1,360 research outputs found
Author response: India and China in Africa: a comparative perspective of the oil industry by Raj Verma
No full textEarlier this month Ian Taylor reviewed India and China in Africa, a new book about Asian engagement in the West African oil industry. Here, the book’s author Raj Verma responds to Taylor’s comments, outlining the rationale and evidence for the framework used in the study. India and China in Africa: A comparative perspective of the oil industry. Raj Verma. London: Routledge. 2017
Fifteen New Discriminant-function-based Multi-dimensional Robust Diagrams For Acid Rocks And Their Application To Precambrian Rocks
No full textFor the discrimination of four tectonic settings of island arc, continental arc, within-plate (continental rift and ocean island together), and collision, we present three sets of new diagrams obtained from linear discriminant analysis of natural logarithm transformed ratios of major elements, immobile major and trace elements, and immobile trace elements in acid magmas. The use of discordant outlier-free samples prior to linear discriminant analysis had improved the success rates by about 3% on the average. Success rates of these new diagrams were acceptably high (about 69% to 97% for the first set, about 69% to 99% for the second set, and about 60% to 96% for the third set). Testing of these diagrams for acid rock samples (not used for constructing them) from known tectonic settings confirmed their overall good performance. Application of these new diagrams to Precambrian case studies provided the following generally consistent results: a continental arc setting for the Caribou greenstone belt (Canada) at about 3000. Ma, São Francisco craton (Brazil) at about 3085-2983. Ma, Penakacherla greenstone terrane (Dharwar craton, India) at about 2700. Ma, and Adola (Ethiopia) at about 885-765. Ma; a transitional continental arc to collision setting for the Rio Maria terrane (Brazil) at about 2870. Ma and Eastern felsic volcanic terrain (India) at about 2700. Ma; a collision setting for the Kolar suture zone (India) at about 2610. Ma and Korpo area (Finland) at about 1852. Ma; and a within-plate (likely a continental rift) setting for Malani igneous suite (India) at about 745-700. Ma. These applications suggest utility of the new discrimination diagrams for all four tectonic settings. In fact, all three sets of diagrams were shown to be robust against post-emplacement compositional changes caused by analytical errors, element mobility related to low or high temperature alteration, or Fe-oxidation caused by weathering. © 2013 Elsevier B.V.168-169113123Agrawal, S., Discrimination between late-orogenic, post-orogenic, and anorogenic granites by major element compositions (1995) Journal of Geology, 103, pp. 529-537Agrawal, S., Geochemical discrimination diagrams: a simple way of replacing eye-fitted boundaries with probability based classifier surfaces (1999) Journal of the Geological Society of India, 54, pp. 335-346Agrawal, S., Verma, S.P., Comment on "Tectonic classification of basalts with classification trees" by Pieter Vermeesch (2006) (2007) Geochimica et Cosmochimica Acta, 71, pp. 3388-3390Agrawal, S., Guevara, M., Verma, S.P., Discriminant analysis applied to establish major-element field boundaries for tectonic varieties of basic rocks (2004) International Geology Review, 46, pp. 575-594Agrawal, S., Guevara, M., Verma, S.P., Tectonic discrimination of basic and ultrabasic rocks through log-transformed ratios of immobile trace elements (2008) International Geology Review, 50, pp. 1057-1079Aitchison, J., (1986) The Statistical Analysis of Compositional Data, , Chapman and Hall, London, New York, (416 pp.)Barnett, V., Lewis, T., (1994) Outliers in Statistical Data, , John Wiley & Sons, Chichester, (584 pp.)Cassidy, M., Taylor, R.N., Palmer, M.R., Cooper, R.J., Stenlake, C., Trofimovs, J., Tracking the magmatic evolution of island arc volcanism: insights from a high-precision