scholarly journals Petrography of low-grade metamorphic rocks of the Lesser Himalaya from Malekhu area, central Nepal

2015 ◽  
Vol 3 ◽  
pp. 28-35
Author(s):  
Rajendra Acharya ◽  
Kabiraj Paudyal
Keyword(s):  
Metamorphic Rocks ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Thin Sections ◽  
Rock Types ◽  
Central Nepal ◽  
Geological Unit ◽  
The Individual ◽  
Petrographic Study ◽  
Representative Samples

Petrographic study was carried out in the rocks of the Nawakot Group from the Malekhu area. Representative samples from all the units were collected systematically. The area is occupied by low-grade metamorphic rocks of the Lesser Himalaya. The main lithology of this study area consists of phyllite, quartzite, metasandstone, dolomite, slate and metabasics. The main aim of this study was to distinguish the individual rock types based on the petrographic characteristics. Necessity of this type of study is felt because about each geological unit has similar type of rocks. In the case of complex geological setting due to faults and thrusts, distinction between the macroscopically similar rocks is possible only under the thin sections. Keeping this geological problem in mind, altogether 12 thin sections of representative rocks were prepared and studied for mineral paragenesis, texture, microscopic structures, deformation characteristics and metamorphic grade. Chlorite is found in all pelitic rocks as a metamorphic index mineral.

scholarly journals Geology and Mineral Resources of Phalamdada-Dhuwakot Section of West-Central Nepal, Lesser Himalaya

2018 ◽  
pp. 59-64
Author(s):  
Arjun Bhattarai ◽  
Kabiraj Paudyal
Keyword(s):  
Mineral Resources ◽  
Geological Mapping ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Central Nepal ◽  
West Central ◽  
Metallic Mineral ◽  
Geological Control ◽  
Core Part

Geological mapping was carried out along the Phalamdanda-Dhuwakot section of west-central Nepal in the Lesser Himalaya. The aim of geological mapping was to prospect the metallic mineral resources in the area especially to assess the geological control of mineralization as prognostic mapping and study the genesis of mineralization. The area has developed low-grade metamorphic rocks of the Nawakot Group. Geological rock units like the Kuncha Formation, Fagfog Quartzite, Dandagaon Phyllite, Nourpul Formation and Dhading Dolomite are mapped in the area. Jal Bhanjyang Thrust carries the more older rocks of the Nourpul Formation over the Dhading Dolomite. The area is highly deformed as indicated by presence of folds. Outliers of Fagfog Quartzite and Dhading Dolomite are developed at the core part of the syncline. Phalamdada iron and Anbu Khaireni as well as Dharapani copper are the major metallic deposits reported in the area. Both deposits are considered as the syngenetic in nature. Bulletin of Department of Geology, vol. 20-21, 2018, pp:59-64

scholarly journals Stratigraphy of the western Nepal Lesser Himalaya: A synthesis

1996 ◽  
Vol 13 ◽  
Author(s):  
B. N. Upreti
Keyword(s):  
Sedimentary Rocks ◽  
Metasedimentary Rock ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Stratigraphic Sequence ◽  
Central Nepal ◽  
Stratigraphic Nomenclature ◽  
Work Done ◽  
Wide Zone

The western Nepal Lesser Himalaya, lying between the Marsyangdi and Bheri Rivers, is generally free from crystalline nappes and exposes the sedimentary and metasedimentary rock sequences in a wide zone between the MBT and the MCT. Geologically, the area is complicated by the presence of a number of folds, thrusts and imbricate zones. Despite the complicated geology, excellent studies have been carried out in recent years on the stratigraphy of this region. However, individual work has been confined in areas separated by wide intervening parts that are not as well studied. Many researchers have proposed different stratigraphic nomenclatures in their respective study areas, and their stratigraphic subdivisions do not always correspond well with each other. Therefore, confusion and uncertainties have remained in the stratigraphic interpretation of the western Nepal Lesser Himalaya. An attempt has been made here to appraise and synthesize the work done so far to bring out a clearer picture of the problems and prospects in the stratigraphic investigations in western Nepal. For convenience, the stratigraphy of the Lesser Himalayan metasediments the younger group of fossiliferous sedimentary rocks and the Jajarkot Nappe are treated separately. An attempt has been made to extend the stratigraphic nomenclature of the Nawakot Complex of central Nepal established by Stocklin and Bhattarai (1977) and Stocklin (1980) to western Nepal. In spite of the type sections of these rocks in central Nepal and the rocks of western Nepal being separated by a large intervening area, there is a fair consistency in the stratigraphic sequence and rock assemblages in the two areas. The uniformity in the use of nomenclature of rock units will greatly help to build up a more systematic and reliable stratigraphy of Nepal Lesser Himalaya in the future. The low grade metamorphic and the sedimentary rocks of the Lesser Himalaya are divided into the older Nawakot Unit and the younger Tansen Unit. Only the Tansen Unit is fossiliferous. Whereas the Nawakot Unit is largely of Precambrian age, the Tansen Unit ranges in age from Permo-Carboniferous to Lower Tertiary. The Jajarkot Nappe, tectonically overlying the Lesser Himalayan metasediments, consists of medium grade metamorphic rocks such as garnet bearing schists, feldspathic schists and quartzites. These rocks are succeeded conformably by unmetamorphosed carbonate rocks of possibly Cambro­ Ordovician age and stratigraphically and tectonically comparable to the Phulchauki Group of the Kathmandu Nappe of central Nepal.

