Moyen J. F., Cuney M., Baratoux David, Sardini P., Carrouee S. (2021). Multi-scale spatial distribution of K, Th and U in an Archaean potassic granite : a case study from the Heerenveen batholith, Barberton Granite-Greenstone Terrain, South Africa. South African Journal of Geology, 124 (1), 53-86. ISSN 1012-0750.
Titre du document
Multi-scale spatial distribution of K, Th and U in an Archaean potassic granite : a case study from the Heerenveen batholith, Barberton Granite-Greenstone Terrain, South Africa
Moyen J. F., Cuney M., Baratoux David, Sardini P., Carrouee S.
Source
South African Journal of Geology, 2021,
124 (1), 53-86 ISSN 1012-0750
We describe the multi-scale distribution of K, Th and U in the ca. 3.1 Ga Heerenveen batholith of the Barberton GraniteGreenstone Terrain. Data were obtained with a combination of tools, including a portable gamma-ray spectrometer from the scale of the whole batholith to the scale of outcrops, and autoradiography for the thin section scale. U is concentrated preferentially in minor phases in the border shear zones of the batholith and, within these shear zones, in late pegmatites as well as fractures. The processes responsible for the concentration of U in the Heerenveen batholith is discussed in terms of magmatism, hydrothermalism (redistribution of U in fissures associated with magmatohydrothermal fluids), and supergene alteration. The statistical properties of K, Th and U concentrations are different. K shows spatial correlation over large distance, largely mirroring mappable rock types, with increased variability at larger scales. In contrast, U is dominated by small-scale variations ("nugget effect") and its variability is, averaged and smoothed by large-scale integration. Spatial and statistical features thus offer useful and complementary insights on petrogenetic and metallogenic processes in granitoids in addition to standard approaches (petrography, geochemistry).
