Origin of ophiolite complexes related to intra-oceanic subduction initiation: implications of IODP Expedition 352 (Izu-Bonin fore arc)

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Robertson, Alastair; Avery, Aaron; Carvallo, Claire; Christeson, Gail; Ferré, Eric; Kurz, Walter; Kutterolf, Steffen; Morgan, Sally; Pearce, Julian; Reagan, Mark; Sager, William; Shervais, John; Whattam, Scott; International Ocean Discovery Program Expedition 352 (Izu-Bonin-Mariana Fore Arc), the Scientific Party of

2015-04-01

Ophiolites, representing oceanic crust exposed on land (by whatever means), are central to the interpretation of many orogenic belts (e.g. E Mediterranean). Based mostly on geochemical evidence, ophiolites are widely interpreted, in many but by no means all cases, as having formed within intra-oceanic settings above subduction zones (e.g. Troodos ophiolite, Cyprus). Following land geological, dredging and submersible studies, fore arcs of the SW Pacific region became recognised as likely settings of supra-subduction zone ophiolite genesis. This hypothesis was tested by recent drilling of the Izu-Bonin fore arc. Four sites were drilled, two on the outer fore arc and two on the upper trench slope. Site survey seismic data, combined with borehole data, indicate that three of the sites are located in fault-controlled sediment ponds that formed in response to dominantly down-to the-west extensional faulting (with hints of preceding top-to-the-east compressional thrusting). The sediments overlying the igneous basement, of maximum Late Eocene to Recent age, document ash and aeolian input, together with mass wasting of the fault-bounded sediment ponds. At the two more trenchward sites (U1440 and U1441), mostly tholeiitic basalts were drilled, including massive and pillowed lavas and hyaloclastite. Geochemically, these extrusives are of near mid-oceanic ridge basalt composition (fore arc basalts). Subtle chemical deviation from normal MORB can be explained by weakly fluid-influenced melting during decompression melting in the earliest stages of supra-subduction zone spreading (not as 'trapped' older MORB). The remaining two sites, c. 6 km to the west (U1439 and U1442), penetrated dominantly high-magnesian andesites, known as boninites, largely as fragmental material. Their formation implies the extraction of highly depleted magmas from previously depleted, refractory upper mantle in a supra-subduction zone setting. Following supra-subduction zone spreading, the active

Deformation of the Songshugou ophiolite in the Qinling orogen

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Sun, Shengsi; Dong, Yunpeng

2017-04-01

The Qinling orogen, middle part of the China Central Orogenic Belt, is well documented that was constructed by multiple convergences and subsequent collisions between the North China and South China Blocks mainly based on geochemistry and geochronology of ophiolites, magmatic rocks as well as sedimentary reconstruction. However, this model is lack of constraints from deformation of subduction/collision. The Songshugou ophiolite outcropped to the north of the Shangdan suture zone represents fragments of oceanic crust and upper mantle. Previous works have revealed that the ophiolite was formed at an ocean ridge and then emplaced in the northern Qinling belt. Hence, deformation of the ophiolite would provide constraints for the rifting and subduction processes. The ophiolite consists chiefly of metamorphosed mafic and ultramafic rocks. The ultramafic rocks contain coarse dunite, dunitic mylonite and harzburgite, with minor diopsidite veins. The mafic rocks are mainly amphibolite, garnet amphibolite and amphibole schist, which are considered to be eclogite facies and retrograde metamorphosed oceanic crust. Amphibole grains in the mafic rocks exhibit a strong shape-preferred orientation parallel to the foliation, which is also parallel to the lithologic contacts between mafic and ultramafic rocks. Electron backscattered diffraction (EBSD) analyses show strong olivine crystallographic preferred orientations (CPO) in dunite including A-, B-, and C-types formed by (010)[100], (010)[001] and (100)[001] dislocation slip systems, respectively. A-type CPO suggests high temperature plastic deformation in the upper mantle. In comparison, B-type may be restricted to regions with significantly high water content and high differential stress, and C-type may also be formed in wet condition with lower differential stress. Additionally, the dunite evolved into amphibolite facies metamorphism with mineral assemblages of olivine + talc + anthophyllite. Assuming a pressure of 1.5 GPa

Evaluation of Heterotrophy in in Serpentinite-Associated Waters from the Coast Range Ophiolite, Northern California, USA and the Zambales Ophiolite, Philippines

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Scott, T. J.; Arcilla, C. A.; Cardace, D.; Hoehler, T. M.; McCollom, T. M.; Meyer-Dombard, D. R.; Schrenk, M. O.

2013-12-01

The deep biosphere in cold, dark sub-seafloor ultramafic rocks (i.e., those rocks rich in Fe and Mg) is stressed by exceedingly high pH, transient, if any, inorganic carbon availability, and little known organic carbon inventories. As a test of heterotrophic carbon use, serpentinite-associated waters (from groundwater sampling wells and associated surface seepages in tectonically uplifted mantle units in ophiolites) were tested for differences with respect to aqueous geochemistry and performance in EcoPlates™ - Biolog Inc. .. This work focuses on two field locations for water sampling: the Coast Range Ophiolite, CA, USA, and the Zambales Ophiolite, Philippines. Characteristics of each sampling site are presented (pH, mineral substrate, Ca2+/Mg2+ ratio, aqueous metal loads, etc.). Complementary EcoPlate™ results [prefabricated 96-well plates, seeded with triplicate experiments for determining microbiological community response to difference organic carbon sources; a triplicate control experiment with just water is built in to the plate also] are also presented. We found that waters from selected California [groundwater wells (7 discrete wells) and related surface seeps (5 hydrologically connected sites)] and Philippines [4 Zambales Ophiolite springs/seepages] sourced in serpentinites were analyzed. EcoPlate™ average well-color development (AWCD), which demonstrates microbial activities averaged per plate (as in Garland and Mills, 1991), differs across sites. Correlations of AWCD with environmental data (such as pH, oxidation-reduction potential or ORP, Ca2+/Mg2+ ratio, and Fe contents) are evaluated. Clarifying the geochemical-biological relationships that bear out in these analyses informs discourse on the energetic limits of life in serpentinizing systems, with relevance to ultramafic-hosted life on continents and in the seabed.

