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Sample records for bambui group neoproterozoic

  1. Influence of geological and hydrogeological factors on the high natural fluoride concentrations in groundwaters in Bambui Group (Neoproterozoic), northern of Minas Gerais state, Brazil; Influencia de los factores geologicos e hidrogeologicos en las altas concentraciones naturales de fluoruro en las aguas subterraneas del Grupo Bambui (Neoproterozoico), norte del estado de Minas Gerais, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Iglesias Martinez, M.; Velasquez, L. N.M.; Fantinel, L. M.; Uhlein, A.; Melo da Silva, S.; Rodrigues, P. C. H.

    2010-07-01

    In the northern semi-arid and semi-humid region of Minas Gerais State, in the southeast Brazil, substantial part of the water supplying is produced by means of deep wells. In several localities the fluoride concentrations are higher than 1.5 mg/L, maximum acceptable limit for drinking water, endangering the public supply and the public health. Endemies of dental fluorosis have been detected since the decade of 1990. The cause of this problem has been associated to the consumption of local drinking water. Current studies indicate the occurrences of fluorite in the limestones of the Bambui Group as the main mineral-source for the fluoride content in the groundwater, however without identifying the specific contribution of each hydrostratigraphic unit. This work shows the results of stratigraphic studies and hydro-chemical analysis of 144 deep wells and the influence of the carbonatic facies in the fluoride concentrations of the water. Fluoride concentrations are related to fluorite occurrences/mineralizations (lithostratigraphic control) and to circulation depth of groundwater (geochemical control), newly distinguishing three hydrostratigraphic units. The correlation analysis of hydrogeochemic parameters (F-, Mg{sub 2}+, SO{sub 4}{sup 2}- and electric conductivity) corroborates these grouping into three units. The probability of the contamination by fluoride, as a function of the hidroestratigraphic units, in decreasing order, seems to be: top level of the Sete Lagoas Formation; Lagoa do Jacare Formation; and botton and middle levels of the Sete Lagoas Formation. (Author)

  2. PROTEROZOIC STROMATOLITES FROM CENTRAL BRAZIL: PALAEOECOLOGICAL AND TECTONIC SETTING IN PARANOA AND BAMBUI GROUPS%巴西中部元古代Paranoá和Bambui群叠层石的古生态和构造背景

    Institute of Scientific and Technical Information of China (English)

    EMGUIMARA^~ES; LSOARES; TFAIRCHILD; MADARDENNE

    2003-01-01

    Stromatolite morphologies and their terrigenous sediment association indicate depositional basin tectonic gin basin (Dardenne & Faria, 1986), while the other two groups represent a foreland basin (Guimaraes, 1993,1997, 1998, Dardenne et al. , 1998). The sediments of the Vazante Group were deposited near the mountain which forms the Brasilia Fold Belt; however, most of the area of Bambui Group originated in a cratonic region. Generalstromatolite buildings are associated with variations in environmental conditions. However, very often changes in the columnar growth direction and irregular terrigenous-rich intercalations into stromatolites characterize tectonically active settings such as in Vazante Group and in the western portion of the Paranoa and Bambui groups.%叠层石的形态和它们与陆源沉积的关系反映了沉积盆地的构造背景.在巴西中部地区,叠层石出现在中元古和新元古代的Paranoa群、Vazante群和Bambui群.根据沉积学和矿物学的研究分析,Paranoá群形成于被动边缘盆地,而另外两个群形成于前陆盆地.Vazante群沉积在形成巴西褶皱带的山脉附近,然而Bambui群的大部分都形成于克拉通地区.通常远离山脉褶皱带的Paranoá群和B2mbuí群内的叠层石建造的形态和规模的改变与环境的变化有关.在柱状生长方向的频繁变化和不规则的丰富陆源物质的夹层进入叠层石,表征活跃的构造背景,例如在Vazante,Paranoá群和Bambuí群的西部.

  3. The Neoproterozoic Tillite Group from Ella Ø, East Greenland

    DEFF Research Database (Denmark)

    Buchardt, Bjørn; Kristiansen, Kasper K.; Houmark-Nielsen, Michael

    is ~1200 m. The Ulvesø Fm rests conformably on shales and stromatolithic calcareous rocks of suggested warm water origin, and the Storeelv Fm is conformably overlain by clastic rocks showing pseudomorphoses after halite in the uppermost unit. The two diamictitic units are separated by the ~250 m thick Area...... is disconformably overlain by sediments of Cambrian age. Fieldwork by us on Ella Ø has questioned the glacial origin of at least the lower diamictitic unit (Ulvesø Fm), while the upper unit (Storeelv Fm) shows unequivocal evidence of glacial activities at the base. On Ella Ø, the thickness of the Tillite Group...... compositions of the stromatolithic carbonates of Bed Group 18 are significantly enriched compared to modern values with a mean of +7‰ V-PDB. The shift from calcareous rocks of Bed Group 18 to shaly and cherty sediments of Bed Group 19 is accompanied by a negative shift in d13C of more that 15‰, and average...

  4. The Mesoproterozoic to early Neoproterozoic passive margin Lajeado Group and Apiaí Gabbro, Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    G.A.C. Campanha

    2016-07-01

    Full Text Available The Lajeado Group in the Ribeira Belt, southeastern Brazil, corresponds to an open-sea carbonate platform, comprised of seven overlapping siliciclastic and carbonatic formations, intruded in its upper portion by the Apiaí Gabbro. These rocks have a Neoproterozoic tectonometamorphic overprint related to arc magmatism and the Brasiliano collisional orogeny. Geochronological constraints are given by new U-Pb SHRIMP and LA-ICP-MS data for Lajeado Group detrital zircons and for magmatic zircons from the Apiaí Gabbro. The youngest detrital zircons in the Lajeado Group are 1400–1200 Ma, and constrain its maximum age of deposition to be <1200 Ma, whereas the 877 ± 8 Ma age for magmatic zircons in the Apiaí Gabbro give the minimum age. Detritus source areas are mainly Paleoproterozoic (2200–1800 Ma with some Archean and Mesoproterozoic contribution (1500–1200 Ma, with distal or tectonic stable cratonic character. The Lajeado Group should be a Stenian–Tonian carbonate platform passive margin of a continent at this time, namely the Columbia/Nuna or the Rodinia. The Apiaí Gabbro displays similar age to other intrusive basic rocks in the Lajeado and Itaiacoca groups and represents tholeiitic MORB-like magmatism that we relate to the initial break-up of a Mesoproterozoic continent and the formation of the Brasiliano oceans.

  5. Gênese de latossolos e cambissolos desenvolvidos de rochas pelíticas do grupo Bambuí - Minas Gerais Genesis of latosols and cambisols developed from pelitic rocks of the Bambui group, Minas Gerais state - Brazil

    Directory of Open Access Journals (Sweden)

    Thiago Torres Costa Pereira

    2010-08-01

    , dense and silty and of clayey and very clayey Latosols is typical of pelitic rocks of the pre-Cambrian Bambui Group landscape, but few studies are focused on the genesis and agricultural potential of these soils. Two areas were selected in Curvelo, state of Minas Gerais, for a detailed study of physical, chemical and mineralogical properties of these soils, to deepen the understanding of the pedogenesis of this area. Soils classified as Haplic Cambisols (Inceptisols, Red-Yellow latosol (Xanthic Haplustox and Red latosol (Rhodic Haplustox were selected and sampled, and analyzed for the chemical, mineralogical and physical properties. The XRD data coupled with the calculated weathering index indicated a lower degree of weathering in the shallow Cambisols, with higher proportion of illite and kaolinite in the clay fraction, in comparison to the Latosols, where kaolinite, gibbsite and hydroxy-interlayered vermiculite (HIV coexist. In this case, the occurrence of gibbsite is not a good indicator of severe weathering. In the shallow Cambisols, higher silt content combined with a face-to-face arrangement of clay particles (kaolinite/illite may have resulted in poor structural organization, denseness, low water infiltration and soil sealing. In the clay fraction of Latosols, we observed the coexistence of kaolinite/illite and Fe/Al oxides, similarly to the Cambisols, but with much less illite and higher gibbsite contents, as inferred from the results of Ki of around 1.4. Although there are no remarkable physical and chemical differences among Latosols, the Rhodic Latosols displayed considerable magnetization in the sand fraction, where XRD confirmed the presence of magnetite, an uncommon fact in the supposedly magnetite-free pelitic lithologies of the Bambuí Group, but reported in previous studies as well.

  6. Organotemplate structures in sedimentary manganese carbonates of the Neoproterozoic Penganga Group, Adilabad, India

    Indian Academy of Sciences (India)

    Joydip Mukhopadhyay; Jens Gutzmer; Nicolas J Beukes

    2005-06-01

    Manganese carbonates interstratified with bedded chert in the Chanda Limestone of the Neoproterozoic Penganga Group at Adilabad, south India, have been studied for possible evidence that microbiota played a role in the mediation of early diagenetic Mn-carbonate formation in Precam- brian marine sedimentary successions. The manganese carbonate and chert beds occur within a below wave base, deep-water distally steepened ramp succession. High resolution SEM petrogra- phy of the manganese carbonates revealed two basic morphologies — spherical to oval-cylindrical shaped microconcretions, and tubular to irregular, elongated, film-like microstructures. Infolded filmy to hollow tubular strand-like internal morphologies of the spherical to oval-cylindrical shaped microconcretions suggest their microbial affinity. The tubular and film morphologies with mesh- like interconnections closely resemble architectures of microbial extracellular polymeric substance (EPS). Mineralization took place on these organotemplates by the process of permineralization as well as replacement in an early diagenetic pore-water environment with reduction of higher manganese oxy-hydroxides by organic matter and consequent increase in dissolved carbonate.

  7. Southern Brasilia Belt (SE Brazil): tectonic discontinuities, K-Ar data and evolution during the Neoproterozoic Brasiliano orogeny

    Energy Technology Data Exchange (ETDEWEB)

    Valeriano, Claudio Morrison de [Universidade do Estado, Rio de Janeiro, RJ (Brazil)]. E-mail: cmval@uerj.br; Teixeira, Wilson [Sao Paulo Univ., SP (Brazil); Simoes, Luiz Sergio Amarante [UNESP, Sao Paulo, SP (Brazil); Heilbron, Monica [Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brasilia, DF (Brazil)

    2000-03-01

    This paper focuses the tectonic evolution of the southern brasilia belt, with emphasis on the Furnas segment, along the 21 deg C S parallel. The uppermost structural unit (Passos Nappe - PN) comprises a highly deformed metasedimentary succession interpreted as a fragment of the Neoproterozoic passive margin of western Sao francisco craton. An inverted metamorphic gradient ranging from greensvhits to lower granulite facies of medium to high-pressure regime characterizes the PN as relict of a subduction zone. The External Domain display a complex imbrication of basement rocks (Archean Piumhi greenstones, a turbiditic gaywacke succession and a calc-alkaline granitoid suite) with undated siliciclast low-grade metasedimentary rocks. The Sao Francisco Craton (SFC) comprises pre-1.8 Ga basement rocks covered by anchimetamorphic Neoproterozoic carbonatic shallow marine platform deposits of the Bambui group. The Brasiliano thrust stacking generated a coarse clastic influx of molassic character on the foreland zone of Sao Francisco Craton, coeval with the exhumation of the External Domain thrust sheets. New K-Ar determinations on mineral separates are presented an interpreted among previous data. The SFC basement rocks display Paleo-to Meesoproterozoic cooling ages. The allochthonous units, in contrast, display K-Ar ages within the 560-675 Ma range. Brasiliano thrust stacking is therefore interpreted to have taken place onto a cold Sao Francisco craton foreland, in a thin-skinned style, as basement rocks were not heated enough to have their-K-ar systems reset during the allochthony. (author)

  8. Bambuina bambui: a new genus and species of cave cricket from Brazil (Orthoptera: Grylloidea: Phalangopsidae: Luzarinae).

    Science.gov (United States)

    De Mello, Francisco De A G; Horta, Lília S; Bolfarini, Marcio P

    2013-01-03

    Bambuina bambui, um novo gênero e espécie de grilo falangopsídeo é descrito a partir de espécimes obtidos na Gruta do Centenário, uma caverna de quartzo localizada na Serra do Inficionado, um subconjunto de montanhas pertencentes ao complexo da Serra do Caraça no estado de Minas Gerais, Brasil.

  9. High frequency peritidal cycles of the upper Araras Group: Implications for disappearance of the neoproterozoic carbonate platform in southern Amazon Craton

    Science.gov (United States)

    Rudnitzki, Isaac Daniel; Romero, Guilherme Raffaeli; Hidalgo, Renata; Nogueira, Afonso Cesar Rodrigues

    2016-01-01

    The Araras Group is an extensive carbonate platform developed at the southeastern margin of the Amazon Craton during the Neoproterozoic. The Nobres Formation corresponds to the upper unit of the Neoproterozoic Araras Group. It is exposed in road cuts and quarries in the Northern Paraguay Belt, and is characterized by meter-scale shallowing upward cycles. Forty-four fourth-to fifth-order parasequence cycles are enclosed into three third order sequences/megacycles, unconformably overlain by siliciclastic deposits of the Alto Paraguay Group. The cycles are generally of peritidal type, limited by exposure surfaces composed of asymmetrical tidal flat/sabkha lithofacies in the basal Nobres Formation. They consist of fine dolostone, intraclastic dolostones with megaripples, stromatolites biostrome, sandy dolostone with enterolithic structures and silicified evaporite molds. Upsection, the cycles progressively become symmetrical, comprising arid tidal flat deposits with abundant stromatolite biostrome, fine-grained sandstone and rare evaporitic molds. The stacking patterns for hundreds of meters indicate continuous and recurrent generation of accommodation space, probably triggered by subsidence concomitant with relative sea-level changes. Palynomorphs found in the upper part of Nobres Formation comprehend spheroidal forms, such as Leiospharidia, rare filamentous and acanthomorphous acritarchs, mostly Tanarium correlated to the Ediacaran Complex Acantomorph Palynoflora of ˜580-570 Ma. Previous data of carbon isotopes and paleogeographic reconstructions, and also the presence of evaporites and storm-influenced deposits in the Araras Group, suggest a wet to tropical setting for Amazonia during the Mid-Ediacaran, which is incompatible with previous claims for Gaskiers-related glacial sedimentation in the region. During the final stages of evolution of the Araras carbonate platform, a progressive input of terrigenous has occurred in the peritidal setting likely due tectonic

  10. Chemostratigraphy of Neoproterozoic Banded Iron Formation (BIF)

    DEFF Research Database (Denmark)

    Gaucher, Claudio; Sial, Alcides N.; Frei, Robert

    2015-01-01

    Brazil), Chuos, and Numees Formations (Namibia) and Holowilena Ironstone (Australia). However, many occurrences are not related to glacial processes and can be assigned to the Algoma and Lake Superior types. Neoproterozoic Algoma-type BIF includes the Wadi Karim and Um Anab (Egypt), the correlative......Neoproterozoic banded iron formations (BIFs) are not restricted to the middle Cryogenian, c. 715 Ma glaciation, occurring in Tonian, Cryogenian, and Ediacaran successions. Many Neoproterozoic BIFs were deposited in glacially influenced settings, such as the Rapitan Group (Canada), Jacadigo Group (W...... Sawawin BIF (Saudi Arabia), and the Jucurutu Formation of the Seridó Belt (NE Brazil). Lake Superior type BIFs are represented by the Tonian Shilu Group (South China) and the late Ediacaran Arroyo del Soldado Group (Yerbal and Cerro Espuelitas formations, Uruguay). Useful chemostratigraphic tools...

  11. The Middle Neoproterozoic Sidi Flah Group (Anti-Atlas, Morocco): synrift deposition in a Pan-African continent/ocean transition zone

    Science.gov (United States)

    Fekkak, A.; Pouclet, A.; Benharref, M.

    2003-08-01

    The Middle Neoproterozoic (Cryogenian) Sidi Flah Group rocks are located in the Saghro inlier of the Eastern Anti-Atlas and consists of siliciclastic detrital sediment, interbedded basaltic lavas and small ultramafic bodies. Sediment deposition occurred in three turbiditic formations of a deep-sea fan environment and was controlled by synsedimentary collapses. The composition of sandstones and typological study of zircons indicate that detrital material came from the gneisses and granites of a proximal craton. The lavas are synsedimentary subaqueous flows. They show chemical signatures of initial rift tholeiites and of plume-related alkaline intraplate basalts. The ultramafic rocks are serpentinized peridotites that were emplaced along N160° synsedimentary faults as numerous bodies 20-50 m in size. Their petrographical (Cr-spinel signature) and chemical features correspond to intracontinental ultramafic cumulates. The emplacement of the ultramafic rocks was associated with hydrothermal activity that generated calcareous and siliceous rocks such as ophicalcites and jaspers. All the features of the sediments, the lavas and the ultramafic bodies strongly suggest a continent-ocean transition geotectonic context, in an advanced stage of continental rifting that we attribute to the pre-Pan-African ocean passive margin extension.

  12. Zircon U-Pb Geochronology, Hf Isotopic Composition and Geological Implications of the Neoproterozoic Huashan Group in the Jingshan Area, Northern Yangtze Block, China

    Science.gov (United States)

    Yang, Z.; Yang, K.

    2015-12-01

    In the northern Yangtze Block, a clear angular unconformity between the Mesoproterozoic sequences (e.g. Dagushi Group) and the overlying Neoproterozoic strata (e.g. Huashan Group) marks the the Jinning orogeny. A combined study of Lu-Hf isotopes and U-Pb ages for detrital zircons from Huashan Group can provide information on the crustal evolution of sedimentary provenances and the timing of the Jinning orogeny. Detrital zircons from Huashan Group have two major U-Pb age populations of about 2.0Ga, 2.65Ga, and three subordinate age groups of about 0.82Ga, 2.5Ga, 2.9Ga with minor >3.0Ga ages. The youngest five analyses yield a weighted average age of 816±9Ma, which is consistent with that of interlayered basalt (824±9Ma, Deng et al., 2013) and roughly defines the minimum depositional age of Huashan Group. Detrital zircons of Huashan Group mostly have two stage Hf isotope model ages (TDM2) between 3.0 to 3.3Ga, indicating that the northern Yangtze Block experienced significant continental crustal growth during the Paleo- to Meso-archean. Similar U-Pb ages of detrital zircons have been obtained from Precambrian sedimentary rocks in the northern Yangtze Block from previous studies (Liu et al., 2008; Guo et al., 2014 and references therein). Recently, ca. 2.65Ga A-type granites had been reported from the Kongling and Huji area, which likely record the thermally stable lithosphere (Chen et al., 2013; Zhou et al., 2015). In combination with this study, it documents the widespread 2.6-2.7Ga magmatic rocks in the northern Yangtze Block. Zhao et al. (2013) demonstrated both the ca. 850Ma tonalite and trondhjemite of the Huangling igneous complex were formed in a continental arc setting. This suggests the Miaowan-Huashan oceanic basin proposed by Bader et al. (2013) has not been closed at ca. 850Ma. This evidence, together with the depositional age of the Huashan Group, indicates the Jinning orogeny took place at 850-820 Ma. [1] Bader et al., 2013 Tectonics [2] Deng et al

  13. Modal analysis and geochemistry of two sandstones of the Bhander Group (Late Neoproterozoic) in parts of the Central Indian Vindhyan basin and their bearing on the provenance and tectonics

    Indian Academy of Sciences (India)

    Apurba Banerjee; D M Banerjee

    2010-12-01

    The Neoproterozoic Bhander Group in the Son Valley, central India conformably overlying the Rewa Group, is the uppermost subdivision of the Vindhyan Supergroup dominantly composed of arenites, carbonates and shales. In Maihar –Nagod area, a thick pile of unmetamorphosed clastic sedimentary rocks of Bhander Group is exposed, which provides a unique opportunity to study Neoproterozoic basin development through provenance and tectonic interpretations. The provenance discrimination and tectonic setting interpretations are based on modal analysis and whole rock geochemistry. The average framework composition of the detrital sediments composed of quartz and sedimentary lithic fragments are classified as quartz arenite to sublitharenite. The sandstone geochemically re flects high SiO2 moderate Al2O3 and low CaO and Na2O type arenite. The high concentration of HFSE such as Zr, Hf , and Th/Sc, Th/U ratios in these sandstones indicate a mixed provenance. The chondrite normalized REE pattern shows moderate to strong negative Eu anomaly which suggests that major part of the sediments were derived from the granitic source area. The sandstone tectonic discrimination diagrams and various geochemical plots suggest that the provenance of the lower and upper Bhander sandstone formations was continental interior to recycled orogen.

  14. Learning to tell Neoproterozoic time.

    Science.gov (United States)

    Knoll, A H

    2000-03-01

    In 1989, the International Commission on Stratigraphy established a Working Group on the Terminal Proterozoic Period. Nine years of intensive, multidisciplinary research by scientists from some two dozen countries have markedly improved the framework for the correlation and calibration of latest Proterozoic events. Three principal phenomena--the Marinoan ice age, Ediacaran animal diversification, and the beginning of the Cambrian Period--specify the limits and character of this interval, but chemostratigraphy and biostratigraphy based on single-celled microfossils (acritarchs), integrated with high-resolution radiometric dates, provide the temporal framework necessary to order and evaluate terminal Proterozoic tectonic, biogeochemical, climatic, and biological events. These data also provide a rational basis for choosing the Global Stratotype Section and Point (GSSP) that will define the beginning of this period. A comparable level of stratigraphic resolution may be achievable for the preceding Cryogenian Period, providing an opportunity to define this interval, as well, in chronostratigraphic terms--perhaps bounded at beginning and end by the onset of Sturtian glaciation and the decay of Marinoan ice sheets, respectively. Limited paleontological, isotopic, and radiometric data additionally suggest a real but more distant prospect of lower Neoproterozoic correlation and stratigraphic subdivision.

  15. Neoproterozoic granitoids on Wrangel Island

    Science.gov (United States)

    Luchitskaya, M. V.; Sergeev, S. A.; Sokolov, S. D.; Tuchkova, M. I.

    2016-07-01

    Based on geochronological U-Pb studies, the age of Wrangel Island granitoids was estimated as Neoproterozoic (Cryogenian). Some granitoids contain zircons with inherited cores with an estimated age of 1010, 1170, 1200, and >2600 Ma, assuming the presence of ancient (Neoarchean-Mesoproterozoic) rocks in the Wrangel Island foundation and their involvement in partial melting under granitoid magma formation.

  16. Reservoir quality in the A2C-Stringer interval of the late Neoproterozoic Ara-Group of the South Oman Salt Basin. Diagenetic relationships in space and time

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S. [RWTH Aachen (Germany). LuFG Reservoir Petrology; Reuning, L.; Kukla, P.A. [RWTH Aachen (Germany). Geological Inst.; Abe, S.; Li, Shiyan; Urai, J.L. [RWTH Aachen (Germany). Structural Geology, Tectonics and Geomechanics; Farqani, S.; Lopes Cardozo, G.; Rawahi, Z. [Petroleum Development Oman (Oman)

    2013-08-01

    The Ediacaran-Early Cambrian Ara Group of the South Oman Salt Basin consists of six carbonate to evaporite (rock salt, gypsum) sequences. These Ara Group carbonates are termed A0C to A6C from the bottom towards the top of the basin. Differential loading of locally 5 km thick Cambrian to Ordovician clastics onto the mobile rock salt of the Ara Group caused growth of isolated salt diapirs, which resulted in strong fragmentation and faulting of the carbonate intervals into several isolated so-called 'stringers'. These carbonate stringers represent a unique intra-salt petroleum system, which has been successfully explored in recent years. However, some of the stringers failed to produce at significant rates due to the complex diagenetic history from the shallow to the deep burial realm. The goal of this study is twofold. Firstly, to unravel the complex diagenesis and its relative timing and link them to the burial history of the salt basin. Secondly, to detect spatial distribution patterns of diagenetic phases and their effect on reservoir properties. Mineralogy, rock fabrics, paragenetic relationships and geochemistry of {proportional_to} 400 samples from several petroleum wells from the late Neoproterozoic A2C interval were analyzed and combined with pre-existing data. The spatial distribution of diagenetic phases and petrophysical characteristics will be displayed in field-scale distribution maps. These maps comprise crucial information for better prediction of reservoir quality in the analyzed fields, planning of new exploration wells and better volumetric calculations. An integration of the paragenetic sequence derived from thin-section analysis with results from finite element and discrete element models further helps to constrain the effect of salt tectonics on fracture formation and fluid evolution within the stringers.

  17. The Neoproterozoic Granitoids from the Qilian Block, NW China

    Science.gov (United States)

    Tung, K. A.; Yang, H. Y.; Liu, D. Y.; Zhang, J. X.; Yang, H. J.; Shau, Y. H.; Tseng, J. Y.

    2012-04-01

    Field occurrence, petrography, geochemistry, Nd isotopes, and geochronology of the Neoproterozoic granitoids exposed at Tuole, Huangyuan, Duohai, Haiyan, Riyueshan, and Maxianshan in the Qilian block were studied. The Neoproterozoic granitoids are quartz diorite, granodiorite, granite, and leucogranite. They have intruded the schists of the Huangyuan Group, the basement sequence of the Qilian block, and are medium- to coarse-grained. Gneissosities are well developed and are concordant with the schistosities of the country rocks. The Neoproterozoic granitoids plot in the field of diorite, granodiorite, and granite in (K2O+Na2O) vs. SiO2 diagram and are medium- to high-K calc-alkaline. Their REE patterns all show enrichment in LREE's and, with exception of the quartz diorite at Maxianshan, negative Eu anomalies. Their spiderdiagrams also exhibit enrichment in large ion lithophile elements, Rb, Th, U, and K and negative anomalies in Nb, Ta, Sr, P, Ti, and, with exception of the quartz diorite at Maxianshan, Ba. The ages of the Neoproterozoic granitoids are divided into two groups: ca. 800 Ma and ca. 900 Ma. The ɛNd(1 Ga) and TDM are -6.7~-12.7 and 2.2~3.0 Ga for the ca. 800 Ma granitoids and are -4.3~-5.3 and 2.0~2.3 Ga for the ca. 900 Ma granitoids. The granitoids of both age groups were all formed in arc tectonomagmatic environment on active continental margin. The Huangyuan granodiorite, Duohai leucogranite, Haiyan granodiorite, and Maxianshan granite are peraluminous and S-type, and were most probably derived from melting of clay-poor, mature psammitic sources. The Riyueshan granodiorite is metaluminous and I-type, and could have formed by solidification of partial melts of metabasalt or eclogite at pressures of 1-4 GPa. The partial melts may have assimilated MgO-rich crustal rocks before solidification. The Tuole leucogranite and Maxianshan quartz diorite are also I-type, but are weakly peraluminous. They could also have formed from partial melting of metabasalt

  18. Fluctuations in late Neoproterozoic atmospheric oxidation — Cr isotope chemostratigraphy and iron speciation of the late Ediacaran lower Arroyo del Soldado Group (Uruguay)

    DEFF Research Database (Denmark)

    Frei, Robert; Gaucher, Claudio; Stolper, Daniel

    2013-01-01

    Oxygenation of the Earth's atmosphere occurred in two major steps, near the beginning and near the end of the Proterozoic Eon (2500 to 542 Ma ago), but the details of this history are unclear. Chromium isotopes in iron-rich chemical sediments offer a potential to highlight fine-scale fluctuations...... in the oxygenation of the oceans and atmosphere and to add a further dimension in the use of redox-sensitive tracers to solve the question regarding fluctuations of atmospheric oxygen levels and their consequences for Earth's climate. We observe strong positive fractionations in Cr isotopes (d53Cr up to + 5.......0‰) in iron-rich cherts and banded iron formation horizons within the Arroyo del Soldado Group (Ediacaran; Uruguay) that can be explained by rapid, effective oxidation of Fe(II)-rich surface waters. These fluctuations are correlated with variations in ratios of highly reactive iron (FeHR) to total iron (Fetot...

  19. Reconstructing Rodinia by Fitting Neoproterozoic Continental Margins

    Science.gov (United States)

    Stewart, John H.

    2009-01-01

    Reconstructions of Phanerozoic tectonic plates can be closely constrained by lithologic correlations across conjugate margins by paleontologic information, by correlation of orogenic belts, by paleomagnetic location of continents, and by ocean floor magmatic stripes. In contrast, Proterozoic reconstructions are hindered by the lack of some of these tools or the lack of their precision. To overcome some of these difficulties, this report focuses on a different method of reconstruction, namely the use of the shape of continents to assemble the supercontinent of Rodinia, much like a jigsaw puzzle. Compared to the vast amount of information available for Phanerozoic systems, such a limited approach for Proterozoic rocks, may seem suspect. However, using the assembly of the southern continents (South America, Africa, India, Arabia, Antarctica, and Australia) as an example, a very tight fit of the continents is apparent and illustrates the power of the jigsaw puzzle method. This report focuses on Neoproterozoic rocks, which are shown on two new detailed geologic maps that constitute the backbone of the study. The report also describes the Neoproterozoic, but younger or older rocks are not discussed or not discussed in detail. The Neoproterozoic continents and continental margins are identified based on the distribution of continental-margin sedimentary and magmatic rocks that define the break-up margins of Rodinia. These Neoproterozoic continental exposures, as well as critical Neo- and Meso-Neoproterozoic tectonic features shown on the two new map compilations, are used to reconstruct the Mesoproterozoic supercontinent of Rodinia. This approach differs from the common approach of using fold belts to define structural features deemed important in the Rodinian reconstruction. Fold belts are difficult to date, and many are significantly younger than the time frame considered here (1,200 to 850 Ma). Identifying Neoproterozoic continental margins, which are primarily

  20. Carbon and Oxygen Isotope Stratigraphy of the Ediacaran Jaíba Formation, Upper Bambuí Group, Brazil: Insights into Paleogeography and Sedimentary Environments after a Neoproterozoic Glaciation.

    Science.gov (United States)

    Caxito, F.; Uhlein, G. J.; Sial, A. N.; Uhlein, A.

    2015-12-01

    The Neoproterozoic Era was a time of extreme climatic variation as recorded in sedimentary rocks of this age across the globe, leading to a number of controversial hypotheses (e.g. the Snowball Earth glaciations). In eastern Brazil, the Bambuí Gr. is a thick carbonatic-siliciclastic unit that covers the São Francisco Craton and preserves remnants of a Neoproterozoic glaciation and their respective cap carbonate (1). Recent findings of Cloudina in the Januária region (2) suggest that at least part of the sequence might be upper Ediacaran or even Cambrian. Here we present the first carbon-oxygen isotope data for the Jaíba Fm., a ca. 50 m thick carbonate unit that occurs in the topmost portion of the Bambuí Gr. in this same region. The Jaíba Fm. post-dates the cap carbonate sequence and the fossil-bearing layers, and thus was probably deposited in the Ediacaran-Cambrian transition. Three stratigraphic columns were analyzed, and yielded similar ratios. Values of δ13CVPDB are between 0.8 and 3.4 ‰, while δ18OVPDB values are mostly around -8 ‰. These values contrasts with the negative δ13C values found for the base of the Bambuí Gr., followed by highly positive δ13C (up to +14‰) on its middle portion. The unusually high δ13C values are commonly interpreted as evidence for deposition on a restricted basin, such as in a foreland setting. The return to values which are close to the PDB standard in the uppermost Bambuí Gr. might thus indicate a change in the paleogeography and tectonic environment of the basin, suggesting an open, ventilated environment along with a recovery of the biological and hydrological cycle after a Late Neoproterozoic glaciation. Ongoing detailed sedimentological, geochemical and isotopic work might help to further clarify these issues and to provide new clues for unraveling Late Neoproterozoic paleoclimate, paleogeography and ocean chemistry. We thank FAPEMIG (Brazil) for finnacial support through grants n. APQ-00914-14 and PPM

  1. Geological evolution of the Neoproterozoic Bemarivo Belt, northern Madagascar

    Science.gov (United States)

    Thomas, Ronald J.; De Waele, B.; Schofield, D.I.; Goodenough, K.M.; Horstwood, M.; Tucker, R.; Bauer, W.; Annells, R.; Howard, K. J.; Walsh, G.; Rabarimanana, M.; Rafahatelo, J.-M.; Ralison, A.V.; Randriamananjara, T.

    2009-01-01

    The broadly east-west trending, Late Neoproterozoic Bemarivo Belt in northern Madagascar has been re-surveyed at 1:100 000 scale as part of a large multi-disciplinary World Bank-sponsored project. The work included acquisition of 14 U-Pb zircon dates and whole-rock major and trace element geochemical data of representative rocks. The belt has previously been modelled as a juvenile Neoproterozoic arc and our findings broadly support that model. The integrated datasets indicate that the Bemarivo Belt is separated by a major ductile shear zone into northern and southern "terranes", each with different lithostratigraphy and ages. However, both formed as Neoproterozoic arc/marginal basin assemblages that were translated southwards over the north-south trending domains of "cratonic" Madagascar, during the main collisional phase of the East African Orogeny at ca. 540 Ma. The older, southern terrane consists of a sequence of high-grade paragneisses (Sahantaha Group), which were derived from a Palaeoproterozoic source and formed a marginal sequence to the Archaean cratons to the south. These rocks are intruded by an extensive suite of arc-generated metamorphosed plutonic rocks, known as the Antsirabe Nord Suite. Four samples from this suite yielded U-Pb SHRIMP ages at ca. 750 Ma. The northern terrane consists of three groups of metamorphosed supracrustal rocks, including a possible Archaean sequence (Betsiaka Group: maximum depositional age approximately 2477 Ma) and two volcano-sedimentary sequences (high-grade Milanoa Group: maximum depositional age approximately 750 Ma; low grade Daraina Group: extrusive age = 720-740 Ma). These supracrustal rocks are intruded by another suite of arc-generated metamorphosed plutonic rocks, known as the Manambato Suite, 4 samples of which gave U-Pb SHRIMP ages between 705 and 718 Ma. Whole-rock geochemical data confirm the calc-alkaline, arc-related nature of the plutonic rocks. The volcanic rocks of the Daraina and Milanoa groups also

  2. Accelerating Neoproterozoic Research through Scientific Drilling

    Science.gov (United States)

    Condon, Daniel; Prave, Anthony; Boggiani, Paulo; Fike, David; Halverson, Galen; Kasemann, Simone; Knoll, Andrew; Zhu, Maoyan

    2014-05-01

    The Neoproterozoic Era (1.0 to 0.541 Ga) and earliest Cambrian (541 to ca. 520 Ma) records geologic changes unlike any other in Earth history: supercontinental tectonics of Rodinia followed by its breakup and dispersal into fragments that form the core of today's continents; a rise in oxygen that, perhaps for the first time in Earth history, resulted in the deep oceans becoming oxic; snowball Earth, which envisages a blanketing of global ice cover for millions of years; and, at the zenith of these combined biogeochemical changes, the evolutionary leap from eukaryotes to animals. Such a concentration of hallmark events in the evolution of our planet is unparalleled and many questions regarding Earth System evolution during times of profound climatic and geological changes remain to be answered. Neoproterozoic successions also offer insight into the genesis of a number of natural resources. These include banded-iron formation, organic-rich shale intervals (with demonstrated hydrocarbon source rocks already economically viable in some countries), base and precious metal ore deposits and REE occurrences, as well as industrial minerals and dimension stone. Developing our understanding of the Neoproterozoic Earth-system, combined with regional geology has the potential to impact the viability of these resources. Our understanding of the Neoproterozoic and early Cambrian, though, is overwhelmingly dependent on outcrop-based studies, which suffer from lack of continuity of outcrop and, in many instances, deep weathering profiles. A limited number of research projects study Precambrian strata have demonstrated the potential impact of scientific drilling to augment and complement ongoing outcrop based studies and advancing research. An ICDP and ECORD sponsored workshop, to be held in March 2014, has been convened to discuss the utility of scientific drilling for accelerating research of the Neoproterozoic through early Cambrian (ca. 0.9 to 0.52 Ga) rock record. The aim is to

  3. Neoproterozoic magmatic activity and global change

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yongfei

    2003-01-01

    Neoproterozoic is a very important time in the history of the Earth, during which occurred supercontinent breakup, low-latitude glaciation, and biotic diversification. These concern a series of interdisciplinary studies involving ancient plate motion, climate change and life evolution, resulting in many forefront topics of general interest in the earth sciences. These include exact ages bracketing the Cryogenian System and glaciations, initial age and lasted duration of supercontinent breakup, dynamic reconstruction of China continents in supercontinental configurations, the nature of rift magmatism and extent of hydrothermal alteration, paleoclimatic implication of water-rock interaction and low-18O magmatism, and relationship between supercontinental evolution and global change. A number of outstanding advances in the above aspects have being made by Chinese scientists, leaving many important issues to be resolved: (1) did the Cryogenian start at either 800 to 820 Ma or 760 to 780 Ma? (2) was South China in the supercontinental configuration located in either southeast to Australia or north to India? (3) are Paleoproterozoic to Archean ages of crustal rocks a valid parameter in distinguishing North China from South China? Available observations suggest that Neoproterozoic mantle superwelling occurred as conspicuous magmatism in South China but as cryptical magmatism in North China. Mid-Neoproterozoic mantle superplume event and its derived rift-magmatism would not only result in the supercontinental demise, but also play a very important role in the generation and evolution of the snowball Earth event by initiating the global glaciation, causing the local deglaciation and terminating the snowball Earth event.

  4. Socioeconomic Position, But Not African Genomic Ancestry, Is Associated With Blood Pressure in the Bambui-Epigen (Brazil) Cohort Study of Aging.

    Science.gov (United States)

    Lima-Costa, M Fernanda; Mambrini, Juliana Vaz de Mello; Leite, Maria Lea Corrêa; Peixoto, Sérgio Viana; Firmo, Josélia Oliveira Araújo; Loyola Filho, Antônio Ignácio de; Gouveia, Mateus H; Leal, Thiago P; Pereira, Alexandre Costa; Macinko, James; Tarazona-Santos, Eduardo

    2016-02-01

    The study objective is to examine the role of African genome origin on baseline and 11-year blood pressure trajectories in community-based ethnoracially admixed older adults in Brazil. Data come from 1272 participants (aged ≥60 years) of the Bambui cohort study of aging during 11 years of follow-up. Outcome measures were systolic blood pressure, diastolic blood pressure, and hypertension control. Potential confounding variables were demographic characteristics, socioeconomic position (schooling and household income), and health indicators (smoking, sedentary lifestyle, high-density lipoprotein cholesterol, waist circumference, diabetes mellitus, and cardiovascular diseases), including antihypertensive drug use. We used 370 539 single-nucleotide polymorphisms to estimate each individual's African, European, and Native American trihybrid ancestry proportions. Median African, European, and Native American ancestry were 9.6%, 84.0%, and 5.3%, respectively. Among those with African ancestry, 59.4% came from East and 40.6% from West Africa. Baseline systolic and diastolic blood pressure, controlled hypertension, and their respective trajectories, were not significantly (P>0.05) associated with level (in quintiles) of African genomic ancestry. Similar results were found for West and East African subcontinental origins. Lower schooling level (blood pressure (Adjusted β=2.92; 95% confidence interval, 0.85-4.99). Lower monthly household income per capita (hypertension control (β=-0.35; 95% confidence interval, -0.63 to -0.08, respectively). Our results support the view that favors social and environmental factors as determinants of blood pressure and hypertension control.

  5. 滇南新元古代的岩浆作用:来自瑶山群深变质岩SHRIMP锆石U-Pb年代学证据%Neoproterozoic Magmatism in South Yunnan: Evidence from SHRIMP Zircon U-Pb Geochrological Results of High-Grade Metamorphic Rocks in the Yaoshan Group

    Institute of Scientific and Technical Information of China (English)

    李宝龙; 季建清; 王丹丹; 马宗晋

    2012-01-01

    The Lower Proterozoic Yaoshan Group and Ailao Shan Group, composed of high-grade metamorphosed rocks, is a long, narrow belt striking NW-SE direction along the Red River fault, and are considered the Precambrian crystalline basement. In this paper, the SHRIMP zircon U-Pb dating have been conducted on the augen granitic mylonite (08HK-1) from the Yaoshan Group (Lianhuatan, Hekou County) and gneissic granite (08JP-5, Adebo,Jinping County), and ages of two magmatic zircon groups are 828 + 6. 2Ma (N=ll, MSWD= 1.8) and 748~801Ma, respectively. In addition, the SHRIMP zircon U-Pb ages of 769~893Ma were obtained on biotite granodioritic gneiss from the Ailao Shan Group in Mojiang-Yuanjiang section. Combined with the crystal features, CL images and concordant of U-Pb age, 828 6. 2Ma and 748~801Ma should present the crystal age. These ages suggested that there should have the Neoproterozoic magmatism in the study area. The SHRIMP zircon U-Pb dating on old core from sample 08HK-1 has the age of 984Ma, and the 08JP-5 sample has the old core zircon U-Pb age of 1104~ 1353Ma and even 2655Ma. The old core zircon age show that the Yaoshan area and southern part of Ailao Shan should be a Mesproterozoic or Archea basement. Based on these isotopic geochronological data above and regional geological tectonic evolution, the Yaoshan area and southern part of Ailao Shan should located in the cross region of the Nanhua Rift and the Kangdian Rift during breaking-up of the Rodinian Super-continent in the Neoproterozoic.%滇南瑶山哀牢山地区出露一套呈NW-SE向狭长条带状展布的深变质岩系——下元古界瑶山群和哀牢山群,并认为存在前寒武纪的结晶基底.本文选取瑶山群眼球状花岗质糜棱岩和金平阿得博的片麻状花岗岩作为研究对象,进行SHRIMP锆石U-Pb定年.结合阴极发光图像,获得岩浆锆石的结晶年龄为828±6.2Ma(N=11,MSWD=1.8)和748~801Ma.同时,作者在墨江-元江剖面的哀牢山群黑

  6. Organic matter in the Neoproterozoic cap carbonate from the Amazonian Craton, Brazil

    Science.gov (United States)

    Sousa Júnior, Gustavo R.; Nogueira, Afonso C. R.; Santos Neto, Eugênio V.; Moura, Candido A. V.; Araújo, Bruno Q.; Reis, Francisco de A. M.

    2016-12-01

    Bitumen found in Neoproterozoic carbonates from the southern Amazonian Craton, Brazil, represents a great challenge for its geochemical characterization (origin, thermal maturity and the degree of preservation) within a context of petroleum system. This organic material occurs in the basal Araras Group, considered as a Neoproterozoic cap carbonate, composed of dolostones (Mirassol d'Oeste Formation) overlaid by limestones and shales (Guia Formation). Geochemical analyses in samples of carbonate with bitumen from two open pits (Terconi and Tangará quarries) have shown low to very low total organic carbon content. Analyses of representative samples of Guia and Mirassol d'Oeste formations allowed us to obtain Gas chromatography (GC) traces and diagnostic biomarkers. n-C14 to n-C37 alkane distribution patterns in all samples suggests a major contribution of marine algae. Mid-chain monomethyl alkanes (C14sbnd C25) identified in both sets of samples were also reported in all mid to late Proterozoic oils and source rocks. However, there are significant differences among terpane distribution between the Mirassol d'Oeste and Tangará da Serra regions. The integration of organic geochemistry data and geological information suggests an indigenous origin for studied bitumen, primarily accumulated as hydrocarbon fluids migrated to carbonate rocks with higher porosity and permeability, and afterwards, altered to bitumen or migrabitumen. Although further investigations are required, this work provides a significant contribution to the knowledge about the remnant of this hypothetical Neoproterozoic petroleum system developed in the Southern Amazonian Craton.

  7. Ferruginous conditions dominated later neoproterozoic deep-water chemistry.

    Science.gov (United States)

    Canfield, Donald E; Poulton, Simon W; Knoll, Andrew H; Narbonne, Guy M; Ross, Gerry; Goldberg, Tatiana; Strauss, Harald

    2008-08-15

    Earth's surface chemical environment has evolved from an early anoxic condition to the oxic state we have today. Transitional between an earlier Proterozoic world with widespread deep-water anoxia and a Phanerozoic world with large oxygen-utilizing animals, the Neoproterozoic Era [1000 to 542 million years ago (Ma)] plays a key role in this history. The details of Neoproterozoic Earth surface oxygenation, however, remain unclear. We report that through much of the later Neoproterozoic (<742 +/- 6 Ma), anoxia remained widespread beneath the mixed layer of the oceans; deeper water masses were sometimes sulfidic but were mainly Fe2+-enriched. These ferruginous conditions marked a return to ocean chemistry not seen for more than one billion years of Earth history.

  8. Testing the "Mudball Earth" Hypothesis: Are Neoproterozoic Glacial Deposits Capped with Supraglacial Dust?

    Science.gov (United States)

    Goodman, J. C.; Alvim Lage, C.

    2014-12-01

    The Snowball Earth hypothesis has inspired several variants which may help to explain some of the great mysteries of the Neoproterozoic glaciations. One of these, the "Mudball Earth", proposes that as the Earth remained completely frozen for millions of years, a layer of dust accumulated on the ice surface. This dust layer would darken the planet, making it easier for the Earth to escape from the highly stable snowball climate state. This hypothesis is testable: after the ice melted at the end of a glacial era, this dust would sink to the bottom of the ocean, possibly forming a distinct clay, mud, or silt layer on the top of the glacial till deposits: this "clay drape" would then be covered by the cap carbonates that mark a return to warm climate. Sublimation and ice flow during the glacial episode should make this layer thicker at the equator and thinner or absent in the poles. Is this clay layer actually present in the rock record? Is it more prevalent at the paleoequator, as predicted? A clay drape has been noticed anecdotally, but no global survey has been done to date. We conducted a thorough literature review of all sites where Neoproterozoic glacial diamictites have been observed, identifying the type of rock that lies between the diamictite and the postglacial cap carbonate, when present, during both Sturtian and Marinoan glacial periods. Only a few publications identify a distinct clay/silt/mud layer that might represent weathered dust. These sites are not grouped by paleolatitude in any obvious way. With access only to published reports, we cannot determine whether such a layer is absent, went unreported, or was misinterpreted by us. With this work we hope to attract the attention of Neoproterozoic field geologists, inviting them to comment on the presence or absence of strata which could confirm or reject the "Mudball" hypothesis.

  9. Neoproterozoic diamictite-cap carbonate succession and δ13C chemostratigraphy from eastern Sonora, Mexico

    Science.gov (United States)

    Corsetti, Frank A.; Stewart, John H.; Hagadorn, James W.

    2007-01-01

    Despite the occurrence of Neoproterozoic strata throughout the southwestern U.S. and Sonora, Mexico, glacial units overlain by enigmatic cap carbonates have not been well-documented south of Death Valley, California. Here, we describe in detail the first glaciogenic diamictite and cap carbonate succession from Mexico, found in the Cerro Las Bolas Group. The diamictite is exposed near Sahuaripa, Sonora, and is overlain by a 5 m thick very finely-laminated dolostone with soft sediment folds. Carbon isotopic chemostratigraphy of the finely-laminated dolostone reveals a negative δ13C anomaly (down to − 3.2‰ PDB) characteristic of cap carbonates worldwide. Carbon isotopic values rise to + 10‰ across ∼ 400 m of section in overlying carbonates of the Mina el Mezquite and Monteso Formations. The pattern recorded here is mostly characteristic of post-Sturtian (ca. ≤ 700 Ma), but pre-Marinoan (ca. ≥ 635 Ma) time. However, the Cerro Las Bolas Group shares ambiguity common to most Neoproterozoic successions: it lacks useful radiometric age constraints and biostratigraphically useful fossils, and its δ13C signature is oscillatory and therefore somewhat equivocal.

  10. Is the Neoproterozoic oxygen burst a supercontinent legacy?

    Directory of Open Access Journals (Sweden)

    Melina eMacouin

    2015-09-01

    Full Text Available The Neoproterozoic (1000–542 Myr ago witnessed the dawn of Earth as we know it with modern-style plate tectonics, high levels of O2 in atmosphere and oceans and a thriving fauna. Yet, the processes leading to the fully oxygenation of the external envelopes, its exact timing and its link with the inner workings of the planet remain poorly understood. In some ways, it is a chicken and egg question: did the Neoproterozoic Oxygenation Event (NOE cause life blooming, low-latitudes glaciations and perturbations in geochemical cycles or is it a consequence of these phenomena? Here, we suggest that the NOE may have been triggered by multi-million years oxic volcanic emissions along a protracted period at the end of the Neoproterozoic when continents were assembled in the Rodinia supercontinent. We report a very oxidized magma source at the upper mantle beneath a ring of subducting margins around Rodinia, and detail here the evidence at the margin of the Arabian shield. We investigate the 780 Ma Biotite and Pink granites and associated rocks of the Socotra Island with rock magnetic and petrographic methods. Magnetic susceptibility and isothermal remanent magnetization acquisitions show that, in these granites, both magnetite and hematite are present. Hematite subdivides magnetite grains into small grains. Magnetite and hematite are found to be primary, and formed at the early magmatic evolution of the granite at very high oxygen fugacity. Massive degassing of these oxidized magmas would reduce the sink for oxygen, and consequently contribute to its rise in the atmosphere with a net O2 flux of at least 2.25 x 107 Tmol. Our conceptual model provides a deep Earth link to the NOE and implies the oxygenation burst has occurred earlier than previously envisaged, paving the way for later changes in the outer envelopes of the planet epitomized on the extreme Neoproterozoic glaciations and the appearance of the first animals.

  11. Is the Neoproterozoic oxygen burst a supercontinent legacy?

    Science.gov (United States)

    Macouin, Melina; Roques, Damien; Rousse, Sonia; Ganne, Jerome; Denele, Yoann; Trindade, Ricardo

    2015-09-01

    The Neoproterozoic (1000-542 Myr ago) witnessed the dawn of Earth as we know it with modern-style plate tectonics, high levels of O2 in atmosphere and oceans and a thriving fauna. Yet, the processes leading to the fully oxygenation of the external envelopes, its exact timing and its link with the inner workings of the planet remain poorly understood. In some ways, it is a "chicken and egg" question: did the Neoproterozoic Oxygenation Event (NOE) cause life blooming, low-latitudes glaciations and perturbations in geochemical cycles or is it a consequence of these phenomena? Here, we suggest that the NOE may have been triggered by multi-million years oxic volcanic emissions along a protracted period at the end of the Neoproterozoic when continents were assembled in the Rodinia supercontinent. We report a very oxidized magma source at the upper mantle beneath a ring of subducting margins around Rodinia, and detail here the evidence at the margin of the Arabian shield. We investigate the 780 Ma Biotite and Pink granites and associated rocks of the Socotra Island with rock magnetic and petrographic methods. Magnetic susceptibility and isothermal remanent magnetization acquisitions show that, in these granites, both magnetite and hematite are present. Hematite subdivides magnetite grains into small grains. Magnetite and hematite are found to be primary, and formed at the early magmatic evolution of the granite at very high oxygen fugacity. Massive degassing of these oxidized magmas would reduce the sink for oxygen, and consequently contribute to its rise in the atmosphere with a net O2 flux of at least 2.25 x 107 Tmol. Our conceptual model provides a deep Earth link to the NOE and implies the oxygenation burst has occurred earlier than previously envisaged, paving the way for later changes in the outer envelopes of the planet epitomized on the extreme Neoproterozoic glaciations and the appearance of the first animals.

  12. Paleoclimate and evolution: emergence of sponges during the neoproterozoic.

    Science.gov (United States)

    Müller, Werner E G; Wang, Xiaohong; Schröder, Heinz C

    2009-01-01

    In the last 15 years, we had to cope with many technological and conceptual obstacles. The major hindrance was the view that sponges are primitive and exist separated from the other metazoan organisms. After answering these problems, the painful scientific process to position the most enigmatic metazoan phylum, the Porifera, into the correct phylogenetic place among the eukaryotes in general and the multicellular animals in particular came to an end. The well-studied taxon Porifera (sponges) was first grouped to the animal-plants or plant-animals, then to the Zoophyta or Mesozoa, and finally to the Parazoa. Only by the application of molecular biological techniques was it possible to place the Porifera monophyletically with the other metazoan phyla, justifying a unification of all multicellular animals to only one kingdom, the Metazoa. The first strong support came from the discovery that cell-cell and cell-matrix adhesion molecules, that were cloned from sponges (mainly the demosponges Suberites domuncula and Geodia cydonium) and that were subsequently expressed, share high DNA sequence and protein function similarity with the corresponding molecules of other metazoans. Together with the molecular biological studies and with the use of the cell culture technologies (primmorphs), which allowed an insight into the stem cell system of these simple organisms, it was possible to stethoscope back in the paleontological history of animals. These studies confirmed the view that the sponges evolved between two epochal ice times, 710-680 Ma (Sturtian glaciation) and 605-585 Ma (Varanger-Marinoan ice age), a period which allowed evolution to proceed but resulted also in a mass extinction of most animal taxa, with the exception of the Porifera. These animals could develop in the aqueous milieu which was rich in silica, due also to their ability to live in a symbiosis with unicellular organisms (prokaryotic and also eukaryotic). Those organisms provided the sponges with the

  13. Inventory of Neoproterozoic and Paleozoic strata in Sonora, Mexico

    Science.gov (United States)

    Stewart, John H.; Poole, Forrest G.

    2002-01-01

    This compilation is an inventory of all known outcrops of Neoproterozoic and Paleozoic strata in Sonora, Mexico. We have not attempted an interpretation of the regional stratigraphic or structural setting of the strata. Brief summaries of the stratigraphic setting of the Sonora rocks are given in Poole and Hayes (1971), Rangin (1978), Stewart and others (1984, 1990), and Poole and Madrid (1986; 1988b). More specific information on the setting of strata of specific ages are given by Stewart and others (2002) for the Neoproterozoic and Cambrian; by Poole and others (1995a) for Ordovician shelf strata; by Poole and others (1995b) for Ordovician deep-water openbasin strata; by Poole and others (1997, 1998, 2000a) for Silurian strata; and by Poole and others (2000a) for Mississippian strata. Other reports that discuss regional aspects of Paleozoic stratigraphy include López-Ramos (1982), Peiffer-Rangin, (1979, 1988), Pérez-Ramos (1992), and Stewart and others (1997, 1999a). Structurally, the major Paleozoic feature of Sonora is the Sonora allochthon, consisting of deep-water (eugeoclinal) strata emplaced in the Permian over shelf (miogeoclinal) deposits (Poole and others, 1995a,b; Poole and Perry, 1997; 1998). The emplacement structure is generally considered to be a major Permian continental margin thrust fault that emplaced the deep-water rocks northward over shelf (miogeoclinal) deposits. An alternate interpretation has been presented by Stewart and others (2002). He proposed that the emplacement of the Sonora allochthon was along a major Permian transpressional structure that was primarily a strike-slip fault with only a minor thrust component . The Mojave-Sonora megashear has been proposed to disrupt Neoproterozoic and Paleozoic trends in Sonora. This feature is a hypothetical, left-lateral, northwest-striking fault extending across northern Sonora and the southwestern United States (Silver and Anderson, 1974; Anderson and Schmidt, 1983). It is proposed to have

  14. A true polar wander model for Neoproterozoic plate motions

    Energy Technology Data Exchange (ETDEWEB)

    Ripperdan, R.L. (Weizmann Inst. of Science, Rehovot (Israel))

    1992-01-01

    Recent paleogeographic reconstructions for the interval 750--500 Ma (Neoproterozoic to Late Cambrian) require rapid rates of plate motion and/or rotation around an equatorial Euler pole to accommodate reconstructions for the Early Paleozoic. Motions of this magnitude appear to be very uncommon during the Phanerozoic. A model for plate motions based on the hypothesis that discrete intervals of rapid true polar wander (RTPW) occurred during the Neoproterozoic can account for the paleogeographic changes with minimum amounts of plate motion. The model uses the paleogeographic reconstructions of Hoffman (1991). The following constraints were applied during derivation of the model: (1) relative motions between major continental units were restricted to be combinations of great circle or small circle translations with Euler poles of rotation = spin axis; (2) maximum rates of relative translational plate motion were 0.2 m/yr. Based on these constraints, two separate sets of synthetic plate motion trajectories were determined. The sequence of events in both can be summarized as: (1) A rapid true polar wander event of ca 90[degree] rafting a supercontinent to the spin axis; (2) breakup of the polar supercontinent into two fragments, one with the Congo, West Africa, Amazonia, and Baltica cratons, the other with the Laurentia, East Gondwana, and Kalahari cratons; (3) great circle motion of the blocks towards the equator; (4) small circle motion leading to amalgamation of Gondwana and separation of Laurentia and Baltica. In alternative 1, rifting initiates between East Antarctica and Laurentia and one episode of RTPW is required. Alternative 2 requires two episodes of RTPW; and that rifting occurred first along the eastern margin and later along the western margin of Laurentia. Synthetic plate motion trajectories are compared to existing paleomagnetic and geological data, and implications of the model for paleoclimatic changes during the Neoproterozoic are discussed.

  15. Phosphatized multicellular algae in the Neoproterozoic Doushantuo Formation, China, and the early evolution of florideophyte red algae.

    Science.gov (United States)

    Xiao, Shuhai; Knoll, Andrew H; Yuan, Xunlai; Pueschel, Curt M

    2004-02-01

    Phosphatic sediments of the Late Neoproterozoic (ca. 600 million years old [Myr]) Doushantuo Formation at Weng'an, South China, contain fossils of multicellular algae preserved in anatomical detail. As revealed by light microscopy and scanning electron microscopy, these fossils include both simple pseudoparenchymatous thalli with apical growth but no cortex-medulla differentiation and more complex thalli characterized by cortex-medulla differentiation and structures interpretable as carposporophytes, suggesting a multiphasic life cycle. Simple pseudoparenchymatous thalli, represented by Wengania, Gremiphyca, and Thallophycoides, are interpreted as stem group florideophytes. In contrast, complex pseudoparenchymatous thalli, such as Thallophyca and Paramecia, compare more closely to fossil and living corallinaleans than to other florideophyte orders, although they also differ in some important aspects (e.g., lack of biocalcification). These more complex thalli are interpreted as early stem group corallinaleans that diverged before Paleozoic stem groups such as Arenigiphyllum, Petrophyton, Graticula, and Archaeolithophyllum. This phylogenetic interpretation implies that (1) the phylogenetic divergence between the Florideophyceae and its sister group, the Bangiales, must have taken place before Doushantuo time-an inference supported by the occurrence of bangialean fossils in Mesoproterozoic rocks; (2) the initial diversification of the florideophytes occurred no later than the Doushantuo time; and (3) the corallinalean clade had a "soft" (uncalcified) evolutionary history in the Neoproterozoic before evolving biocalcification in the Paleozoic and undergoing crown group diversification in the Mesozoic.

  16. The Neoproterozoic oxygenation event: Environmental perturbations and biogeochemical cycling

    Science.gov (United States)

    Och, Lawrence M.; Shields-Zhou, Graham A.

    2012-01-01

    The oxygen content of the Earth's surface environment is thought to have increased in two broad steps: the Great Oxygenation Event (GOE) around the Archean-Proterozoic boundary and the Neoproterozoic Oxygenation Event (NOE), during which oxygen possibly accumulated to the levels required to support animal life and ventilate the deep oceans. Although the concept of the GOE is widely accepted, the NOE is less well constrained and its timing and extent remain the subjects of debate. We review available evidence for the NOE against the background of major climatic perturbations, tectonic upheaval related to the break-up of the supercontinent Rodinia and reassembly into Gondwana, and, most importantly, major biological innovations exemplified by the Ediacarian Biota and the Cambrian 'Explosion'. Geochemical lines of evidence for the NOE include perturbations to the biogeochemical cycling of carbon. Generally high δ 13C values are possibly indicative of increased organic carbon burial and the release of oxidative power to the Earth's surface environment after c. 800 Ma. A demonstrably global and primary record of extremely negative δ 13C values after about 580 Ma strongly suggests the oxidation of a large dissolved organic carbon pool (DOC), the culmination of which around c. 550 Ma coincided with an abrupt diversification of Ediacaran macrobiota. Increasing 87Sr/ 86Sr ratios toward the Neoproterozoic-Cambrian transition indicates enhanced continental weathering which may have fuelled higher organic production and burial during the later Neoproterozoic. Evidence for enhanced oxidative recycling is given by the increase in sulfur isotope fractionation between sulfide and sulfate, exceeding the range usually attained by sulfate reduction alone, reflecting an increasing importance of the oxidative part in the sulfur cycle. S/C ratios attained a maximum during the Precambrian-Cambrian transition, further indicating higher sulfate concentrations in the ocean and a

  17. Chemostratigraphy of early Neoproterozoic sedimentary rocks of Yenisei ridge (Siberia, Russia)

    Science.gov (United States)

    Vishnevskaya, Irina; Pisareva, Natalia; Kanygina, Nadejda; Proshenkin, Artem

    2014-05-01

    One of the biggest Proterozoic sedimentary basins in Russia is around the Siberian platform. This study about little part of them - Neoproterozoic sedimentary rocks of Yenisei ridge (Southwestern margin of Siberian Platform). Thise geological structure is ancient and very difficult for reaserch. It is a collage of different blocks: volcanic arcks, ophiolite complexes and sedimentary rocks of various ages and degrees of metamorphism. Sedimentary complexes of Siberian platform are outcropping along Angara River and its tributary. Neoproterozoic ones are presented by terrigenous-carbonate rocks of Tungusik and Oslyan groups. Despite the long study history of the area is still controversial question of time of formation of these rocks. As determination of the age of Precambrian sedimentary rocks is very difficult, Sr isotopic chemostratigraphy appears to be the only approach to establish the age of carbonate sequences. All Rb-Sr author's data was investigated by the method of selective dissolution with the preliminary removal of epigenetic carbonate phases. The isotope dilution method with mixed 87Rb + 84Sr spike was used to determine Rb and Sr concentrations in both fractions on the MI 1201AT mass spectrometer. Sr isotope ratios were measured on the Finnigan MAT-262 (BAC CU, Irkutsk, Russia) and Triton Plus (IGG UB RAS, Ekaterinburg, Russia). The C-O isotopic composition in carbon samples was measured on the Finnigan MAT-253 equipment. The main criteria for integrity were correlations of impurity-elements (Mn, Fe, Sr) and stable isotopes (C, O) with each other. The less altered rocks of the Tungusik Group are characterized by 87Sr/86Sr ratio of 0.7055-0.7058, and wide variations in the δ13CPDB values from 0 to +5o [1]. The primary 87Sr/86Sr of Dashka Formation (Oslyan Group) is 0.7057 - 0.7060 and δ13CPDB value varies in interval 3.7-4.3o like in upper part of Tungusik Group. High positive values of δ13CPDB indicate that carbonates had accumulated in warm sea

  18. Towards a quantitative understanding of the late Neoproterozoic carbon cycle

    DEFF Research Database (Denmark)

    Bjerrum, Christian J.; Canfield, Donald Eugene

    2011-01-01

    The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late...... Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features...... of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today....

  19. The tectonic evolution of the Neoproterozoic Brasília Belt, central Brazil: a geochronological and isotopic approach

    Directory of Open Access Journals (Sweden)

    Márcio Martins Pimentel

    Full Text Available ABSTRACT: The Brasília Belt is one of the most complete Neoproterozoic orogens in western Gondwana. Rapid progress on the understanding of the tectonic evolution of the belt was achieved due to new U-Pb data, combined with Sm-Nd and Lu-Hf analyses. The evolution of the Brasília orogen happened over a long period of time (900 - 600 Ma involving subduction, magmatism and terrain accretion, as a result of the consumption of the Goiás oceanic lithosphere. Provenance studies, based on U-Pb zircon data, indicate that the sedimentary rock units record different tectonic settings and stages of the evolution of the orogen. The Paranoá and Canastra groups represent passive margin sequences derived from the erosion of the São Francisco Craton. The Araxá and Ibiá groups, however, have dominant Neoproterozoic detrital zircon populations, as young as 650 Ma, suggesting derivation from the Goiás Magmatic Arc. The Goiás Magmatic Arc represents a composite arc terrain, formed by the accretion of older (ca. 0.9 - 0.8 Ga intraoceanic island arc(s, followed by more evolved continental arcs. It extends for several thousand kilometers, from SW Goiás, through NE Brazil and into Africa. Metamorphism took place between 650 - 630 Ma reflecting final closure of the Goiás Ocean and continental collision.

  20. Integrated Geochemical-Petrographic Insights on Neoproterozoic Ocean Oxygenation

    Science.gov (United States)

    Hood, A.; Planavsky, N.; Wallace, M. W.; Wang, X.; Gueguen, B.

