Geochemical constraints on komatiite volcanism from Sargur Group Nagamangala greenstone belt, western Dharwar craton, southern India: implications for Mesoarchean mantle evolution and continental growth

We present field, petrographic, major and trace element data for komatiites and komatiite basalts from Sargur Group Nagamangala greenstone belt, western Dharwar craton. Field evidences such as crude pillow structure indicate their eruption in a marine environment whilst spinifex texture reveals their komatiite nature. Petrographic data suggest that the primary mineralogy has been completely altered during post-magmatic processes associated with metamorphism corresponding to greenschist to lower amphibolite facies conditions. The studied komatiites contain serpentine, talc, tremolite, actinolite and chlorite whilst tremolite, actinolite with minor plagioclase in komatiitic basalts. Based on the published Sm-Nd whole rock isochron ages of adjoining Banasandra komatiites (northern extension of Nagamangala belt) and further northwest in Nuggihalli belt and Kalyadi belt we speculate ca. 3.2–3.15 Ga for komatiite eruption in Nagamangala belt. Trace element characteristics particularly HFSE and REE patterns suggest that most of the primary geochemical characteristics are preserved with minor influence of post-magmatic alteration and/or contamination. About 1/3 of studied komatiites show Al-depletion whilst remaining komatiites and komatiite basalts are Al-undepleted. Several samples despite high MgO, (Gd/Yb)N ratios show low CaO/Al2O3 ratios. Such anomalous values could be related to removal of CaO from komatiites during fluid-driven hydrothermal alteration, thus lowering CaO/Al2O3 ratios. The elemental characteristics of Al-depleted komatiites such as higher (Gd/Yb)N (>1.0), CaO/Al2O3 (>1.0), Al2O3/TiO2 (<18) together with lower HREE, Y, Zr and Hf indicate their derivation from deeper upper mantle with minor garnet (majorite?) involvement in residue whereas lower (Gd/Yb)N (<1.0), CaO/Al2O3 (<0.9), higher Al2O3/TiO2 (>18) together with higher HREE, Y, Zr suggest their derivation from shallower upper mantle without garnet involvement in residue. The observed chemical characteristics (CaO/Al2O3, Al2O3/TiO2, MgO, Ni, Cr, Nb, Zr, Y, Hf, and REE) indicate derivation of the komatiite and komatiite basalt magmas from heterogeneous mantle (depleted to primitive mantle) at different depths in hot spot environments possibly with a rising plume. The low content of incompatible elements in studied komatiites suggest existence of depleted mantle during ca. 3.2 Ga which in turn imply an earlier episode of mantle differentiation, greenstone volcanism and continental growth probably during ca. 3.6–3.3 Ga which is substantiated by Nd and Pb isotope data of gneisses and komatiites in western Dharwar craton (WDC)

Three-dimensional field perspective on deformation, flow, and growth of the lower continental crust (Dharwar craton, India

The study of fabric development and juvenile batholith emplacement across the tilted crustal section of the Eastern Dharwar craton shows that horizontal, constrictional deformation affected large volumes of the midcrust and lower crust at the time of regional partial melting and magmatic accretion. Constriction is achieved by a combination of coeval shallow and steep planar fabrics sharing a common horizontal elongation direction, two sets of conjugate strike-slip shears, and extensional shear zones. The Eastern Dharwar craton illustrates an end-member deformation mode by which a particularly weakened lithosphere responds to shortening by developing distributed, horizontal plane strain on a crustal scale, resulting from the combination of crustal shortening and lateral gravity-driven flow. Thinning accompanying constrictional deformation is interpreted as compensating for juvenile magmatic accretion and thickening of greenstone belts and as acting to maintain a stable crustal thickness. Such a midcrustal to lower crustal deformation process may provide a resolution of the batholithic room problem in a softened crust submitted to lateral shortening and may explain nearly isobaric retrograde pressure-temperaturetime paths of high temperature - low pressure high-grade terrains

Plutonism and Precambrian Magmatism in India

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Age of younger tonalitic magmatism and granulitic metamorphism in the South Indian transition zone (Krishnagiri area); comparison with older Peninsular gneisses from the Gorur-Hassan area

A major episode of continental crust formation, associated with granulite facies metamorphism, occurred at 2.55-2.51 Ga and was related to accretional processes of juvenile crust. Dating of tonalitic-trondhjemitic, granitic gneisses and charnockites from the Krishnagiri area of South India indicates that magmatic protoliths are 2550-2530+/-5Ma, as shown by both U-Pb and Pb-207/Pb-206 single zircon methods. Monazite ages indicate high temperatures of cooling corresponding to conditions close to granulite facies metamorphism at 2510+/-10 Ma. These data provide precise time constraints and Sr-Nd isotopes confirm the existence of late tonalitic-granodioritic juvenile gneisses at 2550 Ma. Pb single zircon ages from the older Peninsular gneisses (Gorur-Hassan area) are in agreement with some previous Sr ages and range between 3200+/-20 and 3328+/-10 Ma. These gneisses were derived from a 3.3-3.5-Ga mantle source as indicated from Nd isotopes. They did not participate significantly in the genesis of the 2.55-Ga juvenile magmas. All these data, together with previous work, suggest that the 2.51-Ga granulite facies metamorphism occurred near the contact of the ancient Peninsular gneisses and the 2.55-2.52-Ga 'juvenile' tonalitic-trondhjemitic terranes during synaccretional processes (subduction, mantle plume?). Rb-Sr biotite ages between 2060 and 2340 Ma indicate late cooling probably related to the dextral major east-west shearing which displaced the 2.5-Ga juvenile terranes toward the west