A Discussion on natural strain and geological structure - The control of ductility on the deformation of pebbles and conglomerates

1976 ◽  
Vol 283 (1312) ◽  
pp. 109-128 ◽  
Keyword(s):  
Confining Pressure ◽  
Geological Structure ◽  
Metamorphic Rocks ◽  
Tectonic Deformation ◽  
Low Grade ◽  
Rock Types ◽  
Gravitational Loading ◽  
The Matrix ◽  
Host Rocks

Pebbles are commonly used parameters for the determination of finite strain in deformed rocks. In high grade metamorphic environments, rocks probably behave as viscous fluids and a theory exists which relates the deformation experienced by a pebble to that of the host rocks. However, some deformed conglomerates are found in low grade metamorphic rocks where the assumption of viscous behaviour is unrealistic The deformation of artificial conglomerates made of geological materials, at room temperature and varying confining pressure is described. In these experiments, pebbles deform by cataclasis at surprisingly low applied loads and large finite strains are achieved. The amount of deformation experienced by pebbles of different rock types depends mainly on their yield strengths and ductility contrasts with respect to the matrix. A theoretical analysis assuming that pebble and matrix behave as workhardening Bingham materials during deformation relates the strain experienced by a pebble to that of the host rock. The results suggest that significant pebble deformation can occur during gravitational loading of sediments. An attempt is made to verify this idea by analysing the shape of pebbles in conglomerates of the Upper Witwatersrand System. At some sites the pebbles appear to have deformed during gravitational compaction while at others a tectonic deformation has been superimposed upon the pre-tectomic strain.

scholarly journals Detached carbonate blocks in the northern Dang area Lesser Himalaya (Nepal)

1991 ◽  
Vol 7 ◽  
Author(s):  
M. R. Dhital
Keyword(s):  
Characteristic Feature ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Mode Of Occurrence

The process of movement of roof thrust in the northern Dang Lesser Himalaya gave rise to the deformation of various incompetent beds of limestone and dolomite from the underlying Gwar Group. Some of them are also disrupted from the footwall ramp and produced a stacked imbricate antiform of carbonates. In this process the floor thrust of the duplex became more active and later the displacement continued along the same. Afterwards, another larger duplex has formed beneath the stacked antiform. As a result, underneath the roof thrust consisting of the low-grade metamorphic rocks of the Sharda Group are found the detached and haphazardly distributed carbonates from the underlying Gwar Group. Characteristic feature and mode of occurrence of the detached carbonates, their lithology, and possible mechanism of thrusting are discussed here.

scholarly journals Lithostratigraphic comparison of three Diamictite successions of Nepal Lesser Himalaya

1992 ◽  
Vol 8 ◽  
Author(s):  
M. R. Dhital
Keyword(s):  
Metamorphic Rocks ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Coal Seams ◽  
Basic Volcanics ◽  
Strong Deformation ◽  
East And West

ABSTRACT The Proterozoic Blaini-type of diamictite sequences have been identified from the Lesser Himalaya (Brookfield, 1987). A tillitic sequence called the Sisne Formation of Gondwana age was reported by Sakai (1983) from Tansen, the Western Nepal Lesser Himalaya. The newly reported Kokaha Diamictite and Sallyan Diamictite situated to the east and west of Tansen, respectively, exhibit some lithostratigraphic similarity with the Sisne Formation, though the underlying and overlying rocks are quite different The Kokaha Diamictite from the Barahakshetra area of Eastern Nepal is underlain by grey quartzite with coal seams and conglomerate lenses. Sometimes tuffs and agglomerates are also found together with the diamictite in some places. It is followed upsection by grey calcareous sandstone, siltstone and shale. The Sisne Formation from the Tansen area of Western Nepal overlies grey dolomite with a disconformity and is followed by the Taltung Formation separated by another disconformity. The Taltung Formation itself is composed of basic volcanics, conglomerate, sandstone and siltstone. A non-Blaini type of diamictite horizon called the Sallyan Diamictite from the Sallyan area of West Nepal occurs in low -grade metamorphic rocks. It disconformably overlies quartzite, meta-conglomerates and phyllites, and is transitionally followed by black carbonaceou s slates. Lack of reliable fossils, metamorphism and strong deformation pose difficulties in correlating it with other diamictites.

