93 research outputs found
Structural, kinematic and geochronologic evolution of the Himalayan fold-thrust belt in Kumaun, Uttaranchal, Northwest India
No full textElectronic Thesis or DissertationThe Lesser Himalaya is a key tectonostratigraphic zone of the Himalayan fold-thrust belt; however, its poorly defined chronostratigraphy and erroneous stratigraphic correlations hamper the determination of valid structural models. In Kumaun, northwest India, I reassess the tectonostratigraphic and structural architecture using U-Pb zircon geochronology, whole rock neodymium isotopes, and structural data to establish that rock in the Almora klippe and north of the Main Central thrust have Neoproterozoic (~900 Ma) detrital zircon ages and similar ε_Nd(0) (-7.6 to -11.8) values, which suggests that these two units are the same tectonostratigraphic unit, and that the Almora klippe is the southern continuation of the Main Central thrust or another thrust in the Greater Himalayan thrust system. However, north of the Almora klippe, detrital zircon age populations establish the presence of Palaeoproterozoic Lesser Himalayan rock [ca. 1600 Ma youngest zircon, ε_Nd(0)=-22.0] instead of the previous interpretation of Neoproterozoic rocks. South of the klippe, the Ramgarh-Munsiari thrust carries both the less metamorphosed Palaeoproterozoic and Neoproterozoic Lesser Himalayan rocks, in disagreement with the idea that only Neoproterozoic-Cambrian Lesser Himalayan rocks are present south of Almora klippe. U-Pb ages, Hf isotopes and whole rock trace element geochemical data coupled with detail mapping establish that the rocks in the Askot klippe belong to Paleoproterozoic Lesser Himalayan rock, and do not continue to the south as the rock in the Almora klippe. The Askot klippe consists of 1856.6±1.0 Ma granite-granodiorite gneiss, coeval 1869±12 Ma felsic volcanic rocks, and ca. 1820 Ma Berinag Formation quartzite. These rocks represent a small vestige of a Paleoproterozoic continental arc that formed on the northern margin of the northern Indian cratonic block during the Paleo-Mesoproterozoic amalgamation of the supercontinent Columbia. εHf(0) values from ca. 1850 Ma detrital zircons from the Berinag Formation quartzite (-9.6 to -1.1, with an average of -4.5) overlap with the εHf values of the ca. 1850 Ma granite-granodiorite gneiss of the Askot klippe [εHf(0)=-5.5 to -1.2, with an average of -2.7] and other ca. 1850 Ma arc-related granite gneiss [εHf(0)=-4.8 to -2.2, with an average of -4.0] within the Lesser Himalaya. Subchondritic εHf(0) values (1.1 to -4.9) of ca. 1850 Ma granite-granodiorite gneiss indicate pre-existing older crust, which underwent crustal reworking at ca. 1850 Ma. This revised chronostratigraphy along with new structural mapping provide the basis for a new structural model for the evolution of the fold-thrust belt in Kumaun that establishes the thrust system as a forward propagating system and contains a hinterland dipping duplex composed of Lesser Himalayan rocks. A balanced cross-section reveals a total minimum shortening estimate of 541-575 km or 79-80% between Main Frontal thrust and South Tibetan Detachment system, with the MCT accommodating 163-128 km, the RMT accommodating 112 km, the LHD accommodating 270 km, the MBT accommodating 8 km, and the Subhimalayan thrust system accommodating ~22 km. Adding the shortening from the Tethyan Himalaya from published work brings the total minimum shortening estimate for the Himalayan fold-thrust belt along this cross-section line to 674-751 km. The Ramgarh-Munsiari thrust is the roof thrust of the Lesser Himalayan duplex, and its footwall rocks, the Ramgarh, Berinag, Chiplakot and Munsiari Formations, are part of the same, once continuous stratigraphic unit that was dissected and turned into the Ramgarh-Munsiari thrust sheet and other thrust sheets in the Lesser Himalayan duplex
Sedimentation and Tectonics of Lower Cenozoic Sequences from Southeast of Shillong Plateau, India: Provenance History of the Assam-Bengal System, Eastern Himalayas
Get PDFThe present study area is located along the southeastern part of the Shillong Plateau in the eastern and southeastern part of the Meghalaya State and in the lower (southern) part of Assam State, northeast India. A continuous Eocene to Miocene sequence is exposed along the Jowai-Badarpur Road (NH-44). The study area is at the junction between Assam and Bengal basins. Detrital history from this area provides data pertaining to uplift and erosional history of the hinterland areas (i.e., Himalayas, Indo-Burma Ranges and Shillong Plateau).