    2015-12-01

    Novel isotope systems have the potential to provide new insights into biogeochemical cycling in Earth's evolving oceans. However, much recent paleo-redox work has been done without extensive consideration of sample preservation or paleoenvironmental setting. Neoproterozoic reef complexes from South Australia provide a perfect setting to test geochemical redox proxies (e.g. uranium isotopes and trace metal chemistry) within a well-defined sedimentological and petrographic context. These reefs developed significant frameworks over ~1km of steep platform relief from the seafloor, and contain a variety of carbonate components including primary dolomite marine cements. Analysis of a variety of components within these reefs reveals significant variation in uranium isotope composition and trace metal chemistry between components, even within a single sample. Marine cements, which precipitated directly from seawater, have much lower contamination element concentrations (e.g. Al, Zr, Th) than depositional micrites, and appear to represent the best archive of ancient ocean conditions. These cements have high levels of Fe, Mn in shallow and deep reef facies (e.g. 2-3wt% Fe), but only Fe-oxide inclusions in peritidal settings. This distribution suggests ferruginous conditions under a surficial chemocline in this Neoproterozoic seawater. Uranium isotopes from pristine marine cements have relatively heavy values compared to modern seawater (median = -0.22 δ238U). These values are essentially unfractionated from riverine inputs, which we interpret as tracking extensive near quantitative low-T reduction of U(VI) to U(IV) by abundant soluble iron in seawater. Depositional components and late stage cements have a much lighter and more variable U isotope compositions (-0.71 to -0.08 δ238U). This work highlights the need for fundamental petrographic constraints on the preservation of depositional geochemical signatures in the future use and development of sedimentary redox proxies.

  1. Field relations, petrology, and structure of neoproterozoic rocks in the Caledonian Highlands, southern New Brunswick

    Energy Technology Data Exchange (ETDEWEB)

    Barr, S. M. [Acadia Univ., Dept. of Geology, Wolfville, NS (Canada); White, C. E. [Nova Scotia Dept. of Natural Resources, Halifax, NS (Canada)

    1999-05-01

    Geology of the Caledonian Highlands of southern New Brunswick is described. The Highlands consist dominantly of Late Neoproterozoic rocks generally considered typical of the northern Appalachian Orogen. The eastern Caledonian Highlands consist mainly of tuffaceous metavolcanic and metasedimentary rocks of the Broad River Group and cogenetic dioritic to granitic plutons with ages about 620 Ma. The western highlands are formed of mostly younger (560-550 Ma) volcanic and clastic sedimentary rocks of the Coldbrook Group. The Broad River Group was deformed, regionally metamorphosed to greenschist facies, and locally mylonitized prior to deposition of the uncomformably overlying Coldbrook Group. Both units were folded and slightly metamorphosed, probably during the Silurian and Devonian. This event may have been related to juxtaposition with terranes to the northwest. Contrary to previous interpretations, it is now recognized that the volcanic and sedimentary rocks in the Caledonian Highlands do not belong to a single stratigraphic assemblage. This is considered to be a major advance in the understanding of the geological evolution of the area. 138 refs., 4 tabs., 56 figs.

  2. Microanalyzes of remarkable microfossils of the Late Mesoproterozoic-Early Neoproterozoic

    Science.gov (United States)

    Cornet, Yohan; Beghin, Jérémie; Baludikay, Blaise; François, Camille; Storme, Jean-Yves; Compère, Philippe; Javaux, Emanuelle

    2016-04-01

    The Late Mesoproterozoic-Early Neoproterozoic is an important period to investigate the diversification of early eukaryotes [1]. Following the first appearance of red algae in the Late Mesoproterozoic, other (morphological or molecular) fossils of crown groups are recorded during the Early Neoproterozoic, including green algae, sponges, amoebozoa and possibly fungi. Other microfossils also includes unambiguous eukaryotes, including several distinctive forms for that time period, such as the acritarchs Cerebrosphaera buickii (˜820-720 Ma), Trachyhystrichosphaera aimika and T . botula (1100-720 Ma), and the multicellular eukaryotic problematicum taxon Jacutianema solubila (1100-?720 Ma). To further characterize the taxonomy of these microfossils and to test hypotheses about their possible relationships to crown groups, we combine analyzes of their morphology, wall ultrastructure and microchemistry, using optical microscopy, Scanning and Transmission Electron microscopy (SEM and TEM), as well as Raman and FTIR microspectroscopy respectively. Cerebrosphaera populations from the Svanbergfjellet formation, Spitsbergen, and from the Kanpa Formation, Officer Basin, Australia, include organic vesicles with dark and robust walls ornamented by cerebroid folds [2]. Our study shows the occurrence of complex tri- or bi-layered wall ultrastructures and a highly aromatic composition [3]. The genus Trachyhystrichosphaera includes various species characterized by the presence of a variable number of hollow heteromorphic processes [2]. Preliminary infrared microspectroscopy analyzes performed on two species, T. aimika and T. botula, from the 1.1 Ga Taoudeni Basin, Mauritania, and from the ˜1.1 - 0.8 Ga Mbuji-Mayi Supergroup, RDC, indicate a strong aliphatic and carbonyl composition of the wall biopolymer, with some differences linked to thermal maturity between the two locations. TEM is also performed to characterize the wall ultrastructure of these two species. Various morphotypes

  3. A neoproterozoic transition in the marine nitrogen cycle.

    Science.gov (United States)

    Sánchez-Baracaldo, Patricia; Ridgwell, Andy; Raven, John A

    2014-03-17

    The Neoproterozoic (1000-542 million years ago, Mya) was characterized by profound global environmental and evolutionary changes, not least of which included a major rise in atmospheric oxygen concentrations [1, 2], extreme climatic fluctuations and global-scale glaciation [3], and the emergence of metazoan life in the oceans [4, 5]. We present here phylogenomic (135 proteins and two ribosomal RNAs, SSU and LSU) and relaxed molecular clock (SSU, LSU, and rpoC1) analyses that identify this interval as a key transition in the marine nitrogen cycle. Specifically, we identify the Cryogenian (850-635 Mya) as heralding the first appearance of both marine planktonic unicellular nitrogen-fixing cyanobacteria and non-nitrogen-fixing picocyanobacteria (Synechococcus and Prochlorococcus [6]). Our findings are consistent with the existence of open-ocean environmental conditions earlier in the Proterozoic adverse to nitrogen-fixers and their evolution-specifically, insufficient availability of molybdenum and vanadium, elements essential to the production of high-yielding nitrogenases. As these elements became more abundant during the Cryogenian [7, 8], both nitrogen-fixing cyanobacteria and planktonic picocyanobacteria diversified. The subsequent emergence of a strong biological pump in the ocean implied by our evolutionary reconstruction may help in explaining increased oxygenation of the Earth's surface at this time, as well as tendency for glaciation.

  4. Annelid from the Neoproterozoic Doushantuo Formation in Northeastern Guizhou, China

    Institute of Scientific and Technical Information of China (English)

    WANG Yue; WANG Xunlian

    2008-01-01

    Wenghuiia jiangkouensis gen. et sp. nov., characterized by modem annelid taxonomy in morphology and functional biology, is found in black carbonaceous shale from the Neoproterozoic Ediacaran Doushantuo Formation (about 555 Ma) near Wenghui, Jiangkou, northeastern Guizhou Province. The elongate, cylindrical body is composed of many homologous metameres with a true coelom and coelomic pouches. The mouth is at the front of the first segment and the anus at the end of body. A long 11th or 12th segment is probably functionally for procreation, being a clitellum. There are parapodia on the venter of the segments from the rear of the second segment to the front of the clitellum. The setae on all metameres, on the parapodia, and around the anus, differ. In the centre of body, a line probably represents the alimentary canal passing through the body from mouth to anus. A closed vascular system consists of a dorsal vessel at least. W. jiankouensis might represent the oldest discovered 'modem' annelid but it is not a primitive type. It lived on the depositional surface of a shallow sea with an environment of calm-water and abundant light.

  5. Provenance of Neoproterozoic sedimentary basement of northern Iran, Kahar Formation

    Science.gov (United States)

    Etemad-Saeed, Najmeh; Hosseini-Barzi, Mahboubeh; Adabi, Mohammad Hossein; Sadeghi, Abbas; Houshmandzadeh, Abdolrahim

    2015-11-01

    This article presents new data to understand the nature of the hidden crystalline basement of northern Iran and the tectonic setting of Iran during late Neoproterozoic time. The siliciclastic-dominated Kahar Formation represents the oldest known exposures of northern Iran and comprises late Ediacaran (ca. 560-550 Ma) compositionally immature sediments including mudrocks, sandstones, and conglomerates. This work focuses on provenance of three well preserved outcrops of this formation in Alborz Mountains: Kahar Mountain, Sarbandan, and Chalus Road, through petrographic and geochemical methods. Mineralogical Index of Alteration (MIA) and Chemical Index of Alteration (CIA-after correction for K-metasomatism) values combined with A-CN-K relations suggest moderate weathering in the source areas. The polymictic nature of Kahar conglomerates indicates a mixed provenance for them. However, modal analysis of Kahar sandstones (volcanic to plagioclase-rich lithic arkose) and whole rock geochemistry of mudrocks suggest that they are largely first-cycle sediments and that their sources were remarkably late Ediacaran, intermediate-felsic igneous rocks from proximal arc settings. Tectonic setting discrimination diagrams also indicate a convergent plate margin and continental arc related basin for Kahar sediments. This interpretation is supported by the phyllo-tectic to tectic composition and geochemistry of mudrocks. These results reveal the presence of a felsic/intermediate subduction-related basement (∼600-550 Ma) in this region, which provides new constraints on subduction scenario during this time interval in Iran, as a part of the Peri-Gondwanan terranes.

  6. Polyphase Neoproterozoic orogenesis within the east Africa- Antarctica orogenic belt in central and northern Madagascar

    Science.gov (United States)

    Key, R.M.; Pitfield, P.E.J.; Thomas, Ronald J.; Goodenough, K.M.; Waele, D.; Schofield, D.I.; Bauer, W.; Horstwood, M.S.A.; Styles, M.T.; Conrad, J.; Encarnacion, J.; Lidke, D.J.; O'connor, E. A.; Potter, C.; Smith, R.A.; Walsh, G.J.; Ralison, A.V.; Randriamananjara, T.; Rafahatelo, J.-M.; Rabarimanana, M.

    2011-01-01

    Our recent geological survey of the basement of central and northern Madagascar allowed us to re-evaluate the evolution of this part of the East Africa-Antarctica Orogen (EAAO). Five crustal domains are recognized, characterized by distinctive lithologies and histories of sedimentation, magmatism, deformation and metamorphism, and separated by tectonic and/or unconformable contacts. Four consist largely of Archaean metamorphic rocks (Antongil, Masora and Antananarivo Cratons, Tsaratanana Complex). The fifth (Bemarivo Belt) comprises Proterozoic meta-igneous rocks. The older rocks were intruded by plutonic suites at c. 1000 Ma, 820-760 Ma, 630-595 Ma and 560-520 Ma. The evolution of the four Archaean domains and their boundaries remains contentious, with two end-member interpretations evaluated: (1) all five crustal domains are separate tectonic elements, juxtaposed along Neoproterozoic sutures and (2) the four Archaean domains are segments of an older Archaean craton, which was sutured against the Bemarivo Belt in the Neoproterozoic. Rodinia fragmented during the early Neoproterozoic with intracratonic rifts that sometimes developed into oceanic basins. Subsequent Mid- Neoproterozoic collision of smaller cratonic blocks was followed by renewed extension and magmatism. The global 'Terminal Pan-African' event (560-490 Ma) finally stitched together the Mid-Neoproterozoic cratons to form Gondwana. ?? The Geological Society of London 2011.

  7. Phanerozoic and Neoproterozoic Negative Carbon Isotope Excursions, Diagenesis and Terrestrialization

    Science.gov (United States)

    Paul, K.; Kennedy, M. J.

    2008-12-01

    Comprehensive data sets of Phanerozoic and late Precambrian carbon isotope data derived from carbonate rocks show a similar positive relation when cross-plotted with oxygen isotope values. The range and slope between the time periods is identical and the processes responsible for the relation have been well documented in Quaternary sediments. These processes include the stabilization of isotope values to ambient meteoric water values during shallow burial and flushing of carbonate sediments. Both data sets show strongly depleted carbon (-9 per mil PDB) and oxygen isotope values that retain seemingly systematic stratigraphic patterns with the Quaternary and Phanerozoic examples that demonstrably record meteroric water values. Similar values and patterns in the Precambrian are interpreted as primary marine in origin with significant implications for an ocean carbon mass balance not possible in the Phanerozoic carbon cycle. A similar compilation of carbonates older than one billion years do not show a relation between carbon and oxygen isotopes, lacking the negative carbon values evident in the younger record. We hypothesize that this difference records the onset of significant organic carbon on the land surface and the alteration of meteoric waters toward Phanerozoic values. We demonstrate the meteoric affinities of Neoproterozoic carbonates containing prominent negative isotope excursions recorded in the Shuram and Wonoka Formations of Oman and South Australia commonly attributed to whole ocean isotope variation. The conspicuous absence of negative carbon isotope values with normal marine oxygenisotope values in the Phanerozoic and Neoproterozic identifies a consistent relation between these time intervals and suggests that, as well accepted in the Phanerozoic, negative carbon isotope excursions less than -3 per mil are not a record of marine processes, but rather the later terrestrial biotic influence on meteoric water values.

  8. Geochronology of middle Neoproterozoic volcanic deposits in Yangtze Craton interior of South China and its implications to tectonic settings

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Here we report new SHRIMP dating results of the crystal tuff in Ejiaao Formation of middle Banxi Group in northern Guizhou. The results indicate that the volcanic deposition occurred at ~780 Ma. We also suggests that the igneous activities across Yangtze Craton with diabase dyke swarms and basal volcanic rocks during middle Banxi time are indicative of the episodic, extensive and vigorous great bimodal igneous events during middle Neoproterozoic (825-720 Ma) in South China. The characteristics of the igneous series are contrary to the model claiming they are of island-arc origin, but suggest that they are the records of rifting process and may be related to the episodic plume activities leading to the break-up of Rodinia.

  9. A Mediterranean-style model for early Neoproterozoic amalgamation of South China

    Science.gov (United States)

    Zhang, Kai-Jun

    2017-04-01

    A Mediterranean-style model is proposed for early Neoproterozoic amalgamation of South China, based on recognition of the Guangxi promontory on the southeastern margin of the Yangtze craton through a synthesis of geologic, geophysical and chronological data. The model suggests that, while the Guangxi promontory collided with the overriding Cathaysia terrane along the Yunkai orogeny during the earliest Neoproterozoic, the convergence between the Yangtze craton and the Cathaysia terrane paused or slowed down, which triggered the upper Rhine Graben-style Kangdian impact rift along the western Yangtze margin and resulted in roll-back of the oceanic slab trapped in the embayments and sequential formation of backarc rifts in the Cathaysia margin during the early Neoproterozoic. This model predicts a complex diachronous Yangtze-Cathaysia collision history, first at the Guangxi promontory at ∼1000 Ma and finally at the Guizhou reentrant at ∼830 Ma.

  10. Stretching the envelope of past surface environments: Neoproterozoic glacial lakes from Svalbard.

    Science.gov (United States)

    Bao, Huiming; Fairchild, Ian J; Wynn, Peter M; Spötl, Christoph

    2009-01-02

    The oxygen isotope composition of terrestrial sulfate is affected measurably by many Earth-surface processes. During the Neoproterozoic, severe "snowball" glaciations would have had an extreme impact on the biosphere and the atmosphere. Here, we report that sulfate extracted from carbonate lenses within a Neoproterozoic glacial diamictite suite from Svalbard, with an age of approximately 635 million years ago, falls well outside the currently known natural range of triple oxygen isotope compositions and indicates that the atmosphere had either an exceptionally high atmospheric carbon dioxide concentration or an utterly unfamiliar oxygen cycle during deposition of the diamictites.

  11. Stable Chromium Isotopes as tracer of changes in weathering processes and redox state of the ocean during Neoproterozoic glaciation

    Science.gov (United States)

    Dossing, L. N.; Gaucher, C.; Boggiani, P. C.; Frei, R.

    2010-12-01

    The chemistry of surface environments on Earth has essentially evolved from early anoxic conditions to a present day oxic state. How in detail this transition occurred is still a matter of debate but the last 200 million years (My) of the Neoproterozoic Era [(1000 to 542 million years ago (Ma)] show an emerging picture of large scale fluctuations in the redox state of the oceans [1-2]. The reasons for these fluctuations are to be sought in Earth’s atmospheric oxygenation which led to the rapid radiation of oxygen-utilizing macroscopic metazoans, but details regarding the nature of these fluctuations remain unclear. The Late Neoproterozoic is known for a number of widespread glaciations causing the return of ferruginous oceans which were absent for more than a billion years of Earth history. This study elaborates on the idea that Chromium (Cr) stable isotopes in Fe-rich chemical sediments deposited during glacial events are suitable for tracing oxygenation of surface environments through Earth's history [3]. The focus of this study is to apply the Cr isotope system to one of the Marinoan (650-630 Ma) glacio-marine sequences (Jacadigo Group, Brazil) in order to get a detailed spatial and relative temporal resolution of changes in weathering processes and redox states of the respective ocean basin during the depositional period of the sediments. The Jacadigo Group is a glacio-marine succession which is composed of the Urucum Fm. (sandstones) at the base, the Santa Cruz Fm. (BIFs) and the Puga Fm. (Fe-rich glacial diamictites) at the top. Cr stable isotope measurements on various BIF horizons of the Santa Cruz Fm. yielded positive δ53/52Cr values range from +0.4 to+ 0.9‰, while the overlying Fe-rich glaciogenic diamictites of the Puga Fm. show δ53/52Cr values range from to +0.1 to+ 0.4‰. These positively fractionated values correspond to positive δ53/52Cr values measured in other Late Neoproterozoic BIFs and speak for the occurrence of potential oxygenation

  12. Unraveling the tectonic evolution of a Neoproterozoic-Cambrian active margin in the Ribeira Orogen (Se Brazil): U-Pb and Lu-Hf provenance data

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Gabriel Lamounier de F. [Servico Geologico do Estado do Rio de Janeiro (DRM-RJ), Niteroi, RJ (Brazil); Schmitt, Renata; Bongiolo, Everton M.; Mendes, Julio [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Basei, Miguel S. [Universidade de Sao Paulo (USP), SP (Brazil)

    2015-07-01

    Full text: The Neoproterozoic-Ordovician Central Ribeira Orogen, in SE Brazil, presents two contrasting tectonic domains in its southern portion: (a) The Arc Domain constituted of Neoproterozoic to Paleozoic magmatic rocks and low P-high T metamorphic para (Sao Fidelis Group) - and ortho- derived units (in Oriental Terrane); and (b) The Basement Domain, constituted of a Paleoproterozoic and Neoproterozoic medium P-high T metamorphic para (Palmital-Buzios Succession)- and ortho-derived units (in Cabo Frio Tectonic Domain). Our work focuses on paraderived rocks sequences from both domains. The provenance analysis using U-Pb and Lu-Hf in zircon grains is presented here as an effective tool to unravel the paleogeography and nature of the pre-collisional sedimentary basins. We performed 505 analyses (U-Pb) on detrital zircon grains and some metamorphic overgrowths from six paragneiss samples. Besides, 141 analyses (Lu-Hf) in six samples only on the detrital zircon grains domains. All samples present a main peak from Neoproterozoic sources (750-570 Ma) and the other minor peak in the Stenian/Tonian periods (1200-850Ma), this indicate an orogenic contribution for this basin. Scarce register from the Mesoproterozoic and two peaks in the Archean/Paleoproterozoic (2.6 and 1.9 Ga) are recognized as a contribution from an ancient continent. The Lu-Hf data reveals a juvenile source for the detrital zircon grains from Buzios Succession while Palmital and Sao Fidelis Group units show a main crustal signature for their detrital zircon population. Based on the U-Pb and Lu-Hf data presented here, plus petrological data, geological correlations, and compilation of data from literature, we propose a tectonic model for the origin of para-derived rocks from the eastern part of the Ribeira Orogen. Starting with an extensional environment of ca. 600 Ma in a back-arc basin (Buzios succession deposition) and continuing as an active margin between 570 and 550 Ma in the fore-arc and prism

  13. Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications.

    Science.gov (United States)

    Kaufman, A J; Knoll, A H

    1995-01-01

    The recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vectorial signals provided by fossils and Sr-isotopic variations, C isotope chemostratigraphy facilitates the interbasinal correlation of later Neoproterozoic successions. Results of these studies are evaluated in terms of four stratigraphic intervals: (1) the Precambrian/Cambrian boundary, (2) the post-Varanger terminal Proterozoic, (3) the late Cryogenian, and (4) the early Cryogenian. Where biostratigraphic or radiometric data constrain the age of Neoproterozoic sedimentary sequences, secular variations in C and Sr isotopes can provide a level of stratigraphic resolution exceeding that provided by fossils alone. Isotopic data place strong constraints on the chemical evolution of seawater, linking it to major tectonic and paleoclimatic events. They also provide a biogeochemical framework for the understanding of the initial radiation of macroscopic metazoans, which is associated stratigraphically, and perhaps causally, with a global increase in the burial of organic C and a concomitant rise of atmospheric O2.

  14. Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications

    Science.gov (United States)

    Kaufman, A. J.; Knoll, A. H.

    1995-01-01

    The recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vectorial signals provided by fossils and Sr-isotopic variations, C isotope chemostratigraphy facilitates the interbasinal correlation of later Neoproterozoic successions. Results of these studies are evaluated in terms of four stratigraphic intervals: (1) the Precambrian/Cambrian boundary, (2) the post-Varanger terminal Proterozoic, (3) the late Cryogenian, and (4) the early Cryogenian. Where biostratigraphic or radiometric data constrain the age of Neoproterozoic sedimentary sequences, secular variations in C and Sr isotopes can provide a level of stratigraphic resolution exceeding that provided by fossils alone. Isotopic data place strong constraints on the chemical evolution of seawater, linking it to major tectonic and paleoclimatic events. They also provide a biogeochemical framework for the understanding of the initial radiation of macroscopic metazoans, which is associated stratigraphically, and perhaps causally, with a global increase in the burial of organic C and a concomitant rise of atmospheric O2.

  15. Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

    DEFF Research Database (Denmark)

    Kirsch, Moritz; Svenningsen, Olaf

    2016-01-01

    Mafic magmatic rocks formed between ca. 615 and 560 Ma along the Neoproterozoic margins of Baltica and Laurentia are classically attributed to continental rifting heralding the opening of the Iapetus Ocean. We report new data for the Kebnekaise Intrusive Complex (KIC) exposed in the Seve Nappes i...

  16. Remelting of Neoproterozoic relict volcanic arcs in the Middle Jurassic: Implication for the formation of the Dexing porphyry copper deposit, Southeastern China

    Science.gov (United States)

    Liu, Xuan; Fan, Hong-Rui; Santosh, M.; Hu, Fang-Fang; Yang, Kui-Feng; Li, Qiu-Li; Yang, Yue-Heng; Liu, Yongsheng

    2012-10-01

    The Dexing copper deposit in southeastern China is a typical non-arc porphyry deposit, the origin of which has been a topic of debate for several decades. Here we present new results from U-Pb geochronology, whole-rock chemistry and Sr-Nd-Hf-O isotopic investigations on the ore-forming granodioritic porphyry. LA-ICPMS zircon U-Pb data suggest that the granodioritic porphyry was formed in the Middle Jurassic (ca. 172.5 Ma) probably associated with lithospheric thinning driven by either sub-continental lithospheric mantle delamination or asthenospheric upwelling. The porphyry displays both arc-like and adakitic trace element signatures. The adakitic features suggest that HREE (heavy rare earth elements)-rich minerals such as garnet and hornblende, in the absence of plagioclase resided in the source region. The arc-like signatures are broadly comparable with those of the proximal Neoproterozoic island arc rocks including the keratophyre from Shuangxiwu Group and associated granitoids indicating a potential genetic relationship. The porphyry has chondritic ɛNd(t) of - 0.28 to 0.25 and radiogenic ɛHf(t) of 2 to 7, and correspondingly, uniform two stage depleted mantle Nd model ages of 940-980 Ma and Hf model ages of 800-1100 Ma (mean ~ 920 Ma). On Nd and Hf isotopic evolution diagrams, these values are markedly similar to those of the adjacent Neoproterozoic arc rocks when calculated forward to the Mid-Jurassic. Zircons of the porphyry show mantle-like oxygen isotope characters with δ18O values clustering in the range of 4.7-5.9‰, similar to the values for the Neoproterozoic arc rocks mentioned above. The geochemical and isotopic features recorded in our study suggest mantle-derived magmas with no significant supracrustal input for the source of the porphyry. With regard to the source of the Cu ore, we consider a model involving the remelting of sulfide-bearing arc-related lower crustal source. Furthermore, the occurrence of a Neoproterozoic VMS (volcanic massive

  17. Chemostratigraphy and lithological characters of Neoproterozoic cap carbonates from the Kuruktag Mountain, Xinjiang, western China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Neoproterozoic Era includes some of the most largest ice ages in the geological history.The exact number of glaciations is unknown,though there were at least two events of global glaciation.Neoproterozoic glacial deposits in the Kurukmg Mountain,Xinjiang,western China have proven that there had occurred three discrete Neoproterozoic glaciations.Diamictite units occurred in the Bassi,Tereeken,and Hankalchough formations,carbonate units were recognized among the diamictites and immediately overlied the Bayisi,Tereeken and Hankalchough diamictites.Carbonates at the top of the Bayisi Formation are characterized by the dolo-sility stones with negative δ13C values ranging from-4.10‰ to-8.17‰(PDB),comparable to the Sturtian cap carbonates that overlie the Sturtian glacial deposits from other Neoproterozoic sequences.Carbonates overlying the Tereeken Formation are characterized by the pinkish cap dolostones fca.10 m thick)with negative δ13C values railging from -2.58‰ to-4.77‰(PDB),comparable to the Marinoan cap carbonates,The cap is alao characterized by tepee-like structures,barite precipitates and pseudomorphous aragonite crystal fan limestones.Carbonates at the top of the Hankalchough Formation are characterized by subaerial exposure crust(vadose pisolite structure,calcareous crust structure)dolostones with negative δ13C values ranging from-4.56‰δto-11.45‰(PDB)and the calcareous crust dolostones,implying that the Hankalchough cap carbonates differ from either the Sturtian or Marinoan cap carbonates in sedimentary environment and carbon isotopic composition.In addition,it is suggested the Hankalchough glaciation belongs to a terrestrial glaciation and it is the third largest glaciation during the Neoproterozoic period on the Tarim platform.

  18. Documenting and describing the redox evolution of the Neoproterozoic ocean: lessons from the Canadian Cordillera (Invited)

    Science.gov (United States)

    Johnston, D. T.; Poulton, S. W.; Langmuir, C. H.; MacDonald, F. A.; Chen, Z.; Knoll, A.

    2009-12-01

    The geological record of the Neoproterozoic preserves evidence for large-scale perturbations in Earth’s climate and changes in tectonic configuration. During the terminal Proterozoic, and within the context of these changes, Earth’s fluid envelope achieved a level of oxygenation that allowed for the evolution and subsequent radiation of complex multi-cellular life. As such, better constraining the geochemical evolution of the oceans and atmosphere throughout the entire Neoproterozoic will allow for a more mechanistic understanding of the links between changing environmental chemistry and biological innovation. Further, it will provide information on the relative timing of these changes and, where robust dates are available, estimates on the absolute rates of change (both chemical and biological). To this end, our ongoing work has focused on constructing high stratigraphic resolution geochemical records through mixed lithological packages of sedimentary rocks from eastern Alaska and the Canadian Cordillera. Here, we present detailed chemostratigraphic reconstructions of redox sensitive proxies, including Fe-speciation and trace element budgets, that provide an integrated window into Neoproterozoic marine oxidant budgets. These oxidant budgets then allow for the modeling of the relative influence of different aerobic and anaerobic microbial processes on the overall carbon cycle. Taken together, it is this cascade of microbial processes that drives remineralization reactions, the sum of which serves to counter-act organic carbon export, which is ultimately responsible for the buildup of O2. This simple framework serves as the foundation for our interpretation of Neoproterozoic biogeochemistry and informs our view of late Precambrian marine ecosystems. This approach can be further applied to more specific, and perhaps even more anomalous intervals of Neoproterozoic Earth history, including the Cryogenian Bitter Springs event and the Ediacaran Shuram anomaly; both

  19. The Neoproterozoic Drift History of Laurentia: a Critical Evaluation and new Palaeomagnetic Data from Northern and Eastern Greenland

    DEFF Research Database (Denmark)

    Christiansen, Jørgen Løye

    2008-01-01

    Laurentia occupies a critical position in palaeogeographic models for the Neoproterozoic, forming the core of Rodinia Supercontinent. The breakup of Rodinia in the late Neoproterozic was marked by the dispersal of its various constituent continental fragments, concomitant with major episodes...... margin at a latitude of ~17° at this time. Collectively these data agree with models that have Laurentia moving into high latitudes in the latest Neoproterozoic. The required plate velocities, although high, are in the range for Phanerozoic continents. --------------------------------------------------------------------------------...

  20. Geology of East Egypt greenstone field in Neoproterozoic isoand arc: Reconstruction of Iron formation sedimentary environment.

    Science.gov (United States)

    Kiyokawa, S.; Suzuki, T.

    2015-12-01

    Geology of East Egypt greenstone-granit belt which is northern part of Nubia shield was identified neoproterozoic island arc amalgamated sections. There are several iron formation within these greenstone belt. Age data shows this iron formation may be overlaped during 700 Ma Snowball period, how ever, there is no detail report of well preserved ice related evidences. We now started detail field work for identified tectonic reconstruction, original stratigraphy around Iron formation and sedimentary environment during the iron formation sedimentation area. East Egyptian shield was divided three geology, Proterozoic greenstone complex, 700-600 Granitic domes and cover sequence (Hammamet Group). We focus three area to identified sedimentary environment of iron sedimentation. Along the north-south trend of Wadi EL Dabban area are, we named Wadi branch as West site is RW-0 ~ 12, East site is RE-0 ~ 12 from north to south. Northern area is structurally moderate, southern portion is north dipping. Southern portion was intruded by granite and several place contain granitic dikes. Northeast to eastern area are identified younger sedimentary sequence (Hammamat Group) which is unconformablly overlay on the other iron formation bearing greenstone belt. Structurally these area is divided four units. Wadi was divided by right-lateral strike-ship fault. The displacement are more than 3 km. Also north dipping faults are identified.East-West trend fault are divided two units. It is divided NE, SE, NW and NS units.SW unit is most well preserved thick sequence of the Iron formation. SW unit is well preserved iron formation sequence within thick volcaniclastics. This unit mostly north dipping around 40-60 degree. Structural repetition in not well understand. Reconstract stratigraphy in this unit is at least 4000m in thickness. 5 member is identified in this sequence. Several thin iron formations are observed with in pillow lava and volcaniclastic sequence. These very thick

  1. Geochemistry and petrogenesis of Neoproterozoic Mylliem granitoids, Meghalaya Plateau, northeastern India

    Indian Academy of Sciences (India)

    Jyotisankar Ray; Abhishek Saha; Sohini Ganguly; V Balaram; A Keshav Krishna; Sampa Hazra

    2011-06-01

    The Mylliem granitoids of the Meghalaya Plateau, northeastern India, represent one of the disharmonic Neoproterozoic igneous plutons, which are intrusive into low-grade Shillong Group of metasediments. Field studies indicate that the Mylliem granitoids cover an area of about 40 km2 and is characterized by development of variable attitude of primary foliations mostly marked along the margin of the pluton. Xenoliths of both Shillong Group of metasediments and mafic rocks have been found to occur within Mylliem granitoids. Structural study of the primary foliation is suggestive of funnel-shaped intrusion of Mylliem granitoids with no appreciable evidence of shearing. Petrographically, Mylliem granitoids are characterized by pink to white phenocrysts of prismatic microcline/perthite and lath-shaped plagioclase (An20–An29). Groundmass material is characterized by quartz, microcline, plagioclase, muscovite and biotite. Sphene and apatite occur as accessory minerals. Petrographically Mylliem granitoids have been discriminated as granite and granodiorite according to IUGS system of classification. Critical evaluation of geochemical data and variation trends of major oxides/trace elements suggests a significant role of fractional crystallization in the evolution of Mylliem pluton. Th/U ratios (3.22–6.77) indicate a relatively higher abundance of Th over U. Chondrite-normalized REE diagram characteristically shows an enriched LREE pattern and prominent negative Eu anomaly (Eu/Eu* = 0.16–0.42) indicating the significant role of plagioclase fractionation from the parent magma. An overall strong REE fractionation pattern has been envisaged for Mylliem granitoids. The strong REE fractionation of the Mylliem granitoids is depicted by (Ce/Yb) values, which show a range of 1.39 to 1.65. The aluminium saturation index (ASI) (ranging from 1.0 to 1.3), A/CNK ratios (ranging from 1.4 to 2.11) and A/NK ratios (ranging from 1.75 to 2.43) provide evidences for the peraluminous, S

  2. Discussion on the Neoproterozoic glaciations in the South China Block and their related paleolatitudes

    Institute of Scientific and Technical Information of China (English)

    ZHANG QiRui; CHU XueLei; FENG LianJun

    2009-01-01

    The Kaigas, Sturtian, Marinoan, and Gaskiers glaciations are widely recognized in Neoproterozoic. However, in the South China Block only the Jiangkou (Sturtian) and Nantuo (Marinoan) are symbolized by sedimentary records. The Kaigas, recorded by isotopic and chemical proxies, exhibited likely the nature of cold paleoclimate with local mountain glaciation. The correlation of the Doushantuo Forma-tion with the Gaskiers is indicated by the carbon isotope excursion and the dated age from the interval, however the South China Block was then under non-glacial weather. With no paleomagnetic data, the position of the South China Block during the Sturtian glaciation cannot be determined. The paleolati-tudes of the South China Block during the Kaigas and Nantuo glaciations are intermediate, even though the Nantuo was once rendered erratically deduced equatorial. In fact, the paleolatitudes of the South China Block during the Neoproterozoic glaciations are all likely at about 30°-40°.

  3. Seafloor-precipitated carbonate fans in the Neoproterozoic Rainstorm Member, Johnnie Formation, Death Valley Region, USA

    OpenAIRE

    Pruss, Sara Brady; Corsetti, Frank A.; Fischer, Woodward W.

    2008-01-01

    Cm-sized carbonate seafloor fans occur in the Neoproterozoic Rainstorm Member of the Johnnie Formation, Death Valley, USA. The fans formed in a mixed carbonate-clastic succession near storm wave base at the base of parasequences on a storm-dominated ramp. Petrographic observations indicate that the fans were originally precipitated as aragonite and later inverted to calcite during diagenesis. Although not directly dated, the Rainstorm Member preserves a large magnitude negative carbon isotopi...

  4. Methane seeps, methane hydrate destabilization, and the late Neoproterozoic postglacial cap carbonates

    Institute of Scientific and Technical Information of China (English)

    JIANG Ganqing; SHI Xiaoying; ZHANG Shihong

    2006-01-01

    Methane hydrates constitute the largest pool of readily exchangeable carbon at the Earth's sedimentary carapace and may destabilize, in some cases catastrophically, during times of global-scale warming and/or sea level changes. Given the extreme cold during Neoproterozoic ice ages, the aftermath of such events is perhaps amongst the most likely intervals in Earth history to witness a methane hydrate destabilization event. The coincidence of localized but widespread methane seep-like structures and textures, methane-derived isotopic signal,low sulfate concentration, marine barites, and a prominent, short-lived carbon isotope excursion (δ13C≤-5‰) from the post-Marinoan cap carbonates (~635 Ma) provides strong evidence for a methane hydrate destabilization event during the late Neoproterozoic postglacial warming and transgression. Methane release from hydrates could cause a positive feedback to global warming and oxidation of methane could result in ocean anoxia and fluctuation of atmospheric oxygen, providing an environmental force for the early animal evolution in the latest Neoproterozoic. The issues that remain to be clarified for this event include the trigger of methane hydrate destabilization, the time of initial methane release, the predicted ocean anoxia event and its relationship with the biological innovation, additional geochemical signals in response to methane release, and the regional and global synchrony of cap carbonate precipitation. The Doushantuo cap carbonate in South China provides one of the best examples of its age for a better understanding of these issues.

  5. Micro-analysis by U-Pb method using LAM-ICPMS and its applications for the evolution of sedimentary basins: the example from Brasilia Belt; Micro-analise pelo metodo U-Pb usando LAM-CIPMS e suas aplicacoes para a evolucao de bacias sedimentares: o exemplo da faixa Brasilia

    Energy Technology Data Exchange (ETDEWEB)

    Pimentel, Marcio Martins; Matteini, Massimo; Junges, Sergio Luiz; Giustina, Maria Emilia Schutesky Della; Dantas, Elton Luiz; Buhn, Bernhard, E-mail: marcio@unb.br [Universidade de Brasilia (UnB), DF (Brazil). Instituto de Geociencias; Rodrigues, Joseneusa Brilhante [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil)

    2015-07-01

    The U-Pb geochronological method using LAM-MC-ICPMS represents an important tool to investigate the geological evolution of sedimentary basins, as well as its geochronology, through the determination of upper limits for the depositional ages of detrital sedimentary rocks. The method has been applied in the Geochronology Laboratory of the Universidade de Brasilia, and in this study, a brief review of the provenance data for the sediments of the Neoproterozoic Brasilia Belt is presented and their significance for the evolution of the orogen is discussed. The results indicate that the Paranoa and Canastra Groups represent passive margin sequences formed along the western margin of the Sao Francisco-Congo continent. The Vazante Group presents similar provenance patterns, although Sm-Nd isotopic results suggest that its upper portions had contributions from younger (Neoproterozoic) sources, possibly from the Neoproterozoic Goias Magmatic Arc. On the other hand, metasediments of the Araxa and Ibia groups contain an important proportion of material derived from Neoproterozoic sources, demonstrating that they represent syn-orogenic basins. The provenance pattern of the Bambui Group is marked by an important Neoproterozoic component, showing that it constitutes a sedimentary sequence which is younger than 600 Ma, representing a foreland basin to the Brasilia Belt. (author)

  6. Siberian Origins of Neoproterozoic to Upper Triassic Rocks of Arctic Alaska

    Science.gov (United States)

    Clough, J. G.; Blodgett, R. B.

    2007-12-01

    found in the Canadian Arctic Islands Richly diverse Upper Triassic fauna (halobiid and monotid bivalves, brachiopods) are present in the both the Shublik Formation and Otuk Group. These show closer affinities with NE Siberia rather than to western or northern North America, suggesting close spatial relationships between Siberia and Arctic Alaska at least until Late Triassic time. Sedimentary provenance studies in eastern Brooks Range Precambrian rocks indicate age ranges that are dissimilar to Proterozoic detrital-zircon ages from clastic rocks of the northern Canadian Cordillera and Canadian Arctic Islands where a detrital source within the Grenville orogen is indicated. Paleocurrent directions for the Neoproterozoic Katakturuk Dolomite in the northeast Brooks Range and similar-age units in the adjacent Victoria Island and Amundsen Basin are in approximately 100 degree opposition for a counterclockwise rotational- restored Arctic Alaska. Upper Devonian clastics of northern Alaska are in 180 degree opposition to coeval units in the Canadian Arctic Islands when the Arctic Alaska plate is restored in the rotational model. Therefore, based on paleobiogeography, sediment provenance, stratigraphy and sedimentology, tectonic models for the opening of the Canada Basin must take into account that Triassic and older rocks in Arctic Alaska have Siberian origins or were deposited proximal to Siberia.

  7. Pressure-temperature evolution of Neoproterozoic metamorphism in the Welayati Formation (Kabul Block), Afghanistan

    Science.gov (United States)

    Collett, Stephen; Faryad, Shah Wali

    2015-11-01

    The Welayati Formation, consisting of alternating layers of mica-schist and quartzite with lenses of amphibolite, unconformably overlies the Neoarchean Sherdarwaza Formation of the Kabul Block that underwent Paleoproterozoic granulite-facies and Neoproterozoic amphibolite-facies metamorphic events. To analyze metamorphic history of the Welayati Formation and its relations to the underlying Sherdarwaza Formation, petrographic study and pressure-temperature (P-T) pseudosection modeling were applied to staurolite- and kyanite-bearing mica-schists, which crop out to the south of Kabul City. Prograde metamorphism, identified by inclusion trails and chemical zonation in garnet from the micaschists indicates that the rocks underwent burial from around 6.2 kbar at 525 °C to maximum pressure conditions of around 9.5 kbar at temperatures of around 650 °C. Decompression from peak pressures under isothermal or moderate heating conditions are indicated by formation of biotite and plagioclase porphyroblasts which cross-cut and overgrow the dominant foliation. The lack of sillimanite and/or andalusite suggests that cooling and further decompression occurred in the kyanite stability field. The results of this study indicate a single amphibolite-facies metamorphism that based on P-T conditions and age dating correlates well with the Neoproterozoic metamorphism in the underlying Sherdarwaza Formation. The rocks lack any paragenetic evidence for a preceding granulite-facies overprint or subsequent Paleozoic metamorphism. Owing to the position of the Kabul Block, within the India-Eurasia collision zone, partial replacement of the amphibolite-facies minerals in the micaschist could, in addition to retrogression of the Neoproterozoic metamorphism, relate to deformation associated with the Alpine orogeny.

  8. Ocean redox structure across the Late Neoproterozoic Oxygenation Event: A nitrogen isotope perspective

    Science.gov (United States)

    Ader, Magali; Sansjofre, Pierre; Halverson, Galen P.; Busigny, Vincent; Trindade, Ricardo I. F.; Kunzmann, Marcus; Nogueira, Afonso C. R.

    2014-06-01

    The end of the Neoproterozoic Era (1000 to 541 Ma) is widely believed to have seen the transition from a dominantly anoxic to an oxygenated deep ocean. This purported redox transition appears to be closely linked temporally with metazoan radiation and extraordinary perturbations to the global carbon cycle. However, the geochemical record of this transition is not straightforward, and individual data sets have been variably interpreted to indicate full oxygenation by the early Ediacaran Period (635 to 541 Ma) and deep ocean anoxia persevering as late as the early Cambrian. Because any change in marine redox structure would have profoundly impacted nitrogen nutrient cycling in the global ocean, the N isotope signature of sedimentary rocks (δ15Nsed) should reflect the Neoproterozoic deep-ocean redox transition. We present new N isotope data from Amazonia, northwest Canada, northeast Svalbard, and South China that span the Cryogenian glaciations (˜750 to 580 Ma). These and previously published data reveal a N-isotope distribution that closely resembles modern marine sediments, with a mode in δ15N close to +4‰ and range from -4 to +11‰. No apparent change is seen between the Cryogenian and Ediacarian. Data from earlier Proterozoic samples show a similar distribution, but shifted slightly towards more negative δ15N values and with a wider range. The most parsimonious explanation for the similarity of these N-isotope distribution is that as in the modern ocean, nitrate (and hence O2) was stable in most of the middle-late Neoproterozoic ocean, and possibly much of Proterozoic Eon. However, nitrate would likely have been depleted in partially restricted basins and oxygen minimum zones (OMZs), which may have been more widespread than in the modern ocean.

  9. The clumped isotopic record of Neoproterozoic carbonates, Sultanate of Oman

    Science.gov (United States)

    Bergmann, K. D.; Eiler, J. M.; Fischer, W. W.; Osburn, M. R.; Grotzinger, J. P.

    2011-12-01

    The Huqf Supergroup of the Sultanate of Oman records several important events in latest Precambrian time, including two glaciations in the Abu Mahara Group (ca. 725 - isotope excursion in the Nafun Group (ca. isotopic excursions, hypothesized to record perturbations of the surficial Earth carbon cycle or post-depositional diagenetic processes. Rigorous interpretation of these records requires a more thorough assessment of diagenetic processes. To better understand the significance and cause of these large amplitude isotopic excursions, we employed carbonate clumped isotope thermometry. This method allows us to estimate the absolute temperature of carbonate precipitation, including recrystallization, based on the temperature dependent abundance of carbonate ions containing both 13C and 18O. These estimates are accompanied by a measurement of carbonate δ18O, which in conjunction with temperature, can be used to calculate the oxygen isotopic composition of the fluid from which the carbonate precipitated. We analyzed stratigraphically constrained samples from a range of paleoenvironments with differing burial histories (1 - >10km maximum burial depth) to constrain the temperature and fluid composition of recrystallization. Clumped isotope temperatures from Huqf Supergroup samples range from 35-175°C. The isotopic composition of the fluid these rocks equilibrated with ranges from -3.7 to 15.7% VSMOW. This large range in temperature and fluid composition separates into distinct populations that differ systematically with independent constraints on petrography, stratigraphy and burial history. The data indicate the Abu Mahara, Nafun and Ara groups have unique diagenetic histories. In central Oman, the post-glacial Abu Mahara cap dolostone shows high temperature, rock buffered diagenesis (Tavg = 176°C; δ18Ofluid = 15% VSMOW), the Nafun Group generally experienced lower temperature, fluid buffered diagenesis (Tavg = 69°C; δ18Ofluid = 1% VSMOW) and the Ara Group

  10. Co-evolution of Eukaryotes and Ocean and Atmosphere Oxygenation in the Neoproterozoic and Paleozoic Eras

    Science.gov (United States)

    Lenton, T. M.; Daines, S. J.; Mills, B.; Boyle, R. A.

    2014-12-01

    The nature, timing and cause(s) of the Earth's second oxygenation event are widely debated. It has been argued that there was a single pronounced rise in atmospheric oxygen toward present levels in the Late Neoproterozoic, which in turn triggered the evolution of animals. Here we suggest a more complex co-evolutionary scenario, with fluctuations in ocean and atmosphere oxygenation in the Late Neoproterozoic and Early Paleozoic caused partly by the evolution of animals, followed by a pronounced rise of atmospheric oxygen to present levels later in the Paleozoic caused by the rise of land plants. Current geochemical evidence suggests some parts of the deep oceans became oxygenated during the Ediacaran, but there was subsequent de-oxygenation of the ocean during the Cambrian that may have persisted into the Ordovician. Only later in the Paleozoic is there evidence for widespread oxygenation of the deep ocean, together with charcoal indicating atmospheric oxygen had approached present levels. The limited Neoproterozoic oxygenation of the ocean could be explained by the evolution of filter-feeding sponges removing oxygen demand from the water column and encouraging a shift from cyanobacteria to faster-sinking eukaryotic algae, which transferred oxygen demand to greater depths and into sediments. The resulting oxygenation of shelf bottom waters would have increased phosphorus removal from the ocean thus lowering global productivity and oxygen demand in a positive feedback loop encouraging ocean oxygenation [1]. The subsequent Cambrian de-oxygenation of the ocean could be explained by the evolution of bioturbating animals oxygenating the sediments and thus lowering the C/P burial ratio of organic matter, reducing organic carbon burial and lowering atmospheric oxygen [2]. The later rise of land plants, selectively weathering phosphorus from continental rocks and producing recalcitrant high C/P biomass, increased organic carbon burial and atmospheric oxygen, finally

  11. A global transition to ferruginous conditions in the early Neoproterozoic oceans

    Science.gov (United States)

    Guilbaud, Romain; Poulton, Simon W.; Butterfield, Nicholas J.; Zhu, Maoyan; Shields-Zhou, Graham A.

    2015-06-01

    Eukaryotic life expanded during the Proterozoic eon, 2.5 to 0.542 billion years ago, against a background of fluctuating ocean chemistry. After about 1.8 billion years ago, the global ocean is thought to have been characterized by oxygenated surface waters, with anoxic and sulphidic waters in middle depths along productive continental margins and anoxic and iron-containing (ferruginous) deeper waters. The spatial extent of sulphidic waters probably varied through time, but this surface-to-deep redox structure is suggested to have persisted until the first Neoproterozoic glaciation about 717 million years ago. Here we report an analysis of ocean redox conditions throughout the Proterozoic using new and existing iron speciation and sulphur isotope data from multiple cores and outcrops. We find a global transition from sulphidic to ferruginous mid-depth waters in the earliest Neoproterozoic, coincident with the amalgamation of the supercontinent Rodinia at low latitudes. We suggest that ferruginous conditions were initiated by an increase in the oceanic influx of highly reactive iron relative to sulphate, driven by a change in weathering regime and the uptake of sulphate by extensive continental evaporites on Rodinia. We propose that this transition essentially detoxified ocean margin settings, allowing for expanded opportunities for eukaryote diversification following a prolonged evolutionary stasis before one billion years ago.

  12. C-isotope composition and correlation of the Upper Neoproterozoic in Keping area, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    HE XiuBin; XU Bei; YUAN ZhiYun

    2007-01-01

    C-isotope analysis of the carbonates in the Upper Neoproterozoic in Keping, Xinjiang indicates that the Qigebrak Formation and the Upper Sugaitbrak Formation mainly record positive C-isotope values, and a distinct positive excursion occurs in the lower part of the Qigebrak Formation. There are three negative excursions in the boundary between the Qigebrak Formation and the Cambrian, the uppermost and lowermost Upper Sugaitbrak Formation. These characters resemble those of the Upper Neoproterozoic in the Three-Gorge area, which suggests that the Upper Sugaitbrak Formation and Qigebrak Formation can be correlated with the middle and upper parts of the Doushantuo Formation and Dengying Formation, respectively. The negative excursion at the top of the Upper Sugaitbrak Formation corresponds to that at the top of the Doushantuo Formation, while the negative excursion at the bottom of the Sugaitbrak Formation can be correlated with that at the middle part of the Doushantuo Formation in the Three-Gorge area and that at the top of the Hangelchaok diamictites in the Quruqtagh area.

  13. The 1.0 Ga S-type granite in the East Kunlun Orogen, Northern Tibetan Plateau: Implications for the Meso- to Neoproterozoic tectonic evolution

    Science.gov (United States)

    He, Dengfeng; Dong, Yunpeng; Zhang, Feifei; Yang, Zhao; Sun, Shengsi; Cheng, Bin; Zhou, Bo; Liu, Xiaoming

    2016-11-01

    The East Kunlun Orogen (EKO) is characterized by widely distributed granitoids with different ages, which are keys to understanding the tectonic evolution of the Central China Orogenic Belt. Zircon U-Pb ages and Hf isotopic compositions, as well as the whole rock geochemistry of the gneissic granite from the basement rock, are carried out to elucidate the Meso- to Neoproterozoic tectonics of the EKO. The Al-rich minerals, including muscovite and tourmaline, and the A/CNK ratios (1.07-1.18) indicate S-type affinity of the granite. The granite displays high SiO2 and K2O contents, and slightly enrichment in LREE in chondrite normalized REE distribution pattern with strong negative Eu anomalies (δEu = 0.10-0.15). The samples exhibit positive anomalies of Rb, Th, U and Pb, and depletion of Ba, Nb, Ta, Sr and Ti. Meanwhile, the high Rb/Ba and Rb/Sr ratios and low (CaO + FeO + MgO + TiO2) contents indicate that they were derived from pelitic material. Together with the negative εHf(t) values ranging from -5.97 to -2.34 and two-stage Hf model ages varying from 1968 to 1786 Ma, the gneissic granite is suggested being originally derived from partial melting of the metasedimentary rocks of the Paleoproterozoic Jinshuikou Group in the central EKO due to the crust thickening. Most zircon grains from the gneissic granite show typical magmatic zircon morphology, and yield an U-Pb upper intercept age of 1006 ± 20 Ma (MSWD = 1.5), representing the crystallization age. Integrated with the regional geology, our results suggest that the EKO has been probably involved into a Meso- to Neoproterozoic plate collisional event related to the assembly of the Rodinia supercontinent.

  14. Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian tectonic evolution☆

    Science.gov (United States)

    Fritz, H.; Abdelsalam, M.; Ali, K.A.; Bingen, B.; Collins, A.S.; Fowler, A.R.; Ghebreab, W.; Hauzenberger, C.A.; Johnson, P.R.; Kusky, T.M.; Macey, P.; Muhongo, S.; Stern, R.J.; Viola, G.

    2013-01-01

    The East African Orogen, extending from southern Israel, Sinai and Jordan in the north to Mozambique and Madagascar in the south, is the world́s largest Neoproterozoic to Cambrian orogenic complex. It comprises a collage of individual oceanic domains and continental fragments between the Archean Sahara–Congo–Kalahari Cratons in the west and Neoproterozoic India in the east. Orogen consolidation was achieved during distinct phases of orogeny between ∼850 and 550 Ma. The northern part of the orogen, the Arabian–Nubian Shield, is predominantly juvenile Neoproterozoic crust that formed in and adjacent to the Mozambique Ocean. The ocean closed during a protracted period of island-arc and microcontinent accretion between ∼850 and 620 Ma. To the south of the Arabian Nubian Shield, the Eastern Granulite–Cabo Delgado Nappe Complex of southern Kenya, Tanzania and Mozambique was an extended crust that formed adjacent to theMozambique Ocean and experienced a ∼650–620 Ma granulite-facies metamorphism. Completion of the nappe assembly around 620 Ma is defined as the East African Orogeny and was related to closure of the Mozambique Ocean. Oceans persisted after 620 Ma between East Antarctica, India, southern parts of the Congo–Tanzania–Bangweulu Cratons and the Zimbabwe–Kalahari Craton. They closed during the ∼600–500 Ma Kuungan or Malagasy Orogeny, a tectonothermal event that affected large portions of southern Tanzania, Zambia, Malawi, Mozambique, Madagascar and Antarctica. The East African and Kuungan Orogenies were followed by phases of post-orogenic extension. Early ∼600–550 Ma extension is recorded in the Arabian–Nubian Shield and the Eastern Granulite–Cabo Delgado Nappe Complex. Later ∼550–480 Ma extension affected Mozambique and southern Madagascar. Both extension phases, although diachronous,are interpreted as the result of lithospheric delamination. Along the strike of the East African Orogen, different geodynamic settings

  15. Multiple rifting and alkaline magmatism in southern India during Paleoproterozoic and Neoproterozoic

    Science.gov (United States)

    Renjith, M. L.; Santosh, M.; Satyanarayanan, M.; Rao, D. V. Subba; Tang, Li

    2016-06-01

    The Southern Granulite Terrane (SGT) in India preserves the history of tectonothermal events ranging from Paleoarchean to latest Neoproterozoic-Cambrian. Here we investigate alkaline magmatism possibly associated with rifting events in Paleoproterozoic and Neoproterozoic based on petrological, geochemical and zircon U-Pb and Lu-Hf isotopic studies on the alkaline complexes of Korangani (KGAC) and Kambamettu (KAC) in the Madurai Block of SGT. The mica pyroxenite which represents the first intrusive phase at KGAC crystallized from a mildly alkaline hydrous magma derived from a metasomatized mantle. The younger shoshonitic syenite was emplaced at 2533 ± 16 Ma, carries mafic microgranular enclaves, and shows trace-elements ratios consistent with magma mixing trend, and zircon εHf(t) values display mixed positive and negative values - 2.6 to 3.6 suggesting the mixing of adakite-like felsic crustal melt and non-adakitic mantle derived melt. In KAC, four distinct magmatic intrusions are identified: i) quartz-monzonite (emplaced at 2498 ± 16 Ma), an ultrapotassic adakitic rock derived from a carbonated alkali-rich lower crustal source with negative zircons εHf(t) values in zircon (- 8.0 to - 0.8); Y/Nb (> 1.2) and Th/Ce (0.03-0.8) ratios; lower Ni (< 30 ppm) and Cr (< 14 ppm) contents; ii) phlogopite-rich pyroxenite, crystallized from an alkali-rich basaltic parental magma derived from carbonate metasomatized mantle; iii) mantle derived high Ba-Sr carbonatite (emplaced at 2470 ± 15 Ma); and iv) shoshonitic peralkaline syenite rock (emplaced at 608 ± 6 Ma) with strong adakitic signature, low MgO (< 1 wt.%), Ni (12-5 ppm) and Cr (49-35 ppm) contents and negative zircon εHf(t) values (- 30.3 to - 27.3) and trough of Zr-Hf in spidergrams suggesting a carbonated alkali-rich garnet-bearing crustal source. The geochemical features and petrogenetic considerations of the felsic shoshonitic-ultrapotassic adakite-like rocks (syenite, quartz monzonite), mica-pyroxenites and

  16. Late-Neoproterozoic hydrothermal fluid activity in the Tandilia belt, Argentina

    Directory of Open Access Journals (Sweden)

    Juan C Martínez

    2013-09-01

    Full Text Available In the Barker - Villa Cacique area, Tandilia belt, alteration mineral assemblages were studied by petrography, XRD and EMPA at three different stratigraphic levels: (1 a phyllic alteration at the unconformity palaeoproterozoic basement-neoproterozoic sedimentary succession (TLPU; (2 an advanced argillic alteration in the Las Águilas Formation (middle level; and (3 a phyllic alteration on pyroclastic rocks of the Olavarría Formation (upper level. Special emphasize was placed on the chemical characterization of K-white micas and chlorites. Secondary K-white micas of altered migmatites, from the Las Aguilas and Olavarría Formations have a low paragonite content (Na* 9.5 km for the entire sedimentary pile. Hot fluids would rise from deep-seated realms, metamorphic and/or hidden igneous sources. A correlation with a Brasiliano thermo-tectonic event is hypothesized.

  17. Mid amphibolite facies metamorphism of harzburgites in the Neoproterozoic Cerro Mantiqueiras Ophiolite, southernmost Brazil

    Directory of Open Access Journals (Sweden)

    HARTMANN LÉO A.

    2003-01-01

    Full Text Available Valuable information is retrieved from the integrated investigation of the field relationships, microstructure and mineral compositions of harzburgites from the Neoproterozoic Cerro Mantiqueiras Ophiolite. This important tectonic marker of the geological evolution of southernmost Brazilian Shield was thoroughly serpentinized during progressive metamorphism, because the oldest mineral assemblage is: olivine + orthopyroxene + tremolite + chlorite + chromite. This M1 was stabilized in mid amphibolite facies - 550-600ºC as calculated from mineral equilibria. No microstructural (e.g. ductile deformation of olivine or chromite or compositional (e.g. mantle spinel remnant of mantle history was identified. A metamorphic event M2 occurred in the low amphibolite facies along 100 m-wide shear zones, followed by intense serpentinization (M3 and narrow 1-3 m-wide shear zones (M4 containing asbestos.

  18. Integrated in situ U-Pb Age and Hf-O Analyses of Zircon from the Northern Yangtze Block: New Insights into the Neoproterozoic Low-δ18O Magmas in the South China Block

    Science.gov (United States)

    Yang, Y. N.; Wang, X. C.; Li, Q. L.; Li, X. H.

    2015-12-01

    The oxygen isotopic composition of Neoproterozoic magmas from the northern Yangtze Block holds a key for the origin of large-scale 18O depletion in the HP and UHP metamorphic rocks in the Dabie-Sulu orogenic belt, northern margin of the South China Block. We report here the integrated in situ U-Pb dating and O-Hf isotope analyses of zircon grains from sedimentary and volcanic rocks of the late Neoproterozoic Suixian Group (SG) from the northern Yangtze Block. Detrital zircon grains display age peaks of 0.73-0.74 Ga, 0.79 Ga, and 2.0 Ga. Zircon U-Pb ages together with Hf-O isotopic composition indicate provenance of SG dominantly from proximal Neoproterozoic igneous rock and likely hidden Paleoproterozoic basement along the northern margin of the Yangtze Block. The zircon δ18O values from SG range from 10.5‰ to 1.3‰. Zircon grains with negative δ18O value, typical result of magma-ice interaction, were not identified in this study. The major phase of low-δ18O (< 4‰) magmas initiated at ca. 780 Ma, long before the first glaciation event (< 715 Ma) in the South China Block. Thus caution should be taken when using low-δ18O zircon grains to infer cold climate. Low-δ18O zircon grains have large ranges of ɛHf(t) values, varying from -15.5 to 10.7, concentrating on negative ɛHf(t). This strongly argues against the possibility that the low-δ18O magma was produced by partial melting of high-temperature hydrothermally altered oceanic crust because this model predicted MORB-like Hf isotopes for the resultant low-δ18O magmas. This study emphasizes that high-T water-rock interaction and continental rifting tectonic setting are essential to generate abundant low-δ18O magmas. The important application of our study is to confirm that most of negative-δ18O zircons identified in HP and UHP metamorphic rocks may not have been inherited from their Neoproterozoic protoliths.

  19. The late Neoproterozoic to early Cambrian sulphur cycle: an isotopic investigation of sedimentary rocks from the Yangtze platform

    Science.gov (United States)

    Goldberg, T.; Strauss, H.

    2003-04-01

    The sulphur cycle responds to changes in seawater chemistry, biological evolution and tectonic activity. We follow an isotopic approach in order to constrain the state of the ocean/atmosphere system during the late Neoproterozoic and early Cambrian. For this purpose, sedimentary successions from the Yangtze platform, South China, were analysed for their sulphur isotopic composition in different S-bearing phases. The general stratigraphy comprises in ascending order the Doushantuo, Dengying and Niutitang formations. Main lithologies include carbonates, phosphorites, black shales and cherts. The sulphur isotopic composition of the late Neoproterozoic to early Cambrian seawater sulphate ranges from +30 to +35 ‰ as evident from calcium sulphates and trace sulphate in unaltered carbonates and phosphorites (Shields et al., 1999). Sulphur isotopes in chromium reducible and organically bound sulphur are displaced by about +40 ‰ from the seawater sulphate signal, indicating bacterial sulphate reduction. Isotope values range between -16 and +25 ‰ reflecting different environmental conditions, varying from open to closed/limiting conditions in respect to sulphate availability. Pyrite morphology is studied in order to characterize the diagenetic environment. Consistent with a biological origin for the sedimentary pyrite in the Neoproterozoic as well as in the Cambrian (Strauss, 2002) is the positive correlation between sulphide sulphur and organic carbon abundances. The availability of reactive iron is evaluated by means of the degree of pyritization (Raiswell et al., 1988). Raiswell, R. Buckley, F., Berner, R. &Anderson, T. (1988) Degree of pyritization of iron as a paleoenvironmental indicator of bottom-water oxygenation. Journal of Sedimentary Petrology, 58, No.5, 812-819 Shields, G., Strauss, H., Howe, S. &Siegmund, H. (1999) Sulphur isotope composition of sedimentary phosphorites from the basal Cambrian of China: implications for Neoproterozoic-Cambrian biochemical

  20. Cryptic signatures of Neoproterozoic accretionary events in northeast Brazil imaged by magnetotellurics: Implications for the assembly of West Gondwana

    Science.gov (United States)

    Padilha, Antonio L.; Vitorello, Icaro; Pádua, Marcelo B.; Fuck, Reinhardt A.

    2017-03-01

    The Borborema Province, in northeast Brazil, is a complex orogenic system severely affected by deformational, metamorphic, and magmatic processes mostly during the Gondwana convergence in late Neoproterozoic-early Phanerozoic Brasiliano/Pan-African Orogeny. New magnetotelluric (MT) data collected along the northwestern part of the province and eastern part of the contiguous Parnaíba Basin are combined with previous MT data to assess the regional deep electrical resistivity structure. Dimensionality analysis shows that a 3D electrical structure predominates in the subsurface and thus 3D inversion was carried out. The final geoelectric model allows delineating the geometry and variation in physical properties of different lithospheric blocks bounded by major electrical discontinuities. These lithospheric blocks constitute a coalesced mosaic made up of four main terrane compartments: a resistive cratonic keel detected along the western part of the study area, currently hidden beneath the Parnaíba Basin (Parnaíba block); two complex domains in the center characterized by several resistive and conductive zones throughout the crust and upper mantle (Ceará Central and Rio Grande do Norte domains); and a conductive block in the east, with the geoelectric response being controlled by possible remains of late Neoproterozoic subduction activity to the south (Central sub-province). The interfaces between these blocks are interpreted as suture zones correlated to their Neoproterozoic collage, one curved conductor concealed by the sediments of the Parnaíba Basin and bordering the eastern margin of the basin, another huge conductor corresponding to the location of the Orós-Jaguaribe subdomain on the surface, and a third interface coinciding with the position of the Patos shear zone. The presence of these proposed sutures could be a conspicuous evidence of a Neoproterozoic accretion system in northeast Brazil and would support tectonic evolution models for the West Gondwana

  1. Possible Record of Neoproterozoic Ice Sheet Collapse: The Kapp Lyell Diamictite Sequence of southwest Spitsbergen, Svalbard

    Science.gov (United States)

    Bjornerud, M.