scholarly journals Tracing the Mahabharat Thrust (MT) on the basis of lithology and microstructures around Bhainse-Manahari area, central Nepal

2016 ◽  
Vol 51 ◽  
pp. 39-48
Author(s):  
Laxman Subedi ◽  
Kamala Kant Acharya
Keyword(s):  
Hanging Wall ◽  
Strain Analysis ◽  
Metamorphic Rocks ◽  
Foot Wall ◽  
Low Grade ◽  
The North ◽  
Central Nepal ◽  
Complex Shear ◽  
Thrust Zone ◽  
Quartz Grains

Lithological and microstructural study carried out in Bhainse –Manahari area, central Nepal reveals that the rock sequences of the Bhainse–Manahari area can be divided into two successions: the Nawakot Complex and the Kathmandu Complex. These two Complexes are separated by a distinct thrust boundary, the Mahabharat Thrust (MT). The Nawakot Complex consists of low-grade metamorphic rocks like slate, phyllite, quartzite and limestone while the Kathmandu Complex comprises medium grade (up to garnet grade) metamorphic rocks like garnet-schist, marble and mica-schist. The Mahabharat Thrust (MT) and the Manahari Thrust (MnT) are the two major thrusts in the study area. The MT separates the rocks of the Nawakot Complex (foot wall) in the south from the rocks of the Kathmandu Complex (hanging wall) in the north. The Manahari Thrust in the western part of the study area separates the Dunga Quartzite and the older Benighat Slates lying above it. The microstructure analysis reveals that the rocks in the thrust zone show higher deformation than in the neighboring rocks, and this gradually decreases away from the MT zone. The strain analysis of quartz grains reveals that the rock sequences of the hanging wall of the MT showed pure, simple and complex shear senses and the rocks of the footwall also showed the same pattern indicating MT as a stretching fault.

scholarly journals Geology and rockmass condition of Dhulikhel-Panchkhal area, Kavre District, Central Nepal Lesser Himalaya

2013 ◽  
Vol 15 ◽  
pp. 1-14
Author(s):  
Prem Nath Paudel ◽  
Naresh Kazi Tamrakar
Keyword(s):  
Rock Mass ◽  
Rock Type ◽  
Physical And Mechanical Properties ◽  
Geological Mapping ◽  
Rock Mass Rating ◽  
Lesser Himalaya ◽  
Rock Masses ◽  
Northern Limb ◽  
Rock Types ◽  
Central Nepal

A geological mapping was carried out and the rock mass characteristics of the Lesser Himalayan rocks distributed in the Dhulikhel-Panchkhal area (Kavre Distric) were studied along with their physical and mechanical properties. The lithological units distributed in the study area belong to the Benighat Slate of the Upper Nawakot Group and the Bhimphedi Group as separated by the Chak-Rosi Thrust. The lithological units strike NW-SE and dip southwards forming the eastern closure of part of the northern limb of the Mahabharat synclinorium. The area comprises mainly micaceous quartzite, psammitic schist, metasandstone and metasiltstone. Micaceous quartzite is a rock type of the Kalitar Formation, Chisapani quartzite and the Markhu Formation. The Markhu quartzite is slightly calcareous. Psammitic schist is a rock type of the Kulekhani Formation and the Markhu Formation. Metasandstone and metasiltstone are the rock types of the Tistung Formation. The rock masses consist mainly of three to four major joint sets including the joint parallel to foliation. The discontinuity characteristics indicate that the rocks are blocky in nature, and nearly smooth to rough surface with soft filling aperture. The rock mass is nearly fresh, indurated and stiff. The slopes are influenced by stable and unstable wedges, plane and toppling failures. The rock masses are classified into fair to good rock classes according to rock mass rating system. DOI: http://dx.doi.org/10.3126/bdg.v15i0.7412 Bulletin of the Department of Geology, Vol. 15, 2012, pp. 1–14

scholarly journals Geological setting and lithostratigraphy of the Lesser Himalaya in the Mugling-Banspani area, central Nepal

2011 ◽  
Vol 42 ◽  
pp. 51-63
Author(s):  
K. R. Paudyal ◽  
L. P. Paudel
Keyword(s):  
Geological Mapping ◽  
Low Grade ◽  
Thrust Belt ◽  
Lesser Himalaya ◽  
Geological Structures ◽  
Metasedimentary Rocks ◽  
Geological Setting ◽  
Central Nepal ◽  
Fold And Thrust Belt