Pb isotope record of Montserrat, Lesser Antilles (2012) Geochemistry, Geophysics, Geosystems, 13, pp. 1-19Deering, C.D., Gravley, D.M., Vogel, T.A., Cole, J.W., Leonard, G.S., Origins of cold-wet-oxidizing to hot-dry-reducing rhyolite magma cycles and distribution in the Taupo Volcanic Zone, New Zealand (2010) Contributions to Mineralogy and Petrology, 160, pp. 609-629Déruelle, B., Moreau, C., Nkoumbou, C., Kambou, R., Lissom, J., Njonfang, E., Ghogomu, R.T., Nono, A., The Cameron line: a review (1991) Magmatism in Extensional Structural Settings, pp. 274-327. , Springer Verlag, Berlin, Germany, A.B. Kampunzu, R.T. Lubala (Eds.)Eby, G.N., Kochhar, N., Geochemistry and petrogenesis of the Malani igneous suite, northern peninsular India (1990) Journal of Geological Society of India, 36, pp. 109-130Grib, E.N., Leonov, V.L., Perepelov, A.B., The Karymskii Volcanic Center: volcanic rock geochemistry (2009) Journal of Volcanology and Seismology, 3, pp. 367-387Hollings, P., Kerrich, R., Trace element systematics of ultramafic and mafic volcanic rocks from the 3Ga North Caribou greenstone belt, northwestern Superior Province (1999) Precambrian Research, 93, pp. 257-279Kerrich, R., Manikyamba, C., Contemporaneous eruption of Nb-enriched basalts - K-adakites-Na-adakites from the 2.7Ga Penakacherla terrane: implications for subduction zone processes and crustal growth in the eastern Dharwar craton, India (2012) Canadian Journal of Earth Sciences, 49, pp. 615-636Krogstad, E.J., Hanson, G.N., Rajamani, V., Sources of continental magmatism adjacent to the late Archean Kolar Suture Zone, south India: distinct isotopic and elemental signatures of two late Archean magmatic series (1995) Contributions to Mineralogy and Petrology, 122, pp. 159-173Le Bas, M.J., Le Maitre, R.W., Streckeisen, A., Zanettin, B., A chemical classification of volcanic rocks based on the total alkali-silica diagram (1986) Journal of Petrology, 27, pp. 745-750Maheshwari, A., Sial, A.N., Coltorti, M., Chittora, V.K., Cruz, M.J.M., Geochemistry and petrogenesis of Siwana peralkaline granites, west of Barmer, Rajasthan, India (2001) Gondwana Research, 4, pp. 87-95Maheshwari, A., Coltori, M., Rajput, S.K., Verma, M., Geochemical characteristics, discrimination and petrogenesis of neoproterozoic peralkaline granites, Barmer District, SW Rajasthan, India (2009) International Geology Review, 51, pp. 1103-1120Middlemost, E.A.K., Iron oxidation ratios, norms and the classification of volcanic rocks (1989) Chemical Geology, 77, pp. 19-26Mohan, M.R., Piercey, S.J., Kamber, B.S., Sarma, D.S., Subduction related tectonic evolution of the Neoarchean eastern Dharwar Craton, southern India: new geochemical and isotopic constraints Precambrian Research., , in pressOliveira, M.A., Dall'Agnol, R., Althoff, F.J., Leite, A.A.S., Mesoarchean sanukitoid rocks of the Rio Maria Granite-Greenstone Terrane, Amazonian craton, Brazil (2009) Journal of South American Earth Sciences, 27, pp. 146-160Oliveira, E.P., McNaughton, N.J., Armstrong, R., Mesoarchaean to Palaeoproterozoic growth of the northern segment of the Itabuna-Salvador-Curaçá orogen, São Francisco craton, Brazil (2010) Geological Society of America, 338, pp. 263-286Pearce, J.A., Harris, N.B.W., Tindle, A.G., Trace element discrimination diagrams for the tectonic interpretation of granitic rocks (1984) Journal of Petrology, 25, pp. 956-983Rollinson, H.R., (1993) Using Geochemical Data: Evaluation, Presentation, Interpretation, , Longman Scientific Technical, Essex, (344 pp.)Schmitz, M.D., Smith, I.E.M., The petrology of the Rotoiti eruption sequence, Taupo Volcanic Zone: an example of fractionation and mixing in a rhyolitic system (2004) Journal of Petrology, 45, pp. 2045-2066Vaisanen, M., Eklund, O., Lahaye, Y., O'Brien, H., Frojdo, S., Hogdahl, K., Lammi, M., Intra-orogenic Sveconfennian magmatism in SW Finland constrained by LA-MC-ICP-MS zircon dating and geochemistryñ (2012) GFF, 134, pp. 99-114Verma, S.K., Pandarinath, K., Verma, S.P., Statistical