Lower Cenozoic units from the study area bear signatures of the both orogenic belts and stable craton. Lower Eocene Tura and Sylhet sandstones are quartzose (Q98F2L0), which points to the Indian Craton as a potential source area. Sandstones from the late Eocene Kopili Formation are quartzolithic (Q73F4L23). Younger Oligocene and
Miocene sandstones are also quartzolithic, rich in unstable grains, suggesting derivation from adjacent orogenic belts.
Eocene sandstones are rich in opaque and ultra-stable heavy minerals (e.g., zircon, rutile, and tourmaline). Concentrations of unstable heavy minerals (e.g., amphibole, chrome-spinel, and serpentine) increase in Oligocene and Miocene strata. Progressively lower maturity indices of heavy mineral assemblages in up-section suggest that the orogenic fronts are getting closer.
Mineral chemistry of detrital tourmaline grains suggests that derivation from metapelites with a subordinate Li-poor granitoid source. The majority of the detrital tourmalines belong to the schorl-dravite series. Low Al, low Fe, and high Mg-bearing chrome spinels suggest derivation from Alpine-type peridotites, likely from the Indo-Burma Ranges (Naga ophiolites) to the east of the study area. Detrital garnet chemistry suggests a broad P-T range for source rock terranes.
Mudrock geochemical data suggest that the majority of the sediments were derived from recycled orogenic sources. Based on the chemical index of alteration, the intensity of weathering in the source area was moderate to high. Future research project in the area should explain the uplift history of source terranes using garnet and tourmaline chemistry and detrital geochronology
Fresh look at the LHC limits on scalar leptoquarks
Get PDFThe scalar-leptoquark (sLQ) parameter space is well explored experimentally.
The direct pair production searches at the LHC have excluded light sLQs almost
model agnostically, and the high- dilepton tail data have put strong
bounds on the leptoquark-quark-lepton Yukawa couplings for a wide range of sLQ
masses. However, these do not show the complete picture. Previously, Mandal
\emph{et al.} [Single productions of colored particles at the LHC: An example
with scalar leptoquarks, \href{https://doi.org/10.1007/JHEP07(2015)028}{J. High
Energy Phys. 07 (2015) 028}] showed how the dilepton-dijet data from the pair
production searches could give strong limits on these couplings. This was
possible by including the single-production contribution to the dilepton-dijet
signal. In this paper, we take a fresh look at the LHC limits on all sLQs by
following the same principle and combine all significant contributions -- from
pair and single productions, -channel sLQ exchange and its interference with
the Standard Model background -- to the final state and recast the
limits. We notice that the sLQ exchange and its interference with the
background processes play significant roles in the limits. The -recast limits are comparable to or, in some cases, significantly better
than the currently known limits (from high- dilepton data and direct
searches), i.e., the LHC data rules out more parameter space than what is
considered in the current literature. For the first time, we also show how
including the QED processes can noticeably improve the sLQ mass exclusion
limits from the QCD-only limits.Comment: 13 pages, 7 figures and 4 tables. The models are available at
https://github.com/rsrchtsm/LQ_Models. Same as the journal versio
Probing Color Octet Electrons at the LHC
No full text15 pages, 11 figures and 2 tablesModels with quark and lepton compositeness predict the existence of colored partners of the Standard Model leptons. In this paper we study the LHC phenomenology of a charged colored lepton partner, namely the color octet electron, . We explore various production mechanisms of the 's at the LHC. Assuming 100% branching ratio for the decay, , we estimate the LHC discovery potential for the 's. Our analysis shows that the LHC with 14 TeV center of mass energy and 100 fb (300 fb) of integrated luminosity can probe mass up to 3 TeV (3.4 TeV) for the compositeness scale of 5 TeV
Use of soil amendments in an integrated framework for adaptive resource management in agriculture and forestry
No full textAgricultural practices involving intensive applications of chemical fertilizers can be harmful to the environment. Soil amendments can serve as an alternative source of plant nutrients and simultaneously improve the physical, chemical and biological properties of soils. Many soil amendments are produced from organic and inorganic waste materials. The amendment application practices therefore not only support the agricultural productivity but also facilitate an environmental friendly disposal and recycling of the wastes. This also helps the farmers to reduce their cost of production. Most of the soil amendments supply nutrients to plants over a longer period of time in a slow release process. However, best management practices should be adapted in order to harness the optimum benefits of soil amendments in agricultural and forestry production systems. This chapter aims to present an overview of various soil amendments in relation to their already existing and/or potential applications for improving the productivity and health of soils
Probing compositeness with the CMS eejj & eej data
