Relevant bibliographies by topics / Leptynite

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Academic literature on the topic 'Leptynite'

Author: Grafiati
Published: 4 June 2021
Last updated: 18 February 2022

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Journal articles on the topic "Leptynite"

1

DOBMEIER, CHRISTOPH, and MICHAEL M. RAITH. "On the origin of ‘arrested’ charnockitization in the Chilka Lake area, Eastern Ghats Belt, India: a reappraisal." Geological Magazine 137, no. 1 (January 2000): 27–37. http://dx.doi.org/10.1017/s0016756800003472.

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Arrested-type charnockite formation occurs in an assemblage of high-grade gneisses at several localities of the Chilka Lake area that belongs to the Proterozoic Eastern Ghats Belt of India. The isolated ellipsoidal domains are found exclusively in leucogranite (leptynite) bands that intruded lit-par- lit interbanded granulite-grade supracrustal and intermediate igneous rocks (khondalite–enderbite). Macrostructures and microfabrics document a multiple deformation of the rock assemblage under high-grade conditions. The intrusion of the leucogranitic melts separates a first episode of deformation, D1, from a younger progressive deformation, D2–D4. A transpressive regime and inhomogeneous deformation is indicated for D2–D4 by the associated structures and fabrics. But quartz c-axis patterns show that pure shear prevailed during the closing stages of deformation. The spatial distribution and orientation of the ellipsoidal charnockite domains within the host leptynite and the orientation pattern of orthopyroxene c-axes inside the domains provide evidence for a synkinematic in situ formation of the domains during D3, through partial breakdown of the leptynite assemblage (Bt+Grt+Qtz+Fl1[rlhar ]Opx+Fsp+Ilm+Fl2/L). Local fluid migration along steep foliation planes associated with large-scale D3 folds triggered the reaction. Orthopyroxene blastesis was confined to the centre of the domains, and an envelope formed in which the residing fluid caused secondary intergranular formation of chlorite, ore and carbonate, imparting the domains' typical greenish-brown charnockite colour. The shape of the envelope, which varies from prolate in limbs to oblate in hinges of D3 folds, is responsive to the local stress field. Comparison of chemical rock compositions supports the in situ formation of charnockite in leptynite. Subtle compositional differences are controlled by the changing mineralogy. Compared to the host leptynite, the charnockite domains are enriched in K2O, Ba, Rb and Sr, but depleted in FeO*, MnO, Y and Zr. The data obtained in this study provide conclusive evidence that the ellipsoidal charnockite domains do not represent remnants of stretched enderbite layers as proposed by Bhattacharya, Sen & Acharyya, but formed in situ in the leptynite as a result of localized synkinematic fluid migration late in the deformation history.
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2

Luo, Xuedong, Nan Jiang, Mingyang Wang, and Ying Xu. "Response of Leptynite Subjected to Repeated Impact Loading." Rock Mechanics and Rock Engineering 49, no. 10 (December 21, 2015): 4137–41. http://dx.doi.org/10.1007/s00603-015-0896-6.

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3

PRAKASH, DIVYA, DEEPAK, PRAVEEN CHANDRA SINGH, CHANDRA KANT SINGH, SUPARNA TEWARI, MAKOTO ARIMA, and HARTWIG E. FRIMMEL. "Reaction textures and metamorphic evolution of sapphirine–spinel-bearing and associated granulites from Diguva Sonaba, Eastern Ghats Mobile Belt, India." Geological Magazine 152, no. 2 (August 14, 2014): 316–40. http://dx.doi.org/10.1017/s0016756814000399.