    2008-12-01

    The Late Proterozoic Kapp Lyell diamictites of northern Wedel Jarlsberg Land, southwest Spitsbergen, have long been recognized as ancient glacial deposits, but their place within the global stratigraphic framework of 'Snowball Earth' has remained unclear owing to the complexity of superimposed Caledonian deformation and to the inaccessible terrain in which they occur. Newly deglaciated exposures of the rocks now provide a more complete picture of the changing environment in which they were deposited and their place in the global chronostratigraphy. The Kapp Lyell Sequence (KLS) is the higher of two diamictic to conglomeratic Neoproterozoic units in SW Spitsbergen. The lower of these, the Konglomeratfjellet Formation, is not unambiguously glaciogenic, but it is topped by a carbonate sequence with textures similar to 'cap' carbonate units in other Neoproterozoic sequences. These carbonates are succeeded by ca. 2000 m of black phyllite with rare lone stones. The phyllite is overlain with apparent conformity by the 2000-3000 m thick KLS, which actually consists of three distinct types of diamictite, all apparently glaciomarine. The KLS begins with 500- 1000 m of finely laminated diamictite punctuated by pebble- to boulder-sized lone stones, presumably ice- rafted. The cm-scale laminae are defined by layers of sand-to-silt sized particles of detrital dolomite alternating with thin films of graphitic phyllite. Preliminary delta 13C values from this graphitic material are very negative, pointing to a biogenic origin. The extraordinary uniformity of the laminae indicates repetitive, possibly seasonal, depositional cycles, but the density of lone stones increases upsection, recording accelerating delivery of ice-rafted debris to the basin. Carbonate clasts predominate, and many have distinctive textures (cm-sized ooids, digitate stromatolites) that link them with the 'cap' carbonate unit lower in the section. The laminated diamictite interval ends abruptly with the

  2. Neoproterozoic-Paleozoic Evolution of the Arctida Paleocontinent and Plate Reconstructions

    Science.gov (United States)

    Vernikovsky, V. A.; Metelkin, D. V.; Vernikovskaya, A. E.; Matushkin, N. Y.; Lobkovsky, L. I.; Shipilov, E. V.; Scientific Team of Arctida

    2011-12-01

    Available data on the existence of Precambrian metamorphic complexes among the main structures of the Arctic led to the suggestion that a large continental mass existed between Laurentia, Baltica and Siberia - an Arctic continent, more often called Arctida (Zonenshain, Natapov, 1987). It is inferred that as an independent continental mass Arctida was formed after the breakup of Rodinia, and in general it can have a pre-Grenvillian (including Grenvillian) basement age. The breakup of this mass and the collision of its fragments with adjacent cratons led to the formation of heterochronous collisional systems. Arctida probably included the Kara, Novosibirsk, Alaska-Chukotka blocks, the blocks of northern Alaska and the submerged Lomonosov Ridge, small fragments of the Inuit fold belt in the north of Greenland and the Canadian archipelago, the structures of the Svalbard and maybe the Timan-Pechora plates. However the inner structure of this paleocontinent, the mutual configuration of the blocks and its evolution in the Neoproterozoic-Paleozoic is still a matter of discussion. The most accurate way of solving these issues is by using paleomagnetic data, but those are nonexistent for most of the defined blocks. Reliable paleomagnetic determinations for the Neoproterozoic-Paleozoic time interval we are concerned with are available only for fragments of an island arc from Central Taimyr, which are 960 m.y. old (Vernikovsky et al., 2011) and for which the paleomagnetic pole is very close to the pole of Siberia from (Pavlov et al., 2002), and of the Kara microcontinent. This includes three paleomagnetic poles for 500, 450 and 420 Ma (Metelkin et al., 2000; Metelkin et al., 2005). It is those data that made up the basis of the presented paleotectonic reconstructions along with an extensive paleomagnetic database for the cratons of Laurentia, Baltica, Siberia and Gondwana. The paleogeographic position of the cratons is corrected (within the confidence levels for the

  3. The Neoproterozoic-Paleozoic Arctic Margins: early stages of geodynamic evolution and plate reconstructions

    Science.gov (United States)

    Vernikovsky, V. A.; Metelkin, D. V.; Vernikovskaya, A. E.; Matushkin, N. Yu.; Lobkovsky, L. I.; Shipilov, E. V.

    2012-04-01

    Available data on the existence of Precambrian metamorphic complexes among the main structures of the Arctic led to the suggestion that a large continental mass existed between Laurentia, Baltica and Siberia - an Arctic continent, more often called Arctida (Zonenshain, Natapov, 1987). It is inferred that as an independent continental mass Arctida was formed after the breakup of Rodinia, and in general it can have a pre-Grenvillian (including Grenvillian) basement age. The breakup of this mass and the collision of its fragments with adjacent cratons led to the formation of heterochronous collisional systems. Arctida probably included the Kara, Novosibirsk, Alaska-Chukotka blocks, the blocks of northern Alaska and the submerged Lomonosov Ridge, small fragments of the Inuit fold belt in the north of Greenland and the Canadian archipelago, the structures of the Svalbard and maybe the Timan-Pechora plates. However the inner structure of this paleocontinent, the mutual configuration of the blocks and its evolution in the Neoproterozoic-Paleozoic is still a matter of discussion. The most accurate way of solving these issues is by using paleomagnetic data, but those are nonexistent for most of the defined blocks. Reliable paleomagnetic determinations for the Neoproterozoic-Paleozoic time interval we are concerned with are available only for fragments of an island arc from Central Taimyr, which are 960 m.y. old (Vernikovsky et al., 2011) and for which the paleomagnetic pole is very close to the pole of Siberia from (Pavlov et al., 2002), and of the Kara microcontinent. This includes three paleomagnetic poles for 500, 450 and 420 Ma (Metelkin et al., 2000; Metelkin et al., 2005). It is those data that made up the basis of the presented paleotectonic reconstructions along with an extensive paleomagnetic database for the cratons of Laurentia, Baltica, Siberia and Gondwana. The paleogeographic position of the cratons is corrected (within the confidence levels for the

  4. The Jormungand Global Climate State and Implications for the Neoproterozoic Snowball Paradox (Invited)

    Science.gov (United States)

    Abbot, D. S.; Voigt, A.; Koll, D.; Pierrehumbert, R. T.

    2010-12-01

    We present a previously undescribed global climate state, the Jormungand state, that is nearly ice-covered with a narrow (~10-15 degrees of latitude) strip of open ocean near the equator. This state is sustained by internal dynamics of the hydrological cycle and the cryosphere. There is a new bifurcation in global climate climate associated with the Jormungand state that leads to significant hysteresis. We investigate the Jormungand state in a coupled ocean-atmosphere GCM, in multiple atmospheric GCMs coupled to a mixed layer ocean run in an idealized configuration, and we make a simple modification to the Budyko-Sellers model so that it produces Jormungand states. We suggest that the Jormungand state may be a better model for the Neoproterozoic glaciations (~635 Ma and ~715 Ma) than either the hard Snowball or the Slushball models. A Jormungand state would have a large enough region of open ocean near the equator to explain the micropaleontological and molecular clock evidence that photosynthetic eukaryotes thrived both before and immediately after the Neoproterozoic episodes. Additionally, since there is significant hysteresis associated with the Jormungand state, it can explain the cap carbonate sequences, the oxygen isotopic evidence that suggests high CO2 values, and the various evidence that suggests lifetimes for the glaciations of 1 Myrs or more. Since there is not significant hysteresis associated with the Slushball model, the Slushball model cannot explain these observations. Finally, we note that although the Slushball and Jormungand models share the characteristic of open ocean in the tropics, the Jormungand state is produced by entirely different physics, is entered through a new bifurcation in global climate, and is associated with significant hysteresis. Bifurcation diagram of global climate in the CAM global climate model, run with no continents, a 50 m mixed layer with no ocean heat transport, an eccentricity of zero, and annually and diurnally

  5. Chemostratigraphy of stable chromium isotopes in cap carbonate sequences - tracing the aftermath of Earth's Neoproterozoic icehouse climates

    Science.gov (United States)

    Frei, R.; de Andrade Caxito, F.; Gaucher, C.

    2012-12-01

    The Neoproterozoic Era (1000-542 Ma) was a time of extreme climatic variation as recorded in sedimentary rocks of this age across the globe. Of special interest are often occurring associations of glacial deposits with warm climate carbonate platforms, features which are preferentially explained to have resulted from extreme icehouse-greenhouse fluctuations unprecedented in the Phanerozoic record. Despite local differences in the sedimentation regime (clastic, mixed or carbonate), these events are represented by glacial deposits of diverse nature, overlain by distinctive "cap carbonate" sequences. The chemostratigraphy (particularly of δ13C and 87Sr/86Sr signatures) of carbonate sequences has been invoked as a promising alternative tool for regional and global correlation., and these signatures provide proxies for seawater composition at the time of deposition, and may indirectly signalize climatic fluctuations on land. We studied a cap carbonate profile pertaining to the Bambuí Group (Sete Lagoas Formation; Correntina section; previously studied by Caxito et al., 2012)) in the north central part of the São Franciso basin in Brazil. This section lies atop Archean to Paleoproterozoic gneisses of the São Francisco craton basement. The section begins with two-metre thick massive to finely laminated pink dolostone which grade upward into a reddish to purple limestone rhythmite. δ53Cr values of the cap dolostone are within the range typical of magmatic inventory signatures (δ53Cr = 0.1 +/- 0.1 permil; Schoenberg et al., 2008). Our preliminary few first data from the sequence above the cap dolostones show magmatic values also for samples from within the first 20 metres of laminated limestones, which then tend to increase to δ53Cr values of ~+0.3 permil in the following ca. 100 metres of carbonates. Although our data set at this stage is sparse, we note a trend that δ53Cr values correlate with fluctuations of δ13C and δ18O values (Caxito et al., 2012). These

  6. Provenance of the Neoproterozoic high-grade metasedimentary rocks of the arc-related Oriental Terrane of the Ribeira belt: Implications for Gondwana amalgamation

    Science.gov (United States)

    Lobato, Marcela; Heilbron, Monica; Torós, Bernardo; Ragatky, Diana; Dantas, Elton

    2015-11-01

    The Costeiro domain integrates the Oriental terrane of the Ribeira belt, which encompasses arc-related orthogneisses of the Rio Negro complex (ca.790-605 Ma), with a well-documented subduction signature, and the high-grade metasedimentary rocks of the São Fidélis group. The arc-related rocks intruded the lower unit of the São Fidélis group, while both units are crosscut by syn-to late collision granitoids related to the development of different stages of the Brasiliano Orogeny (ca. 605-480 Ma). New U-Pb (LA-ICP-MS) data of detrital zircon grains from quartzites of the top unit of the São Fidélis group yielded a large spectrum of Mesoproterozoic and Paleoproterozoic ages, with subordinated Archean and Neoproterozoic ones. The largest age peaks occur at ca. 1.2 Ga and 2.2 Ga. The youngest detrital zircon of ca. 613 Ma, and metamorphic overprints, with ages varying from ca. 602 to 570 Ma bracket the age of sedimentation of the top unit. Two orthogneisses of the Rio Negro complex intruded within the basal unit of the São Fidélis Group rendered similar ages of ca.620 Ma. These orthogneisses and the basal unit of the São Fidélis group are interpreted as possible sources of the upper unit. The provenance pattern of the São Fidélis Group is similar to that of the Kaoko Belt, suggesting that the Angolan basement, where Mesoproterozoic ages are common, constitutes another important source area.

  7. Microorganisms Linked to Neoproterozoic Microspar Carbonate Sedimentation in the Jilin-Liaoning Area

    Institute of Scientific and Technical Information of China (English)

    GE Ming; KUANG Hongwei; MENG Xianghua; George FURNISS

    2004-01-01

    Molar-tooth carbonate refers to a sort of rock that has ptygmatical folded structure comparable to the ivory. This kind of carbonate exists in a special time range (from Middle to Neoproterozoic). Its origin and the possibility to use it in stratigraphic correlation of the paleocontinent is the key task of the IGCP447, a project on Proterozoic molar tooth carbonates and the evolution of the earth (2001-2005). The importance lies in that the molar-tooth structure is the key to solving problems related to Precambrian biological and global geochemical events. The molar-tooth structure is associated with microorganisms.Development and recession of such carbonates have relations with the evolution process of early lives and abrupt changes in sea carbonate geochemistry. In recent years, based on researches on petrology,geochemistry and Sr isotope of molar-tooth carbonate in the Jilin-Liaoning and Xuzhou-Huaiyang area, the authors hold that it can be used as a marker for stratigraphic sequence and sedimentary facies analyses.

  8. Finding of Neoproterozoic low-18O igneous rocks in the northern margin of the Dabie orogen

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yongfei; WU Yuanbao; ZHAO Zifu; GONG Bing

    2004-01-01

    @@ It has been one of the most intriguing questions in the earth sciences whether the snowball Earth event is genetically associated with mantle superwelling, supercontinent assemblage and breakup, and rift magmatism during the Neoproterozoic[1-4]. In order to demonstrate the occurrence of significant interaction in energy and matter between the earth's interior and exterior in this period, it is critical to find coeval igneous rocks that contain the signature of surface water and thus form low-18O magma.Several investigations of U-Pb dating and O isotope analysis were carried out for zircons from ultrahigh pressure (UHP) metamorphic rocks in the Dabie-Sulu orogen,east-central China[5-8]. The results indicate that low δ18O zircons have U-Pb ages of 700-800 Ma as dated by either TIMS discordia upper-intercept or SIMS in-situ magmatic core, and the origin of low δ18O water is related to cold paleoclimate during the Sturtian ice age.

  9. Neoproterozoic paleogeography of the Tarim Block: An extended or alternative "missing-link" model for Rodinia?

    Science.gov (United States)

    Wen, Bin; Evans, David A. D.; Li, Yong-Xiang

    2017-01-01

    Recent reconstructions of the Rodinia supercontinent and its breakup incorporate South China as a ;missing link; between Australia and Laurentia, and place the Tarim craton adjacent to northwestern Australia on the supercontinent's periphery. However, subsequent kinematic evolution toward Gondwana amalgamation requires complex geometric shuffling between South China and Tarim, which cannot be easily resolved with the stratigraphic records of those blocks. Here we present new paleomagnetic data from early Ediacaran strata of northwest Tarim, and document large-scale rotation at near-constant paleolatitudes during Cryogenian time. The rotation is coeval with Rodinia breakup, and Tarim's paleolatitudes are compatible with its placement between Australia and Laurentia, either by itself as an alternative ;missing link; or joined with South China in that role. At the same time, indications of subduction-related magmatism in Tarim's Neoproterozoic record suggest that Rodinia breakup was dynamically linked to subduction retreat along its northern margin. Such a model is akin to early stages of Jurassic fragmentation within southern Gondwana, and implies more complicated subduction-related dynamics of supercontinent breakup than superplume impingement alone.

  10. Sulfur and carbon isotopic variations in Neoproterozoic sedimentary rocks from southern China

    Institute of Scientific and Technical Information of China (English)

    CHU Xuelei; ZHANG Qirui; ZHANG Tonggang; FENG Lianjun

    2003-01-01

    A new set of δ34Ssulfide, δ34Ssulfate and δ13Ccarbonate values has been reported from Neoproterozoic sedimentary rocks in southern China. The interglacial black shales of the Datangpo Fm. display higher δ34Ssulfide values with >+20‰ average, but the postglacial black shales from the Doushantuo Fm. show negative δ34Ssulfide values. However, the Jinjiadong Fm., the same post-glaciation as the Doushantuo Fm., has positive δ34Ssulfide values, implying that the δ34S value of sedimentary sulfides would be controlled by lithofacies and paleogeographic environments. The δ34Ssulfate values relative to δ13Ccarbonate were obtained by extraction of trace sulfate from the successive carbonate sequences in the Yangtze Gorges sections. A preliminary interpretation suggests that the oceanic environment may fluctuate dramatically at the post-glacial Doushantuo stage and, then, recover its stability at the Dengying stage on the basis of the high resolution δ34S and δ13C curves of seawater.

  11. THE NEOPROTEROZOIC ISLAND-ARC ASSOCIATION OF THE MUKODEK GOLD-ORE FIELD, NORTHERN BAIKAL AREA

    Directory of Open Access Journals (Sweden)

    V. A. Vanin

    2015-09-01

    Full Text Available Metamorphosed volcanic rocks of the Ushmukan suite were studied in the Mukodek gold-ore field located in the Baikal-Muya belt in the Northern Baikal area, Russia. The Ushmukan suite shows interleaving of ortoschists which compositions are widely variable. Basalt-andesite-dacite series of normal alkalinity are the substrate of the studied metavolcanic rocks. Based on the set of geochemical characteristics, it is concluded that the rocks were formed in suprasubduction geodynamic conditions corresponding to a mature island arc. The proximity of the geological locations and the similarity of the geochemical characteristics of the volcanic rocks of the Ushmukan suite and rocks of the Kelyan suite (Neoproterozoic, 823 Ma, which have similar compositions, give grounds to consider these two rock suites as age peers. Specific features of gold distribution through the Mukodek gold-ore field are analyzed. Industrial gold contents are recorded only in berezite-listvenite metasomatic rocks of the gold-quartz-sulfide formation which were formed on metavolcanic rocks of the Ushmukan suite. It is concluded that the volcanic rocks, which are specific of the island-arc setting, could be a source of gold for deposits in the Mukodek gold-ore field. 

  12. Paleoclimatological change in the Late Neoproterozoic: Evidence from oxygen isotopes of phosphorite in Yangtze Platform, China

    Science.gov (United States)

    Ling, H.-F.; Jiang, S.-Y.; Feng, H.-Z.; Chen, J.-H.; Chen, Y.-Q.; Yang, J.-H.

    2003-04-01

    Seawater and its isotopic composition is the most promising recorder for the climate change of the Earth. Chemical sediments such as carbonate and phosphorite has long been used to reveal the seawater chemistry in the past. The d13C of carbonate with least diagenesis has proved to be sensitive proxy for paleo-environment and paleo-productivity and for chemostratigrphy (e.g. Shen, 2002; Yang et al., 1999; Lambert et al., 1987). However, d18O of carbonate are more prone to suffering diagenesis, and therefore the implications of Phanerozoic d18O curve are controversial (cf. Veizer et al., 1999). Recent study of Wenzel et al. (2000) shows that Silurian phosphatic conodont retained primary oxygen isotopes whereas the d18O values of the coeval calcitic brachiopod shells were altered by diagenesis. Here, we presented and compared oxygen, carbon isotopic compositions and trace and rare earth element concentrations of Neoproterozoic phosphorite and coeval dolomite from the Yangtze platform in an attempt to reconstruct the paleoclimatological and paleooceanographic change during Neoproterozoic. The Yangtze platform possesses excellent record of Late Neoproterozoic-Cambrian strata. In this study, we collected samples systematically from late Neoproterozoic Doushantuo Formation at the Wengan section, Guizhou province. The Doushantuo Fm, overlying on the late Vendian tillite of Nantuo Fm and overlain by dolostone of Dengying Fm which underlain the basal Cambrian black shale, consists mainly of phosphorite and minor interbeded dolostone with total thickness of about 70 m. Our results show large variations of d18Odolo(SMOW) for the dolomite (17.6 ~ 25.9‰) which has no correlation with their d13Cdolo values and other geochemical parameters. In contrast, phosphorites display rather limited variations of the d18Ophos (SMOW) values (10.7 ~ 15.0‰). Further more, the d18Ophos and d13Cdolo values, Ce anomaly and Pb/Th ratio consistently increased from the lower to upper part of the

  13. Gammaspectrometry identification covering Neoproterozoic supracrustal sequences in the Serido Belt , northeastern Brazil; Identificacao gamaespectrometrica de placeres rutilo-monaziticos neoproterozoicos no sul da Faixa Serido, nordeste do Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Sebastiao Milton P. da, E-mail: smpsilva@cchla.ufrn.br, E-mail: sebastiaomilton@gmail.com [Laboratorio de Geoprocessamento, Departamento de Geografia, Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Crosta, Alvaro P., E-mail: alvaro@ige.unicamp.br [Instituto de Geociencias, Universidade Estadual de Campinas (Unicamp), SP (Brazil); Ferreira, Francisco J.F., E-mail: francisco.ferreira@ufpr.br [Laboratorio de Pesquisas em Geofisica Aplicada- LPGA, Departamento de Geologia, Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil); Beurlen, Hartmut, E-mail: beurlen@terra.com.br [Programa de Pos-Graduacao em Geociencias, Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Silva, Adalene M., E-mail: adalene@unb.br [Laboratorio de Geofisica Aplicada, Instituto de Geociencias da Universidade de Brasilia (UnB), DF (Brazil); Silva, Marcelo R.R. da, E-mail: marcelor@ufpe.br [Departamento de Geologia, Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil)

    2010-01-15

    Aerial gamma-ray survey data covering Neoproterozoic supracrustal sequences in the Serido Belt were processed and analyzed together with ground gamma-ray data, air photos and geological data for lithogeophysical characterization and mapping of granitic rocks, related pegmatites fields and lithological units of Serido Group. Interpretation was based on individual and ternary images of the three radio-elements and the eU/eTh and eTh/K ratios, and allowed the discovery of thorium anomalies associated with coarse-grained metarenites and metaconglomerates facies intercalated with quartzites of the Equador Formation. High contents of iron oxides, ilmenite, monazite, rutile, titanite and zircon were identified by ore microscopy of polished sections in the metaconglomerate's matrix. Semiquantitative scanning electron microscopy (SEM) analyses in minerals of two samples revealed up to 79.4% of Th0{sub 2} and 87.7% of REE in monazites; up to 99.2% of Ti0{sub 2} in ilmenite and rutile and up to 1.81 % of HfO{sub 2} in zircon. Gamma-ray anomalies due to thorium were also identified in association with sediments of Cenozoic age in the region. (author)

  14. A Cambrian Arc Built on the Neoproterozoic Rifted Margin of Gondwana

    Science.gov (United States)

    Musgrave, R. J.

    2009-12-01

    Cambrian convergence along the northeastern side of the Curnamona Craton, the Gondwana margin in southeastern Australia, resulted in the development of the Delamerian Orogen. A Neoproterozoic rifted margin, marked by the alkalic Mount Arrowsmith Volcanics, forms the substrate on which is built a NE-facing Cambrian arc, complete with a clearly delineated inner imbricate accretionary prism (the Wonnaminta Zone) and outer thin-skinned wedge (the Kayrunnera Zone). Arc volcanism, represented by the calc-alkaline Mount Wright Volcanics, exhibits mixed arc-rift geochemistry. Interpretation and modelling of magnetic data reveals a chain of volcanic edifices of the Mount Wright Arc, now below 3 to 7 km of Devonian sandstones in the Bancannia Trough. Remarkably, a simple rotation around an Euler pole reconstructs the Wonnaminta Zone against the craton, and aligns structural elements on the two sides of the trough. Arc volcanism evidently occupied a rift in marginal continental crust, and the geometry, geochemistry and geophysical properties of the Mount Wright Arc are closely analogous to the Taupo Zone of New Zealand. Rifting of the arc divided Delamerian structures, indicating that at least part of the Delamerian deformation developed in a subduction accretion setting, rather than in some terminal collision. Below the Wonnaminta Zone a 3 to 5 km thick body can be traced as a large magnetic source along the length of the zone. Overridden by the thrust stack of the accretionary prism, this body is mostly planar and dips towards the east, although it is deformed into a broad antiform in the central part of the zone. Physical properties suggest that this body may be a thick rift-volcanic pile equivalent to the Mount Arrowsmith Volcanics. In the southern part of the belt a re-entrant in the Wonnaminta Zone faces a large magnetic anomaly sourced in the basement of the Kayrunnera Zone. The geometry of the re-entrant, and the development of Silurian and Devonian basins over the

  15. Ediacaran stromatolites and intertidal phosphorite of the Salitre Formation, Brazil: Phosphogenesis during the Neoproterozoic Oxygenation Event

    Science.gov (United States)

    Caird, R. A.; Pufahl, P. K.; Hiatt, E. E.; Abram, M. B.; Rocha, A. J. D.; Kyser, T. K.

    2017-04-01

    of hydrothermal veins range from - 4.7‰ to - 3.0‰ (mean = - 4.2‰) reflecting equilibration with temperatures > 80 °C. δ13C values are between - 7.0‰ and + 5.6‰ (mean = - 1.8‰,). Late lateritic weathering produced calcretes with δ18O values between - 3.3‰ and - 1.3‰, and δ13C values from - 9.2‰ to - 8.0‰ (mean values are - 1.8‰ and - 8.7‰, respectively). Petrographic analysis, generally low δ18O, and high δ13C values suggest hydrothermal dolomitization and remobilization of P led to secondary phosphate mineralization of intertidal stromatolite biostromes to produce economic phosphorite. Collectively, these results suggest that the benthic P-cycle in the Neoproterozoic was more complex than previously surmised and emphasize the multifaceted significance of microbial, paleoenvironmental, and diagenetic processes that allowed phosphorite to accumulate on the São Franciscan craton. Such information further elucidates attributes of the onset of Earth's second major phosphogenic episode, which is roughly coincident with the Neoproterozoic Oxygenation Event (NOE) and the evolution of multicellular animals.

  16. Generation of continental crust in the northern part of the Borborema Province, northeastern Brazil, from Archaean to Neoproterozoic

    Science.gov (United States)

    de Souza, Zorano Sérgio; Kalsbeek, Feiko; Deng, Xiao-Dong; Frei, Robert; Kokfelt, Thomas Find; Dantas, Elton Luiz; Li, Jian-Wei; Pimentel, Márcio Martins; Galindo, Antonio Carlos

    2016-07-01

    (TZ). Early Neoproterozoic volcanism at 1091 Ma, and A-type plutonism, from 920 to 775 Ma, mark the intracontinental magmatism in the TZ. In the Seridó Domain, the Late Neoproterozoic registers several events of plutonism, at 600-593, 575-560, 548-533, 528-510, 495-450 Ma. These rocks cover ca. 15% of the area, while Neoproterozoic supracrustal rocks cover ca. 30%. The most important magmatic event is that at 575 Ma, consistent with the peak of widespread transpression and synchronous high temperature metamorphism. The Neoproterozoic rocks are mostly K-enriched alkaline or transitional to calc-alkaline. Inherited Archaean and Palaeoproterozoic zircons and Nd model ages, as well as moderate to strongly negative (-21 to -9) epsilon Nd, and persistent negative anomalies for Ta-Nb, Ti and P indicate significant crustal contributions in their genesis. While a convergent setting (subduction zone) could explain the Archaean and Palaeoproterozoic units, this is not so for the Neoproterozoic rocks which mimic the geochemical and isotopic features of the older sources. In the study area, the peak of juvenile accretion (mantle derived magmas) took place in the Archaean (3.4-2.7 Ga) and Palaeproterozoic (2.4-2.11 Ga), whereas crustal recycling predominated in the Neoproterozoic.

  17. Geochronology and sources of late Neoproterozoic to Cambrian granites of the Saldania Belt

    Science.gov (United States)

    Chemale, F.; Scheepers, R.; Gresse, P. G.; van Schmus, W. R.

    2011-04-01

    The Saldania Belt (SB), located in the southernmost part of South Africa, contains S-, I-, and A-type granites. Whole-rock Sm-Nd data for the Saldania granites indicate the presence of a juvenile as well as inherited crustal signature. The earlier S-type granites have ɛNd( t) values from -4.2 to -3.28 (for t = 550 Ma). In contrast, the intermediate I-type and youngest A-type and highly fractionated I-type granites display ɛNd values ranging from -1.44 to -3.68 (for t = 540 Ma) and from +3.66 to +5.1(for t = 530 Ma), respectively. The U-Pb single zircon data of A-type granites exposed in the Western Branch of the SB yielded dates from 524 ± 8 to 510 ± 4 Ma, whereas an S-type granite, situated in the Southern Branch of the SB and represented by the syn- to late-tectonic Rooiklip Granite, yielded an age of 527 ± 8 Ma. The volcano-sedimentary rocks intruded by these granites display Nd model ages from Ga to 1.67 Ga and ɛNd( t) values from -6.58 to +3.34 (for t = 560 Ma) with isotope signature similar to those of the granites. The S- and I-type granitic magmatism is mostly a product of melting of an earlier crust (Mesoproterozoic to Paleoproterozoic) with different degree of juvenile contribution. The obtained isotope data and field relationship support the hypothesis that the lithological units of the SB were affected by the late Neoproterozoic to Early Cambrian tectonism, related to compressive deformational processes at the southern margin of the Kalahari Plate and probably correlated with the Sierra La Ventana Belt basement.

  18. Molecular composition and indigenity of organic matter in Late Neoproterozoic sedimentary rocks from the Yangtze region, South China

    Institute of Scientific and Technical Information of China (English)

    LI Meijun; WANG Tieguan; WANG Chunjiang; ZHANG Weibiao

    2006-01-01

    Diamictites from Late Neoproterozoic Nantuo tillites (~600 Ma), and dolomites from the overlying Dousantuo and Dengying formations in the Yangtze region, southern China, were analyzed for solvent extractable hydrocarbons. Even though all these samples have low contents of TOC and have undergone overmature thermal evolution, there has been still preserved quite a large amount of hydrocarbons. Analysis of the extracts by gas chromatography-mass spectrometry (GC-MS) revealed the presence of n-alkanes, regular acyclic isoprenoids, tricyclic terpanes, hopanes, gammacerane, steranes, and polyaromatic hydrocarbons. Strict experimental measurements were performed in the analytical procedure to prevent any potential contaminants from being introduced. All these bitumens have molecular markers of Precambrian characteristics and no external organics derived from current contamination events or migrated hydrocarbons from younger strata. The maturity parameters for bitumens indicate that the hydrocarbons are of over-maturity, which is consistent with the thermal maturity of the host rocks. Consequently, it is concluded that the Late Neoproterozoic bitumens in the Yangtze region, South China, are indigenous to their host rocks, which provides the basis for our organic geochemical research on "Snowball Earth" and "Cambrian Explosion."

  19. Late Neoproterozoic to early Cambrian sulphur cycle-An isotopic investigation of sedimentary rocks from the Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    Tatiana GOLDBERG; Harald STRAUSS; GUO Qingjun; LIU Congqiang

    2003-01-01

    The sulphur cycle responds to changes in seawater chemistry, biological evolution and tectonic activity. We follow an isotopic approach in order to constrain the state of the ocean/atmosphere system during late Neoproterozoic and early Cambrian. For this purpose, a sedimentary succession deposited on the Yangtze Platform, South China, was analysed for its sulphur isotopic composition in different S-bearing phases. Redox changes were defined by the degree of pyritization (DOP) values in order to show variations in the oxygenation of the depositional environment. The sulphur isotopic composition of late Neoproterozoic to early Cambrian seawater sulphate ranges from +30‰ to +35‰ as evident from trace sulphate in unaltered carbonates and phosphorites. The isotopic composition for pyrite and organic sulphur varies between -16‰ and +23‰. The apparent sulphur isotopic fractionation between seawater sulphate and pyrite as well as organically bound sulphur varies between 7‰ and 50‰. This large fractionation, as well as its variability suggests a biological origin for pyrite and organically bound sulphur. The temporal evolution of different geochemical proxy signals is comparable for different successions across the Yangtze Platform.

  20. Tidal shelf sedimentation in the Neoproterozoic Chattisgarh succession of central India

    Indian Academy of Sciences (India)

    Sarbani Patranabis Deb

    2005-06-01

    The Neoproterozoic Kansapathar Sandstone of the Chattisgarh basin, a shallow marine shelf bar sequence, consists of mineralogically and texturally mature sandstones with subordinate siltstones, mudstones and conglomerates. The sediments were transported, reworked and deposited in subtidal environments by strong tidal currents of macrotidal regime as well as storms, and accumulated as discrete shoaling-upward features, separated from each other by muddy to low-energy sandy deposits. The sandbodies developed into shoaling up linear bars, often more than a kilometre in length, through accretion of thick cross-stratified units in transverse directions under the influence of ebb and flood tidal currents, as well as in longitudinal direction affected by southeasterly flowing along-shore currents. The aggrading upper surfaces of the bars experienced protracted reworking by strong oscillatory wave currents leading to extensive development of subaqueous 2D or 3D dunes mantled with lag pebble deposits at different points. With continued shoaling and progradation, thebars amalgamated into large sandstone sheets with the development of high energy beach depositsand coastal sand flats in the uppermost part of the sequence. The presence of rill marks, flat-topped ripples, wrinkle marks, desiccation cracks and adhesion warts point to intertidal conditions with intermittent exposure. The high energy sandstone bars overlie a thick mudstone-dominated shelf sequence across a sharp interface indicating rapid change in the sea-level, provenance, rate of sediment generation and sediment input, and circulation condition in the shelf. A quiet muddy shelf was replaced by a major sand-depositing environment with strong, open marine circulation. An interplay of tidal currents, oscillatory wave currents and storm currents generated a complex flow pattern that varied in time and space from bimodal-bipolar to strongly unimodal flows. Close parallelism of wave ripple crests, trend of linear bars

  1. Variations of sulfur and carbon isotopes in seawater during the Doushantuo stage in late Neoproterozoic

    Institute of Scientific and Technical Information of China (English)

    ZHANG Tonggang; CHU Xuelei; ZHANG Qirui; FENG Lianjun; HUO Weiguo

    2003-01-01

    Successive analyses of sulfur and carbon isotopic compositions of carbonates strata in the Doushantuo Formation in the Yangtze area were accomplished through a method of extracting trace sulfate from carbonates. Sulfur and carbon isotopic compositions of coeval seawater were estimated from the samples that show the least diagenetic alteration. A high-resolution age curve of sulfur isotopes in seawater sulfates was obtained in the Doushantuo stage, which reflects thetrend of variation in seawater sulfur isotopes after the Neoproterozoic snowball Earth event. Similar characteristics of variation in carbon isotopes were observed in the coeval carbonates. A large positive δ34S excursion over +20‰ occurs in ancient seawater sulfates in the early Doushantuo stage. Simultaneously, the δ13C values in ancient seawater carbonates exhibit a positive excursion up to10‰. The maximum δ34S and δ13C values are +46.4‰ and +6.9‰, respectively. In the middle Doushantuo stage, the range of variation in δ34S values of seawater is relatively narrow, but δ13C values are quite high. Then, δ34S values of seawater become oscillating, and the same occurs in δ13C values. Negative excursions in δ34S and δ13C values occur simultaneously at the end of the Doushantuo stage, and the minimum δ34S and δ13C values dropped down to -10.1‰ and -5.7‰, respectively. The characteristics of variations in the sulfur and carbon isotopes of ancient seawater imply strong changes in oceanic environment that became beneficial to inhabitation and propagation of organism. The organic productivity and burial rate of organic carbon once reached a quite high level during the Doushantuo stage. However, the state of environment became unstable after the global glaciation. The global climate and environment possibly were fluctuating and reiterating. The negative excursions in δ34S and δ13C values occurring at the end of the Doushantuo stage may represent a global event, which might be related to

  2. The initiation of Neoproterozoic "snowball" climates in CCSM3: the influence of paleo-continental configuration

    Directory of Open Access Journals (Sweden)

    Y. Liu

    2013-07-01

    Full Text Available We identify the "hard snowball" bifurcation point at which total sea ice cover of the oceans is expected by employing the comprehensive coupled climate model CCSM3 for two realistic Neoproterozoic continental configurations, namely a low-latitude configuration appropriate for the 720 Ma Sturtian glaciation and a higher southern latitude configuration more appropriate for the later 635 Ma Marinoan glaciation. We find that for the same total solar insolation (TSI and atmospheric CO2 concentration (pCO2, the most recent continental configuration is characterized by colder climate than the 720 Ma continental configuration and enters the hard snowball state more easily on account of the following four factors: the low heat capacity of land in the south polar region, the higher albedo of the snow covered land compared to that of sea ice, the more negative net cloud forcing near the ice front in the Northern Hemisphere (NH, and more importantly, the more efficient sea ice transport towards the equator in the NH due to the absence of blockage by continents. Beside the paleogeography, we also find the optical depth of aerosol to have a significant influence on this important bifurcation point. When the high value (recommended by CCSM3 but demonstrated to be a significant overestimate is employed, the critical values of pCO2, beyond which a hard snowball will be realized, are between 80–90 ppmv and 140–150 ppmv for the Sturtian and Marinoan continental configurations, respectively. However, if a lower value is employed that enables the model to approximately reproduce the present-day climate, then the critical values of pCO2 become 50–60 ppmv and 100–110 ppmv for the two continental configurations, respectively. All of these values are higher than previously obtained for the present-day geography (17–35 ppmv using the same model, primarily due to the absence of vegetation, but are much lower than that obtained previously for the 635 Ma

  3. Petrogenesis and tectonic implications of the Neoproterozoic Datian mafic-ultramafic dykes in the Panzhihua area, western Yangtze Block, SW China

    Science.gov (United States)

    Yang, Yi-Jin; Zhu, Wei-Guang; Bai, Zhong-Jie; Zhong, Hong; Ye, Xian-Tao; Fan, Hong-Peng

    2017-01-01

    Mafic-ultramafic dykes are important geological markers that can punctuate the onset of crustal extension during the breakup of a continent and provide valuable information on the mantle source. This study reports secondary ion mass spectroscopy zircon and baddeleyite U-Pb ages, elemental and Nd isotopic data for the Datian mafic-ultramafic dykes in the Panzhihua area, western Yangtze Block, SW China. Two kinds of rocks are confirmed: the picritic rock and the dolerite. Based on petrographic and geochemical features, the dolerite dykes are further subdivided into two groups: Group I mafic and Group II mafic dykes, which emplaced at 760 Ma (zircon U-Pb) and 800 Ma (zircon and baddeleyite U-Pb), respectively. All samples from the picritic rocks and the Group I mafic rocks show the features of high-Ti and alkaline basaltic magma in composition as well as "humped" trace element patterns, which are similar to those of typical alkaline basalts associated with continental rifts except for the slightly negative Nb-Ta anomalies. The Group II mafic rocks display the features of low-Ti and tholeiitic magma, moderately enriched in LILE and LREE, and characterized by distinctively negative Nb-Ta anomalies. The primary magmas of the picritic rocks and the Group I mafic rocks were generated from ca 25 % partial melting of an OIB-like, Nd isotopically depleted but incompatible elements relatively enriched mantle source within a garnet stable field. The Group II mafic rocks crystallized from crustal contaminated mafic magmas that were derived from a spinel-bearing sub-continental lithospheric mantle source, because of low ratios of La/Yb, Ti/Y and Sm/Yb. Geochemical features suggest that these groups of mafic-ultramafic dykes were formed in a continental rift setting, but derived from different mantle sources. In combination with other Neoproterozoic igneous rocks in the western margin of Yangtze Block, it is suggested that the Datian mafic-ultramafic dykes in the Panzhihua area

  4. The Neoproterozoic-Cambrian Paraguay Belt, central Brazil: Part I - New structural data and a new approach on the regional implications

    Science.gov (United States)

    Silva, Luiz José Homem D'el-Rey; Walde, Detlef Hans-Gerd; Saldanha, Davi Oliveira

    2016-04-01

    Together with the Araguaia and Brasília belts, the Paraguay belt forms in central Brazil, the Tocantins Province that is one of the largest orogens of western Gondwana. The Corumbá area occupies the site where the northern and southern parts of the Paraguay belt form, together with the Chiquitos-Tucavaca aulacogen (stretching E-W in the adjacent Bolivian territory) an R-R-R basin system opened-filled in the ~ 700/650-540 Ma interval within the Amazon-Rio Apa paleo-continent. The sedimentary (volcanic) rocks of the Jacadigo and Corumbá Groups found around the Corumbá city record part of the Neoproterozoic-Cambrian passive margin precursor of the Paraguay belt. Our pioneer structural analysis reveals that these rocks experienced progressive deformation (phases D1-D2-D3) and low-grade metamorphism during the Brasiliano Cycle (540-513 Ma). The crystalline basement was also involved, according to structural data and K-Ar ages in the literature. The paleo-passive margin was thickened during the D1-D2 deformation and was lately shortened (D3) in two orthogonal directions, SE-NW (D3P) and SW-NE (D3T). Developed co-axially and verging to NW, D1-D2-D3P structures record the closure of the basin precursor of the Paraguay belt, whereas D3T structures seem related to the inversion of the aulacogen. Although the tectonic transport to NW, as observed in the Corumbá area, matches the reported transport of Paraguay belt's supracrustal rocks towards the eastern margin of the Rio Apa block and Araguaia belt's rocks towards the Amazon craton, the transport direction is opposite in other parts of the Paraguay belt. Our comprehensive discussion of these facts brings to light profound regional implications.

  5. Structural evolution and U-Pb SHRIMP zircon ages of the Neoproterozoic Maria da Fé shear zone, central Ribeira Belt - SE Brazil

    Science.gov (United States)

    Zuquim, M. P. S.; Trouw, R. A. J.; Trouw, C. C.; Tohver, E.

    2011-03-01

    The Maria da Fé Shear Zone (MFSZ) is a sinistral strike-slip kilometric-scale structure developed in the late Neoproterozoic during the assembly of Gondwana. The MFSZ development is related to the NW-SE collision between the São Francisco Paleocontinent and the Rio Negro Magmatic Arc, which formed the Ribeira Belt. This paper describes the shear zone in detail, concluding that the orientation and age are consistent with NW-SE shortening during the afore mentioned collision. A U-Pb SHRIMP Concordia age of 586.9 ± 8.7 Ma is reported from zircon grains of a granitic dyke that crystallised synkinematically to the main tectonic activity of the shear zone. Another group of zircon grains from the same sample generated an upper intercept age of 2083 ± 43 Ma anchored in the younger Concordia age. These zircon grains are interpreted as relict grains of the basement from which the granite dyke was generated by partial melting. The temperature during mylonitization in the MFSZ was estimated in the range from 450 to 600 °C, based on microstructures in quartz and feldspar. An earlier collision in the same region, between 640 and 610 Ma, led to an extensive nappe-stack with tectonic transport to ENE, integrating the southern Brasilia Belt. One of the thrust zones between these nappes in the studied area is the Cristina Shear Zone with mylonites that were generated under upper amphibolite to granulite facies conditions. Brittle-ductile E-W metric-scale shear zones are superimposed on the MFSZ, which were active in similar, but probably slightly cooler, metamorphic conditions (≈500 °C).

  6. High-pressure thermal aureoles around two Neoproterozoic synorogenic magmatic epidote-bearing granitoids, Northeastern Brazil

    Science.gov (United States)

    Caby, Renaud; Sial, Alcides N.; Ferreira, Valderez P.

    2009-02-01

    Unusual high-pressure inner thermal aureoles are described from the Minador and Angico Torto epidote-bearing tonalitic plutons that emplaced into greenschist-facies metasedimentary rocks of the Neoproterozoic Cachoeirinha-Salgueiro belt, northeastern Brazil. The foliated pelitic hornfelses display the mineral assemblage garnet, kyanite, staurolite, muscovite, biotite, plagioclase ± quartz. Rare fibrolite is only found very close to the contacts. Hornfelses display steep mineral lineations and steeply-dipping foliations concordant with magmatic contacts. Leucocratic veinlets containing quartz, oligoclase, garnet, kyanite, staurolite, rutile and ilmenite suggest that limited melting conditions were reached very close to magmatic contacts ( T ⩾ 650 °C, P around 8 kbar). These high-pressure hornfelses form a few meters thick, rigid envelopes around the two plutons. Contrary to known examples of kyanite-bearing hornfelses that recorded high-temperature decompression, the nearly isobaric cooling down to ca. 450 °C is constrained by 3.20-3.30 Si contents of retrogressive phengites from both inner hornfelses and ductilely-deformed tonalite at the pluton margins. Isograds and bathograds are, therefore, apparently telescoped due to HP/LT shearing, possibly caused by subsequent differential vertical movements affecting these two solidified plutons. The unusual depth of emplacement of these syn-kinematic calc-alkaline plutons is explained by a tentative geodynamic model involving a pre-620 Ma-subduction setting. Resumen Las aureolas internas que rodean dos plutones tonalíticos emplazados dentro de rocas cajas en facies esquistos verdes del Cinturón-plegado Cachoeirinha-Salgueiro al noreste de Brasil, contienen hornfelses pelíticos foliados con granate, kyanita, estaurolita, muscovita, biotita, plagioclasa ± cuarzo. Fibrolita es rara ó es encontrada solamente cerca de las zonas de contacto. Los hornfelses desarrollaron foliaciones concordantes con buzamiento fuerte

  7. Discovery of a Miaohe-type Biota from the Neoproterozoic Doushantuo Formation in Jiangkou County,Guizhou Province,China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yuanlong; CHEN Meng'e; PENG Jin; YU Meiyi; HE Minghua; WANG Yue; YANG Rongjun; WANG Pingli; ZHANG Zhenhan

    2004-01-01

    @@ A megascopic algal fossil assemblage was first discovered by Ma Guogan and Chen Meng'e in the black shales of the Neoproterozoic Doushantuo Formation in Miaohe Town, Zigui County, Hubei Province in 1978[1]. Formal naming of the Miaohe Biota was proposed by Cheng Meng'e and Xiao Zongzheng in 1991[2], and eleven morphological genera have been previously described, including megascopic algae and putative metazoans[3]. Ding et al.[4] greatly expanded the scope of the Miaohe Biota to 9 phyla consisting of 140 genera, including microphytoplanctons, megascopic algae, metazoans, sponges and trace fossils. Xiao et al.[5] further restudied this fossil assemblage, concluding that only about 18 distinct taxa could be recognized and that many Miaohe taxa are poorly defined or synonymous.

  8. Stromatolite branching in the Neoproterozoic of the Centralian Superbasin, Australia: an investigation into sedimentary and microbial control of stromatolite morphology.

    Science.gov (United States)

    Planavsky, Noah; Grey, Kathleen

    2008-01-01

    The extensive and well-preserved Neoproterozoic Acaciella australica Stromatolite assemblage of Australia is ideal for examining the relative roles of microbial and environmental influences on stromatolite branching and stromatolite macrostructure across a wide geographical area. Detailed sedimentological analyses indicate that the basal hemispheroidal section of bioherms contains abundant sediment. By contrast, the columnar sections of bioherms are composed almost exclusively of micritic laminae. These micritic laminae display little evidence for environmental, especially sedimentary, control over stromatolite morphology. The change from a hemispheroidal morphology to branching morphology is linked to variations in the relative contributions of sediment and framework growth. The shift to columns appears to be closely linked to a decrease in sediment supply that resulted in a more stable environment in which microbially mediated framework growth began to control stromatolite morphology. Branching in the A. australica assemblage stromatolites appears to be caused by shifting sedimentary and microbial control on stromatolite morphology.

  9. Macroalgal holdfasts and their interaction with environments from the Neoproterozoic Doushantuo Formation in Guizhou,South China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Numerous macro-organisms of the Doushantuo macrobiota, which were found in the black carbonaceous mudstone of the upper Neoproterozoic Ediacraan Doushan-tuo Formation in Jiangkou County, Guizhou Province, China, are considered to live on sea floor by their holdfasts. The appearance and preserved forms of the macroalgal holdfasts may provide some data to the study of the living and buried environments ofmacrobiota. They lived in the lower energy and clear environment, and fixed on a soupground with rich water (about 79% water). Currents, possibly ocean currents, could pull out the macroalgal holdfasts from the soupground and break off the macroalgal foliations. After such events, the corpses of macro-organisms would be covered in a reduced environment by the deposits. Afterwards, a new community, including regenerating and undying macro-organisms, lived continuously on a new deposit.

  10. Neoproterozoic magmatism in Southwestern Algeria (Sebkha el Melah inlier): a northerly extension of the Trans-Saharan orogen

    Science.gov (United States)

    Dostal, J.; Caby, R.; Keppie, J. D.; Maza, M.

    2002-08-01

    The Neoproterozoic Sebkha el Melah inlier is a part of the Pan-African Trans-Saharan orogenic belt that is exposed in northwestern Africa east of the West African craton. The inlier is composed of a 4-5 km thick sequence of fine-grained marine to fluvial clastic sedimentary rocks intercalated with, and conformably overlain by, mafic lava flows and proximal volcaniclastic deposits, 600-1000 m thick. The lava flows and associated minor intrusives are mainly shoshonites. Their geochemical characteristics are indicative of subduction-related magmas and are characterized by relative depletion of Nb, Ta and Ti with respect to rare-earth elements and Th. Their positive but highly variable ɛNd values (+1-+5) are interpreted to reflect contamination of mantle-derived mafic melts (˜+6) by continental crust. It is suggested that the Sebkha el Melah shoshonitic rocks formed in a backarc or rifted arc setting. Their location, close to the Trans-Saharan suture, is interpreted to be the result of subduction erosion which removed the forearc and possibly also part of the arc. The shallow source (Sebkha el Melah volcanic rocks is related to flat-slab subduction. Traced along strike to the south, the >620 Ma, Neoproterozoic volcanic suites of the Trans-Saharan belt change to typical continental, Andean margin calc-alkaline rocks in the northwestern Hoggar and an oceanic island arc complex in Mali. This may indicate that the rate of convergence of the West African craton and the Tuareg (Saharan) paleocontinent increased from south to north due to a change in the angle of convergence across the margin (oblique in the south to orthogonal in the north), resulting from the curve of the eastern margin of the West African craton that swings from N-S to NW-SE.

  11. 论中-新元古界的原生油气资源%On Meso-Neoproterozoic primary petroleum resources

    Institute of Scientific and Technical Information of China (English)

    王铁冠; 韩克猷

    2011-01-01

    在全球范围内,西伯利亚、非洲、东欧、印度、阿拉伯、澳大利亚等克拉通,均有中-新元古界至下寒武统原生油气与油气藏的报道,特别是东西伯利亚与阿曼两地,现探明的油气储量业已达到十亿吨级至亿吨级油当量的规模,证明中-新元古界的原生油气仍是一个值得关注的能源资源领域.中国中-新元古界,乃至下古生界,热演化程度普遍处于过成熟状态,不利于液态石油的保存,目前尚未发现其原生油田,但是,在一些地区已发现大量中-新元古界油苗,或大规模的沥青脉,剖析其中-新元古界的含油性,有利于指导中-新元古界原生油气资源的勘探.以扬子克拉通川西北龙门山前山带,以及华北克拉通燕山北部坳陷带为例,由于上覆沉积盖层累计厚度较薄,中-新元古界无深埋经历,或者岩石圈异常增厚,形成"冷圈、冷盆"的地质条件,中-新元古界原生烃类始终处于石油"液态窗"内,仍有利于中-新元古界原生油气资源的保存.%In view of global scale, primary oil and gas reservoirs of the Meso-Neoproterozoic, and even the Lower Cambrian, have been reported in cratons of Siberia, Africa, East Europe, India, Arabia and Australia, especially in the East Siberia and Oman regions, so far the proved oil and gas reserves are up to a scale of 108t to 109t of oil equivalents, which testifies that the Meso-Neoproterozoic petroleum is an energy resource realm worthy of notice. In China, the thermal evolution levels of the Meso-Neoproterozoic, and even the Lower Palaeozoic strata are commonly in overmature phase unfavorable for the preservation of liquid oils, thus,Meso-Neoproterozoic primary oilfields are not yet discovered up to now. However, a large number of oil seepages and/or large scale bituminous veins are found in the Meso-Neoproterozoic, the analysis of the primary petroleum prospectivity would be helpful to guiding the exploration of Meso-Neoproterozoic

  12. Molybdenum (Mo) and Iron (Fe) Isotope Evidence of Tepla-Barrandian Black Shales Against Widespread Deep Ocean Oxygenation in the Late Neoproterozoic

    Science.gov (United States)

    Kurzweil, F.; Pasava, J.; Drost, K.; Wille, M.; Schoenberg, R.

    2014-12-01

    The late Neoproterozoic was a period of major environmental perturbations including tectonic reorganizations, biologic evolution and environmental oxygenation (Neoproterozoic oxygenation event). Authigenic enrichments in redox-sensitive elements such as Mo, V and U in late Neoproterozoic black shales prior to the appearance of the first metazoan fossils indicate that increasing oxygen levels in the atmosphere-hydrosphere system have facilitated the evolution and diversification of multi-cellular life. The isotopic composition of these elements is another tool to trace (possibly global) changes in the oceanic redox state. For example, significantly higher δ98Mo of seawater and black shales are expected, when the sink of isotopically light Mo in oxic deep marine settings increased. Accordingly, modern anoxic sediments in the Black Sea as well as the well oxygenated seawater show high δ98Mo of 2.3 ‰. However, Mesoproterozoic black shales show relatively low δ98Mo values up to 1.4 ‰. To test if the enrichment of redox-sensitive elements and metazoan evolution temporally correlate with an increase in seawater δ98Mo, we present Mo and Fe isotope data of slightly younger late Neoproterozoic black shales of the Tepla-Barrandian, Czech Republic. We observe a perfect correlation of Fe/Al ratios with δ56Fe that is best explained by mixing of detrital derived Fe with δ56Fe of ~0.1 ‰ and hydrothermal sourced Fe with δ56Fe of ~-0.7 ‰. Hydrothermally dominated samples with low δ56Fe are also enriched in heavy metals such as Ni, Cu and Zn as well as hydrothermally derived Mo (with δ98Mo of ~0.6 ‰). Samples with minor hydrothermal influence show authigenic Mo enrichment from seawater with a maximum δ98Mo of 1.2 ‰. This estimate indicates no significant increase in the seawater δ98Mo during the Neoproterozoic and after the evolution of metazoan life. Thus, our Mo isotope dataset provides no evidence for deep ocean oxygenation during the Neoproterozoic

  13. Petrogenesis of the Neoproterozoic Ngondo Plutonic complex (Cameroon, west central Africa): a case of late-collisional ferro-potassic magmatism

    Science.gov (United States)

    Tagne-Kamga, Gabriel

    2003-04-01

    The Ngondo complex is a late-collisional pluton, which was emplaced around 600 Ma along a N030° E strike-slip shear zone in the southwestern part of the Neoproterozoic Fold Belt of Cameroon. It comprises three successively emplaced plutonic groups of rocks: (i) mafic to felsic intrusive rocks (MFR), (ii) fine-grained granites (FGG) and (iii) coarse-grained granites (CGG). Late aplitic and pegmatite dykes were emplaced along brittle fractures in these plutons. The complex is metaluminous to weakly peraluminous, high-K, calc-alkaline to " trans-alkaline" ferro-potassic, with mineralogical and geochemical characteristic of I-type granites. The plutonic rocks are characterised by high Ba, Sr, Rb and ∑REE concentrations and low Ni and Cr contents in the mafic members. They also display chondrite-normalised REE patterns characterised by variable LREE enrichment, moderate to minor HREE fractionation with moderate to pronounced negative Eu anomalies (Eu/Eu∗: 0.6-0.9 (MFR), 0.2-0.5 (FGG), 0.3-0.7 (CGG)). Trace element distribution patterns for the three plutonic groups are similar with a distinctive depletion in Nb, Sr and Ti relative to other trace elements and a greater enrichment in LILE compared to HFSE. These plutonic groups present distinct evolutionary trends precluding their origin from differentiation of a single parental magma. The geochemical and isotopic data indicate that they derived from partial melting of heterogeneous (meta)-igneous mafic lower crustal materials, having possibly the composition of amphibolitised high-K calc-alkaline basaltic andesites and andesitic metagreywackes. Petrographic evidences such as the presence of quartz-ocelli, xenocrysts of feldspar, fragments of country rocks (migmatitic gneisses) strongly indicate that crustal contamination may have played an important role in the genesis of the plutonic rocks. This contamination process is further supported by the variation of major and trace elements together with Sr-Nd isotopic data

  14. Neoproterozoic granitoids associated with the Bou-Azzer ophiolitic melange (Anti-Atlas, Morocco): evidence of adakitic magmatism in an arc segment at the NW edge of the West-African craton

    Science.gov (United States)

    Beraaouz, E. H.; Ikenne, M.; Mortaji, A.; Madi, A.; Lahmam, M.; Gasquet, D.

    2004-06-01

    The Neoproterozoic intrusions of the Bou-Azzer El Graara inlier consist of metaluminous, medium to high-K, I-type granitoids. Two groups of granitoids can be distinguished based on chemistry and isotopic signature: (1) the early (≈670 Ma) medium-K calc-alkaline, pre-collisional diorites of Ousdrat, Bou-Azzer, Bou-Izbane, and Ait-Hmane, with less fractionated REE patterns (2.6 Bleida characterized by relatively more fractionated REE patterns (8.9 15%, 3 < %Na 2O < 6.4, Yb < 1.8 ppm, Y < 20 ppm and isotopic ratios of Sr and Nd similar to the ophiolitic rocks). However their La/Yb and Sr/Y are relatively low in most of the samples. The origin of these arc magmas is not completely understood. In this paper we argue that some of these rocks probably contain components of adakitic melts. The early group was produced by partial melting of subducted oceanic crust followed by interaction of the melt with the overlying mantle wedge, and the late group by dehydration melting of underplated basalts in the lower crust in the garnet stability field.

  15. Towering sponges in an Early Cambrian Lagerstätte: Disparity between nonbilaterian and bilaterian epifaunal tierers at the Neoproterozoic-Cambrian transition

    Science.gov (United States)

    Yuan, Xunlai; Xiao, Shuhai; Parsley, Ronald L.; Zhou, Chuanming; Chen, Zhe; Hu, Jie

    2002-04-01

    Epifaunal, suspension-feeding bilaterian animals in the Cambrian lived close to the sediment-water interface, and hence their ecological tiering levels were low (Burgess Shale, and Sinsk biotas. These data are consistent with medium- to high-tiering levels in Neoproterozoic-Cambrian epifaunal communities, but suggest that nonbilaterians achieved such tiering levels long before bilaterian suspension feeders did so in the Early Ordovician. The disparity between bilaterian and nonbilaterian tierers during the Neoproterozoic-Cambrian transition and the delayed appearance of high-tiering bilaterians demand phylogenetic and ecological explanations. The Cambrian substrate revolution may have triggered a cascade of ecological evolution, including the rise of bilaterian animals in high-tiering levels during the Ordovician radiation of the Paleozoic fauna.

  16. δ13Ccarb and Ceanom excursions in the post-glacial Neoproterozoic and Early Cambrian interval in Guizhou,South China

    Institute of Scientific and Technical Information of China (English)

    FENG Hongzhen; LING Hongfei; JIANG Shaoyong; YANG Jinghong

    2004-01-01

    Secular δ 13Ccarb and Ceanom profiles in the post-glacial Neoproterozoic and Early Cambrian interval are reported from Guizhou on the southeasten border of the Yangtze platform, South China. Overall, the δ 13Ccarb profile drifts to negative values in the post-glacial Nantuo and lower to middle Doushantuo Formations, and then to positive values in the upper Doushantuo and Dengying Formations of Neoproterozoic, followed by negative values in the Lower Cambrian Gezhongwu and Niutitang Formations. A detailed investigation of the relationship between the δ 13Ccarb and Ceanom profiles reveals that the main anoxic and oxic episodes are coupled with negative and positive δ 13Ccarb values, respectively. This may suggest a control of alternation between ocean stratification and mixing on variations in 13C abundance in the ancient ocean of the investigated areas.

  17. Petrogenesis of the Neoproterozoic bimodal volcanic rocks along the western margin of the Yangtze Block: New constraints from Hf isotopes and Fe/Mn ratios

    Institute of Scientific and Technical Information of China (English)

    LI Xianhua; QI Changshi; LIU Ying; LIANG Xirong; TU Xianglin; XIE Liewen; YANG Yueheng

    2005-01-01

    High-precision major element and Hf isotope data are reported for the Neoproterozoic Suxiong volcanic rocks along the western margin of the Yangtze Block. These volcanic rocks have variable εHf(T) values and Fe/Mn ratios. The relatively primitive basalts have high Fe/Mn ratios and high Hf-Nd isotopic compositions, indicating that they were generated by partial melting of garnet clinopyroxene in mantle plume at high pressure. Thus, the Suxiong basalts are genetically related to the proposed Neoproterozoic superplume. On the contrary, a few differentiated basalts have low Fe/Mn ratios and low Hf-Nd isotopic compositions. They are likely to experience assimilation-fractional crystallization process. The Suxiong rhyolites have consistent Hf and Nd model ages of 1.3-1.4 Ga. They are likely generated by shallow dehydration melting of pre-existing young arc igneous rocks associated with the basaltic underplating/intrusion in a continental rift.

  18. Stratigraphic architecture of the Neoproterozoic glacial rocks in the "Xiang-Qian-Gui" region of the central Yangtze Block, South China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qirui; CHU Xuelei; Heinrich BAHLBURG; FENG Lianjun; Nicole DOBRZINSKI; ZHANG Tonggang

    2003-01-01

    The Yangtze Block in South China is one of the important regions where Neoproterozoic glacial rocks are well developed and studied. However, the classification and correlation of the Neoproterozoic glacial sequences in the central Yangtze Block still remain controversial among Chinese geologists. The original Sinian sections around the Yangtze Gorges Region became an official standard for classification and correlation since the 1950s. Subsequent regional geologic studies, however, resulted in different classification and correlation, because of its incompleteness. We select one of the complete sections in the bordering areas of Xiang (Hunan), Qian (Guizhou) and Gui (Guangxi), as a standard of classification and correlation. The temporal and spatial distribution, i.e. the stratigraphic architecture, of the glacial rocks in the central Yangtze Block is suggested. Our results indicate that the glacial sequence on the Yangtze Block was deposited during the Nantuo Ice-age, the Datangpo Interglacial-age and Jiangkou Ice-age, in descending order.

  19. Diachronism in the late Neoproterozoic-Cambrian arc-rift transition of North Gondwana: A comparison of Morocco and the Iberian Ossa-Morena Zone

    Science.gov (United States)

    Álvaro, J. Javier; Bellido, Félix; Gasquet, Dominique; Pereira, M. Francisco; Quesada, Cecilio; Sánchez-García, Teresa

    2014-10-01

    In the northwestern border of the West African craton (North Gondwana), a transition from late Neoproterozoic subduction/collision to Cambrian rift processes was recorded in the Anti-Atlas (Morocco) and in the Ossa-Morena Zone (Iberia). Cambrian rifting affected both Pan-African and Cadomian basements in a stepwise and diachronous way. Subsequently, both areas evolved into a syn-rift margin episodically punctuated by uplift and tilting that precluded Furongian sedimentation. A comparison of sedimentary, volcanic and geodynamic evolution is made in the late Neoproterozoic (Pan-African and Cadomian) belts and Cambrian rifts trying to solve the apparent diachronous (SW-NE-trending) propagation of an early Palaeozoic rifting regime that finally led to the opening of the Rheic Ocean.

  20. Evidence for Mojave-Sonora megashear-Systematic left-lateral offset of Neoproterozoic to Lower Jurassic strata and facies, western United States and northwestern Mexico

    Science.gov (United States)

    Stewart, John H.

    2005-01-01

    Major successions as well as individual units of Neoproterozoic to Lower Jurassic strata and facies appear to be systematically offset left laterally from eastern California and western Nevada in the western United States to Sonora, Mexico. This pattern is most evident in units such as the "Johnnie oolite," a 1- to 2-m-thick oolite of the Neoproterozoic Rainstorm Member of the Johnnie Formation in the western United States and of the Clemente Formation in Sonora. The pattern is also evident in the Lower Cambrian Zabriskie Quartzite of the western United States and the correlative Proveedora Quartzite in Sonora. Matching of isopach lines of the Zabriskie Quartzite and Proveedora Quartzite suggests ???700-800 km of left-lateral offset. The offset pattern is also apparent in the distribution of distinctive lithologic types, unconformities, and fossil assemblages in other rocks ranging in age from Neoproterozoic to Early Jurassic. In the western United States, the distribution of facies in Neoproterozoic and Paleozoic strata indicates that the Cordilleran miogeocline trends north-south. A north-south trend is also suggested in Sonora, and if so is compatible with offset of the miogeocline but not with the ideas that the miogeocline wrapped around the continental margin and trends east-west in Sonora. An imperfect stratigraphic match of supposed offset segments along the megashear is apparent. Some units, such as the "Johnnie oolite" and Zabriskie-Proveedora, show almost perfect correspondence, but other units are significantly different. The differences seem to indicate that the indigenous succession of the western United States and offset segments in Mexico were not precisely side by side before offset but were separated by an area-now buried, eroded, or destroyed-that contained strata of intermediate facies. ?? 2005 Geological Society of America.

  1. Association of Neoproterozoic A- and I-type Granites in South China: Implications for Generation of A-type Granites in A Subduction-related Environment

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xin-fu; ZHOU Mei-fu; LI Jian-wei; WU Fu-yuan

    2008-01-01

    @@ Neoproterozoic magmatism in the Yangtze Block of South China produced voluminous S- and I-type granites, and sparse A-type granites. The Daxiangling A-type granitic pluton is spatially associated with the Shimian I-type pluton at the western margin of the Yangtze Block. Both plutons have similar SHRIMP zircon U-Pb ages of~800 Ma and are slightly younger than the tonalite-trondhjemite-granodiorite (TTG) gneisses in the area.

  2. Neoproterozoic diamictite in the Eastern Desert of Egypt and Northern Saudi Arabia: evidence of ~750 Ma glaciation in the Arabian-Nubian Shield?

    Science.gov (United States)

    Ali, Kamal A.; Stern, Robert J.; Manton, William I.; Johnson, Peter R.; Mukherjee, Sumit K.

    2010-06-01

    The Neoproterozoic Atud diamictite in Wadi Kareim and Wadi Mobarak in the Eastern Desert of Egypt and the Nuwaybah formation in NW Saudi Arabia consist of poorly sorted, polymictic breccia, with clasts up to 1 m of granitoid, quartz porphyry, quartzite, basalt, greywacke, marble, arkose, and microconglomerate in fine-grained matrix. Stratigraphic relations indicate that the diamictite was deposited in a marine environment. Integrated field investigation, petrographic study and U-Pb SHRIMP zircon ages demonstrate that the Atud and Nuwaybah are correlative. The distribution of zircon ages indicate that ~750 Ma ages are dominant with a significant component of older materials, characterized by minor Mesoproterozoic and more abundant Paleoproterozoic and Neoarchean ages. Some matrix and metasedimentary clast zircons yield ages that are a few 10s of Ma younger than the age of the youngest clast (754 ± 15 Ma), suggesting Atud/Nuwaybah diamictite deposition ~750 Ma or slightly later, broadly consistent with being deposited during the Sturtian glaciation (740-660 Ma). The Paleoproterozoic and Neoarchean clasts have no source within the ensimatic Arabian-Nubian Shield. The distribution of the pre-Neoproterozoic ages are similar to the distribution of the pre-Neoproterozoic ages in Yemen and Saharan Metacraton, suggesting that these clasts have been transported hundreds of kilometers, maybe by ice-rafting. The Atud diamictite may represent important evidence for Cryogenian “Snowball Earth” in the Arabian-Nubian Shield.