Spinel and plagioclase peridotites of the Nain ophiolite (Central Iran): Evidence for the incipient stage of oceanic basin formation

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Pirnia, Tahmineh; Saccani, Emilio; Arai, Shoji

2018-06-01

The Nain ophiolites crop out along the western border of the central East Iran Microcontinent (CEIM) and consist of an ophiolitic mélange in which pargasite-bearing spinel and plagioclase mantle lherzolites are largely represented. Whole-rock and mineral chemistry data suggest that these rocks record the complex history of the asthenospheric and lithospheric mantle evolution. The spinel lherzolites have experienced low-degree ( 5%) partial melting and contain clinopyroxenes with positive Eu anomalies (Eu/Eu* = 1.10-1.48) suggesting that the partial melting occurred under oxidized conditions (fayalite-magnetite-quartz -0.8 to +1.3). The pargasite and coexisting clinopyroxene in these rocks are depleted in light rare earth elements (LREE) (mean chondrite-normalized CeN/SmN = 0.045). The depleted chemistry of this amphibole reflects metasomatism during interaction with H2O-rich subalkaline mafic melts, most likely concurrently with or after the partial melting of the spinel lherzolites. The plagioclase lherzolites were subsequently formed by the subsolidus recrystallization of spinel lherzolites under plagioclase facies conditions as a result of mantle uprising, as evidenced by: (1) the development of plagioclase rims around the spinels; (2) plagioclase + orthopyroxene exsolution textures within some clinopyroxene grains; (3) an increase in plagioclase modal content coupled with an increase in modal olivine and a decrease in modal pyroxene and pargasite; (4) coincident decreases in Al, Mg, and Ni, and increases in Cr, Ti, and Fe in spinel, as well as decreases in Al and Ca, and increases in Cr and Ti in pyroxene and pargasite; and (5) the identical whole rock compositions of the spinel and plagioclase lherzolites, which rules out a magmatic origin for the plagioclase in these units. The Nain lherzolites have similar whole-rock and mineral geochemical compositions to subcontinental peridotites that are typically representative of Iberia-type rifted continental margins

Geology of the Zambales ophiolite, Luzon, Philippines

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Rossman, D.L.; Castanada, G.C.; Bacuta, G.C.

1989-01-01

The Zambales ophiolite of western Luzon, Philippines, exposes a typical succession of basalt flows, diabasic dikes, gabbro and tectonized harzburgite. The age established by limiting strata is late Eocene. Lack of evidence of thrust faulting and the general domal disposition of the lithologie units indicate that the ophiolitic rocks are exposed by uplift. Highly complex internal layered structures within the complex are related to processes developed during formation of the ophiolite and the Zambales ophiolite may be one of the least disturbed (by emplacement) ophiolitic masses known. The exposed mass trends north and the upper surface plunges at low angles (a few degrees) to the north and south. The chemistry and composition of the rocks in the northwest part of the Zambales area (Acoje block) is distinct from that in the southeastern segment (Coto block). The Acoje block, according to Evans (1983) and Hawkins and Evans (1983), resembles (on a chemical basis) arc-tholeiite series rocks from intra-island arcs and the rocks in the Coto block are typical back-arc basin rock series. The present writer believes that the ophiolite composes a single genetic unit and that the changes in composition are the result of changes that took place during the initial formation. The gabbro probably formed below a spreading center in an elongate, in cross section, V-shaped, magma chamber. The gabbro is estimated by the writer to be less than 2 km thick and may be less than 1 km in places. Numerous erosional windows through the gabbro in the northern and eastern side of the Zambales area show that the gabbro remaining in those areas is likely to be only a few hundred meters thick. Harzburgite is exposed to a depth of about 800 m in the Bagsit River area and this may be the deepest part of the ophiolite accessible for study on which there is any control on depth. A transitional zone, about 200 m thick lying between the gabbro and harzburgite, is composed of serpentinized dunite

Beginning the Modern Regime of Subduction Tectonics in Neoproterozoic time: Inferences from Ophiolites of the Arabian-Nubian Shield

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Stern, R.

2003-04-01

It is now clear that the motive force for plate tectonics is provided by the sinking of dense lithosphere in subduction zones. Correspondingly, the modern tectonic regime is more aptly called ``subduction tectonics" than plate tectonics, which only describes the way Earth's thermal boundary layer adjusts to subduction. The absence of subduction tectonics on Mars and Venus implies that special circumstances are required for subduction to occur on a silicate planet. This begs the question: When did Earth's oceanic lithosphere cool sufficiently for subduction to began? This must be inferred from indirect lines of evidence; the focus here is on the temporal distribution of ophiolites. Well-preserved ophiolites with ``supra-subduction zone" (SSZ) affinities are increasingly regarded as forming when subduction initiates as a result of lithospheric collapse (± a nudge to get it started), and the formation of ophiolitic lithosphere in evolving forearcs favors their emplacement and preservation. The question now is what percentage of ophiolites with ``supra-subduction zone" (SSZ) chemical signatures formed in forearcs during subduction initiation events? Most of the large, well-preserved ophiolites (e.g., Oman, Cyprus, California, Newfoundland) may have this origin. If so, the distribution in space and time of such ophiolites can be used to identify ``subduction initiation" events, which are important events in the evolution of plate tectonics. Such events first occurred at the end of the Archean (˜2.5Ga) and again in the Paleoproterozoic (˜1.8 Ga), but ophiolites become uncommon after this. Well-preserved ophiolites become abundant in Neoproterozoic time, at about 800±50 Ma. Ophiolites of this age are common and well-preserved in the Arabian-Nubian Shield (ANS) of Egypt, Sudan, Ethiopia, Eritrea, and Saudi Arabia. ANS ophiolites mostly contain spinels with high Cr#, indicating SSZ affinities. Limited trace element data on pillowed lavas supports this interpretation

The Othris Ophiolite, Greece: A snapshot of subduction initiation at a mid-ocean ridge

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Barth, M.G.; Mason, P.R.D.; Davies, G.R.; Drury, M.R.

