Features and characterization of graphite in Almora Crystallines and their implication for the graphite formation in Lesser Himalaya, India

Rawat, R. S.; Sharma, Rajesh

doi:10.1016/j.jseaes.2011.03.015

Cited by 17 publications

(11 citation statements)

References 36 publications

(62 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Further implication of this flexural folding is the formation of extrusive wedged-shaped domains as a result of inhomogeneous shortening which in turn implies minor shearing components along the cleavage planes (Hobbs et al 1982, Price and Cosgrove 1990, Williams 1990. Another distinctive feature is its crystallinity which increases with increase in grade of metamorphism and remains unaffected during retrogression, provides degree of graphitisation and temperature of graphite formation (Rawat and Sharma 2011). The photomicrograph shows graphite and biotite associated with variable amount of quartz and plagioclase.…”

Section: Results and Applicationsmentioning

confidence: 99%

Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks

Nkpadobi

Raj

2015

Geomechanics and Geoengineering

View full text Add to dashboard Cite

The meta-sedimentary rocks along Pos Selim Highway in Perak State, Malaysia showed a gradational weathering profile based on differences particularly in textures, hardness, lateral changes in colour and consistency of material extension. Both large and small scale discontinuities observed in the investigated rocks reduce the physical and mechanical properties of the rocks, and provide slip surfaces for failures. Rock and soil samples were tested using established standards to determine their characteristics and responses under a wide variety of disturbances. Kinematic analyses were also carried out to determine the modes and likely modes of failures.Petrographic analyses revealed associated micro-structures, and the implications of these micro-structures showed shearing components along planes of weakness. From the determined index properties of the tested soil samples, the weathered quartz mica schist is not suitable for structural support. Further study involving unconsolidated undrained direct shear box tests carried out under total stress, revealed a non-uniform response of the rocks to shearing disturbance along discontinuity planes, and the rate and depth of deformation. The shear strength components of the investigated rocks were thereby prescribed in terms of cohesion and friction angle. From the kinematic analyses across this extended cut slope, there are possibilities of wedge and planar failures.

show abstract

Section: Results and Applicationsmentioning

confidence: 99%

Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks

Nkpadobi

Raj

2015

Geomechanics and Geoengineering

View full text Add to dashboard Cite

show abstract

“…Further implication of this flexural folding is the formation of extrusive wedged-shaped domains as a result of inhomogenous shortening which in turn implies minor shearing components along the cleavage planes (Hobbs et al 1982;Williams 1990;Price and Cosgrove 1990). Another distinctive feature is its crystallinity which increases with increase in grade of metamorphism and remains unaffected during retrogression, and provides degree of graphitization, and temperature of graphite formation (Rawat and Sharma 2011). The photomicrograph shows graphite and biotite associated with variable amount of quartz and plagioclase.…”

Section: Applicationsmentioning

confidence: 99%

Failure mechanisms in weathered meta-sedimentary rocks

Nkpadobi

Raj

2014

Environ Earth Sci

View full text Add to dashboard Cite

The weathering profile of the extended cut slope within the quartz mica schist along Pos Selim Highway in Perak State, Malaysia shows three broad morphological zones; bedrock zone, intermediate zone, and residual soil zone. Further thinner horizons within these broad morphological zones were differentiated based on differences particularly in textures and structures of original bedrock and degree of preservation of the constituent minerals. Both large and small scale discontinuities observed in the schist provide slip surfaces for failures, and field investigation showed evidence of failures in this extended cut slope. The implications of the micro-structures revealed through petrography showed shearing components along planes of weakness. From the determined index properties of the weathered profile, the quartz mica schist is not suitable for structural support. This is also evidenced by the high values of sand over silt and clay deduced from the sieve analysis. In the bedrock zone, weathering manifests itself by opening up of discontinuities within the rock mass rather than weakening of the material itself. From the kinematic analyses carried out on the rock cuts, there are possibilities of wedge, planar and toppling failures across this extended cut slope.

show abstract

“…Two geochemically distinct tectonostratigraphic units—the Neoproterozoic‐Ordovician Greater Himalaya and lowermost part of the Paleoproterozoic lower Lesser Himalaya—form the high‐grade metamorphic core of the Himalayan orogen in the Kumaun‐Garhwal region (Uttarakhand) of northwestern India (Figure ) [ Valdiya , ; Srivastava and Mitra , ; Célérier et al ., ; Spencer et al ., ; Kohn , ]. However, similar lithologies, metamorphism, and ductile deformation make it difficult to differentiate these two similar looking rock units [ Valdiya , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., , , ] and to interpret the structural significance of klippen that carries these rocks, including the Almora, Bajnath, Askot, Chiplakot, and Lansdowne klippen (Figure ). These klippen occur as metamorphic rock outliers within the Lesser Himalayan tectonostratigraphic zone, and identifying their proper tectonostratigraphic affinity is crucial to structural reconstructions of the orogen in this region [ Valdiya , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., , ].…”