evaluation of tectonomagmatic discrimination diagrams for granitic rocks and proposal of new discriminant-function-based multi-dimensional diagrams for acid rocks (2012) International Geology Review, 54, pp. 325-347Verma, S.P., Sixteen statistical tests for outlier detection and rejection in evaluation of International Geochemical Reference Materials: example of microgabbro PM-S (1997) Geostandards Newsletter: The Journal of Geostandards and Geoanalysis, 21, pp. 59-75Verma, S.P., Statistical evaluation of bivariate, ternary and discriminant function tectonomagmatic discrimination diagrams (2010) Turkish Journal of Earth Sciences, 19, pp. 185-238Verma, S.P., Geochemometrics (2012) Revista Mexicana de Ciencias Geológicas, 29, pp. 276-298Verma, S.P., Application of multi-dimensional discrimination diagrams and probability calculations to acid rocks from Portugal and Spain (2012) Comunicações Geológicas, 99, pp. 79-93Verma, S.P., Agrawal, S., New tectonic discrimination diagrams for basic and ultrabasic volcanic rocks through log-transformed ratios of high field strength elements and implications for petrogenetic processes (2011) Revista Mexicana de Ciencias Geológicas, 28, pp. 24-44Verma, S.P., Díaz-González, L., Application of the discordant outlier detection and separation system in the geosciences (2012) International Geology Review, 54, pp. 593-614Verma, S.P., Rivera-Gómez, M.A., New computer program TecD for tectonomagmatic discrimination from discriminant function diagrams for basic and ultrabasic magmas and its application to ancient rocks Journal of Iberian Geology., , in pressVerma, S.P., Rivera-Gómez, M.A., submitted for publication Computer programs for the classification and nomenclature of igneous rocks, , Episodes, (waiting decision)Verma, S.P., Verma, S.K., First fifteen probability-based multi-dimensional tectonic discrimination diagrams for intermediate magmas and their robustness against post-emplacement compositional changes and petrogenetic processes Turkish Journal of Earth Sciences, , in pressVerma, S.P., Torres-Alvarado, I.S., Sotelo-Rodríguez, Z.T., SINCLAS: standard igneous norm and volcanic rock classification system (2002) Computers & Geosciences, 28, pp. 711-715Verma, S.P., Torres-Alvarado, I.S., Velasco-Tapia, F., A revised CIPW norm (2003) Schweizerische Mineralogische und Petrographische Mitteilungen, 83, pp. 197-216Verma, S.P., Guevara, M., Agrawal, S., Discriminating four tectonic settings: five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log-ratio transformation of major-element data (2006) Journal of Earth System Science, 115, pp. 485-528Wolde, B., Asres, Z., Desta, Z., Gonzalez, J.J., Neoproterozoic zirconium-depleted boninite and tholeitic series rocks from Adola, southern Ethiopia (1996) Precambrian Research, 80, pp. 261-27
Tectonic Setting Of Basic Igneous And Metaigneous Rocks Of Borborema Province, Brazil Using Multi-dimensional Geochemical Discrimination Diagrams
No full textFifteen multi-dimensional diagrams for basic and ultrabasic rocks, based on log-ratio transformations, were used to infer tectonic setting for eight case studies of Borborema Province, NE Brazil. The applications of these diagrams indicated the following results: (1) a mid-ocean ridge setting for Forquilha eclogites (Central Ceará domain) during the Mesoproterozoic; (2) an oceanic plateau setting for Algodões amphibolites (Central Ceará domain) during the Paleoproterozoic; (3) an island arc setting for Brejo Seco amphibolites (Riacho do Pontal belt) during the Proterozoic; (4) an island arc to mid-ocean ridge setting for greenschists of the Monte Orebe Complex (Riacho do Pontal belt) during the Neoproterozoic; (5) within-plate (continental) setting for Vaza Barris domain mafic rocks (Sergipano belt) during the Neoproterozoic; (6) a less precise arc to continental rift for the Gentileza unit metadiorite/gabbro (Sergipano belt) during the Neoproterozoic; (7) an island arc setting for the