresponds to higher Cr content. This study, therefore, implies a significant understanding in determination of mineral chemistry (especially Chromites) by VNIR and micro Raman spectroscopy, which could be a useful tool for the future planetary exploration. Highlights: Chromites from ophiolite are common and their chemistry and structure can be linked to spectroscopic observations. Spectroscopic (VNIR and micro-Raman) and mineral chemical studies of chromite can be correlated. VNIR and micro Raman spectroscopy can be a useful tool in future planetary exploration.