No full textQuark-lepton compositeness is a well-known beyond the Standard Model (SM) scenario with heavy exotic particles like leptoquarks (LQs) and leptogluons (LGs) etc. These particles can couple to leptons and jets simultaneously. In this letter, we use the recent CMS scalar LQ search data in the eejj and eej channels to probe this scenario. We recast the data in terms of a color octet partner of the SM electron (or a first generation spin-1/2 LG) that couples to an electron and a gluon via a dimension five operator suppressed by the quark–lepton compositeness scale (Λ). By combining different production processes of the color octet electron (e8) at the LHC, we use the CMS 8 TeV data to obtain a simultaneous bound on Λ and the mass of the e8 (Me8). We also study the reach of the 13 TeV LHC to discover the e8 and interpret the required luminosity in terms of Me8 and Λ
Soil mineralogical perspective on immobilization/mobilization of heavy metals
No full textKnowledge on the fate and transport of heavy metals is essential for predicting the environmental impact of metal contamination on agricultural soils. This chapter presents an overview of various factors that are involved in controlling the retention and mobility of heavy metals in soils with a special reference to soil mineralogy. The bioavailability of most elements, in particular heavy metals, in soils is governed by adsorption-desorption, complexation, precipitation and ionexchange processes. The most important surfaces involved in metal adsorption in soils are active inorganic colloids such as clay minerals, oxides and hydroxides of metals, metal carbonates and phosphates and organic colloids. In addition to soil mineralogy, other important parameters controlling heavy metal retention and their distribution are soil texture, structure, pH, redox condition, cation and anion concentration, ionic strength, organic matter, microbial and root activity and climatic conditions. However, the ultimate fate of elements depends on a combination of several factors that are working together in the soil system. Finally, several remediation strategies have also been highlighted based on the fundamental principles of metal immobilization on mineral containing soil amendments
Addressing the R-D(*) anomalies with an S-1 leptoquark from SO(10) grand unification
Get PDFMotivated by the R-D(*) anomalies, we investigate an SO(10) grand unification scenario where a charge -1/3 scalar leptoquark (S-1) remains as the only new physics candidate at the TeV scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from the same ten-dimensional real scalar multiplet in the SO(10) grand unification framework taking its mass close to the electroweak scale. We explicitly show how the gauge coupling unification is achieved with only one intermediate symmetrybreaking scale at which the Pati-Salam gauge group is broken into the SM group. We investigate the phenomenological implications of our scenario and show that an S-1 with a specific Yukawa texture can explain the R-D(*) anomalies. We perform a multiparameter scan considering the relevant flavor constraints on R-D(*), F-L(D*), P-tau(D*) and R-K(*)(vv) as well as the constraint coming from the Z -> tau tau decay and the latest Dr resonance search data at the LHC. Our analysis shows that a single leptoquark solution to the observed R-D(*) anomalies with S-1 is still a viable solution
LHC signatures of warped-space vectorlike quarks
Get PDF33 pages, 18 figures, 10 tablesWe study the LHC signatures of TeV scale vectorlike quarks , and with electromagnetic charges -1/3, 2/3 and 5/3 that appear in many beyond the standard model (BSM) extensions. We consider warped extradimensional models and analyze the phenomenology of such vectorlike quarks that are the custodial partners of third generation quarks. In addition to the usually studied pair-production channels which depend on the strong coupling, we put equal emphasis on single production channels that depend on electroweak couplings and on electroweak symmetry breaking induced mixing effects between the heavy vectorlike quarks and standard model quarks. Although the motivation is from warped models, we present many of our results model-independently
Hunting for scalar leptoquarks with boosted tops and light leptons
No full textThe LHC search strategies for leptoquarks that couple dominantly to a top quark are different than for the ones that couple mostly to the light quarks. We consider charge 1/3 (phi(1)) and 5/3 (phi(5)) scalar leptoquarks that can decay to a top quark and a charged lepton (tl) giving rise to a resonance system of a boosted top and a high-p(T) lepton. We introduce simple phenomenological models suitable for bottom-up studies and explicitly map them to all possible scalar leptoquark models within the Buchmuller-Ruckl-Wyler classifications that can have the desired decays. We study pair and single productions of these leptoquarks. Contrary to the common perception, we find that the single production of top-philic leptoquarks phi = {phi(1), phi(5)} in association with a lepton and jets could be significant for order one phi tl coupling in certain scenarios. We propose a strategy of selecting events with at least one hadronic-top and two high-p(T) same flavor opposite sign leptons. This captures events from both pair and single productions. Our strategy can significantly enhance the LHC discovery potential especially in the high-mass region where single productions become more prominent. Our estimation shows that a scalar leptoquark as heavy as similar to 1.7 TeV can be discovered at the 14 TeV LHC with 3 ab(-1) of integrated luminosity in the tll + X channel for 100% branching ratio in the phi -> tl decay mode. However, in some scenarios, the discovery reach can increase beyond 2 TeV even though the branching ratio comes down to about 50%
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