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AbstractThe Diguva Sonaba area (Vishakhapatnam district, Andhra Pradesh, South India) represents part of the granulite-facies terrain of the Eastern Ghats Mobile Belt. The Precambrian metamorphic rocks of the area predominantly consist of mafic granulite (±garnet), khondalite, leptynite (±garnet, biotite), charnockite, enderbite, calc-granulite, migmatic gneisses and sapphirine–spinel-bearing granulite. The latter rock type occurs as lenticular bodies in khondalite, leptynite and calc-granulite. Textural relations, such as corroded inclusions of biotite within garnet and orthopyroxene, resorbed hornblende within pyroxenes, and coarse-grained laths of sillimanite, presumably pseudomorphs after kyanite, provide evidence of either an earlier episode of upper-amphibolite-facies metamorphism or they represent relics of the prograde path that led to granulite-facies metamorphism. In the sapphirine–spinel-bearing granulite, osumilite was stable in addition to sapphirine, spinel and quartz during the thermal peak of granulite-facies metamorphism but the assemblage was later replaced by Crd–Opx–Qtz–Kfs-symplectite and a variety of reaction coronas during retrograde overprint. Variable amounts of biotite or biotite+quartz symplectite replaced orthopyroxene, cordierite and Opx–Crd–Kfs–Qtz-symplectite at an even later retrograde stage. Peak metamorphic conditions of c. 1000°C and c. 12 kbar were computed by isopleths of XMg in garnet and XAl in orthopyroxene. The sequence of reactions as deduced from the corona and symplectite assemblages, together with petrogenetic grid and pseudosection modelling, records a clockwise P–T evolution. The P–T path is characteristically T-convex suggesting an isothermal decompression path and reflects rapid uplift followed by cooling of a tectonically thickened crust.
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Bhattacharya, S., S. K. Sen, and A. Acharyya. "Structural evidence supporting a remnant origin of patchy charnockites in the Chilka Lake area, India." Geological Magazine 130, no. 3 (May 1993): 363–68. http://dx.doi.org/10.1017/s0016756800020045.

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AbstractDark patches of charnockitic rocks characterized by orthopyroxene occur within garnetiferous granite gneisses (leptynites) in a granulite-migmatite suite around the Chilka Lake, Orissa, within the Eastern Ghats belt in the Indian Precambrian. Analysis of structures of different scales observed in this terrain establishes the presence of three phases of deformation. S1 is pervasive in the metapelitic granulites (mainlykhondalite), while in the migmatite complex composed of leptynites, charnockites and quartzofeldspathic veins, S1 is present exclusively within the charnockite lenses and bands, and shows different stages of obliteration in the associated leptynites. Thus, the charnockite patches must be earlier than the surrounding migmatitic rocks. The charnockite patches and the surrounding leptynitic gneisses are chemically quite different and the two rock types are not related by any prograde or retrograde transformation. The shapes and disposition of charnockite patches in the mixed exposures are found to be largely controlled by the third phase of folding and locally associated shearing. The kinematics of this late deformation are not favourable for fluid ingress from deeper levels.
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Datta, Niloy Ranjan, P. Sengupta, Aparajita Gangopadhyay, and Sushmita Sarkar. "Incipient Charnockite Formation in Leptynite from Vizianagaram, Andhra Pradesh: Implication for Pan-African (?) Crustal Reworking in the Eastern Ghats Belt." Gondwana Research 4, no. 4 (October 2001): 603–4. http://dx.doi.org/10.1016/s1342-937x(05)70404-4.

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6

Scali, Valerio, Liliana Milani, and Marco Passamonti. "Revision of the stick insect genus Leptynia: description of new taxa, speciation mechanism and phylogeography." Contributions to Zoology 81, no. 1 (January 31, 2012): 25–42. http://dx.doi.org/10.1163/18759866-08101002.

