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Bhu, Harsh
- Dynamic Recrystallisation and Quartz Fabric in Palaeoproterozoic Conglomerate, East of Udaipur, Rajasthan
Authors
1 Department of Geology, Mohanlal Sukhadia University,Udaipur- 3 13 002, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 68, No 5 (2006), Pagination: 819-830Abstract
The paper reports the study of strain analysis on pebbles of a horizon of polymictic conglomerate belonging to the Debarn Formation of the Aravalli Super group. The variable shape geometry of pebbles observed in different parts of the conglomerate outcrops, which cover a long linear distance east of Udaipur, is indicative of heterogeneous superimposed stream on somewhat Non-Spherical initial bodies.Micro textural studies indicated a variety of strain forms in constituent grains of both pebble and matrix along with attendant recovery through Sub-Gram formation and recrystallisation. Mica grams in the matrix have acted as a strainpartitioning mineral.
The lattice preferred orientation of c-axes in quartz is comparable to partially developed Type I pattern developed in regions of coaxial deformation. The pattern has been influenced by strain a d dynamic recrystallisation. The slip planes that operated in the deformation of quartz grains varied from basal slips to prism slips Basal slips were dominant at low temperature and low strain regions in quartz while prism slips at moderately higher temperature and moderate strain. The variation in slip planes can be accounted by in homogeneous nature of deformation possibly due to difference in critically resolved shear stresses in the conglomerate.
Keywords
Paleoproterozoic, Deformed Conglomerate, Strain Analysis, Quartz, Dynamic Recrystallisatlion, Deban Formation, Aravalli Supergroup, Rajasthan- Tectonostratigraphic Status of the Proterozoic Babarmal Pink Marble from the Aravalli Supergroup
Authors
1 Department of Geology, Government College, Sirohi - 307 001, IN
2 Department of Geology, M.L. Sukhadia, University, Udaipur - 313 00, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 79, No 2 (2012), Pagination: 135-150Abstract
Present study reviews the tectono-stratigraphic status of Babarmal pink marble from the Aravalli Supergroup through mapping and petrographic study of marble as well as associated lithologies. The pink marble is predominantly calcitic and characteristically different from dolomitic carbonate rocks of the Jhamarkotra Formation, the Lower Aravalli Group. The marble is devoid of organic matter and phosphate content unlike the Jhamarkotra dolomite. The pink marble is underlain by quartz-pebble rich conglomerate. This assemblage represents a rare lithological association which has not been reported so far from the Aravalli Supergroup.Besides the above differences between the Babarmal pink marble and the Jhamarkotra dolomite we also noted significant similarities between the two with respect to greenschist facies metamorphism and three phases of deformational history. Similarities in both these aspects imply that the pink marble like the Jhamarkotra dolomite can be corroborated with the Aravalli orogenic cycle. While on the basis of distinguishing lithological and petrographic features the pink marble-pebbly conglomerate, the lithoassemblage is suggested to be designated as "Babarmal Formation" as a modification to the Babarmal Formation of Gupta et al. (1997) which constituted of pink marble.
The outcrop patterns on the high resolution map shows that the Babarmal litho-assemblages are sandwiched between the Barytes bearing meta-volcanics (that represent the underlying Delwara Formation) and the dolomite-quartzite-phyllite (that represent the overlying Jhamarkotra Formation) of the Lower Aravalli Group (Roy and Jakhar, 2002). Hence we suggest to place the Babarmal Formation as the middle stratigraphic unit of the Lower Aravalli Group of the Aravalli Supergroup.
Keywords
Tectonics, Stratigraphy, Proterozoic, Pink Marble, Pebbly Conglomerate, Babarmal, Aravalli Supergroup.References
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