2008-01-01

The mantle section of the Tethyan-type Othris Ophiolite, Greece, records tectono-magmatic processes characteristic of both mid-ocean ridges and supra-subduction zones. The Othris Ophiolite is a remnant of the Jurassic Neotethys Ocean, which existed between Eurasia and Gondwanaland. Othris

Multi-scale Onland-Offshore Investigations of the New Caledonia Ophiolite, SW Pacific

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Clerc, C. N.; Collot, J.; Sevin, B.; Patriat, M.; Etienne, S.; Iseppi, M.; Lesimple, S.; Jeanpert, J.; Mortimer, N. N.; Poli, S.; Pattier, F.; Juan, C.; Robineau, B.; Godard, M.; Cluzel, D.

2017-12-01

The Peridotite Nappe of New Caledonia is one of the largest ultramafic ophiolite in the World: it represents about one quarter of the 500 x 80 km island of Grande Terre. This extensive upper mantle unit was tectonically emplaced during the Eocene onto the northeastern edge of Zealandia continent. It is weakly deformed because it was not involved in a collision belt after obduction. A dome-shaped Eocene HP/LT metamorphic complex was exhumed across the fore-arc mantle lithosphere in the northern tip of the island. Post-obduction Miocene to Present coral reefs developed in shallow waters around Grande Terre and surrounding islands. In the perspective of a possible onshore/offshore drilling project (IODP/ICDP), we present recent advances in our understanding of offshore extensions of this ophiolite. To the south of New Caledonia, the offshore continuation of the ultramafic allochthon has been identified by dredges and by its geophysical signature as a continuous linear body that extends over a distance of more than 400 km at about 2000m bsl. Such water depths allow an unprecedented seismic reflection imaging of a drowned and well-preserved ophiolite. Seismic profiles show that the nappe has a flat-top, and is capped by carbonate reefs and dissected by several major normal faults. To the east of this presumed ultramafic body, Felicité Ridge is a 30 km wide, 350 km long, dome-shaped ridge, which may be interpreted as the possible southern extension of the HP/LT metamorphic complex observed onshore. Onshore, several 150 to 200 m long cores were drilled in the ophiolite and airborne electromagnetic allowed high-resolution imaging down to 400 m depth. These recent results allow identification of internal thrusts within the peridotite body and more superficial landslides. The analysis of polyphase fracturation and associated serpentinization brings new constraints on the tectonic evolution of the ophiolite and its subsequent weathering pattern. We integrate these data and

Structural evolution of the Semail Ophiolite metamorphic sole, Wadi Hawasina and Northern Jebel Nakhl Culmination, Oman

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Hurtado, C.; Bailey, C.; Visokay, L.; Scharf, A.

2017-12-01

The Semail ophiolite is the world's largest and best-exposed ophiolite sequence, however the processes associated with both oceanic detachment and later emplacement onto the Arabian continental margin remain enigmatic. This study examines the upper mantle section of the ophiolite, its associated metamorphic sole, and the autochthonous strata beneath the ophiolite at two locations in northern Oman. Our purpose is to understand the structural history of ophiolite emplacement and evaluate the deformation kinematics of faulted and sheared rocks in the metamorphic sole. At Wadi Hawasina, the base of the ophiolite is defined by a 5- to 15-m thick zone of penetratively-serpentinized mylonitic peridotite. Kinematic indicators record top-to-the SW (reverse) sense-of-shear with a triclinic deformation asymmetry. An inverted metamorphic grade is preserved in the 300- to 500-m thick metamorphic sole that is thrust over deep-water sedimentary rocks of the Hawasina Group. The study site near Buwah, in the northern Jebel Nakhl culmination, contains a N-to-S progression of mantle peridotite, metamorphic sole, and underlying Jurassic carbonates. Liswanite crops out in NW-SE trending linear ridges in the peridotite. The metamorphic sole includes well-foliated quartzite, metachert, and amphibolite. Kinematic evidence indicates that the liswanite and a serpentinized mélange experienced top to-the north (normal) sense-of-shear. Two generations of E-W striking, N-dipping normal faults separate the autochthonous sequence from the metamorphic sole, and also cut out significant sections of the metamorphic sole. Fabric analysis reveals that the metamorphic sole experienced flattening strain (K<0.2) that accumulated during pure shear-dominated general shear (Wk<0.4). Normal faulting and extension at the Buwah site indicates that post-ophiolite deformation is significant in the Jebel Akhdar and Jebel Nakhl culminations.