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Leptynia specimens were analyzed by karyotype analysis, mitochondrial gene sequencing and SEM of bodies and eggs. Here we describe a new species, Leptynia annaepaulae, and three subspecies of L. attenuata Pantel (L. attenuata attenuata, L. attenuata iberica, L. attenuata algarvica). The phylogeny of the genus Leptynia is congruent with a karyotype trend toward a reduction of chromosome number and the shift from the shared XX/X0 sex chromosome formula to the unusual XX/XY one. Chromosome repatterning appears to occur ahead of genetic differentiation, following a chromosome model of cladogenesis. Chromosome and genetic differentiation, in turn, appears to precede morphological distinction, thus realizing a condition of incipient species for most of the Leptynia taxa. Actually, morphological analyses revealed that, only rarely clear cut differences exist among and between taxa, while, more often, just trends in the differentiating traits occur, since the investigated characters generally suffer from some overlapping: In this study, only the 10th:9th ratio value and the subanal vomer appear to be diagnostic for L. annaepaulae against all other Leptynia taxa. As a consequence, the subanal vomer as well as cercus tooth features with egg chorion traits are not sharply diagnostic for the remaining co-generic taxa; however, comparisons are quite helpful in reducing uncertainties. A likely phylogeographic scenario for the genus supports that Leptynia ancestors spread from Northern Africa into Southern Spain where an ancestral taxon originated L. annaepaulae (2n = 40/39, XX/X0, with 2 large dibrachial pairs). Later on, a northbound colonization, should have originated L. caprai (2n = 40/39, XX/X0, all acrocentrics), from which L. montana (2n = 38, XX/X0) and L. attenuata (2n = 36, XY/XX) originated; supporting instances of chromosome repatterning have been actually observed. In this connection we like to stress that, particularly in stick insects, androgenesis has been a preferential pathway to quickly make homozygous those odd chromosome rearrangements likely responsible for low fitness in the heterozygotes.
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7

Han, Zuozhen, Jingjing Li, Zhigang Song, Guyao Liu, Wenjian Zhong, Lihua Gao, and Qingxiang Du. "Geochemistry and Zircon U-Pb-Hf Isotopes of Metamorphic Rocks from the Kaiyuan and Hulan Tectonic Mélanges, NE China: Implications for the Tectonic Evolution of the Paleo-Asian and Mudanjiang Oceans." Minerals 10, no. 9 (September 22, 2020): 836. http://dx.doi.org/10.3390/min10090836.

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The Late Paleozoic–Early Mesozoic tectonic evolution of the Changchun-Yanji suture (CYS) was mainly associated with the Paleo-Asian and Mudanjiang tectonic regimes. However, the spatial and temporal overprinting and variations of these two regimes remains are still dispute. In order to evaluate this issue, in this contribution, we present new zircon U-Pb ages and a whole-rock geochemical and zircon Hf isotopic dataset on a suite of metamorphic rocks, including gneisses, actinolite schist, leptynites, and biotite schists, from tectonic mélanges in northern Liaoning and central Jilin provinces, NE China. Based on zircon LA-ICP-MS U-Pb dating results, protoliths show wide ranges of aging spectrum, including Paleoproterozoic (2441 Ma), Early Permian (281 Ma), Late Permian (254 Ma), and Late Triassic (230 Ma). The Permian protoliths of leptynites from the Hulan Tectonic Mélange (HLTM) and gneisses from the Kaiyuan Tectonic Mélange (KYTM) exhibit arc-related geochemical signatures, implying that the Paleo-Asian Ocean (PAO) did not close prior to the Late Permian. The Late Triassic protoliths of gneisses from the KYTM, in combination with previously reported coeval igneous rocks along the CYS, comprises a typical bimodal igneous suite in an E–W-trending belt, suggesting a post-orogenic extensional environment. Consequently, we infer that the final closure of the PAO took place during the Early–Middle Triassic. The Early Permian protoliths of biotite schists from the HLTM are alkali basaltic rocks and contain multiple older inherited zircons, which, in conjunction with the geochemical features of the rocks, indicate that they were generated in a continental rift related to the initial opening of the Mudanjiang Ocean (MO). Data from this contribution and previous studies lead us to conclude that the MO probably opened during the Middle Triassic, due to the north–south trending compression caused by the final closure of the PAO.
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Rao, P. V. Nageswara, A. T. Rao, and M. Yoshida. "Geochemical characters of leptynites from the Visakhapatnam area in the Eastern Ghats granulite terrane, India." Journal of Southeast Asian Earth Sciences 14, no. 3-4 (October 1996): 199–207. http://dx.doi.org/10.1016/s0743-9547(96)00058-x.