Novo Gosto unit metabasalts (Sergipano belt) during Neoproterozoic; (8) continental rift setting for Rio Grande do Norte basic rocks during Miocene.58309317Agrawal, S., Guevara, M., Verma, S.P., Tectonic discrimination of basic and ultrabasic rocks through log-transformed ratios of immobile trace elements (2008) Int. Geol. Rev., 50, pp. 1057-1079Aitchison, J., (1986) The Statistical Analysis of Compositional Data, , Chapman and Hall, London, New YorkAlmeida, F.F.M., Hasui, Y., Brito Neves, B.B., Fuck, R.A., Brazilian structural provinces: an introduction (1981) Earth Sci. Rev., 17, pp. 1-29Amaral, W.D.S., Santos, T.J.S., Wernick, E., Matteini, M., Dantas, E.L., Moreto, C.P.N., U-Pb, Lu-Hf and Sm-Nd geochronology of rocks from the forquilha eclogite zone, ceará Central domain, borborema province, NE-Brazil (2010) VII-SSAGI South American Symposium on Isotope Geology, Brasília-DF (CD-ROM)Amaral, W.D.S., Santos, T.J.S., Wernick, E., Occurrence and geochemistry of metamafic rocks from the Forquilha Eclogite Zone, central Ceara' (NE Brazil): geodynamic implications (2011) Geol. J., 46, pp. 137-155Araujo, M.N.C., Oliveira, E.P., Carvalho, M.J., TectÔnica de endentação na Faixa Sergipana, NE do Brasil: compatibilização entre os elementos estruturais e cinemáticos (2003) IX Simpósio Nacional de Estudos TectÔnicos, Búzios, Boletim de Resumos, pp. 115-117Araujo, C.E.G., Cordani, U.G., Basei, M.A.S., Castro, N.A., Sato, K., Sproesser, W.M., U-Pb detrital zircon provenance of metasedimentary rocks from the Ceará Central and Médio Coreaú Domains, Borborema Province, NE-Brazil: tectonic implications for a long-lived Neoproterozoic active continental margin (2012) Precambrian Res., 206-207, pp. 36-51Armstrong-Altrin, J.S., Evaluation of two multidimensional discrimination diagrams from beach and deep-sea sediments from the Gulf of Mexico and their application to Precambrian clastic sedimentary rocks (2014) Int. Geol. Rev., , (in press)Arthaud, M.H., Caby, R., Fuck, R.A., Dantas, E.L., Parente, C.V., Geology of the northern Borborema Province, NE Brazil and its correlation with Nigeria, NWAfrica (2008) West Gondwana: Pre-cenozoic Correlations Across the South Atlantic Region, pp. 49-67. , Geological Society, London, Special Publications 294, R.J. Pankhurst, R.A.J. Trouw, B.B. Brito Neves, M.J. de Wit (Eds.)Bailie, R., Rajesh, H.M., Gutzmer, J., Bimodal volcanism at the western margin of the Kaapvaal Craton in the aftermath of collisional events during the Namaqua-Natal Orogeny: the Koras Group, South Africa (2012) Precambrian Res., 200, pp. 163-183Brito Neves, B., Santos, E.J., Van Schmus, W.R., Tectonic history of the borborema province, NW Brazil (2000) Tectonic Evolution of South America, pp. 151-182. , Rio de Janeiro, U.G. Cordani, E.J. Milani, A. Thomaz Filho, D.A. Campos (Eds.)Buccianti, A., Is compositional data analysis a way to see beyond the illusion? (2013) Comput. Geosci., 50, pp. 165-173Cabanis, B., Thiéblemont, D., La discrimination des tholéiites continentales et des basaltes arriérearc: proposition d un nouveau diagramme: le triangle Th-3xTb-2xTa (1988) Bull. la Société Géol. Fr., 8, pp. 927-935Castro, N.A., Araujo, C.E.G., Basei, M.A.S., Osako, L.S., Nutman, A.A., Liu, D., Ordovician A-type granitoid magmatism on the ceará Central domain, borborema province, NE-Brazil (2012) J.South Am. Earth Sci., 36, pp. 18-31Caxito, F.D.A., (2013) GeotectÔnica e evolução crustal das Faixas Rio Preto e Riacho do Pontal, Estados da Bahia, Pernambuco e Piauí, , Ph.D. thesis, Universidade Federal de Minas GeraisCaxito, F., Uhlein, A., Stevenson, R., Uhlein, G.J., Neoproterozoic oceanic crust remnants in northeast Brazil (2014) Geology, 42, pp. 387-390Davison, I., Santos, R.A., Tectonic evolution of the sergipano fold Belt, NE Brazil, during the Brasiliano orogeny (1989) Precambrian Res., 45, pp. 319-342D'el-Rey Silva, L.J.H., The evolution of basement gneiss domes of the Sergipano fold belt (NE Brazil) and its importance for the analysis of