Magnetic fabrics in an apparently undeformed granite body near Main Boundary Thrust (MBT), Kumaun Lesser Himalaya, India

2021 ◽  
pp. 228996
Author(s):  
Amar Agarwal ◽  
Deepak C. Srivastava ◽  
Jyoti Shah ◽  
Manish A. Mamtani
Keyword(s):  
Lesser Himalaya ◽  
Magnetic Fabrics ◽  
Main Boundary Thrust ◽  
Granite Body ◽  
Kumaun Lesser Himalaya

Tectonics and evolution of the central sector of the Himalaya

1988 ◽  
Vol 326 (1589) ◽  
pp. 151-175 ◽  
Keyword(s):  
Late Holocene ◽  
Granulite Facies ◽  
Lesser Himalaya ◽  
Main Central Thrust ◽  
Indian Shield ◽  
Ganga Basin ◽  
Granulite Facies Metamorphism ◽  
Slowing Down ◽  
Main Boundary Thrust ◽  
The Himalaya

Following the India-Asia collision, intracrustal movements along the Main Central Thrust (MCT) and Main Boundary Thrust (MBT) in a piggy-back-style, thrust duplexes developed that uplifted the Vaikrita (Central) crystallines of the basement to more than 8000 m elevation. Blocking of subduction on the suture and slowing down of movement on the MCT led to the formation of the Trans-Himadri (Malari) Thrust between the Vaikrita basement and the Tethyan cover sediments, and to gravity-induced backfolds and backthrusts in the latter. The Vaikrita crystallines underwent upper amphibolite to lower granulite facies metamorphism at 600-650 °C and more than 5 kbar (1 kbar = 101 *8 Pa) and migmatistation associated with 28-20 Ma old S-type granites that formed at 15-30 km depth during the culmination of metamorphism and thrust deformation. Delimited by the MCT and MBT, the Lesser Himalaya is made of Proterozoic sediments beneath the Almora nappe constituted of low- to medium-grade metamorphics and 1900+ 100 Ma old granitic gneisses and 560 + 20 Ma old granites. The Lesser Himilaya underwent considerable neotectonic rejuvenation during differential movements along the MBT. The frontal Siwalik molasse below the MBT was severely thrusted and folded in the late Holocene, and continued underthrusting of the Indian Shield beneath the Himalaya is manifest in the development and activation of the deep Himalayan Front Fault (HFF), which separates the Siwalik from the subRecent-Recent alluvial plain of the Ganga Basin.

Accelerated mass movement activities due to increased rainfall in the Nainital township, Kumaun Lesser Himalaya, India

2017 ◽  
Vol 61 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vikram Gupta ◽  
RuchikaS. Tandon ◽  
B. Venkateshwarlu ◽  
RajinderK. Bhasin ◽  
AmirM. Kaynia
Keyword(s):  
Mass Movement ◽  
Lesser Himalaya ◽  
Kumaun Lesser Himalaya ◽  
Movement Activities

Mesoscopic and magnetic fabrics in arcuate igneous bodies: an example from the Mandi-Karsog pluton, Himachal Lesser Himalaya

2010 ◽  
Vol 147 (5) ◽  
pp. 652-664 ◽  
Author(s):  
R. JAYANGONDAPERUMAL ◽  
A. K. DUBEY ◽  
K. SEN
Keyword(s):  
Host Rock ◽  
Magnetic Fabric ◽  
Lesser Himalaya ◽  
Himalayan Orogeny ◽  
Magnetic Fabrics ◽  
Himachal Lesser Himalaya ◽  
Shear Sense ◽  
Magmatic Fabric ◽  
Extension Fracture ◽  
Shear Sense Indicators

AbstractField, microstructural and anisotropy of magnetic susceptibility (AMS) data from the Palaeozoic Mandi-Karsog pluton in the Lesser Himalayan region reveal a concordant relationship between fabric of the Proterozoic host rock and the granite. The pluton displays a prominent arcuate shape on the geological map. The margin-parallel mesoscopic and magnetic fabrics of the granite and warping of the host rock fabric around the pluton indicate that this regional curvature is either synchronous or pre-dates the emplacement of the granite body. Mesoscopic fabric, magnetic fabric and microstructures indicate that the northern part of the pluton preserves its pre-Himalayan magmatic fabric while the central and southern part shows tectonic fabric related to the Tertiary Himalayan orogeny. The presence of NW–SE-trending aplitic veins within the granite indicates a post-emplacement stretching in the NE–SW direction. Shear-sense indicators in the mylonites along the margin of the pluton suggest top-to-the-SW shearing related to the Himalayan orogeny. Based on these observations, it is envisaged that the extension that gave rise to this rift-related magmatism had a NE–SW trend, that is, normal to the trend of the aplite veins. Subsequently, during the Himalayan orogeny, compression occurred along this same NE–SW orientation. These findings imply that the regional curvature present in the Himachal Lesser Himalaya is in fact a pre-Himalayan feature and the pluton has formed by filling a major pre-Himalayan arcuate extension fracture.

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