Sulfide mineralization in ultramafic rocks of the Faryab ophiolite complex, southern Kerman

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Mohammad Ali Rajabzadeh

2015-10-01

Full Text Available Introduction Worldwide, Ni-Cu and PGE magmatic sulfide deposits are confined to the lower parts of stratiform mafic and ultramafic complexes. However, ophiolite mafic and ultramafic complexes have been rarely explored for sulfide deposits despite the fact that they have been extensively explored and exploited for chromite. Sulfide saturation during magmatic evolution is necessary for sulfide mineralization, in which sulfide melts scavenge chalcophile metals from the parent magma and concentrate them in specific lithological zones. The lack of exploration for sulfides in this environment suggests that sulfide saturation is rarely attained in ophiolite-related magmas. Some ophiolites, however, contain sulfide deposits, such as at Acoje in Philippines, and Cliffs in Shetland, U.K. (Evans, 2000; Naldrett, 2004. The Faryab ophiolite complex in southern Kerman Province, the most important mining area for chromite deposits in Iran, is located in the southwest part of the Makran Zone. Evidence of sulfide mineralization has been reported there by some authors (e.g. Rajabzadeh and Moosavinasab, 2013. This paper discusses the genesis of sulfides in the Faryab ophiolite using mineral chemistry of the major mineral phases in different rocks of the ophiolite column in order to determine the possible lithological location of sulfide deposits. Materials and methods Seventy three rock samples from cumulate units were collected from surficial occurrences and drill core. The samples were studied using conventional microscopic methods and the mineralogy confirmed by x-ray diffraction. Electron microprobe analysis was carried out on different mineral phases in order to determine the chemistry of the minerals used in the interpretation of magma evolution in the Faryab ophiolite. Lithologically, the Faryab ophiolite complex is divided into two major parts: the northern part includes magmatic rocks and the southern part is comprised of rocks residual after partial

Lower Cretaceous Xigaze ophiolites formed in the Gangdese forearc : Evidence from paleomagnetism, sediment provenance, and stratigraphy

NARCIS (Netherlands)

Huang, Wentao; van Hinsbergen, Douwe J J; Maffione, Marco; Orme, Devon A.; Dupont-Nivet, Guillaume; Guilmette, Carl; Ding, Lin; Guo, Zhaojie; Kapp, Paul

2015-01-01

The India-Asia suture zone of southern Tibet exposes Lower Cretaceous Xigaze ophiolites and radiolarian cherts, and time-equivalent Asian-derived clastic forearc sedimentary rocks (Xigaze Group). These ophiolites have been interpreted to have formed in the forearc of the north-dipping subduction

Contrasting thermal and melting histories for segments of mantle lithosphere in the Nahlin ophiolite, British Columbia, Canada

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McGoldrick, Siobhan; Canil, Dante; Zagorevski, Alex

2018-03-01

The Permo-Triassic Nahlin ophiolite is the largest and best-preserved ophiolite in the Canadian Cordillera of British Columbia and Yukon, Canada. The ophiolite is well-exposed along its 150 km length with mantle segments divisible into the Hardluck and Menatatuline massifs. Both massifs comprise mostly depleted spinel harzburgite (exchange temperatures in the mantle of the ophiolite also change systematically along strike with the degree of partial melt depletion. The temperatures recorded by REE and Ca-Mg exchange between coexisting pyroxenes require markedly higher peak temperatures and cooling rates for the Menatatuline massif (1250 °C, 0.1-0.01 °C/year) compared to the Hardluck massif (rates controlled by presence or absence of a crustal section above the mantle lithosphere, or by rapid exhumation along a detachment.

Eclogite nappe-stack in the Grivola-Urtier Ophiolites (Southern Aosta Valley, Western Alps)

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Tartarotti, Paola

2013-04-01

In the Western Alpine chain, ophiolites represent a section of the Mesozoic Tethys oceanic lithosphere, involved in subduction during the convergence between the paleo-Africa and paelo-Europe continents during the Cretaceous - Eocene. The Western Alpine ophiolites consist of several tectonic units, the most famous being the Zermatt-Saas and Combin nappes, and other major ophiolite bodies as the Voltri, Monviso, and Rocciavrè that show different rock assemblages and contrasting metamorphic imprints. The Grivola-Urtier (GU) unit is exposed in the southern Aosta Valley, covering an area of about 100 km2; it is tectonically sandwiched between the continentally-derived Pennidic Gran Paradiso Nappe below, and the Austroalpine Mount Emilius klippe above. This unit has been so far considered as part of the Zermatt-Saas nappe extending from the Saas-Fee area (Switzerland) to the Aosta Valley (Italy). The GU unit consists of serpentinized peridotites that include pods and boudinaged layers of eclogitic Fe-metagabbro and trondhjemite, rodingites and chloriteschists transposed in the main foliation together with calcschists and micaschists. All rocks preserve particularly fresh eclogitic mineral assemblages. The contact between the serpentinites and calcshists is marked by a tectonic mélange consisting of mylonitic marble and calcschist with stretched and boudinaged serpentinite blocks. Continentally-derived allochthonous blocks ranging in size from100 meters to meters are also included within the ophiolites. New field, petrographic and geochemical data reveal the complex nature of the fossil Tethyan oceanic lithosphere exposed in the southern Aosta Valley, as well as the extent and size of the continental-oceanic tectonic mélange. The geological setting of the GU unit is here inferred as a key tool for understanding the complex architecture of the ophiolites in the Western Alps.

Tracing alteration of mantle peridotite in the Samail ophiolite using Mg isotopes

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de Obeso, J. C.; Kelemen, P. B.; Higgins, J. A.