Proterozoic basins (1995) J.South Am. Earth Sci., 8, pp. 325-340Egozcue, J.J., Pawlowsky-Glahn, V., Mateu-Figueras, G., Barceló-Vidal, C., Isometric logratio transformations for compositional data analysis (2003) Math. Geol., 35, pp. 279-300Gava, A., Montes, A.L., Oliveira, E.P., Granitos alcalinos no sudeste do Piauí: caracterização geológica, petrográfica e geoquímica (1984) Anais XXXIII Congresso Brasileiro Geologia, 6, pp. 2767-2786. , SBG, Rio de JaneiroKnesel, K.M., Souza, Z.S., Vasconcelos, P.M., Cohen, B.E., Silveira, F.V., Young volcanism in the Borborema Province, NE Brazil, shows no evidence for a trace of the Fernando de Noronha plume on the continent (2011) Earth Planet. Sci. Lett., 302, pp. 38-50Marimon, M.P.C., (1990) Petrologia e litogeoquímica da sequência plutono-vulcanossedimentar do Brejo Seco, município de São João do Piauí, Estado do Piauí, p. 102. , Dissertação de Mestrado, Universidade Federal da Bahia, Curso de Pós-graduação em GeociênciasMartins, G., Oliveira, E.P., Lafon, J.-M., The Algodões amphibolite-tonalite gneiss sequence, Borborema Province, NE Brazil: geochemical and geochronological evidence for Palaeoproterozoic accretion of oceanic plateau/back-arc basalts and adakitic plutons (2009) Gondwana Res., 15, pp. 71-85Nascimento, R.S., (2005) Domínio Canindé, Faixa Sergipana, nordeste do Brasil: um estudo geoquímico e isotópico de uma sequência de rifte continental neoproterozóica, p. 140. , PhD thesis, Instituto de Geociências, Universidade Estadual de CampinasNeves, S.P., Bruguier, O., Silva, J.M.R., Bosch, D., Alcantara, V.C., Lima, C.M., The age distributions of detrital zircons in metasedimentary sequences in eastern Borborema Province (NE Brazil): evidence for intracontinental sedimentation and orogenesis? (2009) Precambrian Res., 175, pp. 187-205Neves, S.P., Monié, P., Bruguier, O., Rangel da Silva, J.M., Geochronological, thermochronological and thermobarometric constraints on deformation, magmatism and thermal regimes in eastern Borborema Province (NE Brazil) (2012) J.South Am. Earth Sci., 38, pp. 129-146Oliveira, E.P., Carvalho, M.J., Nascimento, R.S., Araújo, M.N.C., Dantas, E., Basilici, G., Bueno, J.F., McNaughton, N., Evidence from detrital zircon geochronology and whole-rock Sm-Nd isotopes for off-craton provenance of clastic metasedimentary units of the Sergipano belt, NE Brazil (2005) XSimpósio Nacional de Estudos TectÔnicos, Curitiba, Paraná, pp. 308-311Oliveira, E.P., Tarney, J., Petrogenesis of the Canindé de Sao Francisco Complex: a major Late Proterozoic gabbroic body in the Sergipe Foldbelt, northeastern Brazil (1990) J.South Am. Earth Sci., 3, pp. 125-140Oliveira, E.P., Toteu, S.F., Araújo, M.N.C., Carvalho, M.J., Nascimento, R.S., Bueno, J.F., McNaughton, N., Basilici, G., Geologic correlation between the Neoproterozoic Sergipano belt (NE Brazil) and the Yaoundé belt (Cameroon, Africa) (2006) J.Afr. Earth Sci., 44, pp. 470-478Oliveira, E.P., Windley, B.F., Araújo, M.N.C., The Neoproterozoic Sergipano orogenic belt, NE Brazil: a complete plate tectonic cycle in western Gondwana (2010) Precambrian Res., 181, pp. 64-84Oliveira, E.P., McNaughton, N.J., Araújo, M.N.C., Carvalho, M.J., Bueno, J.F., Nascimento, R.S., Windley, B.F., The neoproterozoic sergipano orogenic Belt at the N-NE boundary of the são francisco craton (2014) Regional Geology Review Series, , Springer Verlag, Chapter 13 (in press), M. Heilbron, F. Alkmim, U. Cordani (Eds.) The São Francisco Craton and its Margins, Eastern BrazilPandarinath, K., Testing of the recently developed tectonomagmatic discrimination diagrams from hydrothermally altered igneous rocks of 7 geothermal fields (2014) Turkish J. Earth Sci., 23, pp. 412-426Pandarinath, K., Verma, S.K., Application of four sets of tectonomagmatic discriminant function based diagrams to basic rocks from northwest Mexico (2013) J.Iber. Geol., 39, pp. 181-195Parent, S.-E., Parent, L.E., Egozcue, J.J., Rozane, D.