10:45 AM - 12:15 PM
[SRD24-P01] Close-range spectroscopic techniques for detection of REE mineralization: A case study from Siwana Ring Complex, Rajasthan, India
Keywords:Rare Earth Elements, Siwana Ring Complex, Spectroscopy
Rare earth elements (REEs), which comprise of the lanthanides (Z= 57-71) along with scandium and yttrium, are considered to be of high economic importance due to their use in various modern technological products. Among the REEs, the elements showing sharp spectral absorption features in the VNIR to SWIR region include Nd, Sm, Eu and Pr, out of which Nd is known to exhibit prominent features at wavelengths 580 nm, 740 nm, 800 nm and 870 nm.
In this study, samples are collected from REE-bearing rocks of the Neoproterozoic Siwana Ring Complex (SRC), Rajasthan, India belonging to the Malani Igneous Suite. The SRC is an elliptical collapsed caldera structure and comprises of a bimodal volcano-plutonic rock association which includes felsic and basic volcanic lava flows, rhyolite, peralkaline granite, pyroclastics, tuff and later microgranite, aplite and felsite dykes.
These samples are studied using laboratory-based imaging spectroscopy and confirmatory geochemical analytical techniques. An ASD FieldSpec4 (350 nm – 2500 nm) is used to collect spectra from the samples. The spectral reflectance curves show distinctive absorption features at around 439 nm, 491 nm, 580 nm, 740 nm, 800 nm and 870 nm which indicate the presence of Nd3+. Fourier Transform Infrared (FTIR) spectra are collected in the range 400-4000 cm-1. Features observed due to asymmetric bending (538 and 585 cm-1) and asymmetric stretching (1050 and 1097 cm-1) vibrations of P-O bond indicate the presence of monazite. Ce (306-1772 ppm) and Nd (153-843 ppm) are the most abundant REEs. Trace and bulk rock geochemistry confirm the abundance of LREEs (ΣLREE = 662-3799 ppm). Presence of monazite-Ce, REE fluorocarbonates and allanite-Ce are confirmed by mineral chemistry along with the occurrence of zircon, sphene and apatite which correlate with the abundance of LREEs.
This study provides information on the spectral characteristics of rocks from the SRC. It is observed that imaging spectroscopy can be used as an effective low-cost technique for detection of REE mineralization before further exploration.
Abbreviations:
ASD – Analytical Spectral Devices, Inc.
FTIR – Fourier Transform Infrared
REE – Rare Earth Element
LREE – Light Rare Earth Element
SRC – Siwana Ring Complex
SWIR – Short Wave Infrared
VNIR – Visible Near Infrared
In this study, samples are collected from REE-bearing rocks of the Neoproterozoic Siwana Ring Complex (SRC), Rajasthan, India belonging to the Malani Igneous Suite. The SRC is an elliptical collapsed caldera structure and comprises of a bimodal volcano-plutonic rock association which includes felsic and basic volcanic lava flows, rhyolite, peralkaline granite, pyroclastics, tuff and later microgranite, aplite and felsite dykes.
These samples are studied using laboratory-based imaging spectroscopy and confirmatory geochemical analytical techniques. An ASD FieldSpec4 (350 nm – 2500 nm) is used to collect spectra from the samples. The spectral reflectance curves show distinctive absorption features at around 439 nm, 491 nm, 580 nm, 740 nm, 800 nm and 870 nm which indicate the presence of Nd3+. Fourier Transform Infrared (FTIR) spectra are collected in the range 400-4000 cm-1. Features observed due to asymmetric bending (538 and 585 cm-1) and asymmetric stretching (1050 and 1097 cm-1) vibrations of P-O bond indicate the presence of monazite. Ce (306-1772 ppm) and Nd (153-843 ppm) are the most abundant REEs. Trace and bulk rock geochemistry confirm the abundance of LREEs (ΣLREE = 662-3799 ppm). Presence of monazite-Ce, REE fluorocarbonates and allanite-Ce are confirmed by mineral chemistry along with the occurrence of zircon, sphene and apatite which correlate with the abundance of LREEs.
This study provides information on the spectral characteristics of rocks from the SRC. It is observed that imaging spectroscopy can be used as an effective low-cost technique for detection of REE mineralization before further exploration.
Abbreviations:
ASD – Analytical Spectral Devices, Inc.
FTIR – Fourier Transform Infrared
REE – Rare Earth Element
LREE – Light Rare Earth Element
SRC – Siwana Ring Complex
SWIR – Short Wave Infrared
VNIR – Visible Near Infrared