  3. Hypothesized link between Neoproterozoic greening of the land surface and the establishment of an oxygen-rich atmosphere

    Science.gov (United States)

    Kump, Lee R.

    2014-01-01

    Considerable geological, geochemical, paleontological, and isotopic evidence exists to support the hypothesis that the atmospheric oxygen level rose from an Archean baseline of essentially zero to modern values in two steps roughly 2.3 billion and 0.8–0.6 billion years ago (Ga). The first step in oxygen content, the Great Oxidation Event, was likely a threshold response to diminishing reductant input from Earth’s interior. Here I provide an alternative to previous suggestions that the second step was the result of the establishment of the first terrestrial fungal–lichen ecosystems. The consumption of oxygen by aerobes respiring this new source of organic matter in soils would have necessitated an increase in the atmospheric oxygen content to compensate for the reduced delivery of oxygen to the weathering environment below the organic-rich upper soil layer. Support for this hypothesis comes from the observed spread toward more negative carbon isotope compositions in Neoproterozoic (1.0–0.542 Ga) and younger limestones altered under the influence of ground waters, and the positive correlation between the carbon isotope composition and oxygen content of modern ground waters in contact with limestones. Thus, the greening of the planet’s land surfaces forced the atmospheric oxygen level to a new, higher equilibrium state. PMID:25225378

  4. Depositional tracts and stratigraphic architecture of the Itajaí Basin sedimentary sucessions (Neoproterozoic, northeastern Santa Catarina, Brazil

    Directory of Open Access Journals (Sweden)

    Michel Silva Costa

    2015-06-01

    Full Text Available Neoproterozoic sedimentary successions of the Itajaí Basin show depositional trends and a stratigraphic framework characteristics of foreland basin system. The sedimentary environments have developed in basin conditions ranging from deep marine context, transitional shallow marine, to continental. Stratigraphic architecture comprises three depositional tracts (DT: DTI - submarine fans system that records the initial basin sedimentation and involves frontal and distal turbiditic deposits; DTII - transitional to shallow marine depositional system that represents the efective infill fase of basin, and includes deltaic succession with braided channels dominated plain; and DTIII - fluvial braided and alluvial fan depositional system that comprises the final stage of basin sedimentation. Arkoses and greywacke of the DTI present paleocurrent unimodals patterns and general trend to south-southeast, suggesting source area from Santa Catarina Granulitic Complex. The sandstones and conglomerates of DTII and DTIII have opposite paleocurrent pattern, indicating source area from both Metamorphic Brusque Complex and Florianópolis Batolith. Integration of paleoenvironmental and stratigraphic data, with previous information (U-Pb in detrital zircon, allowed a consistent interpretation on the sedimentary evolution and detrital sources of the basin and represent a progress on the discussions on the knowledge of the Itajaí Basin and its significance in the evolutionary context of the Dom Feliciano Belt.

  5. Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG

    2003-01-01

    Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.

  6. Pedogenic calcretes within fracture systems and beddings in Neoproterozoic limestones of the Irecê Basin, northeastern Brazil

    Science.gov (United States)

    Borges, S. V. F.; Balsamo, F.; Vieira, M. M.; Iacumin, P.; Srivastava, N. K.; Storti, F.; Bezerra, F. H. R.

    2016-07-01

    Calcretes or caliches are continental limestones developed by surficial weathering process that takes place mostly in arid and semi-arid regions. In the Irecê Basin, northeastern Brazil, in addition to the regular occurrence of pedogenic calcretes, a peculiar type of structurally controlled calcretes occurs on Neoproterozoic limestones. These peculiar calcretes developed near the surface and occur (1) between layers, (2) inside fractures and (3) within major thrust faults. Fieldwork on selected outcrops was integrated with petrographic, mineralogic, geochemical, density and mercury intrusion porosity analyses to constrain the environment of formation and their petrophysical properties. The results revealed that this type of calcrete is the product of multiepisodic events of dissolution and precipitation occurring during the wet and dry seasons in the region along fractures and beddings. Based on the petrophysical results, we suggest that these calcretes may have an important role in the migration of fluids through the impermeable host carbonate rock and that they act as a conduit for fluid flow, as revealed by their high porosity (mean value = 26%) and remarkable pore connectivity.

  7. Volcanosedimentary Basins in the Arabian-Nubian Shield: Markers of Repeated Exhumation and Denudation in a Neoproterozoic Accretionary Orogen

    Directory of Open Access Journals (Sweden)

    Victoria Pease

    2013-07-01

    Full Text Available The Arabian-Nubian Shield (ANS includes Middle Cryogenian-Ediacaran (790–560 Ma sedimentary and volcanic terrestrial and shallow-marine successions unconformable on juvenile Cryogenian crust. The oldest were deposited after 780–760 Ma shearing and suturing in the central ANS. Middle Cryogenian basins are associated with ~700 Ma suturing in the northern ANS. Late Cryogenian basins overlapped with and followed 680–640 Ma Nabitah orogenesis in the eastern ANS. Ediacaran successions are found in pull-apart and other types of basins formed in a transpressive setting associated with E-W shortening, NW-trending shearing, and northerly extension during final amalgamation of the ANS. Erosion surfaces truncating metamorphosed arc rocks at the base of these successions are evidence of periodic exhumation and erosion of the evolving ANS crust. The basins are evidence of subsequent subsidence to the base level of alluvial systems or below sea level. Mountains were dissected by valley systems, yet relief was locally low enough to allow for seaways connected to the surrounding Mozambique Ocean. The volcanosedimentary basins of the ANS are excellently exposed and preserved, and form a world-class natural laboratory for testing concepts about crustal growth during the Neoproterozoic and for the acquisition of data to calibrate chemical and isotopic changes, at a time in geologic history that included some of the most important, rapid, and enigmatic changes to Earth’s environment and biota.

  8. Geochemistry of meta-igneous rocks from southern Ethiopia: a new insight into neoproterozoic tectonics of northeast Africa

    Science.gov (United States)

    Alene, Mulugeta; Barker, Andrew J.

    1997-04-01

    Utilising geochemical data, various discriminant diagrams have been employed to establish the magma type and original tectonic environment for some Neoproterozoic amphibolites, ultrabasic rocks and gabbros of the Moyale area, southern Ethiopia. The gneissic amphibolites are found to have mixed geochemical characteristics indicative of island arc and/or ocean ridge basalts with tholeiitic composition whereas the porphyritic amphibolites show alkalic features with no clear tectonic setting. The ultrabasic and gabbroic units of the Moyale area are described in terms of their relation with mantle melts and parental material. The majority of ultrabasics relate to a cumulate origin and the gabbroic rocks appear as more differentiated magma from the same source. The mainly dunite bodies in the eastern sub-area at Moyale probably represent refractory residues left after variable degree of partial melting of a periodotite mantle. It is concluded that the gneissic amphibolites were probably part of an accreting arc associated with closure of a pre-existing oceanic basin. The ultrabasic and gabbroic rocks (together with the porphyritic amphibolite) are considered to be remnants of oceanic crust.

  9. Petrology of a Neoproterozoic Alaskan-type complex from the Eastern Desert of Egypt: Implications for mantle heterogeneity

    Science.gov (United States)

    Khedr, Mohamed Zaki; Arai, Shoji

    2016-10-01

    This paper details petrological and geochemical studies of an ultramafic-mafic intrusion in the Southern Eastern Desert of Egypt. The Dahanib complex shows a concentric zonation, from dunites at the core, through chromitites, clinopyroxene-rich dunites, wehrlites, harzburgites, gabbronorites and layered gabbros, to hornblende gabbros/diorites at the rim, similar to other Alaskan-type complexes. These lithologies typically feature cumulate textures and layering. Their pyroxenes (Mg#s, 0.54-0.94) evidence Fe, Mn and Na enrichment, but Al, Cr, Mg and Ti are depleted with differentiation. Their chromian spinels have a wide range of Cr# (0.31-0.61), along with high Ti and Fe, as a result of their origin through crystal accumulation and reaction with interstitial liquids. The clinopyroxenes (Cpxs) in peridotites and gabbroic rocks, which are high in REE concentration (2-100 times chondrite), are depleted in LREE relative to HREE and are similar to Cpx crystallized from asthenospheric melts. The mineral inclusions in spinel, the chemistry of Cpx in peridotites (rich in Al, Cr, Na, Ti and ΣREE = 13.7), and the melts in equilibrium with Cpx suggest that the Neoproterozoic lithosphere were partially refertilized by trace asthenospheric melts. The early magmas were possibly enriched by Mg, Cr, Ni, Ti, V and Sr, while the evolved types were rich in Fe, Mn, Na, Li, Zr, Co and REE via crystal accumulation and the interaction with interstitial liquids. The Neoproterozoic sub-arc mantle in Egypt is chemically heterogeneous and generally low in Nb, Ta, Zr and K, due to the low solubility of HFSE in slab-derived fluids and no other external addition of these elements. The large variations in lithology and chemistry, as well as the occurrence of scattered chromitite clots in the Dahanib peridotites, are related to a continuous supply of primitive magmas and/or the reaction between interstitial liquids and early cumulus crystals during multistage fractional crystallization. The

  10. Iso-Naakkima, a circular structure filled with Neoproterozoic sediments, Pieksämäki, southeastern Finland

    Directory of Open Access Journals (Sweden)

    Elo, S.

    1993-06-01

    Full Text Available A circular Bouguer gravity anomaly with a minimum of -4.0 mGal and halfamplitude width of 2 km was recognized at Lake Iso-Naakkima (62°11'N, 27°09'E, southeastern Finland. The gravity low is associated with subdued aeromagnetic signature and notable airborne and ground electromagnetic anomalies that indicate low bedrock resistivity. The drilling record beneath the recent (Quaternary glacial sediments, 25-40 m thick, reveals a 100 m thick sequence of unmetamorphosed shale, siltstone, quartz sandstone, kaolinitic clay and conglomeratic sandstone that rest on a weathered mica gneiss basement. The upward fining sequence is characterized by red colour, high kaolinite content, and tilted, distorted and brecciated beds. According to the geophysical modelling the diameter of the whole basin is 3 km and that of the sedimentary rocks 2 km, and the depth is 160 m. Shock lamellas in quartz clasts of the basal conglomeratic sandstone, almost omnipresent kink banding in micas of the rocks beneath the basin floor and the occurrence of polymictic dike breccia in the underlying mica gneiss suggest shock metamorphism. It was concluded that the basin originated by a meteorite impact. However, the impact-generated rocks were subsequently eroded before the sedimentation and only minor marks of shock metamorphism were preserved. Lateritic weathering took place prior to deposition of the sediments. Quartz sandstone and siltstone are interpreted as fluvial deposits and the thinly laminated shales as transgressi ve lacustrine or lagoonal deposits. The microfossil assemblage in the shale includes sphaeromorphs of acritarchs from Late Riphean (Neoproterozoic. Postdepositional subsidence of the Iso-Naakkima basin, shown by tilted sediments, preserved the sequence from further erosion.

  11. U-Pb zircon geochronology and Nd-Hf-O isotopic systematics of the Neoproterozoic Hadb adh Dayheen ring complex, Central Arabian Shield, Saudi Arabia

    Science.gov (United States)

    Ali, Kamal A.; Jeon, Heejin; Andresen, Arild; Li, Shuang-Qing; Harbi, Hesham M.; Hegner, Ernst

    2014-10-01

    A combined study of single zircon U-Pb dating, Hf-O zircon isotopic analyses and whole-rock Nd isotopic compositions was carried out to infer the magma sources of Neoproterozoic post-collisional A-type granitoids in Saudi Arabia. U-Pb zircon dating of magmatic zircons of two samples from the Hadb adh Dayheen ring complex yielded ages of 625 ± 11 Ma for a hornblende-biotite granite sample, and 613 ± 4 Ma for a monzogranite sample. The granitic rocks show initial εNd values of + 4.1 to + 5.3 and εHf of + 4.5 to + 8.4 that are lower than those of a model depleted mantle (εHf ~+ 14 and εNd ~+ 6.5) and consistent with melting of subduction-related crustal protoliths that were formed during the Neoproterozoic assembly of the Arabian-Nubian Shield (ANS). Crustal-model ages (Hf-tNC) of 0.81 to 1.1 Ga are inconsistent with depleted-mantle Nd model ages of 0.71 to 0.81 Ga and indicate that the post-collisional Hadb adh Dayheen granites were derived mostly from juvenile crust formed in Neoproterozoic time. Single zircons data show a wide range in δ18O values from + 3.2‰ to + 6.4‰, possibly indicating crystallization of zircon from magma derived from magmatic rocks altered by meteoric water in a magma chamber-caldera system.

  12. Mid-Neoproterozoic (ca. 830-800 Ma) metamorphic P-T paths link Tarim to the circum-Rodinia subduction-accretion system

    Science.gov (United States)

    Ge, Rongfeng; Zhu, Wenbin; Wilde, Simon A.

    2016-06-01

    Long-lived exterior accretionary orogeny shapes tectonothermal evolution of the peripheral building blocks of supercontinents and leads to considerable crustal growth. However, such accretionary orogeny has only been locally recognized for the Rodinia supercontinent. Here a suite of newly discovered mid-Neoproterozoic high-grade metamorphic rocks in the northern Tarim Craton, NW China, are used to test the exterior accretion hypothesis for Rodinia. These rocks occur as dark-colored mafic and calc-silicate boudins in impure marbles and mica schists. Geochemical data suggest a protolith of arc-related basalts metasomatized by Ca-rich fluids. Mineral assemblages, phase diagram modeling, and mineral compositions for a garnet pyroxenite and a garnet clinopyroxene gneiss reveal upper amphibolite to high-pressure granulite facies peak metamorphism (660-700°C, 11-12 kbar) following a counterclockwise P-T path, which is characterized by prograde burial and heating, followed by near-isothermal burial and retrograde exhumation and cooling. This P-T path is interpreted to have recorded crustal thickening of an earlier magmatic arc transformed to a fore arc by subduction erosion and subsequent burial along bent isotherms near the subduction channel. All studied samples record ca. 830-800 Ma metamorphic zircon U-Pb ages, which probably date the early exhumation and cooling according to Ti-in-zircon temperatures, zircon rare earth element patterns, and Hf isotopes. This is the first mid-Neoproterozoic P-T-t path in Tarim, and it provides metamorphic evidence for a mid-Neoproterozoic advancing-type accretionary orogeny, which is coeval with the initial breakup events of Rodinia and thus links Tarim to the circum-Rodinia accretion system, supporting the peripheral subduction model.

  13. SHRIMP Zircon U-Pb Dating of Gabbro and Granite from the Huashan Ophiolite, Qinling Orogenic Belt, China: Neoproterozoic Suture on the Northern Margin of the Yangtze Craton

    Institute of Scientific and Technical Information of China (English)

    SHI Yuruo; LIU Dunyi; ZHANG Zongqing; MIAO Laicheng; ZHANG Fuqin; XUE Hongmei

    2007-01-01

    The recently identified Huashan ophiolitic mélange was considered as the eastern part of the Mianliie suture in the Qinling orogenic belt. SHRIMP zircon U-Pb geochronology on gabbro from the Huashan ophiolite and granite intruding basic volcanic rocks indicates crystallization ages of 947±14Ma and 876±17 Ma respectively. These ages do not support a recently proposed Hercynian Huashan Ocean, but rather favor that a Neoproterozoic suture assemblage (ophiolite) is incorporated into the younger (Phanerozoic) Qinling orogenic belt.

  14. Chemostratigraphy of the Neoproterozoic Mirassol d'Oeste cap dolostones (Mato Grosso, Brazil): An alternative model for Marinoan cap dolostone formation

    Science.gov (United States)

    Font, E.; Nédélec, A.; Trindade, R. I. F.; Macouin, M.; Charrière, A.

    2006-10-01

    We have conducted a detailed study of the Neoproterozoic Mirassol d'Oeste cap dolostones that overlay the glacial diamictites of the Puga Formation (˜ 635 Ma, Amazon craton, Brazil) in order to understand the formation of these post-glacial dolostones. Petrographic features indicate that the dolostones are primary to early diagenetic in origin and precipitated in a moderately shallow-water platform corresponding to a carbonate ramp during transgressive conditions. Major and trace element contents, as well as C and O isotopic signatures, are consistent with an anoxic sediment influenced by sulphate-reducing bacteria. Such an environment is known to provide favourable conditions for the precipitation of dolomite as observed nowadays in modern hypersaline lagoons. Isotopic compositions of tube-like structures suggest local upward fluid seepage from the underlying cap dolostone. Our data concur with geochemical data from other Neoproterozoic cap dolostones to support a microbially-mediated model in specific environmental conditions for the formation of these unusual deposits worldwide.

  15. Mineral chemistry of isotropic gabbros from the Manamedu Ophiolite Complex, Cauvery Suture Zone, southern India: Evidence for neoproterozoic suprasubduction zone tectonics

    Science.gov (United States)

    Yellappa, T.; Tsunogae, T.; Chetty, T. R. K.; Santosh, M.

    2016-11-01

    The dismembered units of the Neoproterozoic Manamedu Ophiolite Complex (MOC) in the Cauvery Suture Zone, southern India comprises a well preserved ophiolitic sequence of ultramafic cumulates of altered dunites, pyroxenites, mafic cumulates of gabbros, gabbro-norites and anorthosites in association with plagiogranites, isotropic gabbros, metadolerites, metabasalts/amphibolites and thin layers of ferruginous chert bands. The isotropic gabbros occur as intrusions in association with gabbroic anorthosites, plagiogranite and metabasalts/amphibolites. The gabbros are medium to fine grained with euhedral to subhedral orthopyroxenes, clinopyroxenes and subhedral plagioclase, together with rare amphiboles. Mineral chemistry of isotropic gabbros reveal that the clinopyroxenes are diopsidic to augitic in composition within the compositional ranges of En(42-59), Fs(5-12), Wo(31-50). They are Ca-rich and Na poor (Na2O < 0.77 wt%) characterized by high-Mg (Mg# 79-86) and low-Ti (TiO2 < 0.35 wt%) contents. The tectonic discrimination plots of clinopyroxene data indicate island arc signature of the source magma. Our study further confirms the suprasubduction zone origin of the Manamedu ophiolitic suite, associated with the subduction-collision history of the Neoproterozoic Mozambique ocean during the assembly of Gondwana supercontinent.

  16. A comparison of the biological,geological events and environmental backgrounds between the Neoproterozoic-Cambrian and Permian-Triassic transitions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Neoproterozoic-Cambrian(N-C) and Permian-Triassic(P-T) transitions have been regarded the two most critical transitions in earth history because of the explosive biological radiation in the early Cambrian(the Cambrian Explosion) and the largest mass extinction at the end-Permian.Previous studies suggest that these two critical transitions showed certain comparability in major evolutionary events.In other words,a series of biological,geological,and geochemical events that had happened in the N-C transition occurred repeatedly during the P-T transition.Those events included continental re-configuration related to the deep mantle dynamics,global-scale glaciations,large C-,Sr-,and S-isotope perturbations indicating atmospheric and oceanic changes,abnormal precipitation of carbonates,and associated multiple biological radiations and mass extinctions.The coupling of those events in both N-C and P-T transitions suggests that deep mantle dynamics could be a primary mechanism driving dramatic changes of environment on the earth’s surface,which in turn caused major biological re-organizations.A detailed comparison of those events during the two critical transitions indicates that despite their general comparability,significant differences do exist in magnitude,duration,and frequency.The supercontinent Rodinia began to rift before the Snowball Earth time.By contrast,the supercontinent Pangea entered the dispersal stage after the greatest glaciation from the Late Carboniferous to Cisuralian.Quantitative data and qualitative analyses of different fossil groups show a more profound mass extinction during the N-C transition than at the end-Permian in terms of ecosystem disruption.This is indicated by the disappearance of the whole Ediacaran biota at the N-C boundary.The subsequent appearances of many new complex animals at phylum level in the early Cambrian mark the establishment of a brand new ecosystem.However,the end-Permian mass extinction is manifested mainly by the

  17. Mat-related sedimentary structures in Neoproterozoic peritidal passive margin deposits of the West African Craton (Anti-Atlas, Morocco)

    Science.gov (United States)

    Bouougri, E.; Porada, H.

    2002-11-01

    Proterozoic inliers in the central Anti-Atlas mountains expose predominantly siliciclastic sedimentary successions deposited in peritidal zones along the Neoproterozoic continental margin of the West African Craton (WAC). The low-grade metamorphic and modestly deformed sediments contain a wealth of sedimentary structures related to the former presence and activities of microbial mats and respective physicobiological processes. The well-preserved structures include wrinkle structures, erosion marks, microbial sand chips, spindle-shaped and subcircular microbial shrinkage cracks, and possibly gas domes and cabbage-head structures. Thin sections exhibit mat fragments and dispersed grains of hematite/limonite after pyrite in fine-grained quartzitic storm deposits. Post-storm layers frequently consist of matrix-supported sand-sized to silt-sized grains and are overlain by argillaceous veneers including isolated silt-sized grains and black carbonaceous laminae. The muddy veneers are considered to represent compacted stacks of microbial mats (biolaminites), which colonized and biostabilized storm and post-storm layers, and thus prevented them from eroding. In the absence of grazing and burrowing organisms and at suitable depositional and hydrodynamic conditions, it may be expected that Proterozoic microbial mats extensively grew from the supratidal to the intertidal zones and occasionally, e.g. behind protective barriers, in the subtidal zone and beyond. Mat-related structures, however, need specific conditions for their formation and preservation: Wrinkle structures, erosion marks, and microbial sand chips require tractional currents and soon deposition and burial, respectively. Such conditions are preferably met in intertidal and supratidal zones. Spindle-shaped and subcircular cracks require mat shrinkage due to either desiccation or "syneresis". Crack propagation implies progressive shrinkage, while superposition of crack generations indicates repeated alternation

  18. Deep inside a neoproterozoic intra-oceanic arc: growth, differentiation and exhumation of the Amalaoulaou complex (Gourma, Mali)

    Science.gov (United States)

    Berger, Julien; Caby, Renaud; Liégeois, Jean-Paul; Mercier, Jean-Claude C.; Demaiffe, Daniel

    2011-10-01

    We show here that the Amalaoulaou complex, in the Pan-African belt of West Africa (Gourma, Mali), corresponds to the lower and middle sections of a Neoproterozoic intra-oceanic arc. This complex records a 90-130-Ma-long evolution of magmatic inputs and differentiation above a subducting oceanic slab. Early c. 793 Ma-old metagabbros crystallised at lower crustal or uppermost mantle depths (25-30 km) and have geochemical characteristic of high-alumina basalts extracted from a depleted mantle source slightly enriched by slab-derived sedimentary components ((La/Sm)N high-Mg andesitic parental magma. Quartz and hornblende-gabbros (700-660 Ma) with composition typical of hydrous volcanic rocks from mature arcs ((La/Sm)N: 0.9-1.8; ɛNd: +4.6 to +5.2; 87Sr/86Sr: 0.7028-0.7031) were subsequently emplaced at mid-arc crust levels (~15 km). Trace element and isotopic data indicate that magmas tapped a depleted mantle source significantly more enriched in oceanic sedimentary components (0.2%). Exhumation occurred either in two stages (700-660 and 623 Ma) or in one stage (623 Ma) with a final exhumation of the arc root along cold P-T path (550°C, 6-9 kbar; epidote-amphibolite and greenschist facies conditions) during the main Pan-African collision event (620-580 Ma). The composition of magmas forming the Cryogenian Amalaoulaou arc and the processes leading to intra-arc differentiation are strikingly comparable to those observed in the deep section of exposed Mezosoic oceanic arcs, namely the Kohistan and Talkeetna complex. This evolution of the Amalaoulaou oceanic arc and its accretion towards the West African craton belong to the life and closure of the Pharusian Ocean that eventually led to the formation of the Greater Gondwana supercontinent, a similar story having occurred on the other side of the Sahara with the Mozambique Ocean.

  19. Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States

    Science.gov (United States)

    Vikre, P.G.; Poulson, S.R.; Koenig, A.E.

    2011-01-01

    The thick (???8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high d34S values (-11.6 to 40.8%, derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( 207Pb/204Pb derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources. In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in

  20. Zircon SHRIMP U-Pb ages of the "Xinghuadukou Group" in Hanjiayuanzi and Xinlin areas and the "Zhalantun Group" in Inner Mongolia, Da Hinggan Mountains

    Institute of Scientific and Technical Information of China (English)

    MIAO LaiCheng; LIU DunYi; ZHANG FuQin; FAN WeiMing; SHI YuRuo; XIE HangQiang

    2007-01-01

    A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group (Xinlin-Hanjiayuanzi area, Heilongjiang Province) and meta-volcanic rocks of the Zhalantun Group (Zhalantun district, Inner Mongolia). The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10-547±46 Ma, belonging to Early-Middle Precambrian, whereas the meta-sedimentary rocks yielded detrital zircons, with ages of 1.0-1.2, 1.6-1.8 and 2.5-2.6 Ga, indicative of deposition age at least <1.0 Ga.Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma. These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time, rather than Paleoproterozoic time as previously thought. Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons in the meta-sedimentary rocks imply that these rocks were formed proximal to older crust. It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic volcano-sedimentary sequences formed in an active continental margin setting.

  1. Neoproterozoic diamictite-bearing sedimentary rocks in the northern Yili Block and their constraints on the Precambrian evolution of microcontinents in the Western Central Asian Orogenic Belt

    Science.gov (United States)

    He, Jingwen; Zhu, Wenbin; Zheng, Bihai; Wu, Hailin; Cui, Xiang; Lu, Yuanzhi

    2015-12-01

    The origin and tectonic setting of Precambrian sequences in the Central Asian Orogenic Belt (CAOB) have been debated due to a lack of high resolution geochronological data. Answering this question is essential for the understanding of the tectonic framework and Precambrian evolution of the blocks within the CAOB. Here we reported LA-ICP-MS detrital zircon U-Pb ages and in-situ Hf isotopic data for Neoproterozoic sedimentary cover in the northern Yili Block, an important component of the CAOB, in order to provide information on possible provenance and regional tectonic evolution. A total of 271 concordant U-Pb zircon ages from Neoproterozoic sedimentary cover in the northern Yili Block define three major age populations of 1900-1400 Ma, 1300-1150 Ma and 700-580 Ma, which are quite different from cratons and microcontinents involved in the CAOB. Although it is not completely consistent with the local basement ages, an autochthonous provenance interpretation is more suitable. Some zircon grains show significant old Hf model ages (TDMC; 3.9-2.4 Ga) and reveal continental crust as old as Paleoarchean probably existed. Continuous Mesoproterozoic zircon age populations exhibit large variations in the εHf(t) ratios, suggesting the long-time involvement of both reworked ancient crust and juvenile material. Similar Mesoproterozoic evolution pattern is identified in many continental terranes involved in the CAOB that surround the Tarim Craton. Based on our analysis and published research, we postulate that the northern Yili Block, together with Chinese Central Tianshan, Kyrgyz North Tianshan and some other microcontinents surrounding the Tarim Craton, once constituted the continental margin of the Tarim Craton in the Mesoproterozoic, formed by long-lived accretionary processes. Most of the late Neoproterozoic zircons exhibit significant positive εHf(t) ratios, suggesting the addition of juvenile crust. It is consistent with the tectonic event related to the East Africa

  2. Mid-Neoproterozoic intraplate magmatism in the northern margin of the Southern Granulite Terrane, India: Constraints from geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    Science.gov (United States)

    Deeju, T. R.; Santosh, M.; Yang, Qiong-Yan; Pradeepkumar, A. P.; Shaji, E.

    2016-11-01

    The northern margin of the Southern Granulite Terrane in India hosts a number of mafic, felsic and alkaline magmatic suites proximal to major shear/paleo-suture zones and mostly represents magmatism in rift-settings. Here we investigate a suite of gabbros and granite together with intermediate (dioritic) units generated through mixing and mingling of a bimodal magmatic suite. The massive gabbro exposures represent the cumulate fraction of a basic magma whereas the granitoids represent the product of crystallization in felsic magma chambers generated through crustal melting. Diorites and dioritic gabbros mostly occur as enclaves and lenses within host granitoids resembling mafic magmatic enclaves. Geochemistry of the felsic units shows volcanic arc granite and syn-collisional granite affinity. The gabbro samples show mixed E-MORB signature and the magma might have been generated in a rift setting. The trace and REE features of the rocks show variable features of subduction zone enrichment, crustal contamination and within plate enrichment, typical of intraplate magmatism involving the melting of source components derived from both depleted mantle sources and crustal components derived from older subduction events. The zircons in all the rock types show magmatic crystallization features and high Th/U values. Their U-Pb data are concordant with no major Pb loss. The gabbroic suite yields 206Pb/238U weighted mean ages in the range of 715 ± 4-832.5 ± 5 Ma marking a major phase of mid Neoproterozoic magmatism. The diorites crystallized during 206Pb/238U weighted mean age of 724 ± 6-830 ± 2 Ma. Zircons in the granite yield 206Pb/238U weighted mean age of 823 ± 4 Ma. The age data show broadly similar age ranges for the mafic, intermediate and felsic rocks and indicate a major phase of bi-modal magmatism during mid Neoproterozoic. The zircons studied show both positive and negative εHf(t) values for the gabbros (-6.4 to 12.4), and negative values for the diorites (-7

  3. Neoproterozoic tectonic evolution of the Jebel Saghro and Bou Azzer - El Graara inliers, eastern and central Anti-Atlas, Morocco

    Science.gov (United States)

    Walsh, Gregory J.; Aleinikoff, John N.; Harrison, Richard W.; Burton, William C.; Quick, James E.; Benziane, Foudad; Yazidi, Abdelaziz; Saadane, Abderrahim

    2012-01-01

    New mapping, geochemistry, and 17 U–Pb SHRIMP zircon ages from rocks of the Sirwa, Bou Azzer–El Graara, and Jebel Saghro inliers constrain the Neoproterozoic evolution of the eastern Anti-Atlas during Pan-African orogenesis. In the Sirwa inlier, Tonian quartzite from the pre Pan-African passive margin deposits of the Mimount Formation contains detrital zircon derived entirely from the West African Craton (WAC), with most grains yielding Eburnean Paleoproterozoic ages of about 2050 Ma. Cryogenian Pan-African orogenic activity (PA1) from about 760 to 660 Ma included northward-dipping subduction to produce a volcanic arc, followed by ophiolite obduction onto the WAC. In the Bou Azzer–El Graara inlier, calc-alkaline granodiorite and quartz diorite, dated at 650–646 Ma, are syn- to post-tectonic with respect to the second period of Pan-African orogenesis (PA2), arc-continent accretion, and related greenschist facies metamorphism. Slab break-off and lithospheric delimination may have provided the source for the supra-subduction calc-alkaline plutons. At about 646 Ma, quartz diorite intruded the Tiddiline formation placing an upper limit on molassic deposition. Widespread Ediacaran high-K calc-alkaline to shoshonitic plutonism and volcanism during the final stage of Pan-African orogenesis (PA3) occurred in a setting related to either modification of the margin of the WAC or formation of a continental volcanic arc above a short-lived southward-dipping subduction zone. In the Saghro inlier, eight plutonic rocks yield ages ranging from about 588 to 556 Ma. Sampled plutonic rocks previously considered to be Cryogenian yielded Ediacaran ages. Peraluminous rhyolitic volcanic rocks in the lower part of the Ouarzazate Supergroup, including ash-flow tuffs of the Oued Dar’a caldera, yield ages between about 574 and 571 Ma. The Oued Dar’a caldera developed in a pull-apart graben produced by a left-step in a northeast-trending, left-lateral strike-slip fault zone, and

  4. Juxtaposition of Neoproterozoic units along the Baruda - Tulu Dimtu shear-belt in the East African Orogen of western Ethiopia

    Science.gov (United States)

    Braathen, A.; Grenne, Tor; Selassie, M.G.; Worku, T.

    2001-01-01

    Amalgamation of East and West Gondwanaland during the Neoproterozoic East African Orogen is recorded by several shear-belts or 'suture zones', some of which are associated with ultramafic and mafic complexes that have been interpreted as ophiolite fragments. The Baruda shear-belt is a major structure of this type that belongs to the N-S trending Barka - Tulu Dimtu zone. The significance of this zone has been studied within a transect in western Ethiopia which covers a variety of metasedimentary and metavolcanic sequences, ultramafic rocks and synkinematic intrusive complexes. All rocks participated in the regional D1 event as reflected in a penetrative steep foliation in supracrustal rocks and marginal parts of the intrusions. Highly strained rocks contain a stretching lineation that plunge to the east. The several-km thick Baruda shear-belt, comprising mylonitic supracrustal and plutonic rocks including mafic-ultramafic mega-lenses, is the most prominent expression of this event. Shear-sense indicators demonstrate top-to-the-west shear. Subsequent D2 deformation is recorded in 2-300 m wide, N-S striking, subvertical shear-zones with subhorizontal stretching lineation relatable to sinistral transcurrent movements. Our data indicate that rock units on either side of the Baruda shear-belt are related, rather than being exotic to each other as implied in suture zone models, since there is no major lithologic or metamorphic difference, geochemical data on metavolcanic rocks and pre-tectonic intrusions suggest a paleotectonic link, and style and extent of deformation is similar across the shear-belt. A tentative model for the transect suggests an arc and back-arc setting which experienced later continental collision and tectonic shortening. The initial setting was that of a shallow marine platform characterised by carbonates and sandstones, which covered extensive areas prior to break-up of a pre-existing supercontinent. Continental convergence is first recorded in high

  5. Geochronology and geochemistry of gneissic metagranites in eastern Dabie Mountains:Implications for the Neoproterozoic tectono-magmatism along the northeastern margin of the Yangtze Block

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The gneissic metagranites with Neoproterozoic protolith ages are widely exposed along the eastern margin of the Dabie ultra-high-pressure(UHP) metamorphic belt.In this paper,five representative plutons,including Huangzhen,Daba,Shima,Shuanghe,and Sanzusi,were selected for a detailed chronological and geochemical study aiming to identify the nature of the protoliths and to reveal their implications for the Neoproterozoic tectono-magmatic evolution along the northeastern margin of the Yangtze Block.These gneissic metagranites consist mainly of quartz,albite(oligoclase) and K-feldspar,and minor amphibole and biotite,as well as some metamorphic minerals due to the UHP metamorphism,such as phengite,epidote and minor kyanite and garnet.Mafic alkaline minerals(e.g.,aegirine or aegirine-augite) have been observed in some of these plutons.Zircon LA-ICP-MS U-Pb dating results indicate that the protoliths of the gneissic metagranites have been generated in Mid-Neoproterozoic(770-780 Ma),and suffered both ultrahigh-pressure metamorphism in Early Mesozoic and subsequently high-pressure eclogite-facies recrystallization at about 215 Ma.Although the gneissic metagranites generally have high SiO2 contents(70.23%-77.23%) and show metaluminous-weakly peraluminous signatures(ASI=0.90-1.05),there are still some geochemical variances between different plutons.Compared with the Sanzusi pluton,the metagranites from the Huangzhen,Daba,Shima,and Shuanghe have high K2O+Na2O contents(7.76%-9.45%),FeOtotal/(FeOtotal+MgO) ratios(0.82-0.96),HFSEs and Ga concentrations with an average 104×Ga/Al ratio up to 3.07.Combined with the features that the four plutons commonly contain aegirine-augite and have high zircon saturation temperatures(816-918°C),it is suggested that their proto-liths belong to peralkaline A-type granites.The Sanzusi pluton generally contains biotite and epidote generated from metamorphic reaction of amphibole,and is chemically enriched in calcium and depleted in potassium with

  6. Carbonatite magmatism of the southern Siberian Craton 1 Ga ago: Evidence for the beginning of breakup of Laurasia in the early Neoproterozoic

    Science.gov (United States)

    Savelieva, V. B.; Danilova, Yu. V.; Bazarova, E. P.; Ivanov, A. V.; Kamenetsky, V. S.

    2016-11-01

    Apatite and biotite from dolomite‒ankerite and calcite‒dolomite carbonatite dikes emplaced into the Paleoproterozoic metamorphic rock complex in the southern part of the Siberian Craton are dated by the U-Pb (LA-ICP-MS) and 40Ar-39Ar methods, respectively. Proceeding from the lower intercept of discordia with concordia, the age of apatite from calcite‒dolomite carbonatite is estimated to be 972 ± 21 Ma and that for apatite from dolomite‒ankerite carbonatite, as 929 ± 37 Ma. Values derived from their upper intercept have no geological sense. The ages obtained for biotite by the 40Ar-39Ar method are 965 ± 9 and 975 ± 14 Ma. It means that the formation of carbonatites reflects the earliest phases of the Neoproterozoic stage in extension of the continental lithosphere.

  7. The Bossoroca Complex, São Gabriel Terrane, Dom Feliciano Belt, southernmost Brazil: Usbnd Pb geochronology and tectonic implications for the neoproterozoic São Gabriel Arc

    Science.gov (United States)

    Gubert, Mauricio Lemos; Philipp, Ruy Paulo; Stipp Basei, Miguel Angelo

    2016-10-01

    Usbnd Pb LA-ICPMS geochronological analyses were carried out on zircon grains from metavolcanic rocks of the Bossoroca Complex and for one ash tuff of the Acampamento Velho Formation of the Camaquã Basin, in order to understand the evolution of the Neoproterozoic São Gabriel magmatic arc. A total of 42 analyses of igneous zircon grains were performed in three samples. The results yielded Usbnd Pb ages of 767.2 ± 2.9 Ma for the metavolcanic agglomerate (BOS-02); 765 ± 10 Ma for the metacrystal tuff (BOS-03) and 565.8 ± 4.8 Ma for the ash tuff (BOS-04). The Orogenic Cycle in Brazil is characterized by a set of orogenic belts consisting of petrotectonic associations juxtaposed by two collisional events that occurred at the end of the Neoproterozoic. In southern Brazil this orogeny formed the Dom Feliciano Belt, a unit composed of associations of rocks developed during two major orogenic events called São Gabriel (900-680 Ma) and Dom Feliciano (650-540 Ma). The main São Gabriel associations are tectonically juxtaposed as elongated strips according to the N20-30°E direction, bounded by ductile shear zones. The Bossoroca Complex comprises predominantly metavolcano-sedimentary rocks, characterized by medium-K calc-alkaline association generated in a cordillera-type magmatic arc. The volcanism occurred in sub-aerial environment, developing deposits generated by flow, resurgence and fall, sporadically interrupted by subaqueous epiclastic deposits, suggesting an arc related basin. The São Gabriel Terrane contains the petrotectonic units that represent the closure of the Charrua Ocean associated to the subduction period of the Brasiliano Orogenic Cycle in the Sul-rio-grandense Shield.

  8. Petrogenesis of Bir Madi Gabbro-Diorite and Tonalite-Granodiorite Intrusions in Southeastern Desert, Egypt: Implications for Tectono-Magmatic Processes at the Neoproterozoic Shield

    Directory of Open Access Journals (Sweden)

    M. A. OBEID

    2010-06-01

    Full Text Available The Neoproterozoic rocks of the Bir Madi area, south eastern desert, comprise a Metagabbro-Diorite Complex (GDC and a Tonalite-Granodiorite Suite (TGrS. The GDC has a weak tonalitic to strong calc-alkaline character and is made up of olivine gabbro, hornblende gabbro, diorite and monzodiorite. The olivine gabbro is characterized by abun-dance of augite and labradorite with pseudomorphic serpentine. The hornblende gabbro is mainly composed of horn-blende, labradorite, andesine and minor amounts of quartz with or without augite. The diorite consists essentially of andesine, hornblende, biotite and quartz. The GDC is compositionally broad, with a wide range of SiO2 (46-57 % and pronounced enrichment in the LILE (Ba and Sr relative to the HFSE (Nb, Y and Zr. The GDC rocks exhibit petrological and geochemical characteristics of arc-related mafic magmas, derived possibly from partial melting of a mantle wedge above an early Pan-African subduction zone of the Neoproterozoic Shield. The tonalite and granodiorite have a calc-alkaline affinity and show the geochemical signatures of I-type granitoids. The TGrS contains amphibolite enclaves and foliated gabbroic xenoliths. Based on the field evidence and geochemical data, the GDC and TGrS are not related to a single magma type through fractional crystallization. The presence of microgranular amphibolite enclaves in the tonalitic rocks suggest against their generation by partial melting of a mantle-derived basaltic source. The tonalitic magma originated from partial melting of an amphibolitic lower crust by anatexis process at a volcanic arc regime during construction of the Arabian-Nubian Shield. Fractional crystallization of K-feldspar and biotite gave more developed granodiorite variety from the tonalitic magma. The gabbroic xenoliths are similar in the chemical composition to the investigated metagabbros. They are incompletely digested segments from the adjacent metagabbro rocks incorporated into the

  9. Detrital zircon analysis of Mesoproterozoic and neoproterozoic metasedimentary rocks of northcentral idaho: Implications for development of the Belt-Purcell basin

    Science.gov (United States)

    Lewis, R.S.; Vervoort, J.D.; Burmester, R.F.; Oswald, P.J.

    2010-01-01

    The authors analyzed detrital zircon grains from 10 metasedimentary rock samples of the Priest River complex and three other amphibolite-facies metamorphic sequences in north-central Idaho to test the previous assignment of these rocks to the Mesoproterozoic Belt-Purcell Supergroup. Zircon grains from two samples of the Prichard Formation (lower Belt) and one sample of Cambrian quartzite were also analyzed as controls with known depositional ages. U-Pb zircon analysis by laser ablation - inductively coupled plasma - mass spectrometry reveals that 6 of the 10 samples contain multiple age populations between 1900 and 1400 Ma and a scatter of older ages, similar to results reported from the Belt- Purcell Supergroup to the north and east. Results from the Priest River metamorphic complex confirm previous correlations with the Prichard Formation. Samples from the Golden and Elk City sequences have significant numbers of 1500-1380 Ma grains, which indicates that they do not predate the Belt. Rather, they are probably from a relatively young, southwestern part of the Belt Supergroup (Lemhi subbasin). Non-North American (1610-1490 Ma) grains are rare in these rocks. Three samples of quartzite from the Syringa metamorphic sequence northwest of the Idaho batholith contain zircon grains younger than the Belt Supergroup and support a Neoproterozoic age. A single Cambrian sample has abundant 1780 Ma grains and none younger than ~1750 Ma. These results indicate that the likely protoliths of many high-grade metamorphic rocks in northern Idaho were strata of the Belt-Purcell Supergroup or overlying rocks of the Neoproterozoic Windermere Supergroup and not basement rocks.

  10. A normalised seawater strontium isotope curve. Possible implications for Neoproterozoic-Cambrian weathering rates and the further oxygenation of the Earth

    Energy Technology Data Exchange (ETDEWEB)

    Shields, G.A. [Muenster Univ. (Germany). Geologisch-Palaeontologisches Inst.

    2007-07-01

    The strontium isotope composition of seawater is strongly influenced on geological time scales by changes in the rates of continental weathering relative to ocean crust alteration. However, the potential of the seawater {sup 87}Sr/{sup 86}Sr curve to trace globally integrated chemical weathering rates has not been fully realised because ocean {sup 87}Sr/{sup 86}Sr is also influenced by the isotopic evolution of Sr sources to the ocean. A preliminary attempt is made here to normalise the seawater {sup 87}Sr/{sup 86}Sr curve to plausible trends in the {sup 87}Sr/{sup 86}Sr ratios of the three major Sr sources: carbonate dissolution, silicate weathering and submarine hydrothermal exchange. The normalised curve highlights the Neoproterozoic-Phanerozoic transition as a period of exceptionally high continental influence, indicating that this interval was characterised by a transient increase in global weathering rates and/or by the weathering of unusually radiogenic crustal rocks. Close correlation between the normalised {sup 87}Sr/{sup 86}Sr curve, a published seawater {delta}{sup 34}S curve and atmospheric pCO{sub 2} models is used here to argue that elevated chemical weathering rates were a major contributing factor to the steep rise in seawater {sup 87}Sr/{sup 86}Sr from 650 Ma to 500 Ma. Elevated weathering rates during the Neoproterozoic-Cambrian interval led to increased nutrient availability, organic burial and to the further oxygenation of Earth's surface environment. Use of normalised seawater {sup 87}Sr/{sup 86}Sr curves will, it is hoped, help to improve future geochemical models of Earth System dynamics. (orig.)

  11. Nature and evolution of Neoproterozoic ocean-continent transition: Evidence from the passive margin of the West African craton in NE Mali

    Science.gov (United States)

    Renaud, Caby

    2014-03-01

    The Timétrine massif exposed west of the Pan-African suture zone in northeastern Mali belongs to the passive margin of the West African craton facing to the east intra-oceanic arc assemblages and 730 Ma old pre-collisional calc-alkaline plutons. The Timétrine lithologic succession includes from the base to the top Mesoproterozoic cratonic to passive margin formations overlain by deep-sea Fe-Mg schists. Submarine metabasalts and two ultramafic massifs of serpentinized mantle peridotites are inserted as olistoliths towards the top whereas turbidites of continental origin represent the younger unit. Field and petrological data have revealed a distinct metasedimentary sequence attached to the serpentinized peridotites. It essentially consists of impure carbonates, Fe jaspers and polymictic breccias containing altered blocks of mantle peridotites, most rocks being enriched in detrital chromite. This association is interpreted as reworked chemical and detrital sediments derived from the alteration of mafic-ultramafic rocks. It is argued that mantle exhumation above sea floor took place during the Neoproterozoic rifting and crustal thinning period under possible tropical conditions, as suggested by the large volume of silicified serpentinites. In spite of greenschist facies metamorphic overprint characterized by widespread Fe-rich blue amphiboles that are not diagnostic of high-pressure conditions, it is possible to reconstruct a former ocean-continent transition similar to that evidenced for the Mesozoic period, followed by the deposition of syn-to post rift terrigeneous turbidites roughly coeval with ocean spreading some time before 800 Ma. It is concluded that the serpentinite massifs were tectonically emplaced first in an extensional setting, then incorporated within deep-sea sediments as olistoliths and finally transported westward during late Neoproterozoic collisional tectonics onto the West African craton.

  12. Genesis and geological significances of Neoproterozoic granitoids in the North Qinling terrain, SW Henan, China%豫西南地区北秦岭地体新元古代花岗岩类岩石成因及其地质意义

    Institute of Scientific and Technical Information of China (English)

    刘丙祥; 聂虎; 齐玥; 杨力; 祝禧艳; 陈福坤

    2013-01-01

    北秦岭地体中新元古代花岗岩类岩石是秦岭造山带的重要组成部分,记录了造山带基底前寒武纪地壳形成和演化历史.本文报道方庄和德河花岗岩岩体的锆石U-Pb年龄和O同位素组成、全岩元素和Sr-Nd同位素地球化学组成,探讨其岩石成因和地壳演化意义.结果表明,方庄花岗质糜棱岩的锆石结晶年龄为933.4±9.2Ma,δ18O值8.3‰~ 11.9‰,初始87Sr/86 Sr比值0.72455,初始εNd值-6.0,Nd模式年龄2.09Ga (tDM2);德河黑云斜长片麻岩的锆石结晶年龄为948.1±8.9Ma,初始87 Sr/86 Sr比值变化较大,初始εNd值-5.0,Nd模式年龄2.02Ga.结合已报道的新元古代花岗岩类岩体的年龄和地球化学数据,北秦岭地体新元古代岩浆作用可以划分为980 ~870Ma挤压碰撞作用和~ 844Ma伸展裂解作用两大阶段,包括~940Ma强烈变形S型同碰撞花岗岩、~ 880Ma弱-无变形后碰撞Ⅰ型花岗岩和~844Ma板内A型碱性岩三类花岗岩体.地球化学组成显示,这些花岗岩类岩石可能源自不同时期形成的秦岭群基底杂岩的部分熔融,但在后碰撞阶段幔源物质或年轻地壳物质的加入明显增加.北秦岭地体中新元古代岩浆活动与Rodinia超大陆演化基本同时代,可能记录超大陆形成过程中的地壳响应.在新元古代之前,北秦岭地体或许具有不同于华北陆块和华南陆块的演化历史.%Neoproterozoic granitoids exposed in the North Qinling terrain belong to an important part of the Qinling orogenic belt and have recorded Precambrian crustal formation and evolution of the basement of this orogenic belt.In this study,we report zircon U-Pb ages and oxygen isotopic data and whole-rock geochemical and Sr-Nd isotopic composition for the Fangzhuang and Dehe granitoid plutons,emplaced into the Qinling Group in the North Qinling terrain,and discuss petrogenesis and geological significances for crustal evolution of the basement.Analytical results show that

  13. Neoarchean-Early Paleoproterozoic and Early Neoproterozoic arc magmatism in the Lützow-Holm Complex, East Antarctica: Insights from petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    Science.gov (United States)

    Tsunogae, Toshiaki; Yang, Qiong-Yan; Santosh, M.

    2016-10-01

    The Lützow-Holm Complex (LHC) of East Antarctica forms part of the Neoproterozoic-Cambrian high-grade metamorphic segment of the East African-Antarctic Orogen. Here we present new petrological, geochemical, and zircon U-Pb and Lu-Hf isotopic data for meta-igneous rocks including charnockite, felsic gneiss, metagabbro, and mafic granulite from the LHC and evaluate the Neoarchean to Early Paleoproterozoic (ca. 2.5 Ga) and Early Neoproterozoic (ca. 1.0 Ga) arc magmatic events. The trace element geochemical signatures reveal a volcanic arc affinity for the charnockites from Sudare Rocks and Vesleknausen and felsic gneiss from Rundvågshetta, suggesting that the protoliths of these rocks were derived from felsic arc magmas. In contrast, metagabbros from Skallevikshalsen and Austhovde, occurring as boudins in metasediments, show non-arc signatures (within-plate basalt or mid-oceanic ridge basalt). The upper intercept ages of magmatic zircons in charnockite plotted on concordia diagrams yielded 2508 ± 14 Ma (Sudare Rocks) and 2490 ± 18 Ma (Vesleknausen), clearly suggesting a Neoarchean to Early Paleoproterozoic arc magmatic event. A subsequent thermal event during Early Neoproterozoic traced by 206Pb/238U age of oscillatory-zoned core of zircon in mafic granulite from Langhovde (973 ± 10 Ma) is consistent with a similar Early Neoproterozoic magmatic event reported from the LHC, suggesting a second stage of arc magmatism. The timing of peak metamorphism has been inferred from 206Pb/238U mean ages of structureless zircons in metagabbros from Skallevikshalsen and Austhovde, mafic granulite from Langhovde, and felsic gneiss from Rundvågshetta in the range of 551 ± 5.4 to 584 ± 5.0 Ma. Zircon Lu-Hf data of Neoarchean charnockites from Sudare Rocks and Vesleknausen indicate that the protolith magma was sourced from Paleo- to Neoarchean juvenile components mixed with reworked ancient crustal materials. Protolith magmatic rock of the felsic gneiss from Rundvågshetta might

  14. Hf isotope study of Palaeozoic metaigneous rocks of La pampa province and implications for the occurrence of juvenile early Neoproterozoic (Tonian) magmatism in south-central Argentina

    Science.gov (United States)

    Chernicoff, C. J.; Zappettini, E. O.; Santos, J. O. S.; Belousova, E.; McNaughton, N. J.

    2011-12-01

    On a global scale, juvenile Tonian (Early Neoproterozoic) magmatic rocks are associated with the extensional events that lead to the breakup of the Rodinia supercontinent. In Argentina, no geological record is available for this time interval, lasting from 1000 to 850 Ma. We present indirect evidence for the existence of Tonian extension in Argentina, as supported by Hf and Nd isotope determinations on Phanerozoic magmatic and sedimentary rocks. We mainly focus on our own Hf isotope determinations carried out on U-Pb SHRIMP dated zircons from Palaeozoic metaigneous rocks of La Pampa province, south-central Argentina, i.e. metagabbros of Valle Daza, dioritic orthogneiss of Estancia Lote 8, and metadiorite of Estancia El Carancho, having found that these rocks were derived from sources of ca. 920 to ca 880 Ma, with ɛHf values between +6.83 and + 9.59. Inherited zircons of this age and character identified in these rocks also point to the same source. We also compile additional Hf and Nd studies from previous work on Phanerozoic magmatic and sedimentary rocks. We preliminarily compare the age of the juvenile Tonian sources referred to in our work with that of two extensional events identified in the São Francisco craton, Brazil.

  15. The evolution of Neoproterozoic magmatism in Southernmost Brazil: shoshonitic, high-K tholeiitic and silica-saturated, sodic alkaline volcanism in post-collisional basins

    Directory of Open Access Journals (Sweden)

    Sommer Carlos A.

    2006-01-01

    Full Text Available The Neoproterozoic shoshonitic and mildly alkaline bimodal volcanism of Southernmost Brazil is represented by rock assemblages associated to sedimentary successions, deposited in strike-slip basins formed at the post-collisional stages of the Brasilian/Pan-African orogenic cycle. The best-preserved volcano sedimentary associations occur in the Camaquã and Campo Alegre Basins, respectively in the Sul-riograndense and Catarinense Shields and are outside the main shear belts or overlying the unaffected basement areas. These basins are characterized by alternation of volcanic cycles and siliciclastic sedimentation developed dominantly on a continental setting under subaerial conditions. This volcanism and the coeval plutonism evolved from high-K tholeiitic and calc-alkaline to shoshonitic and ended with a silica-saturated sodic alkaline magmatism, and its evolution were developed during at least 60 Ma. The compositional variation and evolution of post-collisional magmatism in southern Brazil are interpreted as the result mainly of melting of a heterogeneous mantle source, which includes garnet-phlogopite-bearing peridotites, veined-peridotites with abundant hydrated phases, such as amphibole, apatite and phlogopite, and eventually with the addition of an asthenospheric component. The subduction-related metasomatic character of post-collisional magmatism mantle sources in southern Brazil is put in evidence by Nb-negative anomalies and isotope features typical of EM1 sources.

  16. Geochemistry and zircon ages of mafic dikes in the South Qinling, central China: evidence for late Neoproterozoic continental rifting in the northern Yangtze block

    Science.gov (United States)

    Zhu, Xiyan; Chen, Fukun; Liu, Bingxiang; Zhang, He; Zhai, Mingguo

    2015-01-01

    Neoproterozoic volcanic-sedimentary sequences of the southern Qinling belt, central China, were intruded by voluminous mafic dikes. secondary ion mass spectrometry zircon U-Pb dating indicates that these dikes were emplaced at 650.8 ± 5.2 Ma, coeval with mafic rocks occurring at the northern margin of the Yangtze block. The dikes are characterized by enrichment of large ion lithophile elements, high Ti contents (up to 3.73 wt%) and Nb/Ta ratios between 14.5 and 19.6, suggesting a mantle source of oceanic island basalt affinity. Initial 87Sr/86Sr ratios show positive correlation with SiO2 contents and negative correlation with Zr/Nb ratios, implying that these rocks were affected by crustal contamination during the magma ascend and emplacement process. The dikes have initial ɛ Nd values of +0.2 to +3.3, low 206Pb/204Pb ratios of 16.96-17.45, and moderate 87Sr/86Sr ratios of 0.7043-0.7076, likely pointing to the involvement of an enriched mantle source. The mafic dikes and coeval mafic volcanic equivalents in the South Qinling and the northern Yangtze are hypothesized to be related with the prolonged breakup of the supercontinent Rodinia, suggesting that continental rifting lasted until ca. 650 Ma.

  17. Volcanic rock-hosted gold and base-metal mineralization associated with neoproterozoic-early Paleozoic back-arc extension in the Carolina terrane, southern Appalachian Piedmont

    Energy Technology Data Exchange (ETDEWEB)

    Feiss, P.G. (Univ. of North Carolina, Chapel Hill (United States)); Vance, R.K. (Georgia Southern Univ., Statesboro (United States)); Wesolowski, D.J. (Oak Ridge National Lab., TN (United States))

    1993-05-01

    Volcanogenic mineral deposits in the Carolina terrane, southern Appalachian Piedmont, include Kuroko-type polymetallic massive sulfide deposits and disseminated gold-pyrite deposits associated with propylitic, silicic, argillic, and advanced argillic alteration. Host rocks are metavolcaniclastic and metaepiclastic rocks of a Neoproterozoic-Early Cambrian magmatic arc. The favorable gold horizon is the transition from a lower succession of andesitic and rhyolitic pyroelastic rocks with basal mafic lavas to an upper sequence of epiclastic sedimentary units and minor lava and ash flows. Kuroko-type deposits are associated with mafic to bimodal volcanic rocks in the upper sequence. Whole-rock oxygen isotope analyses indicate that gold mineralization is associated with a transition from hydrothermal systems dominated by isotopically relatively light ([delta][sup 18]O = -6% to -10%) waters, typical of high-latitude subaerial systems, to seawater ([delta][sup 18]O = 0%). Plots of [delta][sup 18]O vs. SiO[sub 2] of the host rocks show a compositional gap associated with mineralization at the subaerial to submarine transition. Values of [delta][sup 18]O for the hydrothermal waters, lithostratigraphic analyses, and tectonic models of the Carolina terrane demonstrate that mineralization coincided with extension in a rifted arc. 34 refs., 3 figs.

  18. Geochemistry of Precambrian sedimentary rocks used to solve stratigraphical problems: An example from the Neoproterozoic Volta basin, Ghana

    DEFF Research Database (Denmark)

    Kalsbeek, F.; Frei, Robert

    2010-01-01

    units, in upward succession the Bombouaka, Oti and Obosum Groups, but poor exposure has resulted in major disagreements on stratigraphical correlations and on the areal extents of these units. Geochemical data (major and trace element concentrations as well as Rb–Sr, Pb and Sm–Nd isotope data...... anamalies, higher 87Sr/86Sr, and more negative var epsilonNd values. Geochemical distinction between samples from the Oti and Obosum Groups is ambiguous because published geological maps differ with respect to the relative extents of the Oti and Obosum Groups. Rb–Sr isotope data, combined with high degrees...

  19. Reevaluating the age of the Walden Creek Group and the kinematic evolution of the western Blue Ridge, southern Appalachians

    Science.gov (United States)

    Thigpen, J. Ryan; Hatcher, Robert D.; Kah, Linda C.; Repetski, John E.

    2016-01-01

    An integrated synthesis of existing datasets (detailed geologic mapping, geochronologic, paleontologic, geophysical) with new paleontologic and geochemical investigations of rocks previously interpreted as part of the Neoproterozoic Walden Creek Group in southeastern Tennessee suggest a necessary reevaluation of the kinematics and structural architecture of the Blue Ridge Foothills. The western Blue Ridge of Tennessee, North Carolina, and Georgia is composed of numerous northwest-directed early and late Paleozoic thrust sheets, which record pronounced variation in stratigraphic/structural architecture and timing of metamorphism. The detailed spatial, temporal, and kinematic relationships of these rocks have remained controversial. Two fault blocks that are structurally isolated between the Great Smoky and Miller Cove-Greenbrier thrust sheets, here designated the Maggies Mill and Citico thrust sheets, contain Late Ordovician-Devonian conodonts and stable isotope chemostratigraphic signatures consistent with a mid-Paleozoic age. Geochemical and paleontological analyses of Walden Creek Group rocks northwest and southeast of these two thrust sheets, however, are more consistent with a Late Neoproterozoic (550–545 Ma) depositional age. Consequently, the structural juxtaposition of mid-Paleozoic rocks within a demonstrably Neoproterozoic-Cambrian succession between the Great Smoky and Miller Cove-Greenbrier thrust sheets suggests that a simple foreland-propagating thrust sequence model is not applicable in the Blue Ridge Foothills. We propose that these younger rocks were deposited landward of the Ocoee Supergroup, and were subsequently plucked from the Great Smoky fault footwall as a horse, and breached through the Great Smoky thrust sheet during Alleghanian emplacement of that structure.

  20. Lead isotope evidence for recent uranium mobility in geological formations of Brazil: implications for radioactive waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Iyer, S.S. [Department of Physics and Astronomy, University of Calgary, Calgary (Canada); Babinski, M. [Instituto de Geociencias, Universidade de Sao Paulo, Sao Paulo (Brazil); Marinho, M.M. [Companhia Baiana de Pesquisa Mineral (CBPM), Salvador (Brazil); Barbosa, J.S.F. [Instituto de Geociencias, Universidade Federal da Bahia, Salvador (Brazil); Sato, I.M.; Salvador, V.L. [Instituto de Pesquisas Energeticas e Nucleares (CNEN/SP), Sao Paulo (Brazil)

    1999-03-01

    Lead-lead isotope data from whole rock samples are used to investigate the recent (last few million years) mobility of U and Th. The method is based on the comparison of the calculated present day U and Th concentrations required to yield the Pb isotope composition in the samples with the actual present day concentrations of U and Th obtained by direct measurement. The geological formations studied include the Neoproterozoic carbonate sediments of the Bambui Group, Archean/Paleoproterozoic granite-greenstone terrain of the Contendas-Mirante Complex and a Proterozoic ortho-gneisses hosting U deposit in Lagoa Real. All these formations are in the Sao Francisco Craton, Brazil. The data show high U mobility in the carbonate sediments and in the deformed ortho-gneisses set in a ductile shear zone. Infiltration of groundwater through fault zones seems to have facilitated the U mobility. The Pb isotope approach is a useful technique complementing U-series disequilibrium studies and may be included for site characterization studies for radioactive waste disposal. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  1. Petrology and SHRIMP zircon geochronology of granulites from Vesleknausen, Lützow-Holm Complex, East Antarctica:Neoarchean magmatism and Neoproterozoic high-grade metamorphism

    Institute of Scientific and Technical Information of China (English)

    Toshiaki Tsunogae; Daniel J. Dunkley; Kenji Horie; Takahiro Endo; Tomoharu Miyamoto; Mutsumi Kato

    2014-01-01

    We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the Lützow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 ?C, approximately 150 ?C lower than those estimated for met-asedimentary gneisses from Rundvågshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ? 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundvågshetta-Vesleknausen-Strandnibba region in southwestern Lützow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc mag-matism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern Lützow-Holm Bay) by subduction/collision events during the as-sembly of Gondwana supercontinent, and subsequently underwent w850 ?C granulite-facies meta-morphosed during Neoproterozoic to Cambrian final collisional event.

  2. Petrology and SHRIMP zircon geochronology of granulites from Vesleknausen, Lützow-Holm Complex, East Antarctica: Neoarchean magmatism and Neoproterozoic high-grade metamorphism

    Directory of Open Access Journals (Sweden)

    Toshiaki Tsunogae

    2014-03-01

    Full Text Available We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the Lützow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss, mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750–850 °C, approximately 150 °C lower than those estimated for metasedimentary gneisses from Rundvågshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ± 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundvågshetta-Vesleknausen-Strandnibba region in southwestern Lützow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc magmatism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern Lützow-Holm Bay by subduction/collision events during the assembly of Gondwana supercontinent, and subsequently underwent ∼850 °C granulite-facies metamorphosed during Neoproterozoic to Cambrian final collisional event.

  3. U-Pb zircon geochronology, petrochemical and Sr-Nd isotopic characteristic of Late Neoproterozoic granitoid of the Bornaward Complex (Bardaskan-NE Iran)

    Science.gov (United States)

    Bagherzadeh, R. Monazzami; Karimpour, M. H.; Farmer, G. Lang; Stern, C. R.; Santos, J. F.; Rahimi, B.; Heidarian Shahri, M. R.

    2015-11-01

    The Bornaward Granitoid Complex (BGC) in the Taknar Zone is located in the northeast of Central Iranian Block. The BGC consists of granite, alkaligranite, syenogranite, leucogranite, granophyre, monzogranite, granodiorite, tonalite and diorite that have intruded into the center of Taknar Zone. These intrusive rocks affected by low grade metamorphism. Because of there are no reliable isotope dating data, for the Bornaward Granitoid Complex rocks have been proposed discordant ages (Jurassic, Cretaceous or even younger ages) by many studies. In the present study, new isotopic information based on zircon U-Pb dating has revealed the origin and time of the formation of the BGC. These new results do not confirm previously proposed ages. The results obtained from zircon U-Pb dating of the BGC rocks suggest late-Neoproterozoic (Precambrian) age (540-550 Ma). The Bornaward Granitoid Complex is middle-high metaluminous to lower-middle peraluminous and belongs to tholeiite, calc-alkaline to high-K calc-alkaline rock series with enrichment in LIL (Cs, Rb and Ba, U, K, Zr, Y, Th) and depletion in HIL (Sr and Nb, Ta, Ti) elements. Chondrite-normalized Rare Earth Elements (REE) plots indicate minor enrichment of LREE compared to HREE, and strong negative anomaly of Eu compared to other Rare Earth Elements. Furthermore, initial 87Sr/86Sr and 143Nd/144Nd range from 0.70351 to 0.71689 and 0.511585 to 0.512061, respectively, and initial εNd isotope values for granite, granodiorite and diorite range from -6.73 to 2.52. These all indicate that the BGC has derived from partial melting of distinct basement source regions with very high initial 87Sr/86Sr and undergoing extensive crustal contamination (S-type granite).