-E., Hernandes, A., Lapointe, L., Hébert-Gentile, V., Natale, W., The plant ionome revisited by the nutrient balance concept (2013) Front. Plant Sci., 4Pawlowsky-Glahn, V., Egozcue, J.J., (2006) Compositional Data Analysis in the Geosciences: from Theory to Practice, pp. 1-10Pearce, J.A., Geochemical fingerprinting of oceanic basalts with applications to ophiolite classification and the search for Archean oceanic crust (2008) Lithos, 100, pp. 14-48Pearce, J.A., Cann, J.R., Tectonic setting of basic volcanic rocks determined using trace element analyses (1973) Earth Planet. Sci. Lett., 19, pp. 290-300Pearce, J.A., Harris, N.B.W., Tindle, A.G., Trace element discrimination diagrams for the tectonic interpretation of granitic rocks (1984) J. Petrol., 25, pp. 956-983Polat, A., Geochemical variations in Archean volcanic rocks, southwestern Greenland: traces of diverse tectonic settings in the early Earth (2013) Geology, 41, pp. 379-380Polat, A., Frei, R., Fryer, B., Appel, P.W.U., The origin of geochemical trends and Eoarchean (ca. 3700 Ma) zircons in Mesoarchean (ca. 3075 Ma) ocelli-hosting pillow basalts, Ivisaartog greenstone belt, SW Greenland: evidence for crustal contamination versus crustal recycling (2009) Chem. Geol., 268, pp. 248-271Polat, A., Fryer, B.J., Appel, P.W.U., Kalvig, P., Kerrich, R., Dilek, Y., Yang, Z., Geochemistry of anorthositic differentiated sills in the Archean (~2970 Ma) Fiskenæsset Complex, SW Greenland: Implications for parental magma compositions, geodynamic setting, and secular heat flow in arcs (2011) Lithos, 123, pp. 50-72Santos, T.J.S., Fetter, A.H., Hackspacher, P.C., Van Schmus, W.R., Nogueira Neto, J.A., Neoproterozoic tectonic and magmatic episodes in the NW sector of the Borborema Province, NE Brazil, during assembly of western Gondwana (2008) J.South Am. Earth Sci., 25, pp. 271-284Sheth, H.C., Do major oxide tectonic discrimination diagrams work? Evaluating new log-ratio and discriminant-analysis-based diagrams with Indian Ocean mafic volcanics and Asian ophiolites (2008) Terra Nova, 20, pp. 229-236Trompette, R., (1994) Geology of Western Gondwana, Pan-African/Brasiliano Aggregation of South America and Africa, p. 350. , A. A. Balkema, Rotterdam, BrookfieldVan Schmus, W.R., Brito Neves, B.B., Hackspacher, P.C., U/Pb and Sm/Nd geochronologic studies of the eastern Borborema Province, NE Brazil (1995) J.South Am. Earth Sci., 8, pp. 267-288Van Schmus, W.R., Oliveira, E.P., Silva Filho, A.F., Toteu, S.F., Penaye, J., Guimarães, I.P., (2008) Proterozoic Links between the Borborema Province, NE Brazil, and the Central African Fold Belt, pp. 69-99. , Geological Society, London, Special Publications 294Verma, S.K., Pandarinath, K., Verma, S.P., Statistical evaluation of tectonomagmatic discrimination diagrams for granitic rocks and proposal of new discriminant-function-based multi-dimensional diagrams for acid rocks (2012) Int. Geol. Rev., 54, pp. 325-347Verma, S.K., Oliveira, E.P., Application of multi-dimensional discrimination diagrams and probability calculations to Paleoproterozoic acid rocks from Brazilian cratons and provinces to infer tectonic settings (2013) J.South Am. Earth Sci., 45, pp. 117-146Verma, S.K., Verma, S.P., Identification of Archaean plate tectonic processes from multidimensional discrimination diagrams and probability calculations (2013) Int. Geol. Rev., 55, pp. 225-248Verma, S.K., Verma, S.P., Oliveira, E.P., Plate tectonic settings for Precambrian basic rocks from Brazil by using new multi-dimensional tectonomagmatic discrimination diagrams (2014) Int. Geol. Rev.Verma, S.P., Continental rift setting for the central part of the Mexican Volcanic Belt: a statistical approach (2009) Open Geol. J., 3, pp. 8-29Verma, S.P., Statistical evaluation of bivariate, ternary and discriminant function tectonomagmatic discrimination diagrams (2010) Turkish J. Earth Sci., 19, pp. 185-238Verma, S.P., Geochemometrics (2012) Rev. Mex. Ciencias Geol., 29, pp. 276-298Verma, S.P., Application of multi-dimensional discrimination diagrams