2017-12-01

Magnesium is one of the main constituents of mantle peridotite ( 22.8 wt%), which has a homogeneous Mg isotopic composition (d26Mg = -0.25 ± 0.04 ‰ (2 sd) DSM3, Teng et al 2010 GCA). Mg isotopes are used as tracers of continental and oceanic weathering as they exhibit variable degrees of fractionation during alteration depending on the lithology. Here we report some of the first Mg isotopic compositions of the mantle section of the Samail ophiolite in Oman and its alteration products. The mantle section of the ophiolite is composed mainly of depleted harzburgites and dunites with mantle-like d26Mg (-0.25, -0.21 ‰). Mantle peridotite is far from equilibrium in near surface conditions leading to rapid, extensive serpentinization, carbonation and oxidation, as well as other geochemical changes. Our analyzed samples encompass most of the alteration of peridotite products observed in Oman including listvenites (completely carbonated peridotite) near the basal thrust of the ophiolite, massive magnesite veins within peridotite outcrops, and heavily altered harzburgites. Magnesite listvenites have d26Mg slightly below mantle values (-0.33, -0.33‰) while dolomite listvenites are significantly lighter (-1.46, -0.89‰). This suggests that heavy Mg isotopes were removed from the listvenites during ophiolite emplacement. Heavily altered peridotite from Wadi Fins exhibit alteration halos with drastic changes in composition. The most oxidized areas are enriched in Fe and depleted in Mg compared to the cores of the samples. These variations in Mg concentrations are complemented by a shift to heavy Mg isotopic compositions (0.74, 0.86‰), among the heaviest d26Mg values that have been reported in altered peridotite. Potential sinks for light isotopes removed from such alteration zones are massive magnesite veins with very light compositions (-3.39, -3.14‰). The fractionation of Mg isotopes observed in the mantle section of the ophiolite spans more than 50% of the known

The basal part of the Oman ophiolitic mantle: a fossil Mantle Wedge?

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Prigent, Cécile; Guillot, Stéphane; Agard, Philippe; Godard, Marguerite; Chauvet, Alain; Dubacq, Benoit; Monié, Patrick; Yamato, Philippe

2014-05-01

Although the Oman ophiolite is classically regarded as being the direct analog of oceanic lithosphere created at fast spreading ridges, the geodynamic context of its formation is still highly debated. The other alternative end-member model suggests that this ophiolite entirely formed in a supra-subduction zone setting. Fluids involved in the hydration of the oceanic lithosphere and in the presence of a secondary boninitic and andesitic volcanism may provide a way to discriminate between these two interpretations: are they descending near-axis hydrothermal fluxes (first model) or ascending from a subducting slab (second model)? We herein focus on the base of the ophiolitic mantle in order to characterize the origin of fluids and decipher hydration processes. Samples were taken along hecto- to kilometre-long sections across the basal banded unit directly overlying the amphibolitic/granulitic metamorphic sole. We carried out a petrological, structural and geochemical study on these rocks and their constitutive minerals. Our results show that, unlike the generally refractory character of Oman harzburgites, all the basal mantle rocks display secondary crystallization of clinopyroxene and amphibole through metasomatic processes. The microstructures and the chronology of these secondary mineralizations (clinopyroxene, pargasitic amphibole, antigorite and then lizardite/chrysotile) suggest that these basal rocks have been affected by cooling from mantle temperatures (serpentines (B, Sr, Rb, Ba, As), are consistent with amphibolite-derived fluids (Ishikawa et al., 2005) and cannot be easily explained by other sources. Based on these observations, we propose a geodynamic model in which intense and continuous metasomatism of the cooling base of the ophiolitic mantle is due to the release of fluids coming from the progressive dehydration of underlying amphibolitic rocks. This process is compatible with the progressive subduction of the Arabian margin during the Upper

Origin of Manipur Ophiolite Complex, Indo-Myanmar Range ...

Indian Academy of Sciences (India)

r b

2017-11-20

Nov 20, 2017 ... The Manipur. Ophiolite. Complex: Varying degree of serpentinization and relict pyroxenes. 11/20/2017. 13. Page 14. Serpentinization process preserves the protolith elemental signatures. 11/20/2017. 14 ... The range of Nd isotope ratios in the serpentinized peridotites. 11/20/2017. 17. Kingson et al.

Timing of pyroxenite formation in supra-subduction Josephine Ophiolite, Oregon.

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Hough, T.; Le Roux, V.; Kurz, M. D.

2017-12-01

The Josephine ophiolite is a partly dismembered ophiolite located in southern Oregon and northwestern California (USA). It displays a large ( 640 km2) mantle section that is mostly composed of depleted spinel harzburgite and lherzolite re-equilibrated at temperatures of 900 °C. In addition, the peridotite section of the ophiolite contains minor dunites and pyroxenite veins ranging from orthopyroxenites to clinopyroxenites. Using field, petrological and geochemical data, previous studies have shown that the peridotite experienced 10-20% of hydrous flux melting. In addition, clinopyroxene and orthopyroxene in harzburgites show variable degrees of light rare-earth element (LREE) enrichment, which suggests percolation and re-equilibration with small fractions of boninite melt. Overall, the trace element concentrations of pyroxenes indicate that the harzburgites experienced particularly high degrees of melting in the mantle wedge. We collected a number of orthopyroxenite and clinopyroxenite veins in the mantle section of the Josephine Ophiolite. Here we present the major and rare-earth element (REE) contents of pyroxene in 4 orthopyroxenites and 2 clinopyroxenites and calculate the major element and REE closure temperatures for individual veins. We show that individual pyroxenites record drastic variations in their degree of REE depletion, indicating that multiple generations of melts percolated the peridotite. The pyroxenite veins also record higher REE closure temperatures (>1200 ºC) compared to the surrounding peridotite, potentially indicating rapid cooling after emplacement. REE closure temperatures are also higher than major element closure temperatures. In parallel, we analyzed Sr isotopes by MC-ICPMS in pyroxene separates from 4 veins. Results indicate that the maximum age of emplacement of orthopyroxenite veins corresponds to the age of exhumation. Some clinopyroxenites may have formed during earlier melt percolation events. This study supports the idea that

Slab and Sediment Melting during Subduction Initiation: Mantle Plagiogranites from the Oman Ophiolite

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Rollinson, H. R.