  4. Redox condition of the late Neoproterozoic pelagic deep ocean: 57Fe Mössbauer analyses of pelagic mudstones in the Ediacaran accretionary complex, Wales, UK

    Science.gov (United States)

    Sato, Tomohiko; Sawaki, Yusuke; Asanuma, Hisashi; Fujisaki, Wataru; Okada, Yoshihiro; Maruyama, Shigenori; Isozaki, Yukio; Shozugawa, Katsumi; Matsuo, Motoyuki; Windley, Brian F.

    2015-11-01

    We report geological and geochemical analysis of Neoproterozoic pelagic deep-sea mudstones in an accretionary complex in Lleyn, Wales, UK. Ocean plate stratigraphy at Porth Felen, NW Lleyn, consists of mid-ocean ridge basalt (> 4 m), bedded dolostone (2 m), black mudstone (5 m), hemipelagic siliceous mudstone (1 m,) and turbiditic sandstone (15 m), in ascending order. The absence of terrigenous clastics confirms that the black and siliceous mudstone was deposited in a pelagic deep-sea. Based on the youngest U-Pb age (564 Ma) of detrital zircons separated from overlying sandstone, the deep-sea black mudstone was deposited in the late Ediacaran. The 5 m-thick black mudstone contains the following distinctive lithologies: (i) black mudstone with thin pyritic layers (0.8 m), (ii) alternation of black mudstone and gray/dark gray siliceous mudstone (2.4 m), (iii) thinly-laminated dark gray shale (1 m), and (iv) black mudstone with thin pyritic layers (1 m). 57Fe Mössbauer spectroscopy confirms that these black mudstones contain pyrite without hematite. In contrast, red bedded claystones (no younger than 542 Ma) in the neighboring Braich section contain hematite as their main iron mineral. These deep-sea mudstones in the Lleyn Peninsula record a change of redox condition on the pelagic deep-sea floor during the Ediacaran. The black mudstone at Porth Felen shows that deep-sea anoxia existed in the late Ediacaran. The eventual change from a reducing to an oxidizing deep-sea environment likely occurred in the late Ediacaran (ca. 564-542 Ma).

  5. U-Pb (LA-PIMMS) Ages of Inherited Zircons from Early Palaeozoic Granitoids of the W Sudetes, N Bohemian Massif, Central Europe: Implications for Neoproterozoic Continental Reconstructions

    Science.gov (United States)

    Crowley, Q. G.; Patocka, F.; Kachlík, V.

    2003-04-01

    A U-Pb laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS) geochronological study of zircons from early Palaeozoic (meta)granitoids of the Czech W Sudetes (E Saxothuringian Zone), NW Bohemian Massif, was carried out in order to determine the range of inherited age spectra preserved in these lithologies. Backscattered SEM images indicate that many zircons have distinct cores and rims. The majority of inherited zircon components yield concordant U-Pb ages that fall into the following age ranges: (1) 520-770 Ma, (2) 1.9-2.2 Ga and (3) ca. 3.0 Ga. These three age populations are typical of the W African Craton and the Armorican Terrane Assemblage of Europe. The age spectra correspond to Cadomian, Birimian / Icartian / Eburnean / Burkinian and Leonian events respectively. Some previous Pb-Pb zircon and whole rock Nd studies of similar lithologies from the W Sudetes (e.g. Hegner &Kröner, 2000) have attributed the presence of Mesoproterozoic 207Pb/206Pb ages to a peri-Amazonian provenance. Although some zircons from this study have yielded apparent Mesoproterozoic ages, they are discordant and can be resolved into early Palaeozoic to Neoproterozoic lower intercept and Palaeoproterozoic to Archaean upper intercept components. This unequivocally proves that an inherited Grenvillian component does not exist in these lithologies. We therefore favour derivation of the Saxothuringian zone and associated members of the Armorican Terrane Assemblage from a W African Craton Gondwanan setting. References: Hegner, E, &Kröner, A. 2000. Review of Nd data and xenocrystic and detrital ages from the pre-Variscan basement in the Eastern Bohemian Massif: speculations on palinspastic reconstructions. In: Franke, W., Altherr, R., Haak, V. &Oncken, O. (eds.), Orogenic Processes: Quantification and Modelling in the Variscan Belt of Central Europe Geological Society of London Special Publication, 179, 113-129.

  6. Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation:A case study from the Neoproterozoic Doushantuo Formation,Guizhou Province,South China

    Institute of Scientific and Technical Information of China (English)

    LING Hongfei; JIANG Shaoyong; FENG Hongzhen; CHEN Yongquan; CHEN Jianhua; YANG Jinghong

    2004-01-01

    The Neoproterozoic Doushantuo Formation at Weng'an in Guizhou Province of South China consists of phosphorites and dolomites.Three types of samples are recongnized for the phosphate-bearing rocks.In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin.The Type II samples are interbedded phosphorites and dolomites.Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed.Phosphates of Type I and II samples show similar low δ18Ophos (SMOW) values of 10.9‰~12.1‰ and 10.7‰~12.8‰, respectively, whereas Type III phosphates show higher δ18Ophos (SMOW) values of 13.2‰~15.0‰.Dolomites from Type I and II samples have δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -6.2‰~-3.4‰ and -2.2‰~-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -12.9‰~-8.6‰ and -4.4‰~-2.6‰.Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater.Calculations of palaeocean temperatures from the most 18O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period.Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng'an, Guizhou Province.

  7. Time span of plutonism, fabric development, and cooling in a Neoproterozoic magmatic arc segment: U Pb age constraints from syn-tectonic plutons, Sark, Channel Islands, UK

    Science.gov (United States)

    Miller, Brent V.; Samson, Scott D.; D'Lemos, Richard S.

    1999-10-01

    New U-Pb zircon and titanite dates from syn-tectonic plutons on the British Channel Island of Sark constrain the time span of plutonism, fabric development, and cooling in this part of the Neoproterozoic Cadomian magmatic arc. The Tintageu leucogneiss is a mylonitic unit that was dated previously at 615.6 +4.2-2.3 Ma. The Port du Moulin quartz diorite, which intruded the Tintageu unit, contains a high-strain solid-state deformation fabric that is less intense than, but parallel to, fabrics in the leucogneiss and yields a U-Pb zircon date of 613.5 +2.3-1.5 Ma. The Little Sark quartz diorite also displays solid-state deformation fabrics in addition to relict magmatic textures, and yields a U-Pb zircon date of 611.4 +2.1-1.3 Ma. The North Sark granodiorite is largely penetratively undeformed, exhibits mainly magmatic fabrics and textures and has a U-Pb zircon date of 608.7 +1.1-1.0 Ma. Two fractions of titanite from each intrusion are essentially concordant and are identical within error, with mean dates of 606.5±0.4 Ma (Port du Moulin quartz diorite), 606.2±0.6 Ma (Little Sark quartz diorite), 606.4±0.6 Ma (North Sark granodiorite). The new U-Pb data, in combination with previous U-Pb and 40Ar/ 39Ar data and previous field studies, confirm the syn-tectonic nature of the Sark plutons and quantify the time span (ca. 7 m.y.) required for intrusion and sufficient crystallization of each body to record incremental strain during waning deformation. Titanite U-Pb and hornblende 40Ar/ 39Ar dates mark final cooling about 2 m.y. after intrusion of the last pluton.

  8. Detrital mineral chronology of the Uinta Mountain Group: Implications for the Grenville flood in southwestern Laurentia

    Science.gov (United States)

    Mueller, P.A.; Foster, D.A.; Mogk, D.W.; Wooden, J.L.; Kamenov, George D.; Vogl, J.J.

    2007-01-01

    Numerous studies have shown that large quantities of Grenville-age detritus dominate Neo-proterozoic to Cambrian arenites in southwest Laurentia (southwestern United States). U-Pb ages and Hf isotopic compositions of zircons and 40Ar/39Ar ages of white mica from clastic sedimentary rocks of the Neoproterozoic Uinta Mountain Group also indicate significant Mesoproterozoic detritus mixed with a variably abundant Archean component. Zircons with ages representative of the Paleoproterozoic basement in the eastern Uinta Mountains or the younger Paleoproterozoic rocks of the adjacent Yavapai-Mazatzal terranes were not observed. A limited range of initial ??Hf (???90% between -3 and +3) for Mesoproterozoic zircons suggests derivation from a source region (or regions) characterized by mixing between juvenile and reworked older crust during Grenville orogenesis. The enriched Grenville-age basement proposed to underlie much of southeastern North America may be this source based on similarities of Hf isotopic data from Mesoproterozoic zircons in Mississippi River sand and available paleocurrent data. If so, then disruption of this supply in the Cambrian may be related to Iapetan rifting and, perhaps, the separation of the Precordillera terrane from Laurentia. ?? 2007 The Geological Society of America.

  9. Neoproterozoic-middle Paleozoic tectono-magmatic evolution of the Gorny Altai terrane, northwest of the Central Asian Orogenic Belt: Constraints from detrital zircon U-Pb and Hf-isotope studies

    Science.gov (United States)

    Chen, Ming; Sun, Min; Buslov, Mikhail M.; Cai, Keda; Zhao, Guochun; Zheng, Jianping; Rubanova, Elena S.; Voytishek, Elena E.

    2015-09-01

    The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U-Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1-1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530-464 Ma grains, followed by a subordinate group of 641-549 Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555-456 Ma and 525-463 Ma, respectively), but a significant amount of additional 2431-772 Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk-Altai intra-oceanic island arc served as a unitary source for the Cambrian-Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640-540 Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530-470 Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk-Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530-470 Ma detrital zircons are almost exclusively featured by positive εHf(t) values and have two-stage Hf model ages of ca. 1.40-0.45 Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk-Altai arc made a

  10. Group X

    Energy Technology Data Exchange (ETDEWEB)

    Fields, Susannah

    2007-08-16

    This project is currently under contract for research through the Department of Homeland Security until 2011. The group I was responsible for studying has to remain confidential so as not to affect the current project. All dates, reference links and authors, and other distinguishing characteristics of the original group have been removed from this report. All references to the name of this group or the individual splinter groups has been changed to 'Group X'. I have been collecting texts from a variety of sources intended for the use of recruiting and radicalizing members for Group X splinter groups for the purpose of researching the motivation and intent of leaders of those groups and their influence over the likelihood of group radicalization. This work included visiting many Group X websites to find information on splinter group leaders and finding their statements to new and old members. This proved difficult because the splinter groups of Group X are united in beliefs, but differ in public opinion. They are eager to tear each other down, prove their superiority, and yet remain anonymous. After a few weeks of intense searching, a list of eight recruiting texts and eight radicalizing texts from a variety of Group X leaders were compiled.

  11. P-T-t path of metamorphism for the Julin Group and its geodynamical implications in Yuanmou, Yunnan

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The metamorphic complex of the Julin Group occurs in the Yuanmou area of Yunnan Province on the western margin of the Yangtze Platform, and connects with the Kangdian metamorphic complex to the north. Based on the detailed petrographic observations and studies of garnet growth zoning, a P-T-t path has been reconstructed for the staurolite-kyanite zone in the Julin Group. This path is characterized by (1) a counter-clockwise evolutional trend, (2) a quicker increase of temperature than that of pressure in the initial prograde metamorphism, but slower near the peak, then temperature and pressure simultaneously reaching the peak metamorphic conditions, and (3) a slow near-isobaric cooling during the retrograde process. The P-T-t path for prograde metamorphism is closely related to magmatic accretion in the arc setting. The magmatic accretion model, metamorphism type and tectonic setting may be compared with the global Grenville tectono-metamorphic events, and related to the assembly of the Rodinia at the late Meso-proterozoic-early Neoproterozoic (~1.0 Ga). The retrograde P-T-t path shows a slow near-isobaric cooling, indicating sustained heat supplies from the upper mantle and no rapid erosion. This heat source may be originated from the Neoproterozoic (~0.82 Ga) breakup of the Rodinia.

  12. Stable isotopes of oxygen and carbon compositions in the Neoproterozoic of South Gabon (Schisto-Calcaire Subgroup, Nyanga Basin): Are cap carbonates and lithoherms recording a particular destabilization event after the Marinoan glaciation?

    Science.gov (United States)

    Préat, Alain; Prian, Jean-Pierre; Thiéblemont, Denis; Obame, Rolf Mabicka; Delpomdor, Franck

    2011-06-01

    Geologic evidence of tropical sea level glaciation in the Neoproterozoic remains a matter of debate in the Snowball Earth hypothesis. The Niari Tillite Formation and the cap carbonates record the late Neoproterozoic Marinoan glaciation in South Gabon. These cap carbonates are located at the base of the Schisto-Calcaire Subgroup a predominantly carbonate succession that rests with sharp contact on top of the Niari Tillite. Integrating sedimentological and stable isotope data, a consistent sequence of precipitation events is proposed, with strongly negative δ 13C values pointing to a particular event in the cap carbonates (average δ 13C value = -3.2‰ V-PDB) and in a further newly defined lithohermal unit (average δ 13C value = -4.6‰ V-PDB). Subsequent shallow evaporitive platform carbonates display carbon and oxygen isotopic compositions indicative of relatively unaltered seawater values. Strongly negative δ 18O values in the lithoherms and replacement of aragonite fans by equigranular calcite suggest flushing of meteoric water derived from glacial meltwater.

  13. Group morphology

    NARCIS (Netherlands)

    Roerdink, Jos B.T.M.

    2000-01-01

    In its original form, mathematical morphology is a theory of binary image transformations which are invariant under the group of Euclidean translations. This paper surveys and extends constructions of morphological operators which are invariant under a more general group TT, such as the motion group

  14. Neoproterozoic anorogenic magmatism in the Southern Bahia Alkaline Province of NE Brazil: U-Pb and Pb-Pb ages of the blue sodalite syenites

    Science.gov (United States)

    Rosa, Maria de Lourdes da Silva; Conceição, Herbet; Macambira, Moacir José Buenano; Galarza, Marco Antonio; Cunha, Mônica Pringsheim; Menezes, Rita Cunha Leal; Marinho, Moacyr Moura; Filho, Basílio Elesbão da Cruz; Rios, Débora Correia

    2007-08-01

    Blue sodalite syenite is a rare rock, and the Southern Bahia Alkaline Province (SBAP) is the only place in Brazil where economic deposits are found. This province forms part of the Archaean to Paleoproterozoic São Francisco craton, and contains a few batholiths, a large number of stocks and hundreds of dykes. Its southern part lies close to the tectonic contact between the craton and the Neoproterozoic Araçuaí mobile melt. Blue sodalite-bearing syenites are found in almost all the igneous bodies of the SBAP as dykes or pegmatitic masses hosted by nepheline syenite. Economically viable quantities for the production of dimension stones are found only in the Floresta Azul alkaline complex, the Itaju do Colônia and Rio Pardo stocks and the Itarantim batholith.U-Pb ages obtained for titanite from Itaju do Colônia (732 ± 8 Ma) and Rio Pardo (714 ± 8) and Pb-Pb evaporation ages of zircon from Floresta Azul (696 ± 3 Ma) and Itarantim (722 ± 5 Ma). The geochronology of the SBAP shows that the anorogenic alkaline magmatism persisted for at least 58 Ma, demonstrating an extensional tectonic environment in the southern part of the São Francisco craton at this time. The data show that the rift phase which preceded the formation of the Araçuaí orogen was active until at least 700 Ma. The reported ages are similar to those found for the nepheline syenite host bodies, which supports the conclusions of the previous petrologic study demonstrating that blue sodalite is formed during the crystallization of these bodies. Two different processes are involved. In the magmatic process, sodalite occurs as disseminated and interstitial crystals among alkali feldspar crystals, and is associated with calcite and cancrinite formed by destabilization of nepheline. In the metasomatic process, discontinuous bands of sodalite are in sharp contact with nepheline syenite pegmatite, and its crystal aggregates often contain relict textures of nepheline and albite been replaced by sodalite.

  15. Sources of granite magmatism in the Embu Terrane (Ribeira Belt, Brazil): Neoproterozoic crust recycling constrained by elemental and isotope (Sr-Nd-Pb) geochemistry

    Science.gov (United States)

    Alves, Adriana; Janasi, Valdecir de Assis; Campos Neto, Mario da Costa

    2016-07-01

    Whole rock elemental and Sr-Nd isotope geochemistry and in situ K-feldspar Pb isotope geochemistry were used to identify the sources involved in the genesis of Neoproterozoic granites from the Embu Terrane, Ribeira Belt, SE Brazil. Granite magmatism spanned over 200 Ma (810-580 Ma), and is dominated by crust-derived relatively low-T (850-750 °C, zircon saturation) biotite granites to biotite-muscovite granites. Two Cryogenian plutons show the least negative εNdt (-8 to -10) and highest mg# (30-40) of the whole set. Their compositions are strongly contrasted, implying distinct sources for the peraluminous (ASI ∼ 1.2) ∼660 Ma Serra do Quebra-Cangalha batholith (metasedimentary rocks from relatively young upper crust with high Rb/Sr and low Th/U) and the metaluminous (ASI = 0.96-1.00) ∼ 630 Ma Santa Catarina Granite. Although not typical, the geochemical signature of these granites may reflect a continental margin arc environment, and they could be products of a prolonged period of oceanic plate consumption started at ∼810 Ma. The predominant Ediacaran (595-580 Ma) plutons have a spread of compositions from biotite granites with SiO2 as low as ∼65% (e.g., Itapeti, Mauá, Sabaúna and Lagoinha granites) to fractionated muscovite granites (Mogi das Cruzes, Santa Branca and Guacuri granites; up to ∼75% SiO2). εNdT are characteristically negative (-12 to -18), with corresponding Nd TDM indicating sources with Paleoproterozoic mean crustal ages (2.0-2.5 Ga). The Guacuri and Santa Branca muscovite granites have the more negative εNdt, highest 87Sr/86Srt (0.714-0.717) and lowest 208Pb/206Pb and 207Pb/206Pb, consistent with an old metasedimentary source with low time-integrated Rb/Sr. However, a positive Nd-Sr isotope correlation is suggested by data from the other granites, and would be consistent with mixing between an older source predominant in the Mauá granite and a younger, high Rb/Sr source that is more abundant in the Lagoinha granite sample. The

  16. Group devaluation and group identification

    NARCIS (Netherlands)

    Leach, C.W.; Rodriguez Mosquera, P.M.; Vliek, M.L.W.; Hirt, E.

    2010-01-01

    In three studies, we showed that increased in-group identification after (perceived or actual) group devaluation is an assertion of a (preexisting) positive social identity that counters the negative social identity implied in societal devaluation. Two studies with real-world groups used order manip

  17. Geochemical characteristics of Bikou volcanic group and Sr-Nd-Pb isotopic composition: Evidence for breakup event in the north margin of Yangtze plate, Jining era

    Institute of Scientific and Technical Information of China (English)

    LI; YongFei; LAI; ShaoCong; QIN; JiangFeng; LIU; Xin; WANG; Juan

    2007-01-01

    The geodynamic setting of the Bikou volcanic group is a critical question to trace the Precambrain tectonic framework and evolution for the Yangtze plate. This study has suggested that the Bikou volcanic group is composed of several residual oceanic crust units: MORB (mid-ocean ridge basalt), Alk-OIB (alkaline ocean island basalt) and Th-OIB (tholeiitic ocean island basalt) as well as subduction-related volcanic rocks. According to field observation, those distinct rocks occurred collectively in form of tectonic contact, implying that the Bikou volcanic group was an ophiolitic mélange. Coupled with geochronological data, a perished oceanic basin at the northern margin of the Yangtze block during Neoproterozoic was tested by this ophiolitic mélange. Meanwhile, the isogeochemical data suggest that the ocean occurred in the Southern Hemisphere identical to Indian, South Atlantic and South Pacific oceans in terms of their Dupal anomalies, and the original source of the rocks could be probably mixing by EMⅠand EMⅡ component caused by dehydration melting of subducting oceanic crust during subduction process. On the basis of geochemical characteristics of the studied rocks, the Bikou volcanic group could imply that a partial breakup event occurred in the northern margin of Yangtze plate during the Neoproterozoic era.

  18. Record and time of Neoproterozoic glaciations on Earth%全球新元古代冰期的记录和时限

    Institute of Scientific and Technical Information of China (English)

    赵彦彦; 郑永飞

    2011-01-01

    新元古代时期,地球上出现了几次大规模的大洋型和大陆型冰川事件.但是,由于新元古界地层缺少有利的冰期沉积对比标志,因此对这些冰川事件的期次、开始和结束时间、全球化程度等仍然存在较大争议.冰期沉积物的成分、结构和构造是认识古冰川活动遗迹的重要地质证据,化学沉积地层的碳同位素漂移是识别冰期的常用地球化学代理指标,岩石和矿物氧同位素的极端值已经成为古大陆冰川活动的新兴地球化学代理指标.新元古代的地层年龄、岩石学和同位素地球化学特征指示了当时全球总共发育4次冰期,其中两次属于大洋型冰川,分别称为Sturtian冰期(718~660Ma)和Marinoan冰期(651~635Ma).其中Marinoan冰期的全球化程度最高,对应于通常所说的"雪球地球事件".Sturtian冰期可能属于滨海相-大陆边缘相沉积,其沉积物主要在海洋到大陆边缘的过渡地区发育.在这两期大洋型冰川之前和之后存在局部的大陆/山岳型冰川,其中Sturtian期之前的称为Kaigas冰期(757~741Ma),而Marinoan冰期之后的称之为Gaskiers冰期(583.7~582.1Ma).尽管中国华南地区缺少这两次大陆型冰川的沉积记录,但是岩石和矿物的稳定同位素异常提供了这两次大陆型冰川曾经存在过的地球化学证据.因此,地质学和地球化学证据都可以用来追溯地质历史上的冰川事件.%Several serious glaciations of oceanic and continental origins occurred on Earth in the Neoproterozoic Period. However, there are hot debates on the number, time and extent of these glaciations due to the relative lack of robust indicators for glacial deposits. Sedimentary records such as the components, facies and structures of diamictites are the most important observations to substantiate the presence of glaciation. Carbon isotopic excursions in associated carbonates have been used to suggest the possible existence of glacial

  19. Group Grammar

    Science.gov (United States)

    Adams, Karen

    2015-01-01

    In this article Karen Adams demonstrates how to incorporate group grammar techniques into a classroom activity. In the activity, students practice using the target grammar to do something they naturally enjoy: learning about each other.

  20. MUYANG GROUP

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ With its headquarters in the historic city of Yangzhou,Jiangsu Muyang Group Co.,Ltd has since its founding in 1967 grown into a well-known group corporation whose activities cover research&development.project design,manufacturing,installation and services in a multitude of industries including feed machinery and engineering,storage engineering,grain machinery and engineering,environmental protection,conveying equipment and automatic control systems.

  1. Abelian groups

    CERN Document Server

    Fuchs, László

    2015-01-01

    Written by one of the subject’s foremost experts, this book focuses on the central developments and modern methods of the advanced theory of abelian groups, while remaining accessible, as an introduction and reference, to the non-specialist. It provides a coherent source for results scattered throughout the research literature with lots of new proofs. The presentation highlights major trends that have radically changed the modern character of the subject, in particular, the use of homological methods in the structure theory of various classes of abelian groups, and the use of advanced set-theoretical methods in the study of undecidability problems. The treatment of the latter trend includes Shelah’s seminal work on the undecidability in ZFC of Whitehead’s Problem; while the treatment of the former trend includes an extensive (but non-exhaustive) study of p-groups, torsion-free groups, mixed groups, and important classes of groups arising from ring theory. To prepare the reader to tackle these topics, th...

  2. Timing of maturation of a Neoproterozoic oceanic arc during Pan-African Orogeny: the Asmlil complex (Anti-Atlas, South Morocco)

    Science.gov (United States)

    Triantafyllou, Antoine; Berger, Julien; Baele, Jean-Marc; Bruguier, Olivier; Diot, Hervé; Ennih, Nasser; Plissart, Gaëlle; Monnier, Christophe; Watlet, Arnaud; Vandycke, Sara

    2016-04-01

    Many intra-oceanic paleo-arcs are exposed in the Pan-African belt surrounding the West African Craton. In the Moroccan Anti-Atlas, remnants of Intra-Oceanic Subduction Zone (IOSZ) are preserved in few erosional windows moulded along the Anti-Atlas Major fault. These complexes highlight a Neoproterozoic paleo-suture made of 760 My back-arc ophiolites thrusted to the south onto a dismembered band of oceanic arc relics. The Asmlil arc complex, located in the southern part of the Bou Azzer inlier, is made of (i) 755 to 745 My- intermediate banded gneiss interpreted as metavolcanic products of a juvenile oceanic arc. This latter has been intruded by (ii) medium-grained hornblende-gabbro and dioritic magmas, in turn intruded by (iii) medium- to coarse grained hornblenditic-granodioritic decametric intrusions under sub-magmatic HT conditions. Hornblende-gabbros are made of garnet + amphibole/cpx relics + epidote + rutile paragenesis. Calculated pseudosections yielded P ~ 11-12 kbar for T ranging between 600 and 720°C for garnet growth. Measured Zr-in-rutile thermometer gave slightly higher temperature ranging between 710-790°C. On the field, garnet-rich leucocratic veinlets suggest that moderate partial melting of the mafic rock or localized dehydration reactions took place under garnet-granulite conditions (>800°C for hydrated chemical system). New geochronological data on garnet-bearing leucogabbros constrain their emplacement at 700 ±7 My (U-Pb zircon with low Th/U age (age of 654 ±7 My (U-Pb method on rutile). Geochemical data of each mafic and ultramafic facies (hornblende gabbro, garnet-bearing facies and hornblendite) show typical arc signature (marked by e.g. Nb-Ta anomaly, (La/Sm)N: 0.8-1.6 ; (Nb/La) < 0.46 ; high Nb/Ba ratio ; 0.4 < K2O < 2.1 wt%). Intrusive granodioritic magmas show depleted HREE trend similar to granitoids in the Kohistan paleo-arc. Melting modeling suggests they are produced by partial melting of a REE-depleted gabbronorite with cpx

  3. Neoproterozoic chromite-bearing high-Mg diorites in the western part of the Jiangnan orogen, southern China: Geochemistry, petrogenesis and tectonic implications

    Science.gov (United States)

    Chen, Xin; Wang, Di; Wang, Xiao-Lei; Gao, Jian-Feng; Shu, Xu-Jie; Zhou, Jin-Cheng; Qi, Liang

    2014-07-01

    -stage model for the petrogenesis of the high-Mg diorites: 1) the mantle source was firstly metasomatized by melts from partial melting of subducting terrigenous sediments to form the enriched Nd-Hf isotopic characteristics; and then 2) the mantle-derived high-Mg mafic melts mixed with the crust-derived low-Mg granitic melts to form the high-Mg diorites and medium-Mg granodiorites. The occurrence of high-Mg diorites implies the existence of Neoproterozoic subduction-related metasomatism in the western part of the Jiangnan orogen.

  4. C- and Sr-isotope stratigraphy of the São Caetano complex, Northeastern Brazil: a contribution to the study of the Meso-Neoproterozoic seawater geochemistry

    Directory of Open Access Journals (Sweden)

    Juan C. Silva

    2005-03-01

    Full Text Available C-isotope and 87Sr/86Sr values for five carbonate successions from the São Caetano Complex, northeastern Brazil, were used to constrain their depositional age and to determine large variations in the C- and Sr-isotopic composition of seawater under the framework of global tectonic events. Three C-isotope stages were identified from base to top in a composed chemostratigraphic section: (1 stage in which delta13C values vary from +2 to +3.7‰ PDB and average 3‰ PDB, (2 stage with delta13C values displaying stronger oscillations (from -2‰ to +‰ PDB, and (3 stage with an isotopic plateau with values around +3.7‰ PDB. Constant 87Sr/86Sr values (~ 0.70600 characterize C-isotope stage 1, whereas slightly fluctuating values (from 0.70600 to 0.70700 characterize C-isotope stage 2. Finally, 87Sr/86Sr values averaging 0.70600 characterize C-isotope stage 3. The C- and Sr- chemostratigraphic pathways permit to state: (a the C- and Sr-isotope secular curves registered primary fluctuations of the isotope composition of seawater during late Mesoproterozoic- early Neoproterozoic transition in the Borborema Province, and (b onset of the Cariris Velhos/Greenville cycle, widespread oceanic rifting, continental magmatic arc formation and onset of the agglutination of Rodinia supercontinent, mostly controlled the C- and Sr-isotope composition of seawater during the C-isotope stages 1, 2 and 3.Valores de isótopos de C e 87Sr/86Sr de cinco seqüências de carbonatos do Complexo São Caetano, nordeste do Brasil; foram usados para estimar a sua idade de deposição e relacionar variações da composição isotópica na água do mar com eventos tectônicos globais. Três estágios de variação de isótopos de carbono foram identificados de base para o topo numa seção quimioestratigráfica composta: (1 estágio em que delta13C varia de +2 a +3.7‰PDB (media 3‰PDB, (2 estágio no qual delta13C varia consideravelmente (de -2 a +3‰PDB e (3 est

  5. Molar-tooth Carbonate Sequences and Sr Isotopes in the Neoproterozoic for Stratigraphic Correlation:Research in the Jilin-Liaoning-Xuzhou-Huaiyang Area of the Sino-Korean Plate and Its Correlation with the Yangtze Plate

    Institute of Scientific and Technical Information of China (English)

    MENG Xianghua; GE Ming; LIU Yanxue; KUANG Hongwei; LIU Weifu; Francoise G. BOURROUILH-LE JAN; Robert BOURROUILH

    2004-01-01

    Based on a study of Neoproterozoic carbonates in the Jilin-Liaoning-Xuzhou-Huaiyang area, especially its cyclic sequence stratigraphy and Sr isotopes, two maximum sea flooding events (at 820 Ma and 835 Ma) have been identified. The resulting isochronous stratigraphic correlation proves that these Precambrian strata were connected between the Qingbaikou and the Nanhuan systems with a time range from 750 Ma to 850 Ma. The disappearance of microsparite carbonate and coming of a glacial stage offer important evidence for worldwide stratigraphic correlation and open a window for further correlation of the stratigraphic successions across the Sino-Korean and Yangtze Plates. A new correlation scheme is therefore provided based on our work.

  6. Algebraic Groups

    DEFF Research Database (Denmark)

    2007-01-01

    of algebraic groups (in a broad sense) has seen important developments in several directions, also related to representation theory and algebraic geometry. The workshop aimed at presenting some of these developments in order to make them accessible to a "general audience" of algebraic group......-theorists, and to stimulate contacts between participants. Each of the first four days was dedicated to one area of research that has recently seen decisive progress: \\begin{itemize} \\item structure and classification of wonderful varieties, \\item finite reductive groups and character sheaves, \\item quantum cohomology...... of homogeneous varieties, \\item representation categories and their connections to orbits and flag varieties. \\end{itemize} The first three days started with survey talks that will help to make the subject accessible to the next generation. The talks on the last day introduced to several recent advances...

  7. Group Anonymity

    CERN Document Server

    Chertov, Oleg; 10.1007/978-3-642-14058-7_61

    2010-01-01

    In recent years the amount of digital data in the world has risen immensely. But, the more information exists, the greater is the possibility of its unwanted disclosure. Thus, the data privacy protection has become a pressing problem of the present time. The task of individual privacy-preserving is being thoroughly studied nowadays. At the same time, the problem of statistical disclosure control for collective (or group) data is still open. In this paper we propose an effective and relatively simple (wavelet-based) way to provide group anonymity in collective data. We also provide a real-life example to illustrate the method.

  8. Informal groups

    NARCIS (Netherlands)

    E. van den Berg; P. van Houwelingen; J. de Hart

    2011-01-01

    Original title: Informele groepen Going out running with a group of friends, rather than joining an official sports club. Individuals who decide to take action themselves rather than giving money to good causes. Maintaining contact with others not as a member of an association, but through an Inter

  9. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group, established at the start of 2010, has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure There are now 55 CMS Centres worldwide that are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS offline and computing operations, hosting dedicated analysis efforts such as during the CMS Heavy Ion lead-lead running. With a majority of CMS sub-detectors now operating in a “shifterless” mode, many monitoring operations are now routinely performed from there, rather than in the main Control Room at P5. The CMS Communications Group, CERN IT and the EVO team are providing excellent videoconferencing support for the rapidly-increasing number of CMS meetings. In parallel, CERN IT and ...

  10. Group play

    DEFF Research Database (Denmark)

    Tychsen, Anders; Hitchens, Michael; Brolund, Thea

    2008-01-01

    of group dynamics, the influence of the fictional game characters and the comparative play experience between the two formats. The results indicate that group dynamics and the relationship between the players and their digital characters, are integral to the quality of the gaming experience in multiplayer......Role-playing games (RPGs) are a well-known game form, existing in a number of formats, including tabletop, live action, and various digital forms. Despite their popularity, empirical studies of these games are relatively rare. In particular there have been few examinations of the effects...... of the various formats used by RPGs on the gaming experience. This article presents the results of an empirical study, examining how multi-player tabletop RPGs are affected as they are ported to the digital medium. Issues examined include the use of disposition assessments to predict play experience, the effect...

  11. Lego Group

    DEFF Research Database (Denmark)

    Møller Larsen, Marcus; Pedersen, Torben; Slepniov, Dmitrij

    2010-01-01

    The last years’ rather adventurous journey from 2004 to 2009 had taught the fifth-largest toy-maker in the world - the LEGO Group - the importance of managing the global supply chain effectively. In order to survive the largest internal financial crisis in its roughly 70 years of existence......, the management had, among many initiatives, decided to offshore and outsource a major chunk of its production to Flextronics. In this pursuit of rapid cost-cutting sourcing advantages, the LEGO Group planned to license out as much as 80 per cent of its production besides closing down major parts...... of the production in high cost countries. Confident with the prospects of the new partnership, the company signed a long-term contract with Flextronics. This decision eventually proved itself to have been too hasty, however. Merely three years after the contracts were signed, LEGO management announced that it would...

  12. Group Connections: Whole Group Teaching.

    Science.gov (United States)

    Griffiths, Dorothy

    2002-01-01

    A learner-centered approach to adult group instruction involved learners in investigating 20th-century events. The approach allowed learners to concentrate on different activities according to their abilities and gave them opportunities to develop basic skills and practice teamwork. (SK)

  13. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The CMS Communications Group, established at the start of 2010, has been strengthening the activities in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The Communications Group has invested a lot of effort to support the operations needs of CMS. Hence, the CMS Centres where physicists work on remote CMS shifts, Data Quality Monitoring, and Data Analysis are running very smoothly. There are now 55 CMS Centres worldwide, up from just 16 at the start of CMS data-taking. The latest to join are Imperial College London, the University of Iowa, and the Università di Napoli. The CMS Centre@CERN in Meyrin, which is now full repaired after the major flooding at the beginning of the year, has been at the centre of CMS offline and computing operations, most recently hosting a large fraction of the CMS Heavy Ion community during the lead-lead run. A number of sub-detector shifts can now take pla...

  14. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS Offline and Computing operations, and a number of subdetector shifts can now take place there, rather than in the main Control Room at P5. A new CMS meeting room has been equipped for videoconferencing in building 42, next to building 40. Our building 28 meeting room and the facilities at P5 will be refurbished soon and plans are underway to steadily upgrade the ageing equipment in all 15 CMS meeting rooms at CERN. The CMS evaluation of the Vidyo tool indicates that it is not yet ready to be considered as a potential replacement for EVO. The Communications Group provides the CMS-TV (web) cha...

  15. 皖南新元古代花岗闪长岩地球化学特征及构造环境%Geochemical characteristics and tectonic setting of Neoproterozoic granodiorites in South Anhui Province

    Institute of Scientific and Technical Information of China (English)

    翁望飞; 支利庚; 蔡连友; 李永成; 徐生发; 王邦民

    2012-01-01

    皖南新元古代花岗闪长岩沿祁门-歙县-三阳深断裂呈串珠状出露。本文在对其岩石学、地球化学细致分析的基础上,探讨了岩体的岩石成因和产出环境。皖南新元古代花岗闪长岩主要由石英、钾长石和斜长石组成,普遍含富铝矿物黑云母和堇青石,副矿物包括锆石、磷灰石、钛铁矿、独居石、磷钇矿、极少的磁铁矿等。地球化学分析数据显示,岩石总体具高硅、高钾、高铝和低钠、低镁、低钙的特征;岩石富碱(ALK=6.63%),高K2O/Na2O比值(1.33)。里特曼指数δ为0.8~2.91,碱度率AR为1.56~3.14,属高钾钙碱性系列。岩石铝饱和指数(A/CNK-1.31)大于1.1,具强过铝质S型花岗岩的特征。岩石稀土元素呈轻稀土富集、重稀土亏损的特征,∑LREE/∑HREE比值为5.36~8.36,具较强的负铕异常(δEu=0.39~0.7),配分模式为右倾“V”字形态;微量元素明显富集Rb、Th而亏损Ba、Nb、Ta、Sr等,为低Sr高Yb型花岗岩。地球化学特征显示其岩浆源于围岩-中元古代牛屋组浅变质千枚岩的部分熔融,反映陆-陆碰撞挤压造山环境,为晋宁运动晚期华夏板块向北俯冲与扬子板块碰撞造山的火山弧产物。%Neoproterozoic granodiorites in South Anhui Province are developed along Qimen-Shexian-Sanyang deep fracture and outcropped in the form of beaded veins. This paper studied petrographical and geochemi- cal characteristics of these granodiorites as well as its petrogenesis and tectonic setting. These granodior- ites mainly consist of quartz, potash feldspar, plagioelase, biotite and cordierite with minor accessory min- erals of zircon, apatite, ilmenite, monazite, xenotime. Geochemical analyses show that the granodiorites have high contents of SiO2, K2O, Al2O3 and total alkal (ALK=6.63%), but relatively low contents of Na2O, MgO, CaO. The ratios of K2O/Na2O (1.33

  16. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2012-01-01

      Outreach and Education We are fortunate that our research has captured the public imagination, even though this inevitably puts us under the global media spotlight, as we saw with the Higgs seminar at CERN in December, which had 110,000 distinct webcast viewers. The media interest was huge with 71 media organisations registering to come to CERN to cover the Higgs seminar, which was followed by a press briefing with the DG and Spokespersons. This event resulted in about 2,000 generally positive stories in the global media. For this seminar, the CMS Communications Group prepared up-to-date news and public material, including links to the CMS results, animations and event displays [http://cern.ch/go/Ch8thttp://cern.ch/go/Ch8t]. There were 44,000 page-views on the CMS public website, with the Higgs news article being by far the most popular item. CMS event displays from iSpy are fast becoming the iconic media images, featuring on numerous major news outlets (BBC, CNN, MSN...) as well as in the sci...

  17. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The recently established CMS Communications Group, led by Lucas Taylor, has been busy in all three of its main are areas of responsibility: Communications Infrastructure, Information Systems, and Outreach and Education Communications Infrastructure The damage caused by the flooding of the CMS Centre@CERN on 21st December has been completely repaired and all systems are back in operation. Major repairs were made to the roofs, ceilings and one third of the floor had to be completely replaced. Throughout these works, the CMS Centre was kept operating and even hosted a major press event for first 7 TeV collisions, as described below. Incremental work behind the scenes is steadily improving the quality of the CMS communications infrastructure, particularly Webcasting, video conferencing, and meeting rooms at CERN. CERN/IT is also deploying a pilot service of a new videoconference tool called Vidyo, to assess whether it might provide an enhanced service at a lower cost, compared to the EVO tool currently in w...

  18. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin is particularly busy at the moment, hosting about 50 physicists taking part in the heavy-ion data-taking and analysis. Three new CMS meeting room will be equipped for videoconferencing in early 2012: 40/5B-08, 42/R-031, and 28/S-029. The CMS-TV service showing LHC Page 1, CMS Page 1, etc. (http://cmsdoc.cern.ch/cmscc/projector/index.jsp) is now also available for mobile devices: http://cern.ch/mcmstv. Figure 12: Screenshots of CMS-TV for mobile devices Information Systems CMS has a new web site: (http://cern.ch/cms) using a modern web Content Management System to ensure content and links are managed and updated easily and coherently. It covers all CMS sub-projects and groups, replacing the iCMS internal pages. It also incorporates the existing CMS public web site (http:/...

  19. 桂北新元古代两类过铝花岗岩的地球化学研究%Geochemical studies on two types of Neoproterozoic peraluminous granitoids in northern Guangxi

    Institute of Scientific and Technical Information of China (English)

    葛文春; 李献华; 李正祥; 周汉文; 李寄嵎

    2001-01-01

    The Neoproterozoic granitoids in northern Guangxi consist ofbiotite granodiorite and biotite granitoids. The geochemical characteristics indicate that biotite granodiorite is equivalent to cordierite-bearing peraluminous granitoids (CPG), while biotite granitoids are similar to muscovite-monzonitic granite (MPG). Biotite granitoids are the result of partial melting of mature crust, and the formation of biotite granodiorites are related to the mixing of mantle plume-derived mafic magma and crustal-derived peraluminous biotite granitic magma. The formation of these two types of Neoproterozoic peraluminous granitoids is irrelevant to the compressional structures caused by collisional orogney which led to crustal thickening, but relevant to extensional structures caused by the ascent of mantle plume which led to the breakup of Rodinia supercontinent.%广西北部新元古代花岗岩类岩石包括黑云母花岗闪长岩和黑云母花岗岩。地球化学特征表明,黑云母花岗闪长岩与含堇青石的过铝花岗岩(CPG)相当,而黑云母花岗岩则类似于白云母二长花岗岩(MPG)。黑云母花岗岩类是成熟地壳岩石部分熔融作用的产物,而黑云母花岗闪长岩类的形成与地幔柱起源的镁铁质岩浆和地壳起源的过铝质黑云母花岗岩浆之间的混合作用有关。这两类新元古代过铝花岗岩的形成与碰撞造山导致地壳加厚的挤压性构造无关,而与导致Rodinia超大陆裂解的地幔柱上升诱发岩石圈伸展的张性构造相联系。

  20. Evolution of a Neoproterozoic suture in the Iberian Massif, Central Portugal: New U-Pb ages of igneous and metamorphic events at the contact between the Ossa Morena Zone and Central Iberian Zone

    Science.gov (United States)

    Henriques, S. B. A.; Neiva, A. M. R.; Ribeiro, M. L.; Dunning, G. R.; Tajčmanová, L.

    2015-04-01

    A Neoproterozoic suture is exposed at the contact between the Ossa Morena Zone and the Central Iberian Zone, in the Iberian Massif (Central Portugal), the westernmost segment of the European Variscides. Although, the Cadomian magmatic and tectonometamorphic events have been previously documented, their timing is still poorly constrained, particularly in the inner zones of the suture. We used geochronological (ID-TIMS U-Pb) data to establish the sequence of events, isotopic (Rb-Sr, Sm-Nd) data to characterize the magmatic sources and thermodynamic modelling to determine the maximum P-T conditions attained during the Cadomian metamorphism. The first event, in the future Ossa Morena Zone, is the onset of island arc magmatism represented mainly by tholeiites with a MORB signature. Their igneous crystallization age is unknown, but they are older than ca. 539 Ma. This magmatic activity was accompanied by deposition of fine-grained sediments in a Neoproterozoic basin. The second event is the evolution of the Cadomian magmatic arc in different stages. The earliest magmatic stage occurs at ca. 692 Ma, which is the oldest igneous age known in the Ossa Morena Zone. It is followed by the generation of subalkaline and peraluminous protoliths at ca. 569 Ma, with the isotopic signature of old crustal sources. The final phase of the arc magmatism (ca. 548-544 Ma) involved mainly partial melting of continental crust. The range of the main magmatic activity must have been between ca. 569 Ma and ca. 544 Ma as mentioned for other areas in the Ossa Morena Zone. A major metamorphic event, recorded in metamorphic monazite, zircon and titanite at ca. 540 Ma, attained upper amphibolite facies conditions close to the transition to granulite facies (7-8 kbar and 640-660 °C). It represents the continental arc accretion of the Ossa Morena Zone with the Iberian Autochthon passive margin (future Central Iberian Zone). The Early Ordovician rocks (ca. 483-477 Ma) were generated from depleted and

  1. From mapping class groups to automorphism groups of free groups

    DEFF Research Database (Denmark)

    Wahl, Nathalie

    2005-01-01

    We show that the natural map from the mapping class groups of surfaces to the automorphism groups of free groups, induces an infinite loop map on the classifying spaces of the stable groups after plus construction. The proof uses automorphisms of free groups with boundaries which play the role...... of mapping class groups of surfaces with several boundary components....

  2. SHRIMP U-Pb Dating of Zircons of a Dark Eclogite and a Garnet-bearing Gneissic Granitic Rock from Bixiling, EasternDabie Area, Anhui Province: Isotope Chronological Evidence of Neoproterozoic UHP Metamorphism

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The paper reports SHRIMP U-Pb zircon data of a dark eclogite and a post-eclogite garnet-bearing gneissic granitic rock from the Bixiling area, Yuexi County, Anhui Province, in the eastern Dabie Mountains. The eclogite, which is metamorphosed basic tuff, contains very scarce zircons in omphacite or garnet, but more zircons in quartz. They usually exhibit a double-layered texture, as shown clearly in cathodoluminescence images. Their inner main parts give a206 Pb/238U age of 757±7Ma, representing the approximate age of the high-pressure (HP)-ultrahighpressure (UHP) metamorphic event duing which the eclogite was formed. The outer peripheral parts of the zircons,which have been modified by late-stage fluids, give an age of 223±3 Ma. The granitic rock contains more zircons of anatectic origin found mostly in feldspar and quartz and usually also showing a similar composite texture. The inner main parts of the anatectic zircons with oscillatory zoning give a 206Pb/238U age of 727±15Ma for the approximate age of the emplacement of the granitic rock, and their outer parts, an age of 219±3 Ma for a similar or even the same fluid event. It is thus suggested that the HP-UHP metamorphism of the Bixiling eclogite facies rocks took place during the Neoproterozoic Jinningian,and the Indosinian age values may only represent a late event in the nature of fluid activity.

  3. U-Pb (LA-ICPMS) zircon ages and Nd isotopes for granitoids of the Tamboril-Santa Quiteria Complex, Ceara Central Domain: implication for neoproterozoic syncollisional magmatism in north Borborema Province, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Felipe Grandjean da; Araujo, Carlos Eduardo Ganade de; Vasconcelos, Antonio Maurilio, E-mail: felipe.costa@cprm.gov.br, E-mail: caegeo@gmail.com, E-mail: maurilio.vasconcelos@cprm.gov.br [Servico Geologico do Brasil (CPRM), Fortaleza, CE (Brazil); Amaral, Wagner da Silva, E-mail: wamaral@ufc.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Geologia; Rodrigues, Joseneusa Brilhante, E-mail: joseneusa.rodrigues@cprm.gov.br [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil)

    2013-06-15

    The Tamboril-Santa Quiteria Complex (TSQC) is one of the largest Neoproterozoic plutonic manifestations in the north Borborema Province (NE Brazil). It represents an anatectic/igneous association characterized by a number of magmatic pulses that occurred in the 650-610 Ma interval. In this paper, we present U-Pb (LA-MC-ICP-MS) zircon ages and Nd isotopes for quartz monzonite and quartz diorites of the southern part of TSQC. The quartz monzonite belong to a hybrid granitoid association, including monzonite, syenites and quartz syenites, all with abundant mafic magmatic enclaves. A quartz monzonite sample yielded a U-Pb zircon age of 634 {+-} 10 Ma and a TDM age of 2.69 Ga. The quartz diorites are much more homogeneous in composition and yielded a U-Pb zircon age of 618 {+-} 23 Ma and a TDM age of 2.19 Ga. The presence of coeval mantle-derived magmatism and diatexites (crustal anatexis) post-dating high-pressure metamorphism (ca. 650 Ma), and together with high-temperature metamorphism (ca. 630-610 Ma), suggests that this large magmatic manifestation evolved in a collisional setting, probably related to slab break off during the Western Gondwana amalgamation. (author)

  4. U-Pb (Zircon Ages of Metavolcanic Rocks From the Itaiacoca Group: Tectonic Implications

    Directory of Open Access Journals (Sweden)

    Oswaldo Siga Jr.

    2003-08-01

    Full Text Available The main aim of this work is to present and discuss the U-Pb ages obtained for zircon grains from metavolcanic rocks of theItaiacoca Group. The Itaiacoca Group is a metavolcano-sedimentary sequence, which occurs as a narrow belt between theCunhaporanga granitic batholith to the northwest and the Itapirapuã shear zone to the south and southwest, which separates thesequence from the Três Córregos granite batholith and metasedimentary rocks of the Açungui Group. Geological studies of thesouthern part of the Itaiacoca belt led to the recognition of three units, represented (from base to top by metawackes with animportant volcanic component, metacarbonate, and metapelitic and metapsammitic rocks. The U-Pb geochronological analyses ofzircon grains from two outcrops of metavolcanic rocks yield ages of 628 ± 18 Ma (SHRIMP and 636 ± 30 Ma (conventional multigrainanalyses. These ages are quite close to the metamorphic event recorded in the Itaiacoca Group (628 – 610 Ma, suggesting ashort interval between the formation of these rocks and closure of the basin. Furthermore, this volcanism is very close to the age offormation of the Três Córregos (630 Ma and Cunhaporanga (590 Ma granitic batholiths, admitted as associated with a probablemagmatic arc. Such an isotopic pattern characterizes a Neoproterozoic tectonic scenario involving volcanism, metamorphism andgranitic plutonism, interpreted here as the final stages in the evolution of the Itaiacoca Basin.

  5. 华北地台东西部中新元古界生烃条件比较研究%Comparative research on hydrocarbon generation conditions of Meso-Neoproterozoic between east and west of North China Platform

    Institute of Scientific and Technical Information of China (English)

    林玉祥; 李晓凤; 闫晓霞; 郭凤霞; 刘虎; 李秀芹

    2014-01-01

    通过对华北地台中新元古界有机质丰度、类型、热演化程度以及生烃演化史等的分析,全面对比了以蒙陕裂陷槽为代表的华北地台西部和以冀辽裂陷槽为代表的华北地台东部中新元古界的生烃条件,结果表明,冀辽裂陷槽中新元古界烃源岩有机质丰度高、类型好,为优质烃源岩;蒙陕裂陷槽中新元古界烃源岩有机质丰度低,尽管类型也较好,烃源岩仅为中等-偏差。华北地台东、西部中新元古界现今热演化程度较为接近,但其热演化过程差异较大,东部自晚古生代以后持续抬升,上覆地层剥蚀殆尽;西部则持续沉降,至中生代方达到最高演化程度。总体看来,华北地台中新元古界有利生烃区首推冀辽裂陷槽,其次为蒙陕裂陷槽和豫陕裂陷槽。%Based on the analysis of the abundance, type, thermal evolution degree of organic matter and the hy-drocarbon generation history in Meso-Neoproterozoic in the North China Platform, the western part of the plat-form represented by the Mengshan Aulacogen was compared with the eastern part represented by the Jiliao Aula-cogen in hydrocarbon generation condition. The hydrocarbon source rocks of Meso-Neoproterozoic in the eastern part of the North China Platform are premium source rocks for high abundance and good type of organic matter while the western hydrocarbon source rocks with low abundance of organic matter are only medium to bias, even though their type is also good. Although the thermal evolution of the eastern part is similar to the western part, their thermal evolutions are quite different from the Late Paleozoic:the eastern part uplifted in succession and the overlying strata denuded;while the western part continued to subside and achieved the highest thermal evolution degree in Mesozoic. Generally speaking, the Jiliao Aulacogen is the most favorable hydrocarbon generation area in the North China platform, then the

  6. Integrated Groups and Smooth Distribution Groups

    Institute of Scientific and Technical Information of China (English)

    Pedro J. MIANA

    2007-01-01

    In this paper, we prove directly that α-times integrated groups define algebra homo-morphisms. We also give a theorem of equivalence between smooth distribution groups and α-times integrated groups.

  7. Compositional variations and tectonic settings of podiform chromitites and associated ultramafic rocks of the Neoproterozoic ophiolite at Wadi Al Hwanet, northwestern Saudi Arabia

    Science.gov (United States)

    Ahmed, Ahmed Hassan; Harbi, Hesham M.; Habtoor, Abdelmonem M.

    2012-08-01

    Wadi Al Hwanet area in NW of Saudi Arabia is part of the Jebel Ess ophiolite constituting the northeastern part of the ˜700 Ma Yanbu-Sol Hamed-Onib-Allaqi-Heiani suture of the northern Arabian-Nubian Shield. The mantle section of Wadi Al Hwanet ophiolite consists mainly of voluminous harzburgites overlain by thick, massive transition-zone dunites, and small-scale chromitite pods. The harzburgites and massive dunites are exceptionally fresh; primary magmatic textures and silicate minerals are still preserved. Two modes of podiform chromitites exist; small lensoidal pods (group I), and relatively large dike-like pods (group II). Geochemically, the former chromitite type contains chromian spinels with high Cr# (0.79-0.81) and displays a PGE-poor character, with steep negatively-sloped PGE distribution patterns, whereas the latter chromitite type contains chromian spinels with relatively lower Cr# (0.61-0.71) and is PGE-rich (up to 1000 ppb), with positively-sloped PGE distribution patterns. The group II chromitites have much higher sulfide content than the group I suite. Parental melt compositions, in equilibrium with podiform chromitites, vary in Al2O3, FeO*/MgO and TiO2 contents from group I to group II chromitites, although both of them are in the range of the boninitic melts. The differences in the chromitites chemistry are most probably due to variable degrees of partial melting of the involved melts. Two stages of a magmatic activity were inferred for the chromitites genesis. The group I chromitites, of high Cr# of chromian spinels and PGE-poor negatively-sloped patterns, were precipitated in the first stage from a boninitic melt produced by a high degree of partial melting at a supra-subduction zone setting. The second chromitite-forming stage involves a relatively low degree of partial melting under high activities of sulfur and oxygen to produce the group II chromitites with enrichment in sulfides and PGE contents, possibly in a supra-subduction zone setting

  8. Group typicality, group loyalty and cognitive development.

    Science.gov (United States)

    Patterson, Meagan M

    2014-09-01

    Over the course of childhood, children's thinking about social groups changes in a variety of ways. Developmental Subjective Group Dynamics (DSGD) theory emphasizes children's understanding of the importance of conforming to group norms. Abrams et al.'s study, which uses DSGD theory as a framework, demonstrates the social cognitive skills underlying young elementary school children's thinking about group norms. Future research on children's thinking about groups and group norms should explore additional elements of this topic, including aspects of typicality beyond loyalty.

  9. Which finite simple groups are unit groups?

    DEFF Research Database (Denmark)

    Davis, Christopher James; Occhipinti, Tommy

    2014-01-01

    We prove that if G is a finite simple group which is the unit group of a ring, then G is isomorphic to either (a) a cyclic group of order 2; (b) a cyclic group of prime order 2^k −1 for some k; or (c) a projective special linear group PSLn(F2) for some n ≥ 3. Moreover, these groups do all occur a...

  10. Group Cohesion in Experiential Growth Groups

    Science.gov (United States)

    Steen, Sam; Vasserman-Stokes, Elaina; Vannatta, Rachel

    2014-01-01

    This article explores the effect of web-based journaling on changes in group cohesion within experiential growth groups. Master's students were divided into 2 groups. Both used a web-based platform to journal after each session; however, only 1 of the groups was able to read each other's journals. Quantitative data collected before and…

  11. Group Work Publication-1991.

    Science.gov (United States)

    Zimpfer, David G.

    1992-01-01

    Lists 21 new publications in group work, of which 9 are reviewed. Those discussed include publications on group counseling and psychotherapy, structured groups, support groups, psychodrama, and social group work. (Author/NB)

  12. Detrital zircon U-Pb and Hf isotopic data from the Liuling Group in the South Qinling belt: Provenance and tectonic implications

    Science.gov (United States)

    Liao, Xiao-ying; Wang, Ya-wei; Liu, Liang; Wang, Chao; Santosh, M.

    2017-02-01

    The Liuling Group is exposed in the Northern part of the South Qinling orogenic belt. LA-ICP-MS U-Pb analysis of detrital zircons from the meta-sandstones in this Group yields ages ranging between 400 Ma and 3200 Ma, with three prominent age clusters at 500-400 Ma, 850-700 Ma and 1000-900 Ma. A few older zircon populations with U-Pb ages of 1750-1450 Ma, 2000 Ma and 2600-2400 Ma are also present. Age data integrated with cathodoluminescence, trace element data and εHf(t) values of zircon grains show that the Liuling sediments have a complex source. Source rocks mainly include Early Neoproterozoic and Early Paleozoic granitoids, together with minor ultra-high pressure/high pressure (HP-UHP) metamorphic rocks, and paragneiss in the North Qinling belt, and Middle-Late Neoproterozoic magmatic rocks in the South Qinling belt. The dominant population of detrital zircon grains with ages between 500 Ma and 400 Ma show the characteristics of both magmatic and metamorphic zircons. They show three age clusters at 497 Ma, 451 Ma, and ca. 420 Ma and show marked correlation with the three stages of Palaeozoic magmatism, as well as with the peak and retrograde HP-UHP metamorphic stages in the North Qinling belt. This correlation demonstrates that these Early Palaeozoic granitoids and HP-UHP metamorphic rocks in the North Qinling belt were already exhumed to the surface, underwent erosion prior to Middle Devonian time and were then deposited in an extensional basin. Based on the results from detrital zircon U-Pb dating, combined with geochemical data and the regional geology, the deposition of Liuling sediments is inferred to have occurred in a post-orogenic extensional basin, rather than a subduction-related fore-arc basin or a foreland basin formed during or after continental collision.

  13. Group theories: relevance to group safety studies.

    Science.gov (United States)

    Benevento, A L

    1998-01-01

    Promoting safety in the workplace has been attempted in a variety of ways. Increasingly, industries are using groups such as safety teams and quality circles to promote worker safety. Group influences on individual behavior and attitudes have long been studied in the social psychology literature, but the theories have not been commonly found outside the psychology arena. This paper describes the group theories of group polarization, risky shift, social loafing, groupthink and team think and attempts to apply these theories to existing studies that examine work group influences on safety. Interesting parallels were found but only one study examined group influences as their primary focus of research. Since groups are increasingly used for safety promotion, future research on safety that studies group influences with respect to current group theories is recommended.

  14. Geochemistry of the Neoproterozoic (800-767 Ma) Cerro Bori orthogneisses, Dom Feliciano Belt in Uruguay: tectonic evolution of an ancient continental arc

    Science.gov (United States)

    Lenz, C.; Porcher, C. C.; Fernandes, L. A. D.; Masquelin, H.; Koester, E.; Conceição, R. V.

    2013-10-01

    The Cerro Bori orthogneisses, crystallized between ca. 800 and 767 Ma, are composed of a sequence of mafic gneisses, with dioritic-gabbroic and dioritic composition tectonically interleaved with a sequence of tonalitic and granodioritic gneisses. These rocks intruded the Chafalote paragneisses (metapelites, semipelites, carbonate and mafic rocks) and they were metamorphosed of high P-T conditions at ca. 676-654 Ma. This paper presents the first major and trace geochemical signatures, as well as Sm and Pb isotopic composition for the Cerro Bori orthogneisses, which allow distinguishing three different groups of rocks. Type I rocks are mafic gneisses with tholeiitic affinity, whereas the Type II rocks are tonalitic and granodioritic gneisses with calc-alkaline affinity. The third type is composed of biotite-rich mafic gneisses with potassic and ultrapotassic affinities. All the three types of rocks have negative ℰND values (between -2.12 and -6.67) and old TDM ages (between 1.2 and 2.0 Ga), indicating that the process of crustal assimilation/contamination was an important process, together with fractional crystallization. An continental arc tectonic setting is suggested to this association of rocks between 800 and 767 Ma. This subduction suggests the existence of an ocean between Rio de La Plata and adjacent cratons during the break up of the Rodinia supercontinent.

  15. Interagency mechanical operations group numerical systems group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    This report consists of the minutes of the May 20-21, 1971 meeting of the Interagency Mechanical Operations Group (IMOG) Numerical Systems Group. This group looks at issues related to numerical control in the machining industry. Items discussed related to the use of CAD and CAM, EIA standards, data links, and numerical control.

  16. AREVA group overview; Presentation du groupe AREVA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-02-08

    This document presents the Group Areva, a world nuclear industry leader, from a financial holding company to an industrial group, operating in two businesses: the nuclear energy and the components. The structure and the market of the group are discussed, as the financial assets. (A.L.B.)

  17. Petrogenesis of syntectonic granites emplaced at the transition from thrusting to transcurrent tectonics in post-collisional setting: Whole-rock and Sr-Nd-Pb isotope geochemistry in the Neoproterozoic Quatro Ilhas and Mariscal Granites, Southern Brazil

    Science.gov (United States)

    Florisbal, Luana Moreira; Bitencourt, Maria de Fátima; Janasi, Valdecir de Assis; Nardi, Lauro Valentim Stoll; Heaman, Larry M.

    2012-11-01

    The Neoproterozoic post-collisional period in southern Brazil (650-580 Ma) is characterized by substantial volumes of magma emplaced along the active shear zones that compose the Southern Brazilian Shear Belt. The early-phase syntectonic magmatism (630-610 Ma) is represented by the porphyritic, high-K, metaluminous to peraluminous Quatro Ilhas Granitoids and the younger heterogranular, slightly peraluminous Mariscal Granite. Quatro Ilhas Granitoids include three main petrographic varieties (muscovite-biotite granodiorite — mbg; biotite monzogranite — bmz; and leucogranite — lcg) that, although sharing some significant geochemical characteristics, are not strictly comagmatic, as shown by chemical and Sr-Nd-Pb isotope data. The most primitive muscovite-biotite granodiorite was produced by contamination of more mafic melts (possibly with some mantle component) with peraluminous crustal melts; the biotite monzogranite, although more felsic, has higher Ca, MgO, TiO2 and Ba, and lower K2O, FeOt, Sr and Rb contents, possibly reflecting some mixing with coeval mafic magmas of tholeiitic affinity; the leucogranite may be derived from pure crustal melts. The Mariscal Granite is formed by two main granite types which occur intimately associated in the same pluton, one with higher K (5-6.5 wt.% K2O) high Rb and lower CaO, Na2O, Ba and Zr as compared to the other (3-5 wt.% of K2O). The two Mariscal Granite varieties have compositional correspondence with fine-grained granites (fgg) that occur as tabular bodies which intruded the Quatro Ilhas Granoitoids before they were fully crystallized, and are inferred to correspond to the Mariscal Granite feeders, an interpretation that is reinforced by similar U-Pb zircon crystallization ages. The initial evolution of the post-collisional magmatism, marked by the emplacement of the Quatro Ilhas Granitoids varieties, activated sources that produced mantle and crustal magmas whose emplacement was controlled both by flat-lying and

  18. Possible early Neoproterozoic magmatism associated with slab window in the Pingshui segment of the Jiangshan-Shaoxing suture zone: Evidence from zircon LA-ICP-MS U-Pb geochronology and geochemistry

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (~1.00%), TiO2 (~3.08%) and HFSE (e.g., Nb=9.53-10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8-8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84-0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with "SSZ-type" plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (εNd(t)=7.5-8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.

  19. Possible early Neoproterozoic magmatism associated with slab window in the Pingshui segment of the Jiangshan-Shaoxing suture zone: Evidence from zircon LA-ICP-MS U-Pb geochronology and geochemistry

    Institute of Scientific and Technical Information of China (English)

    CHEN ZhiHong; GUO KunYi; DONG YongGuan; CHEN Rong; LI LongMing; LIANG YiHong; LI ChunHai; YU XiMing; ZHAO Ling; XING GuangFui

    2009-01-01

    We report here geochemical data, U-Pb zircon ages, and Hf Isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranitee (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2Os5(~1.00%), TiO2(~3.08%) and HFSE (e.g., Nb=9.53-10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8-8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (AJCNK=0.84-0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) Is consistent with "SSZ-type" plagiogrenite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (trod(f)=7.5-8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active conUnen- tal margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling aathenosphere below the slab window may have provided significant thermodynamic conditions.

  20. Introduction to Sporadic Groups

    Directory of Open Access Journals (Sweden)

    Luis J. Boya

    2011-01-01

    Full Text Available This is an introduction to finite simple groups, in particular sporadic groups, intended for physicists. After a short review of group theory, we enumerate the 1+1+16=18 families of finite simple groups, as an introduction to the sporadic groups. These are described next, in three levels of increasing complexity, plus the six isolated ''pariah'' groups. The (old five Mathieu groups make up the first, smallest order level. The seven groups related to the Leech lattice, including the three Conway groups, constitute the second level. The third and highest level contains the Monster group M, plus seven other related groups. Next a brief mention is made of the remaining six pariah groups, thus completing the 5+7+8+6=26 sporadic groups. The review ends up with a brief discussion of a few of physical applications of finite groups in physics, including a couple of recent examples which use sporadic groups.

  1. Free Boolean Topological Groups

    Directory of Open Access Journals (Sweden)

    Ol’ga Sipacheva

    2015-11-01

    Full Text Available Known and new results on free Boolean topological groups are collected. An account of the properties that these groups share with free or free Abelian topological groups and properties specific to free Boolean groups is given. Special emphasis is placed on the application of set-theoretic methods to the study of Boolean topological groups.