and probability calculations to acid rocks from Portugal and Spain (2012) Comun. Geol., 99, pp. 79-93Verma, S.P., Application of fifty multi-dimensional discrimination diagrams and significance tests: deciphering compositional similarities and differences between Hawaiian and Icelandic volcanism (2013) Int. Geol. Rev., 55, pp. 1553-1572Verma, S.P., Agrawal, S., New tectonic discrimination diagrams for basic and ultrabasic volcanic rocks through log-transformed ratios of high field strength elements and implications for petrogenetic processes (2011) Rev. Mex. Ciencias Geol., 28, pp. 24-44Verma, S.P., Rivera-Gómez, M.A., New computer program TecD for tectonomagmatic discrimination from discriminant function diagrams for basic and ultrabasic magmas and its application to ancient rocks (2013) J.Iber. Geol., 39, pp. 167-179Verma, S.P., Rivera-Gómez, M.A., Computer programs for the classification and nomenclature of igneous rocks (2013) Episodes, 36, pp. 115-124Verma, S.P., Verma, S.K., First 15 probability-based multidimensional tectonic discrimination diagrams for intermediate magmas and their robustness against postemplacement compositional changes and petrogenetic processes (2013) Turkish J. Earth Sci., 22, pp. 931-995Verma, S.P., Armstrong-Altrin, J.S., New multi-dimensional diagrams for tectonic discrimination of siliciclastic sediments and their application to Precambrian basins (2014) Chem. Geol., 355, pp. 117-133Verma, S.P., Guevara, M., Agrawal, S., Discriminating four tectonic settings: five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log-ratio transformation of major-element data (2006) J.Earth Syst. Sci., 115, pp. 485-528Verma, S.P., Verma, S.K., Pandarinath, K., Rivera-Gómez, M.A., Evaluation of recent tectonomagmatic discrimination diagrams and their application to the origin of basic magmas in Southern Mexico and Central America (2011) Pure Appl. Geophys., 168, pp. 1501-1525Verma, S.P., Pandarinath, K., Verma, S.K., Agrawal, S., Fifteen new discriminant-function-based multi-dimensional robust diagrams for acid rocks and their application to Precambrian rocks (2013) Lithos, 168-169, pp. 113-123Verma, S.P., Verma, S.K., Oliveira, E.P., Application of 55 multi-dimensional tectonomagmatic discrimination diagrams to Precambrian belts (2014) Int. Geol. Rev., , (in press
Sweeping has no effect on renormalized turbulent viscosity
No full textWe perform renormalization group analysis (RG) of the Navier-Stokes equation in the presence of constant mean velocity field , and show that the renormalized viscosity is unaffected by , thus negating the ``sweeping effect", proposed by Kraichnan [Phys. Fluids {\bf 7}, 1723 (1964)] using random Galilean invariance. Using direct numerical simulation, we show that the correlation functions for and differ from each other, but the renormalized viscosity for the two cases are the same. Our numerical results are consistent with the RG calculations
A Unified Shell model for Buoyancy-Driven Turbulence
No full textWe construct a unified shell model for stably stratified and convective turbulence. Shell model simulation of stably stratified flow in turbulent regime exhibit Bolgiano-Obukhbov (BO) scaling in which the kinetic energy spectrum varies as . However, simulation of convective turbulence shows Kolmogorov's spectrum. These results are consistent with the direct numerical simulations of Kumar {\em et al.} [Phys. Rev. E {\bf 90}, 023016 (2014)]. We also observe a dual scaling ( and ) for a limited range of parameters in stably stratified flow
Energy transfers in small-scale and large-scale dynamos
No full textWe study energy transfers during magnetic energy growth in small-scale and large-scale dynamos. We perform direct numerical simulations for magnetic Prandtl number Pm =20 and 0.2 in a periodic box on 1024^3 grid. Energy fluxes and shell-to-shell energy transfers indicate that in small-scale dynamo for Pm =20, the magnetic energy growth takes place due to a non-local energy transfer from large-scale velocity field to small-scale magnetic field. On the other hand, in large-scale dynamo for Pm =0.2, local energy transfers from large-scale velocity field to large-scale magnetic field takes place