2014-12-01

Granitoid dykes up to several hundred metres wide and 2 km long are found in depleted harzburgites in the mantle section of the Oman ophiolite. They vary in composition from tonalite to potassic granite and are generally more potassic than the crustal plagiogranites found within the sheeted dyke complex higher up within the ophiolite stratigraphy. Some granites are strongly peraluminous and contain garnet and andalusite. They are geochemically variable, some with REE that are relatively unfractionated ((La/Yb)n= 3.5-6.0, flat middle to heavy REE, steep light REE) to those which are highly fractionated ((La/Yb)n= 28-220). On primitive-mantle normalised plots some have very high concentrations of fluid-mobile elements - Cs, Rb, Th, U and Pb. Few have significant Ta-Nb anomalies. On the Ca-Fe-Mg-Ti discrimination diagram of Patino Douce (J. Petrol., 1999) whole-rock compositions define a spectrum between felsic-pelite derived melts and amphibolite-derived melts. There is a chemical similarity between the least REE fractionated plagiogranites (generally tonalites and granodiorites) and melts of an amphibolitic parent. This is supported by the occurrence of mafic xenoliths in some dykes, the presence of hornblende and highly calcic cores (up to An85) in some plagioclase grains. Trace element modelling using Oman Geotimes lavas as the starting composition indicates that melting took place in the garnet stability field, although enrichment in the melt in Cs, Rb, Ba and Pb suggests that there was another component present in addition to the mafic parent. Other plagiogranites (trondhjemites and granites) have a strongly peraluminous chemistry and mineralogy and geochemical similarities with the Himalayan leucogranites implying that they were derived from a sedimentary protolith. These mantle plagiogranites are more prevalent in the northern outcrops of the ophiolite. The volume of granitoid melt and the depth of melting preclude their derivation from the sole of the

Syndeformation Chrome Spinels Inclusions in the Plastically Deformed Olivine Aggregates (Kraka Ophiolites, the Southern Urals

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D. E. Saveliev

2015-12-01

Full Text Available This article presents the results of structural, petrographic, mineralogical and chemical studies of dunite veinlets in spinel peridotite from the Kraka ophiolites. It is demonstrated that plastic deformation of polycrystalline olivine, which form dunite, was accompanied by precipitation of impurities (aluminum and chrome as newly formed chrome spinels. The thinnest acicular inclusions of 0.3-0.5 micron thick are aligned in olivine grains along [010] axis. Bigger elongated irregular chrome spinel grains usually occur along grain and sub-grain olivine boundaries, and, occasionally, inside the grains along [100] axis. Alteration from the fine xenomorphic grains of chrome spinels to the bigger idiomorphic crystals was observed. Analogically to dynamic ageing (dispersion hardening in metals, the structural and chemical alterations in dunites are interpreted as deformation induced segregation of impurities. It is suggested that the euhedral chrome spinel grains typical for ophiolitic dunites were formed by coalescence and spheroidization. This process may be a key factor in the formation of ophiolitic chrome ore deposits.

Vestiges of Submarine Serpentinization Recorded in the Microbiology of Continental Ophiolite Complexes

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Schrenk, M. O.; Sabuda, M.; Brazelton, W. J.; Twing, K. I.

2017-12-01

The study of serpentinization-influenced microbial ecosystems at and below the seafloor has accelerated in recent years with multidisciplinary drilling expeditions to the Atlantis Massif (X357), Southwest Indian Ridge (X360) and Mariana Forearc (X366). In parallel, a number of studies have surveyed serpentinizing systems in ophiolite complexes which host a range of geologic histories, geochemical characteristics, fluid pathways, and consequently microbiology. As ophiolite complexes originate as seafloor materials, it is likely that a microbiological record of seafloor serpentinization processes is maintained through the emplacement and weathering of continental serpentinites. This hypothesis was evaluated through a global comparison of continental serpentinite springs and groundwater, ranging from highly brackish (saline) to freshwater. One of the most saline sites, known as the Coast Range Ophiolite Microbial Observatory (CROMO), was used as a point-of-comparison to marine serpentinizing systems, such as the Lost City Hydrothermal Field. Although there was little taxonomic overlap between microbial populations in marine and terrestrial systems, both communities harbored an abundance of genes involved in sulfur metabolism, including sulfide oxidation, thiosulfate disproportionation, and sulfate reduction. The phylogeny of key genes involved in these metabolic processes was evaluated relative to published studies and compared between sites. Together, these data provide insights into both the functioning of microbial communities in modern-day serpentinizing systems, and the transport processes that disperse microorganisms between marine and terrestrial serpentinites.

Magnetic properties of serpentinized peridotites from the Zedong ophiolite, Yarlung-Zangbo suture zone, SE Tibet

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Li, Z.; Zheng, J.; Moskowitz, B. M.; Xiong, Q.; Liu, Q.

2017-12-01

Serpentinized mantle peridotites are widely supposed to be significant sources of the magnetic, gravity and seismic anomalies in mid-oceanic ridges, forearcs and suture zones. However, the relationship between the magnetic properties of variably serpentinized peridotites and the serpentinization process is still under debate. Ophiolite outcrops commonly comprise peridotites in different stages of serpentinization and these ophiolitic peridotites are ideal to investigate the magnetic signatures of suture zones. The Zedong ophiolite locates in the eastern part of the Yarlung-Zangbo suture zone, SE Tibet (China), and the peridotite massif represents the remnants of the Neo-Tethyan lithospheric mantle. The harzburgite and lherzolite samples show densities between 3.316 and 2.593 g cm-3, and vary from the freshest to >90% serpentinized peridotites. The magnetic susceptibility curves from room temperature to 700ºC mainly show the Curie temperatures of 585ºC for pure magnetite. The low-temperature (20-300 K) demagnetization curves show the Verwey transitions at 115-125 K, suggesting that magnetite is also the dominant remanence-carrying phase. The hysteresis data of the peridotites fall in the region of pseudo-single-domain (PSD) and follow the theoretical trends for mixtures of single domain (SD) and multidomain (MD) magnetite. The first-order reversal curve (FORC) diagrams suggest that the magnetite is dominantly interacting SD + PSD particles for S 40% serpentinized samples. The susceptibility and saturation magnetization of the Zedong peridotites range from 0.9 to 30.8 × 10‒3 (SI) and 14.1 to 1318 × 10‒3 Am2 kg‒1, respectively, and both show consistent trends with increasing degrees of serpentinization. The S serpentinization of ophiolitic peridotites, whereas the S > 40% peridotites have higher susceptibilities of 0.02-0.03 (SI) and fall in the region of abyssal peridotites. Our results suggest that the Zedong ophiolitic peridotites probably experienced a

Ophiolitic basement to the Great Valley forearc basin, California, from seismic and gravity data: Implications for crustal growth at the North American continental margin

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Godfrey, N.J.; Beaudoin, B.C.; Klemperer, S.L.; Levander, A.; Luetgert, J.; Meltzer, A.; Mooney, W.; Tréhu, A.

