Petrography and geochemistry of uranium mineralised Precambrian granitic-pegmatitic rocks of Mawlait, West Khasi Hills district, Meghalaya |
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| Authors: | J Sen N Ranganath YV Rathaiah D B Sen and S N Kak |
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| Institution: | (1) Department of Physics, North Eastern Hill University, Shillong, 793 022, Meghalaya, India;(2) Department of Zoology, North Eastern Hill University, Shillong, 793 022, Meghalaya, India |
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| Abstract: | During radiometric investigation at Mawlait, significant uranium mineralisation (0.024–0.22%U3O8) was located mainly within the small pegmatite (garnet bearing quartzofeldspathic rock), which are locally segregated within
migmatite at Umiang River section. Pink granite and granite gneisses are the dominant lithounits of the study area showing
fertile character and spotty radioactivity at several places. Radioactivity in these rocks is mainly contributed by discrete
uraninite grains along with some zircon and xenotime. Granites are peraluminous, low-Ca in nature and their geochemical signatures
suggest derivation from a felsic source. Discriminant diagrams using Rb, Nb and Y indicate ‘within plate’ to ‘volcanic arc’
nature of the rock. The uraniferous pegmatitic veins within migmatite appear to have formed due to localised metamorphic segregation
during late stage of anatexis. Petromineralogical and geochemical studies suggest that the uranium mineralisation in granitic-pegmatitic
rocks of the area is mainly syn-magmatic type. |
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