Differences in natural gamma radiation characteristics of Erinpura and Malani granites in NW India

Abstract

In NW India, large volumes of exposed Neoproterozoic basement rocks are formed by two magmatic suites, Erinpura granites as a late thermal event with respect to the ∼1 Ga Delhi Orogeny and the younger Malani igneous suite (770-750 Ma). Average uranium and thorium equivalent concentrations (in ppm) inferred from spectroscopic gamma radiation survey are higher in Malani rocks (Th 47.33 ppm and U 6.95 ppm) as compared to the Erinpura granites (Th 33.55 ppm and U 4.77 ppm). These values are considerably above the granite world average (Th 14.8 ± 13.2 ppm; U 3.93 ± 3.27 ppm). High U (up to 19 ppm) and Th (up to 88 ppm) in some Malani granites and a constant Th-U ratio of 7 points to a high degree of fractionation of the felsic magma. Higher radioelement concentration in the east (Mirpur granite) as compared to the west (Jaswantpura granite) is substantiated by geochemical data. Areas to the west and east of the Sirohi frontal thrust show differences, most likely a consequence of anatexis in the eastern sector. A high linear correlation between inductively coupled plasma mass spectrometry and gamma-ray data underlines the suitability of in-situ measurements for the determination of U and Th concentrations during a field survey providing basic information for future petrogenetic and risk-hazard studies in this granitic terrain.

Radiogenic heat production of Variscan granites from the Western Bohemian Massif, Germany

“…For quality control of the gamma radiation (GR) data, comparison with geochemical data is necessary. Previously, we have substantiated the general significance of indirect GR measurements with the RS 230 equipment (Scharfenberg et al 2019). This study showed good correlation of U and Th concentrations derived from in situ measurements and data measured by ICP-MS.…”

“…A-type granites (Loiselle and Wones 1979;Eby 1992) are typical of intra-plate, often anorogenic settings. They are the most abundant in Proterozoic terranes, such as the Malani Igneous suite in NW India (Eby and Kochhar 1990;de Wall et al 2018), and are characterized by generally high radioelement concentrations (Scharfenberg et al 2015(Scharfenberg et al , 2019 resulting in higher RHP (Singh and Vallinayagam 2012). Therefore A-type granites commonly rank to high-heat-producing granites (HHP granites).…”

“…Frattini et al 2006;Šimíček et al 2012;McCay et al 2014;Puccini et al 2014;Harley et al 2017). In granitic terrains, an advantage of gamma-ray spectroscopy over chemical analysis is the easier mapping and therefore better regional coverage (Gnojek et al 2018;Scharfenberg et al 2019).…”

Origin of S-, A- and I-Type Granites: Petrogenetic Evidence from Whole Rock Th/U Ratio Variations

“…Felsic rocks of the Malani Igneous Suite are well known for their high radiogenic heat production [84]. The Malani granites are characterized by high but varying Th and U concentration [85]. Some intrusions such as granites forming the Mt.…”