1997-01-01

The nature of the Great Valley basement, whether oceanic or continental, has long been a source of controversy. A velocity model (derived from a 200-km-long east-west reflection-refraction profile collected south of the Mendocino triple junction, northern California, in 1993), further constrained by density and magnetic models, reveals an ophiolite underlying the Great Valley (Great Valley ophiolite), which in turn is underlain by a westward extension of lower-density continental crust (Sierran affinity material). We used an integrated modeling philosophy, first modeling the seismic-refraction data to obtain a final velocity model, and then modeling the long-wavelength features of the gravity data to obtain a final density model that is constrained in the upper crust by our velocity model. The crustal section of Great Valley ophiolite is 7-8 km thick, and the Great Valley ophiolite relict oceanic Moho is at 11-16 km depth. The Great Valley ophiolite does not extend west beneath the Coast Ranges, but only as far as the western margin of the Great Valley, where the 5-7-km-thick Great Valley ophiolite mantle section dips west into the present-day mantle. There are 16-18 km of lower-density Sierran affinity material beneath the Great Valley ophiolite mantle section, such that a second, deeper, "present-day" continental Moho is at about 34 km depth. At mid-crustal depths, the boundary between the eastern extent of the Great Valley ophiolite and the western extent of Sierran affinity material is a near-vertical velocity and density discontinuity about 80 km east of the western margin of the Great Valley. Our model has important implications for crustal growth at the North American continental margin. We suggest that a thick ophiolite sequence was obducted onto continental material, probably during the Jurassic Nevadan orogeny, so that the Great Valley basement is oceanic crust above oceanic mantle vertically stacked above continental crust and continental mantle.

Geodynamic evolution of the Sabzevar zone, northern central Iranian micro-continent

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Omrani, Hadi; Moazzen, Mohssen; Oberhänsli, Roland

2018-02-01

The Northern Central Iranian Micro-continent (CIM) represents Neotethys-related oceanic crust remnants, emplaced due to convergence between CIM and Eurasia plates during Eocene. Mafic and ultramafic units are exposed along the northern part of the CIM in the Sabzevar area. The geology and field relation of Sabzevar ophiolite indicate northward subduction of the Sabzevar basin. The average whole rock chemistry of mafic (gabbros) and ultramafic samples (lherzolite, harzburgite and dunite) is characterized by a range of MgO of 11.16-31.88, CaO 5.22-11.53 and Al2O3 2.77-14.57, respectively. Low LREE/HREE ratio of ultramafic samples is accompanied by enrichment of large ion lithophile elements (LILE) such as Sr, Pb and K. Mafic samples show two distinct groups with low and high LREE/HREE ratios. The spider diagram of mafic samples indicates enrichment in Sr, Pb and K and depletion in REE. Petrological and geochemical evidence and field relations show that the mafic rocks formed in a supra-subduction zone setting. Petrological studies reveal the role of fractional crystallization and assimilation effect by released fluids during subduction related generation of the Sabzevar mafic rocks. We suggest that the studied mafic rocks likely represent the basement of an initial island arc, which was generated in a supra-subduction zone setting within the Neotethys branch of the Sabzevar Ocean at the north of CIM. Copper, gold and chromite mineralizations are studied in relation to island arc setting and supra-subduction environment. Similarities in lithology, ophiolite age and mineralization between Sabzevar ophiolite and Bardaskan-Torbat Heydariyeh ophiolites testify for their separation due to rotation (or faulting) of the Central Iranian Micro-continent.

From an ocean floor wrench zone origin to transpressional tectonic emplacement of the Sithonia ophiolite, eastern Vardar Suture Zone, northern Greece

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Bonev, Nikolay; Filipov, Petyo

2017-12-01

In the Hellenides of northern Greece, the Sithonia back-arc ophiolite constitute an element of the Vardar suture zone against the Chortiatis island arc magmatic suite, the Melissochori Formation and the Serbo-Macedonian Massif further north at the Mesozoic continental margin of Eurasia. A granodiorite from the Chortiatis island arc magmatic suite crystallized at 160 Ma as derived from new U-Pb zircon geochronology and confirms the end of arc magmatic activity that started at around 173 Ma. Located southerly of the Chortiatis island arc magmatic suite, the Sithonia ophiolite had igneous life from 159 to 149 Ma, and the ophiolite interfinger with clastic-carbonate Kimmeridgian sediments. Magmatic structures (i.e., sheeted dykes) in the ophiolite witness for NE-trending rift axis, while the transform faults and fracture zones sketch NW-SE transcurrent transtension-like propagation of the rift-spreading center at Sithonia that is consistent with a dextral wrench corridor already proposed for the ophiolite origin in the eastern Vardar zone. The tectonic emplacement of the Sithonia ophiolite involved dextral ENE to SE strike-slip sense of shear and SW and NE reverse thrust sense of shear on mostly steep foliation S1, subhorizontal lineation L1 and associated variably inclined F1 fold axes. This structural grain and kinematics are shared by adjacent Chortiatis island arc magmatic suite and the Melissochori Formation. The coexistence of strike-parallel and thrust components of displacement along discrete dextral strike-slip shear zones and internal deformation of the mentioned units is interpreted to result from a bulk dextral transpressive deformation regime developed in greenschist-facies metamorphic conditions. The back-arc ocean floor previous structural architecture with faults and fracture zones where Kimmeridgian sediments deposited in troughs was used by discrete strike-slip shear zones in which these sediments involved, and the shear zones become the sites for