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9

Scali, V., E. Coluccia, F. Deidda, C. Lobina, A. M. Deiana, and S. Salvadori. "Co-localization of ribosomal and telomeric sequences in Leptynia (Insecta: Phasmatodea)." Italian Journal of Zoology 83, no. 3 (July 2, 2016): 285–90. http://dx.doi.org/10.1080/11250003.2016.1219403.

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10

Passamonti, Marco, Barbara Mantovani, and Valerio Scali. "Karyotype and Allozyme Characterization of the Iberian Leptynia attenuata Species Complex (Insecta Phasmatodea)." Zoological Science 16, no. 4 (August 1999): 675–84. http://dx.doi.org/10.2108/zsj.16.675.

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Dissertations / Theses on the topic "Leptynite"

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Zonou, Siaka. "Les formations leptyno-amphibolitiques et le complexe volcanique et volcano-sédimentaire du proterozoïque inférieur de Bouroum-Nord (Burkina Faso, Afrique de l'Ouest) : Étude pétrographique, géochimique, approche pétrogénétique et évolution géodynamique." Nancy 1, 1987. http://www.theses.fr/1987NAN10325.

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On distingue deux méga ensembles : les formations dabakaliennes et birrimiennes. Les formations dabakaliennes sont caractérisées par une énergique déformation pénétrative, synchrone d'un métamorphisme largement instauré dans le faciès amphibolite mais devenant rétrograde sous le joug de l'orogénèse éburnéenne. Les formations birrimiennes, dont l'étude, beaucoup plus complète, d'ordre stratigraphique, pétrographique, minéralogique, et géochimique, permet la propositin d'un schéma d'évolution, géodynamique du birrimien
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Alexandrov, Pavel. "Géochronologie U/Pb et ⁴⁰ Ar/ ³⁹ Ar de deux segments de la chaîne varisque : le haut limousin et les pyrénées orientales." Vandoeuvre-les-Nancy, INPL, 2000. http://www.theses.fr/2000INPL062N.

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Différents corps métamorphiques et magmatiques dans leLlimousin et dans les Pyrénées orientales ont été datés par la méthode u/pb à la microsonde ionique et 4 0ar/ 3 9ar sur monograin. Les résultats permettent d'avancer de nouvelles idées sur l'évolution orogénique de ces segments de la chaîne varisque. 1. Pyrénées orientales. L'orthogneiss de canigou-caranca a été daté par la méthode u/pb à la microsonde ionique sur zircons selectionnes. Les âges 2 0 6pb/ 2 3 8u des trois echantillons analyses varient entre 460 et 500 ma. Cet âge invalide le modèle classique de disposition en socle et couverture des séries métamorphiques. 2. Limousin. Le protolithe de la leptynite de vergonzac qui fait partie de l'unité supérieure des gneiss, a été daté à 525 6 ma (u/pb sur zircons a la microsonde ionique). Cet âge est compatible avec les âges des autres unités métamorphiques du Limousin. La mise en place du leucogranite péralumineux de blond a été datée à 319 7 ma (u/pb sur zircons a la microsonde ionique). Les âges 4 0ar/ 3 9ar sur muscovites de cette intrusion varient entre 311 et 306 ma. Ils sont interprétés non pas comme des âges de refroidissement, mais comme caractérisant une activite magmatique et hydrothermale importante. Les granitoides sous couverture du seuil du Poitou ont donné des âges 4 0ar/ 3 9ar sur biotites et amphiboles entre 350 et 345 ma. Une modélisation numérique a permis de les interpréter en termes de refroidissement et d'exhumation. Les minéralisations a w et sn de moulin-barret et de puy-les-vignes ont fourni des âges de 324 ma, ce qui implique l'existance d'un épisode de minéralisations au namurien. Une synthèse de tous les résultats permet de proposer une exhumation et une extension tardi-orogenique précoce, respectivement vers 340 ma et 320 ma. 3. Méthodologie. Quelques réflexions sur la calibration des analyses u/pb à la microsonde ionique sont proposées. La forme des spectres d'âge 4 0ar/ 3 9ar, leur signification en termes d'âge et l'interprétation des âges 4 0ar/ 3 9ar sont abordées.
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Schürch, Marie Louise. "Les ophiolites de la zone du Versoyen : témoins d'un bassin à évolution métamorphique complexe : Province d'Aoste (Italie), Savoie (France)." Phd thesis, 1987. http://tel.archives-ouvertes.fr/tel-00795566.

