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Rao, N. K.
- Deformation Twinning in Stibnite from Punjab, India
Abstract Views :450 |
PDF Views:2
Authors
N. K. Rao
1,
G. V. U. Rao
1
Affiliations
1 Metallurgy Division, Atomic Energy Establishment, Trombay, IN
1 Metallurgy Division, Atomic Energy Establishment, Trombay, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 7 (1966), Pagination: 28-32Abstract
Prismatic sections of stibnite obtained from-Punjab, India, show various types of twinning, whose nature indicates deformation origin of the twinning . The twinning is simple or repeated or polysynthetic; in the latter case the twin lamellae may be parallel, wedge-, lens- or spindle-shaped, twisted and sinuous.
The disposition of the twinning lamellae and their relation to the (010) cleavage indicate that twin gliding has taken place in the plane (001) along [010]. This is probably due to the least coherence along [010]. The various patterns of twin lamellae are due to (a) trans lation gliding (010) [001] (b) bending about [100] and © twisting about [001] subsequent to the twinning. The simple types of twins are either due to accumulation of localised stresses during alteration or due to grinding and polishing, and the complex ones are due to shearing movements during or after deposition of stibnite.
- Alteration of Beach Sand Ilmenite from Manavalakurichi, Tamil Nadu, India
Abstract Views :168 |
PDF Views:2
Authors
N. P. Subrahmanyam
1,
N. K. Rao
1,
D. Narasimhan
1,
G. V. U. Rao
1,
N. K. Jaggi
2,
K. R. P. M. Rao
2
Affiliations
1 Ore Dressing Section, Bhabha Atomic Research Centre, Begumpet, Hyderabad - 500 016, IN
2 Nuclear Physics Division, B. A. R. C., Bombay - 400085, IN
1 Ore Dressing Section, Bhabha Atomic Research Centre, Begumpet, Hyderabad - 500 016, IN
2 Nuclear Physics Division, B. A. R. C., Bombay - 400085, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 4 (1982), Pagination: 168-174Abstract
The study shows that the alteration of ilmenite has taken place according to the two stage model proposed by Grey and Reid (1975). Identification of the intermediate altered compound, pseudorutile, was found difficult in earlier studies by optical and X-ray diffraction methods, because of the occurrence of this phase in altered ilmenite in very fine grain size (30 Å), its poor crystallinity and coincidence of many of the diffraction lines with those of other phases. The present study has shown that the Mossbauer technique is more suitable in the identification and estimation of this phase.
The relative amount of pseudorutile increases progressively in the magnetic fractions in the following order: 0.30 - 0.35 amps (5%), 0.25 - 0.30 amps (40%), 0-0.25 amps (75%) and 0.35 - 0.50amps (95%), indicating that the magnetic susceptibility of the grains is increasing initially with progressive pseudorutile formation, and decreasing in the later stages of alteration. Reflectivity and hardness are also increasing up to the stage of pseudorutile formation and decreasing in the later stages.
- Alaskan-Type Mafic–Ultramafic Complex at Padhar, Betul Belt, Central India
Abstract Views :261 |
PDF Views:82
Authors
Affiliations
1 Geological Survey of India, Central Region, Nagpur 440 006, IN
2 Geological Survey of India, Southern Region, Hyderabad 500 068, IN
3 Geological Survey of India, National Center of Excellence in Geoscience Research, Kolkata 700 016, IN
4 Geological Survey of India, National Center of Excellence in Geoscience Research, Bengaluru 560 078, IN
1 Geological Survey of India, Central Region, Nagpur 440 006, IN
2 Geological Survey of India, Southern Region, Hyderabad 500 068, IN
3 Geological Survey of India, National Center of Excellence in Geoscience Research, Kolkata 700 016, IN
4 Geological Survey of India, National Center of Excellence in Geoscience Research, Bengaluru 560 078, IN
Source
Current Science, Vol 114, No 03 (2018), Pagination: 671-678Abstract
We report here an Alaskan-type mafic–ultramafic complex at Padhar from the Precambrian Betul Belt of Central India. The Padhar intrusive bodies show lithological zoning defined by olivine-bearing ultramafic rocks in the core and gabbroic rocks at the margins, and are commonly accompanied by Cr–Cu–Ni sulphide mineralization. Mineral chemistry and whole-rock geochemistry of these rocks indicate that they are derived from the crystallization of hydrous magmas. The Padhar complex is characterized by high Mg and low abundance of incompatible trace elements. Flat REE pattern with negative Nb anomaly suggests arcmagmatism typical of Ural–Alaskan type. Presence of Mg-rich clinopyroxene and hornblende-rich rock types in the Padhar mafic–ultramafic intrusives along with paucity of orthopyroxenes in them further distinguish its from different types of complexes, i.e. ophiolite, Alpine and stratiform layered-type. These features are akin to Alaskan-type rocks as seen in Alaska, Canada and Urals of Russia. This finding of Alaskan-type ultramafic complex in the Padhar area of Betul Belt, Madhya Pradesh, is significant and has important implications in the tectonics and geodynamics of the Central Indian Tectonic Zone in general, and in the search of platinum group of minerals in particular.Keywords
CITZ, Mafic–Ultramafic Complex, Hydrous Magmas, Intrusive Bodies, Lithological Zoning.Full Text
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