The Lesser Himalaya in central Nepal is a fold-and-thrust belt with a complex stratigraphy and structure. In the present study, detailed geological mapping was carried out in the Mugling-Banspani area based on stratigraphic units proposed by Stocklin and Bhattarai (1977) to reveal the geological setting and lithostratigraphy of the area. The study shows that the area is occupied by the low-grade metasedimentary rocks of the Lower Nawakot Group. However, there are several discrepancies in classification of the rocks of the Lower Nawakot Group and their classification does not correspond with the field realities. The Anpu Quartzite thought to be the oldest unit of the Nawakot Complex laterally joins to the Fagfog Quartzite. Similarly, the Banspani Quartzite and Labdi Phyllite laterally join to the Purebensi Qu artzite and Dandagao n Phyllite, respectively. Si milar ly, the Nourpul Formation is clearly divisible into three members with distinct lithological characteristics. Based on the above facts, a revise d stratigraphic classification has been proposed for the rocks of the Lower Nawakot Group in the Mugling­ Banspani area. The Lower Nawakot Group can be divided into the oldest Kunchha Formation followed up section by the Fagfog Quartzite (~Anpu Quartzite), Dandagaon Phyllite (~Labdi Phyllite), Nourpul Formation and Dhading Dolomite. The Nourpul Formation comprises three members namely the Purebensi Quartzite, the Amdanda Phyllite and the Labdi Khola Carbonate. The Jalbire Syncline, Mugling Anticline, Aklang Syncline and the Anpu Anticline are the major geological structures of the study area.

scholarly journals Geological setting and lithostratigraphy of Bandipur-Gondrang area of Lesser Himalaya, central Nepal

2013 ◽  
Vol 15 ◽  
pp. 49-62
Author(s):  
KR Paudyal ◽  
LB Adhikari ◽  
N Maharjan ◽  
LP Paudel
Keyword(s):  
Geological Mapping ◽  
Low Grade ◽  
Lesser Himalaya ◽  
The West ◽  
Metasedimentary Rocks ◽  
Geological Setting ◽  
Central Nepal ◽  
Present Study Area ◽  
Set Up ◽  
Bottom To Top

Detailed geological mapping was carried out in the Bandipur-Gondrang area of Tanahun district to clarify the geological set up and stratigraphy of the area. Wherever possible, geological mapping is based on stratigraphic units proposed by Stocklin and Bhattarai (1977) in central Nepal and the present mapping is the west ward continuation from Mugling-Banspani area (Paudyal and Paudel, 2011). The study area comprises low grade metasedimentary rocks of Nawakot Complex. The rock succession of the area are divided into six formations as the Kunchha Formation, the Fagfog Quartzite, the Dandagaon Phyllite, the Nourpul Formation with four members, the Dhading Dolomite and the Benighat Slates in stratigraphic upwards. The former four formations belong to Upper Nawakot Group and the remaining one belongs to the Lower Nawakot Group of Nawakot Complex (Stöcklin and Bhattarai, 1977). Based on lithology, the Nourpul Formation is divided into the Purebensi Quartzite, the Amdanda Phyllite, the Labdi Khola Member and the Bandipur Slate from bottom to top respectively. The Purebensi Quartzite is lithologically distinct in the field; the Labdi Khola Member is significant with copper and iron mineralization in the area, and the Bandipur Slate is also significant with roofing quality slate, however, the Amdanda Phyllite is mapped as an intervening member between significant lithologies. The rocks of the present study area consist of several sedimentary structures like mud cracks, ripple marks, graded bedding and cross and parallel laminations. A broad Ghumaune- Gondran Synclinorium is mapped in the area. In addition to this, several anticlines and synclines are also mapped in the study area. Jalbhanjyang Thrust has brought the older metasedimentary rocks of the Nawakot Complex over the younger rocks of the same Complex. Some corrections are recommended over the distribution of previously shown lithological units by Stocklin and Bhattarai (1977) around the Ghumaune-Bhut Khola section. DOI: http://dx.doi.org/10.3126/bdg.v15i0.7417 Bulletin of the Department of Geology, Vol. 15, 2012, pp. 49-62

Ages of Pre-Mesozoic formations of the Lesser Himalaya, Hazara District, Northern Pakistan

1975 ◽  
Vol 112 (5) ◽  
pp. 509-514 ◽  
Author(s):  
A. R. Crawford ◽  
R. G. Davies
Keyword(s):  
Metamorphic Rocks ◽  
Low Grade ◽  
Northern Pakistan ◽  
Lesser Himalaya ◽  
Rock Samples ◽  
Three Samples ◽  
Northwestern Iran ◽  
Sr Method

SummaryThree samples of low-grade metamorphic rocks from the Hazara Group, northern Pakistan, analysed as total-rock samples by the Rb—Sr method, give model ages of 765±20 and 950±20 Ma. The results are discussed in terms of the stratigraphy of Hazara, northwestern Iran, and certain other areas.

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