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Située à cheval sur la frontière franco-italienne, à proximité du col du Petit-Saint-Bernard, la zone du Versoyen est pincée entre le houiller briançonnais et les massifs cristallins externes, et se rattache structuralement à la zone des Brèches de Tarentaise (extrémité SW de la zone valaisane). Elle est constituée, d'écailles de serpentinites associées à des lentilles gneissiques, et d'un ensemble volcano-sédimentaire caractérisé par des filons-couches basaltiques différenciés, intrusifs dans une série pélitique d'âge Crétacé inférieur à moyen. Dans les parties sommitales du bâti, un débit en coussins est souvent observé. La trilogie ophiolitique classique n'est pas complète, en effet, sont absents les termes mafiques grenus et le "sheeted dike complexe" proprement dit (qui, en l'occurrence, pourrait être représenté par les sills). L'environnement géotectonique, dans lequel le complexe ophiolitique s'est développé, a pu être mis en evidence grâce à des diagrammes de discrimination géochimiques; il s'agirait d'un petit bassin, engendré dans une faille transformante, de type golfe de Californie. D'autre part, ces ophiolites et leurs sédiments associés ont subi une histoire métamorphique complexe qui a pu être retracée, grâce à une étude pétrographique détaillée et à l'analyse par microsonde des minéraux clés, selon le scénario suivant: Lors de la mise en place des sills se produit un métamorphisme de contact, à caractère thermique et hydrothermal, qui a eu lieu aux contacts sills - sédiments encaissants; il a principalement engendré des roches porcelanées, les adinoles. Un métamorphisme de fond océanique a suivi probablement peu après, occasionnant une remobilisation importante d'éléments volatils et produisant également, en certains secteurs, une spilitisation. Ensuite la zone du Versoyen a ete affectée par le métamorphisme régional alpin, à caractère polyphasé, représenté par 3 faciès; le premier, le faciès éclogitique (déjà mentionné lors d'études précédentes, mais considéré jusqu'alors comme "metamorphisme transporté"), a pu être défini comme s'étant développé in situ". La découverte de l'omphacite dans plusieurs secteurs du Versoyen et l'extension géographique de l'apparition de la jadéite notamment, permettent de cerner les conditions P-T qui ont permis la cristallisation des paragenèses éclogitiques; elles se situent entre 7 et 16 kbars, et 300 et 600* C. Un contexte géodynamique inédit est envisagé, soit une zone de subduction avec, conjointement, des phénomènes de surpression, engendrées par un chevauchement,tectonique majeur. Les faciès métamorphiques qui ont suivi sont : le facies schistes bleus, cristallisant, lui aussi, dans des conditions de P-T relativement extrêmes, et le faciès schistes verts, nettement rétrograde. Une approche géochronologique a été tentée, par l'isochrone, calculée pour les glaucophanes, métamorphisme paroxysmal (HP-BT) à 65 ± 16 M.a. ,
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