  2. Structural analysis of the Rio Pardo Group - southeast of Bahia state

    Directory of Open Access Journals (Sweden)

    Marcos Egydio-Silva

    2011-12-01

    Full Text Available The Meso- to Neoproterozoic Rio Pardo Group is located in the southeastern region of the Bahia State and consistsof low-grade metasedimentary rocks deposited on Paleoproterozoic to Archean basement. From the base to the top, themetasedimentary rocks are grouped into the following sequences: Panelinha Formation consisting of coarse-grainedimmature clastics; the overlying Itaimbé Subgroup which is made up of the Camacã Formation (metapelites with localcarbonates, the Água Preta Formation (fi ne-grained metapsamites and local carbonate lenses, Serra do Paraíso Formation(metacarbonates and quartzites and the Santa Maria Eterna Formation (metaconglomerates and metacarbonates. TheSalobro Formation was deposited unconformably on this sequence and consists of coarse-grained immature and local fi negrainedclastic rocks. The Rio Pardo Group was affected by three successive folding events, which were recorded in twolitho-structural units. The litho-structural unit 1 is located in the northeastern part of the basin, and the litho-structural unit2, in the southwestern part of the basin. These units are separated by the Rio Pardo-Água Preta inverse fault, trending NWSEand dipping SW. The fi rst unit is autochthonous and monophasic and displays open folds and slaty cleavage, changinggradually towards southwest into large overturned folds with axial plane schistosity. The second unit is polyphasic andshows large folds with NE vergence. A third folding is represented by folds and foliations present at the western marginof the basin. The NE vergence of the Rio Pardo Group can be explained by changes in the deformation regime and in thedirection of the principal axis of deformation in the north sector of the Araçuaí belt during the Brasiliano collision orogen.The tectonic transport to the north could be the cause of deformation of the Rio Pardo Group.

  3. Group Work: How to Use Groups Effectively

    Science.gov (United States)

    Burke, Alison

    2011-01-01

    Many students cringe and groan when told that they will need to work in a group. However, group work has been found to be good for students and good for teachers. Employers want college graduates to have developed teamwork skills. Additionally, students who participate in collaborative learning get better grades, are more satisfied with their…

  4. Homomorphisms of quantum groups

    CERN Document Server

    Meyer, Ralf; Woronowicz, Stanisław Lech

    2010-01-01

    We introduce some equivalent notions of homomorphisms between quantum groups that behave well with respect to duality of quantum groups. Our equivalent definitions are based on bicharacters, coactions, and universal quantum groups, respectively.

  5. MSUD Family Support Group

    Science.gov (United States)

    ... Group The MSUD Family Support Group is a non-profit 501 (c)(3) organization for those with MSUD ... Family Support Group is a 501(c)(3) non-profit organization with no paid staff. Funds are needed ...

  6. Food Groups Recipes

    OpenAIRE

    2012-01-01

    15 pages In 2011, My Plate replaced the Food Pyramid as a visual representation for the USDA Dietary Guidelines. This publication, a group of recipes based on this new division of food groups, reflects the effort of the USDA and other groups to translate science-based research into everyday practice for Americans. Fifteen recipes (3 from each food group) show ways to use foods from each food group. They are complete with basic nutritional analyses and food group amounts.

  7. Locally minimal topological groups

    OpenAIRE

    Außenhofer, Lydia; Chasco, María Jesús; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the ...

  8. Ordered groups and infinite permutation groups

    CERN Document Server

    1996-01-01

    The subjects of ordered groups and of infinite permutation groups have long en­ joyed a symbiotic relationship. Although the two subjects come from very different sources, they have in certain ways come together, and each has derived considerable benefit from the other. My own personal contact with this interaction began in 1961. I had done Ph. D. work on sequence convergence in totally ordered groups under the direction of Paul Conrad. In the process, I had encountered "pseudo-convergent" sequences in an ordered group G, which are like Cauchy sequences, except that the differences be­ tween terms of large index approach not 0 but a convex subgroup G of G. If G is normal, then such sequences are conveniently described as Cauchy sequences in the quotient ordered group GIG. If G is not normal, of course GIG has no group structure, though it is still a totally ordered set. The best that can be said is that the elements of G permute GIG in an order-preserving fashion. In independent investigations around that t...

  9. Communication in Organizational Groups

    OpenAIRE

    Monica RADU

    2007-01-01

    Organizational group can be defined as some persons between who exist interactive connections (functional, communication, affective, normative type). Classification of these groups can reflect the dimension, type of relationship or type of rules included. Organizational groups and their influence over the individual efficiency and the efficiency of the entire group are interconnected. Spontaneous roles in these groups sustain the structure of the relationship, and the personality of each indi...

  10. Group Psychotherapy in Iceland.

    Science.gov (United States)

    Ívarsson, Ómar

    2015-10-01

    In this overview of group psychotherapy in Iceland, an attempt will be made to describe how it is practiced today, give some glimpses into its earlier history, and clarify seven issues: (1) the standing of group psychotherapy in Iceland, its previous history, and the theoretical orientation of dynamic group therapy in the country; (2) the role of group therapy in the health care system; (3) how training in group therapy is organized; (4) the relationship between group psychotherapy research and clinical practice; (5) which issues/processes can be identified as unique to therapy groups in Iceland; and (6) how important are group-related issues within the social background of the country; and (7) what group work holds for the future.

  11. Toleration, Groups, and Multiculturalism

    DEFF Research Database (Denmark)

    Lægaard, Sune

    2014-01-01

    . The chapter relates the different possible meanings of groups toleration to widespread criticisms of multiculturalism for being excessively 'groupist' (e.g. to essentialise or reify groups), to promote group rights over individual rights, or to deny or ignore the internal heterogeneity of groups...... or the multiple identity affiliations of individuals. The chapter suggests that some of these standard criticisms of multiculturalism for being overly tolerant of minority groups, or being so in a way elevating groups over individuals, are less pressing on some understandings of the meaning of 'group......' as an object of policies of multicultural toleration than on others. So the chapter both contributes to the conceptual understanding of toleration and groups and to the normative debates about multiculturalism insofar as these turn on the toleration of groups....

  12. Locally minimal topological groups

    CERN Document Server

    enhofer, Lydia Au\\ss; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the NSS property, establishing that under certain conditions, locally minimal NSS groups are metrizable. A symmetric subset of an abelian group containing zero is said to be a GTG set if it generates a group topology in an analogous way as convex and symmetric subsets are unit balls for pseudonorms on a vector space. We consider topological groups which have a neighborhood basis at zero consisting of GTG sets. Examples of these locally GTG groups are: locally pseudo--convex spaces, groups uniformly free from small subgroups (...

  13. Higher arithmetic Chow groups

    CERN Document Server

    Gil, J I Burgos

    2009-01-01

    We give a new construction of higher arithmetic Chow groups for quasi-projective arithmetic varieties over a field. Our definition agrees with the higher arithmetic Chow groups defined by Goncharov for projective arithmetic varieties over a field. These groups are the analogue, in the Arakelov context, of the higher algebraic Chow groups defined by Bloch. The degree zero group agrees with the arithmetic Chow groups of Burgos. Our new construction is shown to be a contravariant functor and is endowed with a product structure, which is commutative and associative.

  14. Occurrence of helically coiled microfossil Obruchevella in the Owk Shale of the Kurnool Group and its significance

    Indian Academy of Sciences (India)

    Mukund Sharma; Yogmaya Shukla

    2012-06-01

    The present study reports occurrence of helically coiled microfossil Obruchevella Reitlinger from the Owk Shale of the Kurnool Group from the peninsular India. The age of the Kurnool Group is poorly constrained due to the absence of direct radiometric dating and meager palaeobiological data. Occurrence of Obruchevella is considered as a typical Vendian marker genus recorded mostly from close to the Precambrian–Cambrian boundary successions. Hence, the present assemblage is important to ascertain the age of the basin. In the Owk Shale, four species of Obruchevella, viz., O. delicata, O. parva, O. minor and O. valdaica are recorded as organic walled microfossils. Among them O. valdaica is the largest in terms of size parameters. On the global scale, the recovered species occur in the Late Neoproterozoic to Early Cambrian sediments. Therefore, the occurrence of microfossil Obruchevella in the Owk Shale and known burrow structures in the Narji Limestone suggest Ediacaran age close to the Cambrian for the Kurnool Basin and challenges the recently assigned esoproterozoic age of the basin.

  15. Provenance and paleogeography of the Devonian Durazno Group, southern Parana Basin in Uruguay

    Science.gov (United States)

    Uriz, N. J.; Cingolani, C. A.; Basei, M. A. S.; Blanco, G.; Abre, P.; Portillo, N. S.; Siccardi, A.

    2016-03-01

    A succession of Devonian cover rocks occurs in outcrop and in the subsurface of central-northern Uruguay where they were deposited in an intracratonic basin. This Durazno Group comprises three distinct stratigraphic units, namely the Cerrezuelo, Cordobés and La Paloma formations. The Durazno Group does not exceed 300 m of average thickness and preserves a transgressive-regressive cycle within a shallow-marine siliciclastic shelf platform, and is characterized by an assemblage of invertebrate fossils of Malvinokaffric affinity especially within the Lower Devonian Cordobés shales. The sedimentary provenance of the Durazno Group was determined using petrography, geochemistry, and morphological studies of detrital zircons as well as their U-Pb ages. Sandstone petrography of Cerrezuelo and La Paloma sequences shows that they have a dominantly quartz-feldspathic composition with a minor contribution of other minerals. Whole-rock geochemical data indicate that alteration was strong in each of the three formations studied; chondritic-normalized REE patterns essentially parallel to PAAS, the presence of a negative Eu-anomaly, and Th/Sc and La/Hf ratios point to an average source composition similar to UCC or slightly more felsic. Within the Cerrezuelo Formation, recycling of older volcano-metasedimentary sources is interpreted from Zr/Sc ratios and high Hf, Zr, and REE concentrations. U-Pb detrital zircon age populations of the Cerrezuelo and La Paloma formations indicate that the principal source terranes are of Neoproterozoic age, but include also minor populations derived from Mesoproterozoic and Archean-Paleoproterozoic rocks. A provenance from the Cuchilla Dionisio-Dom Feliciano, Nico Pérez and Piedra Alta terranes of Uruguay and southern Brazil is likely. This study establishes an intracratonic extensional tectonic setting during Durazno time. Considering provenance age sources, regional paleocurrent distributions and the established orogenic history recorded in SW

  16. Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

    Science.gov (United States)

    Peacock, Jared R.; Selway, Katherine

    2016-01-01

    The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

  17. Group Decision Process Support

    DEFF Research Database (Denmark)

    Gøtze, John; Hijikata, Masao

    1997-01-01

    Introducing the notion of Group Decision Process Support Systems (GDPSS) to traditional decision-support theorists.......Introducing the notion of Group Decision Process Support Systems (GDPSS) to traditional decision-support theorists....

  18. About group digital signatures

    Directory of Open Access Journals (Sweden)

    Adriana Cristina Enache

    2012-09-01

    Full Text Available

    Group signatures try to combine security (no framing, no cheating and privacy(anonymity, unlinkability.A group digital signature is a digital signature with enhanced privacy features that allows members of a given group to anonymously sign messages on behalf of the group, producing a group signature. However, in the case of dispute the identity of the signature's originator can be revealed by a designated entity (group manager. The present paper describes the main concepts about group signatures, along with a brief state of the art and shows a personal cryptographic library implemented in Java that includes two group signatures.

  19. Working with Groups.

    Science.gov (United States)

    Morris, Joan, Ed.

    1984-01-01

    Describes nine Canadian programs for counseling groups of students. Topics include introducing computer-assisted guidance, future challenges for counselors, sociometry, sexuality, parent counseling, reluctant students, shyness, peer groups, education for living, and guidance advisory committees. (JAC)

  20. Group B streptococcus - pregnancy

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000511.htm Group B streptococcus - pregnancy To use the sharing features on this page, please enable JavaScript. Group B streptococcus (GBS) is a type of bacteria that ...

  1. Gestalt Interactional Groups

    Science.gov (United States)

    Harman, Robert L.; Franklin, Richard W.

    1975-01-01

    Gestalt therapy in groups is not limited to individual work in the presence of an audience. Describes several ways to involve gestalt groups interactionally. Interactions described focus on learning by doing and discovering, and are noninterpretive. (Author/EJT)

  2. Fast Overlapping Group Lasso

    CERN Document Server

    Liu, Jun

    2010-01-01

    The group Lasso is an extension of the Lasso for feature selection on (predefined) non-overlapping groups of features. The non-overlapping group structure limits its applicability in practice. There have been several recent attempts to study a more general formulation, where groups of features are given, potentially with overlaps between the groups. The resulting optimization is, however, much more challenging to solve due to the group overlaps. In this paper, we consider the efficient optimization of the overlapping group Lasso penalized problem. We reveal several key properties of the proximal operator associated with the overlapping group Lasso, and compute the proximal operator by solving the smooth and convex dual problem, which allows the use of the gradient descent type of algorithms for the optimization. We have performed empirical evaluations using the breast cancer gene expression data set, which consists of 8,141 genes organized into (overlapping) gene sets. Experimental results demonstrate the eff...

  3. Multicultural group work

    DEFF Research Database (Denmark)

    Hansen, Annette Skovsted

    2014-01-01

    Motivation for the activity I use this strategy for forming groups to ensure diverse/multicultural groups that combine a variety of different strengths and resources based on student's academic, disciplinary, linguistic, national, personal and work backgrounds.......Motivation for the activity I use this strategy for forming groups to ensure diverse/multicultural groups that combine a variety of different strengths and resources based on student's academic, disciplinary, linguistic, national, personal and work backgrounds....

  4. Generalized Group Signature Scheme

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The concept of generalized group signature scheme will bepresent. Based on the generalized secret sharing scheme proposed by Lin and Ha rn, a non-interactive approach is designed for realizing such generalized group signature scheme. Using the new scheme, the authorized subsets of the group in w hich the group member can cooperate to produce the valid signature for any messa ge can be randomly specified

  5. Groups, combinatorics and geometry

    CERN Document Server

    Ivanov, A A; Saxl, J

    2003-01-01

    Over the past 20 years, the theory of groups in particular simplegroups, finite and algebraic has influenced a number of diverseareas of mathematics. Such areas include topics where groups have beentraditionally applied, such as algebraic combinatorics, finitegeometries, Galois theory and permutation groups, as well as severalmore recent developments.

  6. Asymmetry within social groups

    DEFF Research Database (Denmark)

    Barker, Jessie; Loope, Kevin J.; Reeve, H. Kern

    2016-01-01

    Social animals vary in their ability to compete with group members over shared resources and also vary in their cooperative efforts to produce these resources. Competition among groups can promote within-group cooperation, but many existing models of intergroup cooperation do not explicitly account...

  7. Isotropy in group cohomology

    DEFF Research Database (Denmark)

    Ben David, Nir; Ginosar, Yuval; Meir, Ehud

    2014-01-01

    groups of central type from such quotients, known as Involutive Yang–Baxter groups. Another motivation for the search of normal Lagrangians comes from a non-commutative generalization of Heisenberg liftings that require normality. Although it is true that symplectic forms over finite nilpotent groups...

  8. Higher arithmetic Chow groups

    DEFF Research Database (Denmark)

    Gil, J. I. Burgos; Feliu, Elisenda

    2012-01-01

    We give a new construction of higher arithmetic Chow groups for quasi-projective arithmetic varieties over a field. Our definition agrees with the higher arithmetic Chow groups defined by Goncharov for projective arithmetic varieties over a field. These groups are the analogue, in the Arakelov co...

  9. CHAOTIC GROUP ACTIONS

    Institute of Scientific and Technical Information of China (English)

    ShiEnhui; ZhouLizhen; ZhouYoucheng

    2003-01-01

    It is proved that there is no chaotic group actions on any topological space with free arc.In this paper the chaotic actions of the group like G×F,where F is a finite group,are studied.In particular,under a suitable assumption ,if F is a cyclic group,then the topological space which admits a chaotic action of Z×F must admit a chatotic homeomorphism.A topological space which admits a chaotic group action but admits no chaotic horneomorphism is constructed.

  10. Grouped exposed metal heaters

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J [Bellaire, TX; Coit, William George [Bellaire, TX; Griffin, Peter Terry [Brixham, GB; Hamilton, Paul Taylor [Houston, TX; Hsu, Chia-Fu [Granada Hills, CA; Mason, Stanley Leroy [Allen, TX; Samuel, Allan James [Kular Lumpar, ML; Watkins, Ronnie Wade [Cypress, TX

    2012-07-31

    A system for treating a hydrocarbon containing formation is described. The system includes two or more groups of elongated heaters. The group includes two or more heaters placed in two or more openings in the formation. The heaters in the group are electrically coupled below the surface of the formation. The openings include at least partially uncased wellbores in a hydrocarbon layer of the formation. The groups are electrically configured such that current flow through the formation between at least two groups is inhibited. The heaters are configured to provide heat to the formation.

  11. Grouped exposed metal heaters

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J. (Bellaire, TX); Coit, William George (Bellaire, TX); Griffin, Peter Terry (Brixham, GB); Hamilton, Paul Taylor (Houston, TX); Hsu, Chia-Fu (Granada Hills, CA); Mason, Stanley Leroy (Allen, TX); Samuel, Allan James (Kular Lumpar, MY); Watkins, Ronnie Wade (Cypress, TX)

    2010-11-09

    A system for treating a hydrocarbon containing formation is described. The system includes two or more groups of elongated heaters. The group includes two or more heaters placed in two or more openings in the formation. The heaters in the group are electrically coupled below the surface of the formation. The openings include at least partially uncased wellbores in a hydrocarbon layer of the formation. The groups are electrically configured such that current flow through the formation between at least two groups is inhibited. The heaters are configured to provide heat to the formation.

  12. On -nilpotent abelian groups

    Indian Academy of Sciences (India)

    Mohammad Mehdi Nasrabadi; Ali Gholamian

    2014-11-01

    Let be a group and $A = \\text{Aut}(G)$ be the group of automorphisms of . Then, the element $[g, ] = g^{-1}(g)$ is an autocommutator of $g \\in G$ and $ \\in A$. Hence, for any natural number the -th autocommutator subgroup of is defined as $K_{m}(G)=\\langle [g,_{1},\\ldots,_{m}]|g\\in G,_{1},\\ldots,_{m}\\in A\\rangle$, where $[g, _{1}, _{2},\\ldots, _{m}] = [[g,_{1},\\ldots,_{m−1}], _{m}]$. In this paper, we introduce the new notion of -nilpotent groups and classify all abelian groups which are -nilpotent groups.

  13. Group I intron ribozymes

    DEFF Research Database (Denmark)

    Nielsen, Henrik

    2012-01-01

    Group I intron ribozymes constitute one of the main classes of ribozymes and have been a particularly important model in the discovery of key concepts in RNA biology as well as in the development of new methods. Compared to other ribozyme classes, group I intron ribozymes display considerable......, the intronic products of these pathways have the potential to integrate into targets and to form various types of circular RNA molecules. Thus, group I intron ribozymes and associated elements found within group I introns is a rich source of biological phenomena. This chapter provides a strategy and protocols...... for initial characterization of new group I intron ribozymes....

  14. Group theory I essentials

    CERN Document Server

    Milewski, Emil G

    2012-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Group Theory I includes sets and mapping, groupoids and semi-groups, groups, isomorphisms and homomorphisms, cyclic groups, the Sylow theorems, and finite p-groups.

  15. E-groups training

    CERN Multimedia

    HR Department

    2012-01-01

    There will be an e-groups training course on 16 March 2012 which will cover the main e-groups functionalities i.e.: creating and managing e-groups, difference between static and dynamic e-groups, configuring posting restrictions and archives, examples of where e-groups can be used in daily work. Even if you have already worked with e-groups, this may be a good opportunity to learn about the best practices and security related recommendations when using e-groups. You can find more details as well as enrolment form for the training (it’s free) here. The number of places is limited, so enrolling early is recommended.   Technical Training Tel. 72844

  16. Group Psychotherapy in Italy.

    Science.gov (United States)

    Giannone, Francesca; Giordano, Cecilia; Di Blasi, Maria

    2015-10-01

    This article describes the history and the prevailing orientations of group psychotherapy in Italy (psychoanalytically oriented, psychodrama, CBT groups) and particularly group analysis. Provided free of charge by the Italian health system, group psychotherapy is growing, but its expansion is patchy. The main pathways of Italian training in the different group psychotherapy orientations are also presented. Clinical-theoretical elaboration on self development, psychopathology related to group experiences, and the methodological attention paid to objectives and methods in different clinical groups are issues related to group therapy in Italy. Difficulties in the relationship between research and clinical practice are discussed, as well as the empirical research network that tries to bridge the gap between research and clinical work in group psychotherapy. The economic crisis in Italy has led to massive cuts in health care and to an increasing demand for some forms of psychological treatment. For these reasons, and because of its positive cost-benefit ratio, group psychotherapy is now considered an important tool in the national health care system to expand the clinical response to different forms of psychological distress.

  17. Stochastic Lie group integrators

    CERN Document Server

    Malham, Simon J A

    2007-01-01

    We present Lie group integrators for nonlinear stochastic differential equations with non-commutative vector fields whose solution evolves on a smooth finite dimensional manifold. Given a Lie group action that generates transport along the manifold, we pull back the stochastic flow on the manifold to the Lie group via the action, and subsequently pull back the flow to the corresponding Lie algebra via the exponential map. We construct an approximation to the stochastic flow in the Lie algebra via closed operations and then push back to the Lie group and then to the manifold, thus ensuring our approximation lies in the manifold. We call such schemes stochastic Munthe-Kaas methods after their deterministic counterparts. We also present stochastic Lie group integration schemes based on Castell--Gaines methods. These involve using an underlying ordinary differential integrator to approximate the flow generated by a truncated stochastic exponential Lie series. They become stochastic Lie group integrator schemes if...

  18. Blood groups systems

    Directory of Open Access Journals (Sweden)

    Ranadhir Mitra

    2014-01-01

    Full Text Available International Society of Blood Transfusion has recently recognized 33 blood group systems. Apart from ABO and Rhesus system, many other types of antigens have been noticed on the red cell membranes. Blood grouping and cross-matching is one of the few important tests that the anaesthesiologist orders during perioperative period. Hence, a proper understanding of the blood group system, their clinical significance, typing and cross-matching tests, and current perspective are of paramount importance to prevent transfusion-related complications. Nonetheless, the knowledge on blood group system is necessary to approach blood group-linked diseases which are still at the stage of research. This review addresses all these aspects of the blood groups system.

  19. Quantum isometry groups

    CERN Document Server

    Goswami, Debashish

    2016-01-01

    This book offers an up-to-date overview of the recently proposed theory of quantum isometry groups. Written by the founders, it is the first book to present the research on the “quantum isometry group”, highlighting the interaction of noncommutative geometry and quantum groups, which is a noncommutative generalization of the notion of group of isometry of a classical Riemannian manifold. The motivation for this generalization is the importance of isometry groups in both mathematics and physics. The framework consists of Alain Connes’ “noncommutative geometry” and the operator-algebraic theory of “quantum groups”. The authors prove the existence of quantum isometry group for noncommutative manifolds given by spectral triples under mild conditions and discuss a number of methods for computing them. One of the most striking and profound findings is the non-existence of non-classical quantum isometry groups for arbitrary classical connected compact manifolds and, by using this, the authors explicitl...

  20. Group Problem Solving

    CERN Document Server

    Laughlin, Patrick R

    2011-01-01

    Experimental research by social and cognitive psychologists has established that cooperative groups solve a wide range of problems better than individuals. Cooperative problem solving groups of scientific researchers, auditors, financial analysts, air crash investigators, and forensic art experts are increasingly important in our complex and interdependent society. This comprehensive textbook--the first of its kind in decades--presents important theories and experimental research about group problem solving. The book focuses on tasks that have demonstrably correct solutions within mathematical

  1. Definably amenable NIP groups

    OpenAIRE

    Chernikov, Artem; Simon, Pierre

    2015-01-01

    We study definably amenable NIP groups. We develop a theory of generics, showing that various definitions considered previously coincide, and study invariant measures. Applications include: characterization of regular ergodic measures, a proof of the conjecture of Petrykowski connecting existence of bounded orbits with definable amenability in the NIP case, and the Ellis group conjecture of Newelski and Pillay connecting the model-theoretic connected component of an NIP group with the ideal s...

  2. Semisimple Metacyclic Group Algebras

    Indian Academy of Sciences (India)

    Gurmeet K Bakshi; Shalini Gupta; Inder Bir S Passi

    2011-11-01

    Given a group of order $p_1p_2$, where $p_1,p_2$ are primes, and $\\mathbb{F}_q$, a finite field of order coprime to $p_1p_2$, the object of this paper is to compute a complete set of primitive central idempotents of the semisimple group algebra $\\mathbb{F}_q[G]$. As a consequence, we obtain the structure of $\\mathbb{F}_q[G]$ and its group of automorphisms.

  3. Presentations of groups

    CERN Document Server

    Johnson, D L

    1997-01-01

    The aim of this book is to provide an introduction to combinatorial group theory. Any reader who has completed first courses in linear algebra, group theory and ring theory will find this book accessible. The emphasis is on computational techniques but rigorous proofs of all theorems are supplied. This new edition has been revised throughout, including new exercises and an additional chapter on proving that certain groups are infinite.

  4. E-Group Arrangements

    Science.gov (United States)

    Aylesworth, Grant R.

    Group E at Uaxactún has long been considered an ancient Maya observatory in which an observer could see the sun rise along architectural alignments at the solstices and equinoxes. E-Groups named for the architectural complex list identified in Group E at Uaxactún, typically consist of a large radial pyramid on their west side and three temples on a raised platform on their east side.

  5. Diamictites and Sturtian Cap Dolomites Covering the Jacobina Group - Araras, North of Campo Formoso - Bahia

    Directory of Open Access Journals (Sweden)

    Augusto José de Cerqueira Lima Pedreira da Silva

    2008-10-01

    Full Text Available Occurrences of diamictites with a probable glacial origin underlying limestones north of Campo Formoso – BA around Araras village, had already been described by some authors during the 60´s and 70´s. Some of these occurrences have been recorded in some geological maps of 1/100,000 scales and even in others of smaller scales. The importance of these occurrences which have been studied in greater detail is increased because of the now identified litho-structural similarities (and probable stratigraphic correlation with those of Ituaçu, América Dourada, Morro do Chapéu (all of which overlie the ChapadaDiamantina Group, as well as with those in the northern part of the São Francisco Craton (Patamuté, Bendegó etc. overlying TTG rock units of the basement. For all these cases there is evidence of foreland tectonics associated to the centripetal vergence of the Neoproterozoic fold belts, marginal to the craton. There are some additional observations of these rock units occurring in the level of the “Sul-americana Surface”, thus demonstrating deep levels of erosion, which may be partially responsible for the present geographic separation of the whole original litho-stratigraphic context. Nevertheless it seems very clear that these records have somehow been sparsely distributed in the Cryogenian paleogeographic scenery, which may be an additional argument to contest the Snow Ball Earth theory. Some selected geological sections were undertaken in thesurroundings of Araras which made it possible to discriminate 4 types of litho-structural relationships between the Jacobina Group (Orosirian and the overlying diamictites of the São Francisco (Bebedouro Fm. Cryogenian.

  6. The Canastra Group in the type-area, Tapira region, southwest of Minas Gerais State, Brazil

    Directory of Open Access Journals (Sweden)

    Carlos Humberto da Silva

    2012-08-01

    Full Text Available This work aimed at describing the Neoproterozoic evolution of a Southern Brasília Fold Belt segment, in Tapira area(southwest of Minas Gerais state, Brazil, using detailed geologic mapping. This area, the Canastra Group type-area, hasshowed great tectonic and stratigraphic complexities unlike the simplicity suggested in previous works. From recognizingthe main tectonic discontinuities, it was possible to subdivide the area into some domains. In the west domain, they wereindividualized in tectonic sheet I, marked by pelitic rocks and pelitic-graphite rocks with psammitic intercalations, and II,pelitic rocks with psammitic and mafic-ultramafic intercalations overlapped by gneisses. In the east domain, a group ofthree tectonic sheets was defined, in which, in the two lower tectonic sheets, pelitic and pelitic-graphite rocks with psammiticrock intercalations prevailed, which is different in metamorphic conditions. The lower tectonic sheet is marked bymineralogical associations with muscovite + chlorite + quartz ± graphite ± albite, without biotite; however, the superior oneis with muscovite + quartz + garnet ± chlorite ± biotite ± chloritoid ± graphite ± albite. In the upper tectonic sheet, peliticrocks with local contributions of psammitic and ultramafics rocks occur. In the south domain, psammitic rocks basically occur with contributions of pelitics and rudaceous rocks, where the preservation of textures and sedimentary structures is common.Rocks of the several domains are interpreted as part of a passive continental margin basin, located in the western margin of the SãoFrancisco paleocontinent. Thus, the south domain rocks would represent the facies of proximal platform; rocks of the lower and middle tectonic sheets (east domain and of the tectonic sheet I (west domain are of facies distal platform; and the ones from the upper tectonic sheet (east domain and tectonic sheet II (west domain were acknowledged as deposited in an environment

  7. CLASSIFICATION OF CRIMINAL GROUPS

    Directory of Open Access Journals (Sweden)

    Natalia Romanova

    2013-06-01

    Full Text Available New types of criminal groups are emerging in modern society.  These types have their special criminal subculture. The research objective is to develop new parameters of classification of modern criminal groups, create a new typology of criminal groups and identify some features of their subculture. Research methodology is based on the system approach that includes using the method of analysis of documentary sources (materials of a criminal case, method of conversations with themembers of the criminal group, method of testing the members of the criminal group and method of observation. As a result of the conducted research, we have created a new classification of criminal groups. The first type is a lawful group in its form and criminal according to its content (i.e., its target is criminal enrichment. The second type is a criminal organization which is run by so-called "white-collars" that "remain in the shadow". The third type is traditional criminal groups.  The fourth type is the criminal group, which openly demonstrates its criminal activity.

  8. Explosive Technology Group

    Data.gov (United States)

    Federal Laboratory Consortium — The Explosive Technology Group (ETG) provides diverse technical expertise and an agile, integrated approach to solve complex challenges for all classes of energetic...

  9. Petrogenesis of keratophyes in the Pingshui Group,Zhejiang: Constraints from zircon U-Pb ages and Hf isotopes

    Institute of Scientific and Technical Information of China (English)

    CHEN ZhiHong; XING GuangFu; GUO KungaYi; DONG YongGuan; CHEN Rong; ZENG Yong; LI LongMing; HE ZhengYu; ZHAO Ling

    2009-01-01

    Zircon LA-ICP-MS U-Pb ages and Hf isotopic as well as whole-rock geochemical data are reported for keratophyes in the Pingshui Group, Zhejiang. The results are used to discuss their petrogenesis and geological significance. The keratophyes were dated at 904±8 to 906±10 Ma. These intermediate-felsic rocks are characterized by high LREE contents end depletion of HREE and HFSE (e.g., Nb, Ta, Ti, P), resembling arc-derived rocks. The keratophyes exhibit positive εHf(t) values of 8.6 to 15.4, consistent with their εNd(t) values of 6.4 to 7.9 but far away from those of crust-derived rocks. Such features indicate that they were likely originated from prompt reworking of juvenile crust by arc-continent collision during the early-Neoproterozoic assembly between the Cathaysia and Yangtze Blocks. Combining with their Hf model ages, we suggest that there may exist not only remarkable growth of juvenile crust at ca.1.3-1.1 Ga but also production of juvenile arc-derived crust along the southeastern margin of the Yangtze Block (e.g., the Pingshui area) at ca.1.0-0.9 Ga.

  10. CHINA INTERNATIONAL PUBLISHING GROUP

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The China International Publishing Group (CIPG) specializes in international communications. Its operationsencompass reporting, editing, translation, publishing, printing, distribution, and the Internet. It incorporates sevenpublishing companies, five magazines and 19 periodicals, published in over 20 languages. The ChinaInternational Book Trading Corporation, another group facet, distributes all of these to over 180 countries and

  11. Group Work. Research Brief

    Science.gov (United States)

    Walker, Karen

    2010-01-01

    According to Johnson and Johnson, group work helps increase student retention and satisfaction, develops strong oral communication and social skills, as well as higher self-esteem (University of Minnesota, n.d.). Group work, when planned and implemented deliberately and thoughtfully helps students develop cognitive and leadership skills as well as…

  12. Small Group Inquiry.

    Science.gov (United States)

    Koller, Martin M.

    Learning in small groups is a practical way to bring about behavior change. The inquiry learning process is perceived to be the most natural and scientific way of learning. Skills developed include those of problem-solving task analysis, decision-making, value formation and adaptability. The art of small group interaction is developed. Factual…

  13. Democratic Group Work

    Science.gov (United States)

    Laursen, Erik K.; Tate, Thomas F.

    2012-01-01

    For a century, democratic values have called for abandoning coercive approaches and teaching children and youth to be responsible citizens. The authors explore strategies for creating respectful environments and positive group cultures with challenging youth. They offer suggestions to adult group facilitators to support youth in developing…

  14. Study Groups in Denmark

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    2007-01-01

    Since 1998 European Study Groups have been held in Denmark, and Danish companies from LEGO and NOVO to very small high-tech firms have participated. I briefly describe the history, the organisation and the format of the Danish Study Groups, and highlight a few problem solutions....

  15. Fairness and Ability Grouping.

    Science.gov (United States)

    Strike, Kenneth A.

    1983-01-01

    A recent controversy regarding ability grouping is that it is often perceived as a means whereby racial or class bias can be subtly transformed into mechanisms of discrimination which exhibit the appearance of fairness and objectivity. This article addresses the question of fairness in ability grouping. (CJB)

  16. Automorphism groups of Quandles

    CERN Document Server

    Elhamdadi, M; Restrepo, R

    2010-01-01

    We prove that the automorphism group of the dihedral quandle with n elements is isomorphic to the affine group of the integers mod n, and also obtain the inner automorphism group of this quandle. In [9], automorphism groups of quandles (up to isomorphisms) of order less than or equal to 5 were given. With the help of the software Maple, we compute the inner and automorphism groups of all seventy three quandles of order six listed in the appendix of [4]. Since computations of automorphisms of quandles relates to the problem of classification of quandles, we also describe an algorithm implemented in C for computing all quandles (up to isomorphism) of order less than or equal to nine.

  17. Perceiving persons and groups.

    Science.gov (United States)

    Hamilton, D L; Sherman, S J

    1996-04-01

    This article analyzes the similarities and differences in forming impressions of individuals and in developing conceptions of groups. In both cases, the perceiver develops a mental conception of the target (individual or group) on the basis of available information and uses that information to make judgments about that person or group. However, a review of existing evidence reveals differences in the outcomes of impressions formed of individual and group targets, even when those impressions are based on the very same behavioral information. A model is proposed to account for these differences. The model emphasizes the role of differing expectancies of unity and coherence in individual and group targets, which in turn engage different mechanisms for processing information and making judgments. Implications of the model are discussed.

  18. Supervision and group dynamics

    DEFF Research Database (Denmark)

    Hansen, Søren; Jensen, Lars Peter

    2004-01-01

    as well as at Aalborg University. The first visible result has been participating supervisors telling us that the course has inspired them to try supervising group dynamics in the future. This paper will explore some aspects of supervising group dynamics as well as, how to develop the Aalborg model...... An important aspect of the problem based and project organized study at Aalborg University is the supervision of the project groups. At the basic education (first year) it is stated in the curriculum that part of the supervisors' job is to deal with group dynamics. This is due to the experience...... that many students are having difficulties with practical issues such as collaboration, communication, and project management. Most supervisors either ignore this demand, because they do not find it important or they find it frustrating, because they do not know, how to supervise group dynamics...

  19. LA-ICPMS zircon U-Pb geochronological constraints on the tectonothermal evolution of the Early Paleoproterozoic Dakendaban Group in the Quanji Block, NW China

    Institute of Scientific and Technical Information of China (English)

    WANG QinYan; CHEN NengSong; LI XiaoYan; HAO Shuang; CHEN HaiHong

    2008-01-01

    The Ouanji Block, situated between the northern margin of the Oaidam Block and the South Qilian orogenic belt in the NE Qinghai-Tibet Plateau, China, is thought to represent a remnant continental crust. In this study, LA-ICPMS U-Pb analyses of detrital zircon grains from two mesosomes in the migmatitic Dakendaban Group yield ages of 2467+281-26 Ma and 2474+66/-52 Ms, respectively. Zircon grains from a leucosome give two distinct ages of 2471+18/-16 Ma and 1924+14/-15 Ms. Zircon from a granitic pegmatite that intruded into the Dakendaban Group yields an age of 2427+44/-38 Ms. These data suggest that the Early Paleoproterozoic Dakendaban Group deposited between ~2.43 to ~2.47 Ga and has been subject to an intrusive event at 2.43 Ga, and regional metamorphism-anatexis at 1.92 Ga. The common lower intercept age of ~0.9 Ga probably records a significant Early Neoproterozoic event in the Quanji Block.

  20. Impedance group summary

    Science.gov (United States)

    Blaskiewicz, M.; Dooling, J.; Dyachkov, M.; Fedotov, A.; Gluckstern, R.; Hahn, H.; Huang, H.; Kurennoy, S.; Linnecar, T.; Shaposhnikova, E.; Stupakov, G.; Toyama, T.; Wang, J. G.; Weng, W. T.; Zhang, S. Y.; Zotter, B.

    1999-12-01

    The impedance working group was charged to reply to the following 8 questions relevant to the design of high-intensity proton machines such as the SNS or the FNAL driver. These questions were first discussed one by one in the whole group, then each ne of them assigned to one member to summarize. On the lst morning these contributions were publicly read, re-discussed and re-written where required—hence they are not the opinion of a particular person, but rather the averaged opinion of all members of the working group. (AIP)

  1. Building Bunk Group Buddies.

    Science.gov (United States)

    Nelson, Denise Cabrero

    2000-01-01

    Describes how camp counselors can foster camaraderie among campers through participative decision making, name games, listening, adventure courses, storytelling, spending time in nature, decorating cabins, avoiding favoritism, setting rules, admitting faults, setting group goals, and praising sincere efforts. (TD)

  2. Homogenous finitary symmetric groups

    Directory of Open Access Journals (Sweden)

    Otto‎. ‎H‎. Kegel

    2015-03-01

    Full Text Available We characterize strictly diagonal type of embeddings of finitary symmetric groups in terms of cardinality and the characteristic. Namely, we prove the following. Let kappa be an infinite cardinal. If G=underseti=1stackrelinftybigcupG i , where G i =FSym(kappan i , (H=underseti=1stackrelinftybigcupH i , where H i =Alt(kappan i , is a group of strictly diagonal type and xi=(p 1 ,p 2 ,ldots is an infinite sequence of primes, then G is isomorphic to the homogenous finitary symmetric group FSym(kappa(xi (H is isomorphic to the homogenous alternating group Alt(kappa(xi , where n 0 =1,n i =p 1 p 2 ldotsp i .

  3. Groups – Additive Notation

    Directory of Open Access Journals (Sweden)

    Coghetto Roland

    2015-06-01

    Full Text Available We translate the articles covering group theory already available in the Mizar Mathematical Library from multiplicative into additive notation. We adapt the works of Wojciech A. Trybulec [41, 42, 43] and Artur Korniłowicz [25].

  4. Homogeneous group, research, institution

    Directory of Open Access Journals (Sweden)

    Francesca Natascia Vasta

    2014-09-01

    Full Text Available The work outlines the complex connection among empiric research, therapeutic programs and host institution. It is considered the current research state in Italy. Italian research field is analyzed and critic data are outlined: lack of results regarding both the therapeutic processes and the effectiveness of eating disorders group analytic treatment. The work investigates on an eating disorders homogeneous group, led into an eating disorder outpatient service. First we present the methodological steps the research is based on including the strong connection among theory and clinical tools. Secondly clinical tools are described and the results commented. Finally, our results suggest the necessity of validating some more specifical hypothesis: verifying the relationship between clinical improvement (sense of exclusion and painful emotions reduction and specific group therapeutic processes; verifying the relationship between depressive feelings, relapses and transition trough a more differentiated groupal field.Keywords: Homogeneous group; Eating disorders; Institutional field; Therapeutic outcome

  5. Language and Group Identity.

    Science.gov (United States)

    Milroy, Leslie

    1982-01-01

    Explores the tension between the manner in which intergroup language differences are used to symbolize group membership and the manner in which they mirror and reinforce social class and power distinctions. (EKN)

  6. Radiation Protection Group

    CERN Multimedia

    2006-01-01

    The Radioactive Waste Section of the Radiation Protection Group wishes to inform you that the Radioactive Waste Treatment Centre will be closed on the afternoon of Tuesday 19 December 2006. Thank-you for your understanding.

  7. Parton Distributions Working Group

    Energy Technology Data Exchange (ETDEWEB)

    de Barbaro, L.; Keller, S. A.; Kuhlmann, S.; Schellman, H.; Tung, W.-K.

    2000-07-20

    This report summarizes the activities of the Parton Distributions Working Group of the QCD and Weak Boson Physics workshop held in preparation for Run II at the Fermilab Tevatron. The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, the authors introduce a Manifesto that describes an optimal method for reporting data.

  8. Networks and Small Groups

    OpenAIRE

    Kadushin, Charles

    2005-01-01

    Homans' insights that interaction and sentiment are in a feedback loop that includes clique formation, social ranking and leadership are formalized and derived from a set of limited assumptions and propositions. Freeman's model of groups is used to detect pure informal groups, those that are not consequential upon anything else than sheer hanging around. It produces a system of cliques and rankings based purely on the rates of transitive triads that may include a third who is only weakly conn...

  9. Fuzzy Soft Topological Groups

    Directory of Open Access Journals (Sweden)

    S. Nazmul

    2014-03-01

    Full Text Available Notions of Lowen type fuzzy soft topological space are introduced and some of their properties are established in the present paper. Besides this, a combined structure of a fuzzy soft topological space and a fuzzy soft group, which is termed here as fuzzy soft topological group is introduced. Homomorphic images and preimages are also examined. Finally, some definitions and results on fuzzy soft set are studied.

  10. Groups, rings, modules

    CERN Document Server

    Auslander, Maurice

    2014-01-01

    This classic monograph is geared toward advanced undergraduates and graduate students. The treatment presupposes some familiarity with sets, groups, rings, and vector spaces. The four-part approach begins with examinations of sets and maps, monoids and groups, categories, and rings. The second part explores unique factorization domains, general module theory, semisimple rings and modules, and Artinian rings. Part three's topics include localization and tensor products, principal ideal domains, and applications of fundamental theorem. The fourth and final part covers algebraic field extensions

  11. N-ary Groups

    CERN Document Server

    Gal'mak, Alexander M

    2011-01-01

    The book "N-ary Groups" (in Russian) consists of two Parts. It is intended on the one hand as an initial introduction to the theory of n-ary groups, and on the other hand it contains the published results by the author on this subject. At present, the theory of n-ary groups developing but slowly from group theory. Nonetheless, ternary and n-ary structures have recently been applied to modern models of elementary particle physics. One of the author's goals in this book is to draw the attention of mathematicians and theoretical physicists to the theory of n-ary groups, to some of its distinguishing features, and to details relevant to its further development and application. Part I: Theorems of Post and Gluskin-Hosszu. 1.1. Classical definitions of n-ary groups. Examples. 1.2. Analogies of identity and inverse elements. 1.3. Equivalent sequences. 1.4. Post's coset theorem. 1.5. Theorem of Gluskin-Hosszu. 1.6. Connection between the Post's coset theorem and theorem of Gluskin-Hosszu. Addition and comments. Part ...

  12. Ignimbritas riolíticas neoproterozoicas en la Sierra Norte de Córdoba: ¿evidencia de un arco magmático temprano en el ciclo Pampeano? Neoproterozoic rhyolite ignimbrites in the Sierra Norte de Córdoba: evidence of an early magmatic arc in the Pampean cycle?

    Directory of Open Access Journals (Sweden)

    EJ Llambías

    2003-12-01

    granodioritic and monzogranitic plutons of the Sierra Norte-Ambargasta batholtih, of Cambrian age. Dacitic to rhyolitic domes and dikes were intruded during the last stages of the batholith. In this paper we describe rhyolitic ignimbrite sheets within the metaconglomerates of the La Lidia Formation. The ignimbrites are moderately welded and consist of about 15 % of quartz, K-feldspar and entirely altered plagioclase porhyroclasts. Groundmass consists of devitrified glass shards. The conventional U/Pb zircon age is 584+22/-14 Ma and it is considered as the crystallization age. Very low grade metamorphism of the prehnite-pumpellyte facies altered the plagioclase to zoicite, sericite and pumpellyte. The Neoproterozoic silicic ignimbrites, together with the Cambrian calc-alkaline batholith and the related volcanics indicate the existence of a magmatic arc associated with the active margin of the Gondwana continent. This arc was active since Neoproterozoic times, with a duration of more than 60 Ma. Correlation of the Neoproterozoic metasedimentary and volcanics of Sierra Norte with the Puncoviscana Formation of Northwestern Argentina is considered.

  13. Inversión y reactivación tectónicas cretácicocenozoicas en el Noroeste Argentino: influencia de las heterogeneidades del basamento neoproterozoico-paleozoico inferior Cretaceous-Cenozoic tectonic inversion and reactivation in Northwestern Argentina: Influence of Neoproterozoic-Lower Paleozoic basement heterogeneities

    Directory of Open Access Journals (Sweden)

    Fernando Hongn

    2010-03-01

    Full Text Available Los rasgos estructurales del basamento neoproterozoico-paleozoico inferior (Cámbrico- Ordovícico del noroeste argentino han controlado en diferentes grados el desarrollo de las estructuras posteriores, principalmente las vinculadas con la extensión cretácica y el acortamiento andino. La inversión tectónica de fallas normales relacionadas con el rift cretácico ha sido frecuentemente invocada entre los mecanismos que influyen en la definición de las zonas de doble vergencia y retrovergencia que muestra el orógeno andino en el noroeste argentino. En esta contribución proponemos que las estructuras del basamento jugaron un papel primario en la localización tanto de las fallas normales cretácicas posteriormente reactivadas como de las fallas inversas andinas. Una sección estructural regional entre la Cordillera de Domeyko (Chile y el Sistema de Santa Bárbara (aproximadamente 24º-25ºLS muestra segmentos con vergencias cenozoicas opuestas, en la que cada porción responde a diferentes controles ejercidos por estructuras previas. La inversión de fallas normales asociadas a sistemas de rift fue el principal control de la geometría y vergencia de las estructuras cenozoicas vinculadas al acortamiento andino en la Cordillera de Domeyko, en los Valles Calchaquíes y en el Sistema de Santa Bárbara. La reactivación de las estructuras y heterogeneidades originadas durante la evolución neoproterozoico-paleozoica del basamento controlaron el desarrollo de las estructuras cenozoicas en la Puna. La reactivación de las heterogeneidades no sólo influyó en los cambios de orientación y vergencia, sino también en la distribución temporal compleja que muestra el acortamiento andino. La reactivación múltiple de algunas estructuras del basamento neoproterozoico-paleozoico inferior ocurrió en diferentes etapas de su historia incluyendo inversiones positivas y negativas entre el Cretácico y el Cuaternario.The Neoproterozoic-Lower Paleozoic

  14. 中国辽吉地区新元古代臼齿碳酸盐岩中分子化石及早期生命演化%Molecular Fossils in Neoproterozoic Molar Tooth Carbonates from Liaoning and Jilin Provinces, China and Discussion on the Evolution of Early Life

    Institute of Scientific and Technical Information of China (English)

    李艳霞; 旷红伟

    2012-01-01

    臼齿碳酸盐岩是指具有类似大象臼齿特征并具有肠状褶皱构造的元古宙微亮晶碳酸盐岩,其成因众说纷纭.首次对分布于中国吉辽地区新元古代震旦纪(0.65~0.81 Ga)的臼齿碳酸盐岩可溶有机抽提物进行了研究,从中发现了大量的分子生物化石——生物标志物,诸如正构烷烃、无环类异戊二烯烷烃、烷基环己烷、长侧链三环萜烷、藿烷、伽马蜡烷、甾烷等;同时对各类生物标志物的先体生物进行了详尽的生物门类归属,并对早期的原始生命的演化进行了深入的分析.其分子化石研究表明,MT灰岩中含有大量的原核生物细菌(蓝细菌)、古细菌(硫细菌、甲烷菌)、真核生物藻类(蓝藻、绿藻、褐藻、红藻)、真菌及原生动物.毫无疑问,臼齿构造的形成离不开生物活动的参与;同时也说明元古宙原始生物已演化到一个相当高级的程度,已蕴含埃迪卡拉纪的第一次生物大爆发.%Molar-tooth carbonates (briefly called MT or microsparite carbonates) are characterized by early diagenetic sedimentary features. The term of 'Molar-tooth' is named after their tapered, ptygmatically folded texture which are mainly developed in Mesoproterozoic and Neoproterozoic carbonates. The origin of these enigmatic structures have been argued. The authors investigated the MT carbonates from Simian (0. 65 -0. 81 Ga) of Neoproterozoic Era in Liaoning and Jilin Provinces of China. A series of biomarkers found from the extracted bitumens of MT carbonates include n-alkanes, alkyl cyclohexanes, acyclic isoprenoids alkanes, extended tricyclic trepans, hopanes, gammacerane, steranes. Furthermore, their biological precursors of these hydrocarbon class are discussed particularly based on the distribution of boilipids in extant organisms. The results show that MT carbonates contain a lot of Prokaryote bacteria ( oxygenic photosynthesis cyanobacteria), Archaebacteria (sulfur bacteria

  15. Coordinating Group report

    Energy Technology Data Exchange (ETDEWEB)

    1994-01-01

    In December 1992, western governors and four federal agencies established a Federal Advisory Committee to Develop On-site Innovative Technologies for Environmental Restoration and Waste Management (the DOIT Committee). The purpose of the Committee is to advise the federal government on ways to improve waste cleanup technology development and the cleanup of federal sites in the West. The Committee directed in January 1993 that information be collected from a wide range of potential stakeholders and that innovative technology candidate projects be identified, organized, set in motion, and evaluated to test new partnerships, regulatory approaches, and technologies which will lead to improve site cleanup. Five working groups were organized, one to develop broad project selection and evaluation criteria and four to focus on specific contaminant problems. A Coordinating Group comprised of working group spokesmen and federal and state representatives, was set up to plan and organize the routine functioning of these working groups. The working groups were charged with defining particular contaminant problems; identifying shortcomings in technology development, stakeholder involvement, regulatory review, and commercialization which impede the resolution of these problems; and identifying candidate sites or technologies which could serve as regional innovative demonstration projects to test new approaches to overcome the shortcomings. This report from the Coordinating Group to the DOIT Committee highlights the key findings and opportunities uncovered by these fact-finding working groups. It provides a basis from which recommendations from the DOIT Committee to the federal government can be made. It also includes observations from two public roundtables, one on commercialization and another on regulatory and institutional barriers impeding technology development and cleanup.

  16. Facilities removal working group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    This working group`s first objective is to identify major economic, technical, and regulatory constraints on operator practices and decisions relevant to offshore facilities removal. Then, the group will try to make recommendations as to regulatory and policy adjustments, additional research, or process improvements and/or technological advances, that may be needed to improve the efficiency and effectiveness of the removal process. The working group will focus primarily on issues dealing with Gulf of Mexico platform abandonments. In order to make the working group sessions as productive as possible, the Facilities Removal Working Group will focus on three topics that address a majority of the concerns and/or constraints relevant to facilities removal. The three areas are: (1) Explosive Severing and its Impact on Marine Life, (2) Pile and Conductor Severing, and (3) Deep Water Abandonments This paper will outline the current state of practice in the offshore industry, identifying current regulations and specific issues encountered when addressing each of the three main topics above. The intent of the paper is to highlight potential issues for panel discussion, not to provide a detailed review of all data relevant to the topic. Before each panel discussion, key speakers will review data and information to facilitate development and discussion of the main issues of each topic. Please refer to the attached agenda for the workshop format, key speakers, presentation topics, and panel participants. The goal of the panel discussions is to identify key issues for each of the three topics above. The working group will also make recommendations on how to proceed on these key issues.

  17. Linear algebraic groups

    CERN Document Server

    Springer, T A

    1998-01-01

    "[The first] ten chapters...are an efficient, accessible, and self-contained introduction to affine algebraic groups over an algebraically closed field. The author includes exercises and the book is certainly usable by graduate students as a text or for self-study...the author [has a] student-friendly style… [The following] seven chapters... would also be a good introduction to rationality issues for algebraic groups. A number of results from the literature…appear for the first time in a text." –Mathematical Reviews (Review of the Second Edition) "This book is a completely new version of the first edition. The aim of the old book was to present the theory of linear algebraic groups over an algebraically closed field. Reading that book, many people entered the research field of linear algebraic groups. The present book has a wider scope. Its aim is to treat the theory of linear algebraic groups over arbitrary fields. Again, the author keeps the treatment of prerequisites self-contained. The material of t...

  18. The Multiplication Group of an AG-group

    OpenAIRE

    Shah, Muhammad; Ali, Asif; Ahmad, Imtiaz; Sorge, Volker

    2014-01-01

    We investigate the multiplication group of a special class of quasigroup called AG-group. We prove some interesting results such as: the multiplication group of an AG-group of order n is non-abelian group of order 2n and its left section is an abelian group of order n. The inner mapping group of an AG-group of any order is a cyclic group of order 2.

  19. Illinois Wind Workers Group

    Energy Technology Data Exchange (ETDEWEB)

    David G. Loomis

    2012-05-28

    The Illinois Wind Working Group (IWWG) was founded in 2006 with about 15 members. It has grown to over 200 members today representing all aspects of the wind industry across the State of Illinois. In 2008, the IWWG developed a strategic plan to give direction to the group and its activities. The strategic plan identifies ways to address critical market barriers to the further penetration of wind. The key to addressing these market barriers is public education and outreach. Since Illinois has a restructured electricity market, utilities no longer have a strong control over the addition of new capacity within the state. Instead, market acceptance depends on willing landowners to lease land and willing county officials to site wind farms. Many times these groups are uninformed about the benefits of wind energy and unfamiliar with the process. Therefore, many of the project objectives focus on conferences, forum, databases and research that will allow these stakeholders to make well-educated decisions.

  20. Doing focus group research

    DEFF Research Database (Denmark)

    Lindegaard, Laura Bang

    2014-01-01

    , not as something that pre-exists or goes beyond the situated interaction. This article, however, challenges not only the first, but also the second position and suggests that it is, after all, possible to do committedly ethnomethodological studies of focus group data that demonstrate how members of a focus group......Scholars of ethnomethodologically informed discourse studies are often sceptical of the use of interview data such as focus group data. Some scholars quite simply reject interview data with reference to a general preference for so-called naturally occurring data. Other scholars acknowledge...... of interview interaction, but inadequate as data for studying phenomena that go beyond the phenomenon of interview interaction. Neither of these more and less sceptical positions are, on the face of it, surprising due to the ethnomethodological commitment to study social order as accomplished in situ...

  1. Quantum threshold group signature

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t-1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t-1 or fewer receivers cannot verify the validity of the signature.

  2. Transitive conformal holonomy groups

    CERN Document Server

    Alt, Jesse

    2011-01-01

    For $(M,[g])$ a conformal manifold of signature $(p,q)$ and dimension at least three, the conformal holonomy group $\\mathrm{Hol}(M,[g]) \\subset O(p+1,q+1)$ is an invariant induced by the canonical Cartan geometry of $(M,[g])$. We give a description of all possible connected conformal holonomy groups which act transitively on the M\\"obius sphere $S^{p,q}$, the homogeneous model space for conformal structures of signature $(p,q)$. The main part of this description is a list of all such groups which also act irreducibly on $\\R^{p+1,q+1}$. For the rest, we show that they must be compact and act decomposably on $\\R^{p+1,q+1}$, in particular, by known facts about conformal holonomy the conformal class $[g]$ must contain a metric which is locally isometric to a so-called special Einstein product.

  3. Focus group discussions

    CERN Document Server

    Hennink, Monique M

    2014-01-01

    The Understanding Research series focuses on the process of writing up social research. The series is broken down into three categories: Understanding Statistics, Understanding Measurement, and Understanding Qualitative Research. The books provide researchers with guides to understanding, writing, and evaluating social research. Each volume demonstrates how research should be represented, including how to write up the methodology as well as the research findings. Each volume also reviews how to appropriately evaluate published research. Focus Group Discussions addresses the challenges associated with conducting and writing focus group research. It provides detailed guidance on the practical and theoretical considerations in conducting focus group discussions including: designing the discussion guide, recruiting participants, training a field team, moderating techniques and ethical considerations. Monique Hennink describes how a methodology section is read and evaluated by others, such as journal reviewers or ...

  4. GroupFinder

    DEFF Research Database (Denmark)

    Bøgh, Kenneth Sejdenfaden; Skovsgaard, Anders; Jensen, Christian S.

    2013-01-01

    of PoIs relevant to a user's intent has became a problem of automated spatio-textual information retrieval. Over the last several years, substantial research has gone into the invention of functionality and efficient implementations for retrieving nearby PoIs. However, with a couple of exceptions....... Such groups are relevant to users who wish to conveniently explore several options before making a decision such as to purchase a specific product. Specifically, we demonstrate a practical proposal for finding top-k PoI groups in response to a query. We show how problem parameter settings can be mapped...

  5. Group theory and chemistry

    CERN Document Server

    Bishop, David M

    1993-01-01

    Group theoretical principles are an integral part of modern chemistry. Not only do they help account for a wide variety of chemical phenomena, they simplify quantum chemical calculations. Indeed, knowledge of their application to chemical problems is essential for students of chemistry. This complete, self-contained study, written for advanced undergraduate-level and graduate-level chemistry students, clearly and concisely introduces the subject of group theory and demonstrates its application to chemical problems.To assist chemistry students with the mathematics involved, Professor Bishop ha

  6. Homomorphisms between Kaehler groups

    CERN Document Server

    Arapura, Donu

    2009-01-01

    This is partly a survey and partly a research article. Some known results and open problems about Kaehler groups (fundamental groups of compact Kaehler manifolds) are discussed. A new notion of Kaehler homomorphism is introduced. This is a homomorphism induced by a holomorphic map between these types of manifolds. Some obstructions for a homomorphism to be Kaehler are discussed. Among these is the main result on the vanishing of a certain cohomology class associated to such map. This is reduced to the decomposition theorem for perverse sheaves suitably extended to Kaehler orbifolds.

  7. Fourier Analysis on Groups

    CERN Document Server

    Rudin, Walter

    2011-01-01

    In the late 1950s, many of the more refined aspects of Fourier analysis were transferred from their original settings (the unit circle, the integers, the real line) to arbitrary locally compact abelian (LCA) groups. Rudin's book, published in 1962, was the first to give a systematic account of these developments and has come to be regarded as a classic in the field. The basic facts concerning Fourier analysis and the structure of LCA groups are proved in the opening chapters, in order to make the treatment relatively self-contained.

  8. Group Based Interference Alignment

    CERN Document Server

    Ma, Yanjun; Chen, Rui; Yao, Junliang

    2010-01-01

    in $K$-user single-input single-output (SISO) frequency selective fading interference channels, it is shown that the achievable multiplexing gain is almost surely $K/2$ by using interference alignment (IA). However when the signaling dimensions is limited, allocating all the resource to all the users simultaneously is not optimal. According to this problem, a group based interference alignment (GIA) scheme is proposed and a search algorithm is designed to get the group patterns and the resource allocation among them. Analysis results show that our proposed scheme achieves a higher multiplexing gain when the resource is limited.

  9. Upgraded Coal Interest Group

    Energy Technology Data Exchange (ETDEWEB)

    Evan Hughes

    2009-01-08

    The Upgraded Coal Interest Group (UCIG) is an EPRI 'users group' that focuses on clean, low-cost options for coal-based power generation. The UCIG covers topics that involve (1) pre-combustion processes, (2) co-firing systems and fuels, and (3) reburn using coal-derived or biomass-derived fuels. The UCIG mission is to preserve and expand the economic use of coal for energy. By reducing the fuel costs and environmental impacts of coal-fired power generation, existing units become more cost effective and thus new units utilizing advanced combustion technologies are more likely to be coal-fired.

  10. FAW Group Gorporation

    Institute of Scientific and Technical Information of China (English)

    Yan Feng

    2007-01-01

    @@ As the founder of China's automobile industry, FAW Group Corporation (FAW) has maintained a dominant position in the automotive industry since its founding in 1953 in terms of its total assets, Production capacity, domestic and international sales, market share, and brand recognition.

  11. Group theory in physics

    CERN Document Server

    Cornwell, J F

    1989-01-01

    Recent devopments, particularly in high-energy physics, have projected group theory and symmetry consideration into a central position in theoretical physics. These developments have taken physicists increasingly deeper into the fascinating world of pure mathematics. This work presents important mathematical developments of the last fifteen years in a form that is easy to comprehend and appreciate.

  12. Leukosis/Sarcoma Group

    Science.gov (United States)

    The leukosis/sarcoma (L/S) group of diseases designates a variety of transmissible benign and malignant neoplasms of chickens caused by members that belong to the family Retroviridae. Because the expansion of the literature on this disease, it is no longer feasible to cite all relevant publications ...

  13. Dimensions of Group Interaction

    Science.gov (United States)

    Dawidowicz, Paula

    2008-01-01

    The correlation between positive and negative group interactions and one or another of individuals' attitudes or characteristics--moral development, critical thinking, resilience, and self efficacy--has been examined previously. However, no systemic examination of individuals' development of patterns of these characteristics and those patterns'…

  14. Working Group Report: Neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    de Gouvea, A.; Pitts, K.; Scholberg, K.; Zeller, G. P. [et al.

    2013-10-16

    This document represents the response of the Intensity Frontier Neutrino Working Group to the Snowmass charge. We summarize the current status of neutrino physics and identify many exciting future opportunities for studying the properties of neutrinos and for addressing important physics and astrophysics questions with neutrinos.

  15. Grouping Illumination Frameworks

    Science.gov (United States)

    Zdravkovic, Suncica; Economou, Elias; Gilchrist, Alan

    2012-01-01

    According to Koffka (1935), the lightness of a target surface is determined by the relationship between the target and the illumination frame of reference to which it belongs. However, each scene contains numerous illumination frames, and judging each one separately would lead to an enormous amount of computing. Grouping those frames that are in…

  16. Convolution Operators on Groups

    CERN Document Server

    Derighetti, Antoine

    2011-01-01

    This volume is devoted to a systematic study of the Banach algebra of the convolution operators of a locally compact group. Inspired by classical Fourier analysis we consider operators on Lp spaces, arriving at a description of these operators and Lp versions of the theorems of Wiener and Kaplansky-Helson.

  17. With the Radiobiology Group

    CERN Multimedia

    1980-01-01

    The Radiobiology Group carries out experiments to study the effect of radiation on living cells. The photo shows the apparatus for growing broad beans which have been irradiated by 250 GeV protons. The roots are immersed in a tank of running water (CERN Weekly Bulletin 26 January 1981 and Annual Report 1980 p. 160). Karen Panman, Marilena Streit-Bianchi, Roger Paris.

  18. Group B Streptococcus

    Directory of Open Access Journals (Sweden)

    Albert H. Adriaanse

    1995-01-01

    Full Text Available Objective: Group B streptococcus (GBS, Streptococcus agalactiae is an important cause of neonatal sepsis. Prevention is possible by intrapartum screening for maternal GBS carriership and antimicrobial treatment of colonized women with risk factors during labor. The conflicting results of diagnostic performance are reported both for the newly developed rapid GBS antigen tests and Gram's stain.

  19. Abandoning wells working group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The primary objective of this working group is to identify major technical, regulatory, and environmental issues that are relevant to the abandonment of offshore wellbores. Once the issues have been identified, the working group also has the objective of making recommendations or providing potential solutions for consideration. Areas for process improvement will be identified and {open_quotes}best practices{close_quotes} will be discussed and compared to {open_quotes}minimum standards.{close_quotes} The working group will primarily focus on wellbore abandonment in the Gulf of Mexico. However, workshop participants are encouraged to discuss international issues which may be relevant to wellbore abandonment practices in the Gulf of Mexico. The Abandoning Wells Group has identified several major areas for discussion that have concerns related to both operators and service companies performing wellbore abandonments in the Gulf of Mexico. The following broad topics were selected for the agenda: (1) MMS minimum requirements and state regulations. (2) Co-existence of best practices, new technology, and P & A economics. (3) Liability and environmental issues relating to wellbore abandonment.