The geology and petrogenesis of the southern closepet granite

The Archaean Closepet Granite is a polyphase body intruding the Peninsular Gneiss Complex and the associated supracrustal rocks. The granite out-crop runs for nearly 500 km with an approximate width of 20 to 25 km and cut across the regional metamorphic structure passing from granulite facies in the South and green schist facies in the north. In the amphibolite-granulite facies transition zone the granite is intimately mixed with migmatites and charnockite. Field observations suggests that anatexis of Peninsular gneisses led to the formation of granite melt, and there is a space relationship between migmatite formation, charnockite development and production and emplacement of granite magma. Based on texture and cross cutting relationships four major granite phases are recognized: (1) Pyroxene bearing dark grey granite; (2) Porphyritec granite; (3) Equigranular grey granite; and (4) Equigranular pink granite. The granite is medium to coarse grained and exhibit hypidiomorphic granular to porphyritic texture. The modal composition varies from granite granodiorite to quartz monzonite. Geochemical variation of the granite suite is consistent with either fractional crystallization or partial melting, but in both the cases biotite plus feldspar must be involved as fractionating or residual phases during melting to account trace element chemistry. The trace element data has been plotted on discriminant diagrams, where majority of samples plot in volcanic arc and within plate, tectonic environments. The granite show distinct REE patterns with variable total REE content. The REE patterns and overall abundances suggests that the granite suite represents a product of partial melting of crustal source in which fractional crystallization operated in a limited number of cases

Strain patterns, décollement and incipient sagducted greenstone terrains in the Archaean Dharwar craton (south India)

The Archaean Dharwar craton is characterized by two greenstone successions: the > 3 Ga Sargur Group and the 3.0-2.5 Ga Dharwar Supergroup. Examples of both successions are described from the region of Jayachamarajapura where they are also distinguished by different tectonic patterns. The younger greenstones have undergone only minor deformation and are only slightly metamorphosed and so provide a good case study of the relative behavior of greenstones in relation to their granite-gneiss country rocks. A detailed structural analysis indicates two strain fields associated with two deformational episodes: D1 and D2. The D1 episode produced dome-and-basin structures and affected merely the older greenstones and the gneisses. The mapped strain field is compatible with the hypothesis that it is associated with the development of diapiric-type gravitational instabilities. The D2 episode affects only the younger greenstone belt, which has the overall geometry of a complex syncline. It is discordant over a complex of gneisses and older greenstones that was deformed during the D1 episode. The base of the discordant cover sequence is tectonized and constitutes a décollement surface. Kinematic criteria at this surface have opposite sense and converge towards the belt axis. These structural features are interpreted in terms of progressive deformation compatible with the incipient development of a sagducting trough. These results are consistent with those obtained from other parts of the craton, where the tectonic evolution appears to reflect mainly relative vertical displacements facilitated by the reheating of continental crust during two major Archaean tectonometamorphic episodes. Copyright © 1996 Elsevier Science Ltd

Effect of Alkaline Treatment on Mechanical and Thermal Properties Oftypha Angustifolia Fiber Reinforced Composites

Sustainable development is increasingly becoming a priority of governments and businered which is driven by growing environmental awareness. Much academic research explores new ways to create greener and environmentally friendlier materials for variety of aplications ranging from aeronautic, automotive and construction industry. The natural fibre reinforced composite has the advantage of being light weight, availability, strong, cheap, safe, ease of recycling, sustainability, renewability hermal and acoustic insulation, saving of fabrication energy and carbon dioxide neutrality. The composites are molded with unsaturated polyester resin matrix and reinforced with natural fibre. Five identical specimens are prepared for each fibre content. In this study, mechanical properties of composite such as tensile strength, tensile modulus were measured using universal testing machine. Guarded hot plate apparatus was used to measure the thermal conductivity of natural fibre typha angustifolia reinforced composite.. The results shows that mechanical properties, increased as fiber content increased. Thermal conductivity of composite is in the range of 0.168 w/m k to 0.187 w/m k and thermal conductivity decreased about 11.3% as fiber content increased. The newly developed composite material has lower thermal conductivity and is used as an insulating material to save energy

Petrology and geochemitstry of late Archaean granitoids in the northern part of EDC, Southern India: implications for transitional geodynamic setting

