A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Narayan Das, G. R.
- Radioactive Carbonatites of Pakkanadu and Mulakkadu, Salem District, Tamil Nadu
Authors
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 19, No 2 (1978), Pagination: 53-63Abstract
Precambrian carbonatites associated with pyroxenites occur as discontinuous lenticular bodies intruding the syenites west of Pakkanadu (11°40'15'': 77°50'1'') and Mulakkadu (11°44'3'' : 77°50'2''). They strike northeast to southwest with easterly dips and have been emplaced along a major northeasterly trending deep crustal fault zone. Large outcrops of serpentinised dunites carrying accessory chromite, cut by asbestos and magnesite veins are also found along the same fault zone to the east and northeast of Pakkanadu.
The carbonatites are of the pure calcite-rich sovite type, with biotitic and ankeritic variants. Apatite, magnetite, allanite, barite, monazite, zircon and cerianite, are the accessory minerals.
Spectrographic analysis has revealed Ba, Sr, Ce and La in major amounts (more than 10,000 ppm) and Th, Nb, P, Zr, Y and Sc in minor amounts (< 10,000 ppm). Spectrographic data suggest that the carbonatite-pyroxenite complex is Ce-La rich.
Niobium is not found in economic concentrations. The general radioactivity recorded by the carbonatite-pyroxenites ranges from 5 to 20 x BG. Representative whole rock samples assay from 0.02% to 0.054% eU3O8 (Carbonatites) and 0.02% to 0.06% eU3O8 (pyroxenites). Allanites assay from 0.35% to 0.4% eU3O8 with chemical U3O8 values from 0.007% to 0.034%, thereby indicating the predominance of thorium over uranium. Monazite is mostly concentrated in the biotite-rich portions of the carbonatites to the west of Pakkanadu, whereas allanites predominate in the pyroxenites west of Mulakkadu.
- Geology, Structure and Uranium Mineralisation in Kulu, Himachal Himalaya
Authors
1 Atomic Minerals Division, Department of Atomic Energy, West Block No. VII, R. K. Puram, New Delhi 110022, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 20, No 3 (1979), Pagination: 95-102Abstract
Uranium mineralisation as Uraninite vein filling is seen in joints and fractures in the quartzites exposed within an eroded cover of crystallines, tectonically thrust from east and NE in Kulu-Banjar area of Himachal Pradesh. Analysis of the joints suggests a tensional origin and can be related to the three main folding events identified from the fold structure in the quartzites. It is believed that the mineralisation is essentially under low temperature-pressure conditions as there is a remarkable absence of large scale wallrock alteration.U-Pb dating of six Uraninite samples reveals two distinct episodes of mineralisation at 1200 m.y. and 700 m.y. confirming the Precambrian age of Uranium mineralisation, and associated metasediments.
- Uranium Mineralisation in Sikar District, Rajasthan
Authors
1 Atomic Minerals Division, Department of Atomic Energy, New Delhi-110022, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 21, No 9 (1980), Pagination: 432-439Abstract
Uranium mineralisation of segregated type consisting mostly of uraninite and less commonly of brannerite has been noted in the pink quartzo-feldspathic or aplitic emplacements along shear zones in Rohil-Ghateshwar-Khandela-Diara and Saladipura area in Sikar district of Rajasthan. Ilmenite, molybdenite, pyrrhotite, chalcopyrite and pyrite are noted along with uraninite.
Mineralisation is controlled by structure and generally occurs along linear shears that are parallel to the main tectonic lineament. In Ghateshwar area, the mineralised quartzo-feldspathic emplacements have undergone refolding along with the rest of the formations. Uranium mineralisation is near to the main tectonic lineament that passes through the axis of the Ajabgarh synclinorium. Integrated radiometric and hydrogeochemical surveys have indicated continuity of the uranium bearing quartzo-feldspatbic emplacements along a 16 km belt.
The Salwari fluorite occurrence 10 km NE of Khandela is a post feldspathic emplacement and probably formed during the final phases of mineralisation.
- Uraninite-Fluorite-Bearing Sheared Granites of Brijrani Gad in Bhilangana Valley (U.P.)
Authors
1 Department of Atomic Energy, West Block No. VII, R. K. Puram, New Delhi, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 5 (1981), Pagination: 247-247Abstract
No Abstract.Full Text
- Carbonatite-Alkaline Complex of Mundwara
Authors
1 Atomic Minerals Division, Department of Atomic Energy, New Delhi, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 12 (1982), Pagination: 604-609Abstract
Two types of carbonatite dykes - alvikite and beforsite are associated with (the Mundwara alkaline igneous complex. Petrochemical and mineralogical studies indicate enrichment of alkalies and niobium. Pyrochlore is noted in beforsites along with dolomite, apatite, barite and flourite, whereas calcite, ankerite, heamatite, aegirine, apatite and barite are noted in the alvikites. The presence of both metasomatic as well as intrusive syenites are noticed. Higher content of Nb is noted in the syenites containing sphene, aegirine and magnetite.
The presence of annular fractures around the plutons and the arcuate shatter zone with breccia on the outer margins of the Mer pluton indicate upwarping and later intrusion of carbonatites through the Erinpura granite. High P2O5 and Nb content of the soil samples around Mer Pluton suggest possible existence of a carbonatite plug below.