  20. NEW MATERIALS OF PHOSPHATIZED CYLINDRICAL AND TABULATE MICROFOSSILS FROM THE NEOPROTEROZOIC DOUSHANTUO FORMATION AT WENG'AN, GUIZHOU, SOUTH CHINA%贵州瓮安新元古代陡山沱组磷酸盐化管柱状微体化石新材料

    Institute of Scientific and Technical Information of China (English)

    李勇; 张兴亮; 郭俊峰; 丁莲芳; 韩健; 舒德干

    2003-01-01

    在用醋酸浸泡处理采自贵州瓮安新元古代陡山沱组磷酸质岩石样品时,获得大量微体动物骨骼化石.文中重点报道部分管柱状微体化石,即:Sinoquadraticus poratus gen. et sp. nov.和 Sinoquadraticus wenganensis gen. et sp. nov..并对Sinocyclocylicus的部分特征进行补充.%In 1992 Xue et al. reported some skeletal fossils, including one genus and two species, from the Neoprotorozoic Doushantuo Formation at Weng'an, Guizhou, and assigned them to Echinodermata. In this paper, new materials of phosphatized cylindrical and tabulate microfossils, including a new genus and two new species, are described from the same layer and locality. It provides us much more evidence not only to display the Neoproterozoic biodiversity, but also to explore the origin and the early evolution of biomineralization.

  1. Los esquistos neoproterozoicos de Santa Helena, Provincia de La Pampa, Argentina: edades u-pb shrimp, composición isotópica de hafnio e implicancias geodinámicas The Neoproterozoic Santa Elena Schists, La Pampa Province, Argentina: SHRIMP U-Pb ages, Hf isotope composition and geodynamic implications

    Directory of Open Access Journals (Sweden)

    Eduardo O Zappetini

    2010-03-01

    , equivalente al magmatismo precolisional de los orógenos Juruena y Sunsas, se habría acrecionado al borde sudoccidental del cratón del Río de la Plata y formaría parte actualmente del sustrato de su borde paleoproterozoico sudoccidental y del sustrato del terreno para-autóctono Pampia. Este mecanismo acrecional sería similar al observado en otros núcleos cratónicos arqueanos-paleoproterozoicos, tales como los de Amazonas, Kalahari y Congo. Finalmente, la otra fuente importante de aporte de los Esquistos Santa Helena indica la existencia de una faja de rocas magmáticas neoproterozoicas que correspondería a un arco desarrollado sobre el margen oriental de Pampia.The Santa Helena Schists comprise biotite-garnet schists and minor sillimanite-garnet gneissoid lenses, reaching the higher amphibolite to lower granulite facies metamorphism . Suboutcrops of the schists occur at Estancia Santa Helena. U-Pb SHRIMP dating of the Santa Elena Schists detrital zircon yielded mostly Mesoproterozoic and Neoproterozoic ages, with a small number of Paleoproterozoic grains. Almost all the Mesoproterozoic and Neoproterozoic grains are magmatic and crystallized from a juvenile source (positive εHf, with TDM (Hf ranging 1127 to 1625 Ma, and 948 to 1274 Ma, respectively. The Paleoproterozoic zircons are also magmatic, with a TDM (Hf of 2310 Ma. The age of the youngest detrital zircon is 556 Ma, which corresponds to the maximum age for the onset of sedimentation, indicating that deposition probably started by Neoproterozoic times. The absolute absence of metamorphic zircons of Pampean age suggests that during the time of deposition of the schists, the metamorphic nucleous of the Pampean orogen was still not formed and exposed. This implies a great contrast with the provenance pattern of the nearby Green Schists, dominated by Cambrian metamorphic zircons, deposited between ca. 500 Ma and ca. 465 Ma, when the Pampean orogen was already exhumed and subject to denudation. It is interpreted

  2. The Ombudperson Initiative Group

    CERN Multimedia

    Laura Stewart

    Following many discussions that took place at some of the ATLAS Women's Network lunch gatherings, a few ATLAS women joined forces with similarly concerned CERN staff women to form a small group last Fall to discuss the need for a CERN-wide Ombudsperson. This has since evolved into the Ombudsperson Initiative Group (OIG) currently composed of the following members: Barbro Asman, Stockholm University; Pierre Charrue, CERN AB; Anna Cook, CERN IT; Catherine Delamare, CERN and IT Ombudsperson; Paula Eerola, Lund University; Pauline Gagnon, Indiana University; Eugenia Hatziangeli, CERN AB; Doreen Klem, CERN IT; Bertrand Nicquevert, CERN TS and Laura Stewart, CERN AT. On June 12, members of the OIG met with representatives of Human Resources (HR) and the Equal Opportunity Advisory Panel (EOAP) to discuss the proposal drafted by the OIG. The meeting was very positive. Everybody agreed that the current procedures at CERN applicable in the event of conflict required a thorough review, and that a professionnally trai...

  3. Gravitation Gauge Group

    CERN Document Server

    Ter-Kazarian, G T

    1997-01-01

    Suggested theory involves a drastic revision of a role of local internal symmetries in physical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski to Riemannian space a standard gauge principle of local internal symmetries is generalized. The gravitation gauge group is proposed, which is generated by hidden local internal symmetries. The developed mechanism enables one to infer Einstein's equation of gravitation, but only with strong difference from Einstein's theory at the vital point of well-defined energy-momentum tensor of gravitational field and conservation laws. The gravitational interaction as well as general distortion of manifold G(2.2.3) with hidden group U(1) was considered.

  4. Group and representation theory

    CERN Document Server

    Vergados, J D

    2017-01-01

    This volume goes beyond the understanding of symmetries and exploits them in the study of the behavior of both classical and quantum physical systems. Thus it is important to study the symmetries described by continuous (Lie) groups of transformations. We then discuss how we get operators that form a Lie algebra. Of particular interest to physics is the representation of the elements of the algebra and the group in terms of matrices and, in particular, the irreducible representations. These representations can be identified with physical observables. This leads to the study of the classical Lie algebras, associated with unitary, unimodular, orthogonal and symplectic transformations. We also discuss some special algebras in some detail. The discussion proceeds along the lines of the Cartan-Weyl theory via the root vectors and root diagrams and, in particular, the Dynkin representation of the roots. Thus the representations are expressed in terms of weights, which are generated by the application of the elemen...

  5. Group Leaders Optimization Algorithm

    CERN Document Server

    Daskin, Anmer

    2010-01-01

    Complexity of global optimization algorithms makes implementation of the algorithms difficult and leads the algorithms to require more computer resources for the optimization process. The ability to explore the whole solution space without increasing the complexity of algorithms has a great importance to not only get reliable results but so also make the implementation of these algorithms more convenient for higher dimensional and complex-real world problems in science and engineering. In this paper, we present a new global optimization algorithm in which the influence of the leaders in social groups is used as an inspiration for the evolutionary technique that is designed into a group architecture similar to the architecture of Cooperative Coevolutionary Algorithms. Therefore, we present the implementation method and the experimental results for the single and multidimensional optimization test problems and a scientific real world problem, the energies and the geometric structures of Lennard-Jones clusters.

  6. Mindfulness for group facilitation

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine; Krohn, Simon

    2014-01-01

    In this paper, we argue that mindfulness techniques can be used for enhancing the outcome of group performance. The word mindfulness has different connotations in the academic literature. Broadly speaking there is ‘mindfulness without meditation’ or ‘Western’ mindfulness which involves active...... thinking and ‘Eastern’ mindfulness which refers to an open, accepting state of mind, as intended with Buddhist-inspired techniques such as meditation. In this paper, we are interested in the latter type of mindfulness and demonstrate how Eastern mindfulness techniques can be used as a tool for facilitation....... A brief introduction to the physiology and philosophy of Eastern mindfulness constitutes the basis for the arguments of the effect of mindfulness techniques. The use of mindfulness techniques for group facilitation is novel as it changes the focus from individuals’ mindfulness practice...

  7. Communication from ST Group

    CERN Multimedia

    TS Department

    2008-01-01

    Please note that owing the preparations for the Open Days, the FM Group will not able to handle specific requests for waste collection from 2nd to 6th of April, nor removal or PC transport requests between the 31 March and 11 April. We kindly ask you to plan the collection of all types of waste and any urgent transport of office furniture or PCs before 31 March. Waste collection requests must be made by contacting FM Support on 77777 or at the e-mail address mailto:Fm.Support@cern.ch; removal of office furniture or PC transport requests must be made using the EDH ‘Transport request’ form (select "Removals" or "PC transport" from the drop-down menu). For any question concerning the sorting of waste, please consult the following web site: http://dechets-waste.web.cern.ch/dechets-waste/ Thank you for your understanding and collaboration. TS/FM Group

  8. Combinatorial group theory

    CERN Document Server

    Lyndon, Roger C

    2001-01-01

    From the reviews: "This book (...) defines the boundaries of the subject now called combinatorial group theory. (...)it is a considerable achievement to have concentrated a survey of the subject into 339 pages. This includes a substantial and useful bibliography; (over 1100 ÄitemsÜ). ...the book is a valuable and welcome addition to the literature, containing many results not previously available in a book. It will undoubtedly become a standard reference." Mathematical Reviews, AMS, 1979.

  9. Mixed carbonate-siliciclastic sedimentation in forebulge grabens: An example from the Ediacaran Bambuí Group, São Francisco Basin, Brazil

    Science.gov (United States)

    Reis, Humberto L. S.; Suss, João F.

    2016-06-01

    Mixed carbonate-siliciclastic successions have been described in multiple Phanerozoic sedimentary settings recording the dynamic interplay of tectonics, eustasy, climate, in situ carbonate production, and variations in siliciclastic sediment supply. The Ediacaran Bambuí 1st-order sequence (i.e., Bambuí Group) covers most of the intracratonic São Francisco basin (southeast Brazil) and encompasses thick packages of carbonate and fine- to coarse-grained siliciclastic strata. Recording a marine foreland basin stage that developed in the São Francisco plate during the Neoproterozoic-early Paleozoic West Gondwana assembly, the Ediacaran deposits unconformably overlie Archean-Paleoproterozoic metamorphic assemblages of the Sete Lagoas basement high and fill a series of kilometer-long grabens in the southern São Francisco basin. Seismic data reveal that these troughs developed through the extensional reactivation of ancient basement structures along with the tectonically driven forebulge uplift of the Sete Lagoas high, in the early evolutionary stages of the Bambuí basin cycle. Based on the detailed description of continuous drill cores of a well recently drilled during hydrocarbon exploration campaigns, we recognized two transgressive-regressive 2nd-order sequences preserved within one of the focused grabens: (i) Sequence 1 includes the glaciogenic deposits of the basal Carrancas Formation that grade upward into the carbonate ramp successions of the Sete Lagoas Formation; (ii) Sequence 2 contains the siliciclastic-dominated and deep water to deltaic strata of the Serra de Santa Helena Formation and passes upward into peritidal carbonates of the Lagoa do Jacaré Formation. These sedimentary successions encompass suites of retrogradational, aggradational, and progradational lower-rank cycles and are bounded by erosional surfaces. Regional seismic interpretation, well data, and the available literature indicate that most of these deposits and their correlatives are

  10. Group Variables and Gaming Success.

    Science.gov (United States)

    Norris, Dwight R.; Niebuhr, Robert E.

    1980-01-01

    Describes a study designed to determine the effects of group cohesiveness on group performance in a management game and, to examine the effects voluntary v assigned group membership has on the cohesiveness of the group. (Author/LLS)

  11. Finite groups with transitive semipermutability

    Institute of Scientific and Technical Information of China (English)

    Lifang WANG; Yanming WANG

    2008-01-01

    A group G is said to be a T-group (resp. PT-group, PST-group), if normality (resp. permutability, S-permutability) is a transitive relation. In this paper, we get the characterization of finite solvable PST-groups. We also give a new characterization of finite solvable PT-groups.

  12. Statistical Group Comparison

    CERN Document Server

    Liao, Tim Futing

    2011-01-01

    An incomparably useful examination of statistical methods for comparisonThe nature of doing science, be it natural or social, inevitably calls for comparison. Statistical methods are at the heart of such comparison, for they not only help us gain understanding of the world around us but often define how our research is to be carried out. The need to compare between groups is best exemplified by experiments, which have clearly defined statistical methods. However, true experiments are not always possible. What complicates the matter more is a great deal of diversity in factors that are not inde

  13. Social group utility maximization

    CERN Document Server

    Gong, Xiaowen; Yang, Lei; Zhang, Junshan

    2014-01-01

    This SpringerBrief explains how to leverage mobile users' social relationships to improve the interactions of mobile devices in mobile networks. It develops a social group utility maximization (SGUM) framework that captures diverse social ties of mobile users and diverse physical coupling of mobile devices. Key topics include random access control, power control, spectrum access, and location privacy.This brief also investigates SGUM-based power control game and random access control game, for which it establishes the socially-aware Nash equilibrium (SNE). It then examines the critical SGUM-b

  14. Notes on quantum groups

    Energy Technology Data Exchange (ETDEWEB)

    Pressley, A.; Chari, V. (King' s Coll., London (UK). Dept. of Mathematics Tata Inst. of Fundamental Research, Bombay (India). School of Mathematics)

    1990-12-01

    The authors presents an introduction to quantum groups defined as a deformation of the universal enveloping algebra of a Lie algebra. After the description of Hopf algebras with some examples the approach of Drinfel'd and Jimbo is described, where the quantization of a Lie algebra represents a Hopf algebra, defined over the algebra of formal power series in an indetermined h. The authors show that this approach arises from a r-matrix, which satisfies the classical Yang-Baxter equation. As example quantum sl{sub 2} is considered. Furthermore the approaches of Manin and Woroniwicz and the R-matrix approach are described. (HSI).

  15. Groups and symmetry

    CERN Document Server

    Farmer, David W

    1995-01-01

    In most mathematics textbooks, the most exciting part of mathematics-the process of invention and discovery-is completely hidden from the reader. The aim of Groups and Symmetry is to change all that. By means of a series of carefully selected tasks, this book leads readers to discover some real mathematics. There are no formulas to memorize; no procedures to follow. The book is a guide: Its job is to start you in the right direction and to bring you back if you stray too far. Discovery is left to you. Suitable for a one-semester course at the beginning undergraduate level, there are no prerequ

  16. STEAM GENERATOR GROUP PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Clark, R. A.; Lewis, M

    1985-09-01

    This report is a summary of progress in the Surry Steam Generator Group Project for 1984. Information is presented on the analysis of two baseline eddy current inspections of the generator. Round robin series of tests using standard in-service inspection techniques are described along with some preliminary results. Observations are reported of degradation found on tubing specimens removed from the generator, and on support plates characterized in-situ. Residual stresses measured on a tubing specimen are reported. Two steam generator repair demonstrations are described; one for antivibration bar replacement, and one on tube repair methods. Chemical analyses are shown for sludge samples removed from above the tube sheet.

  17. Applications of Quantum Groups

    Science.gov (United States)

    Chryssomalakos, Chryssomalis

    The main theme of this thesis is the search for applications of Quantum Group and Hopf algebraic concepts and techniques in Physics. We investigate in particular the possibilities that exist in deforming, in a self consistent way, the symmetry structure of physical theories with the hope that the resulting scheme will be of relevance in the description of physical reality. Our choice of topics reflects this motivation: we discuss deformations of rotations and Lorentz boosts, search for integrals on the quantum plane and attempt to Fourier transform functions of non -commuting coordinates. Along the way, more formal considerations prompt us to revisit integration on finite dimensional Hopf algebras, explore the interconnections between various descriptions of the quantum double and derive the algebraic structure of the quantum plane from that of the underlying deformed symmetry group. The material is structured as follows. Chapter 1 introduces the language, basic concepts and notation employed throughout this thesis. Chapter 2 focuses on Hopf algebras viewed as universal envelopes of deformed Lie algebras and their duals. Bicovariant generators enter the discussion as analogues of the classical Lie algebra generators and some of their properties are given. We comment on the geometrical interpretation of the algebraic formulation and introduce computational tools. In chapter 3 we take a close look at the quantum Lorentz Hopf algebra. The basics of complex quantum groups are presented and applied in the derivation of the algebra of the quantum Lorentz generators and its Hopf and involutive structures. We point also to isomorphisms with previous related constructions. The subject of quantum integration is explored in chapter 4. We derive a formula for the integral on a finite dimensional Hopf algebra and show its equivalence to the formulation in terms of the trace of the square of the antipode. Integration on the quantum plane is also examined and a Fourier transform

  18. Finite Symplectic Matrix Groups

    OpenAIRE

    2011-01-01

    The finite subgroups of GL(m, Q) are those subgroups that fix a full lattice in Q^m together with some positive definite symmetric form. A subgroup of GL(m, Q) is called symplectic, if it fixes a nondegenerate skewsymmetric form. Such groups only exist if m is even. A symplectic subgroup of GL(2n, Q) is called maximal finite symplectic if it is not properly contained in some finite symplectic subgroup of GL(2n, Q). This thesis classifies all conjugacy classes of maximal finite symplectic subg...

  19. Outer automorphism groups of certain 1-relator groups

    Institute of Scientific and Technical Information of China (English)

    KIM; Goansu

    2010-01-01

    Grossman first showed that outer automorphism groups of 1-relator groups given by orientable surface groups are residually finite,whence mapping class groups of orientable surfaces are residually finite.Allenby,Kim and Tang showed that outer automorphism groups of cyclically pinched 1-relator groups are residually finite,whence mapping class groups of orientable and non-orientable surfaces are residually finite.In this paper we show that outer automorphism groups of certain conjugacy separable 1-relator groups are residually finite.

  20. Gravitation gauge group

    Energy Technology Data Exchange (ETDEWEB)

    Ter-Kazarian, G. T. [Byurakan Astrophysical Observatory (Armenia)

    1997-06-01

    The suggested theory involves a drastic revision of the role of local internal symmetries in the physical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski to Riemannian space a standard gauge principle of local internal symmetries has been generalized. A gravitation gauge group is proposed, which is generated by hidden local internal symmetries. In all circumstances, it seemed to be of the greatest importance for the understanding of the physical nature of gravity. The most promising aspect in their approach so far is the fact that the energy-momentum conservation laws of gravitational interacting fields are formulated quite naturally by exploiting all the advantages of auxiliary shadow fields on flat shadow space. The mechanism developed here enables one to infer Einstein`s equation of gravitation, but only with a strong difference from Einstein`s theory at the vital point of well-defined energy-momentum tensor of gravitational field and conservation laws. The gravitational interaction as well as the general distortion of the manifold G(2.2.3) with hidden group U{sup loc} (1) has been considered.

  1. Social group and mobbing

    Directory of Open Access Journals (Sweden)

    Baltezarević Vesna

    2009-01-01

    Full Text Available Our reality, having been subject to the numerous social crises during the last decades of the 20th century, is characterized by frequent incidences of powerlessness and alienation. The man is more frequently a subject to loneliness and overcomes the feeling of worthlessness, no matter whether he considers himself an individual or a part of a whole larger social. Such an environment leads to development of aggression in all fields of ones life. This paper has as an objective the pointing out of the mental harassment that is manifested in the working environment. There is a prevalence of mobbing cases, as a mode of pathological communication. The result of this is that a person, subjected to this kind of abuse, is soon faced with social isolation. This research also aspires to initiate the need for social groups self-organization of which victims are part of. The reaction modality of a social group directly conditions the outcome of the deliberate social drama, one is subjected to it as a result of mobbing.

  2. AO Group Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, S

    2005-10-04

    The Adaptive Optics (AO) Group in I Division develops and tests a broad range of advanced wavefront control technologies. Current applications focus on: Remote sensing, High power lasers, Astronomy, and Human vision. In the area of remote sensing, the AO Group leads a collaborative effort with LLNL's Nonproliferation, Arms Control & International Security (NAI) Directorate on Enhanced Surveillance Imaging. The ability to detect and identify individual people or vehicles from long-range is an important requirement for proliferation detection and homeland security. High-resolution imaging along horizontal paths through the atmosphere is limited by turbulence, which blurs and distorts the image. For ranges over {approx}one km, visible image resolution can be reduced by over an order of magnitude. We have developed an approach based on speckle imaging that can correct the turbulence-induced blurring and provide high resolution imagery. The system records a series of short exposure images which freeze the atmospheric effects. We can then estimate the image magnitude and phase using a bispectral estimation algorithm which cancels the atmospheric effects while maintaining object information at the diffraction limit of the imaging system.

  3. Communication from ST Group

    CERN Multimedia

    TS Department

    2008-01-01

    In order to prepare the organization of the Open Days, please note that FM Group will not able to take into account either specific requests for waste collection from 2nd to 6th of April, either removal or PC transport requests between the 31st and the 11th of March. We kindly ask you to plan the collection of any type of waste and the urgent transport of office furniture or PC before the 31st of March. Waste collection requests shall be formulated contacting FM Support at 77777 or at the email address mailto:Fm.Support@cern.ch; removal of office furniture or PC transport requests must be made using the EDH ‘Transport request’ form selecting the "Removals" or the "PC transport" category from the drop-down menu. For any question concerning the waste sorting, please consult the following web address: http://dechets-waste.web.cern.ch/dechets-waste/. Thank you for your understanding and collaboration. TS/FM Group

  4. ATLAS Detector Interface Group

    CERN Multimedia

    Mapelli, L

    Originally organised as a sub-system in the DAQ/EF-1 Prototype Project, the Detector Interface Group (DIG) was an information exchange channel between the Detector systems and the Data Acquisition to provide critical detector information for prototype design and detector integration. After the reorganisation of the Trigger/DAQ Project and of Technical Coordination, the necessity to provide an adequate context for integration of detectors with the Trigger and DAQ lead to organisation of the DIG as one of the activities of Technical Coordination. Such an organisation emphasises the ATLAS wide coordination of the Trigger and DAQ exploitation aspects, which go beyond the domain of the Trigger/DAQ project itself. As part of Technical Coordination, the DIG provides the natural environment for the common work of Trigger/DAQ and detector experts. A DIG forum for a wide discussion of all the detector and Trigger/DAQ integration issues. A more restricted DIG group for the practical organisation and implementation o...

  5. Group Life Insurance

    CERN Multimedia

    2013-01-01

    The CERN Administration would like to remind you that staff members and fellows have the possibility to take out a life insurance contract on favourable terms through a Group Life Insurance.   This insurance is provided by the company Helvetia and is available to you on a voluntary basis. The premium, which varies depending on the age and gender of the person insured, is calculated on the basis of the amount of the death benefit chosen by the staff member/fellow and can be purchased in slices of 10,000 CHF.    The contract normally ends at the retirement age (65/67 years) or when the staff member/fellow leaves the Organization. The premium is deducted monthly from the payroll.   Upon retirement, the staff member can opt to maintain his membership under certain conditions.   More information about Group Life Insurance can be found at: Regulations (in French) Table of premiums The Pension Fund Benefit Service &...

  6. Emotional collectives : How groups shape emotions and emotions shape groups

    NARCIS (Netherlands)

    van Kleef, G.A.; Fischer, A.H.

    2016-01-01

    Group settings are epicentres of emotional activity. Yet, the role of emotions in groups is poorly understood. How do group-level phenomena shape group members’ emotional experience and expression? How are emotional expressions recognised, interpreted and shared in group settings? And how do such ex

  7. Representation Theory of Algebraic Groups and Quantum Groups

    CERN Document Server

    Gyoja, A; Shinoda, K-I; Shoji, T; Tanisaki, Toshiyuki

    2010-01-01

    Invited articles by top notch expertsFocus is on topics in representation theory of algebraic groups and quantum groupsOf interest to graduate students and researchers in representation theory, group theory, algebraic geometry, quantum theory and math physics

  8. Graphs, groups and surfaces

    CERN Document Server

    White, AT

    1985-01-01

    The field of topological graph theory has expanded greatly in the ten years since the first edition of this book appeared. The original nine chapters of this classic work have therefore been revised and updated. Six new chapters have been added, dealing with: voltage graphs, non-orientable imbeddings, block designs associated with graph imbeddings, hypergraph imbeddings, map automorphism groups and change ringing.Thirty-two new problems have been added to this new edition, so that there are now 181 in all; 22 of these have been designated as ``difficult'''' and 9 as ``unsolved''''. Three of the four unsolved problems from the first edition have been solved in the ten years between editions; they are now marked as ``difficult''''.

  9. Working Group Report: Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Artuso, M.; et al.,

    2013-10-18

    Sensors play a key role in detecting both charged particles and photons for all three frontiers in Particle Physics. The signals from an individual sensor that can be used include ionization deposited, phonons created, or light emitted from excitations of the material. The individual sensors are then typically arrayed for detection of individual particles or groups of particles. Mounting of new, ever higher performance experiments, often depend on advances in sensors in a range of performance characteristics. These performance metrics can include position resolution for passing particles, time resolution on particles impacting the sensor, and overall rate capabilities. In addition the feasible detector area and cost frequently provides a limit to what can be built and therefore is often another area where improvements are important. Finally, radiation tolerance is becoming a requirement in a broad array of devices. We present a status report on a broad category of sensors, including challenges for the future and work in progress to solve those challenges.

  10. Grouping Notes Through Nodes

    DEFF Research Database (Denmark)

    Dove, Graham; Abildgaard, Sille Julie Jøhnk; Biskjær, Michael Mose

    The Post-ItTM note is a frequently used, and yet seldom studied, design material. We investigate the functions Post-ItTM notes serve when providing cognitive support for creative design team practice. Our investigation considers the ways in which Post-ItTM notes function as design externalisations......, both individually and when grouped, and their role in categorisation in semantic long-term memory. To do this, we adopt a multimodal analytical approach focusing on interaction between humans, and between humans and artefacts, alongside language. We discuss in detail examples of four different...... externalisation functions served by Post-ItTM notes, and show how these functions are present in complex overlapping combinations rather than being discrete. We then show how the temporal development of Post-ItTM note interactions supports categorisation qualities of semantic long-term memory....

  11. Grouping Synonyms by Definitions

    CERN Document Server

    Falk, Ingrid; Jacquey, Evelyne; Venant, Fabienne

    2009-01-01

    We present a method for grouping the synonyms of a lemma according to its dictionary senses. The senses are defined by a large machine readable dictionary for French, the TLFi (Tr\\'esor de la langue fran\\c{c}aise informatis\\'e) and the synonyms are given by 5 synonym dictionaries (also for French). To evaluate the proposed method, we manually constructed a gold standard where for each (word, definition) pair and given the set of synonyms defined for that word by the 5 synonym dictionaries, 4 lexicographers specified the set of synonyms they judge adequate. While inter-annotator agreement ranges on that task from 67% to at best 88% depending on the annotator pair and on the synonym dictionary being considered, the automatic procedure we propose scores a precision of 67% and a recall of 71%. The proposed method is compared with related work namely, word sense disambiguation, synonym lexicon acquisition and WordNet construction.

  12. Renormalization Group Therapy

    CERN Document Server

    Tomboulis, E T

    2007-01-01

    We point out a general problem with the procedures commonly used to obtain improved actions from MCRG decimated configurations. Straightforward measurement of the couplings from the decimated configurations, by one of the known methods, can result into actions that do not correctly reproduce the physics on the undecimated lattice. This is because the decimated configurations are generally not representative of the equilibrium configurations of the assumed form of the effective action at the measured couplings. Curing this involves fine-tuning of the chosen MCRG decimation procedure, which is also dependent on the form assumed for the effective action. We illustrate this in decimation studies of the SU(2) LGT using Swendsen and Double Smeared Blocking decimation procedures. A single-plaquette improved action involving five group representations and free of this pathology is given.

  13. Gutzwiller renormalization group

    Science.gov (United States)

    Lanatà, Nicola; Yao, Yong-Xin; Deng, Xiaoyu; Wang, Cai-Zhuang; Ho, Kai-Ming; Kotliar, Gabriel

    2016-01-01

    We develop a variational scheme called the "Gutzwiller renormalization group" (GRG), which enables us to calculate the ground state of Anderson impurity models (AIM) with arbitrary numerical precision. Our method exploits the low-entanglement property of the ground state of local Hamiltonians in combination with the framework of the Gutzwiller wave function and indicates that the ground state of the AIM has a very simple structure, which can be represented very accurately in terms of a surprisingly small number of variational parameters. We perform benchmark calculations of the single-band AIM that validate our theory and suggest that the GRG might enable us to study complex systems beyond the reach of the other methods presently available and pave the way to interesting generalizations, e.g., to nonequilibrium transport in nanostructures.

  14. NOSS science working group

    Science.gov (United States)

    The members of the NOSS Science Working Group are John Apel, Pacific Marine Environmental Laboratories/NOAA; Tim Barnett, Scripps Institution of Oceanography; Francis Bretherton (chairman), National Center for Atmospheric Research; Otis Brown, University of Miami; Joost Businger, University of Washington; Garrett Campbell, NCAR; Mark Cane, Massachusetts Institute of Technology; Robert Edwards, National Marine Fisheries Service/NOAA; James Mueller, Naval Postgraduate School; Peter Niiler, Oregon State University; James J. O'Brien, Florida State University; Norman Phillips, National Meteorological Center/NOAA; Owen Phillips, The Johns Hopkins University; Stephen Piacsek, NSTL Station, NORDA; Trevor Platt, Bedford Institute of Oceanography; Stephen Pond, University of British Columbia; Stanley Ruttenberg (executive secretary), NCAR; William Schmitz, Woods Hole Oceanographic Institution; Jerry Schubel, State University of New York; Robert Stewart, Scripps; Norbert Untersteiner, NOAA; and Alan Weinstein, Naval Environmental Prediction Research Facility.

  15. Group life insurance

    CERN Multimedia

    2013-01-01

    The CERN Administration wishes to inform staff members and fellows having taken out optional life insurance under the group contract signed by CERN that the following changes to the rules and regulations entered into force on 1 January 2013:   The maximum age for an active member has been extended from 65 to 67 years. The beneficiary clause now allows insured persons to designate one or more persons of their choice to be their beneficiary(-ies), either at the time of taking out the insurance or at a later date, in which case the membership/modification form must be updated accordingly. Beneficiaries must be clearly identified (name, first name, date of birth, address).   The membership/modification form is available on the FP website: http://fp.web.cern.ch/helvetia-life-insurance For further information, please contact: Valentina Clavel (Tel. 73904) Peggy Pithioud (Tel. 72736)

  16. The Automorphism Groups of the Groups of Order 32p

    CERN Document Server

    Becker, Elaine W

    2009-01-01

    The results of computer computations determining the automorphism groups of the groups of order 32$p$ for $p \\geq 3$ are given in several tables. Presentations for the automorphism groups of the groups of order 32, which in many cases appear as direct product factors in the automorphism groups of order $32p$, are also presented for completeness. Many of the groups of order 32$p$ with a normal sylow $p$-subgroup have automorphism groups of the form: Hol($C_p$)$ \\times $Invariant Factor. A suggestion is made as to how one might determine this invariant factor using only information on the automorphism group of the 2-group associated with the group of order 32$p$, and the normal subgroup of the 2-group associated with the extension of the group of order $32p$. Some general comments on the groups of order $32p^2$ and their automorphism groups are made. A few explicit calculations for the groups of order $32p^2$ are reported here. Knowing the automorphism groups for the groups of order $32p$ enables us to explicit...

  17. Group B Streptococcus and Pregnancy

    Science.gov (United States)

    ... B Strep and Pregnancy • What is group B streptococcus (GBS)? • What does it mean to be colonized ... planned cesarean birth? •Glossary What is group B streptococcus (GBS)? Group B streptococcus is one of the ...

  18. The analytic renormalization group

    Science.gov (United States)

    Ferrari, Frank

    2016-08-01

    Finite temperature Euclidean two-point functions in quantum mechanics or quantum field theory are characterized by a discrete set of Fourier coefficients Gk, k ∈ Z, associated with the Matsubara frequencies νk = 2 πk / β. We show that analyticity implies that the coefficients Gk must satisfy an infinite number of model-independent linear equations that we write down explicitly. In particular, we construct "Analytic Renormalization Group" linear maps Aμ which, for any choice of cut-off μ, allow to express the low energy Fourier coefficients for |νk | < μ (with the possible exception of the zero mode G0), together with the real-time correlators and spectral functions, in terms of the high energy Fourier coefficients for |νk | ≥ μ. Operating a simple numerical algorithm, we show that the exact universal linear constraints on Gk can be used to systematically improve any random approximate data set obtained, for example, from Monte-Carlo simulations. Our results are illustrated on several explicit examples.

  19. Cluster functional renormalization group

    Science.gov (United States)

    Reuther, Johannes; Thomale, Ronny

    2014-01-01

    Functional renormalization group (FRG) has become a diverse and powerful tool to derive effective low-energy scattering vertices of interacting many-body systems. Starting from a free expansion point of the action, the flow of the RG parameter Λ allows us to trace the evolution of the effective one- and two-particle vertices towards low energies by taking into account the vertex corrections between all parquet channels in an unbiased fashion. In this work, we generalize the expansion point at which the diagrammatic resummation procedure is initiated from a free UV limit to a cluster product state. We formulate a cluster FRG scheme where the noninteracting building blocks (i.e., decoupled spin clusters) are treated exactly, and the intercluster couplings are addressed via RG. As a benchmark study, we apply our cluster FRG scheme to the spin-1/2 bilayer Heisenberg model (BHM) on a square lattice where the neighboring sites in the two layers form the individual two-site clusters. Comparing with existing numerical evidence for the BHM, we obtain reasonable findings for the spin susceptibility, the spin-triplet excitation energy, and quasiparticle weight even in coupling regimes close to antiferromagnetic order. The concept of cluster FRG promises applications to a large class of interacting electron systems.

  20. Harmonic Analysis and Group Representation

    CERN Document Server

    Figa-Talamanca, Alessandro

    2011-01-01

    This title includes: Lectures - A. Auslander, R. Tolimeri - Nilpotent groups and abelian varieties, M Cowling - Unitary and uniformly bounded representations of some simple Lie groups, M. Duflo - Construction de representations unitaires d'un groupe de Lie, R. Howe - On a notion of rank for unitary representations of the classical groups, V.S. Varadarajan - Eigenfunction expansions of semisimple Lie groups, and R. Zimmer - Ergodic theory, group representations and rigidity; and, Seminars - A. Koranyi - Some applications of Gelfand pairs in classical analysis.

  1. Group Leader Development: Effects of Personal Growth and Psychoeducational Groups

    Science.gov (United States)

    Ohrt, Jonathan H.; Robinson, E. H., III; Hagedorn, W. Bryce

    2013-01-01

    The purpose of this quasi-experimental study was to compare the effects of personal growth groups and psychoeducational groups on counselor education students' (n = 74) empathy and group leader self-efficacy. Additionally, we compared the degree to which participants in each group valued: (a) cohesion, (b) catharsis, and (c) insight. There were no…

  2. Interagency Advanced Power Group -- Steering group meeting minutes

    Energy Technology Data Exchange (ETDEWEB)

    1993-11-18

    This document contains the draft meeting minutes of the Steering Group of the Interagency Advanced Power Group. Included are the discussions resulting from the presentation of working group reports and the results of a discussion of IAPG policies and procedures. In the appendix are the reports of the following working groups: Electrical, Mechanical, Solar, and Systems.

  3. On the Central Automorphism Groups of Finite p-Groups

    Institute of Scientific and Technical Information of China (English)

    Ali-Reza Jamali; Hamid Mousavi

    2002-01-01

    Using the concept of isoclinism, we study closely the center of the group Autc(G) of central automorphisms for a certain class of finite p-groups G.We also give some necessary and sufficient conditions on a finite purely non-abelian p-group G of class 2 (p odd) for the group Autc(G) to be elementary abelian.

  4. Post-Disaster Social Justice Group Work and Group Supervision

    Science.gov (United States)

    Bemak, Fred; Chung, Rita Chi-Ying

    2011-01-01

    This article discusses post-disaster group counseling and group supervision using a social justice orientation for working with post-disaster survivors from underserved populations. The Disaster Cross-Cultural Counseling model is a culturally responsive group counseling model that infuses social justice into post-disaster group counseling and…

  5. Abstract Lie groups and locally compact topological groups

    Directory of Open Access Journals (Sweden)

    Jacek Lech

    2004-05-01

    Full Text Available We introduce a notion of abstract Lie group by means of the mapping which plays the role of the evolution operator. We show some basic properties of such groups very similar to the fundamentals of the infinite dimensional Lie theory. Next we give remarkable examples of abstract Lie groups which are not necessarily usual Lie groups. In particular, by making use of Yamabe theorem we prove that any locally compact topological group admits the structure of abstract Lie group and that the Lie algebra and the exponential mapping of it coincide with those determined by the Lie group structure.

  6. Emotional collectives: How groups shape emotions and emotions shape groups.

    Science.gov (United States)

    van Kleef, Gerben A; Fischer, Agneta H

    2016-01-01

    Group settings are epicentres of emotional activity. Yet, the role of emotions in groups is poorly understood. How do group-level phenomena shape group members' emotional experience and expression? How are emotional expressions recognised, interpreted and shared in group settings? And how do such expressions influence the emotions, cognitions and behaviours of fellow group members and outside observers? To answer these and other questions, we draw on relevant theoretical perspectives (e.g., intergroup emotions theory, social appraisal theory and emotions as social information theory) and recent empirical findings regarding the role of emotions in groups. We organise our review according to two overarching themes: how groups shape emotions and how emotions shape groups. We show how novel empirical approaches break important new ground in uncovering the role of emotions in groups. Research on emotional collectives is thriving and constitutes a key to understanding the social nature of emotions.

  7. Fermilab Steering Group Report

    Energy Technology Data Exchange (ETDEWEB)

    Steering Group, Fermilab; /Fermilab

    2007-12-01

    The Fermilab Steering Group has developed a plan to keep U.S. accelerator-based particle physics on the pathway to discovery, both at the Terascale with the LHC and the ILC and in the domain of neutrinos and precision physics with a high-intensity accelerator. The plan puts discovering Terascale physics with the LHC and the ILC as Fermilab's highest priority. While supporting ILC development, the plan creates opportunities for exciting science at the intensity frontier. If the ILC remains near the Global Design Effort's technically driven timeline, Fermilab would continue neutrino science with the NOvA experiment, using the NuMI (Neutrinos at the Main Injector) proton plan, scheduled to begin operating in 2011. If ILC construction must wait somewhat longer, Fermilab's plan proposes SNuMI, an upgrade of NuMI to create a more powerful neutrino beam. If the ILC start is postponed significantly, a central feature of the proposed Fermilab plan calls for building an intense proton facility, Project X, consisting of a linear accelerator with the currently planned characteristics of the ILC combined with Fermilab's existing Recycler Ring and the Main Injector accelerator. The major component of Project X is the linac. Cryomodules, radio-frequency distribution, cryogenics and instrumentation for the linac are the same as or similar to those used in the ILC at a scale of about one percent of a full ILC linac. Project X's intense proton beams would open a path to discovery in neutrino science and in precision physics with charged leptons and quarks. World-leading experiments would allow physicists to address key questions of the Quantum Universe: How did the universe come to be? Are there undiscovered principles of nature: new symmetries, new physical laws? Do all the particles and forces become one? What happened to the antimatter? Building Project X's ILC-like linac would offer substantial support for ILC development by accelerating the

  8. Fermilab Steering Group Report

    Energy Technology Data Exchange (ETDEWEB)

    Beier, Eugene; /Pennsylvania U.; Butler, Joel; /Fermilab; Dawson, Sally; /Brookhaven; Edwards, Helen; /Fermilab; Himel, Thomas; /SLAC; Holmes, Stephen; /Fermilab; Kim, Young-Kee; /Fermilab /Chicago U.; Lankford, Andrew; /UC, Irvine; McGinnis, David; /Fermilab; Nagaitsev, Sergei; /Fermilab; Raubenheimer, Tor; /SLAC /Fermilab

    2007-01-01

    The Fermilab Steering Group has developed a plan to keep U.S. accelerator-based particle physics on the pathway to discovery, both at the Terascale with the LHC and the ILC and in the domain of neutrinos and precision physics with a high-intensity accelerator. The plan puts discovering Terascale physics with the LHC and the ILC as Fermilab's highest priority. While supporting ILC development, the plan creates opportunities for exciting science at the intensity frontier. If the ILC remains near the Global Design Effort's technically driven timeline, Fermilab would continue neutrino science with the NOVA experiment, using the NuMI (Neutrinos at the Main Injector) proton plan, scheduled to begin operating in 2011. If ILC construction must wait somewhat longer, Fermilab's plan proposes SNuMI, an upgrade of NuMI to create a more powerful neutrino beam. If the ILC start is postponed significantly, a central feature of the proposed Fermilab plan calls for building an intense proton facility, Project X, consisting of a linear accelerator with the currently planned characteristics of the ILC combined with Fermilab's existing Recycler Ring and the Main Injector accelerator. The major component of Project X is the linac. Cryomodules, radio-frequency distribution, cryogenics and instrumentation for the linac are the same as or similar to those used in the ILC at a scale of about one percent of a full ILC linac. Project X's intense proton beams would open a path to discovery in neutrino science and in precision physics with charged leptons and quarks. World-leading experiments would allow physicists to address key questions of the Quantum Universe: How did the universe come to be? Are there undiscovered principles of nature: new symmetries, new physical laws? Do all the particles and forces become one? What happened to the antimatter? Building Project X's ILC-like linac would offer substantial support for ILC development by accelerating the

  9. ON COLEMAN OUTER AUTOMORPHISM GROUPS OF FINITE GROUPS

    Institute of Scientific and Technical Information of China (English)

    海进科; 李正兴

    2014-01-01

    Let G be a finite group and OutCol(G) the Coleman outer automorphism group of G(for the definition, see below). The question whether OutCol(G) is a p′-group naturally arises from the study of the normalizer problem for integral group rings, where p is a prime. In this article, some sufficient conditions for OutCol(G) to be a p′-group are obtained. Our results generalize some well-known theorems.

  10. Anomaly-safe discrete groups

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mu-Chun, E-mail: muchunc@uci.edu [Department of Physics and Astronomy, University of California, Irvine, CA 92697-4575 (United States); Fallbacher, Maximilian, E-mail: m.fallbacher@tum.de [Physik–Department T30, Technische Universität München, James–Franck–Straße 1, 85748 Garching (Germany); Ratz, Michael, E-mail: michael.ratz@tum.de [Physik–Department T30, Technische Universität München, James–Franck–Straße 1, 85748 Garching (Germany); Trautner, Andreas, E-mail: andreas.trautner@tum.de [Physik–Department T30, Technische Universität München, James–Franck–Straße 1, 85748 Garching (Germany); Excellence Cluster Universe, Boltzmannstraße 2, 85748 Garching (Germany); Vaudrevange, Patrick K.S., E-mail: patrick.vaudrevange@tum.de [Excellence Cluster Universe, Boltzmannstraße 2, 85748 Garching (Germany); TUM Institute for Advanced Study, Lichtenbergstraße 2a, 85748 Garching (Germany); Arnold Sommerfeld Center for Theoretical Physics, Ludwig–Maximilians–Universität München, Theresienstraße 37, 80333 München (Germany)

    2015-07-30

    We show that there is a class of finite groups, the so-called perfect groups, which cannot exhibit anomalies. This implies that all non-Abelian finite simple groups are anomaly-free. On the other hand, non-perfect groups generically suffer from anomalies. We present two different ways that allow one to understand these statements.

  11. Anomaly-safe discrete groups

    Directory of Open Access Journals (Sweden)

    Mu-Chun Chen

    2015-07-01

    Full Text Available We show that there is a class of finite groups, the so-called perfect groups, which cannot exhibit anomalies. This implies that all non-Abelian finite simple groups are anomaly-free. On the other hand, non-perfect groups generically suffer from anomalies. We present two different ways that allow one to understand these statements.

  12. 2010 Chemical Working Group Status

    Science.gov (United States)

    Reid, Concha M.

    2010-01-01

    The Steering Group for the Interagency Advanced Power Group (IAPG) held their business meeting on November 30-December 1st in McLean, Virginia. Status reports were presented from each of the IAPG's Working Groups. These charts contain a brief summary of the IAPG Chemical Working Group's activities during 2010 and its plans for 2011.

  13. About Hebei Jianxin Construction Group

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Hebei Jianxin Construction (Group) Ltd. was incorporated in August 1984. As the holding company, Hebei Jianxin Construction (Group)Ltd. along with five companies under its holding, such as Baoding New Generation Real Estate Development Co., Ltd. and Baoding New Generation Property Management Co., Ltd., formed Hebei Jianxin Architectural Group (hereafter, the Group).

  14. Maximal subgroups of finite groups

    Directory of Open Access Journals (Sweden)

    S. Srinivasan

    1990-01-01

    Full Text Available In finite groups maximal subgroups play a very important role. Results in the literature show that if the maximal subgroup has a very small index in the whole group then it influences the structure of the group itself. In this paper we study the case when the index of the maximal subgroups of the groups have a special type of relation with the Fitting subgroup of the group.

  15. Interrelation of group, micro-group and interpersonal identities of employees in production groups

    Directory of Open Access Journals (Sweden)

    Sidorenkov A.V.

    2016-12-01

    Full Text Available The article represents the results of mathematical and statistical analysis of the links between the levels of the identity of employees (group, micro-group and interpersonal by three components (cognitive, affective and behavioral in 37 industrial groups with expertise in different fields. The significant linear relationship between micro-group and interpersonal identity (for all components, high linear relationship between group identity and micro-group identity (only for affective component and the lack of linear relationship between the components of inter- personal and group identity are revealed. Higher influence of group identity on micro-group (for all components and interpersonal identity (for cognitive and behavioral components is found out in the totality of intercorrelation between group, micro-group and interpersonal identities. Non-linear relationship between group and micro-group identity for all components is revealed. This non-linear relation indicates that increase in expressiveness of one of the components of group iden- tity leads to decrease in expressiveness of the respective component of micro-group identity. This effect occurs until definite moment, after which, on the contrary, further reinforcement of the components of group identity leads to the increase in expressiveness of micro-group identity. These established consistent patterns are interpreted in the article.

  16. Basic and ultrabasic volcanic rocks from the Argyll Group (Dalradian) of NE Scotland

    OpenAIRE

    2005-01-01

    The Dalradian Supergroup of the Scottish Highlands is a largely metasedimentary succession of Neoproterozoic to Early Cambrian age, metamorphosed during the Caledonian Orogeny. The rocks were deposited on the Laurentian margin during and following the break-up of Rodinia. This rift setting is evidenced, in the upper half of the succession, by the presence of several volcanic sequences. A significant development of these volcanic rocks occurs in the NE Grampian Highlands. There, the Blackwater...

  17. Does group efficacy increase group identification? Resolving their paradoxical relationship

    NARCIS (Netherlands)

    van Zomeren, Martijn; Leach, Colin Wayne; Spears, Russell

    2010-01-01

    Although group identification and group efficacy are both important predictors of collective action against collective disadvantage, there is mixed evidence for their (causal) relationship. Meta-analytic and correlational evidence suggests an overall positive relationship that has been interpreted a

  18. Groups possessing extensive hierarchical decompositions

    CERN Document Server

    Januszkiewicz, T; Leary, I J

    2009-01-01

    Kropholler's class of groups is the smallest class of groups which contains all finite groups and is closed under the following operator: whenever $G$ admits a finite-dimensional contractible $G$-CW-complex in which all stabilizer groups are in the class, then $G$ is itself in the class. Kropholler's class admits a hierarchical structure, i.e., a natural filtration indexed by the ordinals. For example, stage 0 of the hierarchy is the class of all finite groups, and stage 1 contains all groups of finite virtual cohomological dimension. We show that for each countable ordinal $\\alpha$, there is a countable group that is in Kropholler's class which does not appear until the $\\alpha+1$st stage of the hierarchy. Previously this was known only for $\\alpha= 0$, 1 and 2. The groups that we construct contain torsion. We also review the construction of a torsion-free group that lies in the third stage of the hierarchy.

  19. Secure Group Communications for Large Dynamic Multicast Group

    Institute of Scientific and Technical Information of China (English)

    Liu Jing; Zhou Mingtian

    2003-01-01

    As the major problem in multicast security, the group key management has been the focus of research But few results are satisfactory. In this paper, the problems of group key management and access control for large dynamic multicast group have been researched and a solution based on SubGroup Secure Controllers (SGSCs) is presented, which solves many problems in IOLUS system and WGL scheme.

  20. Growth of Automorphism Groups of Relatively Free Groups

    Institute of Scientific and Technical Information of China (English)

    V. Drensky; A.I. Papistas

    2001-01-01

    We introduce a new growth function for automorphism groups of residually nilpotent relatively free groups Fn(V) and study its behavior. We prove that, under some natural restrictions, the growth of the group of tame automorphisms of Fn(V) is equal to the growth of the automorphism group of Fn(V), and coincides with the growth of the Lie algebra over Q associated with Fn (V). Applications of our techniques are given.

  1. Group Milieu in systemic and psychodynamic group therapy

    DEFF Research Database (Denmark)

    Lau, Marianne Engelbrecht

    group was characterized by statistically significant highest scores on Relationship (ES = 1.27) and System Maintenance / Change Dimension (ES= 1.28), while the scores for Personal Growth Dimension were comparable in the two groups. Group S had statistically significant higher scores on the following...... subscales: Cohesion (pLeader support (p=0.001), Expressiveness (p

  2. Re-Examining Group Development in Adventure Therapy Groups.

    Science.gov (United States)

    DeGraaf, Don; Ashby, Jeff

    1998-01-01

    Small-group development is an important aspect of adventure therapy. Supplementing knowledge of sequential stages of group development with knowledge concerning within-stage nonsequential development yields a richer understanding of groups. Integrating elements of the individual counseling relationship (working alliance, transference, and real…

  3. How Much "Group" Is There in Online Group Work?

    Science.gov (United States)

    Lowes, Susan

    2014-01-01

    The ability to work in groups across time and space has become a frequent requirement for the workplace and is increasingly common in higher education, but there is a surprising lack of research on how online groups work. This research applies analytic approaches used in studies of face-to-face classroom "talk" to multiple groups in two…

  4. Intensifying the Group Member's Experience Using the Group Log.

    Science.gov (United States)

    Valine, Warren J.

    1983-01-01

    Presents the use of a group log in which members analyze the content and process of each session using a suggested format. The log promotes dialogue between the leader and each group member and involves members more fully in the group process. Feedback indicates the log is valuable. (JAC)

  5. An Exploration of Group and Member Development in Experiential Groups

    Science.gov (United States)

    Ohrt, Jonathan H.; Prochenko, Yulia; Stulmaker, Hayley; Huffman, David; Fernando, Delini; Swan, Karrie

    2014-01-01

    In this phenomenological study, we explored 52 group members' development in experiential groups. Specifically, participants completed 10 weekly journal reflections about their experiences as members and also reflected on the group's overall development. Four overall themes--exploration, transition, working, closure--as well as multiple subthemes…

  6. Quantization on nilpotent Lie groups

    CERN Document Server

    Fischer, Veronique

    2016-01-01

    This book presents a consistent development of the Kohn-Nirenberg type global quantization theory in the setting of graded nilpotent Lie groups in terms of their representations. It contains a detailed exposition of related background topics on homogeneous Lie groups, nilpotent Lie groups, and the analysis of Rockland operators on graded Lie groups together with their associated Sobolev spaces. For the specific example of the Heisenberg group the theory is illustrated in detail. In addition, the book features a brief account of the corresponding quantization theory in the setting of compact Lie groups. The monograph is the winner of the 2014 Ferran Sunyer i Balaguer Prize.

  7. Group analysis of differential equations

    CERN Document Server

    Ovsiannikov, L V

    1982-01-01

    Group Analysis of Differential Equations provides a systematic exposition of the theory of Lie groups and Lie algebras and its application to creating algorithms for solving the problems of the group analysis of differential equations.This text is organized into eight chapters. Chapters I to III describe the one-parameter group with its tangential field of vectors. The nonstandard treatment of the Banach Lie groups is reviewed in Chapter IV, including a discussion of the complete theory of Lie group transformations. Chapters V and VI cover the construction of partial solution classes for the g

  8. Saving Face and Group Identity

    DEFF Research Database (Denmark)

    Eriksson, Tor; Mao, Lei; Villeval, Marie-Claire

    2015-01-01

    their self- but also other group members' image. This behavior is frequent even in the absence of group identity. When group identity is more salient, individuals help regardless of whether the least performer is an in-group or an out-group. This suggests that saving others' face is a strong social norm.......Are people willing to sacrifice resources to save one's and others' face? In a laboratory experiment, we study whether individuals forego resources to avoid the public exposure of the least performer in their group. We show that a majority of individuals are willing to pay to preserve not only...

  9. Paleoproterozoic source contributions to the Sao Roque Group sedimentation: LA-MC-ICPMS U-Pb dating and Sm-Nd systematics of clasts from metaconglomerates of the Boturuna Formation

    Energy Technology Data Exchange (ETDEWEB)

    Henrique-Pinto, Renato; Janasi, Valdecir de Assis; Tassinari, Colombo Celso Gaeta [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Geociencias. Dept. de Mineralogia e Geotectonica; Simonetti, Antonio [University of Notre Dame, South Bend (United States). Dept. of Civil Engineering and Geological Sciences; Heaman, Larry Michael, E-mail: renatohp@usp.br, E-mail: vajanasi@usp.br, E-mail: ccgtassi@usp.br, E-mail: antonio.simonetti.3@nd.edu, E-mail: larry.heaman@ualberta.ca [University of Alberta, Edmonton (Canada). Dept. of Earth and Atmospheric Sciences

    2012-12-15

    The Sao Roque Group is characterized by volcano-sedimentary sequences, in which deposition probably started in the late Paleoproterozoic. U-Pb dating by LA-MC-ICPMS of zircons extracted from predominantly equigranular monzogranites clasts from Morro Doce and Morro do Polvilho regions, yield paleoproterozoic ages of 2199 {+-}8.5 Ma and 2247 {+-}13 Ma, respectively. These represent the ages for the main source of granite for the metaconglomerates from the Boturuna Formation (basal unit of Sao Roque Group). Its polycyclic history is reinforced by the presence of inherited Archean zircons (2694 {+-}29 Ma) found within the clasts. Moreover, these clasts have also been affected by the Neoproterozoic overprinting event as indicated by their lower intercept Concordia ages. Sm-Nd isotope data for the main clast varieties from the Morro Doce metaconglomerates yield T{sub DM} ages of 2.6 to 2.7 Ga, demonstrating that these granites are the recycling products of an Archean crustal component. The metaconglomerate arkosean framework yields slightly lower {epsilon}{sub Nd(t)} values than those for the clasts, indicating that a younger and/or more primitive source also contributed to the Boturuna Formation. (author)

  10. Paleoproterozoic source contributions to the São Roque Group sedimentation: LA-MC-ICPMS U-Pb dating and Sm-Nd systematics of clasts from metaconglomerates of the Boturuna Formation

    Directory of Open Access Journals (Sweden)

    Larry Michael Heaman

    2012-12-01

    Full Text Available The So Roque Group is characterized by volcano-sedimentary sequences, in which deposition probably started in the late Paleoproterozoic. U-Pb dating by LA-MC-ICPMS of zircons extracted from predominantly equigranular monzogranites clasts from Morro Doce and Morro do Polvilho regions, yield paleoproterozoic ages of 2199 8.5 Ma and 2247 13 Ma, respectively. These represent the ages for the main source of granite for the metaconglomerates from the Boturuna Formation (basal unit of So Roque Group. Its polycyclic history is reinforced by the presence of inherited Archean zircons (2694 29 Ma found within the clasts. Moreover, these clasts have also been affected by the Neoproterozoic overprinting event as indicated by their lower intercept Concordia ages. Sm-Nd isotope data for the main clast varieties from the Morro Doce metaconglomerates yield TDM ages of 2.6 to 2.7 Ga, demonstrating that these granites are the recycling products of an Archean crustal component. The metaconglomerate arkosean framework yields slightly lower ENd(t values than those for the clasts, indicating that a younger and/or more primitive source also contributed to the Boturuna Formation.

  11. Group Lasso with Overlaps: the Latent Group Lasso approach

    CERN Document Server

    Obozinski, Guillaume; Vert, Jean-Philippe

    2011-01-01

    We study a norm for structured sparsity which leads to sparse linear predictors whose supports are unions of prede ned overlapping groups of variables. We call the obtained formulation latent group Lasso, since it is based on applying the usual group Lasso penalty on a set of latent variables. A detailed analysis of the norm and its properties is presented and we characterize conditions under which the set of groups associated with latent variables are correctly identi ed. We motivate and discuss the delicate choice of weights associated to each group, and illustrate this approach on simulated data and on the problem of breast cancer prognosis from gene expression data.

  12. Provenance analysis of the Guaritas Group (RS conglomeratic sandstones: implications for the paleoclimate and paleogeography of the Eocambrian Central Camaquã sub-basin

    Directory of Open Access Journals (Sweden)

    Antonio Romalino Santos Fragoso-Cesar

    2013-06-01

    Full Text Available The Camaquã Supergroup, located in the central-south region of Rio Grande do Sul, Brazil, constitutes a rift-type post-orogenicsedimentary basin, whose deposition occurred in a continental environment between the Ediacaran and the Eocambrian.The upper succession of the Camaquã Supergroup is represented by the Guaritas Group, a unit formed by fluvial, eolian andalluvial fan deposits that keeps important records of the sedimentation right after the end of the neoproterozoic orogenesis thatgave rise to the Gondwana supercontinent. The objective of the present work was to apply sedimentary provenance analysis inconglomeratic arenites and conglomerates of the Guaritas Group, in order to explore the climatic and tectonic evolution historyof this unit. Based on the pebble compositional data, two main source areas were recognized for the deposits of this unit,a more distal one located to the north, related with a trunk river system parallel to the basin main axis, and a more proximalone located to the east, related to transversal fluvial systems and alluvial fans at the border of the basin. The comparison of theprovenance data with previous studies on facies and paleocurrents suggests that, during the entire evolution of the east borderof the basin, there was a same transversal fluvial system, whose catchment area suffered significative reductions due to thereactivation of the east border fault during the deposition of the Varzinha and Pedra Pintada Formations. The Serra do ApertadoFormation, the upper unit of Guaritas Group, shows a high correlation between the variation of quartzose and non quartzosepebbles composition, and it was attributed to a variation between more humid and more arid climatic conditions.

  13. The thrust contact between the Canastra and Vazante groups in the Southern Brasília Belt: structural evolution, white mica crystallinity and implications for the Brasiliano orogeny

    Directory of Open Access Journals (Sweden)

    Manuela de Oliveira Carvalho

    Full Text Available ABSTRACT: Two regional thrust-sheets of Neoproterozoic metasedimentary rocks occur in the Southern Brasília Belt, northwest Minas Gerais. The lower one comprises the Vazante Group, that is formed in the studied area, from base to top, by the Serra do Garrote (metapelites interlayered with carbonaceous phyllite, Serra do Poço Verde (beige to pink stromatolitic metadolomite with interlayered greenish slates, Morro do Calcário (gray stromatolitic metadolomite interlayered with gray slates and Serra da Lapa (phyllite with dolarenitic lenses interlayered with slates formations. The upper thrust sheet consists of the Canastra Group (Paracatu formation: laminated sericite phyllites and carbonaceous phyllites interlayered with quartzite. The Braziliano orogeny resulted in four phases of contractional deformation, associated with low-grade metamorphism. The first two (D1 and D2 are ductile, while the third and fourth ones (D3 and D4 are brittle-ductile. D1 developed a slaty S1 cleavage subparallel to the primary layering, with shallow to steep dips to NW. D2 developed a crenulation cleavage (S2 that dips moderately to NW and is associated with tight to isoclinal folds. D3 and D4 phases developed crenulations and open folds and kink bands. S3 dips steeply to NW, while S4 has moderate to steep dips to NE and SW. White mica crystallinity (Kübler index measurements in metapelites indicate that both the Canastra and Vazante groups reached anchizone/epizone conditions, and metamorphic discontinuities along thrusts indicate that the peak of metamorphism is pre or syn-thrusting.

  14. Riemannian means on special euclidean group and unipotent matrices group.

    Science.gov (United States)

    Duan, Xiaomin; Sun, Huafei; Peng, Linyu

    2013-01-01

    Among the noncompact matrix Lie groups, the special Euclidean group and the unipotent matrix group play important roles in both theoretic and applied studies. The Riemannian means of a finite set of the given points on the two matrix groups are investigated, respectively. Based on the left invariant metric on the matrix Lie groups, the geodesic between any two points is gotten. And the sum of the geodesic distances is taken as the cost function, whose minimizer is the Riemannian mean. Moreover, a Riemannian gradient algorithm for computing the Riemannian mean on the special Euclidean group and an iterative formula for that on the unipotent matrix group are proposed, respectively. Finally, several numerical simulations in the 3-dimensional case are given to illustrate our results.

  15. Neutral Hydrogen in Galaxy Groups

    CERN Document Server

    McKay, N P F; Brough, S; Forbes, D A; Barnes, D G

    2002-01-01

    We present preliminary results from a study of the neutral hydrogen (HI) properties of an X-ray selected sample of nearby loose galaxy groups. This forms part of a multi-wavelength investigation (X-ray, optical and radio) of the formation and evolution of galaxies within a group environment. Some initial findings of an ATNF Parkes Multibeam wide-area neutral hydrogen imaging survey of 17 nearby galaxy groups include two new, potentially isolated clouds of HI in the NGC 1052 and NGC 5044 groups and significant amounts of HI within the group virial radii of groups NGC 3557 and IC 1459 - two groups with complex X-ray structures that suggest they may still be in the act of virialisation. Here we present ATCA high-resolution synthesis-imaging follow-up observations of the distribution and kinematics of HI in these four groups.

  16. Group performance and decision making.

    Science.gov (United States)

    Kerr, Norbert L; Tindale, R Scott

    2004-01-01

    Theory and research on small group performance and decision making is reviewed. Recent trends in group performance research have found that process gains as well as losses are possible, and both are frequently explained by situational and procedural contexts that differentially affect motivation and resource coordination. Research has continued on classic topics (e.g., brainstorming, group goal setting, stress, and group performance) and relatively new areas (e.g., collective induction). Group decision making research has focused on preference combination for continuous response distributions and group information processing. New approaches (e.g., group-level signal detection) and traditional topics (e.g., groupthink) are discussed. New directions, such as nonlinear dynamic systems, evolutionary adaptation, and technological advances, should keep small group research vigorous well into the future.

  17. On -supersolvability of finite groups

    Indian Academy of Sciences (India)

    Izabela Agata Malinowska

    2015-05-01

    A number of authors have studied the structure of a group under the assumption that some subgroups of are well located in . We will obtain some new criteria of -supersolvability and -nilpotency of groups.

  18. PRICE DISCRIMINATION THROUGH GROUP BUYING

    OpenAIRE

    2016-01-01

    This paper argues that when consumers are heterogeneous in group-buying costs, a monopolist seller may practice price discrimination through inducing certain consumers to participate in group buying. In contrast to the standard model, the optimal quantity/quality level for low valuation consumers without group buying is further distorted downward, whereas the levels for other consumers are socially optimal. Inducing group buying is more favorable when the proportion of high valuation consumer...

  19. Internal communication in corporate groups

    OpenAIRE

    Grzesik, Katarzyna

    2015-01-01

    This chapter is dedicated to internal communication in corporate groups. It discusses internal communication systems operating in the explored corporate groups and their significance for effective human resources management in those organisations. The chapter presents both the theoretical analysis based on the results of literature studies, and empirical research carried out in the explored groups. Narodowe Centrum Nauki Katarzyna Grzesik

  20. Group Cooperation in Outdoor Education

    Science.gov (United States)

    Matthews, Bruce E.

    1978-01-01

    Utilizing the Beatles' Yellow Submarine fantasy (e.g., the Blue Meanies), this outdoor education program is designed for sixth graders and special education students. Activities developed at the Cortland Resident Outdoor Education Camp include a series of group stress/challenge activities to be accomplished by everyone in the group, as a group.…

  1. On The Harmonic Oscillator Group

    CERN Document Server

    Lopez, Raquel M; Vega-Guzman, Jose M

    2011-01-01

    We discuss the maximum kinematical invariance group of the quantum harmonic oscillator from a view point of the Ermakov-type system. The invariance group of generalized driven harmonic oscillator is shown to be isomorphic to the corresponding Schroedinger group of the free particle.

  2. Group Assessment and Structured Learning.

    Science.gov (United States)

    Lambert, Warren; And Others

    1980-01-01

    Two new techniques that were used with a group of seven blind, multiply handicapped young adults in a half-way house are described. Structured learning therapy is a social skills training technique and group assessment is a method of averaging psychological data on a group of clients to facilitate program planning based on client needs.…

  3. Designing for informed group formation

    DEFF Research Database (Denmark)

    Nicolajsen, Hanne Westh; Juel Jacobsen, Alice; Riis, Marianne

    2012-01-01

    A new design ―project preparation‖ preparing for the group formation in problem based project work is proposed and investigated. The main problem is to overcome group formation based on existing relations. The hypothesis is that theme development and group formation are somewhat counterproductive...

  4. The Variety of Group Learning

    Institute of Scientific and Technical Information of China (English)

    HaoYanyan; YuZhihao

    2004-01-01

    With the rapid enrollment expansion in the recent years,the author feels it urgent to reform the traditional group work,and therefore to form a new and more effective pattern of group learning. The new of group word is based on the principles of cooperation and that of the task with the more flexible marking system.