The results of field, petrographic and geochemical work of the granitoids of Hutti-Gurgunta area in the northern part of Eastern Dharwar Craton (EDC) is presented in this paper. This crustal section comprises polyphase banded to foliated TTG gneisses, middle amphibolite facies Gurgunta schist belt and upper greenschist facies Hutti schist belt and abundant granite plutons. The focus of the present study is mainly on basement TTG gneisses and a granite pluton (∼ 240 sq km areal extent), to discuss crustal accretion processes including changing petrogenetic mechanism and geodynamic setting. The TTGs contain quartz, plagioclase, lesser K-feldspar and hornblende with minor biotite while the granite contain quartz, plagioclase, K-feldspar and hornblende. Late stage alteration (chloritisation, sericitisation and epidotisation) is wide spread in the entire area. A huge synplutonic mafic body which is dioritic to meladioritic in composition injects the granite and displays all stages of progressive mixing and hybridization. The studied TTGs and granite show distinct major and trace element patterns. The TTGs are characterized by higher SiO2, high Al2O3, and Na2O, low TiO2, Mg#, CaO, K2O and LILE, and HFS elements compared to granite. TTGs define strong trondhjemite trend whilst granite shows calc-alkaline trend. However, both TTGs and granite show characteristics of Phanerozoic high-silica adakites. The granite also shows characteristics of transitional TTGs in its high LILE, and progressive increase in K2O with differentiation. Both TTGs and granite define linear to sub-linear trends on variation diagrams. The TTGs show moderate total REE contents with fractionated REE patterns (La/YbN =17.73–61.73) and slight positive or without any significant Eu anomaly implying little amount of amphibole or plagioclase in residual liquid. On the other hand, the granite displays poor to moderate fractionation of REE patterns (La/YbN = 9.06–67.21) without any significant Eu anomaly. The TTGs have been interpreted to be produced by low-K basaltic slab melting at shallow depth, whereas the granite pluton has been formed by slab melting at depth and these melts interacted with peridotite mantle wedge. Such changing petrogenetic mechanisms and geodynamic conditions explain increase in the contents of MgO, CaO, Ni and Cr from 2700 Ma to 2500 Ma granitoids in the EDC

Single Chip Solution with1-Wire Communication Protocol to Interface Digital Transducers to Sensor Networks

A virtual laboratory application setup is used to control and monitorremotely the operation of several sensor nodes placed at different geographicallocations. In this paper, we present the design of a generalized, low-cost and reconfigurablesmart sensor node using a Zigbee with a Field-Programmable Gate Array(FPGA) that embeds all processing and communication functionalities based on theIEEE 1451 family of standards with communication taking place through a 1-wireprotocol. The architecture of the sensor node is based on the single chip concept thatincludes communication, processing and transducer control functionalities. Theproposed architecture reduces the physical size, power and increases speedup ofprocessing due to inter-module communication. Results indicate the accuracy of theproposed system is tested with a temperature sensor which has 1-wire protocol

Late Archean crust-​mantle interactions: geochemistry of LREE-​enriched mantle derived magmas. Example of the Closepet batholith, southern India

The Closepet batholith in South India is generally considered as a typical crustal granite emplaced 2.5 Gyr ago and derived through partial melting of the surrounding Peninsular Gneisses (3.3-​3.0 Gyr)​. In the field, it appears as a composite batholith made up of at least two groups of intrusions. An early SiO2-​poor group (clinopyroxene quartz-​monzonite and porphyritic monzogranite) is located in the central part of the batholith. These rocks display a narrow range in both initial 87Sr​/86Sr ratio (Sri, 0.7017-​0.7035) and εNd (-​0.9 to -​4.1)​. A later SiO2-​rich group (equigranular gray and pink granites) is located along the interface between the SiO2-​poor group and the Peninsular Gneisses. They progressively grade into migmatized Peninsular Gneisses, thus indicating their anatectic derivation. Their isotopic characteristics vary over a wide range (Sri = 0.7028-​0.7336 and εNd values from -​2.7 to -​8.3, at 2.52 Gyr)​. Field and geochronol. evidence shows that the two groups are broadly contemporaneous (2.518-​2.513 Gyr) and mech. mixed. This observation is supported by the chem. data that display well defined mixing trends in the εSr vs εNd and elemental variation diagrams. The continuous chem. variation of the two magmatic bodies is interpreted in terms of interaction and mixing of two unrelated end-​members derived from different source regions (enriched peridotitic mantle and Peninsular Gneisses)​. It is proposed that the intrusion of mantle-​derived magmas into mid-​crustal levels occurred along a transcurrent shear zone; these magmas supplied addnl. heat and fluids that initiated anatexis of the surrounding crust. During this event, large-​scale mixing occurred between mantle and crustal melts, thus generating the composite Closepet batholith. The mantle-​derived magmatism is clearly assocd. with granulite-​facies metamorphism 2.51 ± 0.01 Gyr ago. Both are interpreted as resulting from a major crustal accretion event, possibly related to mantle plume activity