Section: Introductionmentioning

confidence: 99%

“…However, similar lithologies, metamorphism, and ductile deformation make it difficult to differentiate these two similar looking rock units [ Valdiya , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., , , ] and to interpret the structural significance of klippen that carries these rocks, including the Almora, Bajnath, Askot, Chiplakot, and Lansdowne klippen (Figure ). These klippen occur as metamorphic rock outliers within the Lesser Himalayan tectonostratigraphic zone, and identifying their proper tectonostratigraphic affinity is crucial to structural reconstructions of the orogen in this region [ Valdiya , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., , ]. Physical similarities in lithologic appearance necessitate use of geochemical discrimination methods, such as U‐Pb zircon ages or Nd isotopic data, that can separate the Neoproterozoic‐Ordovician rocks of the Greater Himalaya from the Paleoproterozoic rocks of the lower Lesser Himalaya.…”

Section: Introductionmentioning

confidence: 99%

“…The largest klippe in the region—the Almora klippe—is commonly interpreted as the southern extension of Paleoproterozoic Munsiari Formation equivalent rocks [ Valdiya , ; Srivastava and Mitra , ; Célérier et al ., ; Rawat and Sharma , ; Patel et al ., ]. However, the klippe instead contains widespread Neoproterozoic (circa 900 Ma) metasedimentary and Ordovician intrusive rocks and must instead be composed of Greater Himalayan rocks, carried southward by the Main Central thrust (regionally called the Vaikrita thrust) [ Mandal et al ., ].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Zircon U‐Pb ages and Hf isotopes of the Askot klippe, Kumaun, northwest India: Implications for Paleoproterozoic tectonics, basin evolution and associated metallogeny of the northern Indian cratonic margin

et al. 2016

View full text Add to dashboard Cite

Throughout the Himalayan thrust belt, klippen of questionable tectonostratigraphic affinity occur atop Lesser Himalayan rocks. Integrated U-Pb ages, Hf isotopic, and whole rock trace element data establish that the Askot klippe, in northwest India, is composed of Paleoproterozoic lower Lesser Himalayan rocks, not Greater Himalayan rocks, as previously interpreted. The Askot klippe consists of 1857 ± 19 Ma granite-granodiorite gneiss, coeval 1878 ± 19 Ma felsic volcanic rock, and circa 1800 Ma Berinag quartzite, representing a small vestige of a Paleoproterozoic (circa 1850 Ma) continental arc, formed on northern margin of the north Indian cratonic block. Detrital zircon from Berinag quartzite shows εHf 1850 Ma values between À9.6 and À1.1 (an average of À4.5) and overlaps with εHf 1850 Ma values of the Askot klippe granite-granodiorite gneiss (À5.5 to À1.2, with an average of À2.7) and other Paleoproterozoic arc-related Lesser Himalayan granite gneisses ( À4.8 to À2.2, with an average of À4.0). These overlapping data suggest a proximal arc source for the metasedimentary rocks. Subchondritic εHf 1850 Ma values (À5.5 to À1.2) of granite-granodiorite gneiss indicate existence of a preexisting older crust that underwent crustal reworking at circa 1850 Ma. A wide range of εHf 1850 Ma values in detrital zircon (À15.0 to À1.1) suggests that a heterogeneous crustal source supplied detritus to the northern margin of India. These data, as well as the presence of a volcanogenic massive sulphide deposit within the Askot klippe, are consistent with a circa 1800 Ma intra-arc extensional environment.

show abstract

Features and characterization of graphite in Almora Crystallines and their implication for the graphite formation in Lesser Himalaya, India

Cited by 17 publications

References 36 publications

Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks

Influence of discontinuities on the stability of cut slopes in weathered meta-sedimentary rocks

Failure mechanisms in weathered meta-sedimentary rocks

Zircon U‐Pb ages and Hf isotopes of the Askot klippe, Kumaun, northwest India: Implications for Paleoproterozoic tectonics, basin evolution and associated metallogeny of the northern Indian cratonic margin

Contact Info

Product

Resources

About