  5. Empowering Groups that Enable Play

    Science.gov (United States)

    Wilson, David Sloan; Marshall, Danielle; Iserhott, Hindi

    2011-01-01

    Creating play environments for children usually requires groups of adults working together. An extensive scientific literature describes how groups function to achieve shared goals in general terms, and groups attempting to empower play may find this literature useful. Design principles for managing natural resources, identified by Elinor Ostrom…

  6. Stereotypes of Norwegian social groups.

    Science.gov (United States)

    Bye, Hege H; Herrebrøden, Henrik; Hjetland, Gunnhild J; Røyset, Guro Ø; Westby, Linda L

    2014-10-01

    We present a pilot study and two main studies that address the nature of stereotypes of social groups in Norway within the framework of the Stereotype Content Model (SCM). The first study focused on stereotypes of a wide range of groups across categories such as gender, age, religious conviction, socioeconomic and health status. The second study focused on stereotypes of immigrant groups. Participants (n = 244 and n = 63, respectively) rated the groups on perceived warmth, competence, status, and competition. Results from both studies support the applicability of the SCM in Norway and provides a unique insight into stereotypes of Norwegian social groups.

  7. Defining and Classifying Interest Groups

    DEFF Research Database (Denmark)

    Baroni, Laura; Carroll, Brendan; Chalmers, Adam;

    2014-01-01

    The interest group concept is defined in many different ways in the existing literature and a range of different classification schemes are employed. This complicates comparisons between different studies and their findings. One of the important tasks faced by interest group scholars engaged...... in large-N studies is therefore to define the concept of an interest group and to determine which classification scheme to use for different group types. After reviewing the existing literature, this article sets out to compare different approaches to defining and classifying interest groups with a sample...

  8. Locally minimal topological groups 1

    OpenAIRE

    Chasco, María Jesús; Dikranjan, Dikran N.; Außenhofer, Lydia; Domínguez, Xabier

    2015-01-01

    The aim of this paper is to go deeper into the study of local minimality and its connection to some naturally related properties. A Hausdorff topological group ▫$(G,tau)$▫ is called locally minimal if there exists a neighborhood ▫$U$▫ of 0 in ▫$tau$▫ such that ▫$U$▫ fails to be a neighborhood of zero in any Hausdorff group topology on ▫$G$▫ which is strictly coarser than ▫$tau$▫. Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all mini...

  9. The "group" in obstetric psychoprophylaxis.

    Science.gov (United States)

    Volpe, B; Tenaglia, F; Fede, T; Cerutti, R

    1983-01-01

    In the practice of obstetric psychoprophylaxis every method employed considered always the group both from a psychological and a pedagogic point of view. Today the group of pregnant women (or couples) is considered under various aspects: - psychological: the group as a support for members with regard to maternal and parental emotional feelings; - anthropological: the group fills up an empty vital space and becomes a "rite de passage" from a state of social identity to another one; - social: the group is a significative cultural intermediary between health services and the women-patient. The knowledge of these aspects becomes an important methodological support for group conductors. We present an analysis of our experience with groups and how this has affected the Psychoprophylaxis in the last years.

  10. Little Groups of Preon Branes

    CERN Document Server

    Mkrtchyan, H G

    2003-01-01

    Little groups for preon branes (i.e. configurations of branes with maximal (n-1)/n fraction of survived supersymmetry) for dimensions d=2,3,...,11 are calculated for all massless, and partially for massive orbits. For massless orbits little groups are semidirect product of d-2 translational group $T_{d-2}$ on a subgroup of (SO(d-2) $\\times$ R-invariance) group. E.g. at d=9 the subgroup is exceptional $G_2$ group. It is also argued, that 11d Majorana spinor invariants, which distinguish orbits, are actually invariant under d=2+10 Lorentz group. Possible applications of these results include construction of field theories in generalized space-times with brane charges coordinates, different problems of group's representations decompositions, spin-statistics issues.

  11. Little Groups of Preon Branes

    Science.gov (United States)

    MKRTCHYAN, H.; MKRTCHYAN, R.

    Little groups for preon branes (i.e. configurations of branes with maximal (n-1)/n fraction of survived supersymmetry) for dimensions d=2,3,…,11 are calculated for all massless, and partially for massive orbits. For massless orbits little groups are semidirect product of d-2 translational group Td-2 on a subgroup of (SO(d-2) × R-invariance) group. E.g. at d=9 the subgroup is exceptional G2 group. It is also argued, that 11D Majorana spinor invariants, which distinguish orbits, are actually invariant under d=2+10 Lorentz group. Possible applications of these results include construction of field theories in generalized spacetimes with brane charges coordinates, different problems of group's representations decompositions, spin-statistics issues.

  12. Ethnic group identification and group evaluation among minority and majority groups: testing the multiculturalism hypothesis.

    Science.gov (United States)

    Verkuyten, Maykel

    2005-01-01

    Following social identity theory, the author hypothesized that members of minority groups are more likely than majority group members to endorse multiculturalism more strongly and assimilationist thinking less strongly. In addition, the multiculturalism hypothesis proposes that the more minority groups endorse the ideology of multiculturalism (or assimilationism), the more (or less) likely they will be to identify with their ethnic in-group and to show positive in-group evaluation. In contrast, the more majority group members endorse multiculturalism (or assimilationism), the less (or more) likely they are to identify with their ethnic group and to show negative out-group evaluation. Results from 4 studies (correlational and experimental) provide support for this hypothesis among Dutch and Turkish participants living in the Netherlands.

  13. In-Group Versus Out-Group Source Memory.

    Science.gov (United States)

    Greenstein, Michael; Franklin, Nancy; Klug, Jessica

    2016-06-01

    A common finding in the source monitoring literature is that greater similarity impairs source discriminability. Experiments traditionally manipulate similarity overtly by describing or showing sources with explicitly differentiable features. However, people may also infer source characteristics themselves, which should also affect discriminability. Two studies examined inferred source characteristics by capitalizing on the out-group homogeneity effect, whereby in-group members are conceptualized as more diverse than out-group members. Participants learned about two sources who were described only as members of an in-group or an out-group and whose actions did not have higher a priori association with either group. Source memory was superior when participants believed the sources to be in-group members. This demonstrates that people spontaneously include inferred features with source representations and can capitalize on these features during source monitoring. Interestingly, information suggesting membership in one's in-group improved performance even for sources who had previously been considered out-group members (Experiment 2).

  14. Finite Groups with Its Power Automorphism Groups Having Small Indices

    Institute of Scientific and Technical Information of China (English)

    Jun Xin WANG; Xiu Yun GUO

    2009-01-01

    In this paper,a finite group G with|Aut(G) : P(G)| = p or pq is determined,where P(G)is the power automorphism group of G,and p,q are distinct primes.Especially,we prove that a finite group G satisfies |Aut(G) : P(G)| = pq if and only if Aut(G)/P(G) (≈)S3.Also,some other classes of finite groups are investigated and classified,which are necessary for the proof of our main results.

  15. Palaeoproterozoic continental arc magmatism, and Neoproterozoic metamorphism in the Aravalli-Delhi orogenic belt, NW India: New constraints from in situ zircon U-Pb-Hf isotope systematics, monazite dating and whole-rock geochemistry

    Science.gov (United States)

    Kaur, Parampreet; Zeh, Armin; Chaudhri, Naveen

    2017-04-01

    Presently, the extent, origin and petrogenesis of late Palaeoproterozoic (ca. 1.85 Ga) magmatism in the north-central Aravalli-Delhi orogenic belt, NW India and subsequent metamorphic overprints are poorly constrained. Results of new in situ zircon U-Pb-Hf isotope analyses in combination with whole-rock elemental and isotopic data provide the first hard evidence that granitoid magmatism occurred in a continental magmatic arc setting between 1.86 and 1.81 Ga. The Hf-Nd model ages of 3.0-2.6 Ga and inherited zircon grains of 3.3-2.5 Ga indicate abundant reworking of Archaean crust. Flat HREE patterns with negative Eu anomalies furthermore reveal that the granitoids were generated from garnet-free and plagioclase-rich sources at shallow depths. Significant isotope variation among granitoid samples (εHft = -3.7 to -9.0; εNdt = -4.8 to -7.9) indicate that the reworked Archaean crust was not completely homogenised during the Palaeoproterozoic. This is best reflected by zircon Hf-isotope variation of ca. 9.5 epsilon units within the oldest granitoid sample. Zircon grains from this sample define three discrete Hf-isotope groups at εHf1.86Ga = -8.9, -4.8 and -1.6. These are interpreted to result from mixing of zircon-saturated magmas derived from three distinct sources within the crust prior to solidification. A monazite U-Pb isochron age of 868 ± 4 Ma from one of the granitoid samples furthermore indicates that the Aravalli fold belt was affected by an important post-magmatic overprint, perhaps related to the widespread metasomatic, granulite metamorphic and/or magmatic events during the same time span.

  16. [Group cohesion: a concept analysis].

    Science.gov (United States)

    Lin, Yen-Ru; Chen, Yu-Jung; Tzeng, Wen-Chii; Chou, Kuei-Ru

    2007-10-01

    Group cohesion is considered an essential condition for achieving a successful treatment team. High cohesion groups more readily reach their goals, with group members also feeling more secure about their functions and contributions. In clinical practice, nurses use group teaching and group therapy to help patient and family members gain knowledge and skills related to illness treatment and recuperation. Effective group leadership helps minimize non-productive time and manpower and enhance interpersonal interaction. A further advantage of group cohesion is that the more effective administration of nursing programs that results can raise the profession level of staffs and reduce turnover. Walker and Avant (1995) employ concept analysis to use defining attributes in order to apply the same definition and communication to the same profession. The purpose of this paper was to apply this methodology to an analysis of group cohesion. Steps used include a review of the literature on conceptual definitions of group cohesion, a determination of defining attributes, model construction, identification of borderline, contrary, and related cases, and identification of antecedents and consequences and empirical tools. It is hoped that this analysis can help nursing staff to gain a better understanding of the concept of group cohesion and to apply such to clinical practice and nursing administration.

  17. Duality group actions on fermions

    CERN Document Server

    Pantev, T

    2016-01-01

    In this short paper we look at the action of T-duality and string duality groups on fermions, in maximally-supersymmetric theories and related theories. Briefly, we argue that typical duality groups such as SL(2,Z) have sign ambiguities in their actions on fermions, and propose that pertinent duality groups be extended by Z_2, to groups such as the metaplectic group. Specifically, we look at duality groups arising from mapping class groups of tori in M theory compactifications, T-duality, ten-dimensional type IIB S-duality, and (briefly) four-dimensional N=4 super Yang-Mills, and in each case, propose that the full duality group is a nontrivial Z_2 extension of the duality group acting on bosonic degrees of freedom, to more accurately describe possible actions on fermions. We also walk through U-duality groups for toroidal compactifications to nine, eight, and seven dimensions, which enables us to perform cross-consistency tests of these proposals.

  18. Duality group actions on fermions

    Science.gov (United States)

    Pantev, Tony; Sharpe, Eric

    2016-11-01

    In this short paper we look at the action of T-duality and string duality groups on fermions, in maximally-supersymmetric theories and related theories. Briefly, we argue that typical duality groups such as SL(2 , ℤ) have sign ambiguities in their actions on fermions, and propose that pertinent duality groups be extended by ℤ2, to groups such as the metaplectic group. Specifically, we look at duality groups arising from mapping class groups of tori in M theory compactifications, T-duality, ten-dimensional type IIB S-duality, and (briefly) four-dimensional N = 4 super Yang-Mills, and in each case, propose that the full duality group is a nontrivial ℤ2 extension of the duality group acting on bosonic degrees of freedom, to more accurately describe possible actions on fermions. We also walk through U-duality groups for toroidal compactifications to nine, eight, and seven dimensions, which enables us to perform cross-consistency tests of these proposals.

  19. Paleobiology of the Mesoproterozoic Billyakh Group, Anabar Uplift, northern Siberia

    Science.gov (United States)

    Sergeev, V. N.; Knoll, A. H.; Grotzinger, J. P.

    1995-01-01

    Silicified peritidal carbonates of the Mesoproterozoic Kotuikan and Yusmastakh Formations, Anabar Uplift, northeastern Siberia, contain exceptionally well-preserved microfossils. The assemblage is dominated by ellipsoidal akinetes of nostocalean cyanobacteria (Archaeoellipsoides) and problematic spheroidal unicells (Myxococcoides); both are allochthonous and presumably planktonic. The assemblage also includes distinctive mat-forming scytonematacean and entophysalidacean cyanobacteria, diverse short trichomes interpreted as cyanobacterial hormogonia or germinated akinetes, rare longer trichomes, and several types of colonial unicells. Although many taxa in the Kotuikan-Yusmastakh assemblage are long-ranging prokaryotes, the overall character of the assemblage is distinctly Mesoproterozoic, with its major features shared by broadly coeval floras from Canada, China, India, and elsewhere in Siberia. Microfossils also occur in middle to inner shelf shales of the Ust'-Il'ya and lower Kotuikan Formations. Leiosphaerid acritarchs (up to several hundred microns in diameter) characterize this facies. As in other Mesoproterozoic acritarch assemblages, acanthomorphic and other complex forms that typify Neoproterozoic assemblages are absent. The combination in Billyakh assemblages of exceptional preservation and low eukaryotic diversity supports the hypothesis that nucleated organisms diversified markedly near the Mesoproterozoic-Neoproterozoic boundary. The assemblages also demonstrate the antiquity of cyanobacteria capable of cell differentiation and suggest the importance of both changing peritidal substrates and evolving eukaryotes in determining stratigraphic patterns of Proterozoic prokaryotes. The permineralized assemblage contains 33 species belonging to 17 genera. Ten new species or new combinations are proposed: Archaeoellipsoides costatus n. sp., A. elongatus n. comb., A. dolichos n. comb., A. minor n. nom., A. crassus n. comb., A. major n. comb., A. bactroformis n

  20. The Local Group and other neighboring galaxy groups

    CERN Document Server

    Karachentsev, I D

    2004-01-01

    Over the last few years, rapid progress has been made in distance measurements for nearby galaxies based on the magnitude of the tip of red giant branch stars. Current CCD surveys with HST and large ground- based telescopes bring $\\sim$10%-accurate distances for roughly a hundred galaxies within 5 Mpc. The new data on distances to galaxies situated in (and around) the nearest groups: the Local Group, M81 group, CenA/M83 group, IC342/Maffei group, Sculptor filament, and Canes Venatici cloud allowed us to determine their total mass from the radius of the zero- velocity surface, $R_0$, which separates a group as bound against the homogeneous cosmic expansion. The values of $R_0$ for the virialized groups turn out to be close each other, in the range of 0.9 -- 1.3 Mpc. As a result, the total masses of the groups are close to each other, too, yielding total mass-to-blue luminosity ratios of 10 -- 40 $M_{\\sun}/L_{\\sun}$. The new total mass estimates are 3 -- 5 times lower than old virial mass estimates of these gro...

  1. Good for the group? Explaining apparent group-level selection

    NARCIS (Netherlands)

    Smallegange, I.M.; Egas, M.

    2015-01-01

    The idea that group selection can explain adaptive trait evolution is still controversial. Recent empirical work proposes evidence for group-level adaptation in a social spider, but the findings can also be explained from an individual-level perspective. The challenge remains to identify situations

  2. Group lending and the role of the group leader

    NARCIS (Netherlands)

    van Eijkel, R.; Hermes, C.L.M.; Lensink, B.W.

    2011-01-01

    This paper investigates strategic monitoring behavior within group lending. We show that monitoring efforts of group members differ in equilibrium due to the asymmetry between members in terms of future profits. In particular, we show that the entrepreneur with the highest future profits also puts i

  3. Logspace Computations in Coxeter Groups and Graph Groups

    CERN Document Server

    Diekert, Volker; Lohrey, Markus

    2012-01-01

    Computing normal forms in groups (or monoids) is in general harder than solving the word problem (equality testing). However, normal form computation has a much wider range of applications. It is therefore interesting to investigate the complexity of computing normal forms for important classes of groups. For Coxeter groups we show that the following algorithmic tasks can be solved by a deterministic Turing machine using logarithmic work space, only: 1. Compute the length of any geodesic normal form. 2. Compute the set of letters occurring in any geodesic normal form. 3. Compute the Parikh-image of any geodesic normal form in case that all defining relations have even length (i.e., in even Coxeter groups.) 4. For right-angled Coxeter groups we can do actually compute the short length normal form in logspace. (Note that short length normal forms are geodesic.) Next, we apply the results to right-angled Artin groups. They are also known as free partially commutative groups or as graph groups. As a consequence o...

  4. Group Journaling: A Tool for Reflection, Fun and Group Development

    Science.gov (United States)

    Asfeldt, Morten

    2012-01-01

    Personal journaling is common practice in outdoor programs and is an important means of reflection and meaning-making. For over 20 years the author has used group journals to promote reflection and understanding, raise important questions, explore difficult issues, develop writing and speaking skills, and enhance group development. In this…

  5. Countably determined compact abelian groups

    CERN Document Server

    Dikranjan, Dikran

    2008-01-01

    For an abelian topological group G let G^* be the dual group of all continuous characters endowed with the compact open topology. A subgroup D of G determines G if the restriction homomorphism G^* --> D^* of the dual groups is a topological isomorphism. Given a scattered compact subset X of an infinite compact abelian group G such that |X|group, we show that the set of all characters which send X into U has the same size as G^*. (Here w(G) denotes the weight of G.) As an application, we prove that a compact abelian group determined by its countable subgroup must be metrizable. This gives a negative answer to questions of Comfort, Hernandez, Macario, Raczkowski and Trigos-Arrieta, as well as provides short proofs of main results established in three manuscripts by these authors.

  6. Groups, graphs and random walks

    CERN Document Server

    Salvatori, Maura; Sava-Huss, Ecaterina

    2017-01-01

    An accessible and panoramic account of the theory of random walks on groups and graphs, stressing the strong connections of the theory with other branches of mathematics, including geometric and combinatorial group theory, potential analysis, and theoretical computer science. This volume brings together original surveys and research-expository papers from renowned and leading experts, many of whom spoke at the workshop 'Groups, Graphs and Random Walks' celebrating the sixtieth birthday of Wolfgang Woess in Cortona, Italy. Topics include: growth and amenability of groups; Schrödinger operators and symbolic dynamics; ergodic theorems; Thompson's group F; Poisson boundaries; probability theory on buildings and groups of Lie type; structure trees for edge cuts in networks; and mathematical crystallography. In what is currently a fast-growing area of mathematics, this book provides an up-to-date and valuable reference for both researchers and graduate students, from which future research activities will undoubted...

  7. Group theory and its applications

    CERN Document Server

    Thapa, Ram Kumar

    2019-01-01

    Every molecule possesses symmetry and hence has symmetry operations and symmetry elements. From symmetry properties of a system we can deduce its significant physical results. Consequently it is essential to operations of a system forms a group. Group theory is an abstract mathematical tool that underlies the study of symmetry and invariance. By using the concepts of symmetry and group theory, it is possible to obtain the members of complete set of known basis functions of the various irreducible representations of the group. I practice this is achieved by applying the projection operators to linear combinations of atomic orbital (LCAO) when the valence electrons are tightly bound to the ions, to orthogonalized plane waves (OPW) when valence electrons are nearly free and to the other given functions that are judged to the particular system under consideration. In solid state physics the group theory is indispensable in the context of finding the energy bands of electrons in solids. Group theory can be applied...

  8. Group supervision for general practitioners

    DEFF Research Database (Denmark)

    Galina Nielsen, Helena; Sofie Davidsen, Annette; Dalsted, Rikke;

    2013-01-01

    AIM: Group supervision is a sparsely researched method for professional development in general practice. The aim of this study was to explore general practitioners' (GPs') experiences of the benefits of group supervision for improving the treatment of mental disorders. METHODS: One long...... considered important prerequisites for disclosing and discussing professional problems. CONCLUSION: The results of this study indicate that participation in a supervision group can be beneficial for maintaining and developing GPs' skills in dealing with patients with mental health problems. Group supervision......-established supervision group was studied closely for six months by observing the group sessions, and by interviewing GPs and their supervisors, individually and collectively. The interviews were recorded digitally and transcribed verbatim. The data were analysed using systematic text condensation. RESULTS: The GPs found...

  9. Cascade Product of Permutation Groups

    OpenAIRE

    Egri-Nagy, Attila; Nehaniv, Chrystopher L.

    2013-01-01

    We define the cascade product of permutation groups as an external product, an explicit construction of substructures of the iterated wreath product that are much smaller than the full wreath product. This construction is essential for computational implementations of algebraic hierarchical decompositions of finite automata. We show how direct, semidirect, and wreath products and group extensions can all be expressed as cascade products, and analyse examples of groups that can be constructed ...

  10. Taxonomy Working Group Final Report

    Science.gov (United States)

    Parsons, Vickie S.; Beil, Robert J.; Terrone, Mark; Barth, Timothy S.; Panontin, Tina L.; Wales, Roxana; Rackley, Michael W.; Milne, James S.; McPherson, John W.; Dutra, Jayne E.; Shaw, Larry C.

    2009-01-01

    The purpose of the Taxonomy Working Group was to develop a proposal for a common taxonomy to be used by all NASA projects in the classifying of nonconformances, anomalies, and problems. Specifically, the group developed a recommended list of data elements along with general suggestions for the development of a problem reporting system to better serve NASA's need for managing, reporting, and trending project aberrant events. The Group's recommendations are reported in this document.

  11. Group Connectivity and Group Colorings of Graphs - A Survey

    Institute of Scientific and Technical Information of China (English)

    Hong-Jian LAI; Xiangwen LI; Yehong SHAO; Mingquan ZHAN

    2011-01-01

    In 1950s, Tutte introduced the theory of nowhere-zero flows as a tool to investigate the coloring problem of maps, together with his most fascinating conjectures on nowhere-zero flows. These have been extended by Jaeger et al. In 1992 to group connectivity, the nonhomogeneous form of nowhere-zero flows. Let G be a 2-edge-connected undirected graph, A be an (additive) abelian group and A* = A - {0}. The graph G is A-connected if G has an orientation D(G) such that for every each vertex v ∈ V(G), the total amount of f-values on the edges directed out from v minus the total amount of f-values on the edges directed into v is equal to b(v). The group coloring of a graph arises from the dual concept of group connectivity. There have been lots of investigations on these subjects.This survey provides a summary of researches on group connectivity and group colorings of graphs. It contains the following sections.1. Nowhere-zero Flows and Group Connectivity of Graphs 2. Complete Families and A-reductions 3. Reductions with Edge-deletions, Vertex-deletions and Vertex-splitting 4. Group Colorings as a Dual Concept of Group Connectivity 5. Brooks Theorem, Its Variations and Dual Forms 6. Planar Graphs 7. Group Connectivity of Graphs 7.1 Highly Connected Graphs and Collapsible Graphs 7.2 Degrees Conditions 7.3 Complementary Graphs 7.4 Products of Graphs 7.5 Graphs with Diameter at Most 2 7.6 Line Graphs and Claw-Free Graphs 7.7 Triangular Graphs 7.8 Claw-decompositions and All Tutte-orientations

  12. Group decision-making: Factors that affect group effectiveness

    Directory of Open Access Journals (Sweden)

    Juliana Osmani

    2016-03-01

    Full Text Available Organizations are operating in a dynamic and turbulent environment. In these conditions, they have to make decisions for new problems or situations. Most of decisions are therefore non-programmed and unstructured, accompanied by risk and uncertainty. Moreover, the problems and situations are complex. All organizations are oriented towards group decisionmaking processes, as useful tools to cope with uncertainty and complexity. Apart from the necessity, companies are turning towards participatory processes also to benefit from the important advantages that these processes offer. Organizations have realized the importance of group decision-making processes to contribute to the creation of sustainable competitive advantages. Main objective of this paper is to show that group decision-making processes do not offer guarantee for good decisions, because the effectiveness of group is affected by many factors. So, the first thing done in this paper is discussing about the benefits and limitations that accompany the use of groups with decision-making purpose. Afterwards, we stop on the different factors that influence the group’s ability to make good decisions. The aim is to emphasize that regardless of the many advantages of groups, some factors as group size, type of communication within the group, leadership style, the norms, the differentiation of roles and statuses, cohesion and compliance degree should be the main elements to keep into consideration because they affect the effectiveness of group. In this regard, is discussed how such factors influence the quality of decision and then we try to draw some conclusions that can improve and make better and easier group decision-making processes.

  13. Automorphism groups of some algebras

    Institute of Scientific and Technical Information of China (English)

    PARK; Hong; Goo; LEE; Jeongsig; CHOI; Seul; Hee; NAM; Ki-Bong

    2009-01-01

    The automorphism groups of algebras are found in many papers. Using auto-invariance, we find the automorphism groups of the Laurent extension of the polynomial ring and the quantum n-plane (respectively, twisting polynomial ring) in this work. As an application of the results of this work, we can find the automorphism group of a twisting algebra. We define a generalized Weyl algebra and show that the generalized Weyl algebra is simple. We also find the automorphism group of a generalized Weyl algebra. We show that the generalized Weyl algebra Am,m+n is the universal enveloping algebra of the generalized Witt algebra W(m,m + n).

  14. The Nearest Group of Galaxies

    CERN Document Server

    Van den Bergh, S

    1999-01-01

    The small Antlia-Sextans clustering of galaxies is located at a distance of only 1.36 Mpc from the Sun, and 1.72 Mpc from the adopted barycenter of the Local Group. The latter value is significantly greater than the radius of the zero- velocity surface of the Local Group which, for an assumed age of 14 Gyr, has Ro = 1.18 " 0.15 Mpc. This, together with the observation that the members of the Ant-Sex group have a mean redshift of +114 " 12 km s-1 relative to the centroid of the Local Group, suggests that the Antlia-Sextans group is not bound to our Local Group, and that it is expanding with the Hubble flow. If this conclusion is correct, then Antlia-Sextans may be the nearest external clustering of galaxies. The total galaxian population of the Ant-Sex group is ~ 1/5 that of the Local Group. However, the integrated luminosity of Ant-Sex is two orders of magnitude lower than that of the Local Group. Subject headings: Galaxies - clusters: individual (Antlia-Sextans)

  15. Abstract commensurators of braid groups

    OpenAIRE

    Leininger, Christopher J; Margalit, Dan

    2005-01-01

    Let B_n be the braid group on n strands, with n at least 4, and let Mod(S) be the extended mapping class group of the sphere with n+1 punctures. We show that the abstract commensurator of B_n is isomorphic to a semidirect product of Mod(S) with a group we refer to as the transvection subgroup, Tv(B_n). We also show that Tv(B_n) is itself isomorphic to a semidirect product of an infinite dimensional rational vector space with the multiplicative group of nonzero rational numbers.

  16. Automorphism groups of some algebras

    Institute of Scientific and Technical Information of China (English)

    PARK Hong Goo; LEE Jeongsig; CHOI Seul Hee; CHEN XueQing; NAM Ki-Bong

    2009-01-01

    The automorphism groups of algebras are found in many papers. Using auto-invariance, we find the automorphism groups of the Laurent extension of the polynomial ring and the quantum n-plane (respectively, twisting polynomial ring) in this work. As an application of the results of this work, we can find the automorphism group of a twisting algebra. We define a generalized Weyl algebra and show that the generalized Weyl algebra is simple. We also find the automorphism group of a generalized Weyl algebra. We show that the generalized Weyl algebra Am,m+n is the universal enveloping algebra of the generalized Witt algebra W(m, m+n).

  17. Strategic Groups and Banks’ Performance

    Directory of Open Access Journals (Sweden)

    Gregorz Halaj

    2009-06-01

    Full Text Available The theory of strategic groups predicts the existence of stable groups of companies that adopt similar business strategies. The theory also predicts that groups will differ in performance and in their reaction to external shocks. We use cluster analysis to identify strategic groups in the Polish banking sector. We find stable groups in the Polish banking sector constituted after the year 2000 following the major privatisation and ownership changes connected with transition to the mostly-privately-owned banking sector in the late 90s. Using panel regression methods we show that the allocation of banks to groups is statistically significant in explaining the profitability of banks. Thus, breaking down the banks into strategic groups and allowing for the different reaction of the groups to external shocks helps in a more accurate explanation of profits of the banking sector as a whole.Therefore, a more precise ex ante assessment of the loss absorption capabilities of banks is possible, which is crucial for an analysis of banking sector stability. However, we did not find evidence of the usefulness of strategic groups in explaining the quality of bank portfolios as measured by irregular loans over total loans, which is a more direct way to assess risks to financial stability.

  18. Twisted conjugacy in braid groups

    CERN Document Server

    González-Meneses, Juan

    2011-01-01

    In this note we solve the twisted conjugacy problem for braid groups, i.e. we propose an algorithm which, given two braids $u,v\\in B_n$ and an automorphism $\\phi \\in Aut (B_n)$, decides whether $v=(\\phi (x))^{-1}ux$ for some $x\\in B_n$. As a corollary, we deduce that each group of the form $B_n \\rtimes H$, a semidirect product of the braid group $B_n$ by a torsion-free hyperbolic group $H$, has solvable conjugacy problem.

  19. Visual Grouping by Neural Oscillators

    CERN Document Server

    Yu, Guoshen

    2008-01-01

    Distributed synchronization is known to occur at several scales in the brain, and has been suggested as playing a key functional role in perceptual grouping. State-of-the-art visual grouping algorithms, however, seem to give comparatively little attention to neural synchronization analogies. Based on the framework of concurrent synchronization of dynamic systems, simple networks of neural oscillators coupled with diffusive connections are proposed to solve visual grouping problems. Multi-layer algorithms and feedback mechanisms are also studied. The same algorithm is shown to achieve promising results on several classical visual grouping problems, including point clustering, contour integration and image segmentation.

  20. Membership Rules - LHCRRB Scrutiny Group

    CERN Document Server

    2017-01-01

    The LHC Resources Scrutiny Group was created in 2001 to review and scrutinize the M&O cost estimates of the LHC Collaborations. The Scrutiny Group first met on 23 August 2001 and reported to the RRBs at its 13th Plenary meeting, in October 2001 (RRB-D-2001-8). The Scrutiny Group operates according to the procedures set out in Annex 12 of the MoUs for the M&O of the LHC experiments. This document lists the Rules of Procedure that apply to the M&O Scrutiny Group

  1. Stick with your group: young children's attitudes about group loyalty.

    Science.gov (United States)

    Misch, Antonia; Over, Harriet; Carpenter, Malinda

    2014-10-01

    For adults, loyalty to the group is highly valued, yet little is known about how children evaluate loyalty. We investigated children's attitudes about loyalty in a third-party context. In the first experiment, 4- and 5-year-olds watched a video of two groups competing. Two members of the losing group then spoke. The disloyal individual said she wanted to win and therefore would join the other group. The loyal individual said she also wanted to win but would stay with her group. Children were then asked five forced-choice questions about these two individuals' niceness, trustworthiness, morality, and deservingness of a reward. The 5-year-olds preferred the loyal person across all questions; results for the 4-year-olds were considerably weaker but in the same direction. The second experiment investigated the direction of the effect in 5-year-olds. In this experiment, children answered questions about either a loyal individual, a disloyal individual, or a neutral individual. Children rated both the loyal and neutral individuals more positively than the disloyal individual across a number of measures. Thus, whereas disloyal behavior is evaluated unfavorably by children, loyal behavior is the expected norm. These results suggest that, at least from 5 years of age, children understand that belonging to a group entails certain commitments. This marks an important step in their own ability to negotiate belonging and become trustworthy and reliable members of their social groups.

  2. Energy Innovation. IVO group`s research and development report

    Energy Technology Data Exchange (ETDEWEB)

    Salminen, P.; Laiho, Y.; Kaikkonen, H.; Leisio, C.; Hinkkanen, S.; Fletcher, R. [eds.

    1997-11-01

    This annual booklet of the IVO Group`s research and development activities presents a number of articles, written by experts from IVO. The products described are examples of the environmentally-oriented selection made available by the IVO Group. In fact, the entire energy technology developed in Finland is environmentally oriented, if seen from the international perspective. The new business potential of environmental technology is great, and it is believed that in the year 2000, exportation of Finnish know-how in the field of energy-saving and efficiency will exceed the value of out energy imports

  3. 2002 annual report EDF group; 2002 rapport annuel groupe EDF

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-07-01

    This document is the 2002 annual report of Electricite de France (EdF) group, the French electric utility. Content: Introductory section (EDF at a glance, Chairman's message, 2002 Highlights); Corporate governance and Group strategy (Corporate governance, sustainable growth strategy, EDF branches); Financial performance (Reaching critical mass, Margins holding up well, Balance sheet); Human resources (Launching Group-wide synergies, Optimising human resources); Customers (Major customers, SMEs and professional customers, Local authorities, Residential customers, Ensuring quality access to electricity); Generation (A balanced energy mix, Nuclear generation, Fossil-fuelled generation, Renewable energies); Corporate social responsibility (Global and local partnerships, Promoting community development)

  4. Energy Innovation. IVO Group`s Research and Development Report

    Energy Technology Data Exchange (ETDEWEB)

    Salminen, P.; Laiho, Y.; Kaikkonen, H.; Leisio, C.; Hinkkanen, S. [eds.

    1996-11-01

    This annual booklet of the IVO Group`s research and development activities presents a number of articles, written by experts from IVO. The products described are examples of the environmentally-oriented selection made available by the IVO Group. In fact, the entire energy technology developed in Finland is environmentally oriented, if seen from the international perspective. The new business potential of environmental technology is great, and it is believed that in the year 2000, exportation of Finnish know-how in the field of energy-saving and efficiency will exceed the value of out energy imports

  5. Working group report: Quantum chromodynamics

    Indian Academy of Sciences (India)

    V Ravindra; Pankaj Agrawal; Rahul Basu; Satyaki Bhattacharya; J Blümlein; V Del Duca; R Harlander; D Kosower; Prakash Mathews; Anurag Tripathi

    2006-11-01

    This is the report of the subgroup QCD of Working Group-4 at WHEPP-9. We present the activities that had taken place in the subgroup and report some of the partial results arrived at following the discussion at the working group meetings.

  6. Group theoretical methods in Physics

    Energy Technology Data Exchange (ETDEWEB)

    Olmo, M.A. del; Santander, M.; Mateos Guilarte, J.M. (eds.) (Universidad de Valladolid. Facultad de Ciencias. Valladolid (Spain))

    1993-01-01

    The meeting had 102 papers. These was distributed in following areas: -Quantum groups,-Integrable systems,-Physical Applications of Group Theory,-Mathematical Results,-Geometry, Topology and Quantum Field Theory,-Super physics,-Super mathematics,-Atomic, Molecular and Condensed Matter Physics. Nuclear and Particle Physics,-Symmetry and Foundations of classical and Quantum mechanics.

  7. Measuring group climate in prison

    NARCIS (Netherlands)

    van der Helm, P.; Stams, G.J.; van der Laan, P.

    2011-01-01

    The present study examines the construct validity and reliability of the Prison Group Climate Instrument (PGCI) in a sample of 77 adolescents placed in a Dutch youth prison and 49 adult prisoners living in a Dutch psychiatric prison with a therapeutic living group structure. Confirmatory factor anal

  8. Group Work in Science Classrooms

    Science.gov (United States)

    McGregor, Debbie; Tolmie, Andrew

    2009-01-01

    This article considers how students might work together in small groups, from two to eight, in either a primary or secondary science classroom. The nature of group work can vary widely and could include, for example, a pair carrying out an illustrative experiment, a trio or quad debating climate change, or six or seven rehearsing how they will…

  9. Exploring Interpersonal Compatibility in Groups.

    Science.gov (United States)

    Keyton, Joann

    This study investigated William Schutz's three-dimensional theory of interpersonal behavior and compatibility (FIRO) to determine its validity as a group measure of compatibility. Data were collected from 248 students enrolled in a multi-section course in small group communications at a large midwestern university. Subjects self-selected…

  10. Group Intervention in Pediatric Rehabilitation

    Science.gov (United States)

    LaForme Fiss, Alyssa

    2012-01-01

    Group intervention in pediatric physical and occupational therapy is an alternative to individual intervention allowing the therapist to meet the needs of multiple children at one time. Survey research indicates that approximately 40% to 60% of pediatric physical and occupational therapists use group intervention at least occasionally in practice,…

  11. The Globalization of Cooperative Groups.

    Science.gov (United States)

    Valdivieso, Manuel; Corn, Benjamin W; Dancey, Janet E; Wickerham, D Lawrence; Horvath, L Elise; Perez, Edith A; Urton, Alison; Cronin, Walter M; Field, Erica; Lackey, Evonne; Blanke, Charles D

    2015-10-01

    The National Cancer Institute (NCI)-supported adult cooperative oncology research groups (now officially Network groups) have a longstanding history of participating in international collaborations throughout the world. Most frequently, the US-based cooperative groups work reciprocally with the Canadian national adult cancer clinical trial group, NCIC CTG (previously the National Cancer Institute of Canada Clinical Trials Group). Thus, Canada is the largest contributor to cooperative groups based in the United States, and vice versa. Although international collaborations have many benefits, they are most frequently utilized to enhance patient accrual to large phase III trials originating in the United States or Canada. Within the cooperative group setting, adequate attention has not been given to the study of cancers that are unique to countries outside the United States and Canada, such as those frequently associated with infections in Latin America, Asia, and Africa. Global collaborations are limited by a number of barriers, some of which are unique to the countries involved, while others are related to financial support and to US policies that restrict drug distribution outside the United States. This article serves to detail the cooperative group experience in international research and describe how international collaboration in cancer clinical trials is a promising and important area that requires greater consideration in the future.

  12. Modeling Interactions in Small Groups

    Science.gov (United States)

    Heise, David R.

    2013-01-01

    A new theory of interaction within small groups posits that group members initiate actions when tension mounts between the affective meanings of their situational identities and impressions produced by recent events. Actors choose partners and behaviors so as to reduce the tensions. A computer model based on this theory, incorporating reciprocal…

  13. Topological dynamics and definable groups

    CERN Document Server

    Pillay, Anand

    2012-01-01

    Following the works of Newelski we continue the study of the relations between abstract topological dynamics and generalized stable group theory. We show that the Ellis theory, applied to the action of G(M) on its type space, for G an fsg group in a NIP theory, and M any model, yields the quotient G/G^00.

  14. Second Anthropocene Working Group meeting

    OpenAIRE

    2016-01-01

    The second meeting of the Anthropocene Working Group (AWG) was held at the McDonald Institute for Archaeological Research, University of Cambridge, on 24th and 25th November 2015. It took the form of a workshop with 12 members of the working group and numerous archaeologists from the Institute in lively conversation with each other. Dis...

  15. Social Disaffection Among Deprived Groups

    Science.gov (United States)

    Katz, Daniel; And Others

    1977-01-01

    Examines groups of individuals of differing income, education, occupation, age and sex and investigates the extent of differences between these groups on three levels: nationalism, support for the political system and satisfaction with aspects of every day living. Available from: International Journal of Intercultural Relations, Transaction…

  16. Loop groups and noncommutative geometry

    CERN Document Server

    Carpi, Sebastiano

    2015-01-01

    We describe the representation theory of loop groups in terms of K-theory and noncommutative geometry. This is done by constructing suitable spectral triples associated with the level l projective unitary positive-energy representations of any given loop group LG. The construction is based on certain supersymmetric conformal field theory models associated with LG.

  17. Working Group VII: Food Products

    OpenAIRE

    Midtvedt, Tore

    2011-01-01

    The working group recognised that many international and national organisations had developed strategies for evaluating the safety of new food products produced by the application of genetic modification. These strategies were necessarily fairly general and the group agreed that it should focus its attention on the pathogenicity and toxicity of live microorganisms used in food.

  18. Challenges Facing Group Work Online

    Science.gov (United States)

    Chang, Bo; Kang, Haijun

    2016-01-01

    Online group work can be complicated because of its asynchronous characteristics and lack of physical presence, and its requirements for skills in handling technology, human relationships, and content-related tasks. This study focuses on the administrative, logistical and relationship-related challenges in online group work. Challenges in areas…

  19. Group Work with Transgender Clients

    Science.gov (United States)

    Dickey, Lore M.; Loewy, Michael I.

    2010-01-01

    Drawing on the existing literature, the authors' research and clinical experiences, and the first author's personal journey as a member and leader of the transgender community, this article offers a brief history of group work with transgender clients followed by suggestions for group work with transgender clients from a social justice…

  20. Play and Positive Group Dynamics

    Science.gov (United States)

    Thompson, Pam; White, Samantha

    2010-01-01

    Play is an important part of a child's life and essential to learning and development (Vygotsky, 1978). It is vital that students participate in play and that play be conducted in a restorative manner. Play allows a variety of group dynamics to emerge. Irvin Yalom (1995) identifies 11 curative factors of the group experience. These factors include…

  1. Energy velocity and group velocity

    Institute of Scientific and Technical Information of China (English)

    陈宇

    1995-01-01

    A new Lagrangian method for studying the relationship between the energy velocity and the group velocity is described. It is proved that under the usual quasistatic electric field, the energy velocity is identical to the group velocity for acoustic waves in anisotropic piezoelectric (or non-piezoelectric) media.

  2. SOME IDEAS ON GROUP WORK

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    Group work is a widely adopted activity in the oral English class, and certainly boasts a number of advantages. However, problems may occur in the organization of group discussions and the reports afterwards. This paper puts forward some suggestions for solving these problems.

  3. Lenzing Group: Expanding in Asia

    Institute of Scientific and Technical Information of China (English)

    Wang Ting

    2007-01-01

    @@ On April 10th,the Lenzing Group started operation of its new viscose fiber plant at Nanjing(China).The new viscose fiber plant is the second production site for this fiber of theLenzing Group in Asia and its sixth production site globally.

  4. Group Development: Extending Tuckman's Theory.

    Science.gov (United States)

    Maples, Mary F.

    1988-01-01

    Presents a framework for extending the Tuckman model of developmental sequence in small groups. Considers Tuckman's stages of forming, storming, norming, performing, and adjourning lacking in descriptive depth and clear definition. Gathered and organized group dynamics graduate students' assessments of characteristics of stages over five-year…

  5. 江南中段慈化地区新元古代高镁安山岩的厘定及其构造意义%Geochronology and Geochemistry of Cihua Neoproterozoic High-Mg Andesites in Jiangnan Orogen and Their Tectonic Implications

    Institute of Scientific and Technical Information of China (English)

    张玉芝; 王岳军; 郭小飞; 甘成势; 邢晓婉; 宋菁菁

    2015-01-01

    江南造山带被普遍认为是扬子与华夏陆块在新元古代的拼合带,其拼合机制及精细时代却一直备受争议.在江南造山带中段湘赣交界慈化地区识别出新元古代火山岩,并对其进行了锆石 U-Pb 年代学及主微量地球化学研究.该火山岩发育于冷家溪群地层中,其锆石 LA-ICP-MS 年代学测试得到了832±12 Ma 的206 Pb/238 U 加权平均年龄(n=16,MSWD=0.12),代表其喷发年龄.主量元素结果显示,SiO2和 MgO 含量分别为57.67%~61.33%和3.51%~4.29%,Mg#为52~57,高于正常弧火山岩,属高镁安山岩.微量元素富集轻稀土元素和大离子亲石元素,亏损高场强元素,其 Nb-Ta、Ti 亏损,具“弧型”地球化学特征,可能来源于受板片熔体/流体或者俯冲再循环沉积物交代的难熔地幔源区.上述资料表明,慈化高镁安山岩是江南造山带中段楔形地幔源区受消减组分交代作用的产物,暗示此时江南造山带中段仍在消减,扬子和华夏陆块尚未完全拼合.结合前人研究成果,江南造山带不同区段的闭合时间可能存在差异.%It is generally accepted that the Jiangnan orogenic belt led to the amalgamation of the Yangtze with Cathaysia blocks during the Neoproterozoic period.However,its tectonic evolution and amalgamation timing are still in debate.This paper pres-ents a set of new geochronological and geochemical data for the newly-identified Neoproterozoic high-Mg volcanics from Cihua (Jiangxi).LA-ICP-MS zircon U-Pb dating of the representative sample yields a weighted mean age of 832±12 Ma (n=16, MSWD=0.12),representing the eruption age of the andesite.Geochemical results indicate that they can be classified as high-Mg andesites with SiO2 ranging from 57.67% to 61.33%,MgO from 3.51% to 4.29% and Mg-number from 52 to 57.Their chondrite-normalized REE patterns exhibit a left-sloping pattern with enriched LREEs

  6. Groups and Geometries : Siena Conference

    CERN Document Server

    Kantor, William; Lunardon, Guglielmo; Pasini, Antonio; Tamburini, Maria

    1998-01-01

    On September 1-7, 1996 a conference on Groups and Geometries took place in lovely Siena, Italy. It brought together experts and interested mathematicians from numerous countries. The scientific program centered around invited exposi­ tory lectures; there also were shorter research announcements, including talks by younger researchers. The conference concerned a broad range of topics in group theory and geometry, with emphasis on recent results and open problems. Special attention was drawn to the interplay between group-theoretic methods and geometric and combinatorial ones. Expanded versions of many of the talks appear in these Proceedings. This volume is intended to provide a stimulating collection of themes for a broad range of algebraists and geometers. Among those themes, represented within the conference or these Proceedings, are aspects of the following: 1. the classification of finite simple groups, 2. the structure and properties of groups of Lie type over finite and algebraically closed fields of f...

  7. Decision Dynamics in Group Evacuation

    CERN Document Server

    Han, Fangqiu; Schlesinger, Kimberly J; Gür, Izzeddin; Carlson, Jean M

    2016-01-01

    Identifying factors that affect human decision making and quantifying their influence remain essential and challenging tasks for the design and implementation of social and technological communication systems. We report results of a behavioral experiment involving decision making in the face of an impending natural disaster. In a controlled laboratory setting, we characterize individual and group evacuation decision making influenced by several key factors, including the likelihood of the disaster, available shelter capacity, group size, and group decision protocol. Our results show that success in individual decision making is not a strong predictor of group performance. We use an artificial neural network trained on the collective behavior of subjects to predict individual and group outcomes. Overall model accuracy increases with the inclusion of a subject-specific performance parameter based on laboratory trials that captures individual differences. In parallel, we demonstrate that the social media activit...

  8. Stackable groups, tame filling invariants, and algorithmic properties of groups

    CERN Document Server

    Brittenham, Mark

    2011-01-01

    We introduce a combinatorial property for finitely generated groups called stackable that implies the existence of an inductive procedure for constructing van Kampen diagrams with respect to a canonical finite presentation. We also define algorithmically stackable groups, for which this procedure is an effective algorithm. This property gives a uniform model for algorithms arising from both rewriting systems and almost convexity for groups. We also introduce a new pair of asymptotic invariants that are filling inequalities refining the notions of intrinsic and extrinsic diameter inequalities for finitely presented groups. These tame filling invariants are quasi-isometry invariants, up to Lipschitz equivalence of functions (and, in the case of the intrinsic tame filling invariant, up to choice of a sufficiently large set of defining relators). We show that radial tameness functions are equivalent to the extrinsic tame filling invariant condition, and so intrinsic tame filling invariants can be viewed as the in...

  9. EDF group - annual report 2003; Groupe EDF - rapport annuel 2003

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    This document contains the magazine, the financial statements and the sustainable development report of Electricite de France (EdF) group for 2003: 1 - the magazine (chairman's statement, group profile, vision and strategy); 2 - the consolidated financial statements for the period ended 31 December 2003 (statutory auditors' report on the consolidated financial statements, EDF's summary annual financial statements); 3 - sustainable development report (transparency and dialogue, responsibility, commitment, partnerships for progress). (J.S.)

  10. Dealer Group or Financial Planning Group? A Brief Technical Note

    Directory of Open Access Journals (Sweden)

    Lujer Santacruz

    2011-06-01

    Full Text Available This technical note examines whether the industry practice of using the term dealer group when referring to afinancial planning group contributes to the general perception that financial advisers are not objective whenmaking financial product recommendations. An experimental design carried out through an online survey isused. This is supplemented by a direct comparison survey on the two terminologies. The results provide acase for the industry to adopt a new terminology.

  11. Bayesian hierarchical grouping: Perceptual grouping as mixture estimation.

    Science.gov (United States)

    Froyen, Vicky; Feldman, Jacob; Singh, Manish

    2015-10-01

    We propose a novel framework for perceptual grouping based on the idea of mixture models, called Bayesian hierarchical grouping (BHG). In BHG, we assume that the configuration of image elements is generated by a mixture of distinct objects, each of which generates image elements according to some generative assumptions. Grouping, in this framework, means estimating the number and the parameters of the mixture components that generated the image, including estimating which image elements are "owned" by which objects. We present a tractable implementation of the framework, based on the hierarchical clustering approach of Heller and Ghahramani (2005). We illustrate it with examples drawn from a number of classical perceptual grouping problems, including dot clustering, contour integration, and part decomposition. Our approach yields an intuitive hierarchical representation of image elements, giving an explicit decomposition of the image into mixture components, along with estimates of the probability of various candidate decompositions. We show that BHG accounts well for a diverse range of empirical data drawn from the literature. Because BHG provides a principled quantification of the plausibility of grouping interpretations over a wide range of grouping problems, we argue that it provides an appealing unifying account of the elusive Gestalt notion of Prägnanz.

  12. Third group cohomology and gerbes over Lie groups

    Science.gov (United States)

    Mickelsson, Jouko; Wagner, Stefan

    2016-10-01

    The topological classification of gerbes, as principal bundles with the structure group the projective unitary group of a complex Hilbert space, over a topological space H is given by the third cohomology H3(H , Z) . When H is a topological group the integral cohomology is often related to a locally continuous (or in the case of a Lie group, locally smooth) third group cohomology of H. We shall study in more detail this relation in the case of a group extension 1 → N → G → H → 1 when the gerbe is defined by an abelian extension 1 → A → N ˆ → N → 1 of N. In particular, when Hs1 (N , A) vanishes we shall construct a transgression map Hs2 (N , A) → Hs3 (H ,AN) , where AN is the subgroup of N-invariants in A and the subscript s denotes the locally smooth cohomology. Examples of this relation appear in gauge theory which are discussed in the paper.

  13. Spin networks for noncompact groups

    Science.gov (United States)

    Freidel, Laurent; Livine, Etera R.

    2003-03-01

    Spin networks are a natural generalization of Wilson loop functionals. They have been extensively studied in the case where the gauge group is compact and it has been shown that they naturally form a basis of gauge invariant observables. Physically the restriction to compact gauge groups is enough for the study of Yang-Mills theories, however it is well known that noncompact groups naturally arise as internal gauge groups for Lorentzian gravity models. In this context, a proper construction of gauge invariant observables is needed. The purpose of the present work is to define the notion of spin network states for noncompact groups. We first build, by a careful gauge fixing procedure, a natural measure and a Hilbert space structure on the space of gauge invariant graph connections. Spin networks are then defined as generalized eigenvectors of a complete set of hermitic commuting operators. We show how the delicate issue of taking the quotient of a space by noncompact groups can be address in term of algebraic geometry. We finally construct the full Hilbert space containing all spin network states. Having in mind applications to gravity, we illustrate our results for the groups SL(2,R) and SL(2,C).

  14. Modelling group dynamic animal movement

    DEFF Research Database (Denmark)

    Langrock, Roland; Hopcraft, J. Grant C.; Blackwell, Paul G.;

    2014-01-01

    Group dynamic movement is a fundamental aspect of many species' movements. The need to adequately model individuals' interactions with other group members has been recognised, particularly in order to differentiate the role of social forces in individual movement from environmental factors. However...... makes its movement decisions relative to the group centroid. The basic idea is framed within the flexible class of hidden Markov models, extending previous work on modelling animal movement by means of multi-state random walks. While in simulation experiments parameter estimators exhibit some bias...

  15. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  16. Semi-Quantitative Group Testing

    CERN Document Server

    Emad, Amin

    2012-01-01

    We consider a novel group testing procedure, termed semi-quantitative group testing, motivated by a class of problems arising in genome sequence processing. Semi-quantitative group testing (SQGT) is a non-binary pooling scheme that may be viewed as a combination of an adder model followed by a quantizer. For the new testing scheme we define the capacity and evaluate the capacity for some special choices of parameters using information theoretic methods. We also define a new class of disjunct codes suitable for SQGT, termed SQ-disjunct codes. We also provide both explicit and probabilistic code construction methods for SQGT with simple decoding algorithms.

  17. Congruence Subgroups of Hecke Groups

    Institute of Scientific and Technical Information of China (English)

    Bo CHEN; Ping Zhi YUAN

    2009-01-01

    Hecke groups are an important tool in investigating functional equations, and congruence subgroups of Hecke groups play an important rule in research of the solutions of the Dirichlet series.When q, m are two primes, congruence subgroups and the principal congruence subgroups of level m of the Hecke group H(√q) have been investigated in many papers. In this paper, we generalize these results to the case where q is a positive integer with q ≥ 5, √q ¢ Z and m is a power of an odd prime.

  18. MODELLING OF ONLINE GROUP DISCOUNTS

    Directory of Open Access Journals (Sweden)

    Karlo Kotarac

    2013-02-01

    Full Text Available Web pages for group discounts have become very popular in the past few years. In this paper we concentrate on the group discounts for the service industry in which a quality of the service plays an important role in retaining customers which in return affects business profitability. We present a model of the group discount offer from a merchant’s point view. A merchant decides about the size of the discount offered, having in mind quality of the service offered which is affected by the number of customers who use the service. Finally, we derive the first order optimality conditions.

  19. Geometry, rigidity, and group actions

    CERN Document Server

    Farb, Benson; Zimmer, Robert J

    2011-01-01

    The study of group actions is more than a hundred years old but remains to this day a vibrant and widely studied topic in a variety of mathematic fields. A central development in the last fifty years is the phenomenon of rigidity, whereby one can classify actions of certain groups, such as lattices in semi-simple Lie groups. This provides a way to classify all possible symmetries of important spaces and all spaces admitting given symmetries. Paradigmatic results can be found in the seminal work of George Mostow, Gergory Margulis, and Robert J. Zimmer, among others.The p

  20. Group theory and its applications

    CERN Document Server

    Loebl, Ernest M

    1975-01-01

    Group Theory and its Applications, Volume III covers the two broad areas of applications of group theory, namely, all atomic and molecular phenomena, as well as all aspects of nuclear structure and elementary particle theory.This volume contains five chapters and begins with an introduction to Wedderburn's theory to establish the structure of semisimple algebras, algebras of quantum mechanical interest, and group algebras. The succeeding chapter deals with Dynkin's theory for the embedding of semisimple complex Lie algebras in semisimple complex Lie algebras. These topics are followed by a rev

  1. Marketing audit in group practice.

    Science.gov (United States)

    Blackburn, J M

    1984-01-01

    The marketing audit, whether large-scale or small-scale, will soon be critical to the success of every medical group practice. This dynamic process, in which the many components of a group's marketing efforts are analyzed, is examined from the perspective of ideal circumstances and unlimited resources, and more pragmatically, from the perspective of various-sized groups, with different resources and marketing talent. The audit components are prioritized, possible adaptations and combinations are presented, and reasonable implementation mechanisms, designed to address audit outcomes, are suggested.

  2. Groups, measures, and the NIP

    Science.gov (United States)

    Hrushovski, Ehud; Peterzil, Ya'acov; Pillay, Anand

    2008-04-01

    We discuss measures, invariant measures on definable groups, and genericity, often in an NIP (failure of the independence property) environment. We complete the proof of the third author's conjectures relating definably compact groups G in saturated o -minimal structures to compact Lie groups. We also prove some other structural results about such G , for example the existence of a left invariant finitely additive probability measure on definable subsets of G . We finally introduce the new notion of ``compact domination" (domination of a definable set by a compact space) and raise some new conjectures in the o -minimal case.

  3. Dual identity, in-group projection, and out-group feelings among ethnic minority groups

    NARCIS (Netherlands)

    Verkuyten, Maykel; Martinovic, Borja

    2016-01-01

    This study extends research on dual identity and in-group projection by considering category prototypicality and indispensability, and by focusing on ethnic minority members and their attitudes towards the native majority and minority out-groups. Among a sample of 491 participants of the three large

  4. Symbolic dynamics and hyperbolic groups

    CERN Document Server

    Coornaert, Michel

    1993-01-01

    Gromov's theory of hyperbolic groups have had a big impact in combinatorial group theory and has deep connections with many branches of mathematics suchdifferential geometry, representation theory, ergodic theory and dynamical systems. This book is an elaboration on some ideas of Gromov on hyperbolic spaces and hyperbolic groups in relation with symbolic dynamics. Particular attention is paid to the dynamical system defined by the action of a hyperbolic group on its boundary. The boundary is most oftenchaotic both as a topological space and as a dynamical system, and a description of this boundary and the action is given in terms of subshifts of finite type. The book is self-contained and includes two introductory chapters, one on Gromov's hyperbolic geometry and the other one on symbolic dynamics. It is intended for students and researchers in geometry and in dynamical systems, and can be used asthe basis for a graduate course on these subjects.

  5. NISE (Nursing Inservice Education Group)

    Science.gov (United States)

    Clubine, Marilyn; And Others

    1973-01-01

    The purpose of the Toronto Inservice Education Group became to meet regularly in order to provide an opportunity to assist and guide those responsible for formulating and carrying out inservice education. Article outlines their objectives. (Author/RK)

  6. Topological Groups and Dugundji Compacta

    Science.gov (United States)

    Uspenskiĭ, V. V.

    1990-02-01

    A compact space X is called a Dugundji compactum if for every compact Y containing X, there exists a linear extension operator \\Lambda:\\ C(X)\\to C(Y) which preserves nonnegativity and maps constants into constants. It is known that every compact group is a Dugundji compactum. In this paper we show that compacta connected in a natural way with topological groups enjoy the same property. For example, in each of the following cases, the compact space X is a Dugundji compactum:1) X is a retract of an arbitrary topological group;2) X=\\beta P, where P is a pseudocompact space on which some \\aleph_0-bounded topological group acts transitively and continuously.Bibliography: 57 titles.

  7. Climate change and group dynamics

    NARCIS (Netherlands)

    Postmes, Tom

    2015-01-01

    The characteristics and views of people sceptical about climate change have been analysed extensively. A study now confirms that sceptics in the US have some characteristics of a social movement, but shows that the same group dynamics propel believers

  8. The Group Treatment of Bulimia.

    Science.gov (United States)

    Weinstein, Harvey M.; Richman, Ann

    1984-01-01

    Bulimia has become an increasing problem in the college population. This article describes a group psychotherapeutic treatment approach to the problem. A theoretical formulation of the psychodynamics that may underlie the development of bulimia is offered. (Author/DF)

  9. A service dog in group.

    Science.gov (United States)

    Rothberg, Brian; Collins, Emily

    2015-04-01

    Service dogs are sanctioned by the Americans with Disabilities Act as having protected rights allowing them to assist owners with disabilities. These dogs are appearing with increasing frequency in healthcare settings, and it is important for healthcare providers to understand the rules and regulations given to service animals and owners. We discuss processes that transpired when a service dog was brought into a psychodynamic psychotherapy group. The purpose of this paper is to highlight the unintended consequences of the Americans with Disabilities Act of 2010 as it concerns service dogs and the impact on the group process. Problems resulting from the introduction of service dogs into therapy groups should be anticipated and explicitly discussed in the course of the group's transactions.

  10. Kloosterman sheaves for reductive groups

    CERN Document Server

    Heinloth, Jochen; Yun, Zhiwei

    2010-01-01

    Deligne constructed a remarkable local system on $\\bP^1-\\{0,\\infty\\}$ attached to a family of Kloosterman sums. Katz calculated its monodromy and asked whether there are Kloosterman sheaves for general reductive groups and which automorphic forms should be attached to these local systems under the Langlands correspondence. Motivated by work of Gross and Frenkel-Gross we find an explicit family of such automorphic forms and even a simple family of automorphic sheaves in the framework of the geometric Langlands program. We use these automorphic sheaves to construct l-adic Kloosterman sheaves for any reductive group in a uniform way, and describe the local and global monodromy of these Kloosterman sheaves. In particular, they give motivic Galois representations with exceptional monodromy groups G_2,F_4,E_7 and E_8. This also gives an example of the geometric Langlands correspondence with wild ramifications for any reductive group.

  11. Remainder Wheels and Group Theory

    Science.gov (United States)

    Brenton, Lawrence

    2008-01-01

    Why should prospective elementary and high school teachers study group theory in college? This paper examines applications of abstract algebra to the familiar algorithm for converting fractions to repeating decimals, revealing ideas of surprising substance beneath an innocent facade.

  12. Metabolomics and Epidemiology Working Group

    Science.gov (United States)

    The Metabolomics and Epidemiology (MetEpi) Working Group promotes metabolomics analyses in population-based studies, as well as advancement in the field of metabolomics for broader biomedical and public health research.

  13. On w-maximal groups

    CERN Document Server

    Gonzalez-Sanchez, Jon

    2010-01-01

    Let $w = w(x_1,..., x_n)$ be a word, i.e. an element of the free group $F =$ on $n$ generators $x_1,..., x_n$. The verbal subgroup $w(G)$ of a group $G$ is the subgroup generated by the set $\\{w (g_1,...,g_n)^{\\pm 1} | g_i \\in G, 1\\leq i\\leq n \\}$ of all $w$-values in $G$. We say that a (finite) group $G$ is $w$-maximal if $|G:w(G)|> |H:w(H)|$ for all proper subgroups $H$ of $G$ and that $G$ is hereditarily $w$-maximal if every subgroup of $G$ is $w$-maximal. In this text we study $w$-maximal and hereditarily $w$-maximal (finite) groups.

  14. Group valued differential forms revisited

    DEFF Research Database (Denmark)

    Kock, Anders

    We study the relationship between combinatorial group valued differential forms, and classical differential forms with values in the corresponding Lie algebra. In particular, we compare simplicial coboundary and exterior derivative for 1-forms. The results represent strengthenings of results...

  15. Injuries in group kept horses

    DEFF Research Database (Denmark)

    Mejdell, C.M.; Jorgensen, G.M.; Keeling, L.

    2014-01-01

    Group housing of horses is not very widespread, despite obvious advantages for their development and mental well-being. One often expressed rationale for this is that horse owners are worried about the risk of injuries due to kicks, bites or being chased into obstacles. To address this concern, we...... developed and validated a scoring system for external injuries in horses to be able to record the severity of a lesion in a standardized and simple way under field conditions. The scoring system has five categories from insignificant loss of hair to severe, life threatening injuries. It was used...... to categorize 1124 injuries in 478 horses. Most of these horses were allocated to groups to study the effect of group composition (i.e. same age or mixed, same gender or mixed, socially stable or unstable groups) on behaviour and injuries. The material included mainly riding and leisure purpose horses...

  16. Bosonic colored group field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ben Geloun, Joseph [Universite Paris XI, Laboratoire de Physique Theorique, Orsay Cedex (France); University of Abomey-Calavi, Cotonou (BJ). International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair); Universite Cheikh Anta Diop, Departement de Mathematiques et Informatique, Faculte des Sciences et Techniques, Dakar (Senegal); Magnen, Jacques [Ecole Polytechnique, Centre de Physique Theorique, Palaiseau Cedex (France); Rivasseau, Vincent [Universite Paris XI, Laboratoire de Physique Theorique, Orsay Cedex (France)

    2010-12-15

    Bosonic colored group field theory is considered. Focusing first on dimension four, namely the colored Ooguri group field model, the main properties of Feynman graphs are studied. This leads to a theorem on optimal perturbative bounds of Feynman amplitudes in the ''ultraspin'' (large spin) limit. The results are generalized in any dimension. Finally, integrating out two colors we write a new representation, which could be useful for the constructive analysis of this type of models. (orig.)

  17. Holonomy groups of Lorentzian manifolds

    CERN Document Server

    Galaev, Anton S

    2016-01-01

    In this paper, a survey of the recent results about the classification of the connected holonomy groups of the Lorentzian manifolds is given. A simplification of the construction of the Lorentzian metrics with all possible connected holonomy groups is obtained. As the applications, the Einstein equation, Lorentzian manifolds with parallel and recurrent spinor fields, conformally flat Walker metrics and the classification of 2-symmetric Lorentzian manifolds are considered.

  18. Managing factoring in banking groups

    OpenAIRE

    2006-01-01

    On the market for factoring services independent suppliers coexhist with companies affiliated with banking groups. The last ones can be oriented in their decision processes by the policies of their parent company, usually a bank. They could also benefit from synergies among the different units of the group. The main benefits are linked to cost reduction, better skill-based resources allocation and a higher amount of financial coverage. If such interdependencies are found ...

  19. Fifteenth LAMPF users group meeting

    Energy Technology Data Exchange (ETDEWEB)

    Cochran, D.R.F. (comp.)

    1982-03-01

    The Fifteenth LAMPF Users Group Meeting was held November 2-3, 1981 at the Clinton P. Anderson Meson Physical Facility. The program of papers scheduled to be presented was amended to include a Report from Washington by Clarence R. Richardson, US Department of Energy. The general meeting ended with a round-table working group discussion concerning the Planning for a Kaon Factory. Individual items from the meeting were prepared separately for the data base.

  20. The EWMA Patient Outcome Group

    DEFF Research Database (Denmark)

    Gottrup, F

    2009-01-01

    Across Europe, clinical experts in wound care and industry representatives have joined forces to propose recommendations for clinical data collection on chronic wound management. Here, the chair of the group, Finn Gottrup, outlines its main objectives.......Across Europe, clinical experts in wound care and industry representatives have joined forces to propose recommendations for clinical data collection on chronic wound management. Here, the chair of the group, Finn Gottrup, outlines its main objectives....