Role of the strain-rate tensor in turbulent scalar-transport modeling
No full textWe examine the geometric orientation of the subfilter-scale scalar-flux vector in homogeneous isotropic turbulence. Vector orientation is determined using the eigenframe of the resolved strain-rate tensor. The Schmidt number is kept sufficiently large so as to leave the velocity field, and hence, the strain-rate tensor, unaltered by filtering in the viscous-convective subrange. Strong preferential alignment is observed for the case of Gaussian and box filters, whereas the sharp-spectral filter leads to close to a random orientation. The orientation angle obtained with the Gaussian and box filters is largely independent of the filter-width and the Schmidt number. It is shown that the alignment direction observed numerically using these two filters is predicted very well by the tensor-diffusivity model. Further a-priori tests indicate poor alignment of the Smagorinsky and stretched vortex model predictions with the exact subfilter flux
Systems of Differential Operators and Generalized Verma Modules
No full textIn this paper we close the cases that were left open in our earlier works on the study of conformally invariant systems of second-order differential operators for degenerate principal series. More precisely, for these cases, we find the special values of the systems of differential operators, and determine the standardness of the homomorphisms between the generalized Verma modules, that come from the conformally invariant systems.The author was supported by the Global COE program at the Graduate School of Mathematical
Sciences, the University of Tokyo, Japan. He would like to be thankful for the referees for their
careful reading and invaluable comments
Special Volume on Geochemistry in Mexico
No full textLa propuesta de editar un número especial sobre Geoquímica surgió durante las actividades del Instituto Nacional de Geoquímica, A. C. (INAGEQ), creado en junio de 1990, por Surendra P. Verma J., David J. Terrell, Juan Manuel Barbarín C., Georgina Izquierdo M., Ma.Aurora Armienta H. y Cecilia 0. Rodriguez de B., antes de la realización del "ler. Congreso Nacional de Geoquímica", Linares, N. L., 3-5 de septiembre de 1991. Este primer congreso reunió a cerca de 100 profesionales, investigadores y estudiantes, en donde se presentaron 45 trabajos en 9 sesiones técnicas. El directorio de los miembros y los estatutos del INAGEQ, así como algunos trabajos cortos, se incluyeron en el vol. 6, LIV + 209 p., de las Actas de la Facultad de Ciencias de la Tierra de la Universidad Autónoma de Nuevo León, Linares (S.P. VERMA, J. A. RAMIREZ F., C. 0. RODRIGUEZ DE B.,, J. M. BARBARIN C., G. IZQUIERDO M., M. A.ARMIENTA H. yD. J. TERRELL, editores)
Número Especial sobre Geoquímica en México. PRESENTACION
No full textLa propuesta de editar un número especial sobre Geoquímica surgió durante las actividades del Instituto Nacional de Geoquímica, A. C. (INAGEQ), creado en junio de 1990, por Surendra P. Verma J., David J. Terrell, Juan Manuel Barbarín C., Georgina Izquierdo M., Ma.Aurora Armienta H. y Cecilia 0. Rodriguez de B., antes de la realización del "ler. Congreso Nacional de Geoquímica", Linares, N. L., 3-5 de septiembre de 1991. Este primer congreso reunió a cerca de 100 profesionales, investigadores y estudiantes, en donde se presentaron 45 trabajos en 9 sesiones técnicas. El directorio de los miembros y los estatutos del INAGEQ, así como algunos trabajos cortos, se incluyeron en el vol. 6, LIV + 209 p., de las Actas de la Facultad de Ciencias de la Tierra de la Universidad Autónoma de Nuevo León, Linares (S.P. VERMA, J. A. RAMIREZ F., C. 0. RODRIGUEZ DE B.,, J. M. BARBARIN C., G. IZQUIERDO M., M. A.ARMIENTA H. yD. J. TERRELL, editores)
- …