Complejo Ojosmin: fragment of ophiolite transamazonian

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Bossi, J.; Pineyro, D. . Email geologia@fagro.edu.uy

2004-01-01

A preliminary geological survey of a previously unknown basic igneous complex in the Padre Alta Terrane (Pat) is presented. We report petrographic, geochemical and stratigraphic data for more than 200 outcrops. Geological evolution of the complex can be described in terms of four main events: (1) formation Pat units around 2000 Ma; (2) granodiorite thrusting onto possible ophiolite ca 1900 Ma ; (3) granophyric magmatism around 1700 Ma(4) intrusion of trachyte dykes. Data available suggest thrusting onto fragment of oceanic crust. Since the described structure presupposes the existence of pre transamazonian continental fragments in the TPA, it is very important to study the area in detail in the future [es

New Paleomagnetic Data From Upper Gabbros Supports Limited Rotation of Central Semail Massif in Oman Ophiolite

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Horst, A. J.; Sarah, T.; Hartley, E.; Martin, J.

2017-12-01

Paleomagnetic data from northern massifs of the Oman ophiolite demonstrate substantial clockwise rotations prior to or during obduction, yet data from southern massifs are recently suggested to be remagnetized during obduction and show subsequent smaller counterclockwise rotations. To better understand paleomagnetic data from the southern massifs, we conducted a detailed paleomagnetic and rock magnetic study of 21 sites in upper gabbros and 5 sites in lower crustal gabbros within the central Semail massif. Samples treated with progressive thermal demagnetization yield interpretable magnetizations with dominant unblocking between 500-580°C that implies characteristic remanent magnetization (ChRM) components carried by low-titanium magnetite and nearly pure magnetite. Rock magnetic and scanning electron microscopy data provide additional support of the carriers of magnetization. ChRMs from sites with samples containing partially-serpentinized olivine are similar to sites with samples lacking olivine, where the carriers appear to be fine magnetite intergrowths in pyroxene. The overall in situ and tilt-corrected mean directions from upper gabbros are distinct from the lower gabbros, from previous data within the massif, and also directions from similar crustal units in adjacent Rustaq and Wadi Tayin massifs. After tilt correction for 10-15° SE dip of the crust-mantle boundary, the mean direction from upper gabbros is nearly coincident with in situ lower gabbros. The tilt-corrected direction from upper gabbros is also consistent with an expected direction from the Late Cretaceous apparent polar wander path for Arabia at the age of crustal accretion ( 95Ma). These results suggest the upper crustal section in Semail has likely only experienced minor tilting since formation and acquisition of magnetization. Due to slow cooling of middle to lower gabbros in fast-spread crust, the lower gabbro sites likely cooled later or after obduction, and thus yield a distinct

Crustal Accretion at Subduction Initiation Along Izu-Bonin-Mariana Arc and the Link to SSZ Ophiolites

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Ishizuka, O.; Tani, K.; Reagan, M. K.; Kanayama, K.; Umino, S.; Harigane, Y.; Sakamoto, I.

2014-12-01

The Izu-Bonin-Mariana (IBM) forearc preserves the earliest arc magmatic history from subduction initiation to the establishment of the arc. Recent investigations have established a bottom to top igneous stratigraphy of: 1) mantle peridotite, 2) gabbroic rocks, 3) a sheeted dyke complex, 4) basaltic pillow lavas (forearc basalts: FAB), 5) boninites and magnesian andesites, 6) tholeiites and calcalkaline arc lavas. This stratigraphy has many similarities to supra-subduction zone (SSZ) ophiolites. One of the most important common characteristics between the SSZ ophiolites and the forearc crust is the occurrence of MORB-like basaltic lavas underlying or accompanying boninites and early arc volcanic suites. A key observation from the IBM forearc is that FAB differs from nearby back-arc lavas in chemical characteristics, including a depletion in moderately incompatible elements. This indicates that FAB is not a pre-existing oceanic basement of the arc, but the first magmatic product after subduction initiation. Sheeted dikes of FAB composition imply that this magmatism was associated with seafloor spreading, possibly triggered by onset of slab sinking. Recognition of lavas with transitional geochemical characteristics between the FAB and the boninites strongly implies genetic linkage between these two magma types. The close similarity of the igneous stratigraphy of SSZ ophiolites to the IBM forearc section strongly implies a common magmatic evolutionary path, i.e., decompressional melting of a depleted MORB-type mantle is followed by melting of an even more depleted mantle with the addition of slab-derived fluid/melt to produce boninite magma. Similarity of magmatic process between IBM forearc and Tethyan ophiolites appears to be reflected on common characteristics of upper mantle section. Peridotite from both sections show more depleted characteristics compared to upper mantle rocks from mid-ocean ridges. Age determinations reveal that first magmatism at the IBM arc

Kinematics of Late Cretaceous subduction initiation in the Neo-Tethys Ocean reconstructed from ophiolites of Turkey, Cyprus, and Syria

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Maffione, Marco; van Hinsbergen, Douwe J. J.; de Gelder, Giovanni I. N. O.; van der Goes, Freek C.; Morris, Antony

2017-05-01

Formation of new subduction zones represents one of the cornerstones of plate tectonics, yet both the kinematics and geodynamics governing this process remain enigmatic. A major subduction initiation event occurred in the Late Cretaceous, within the Neo-Tethys Ocean between Gondwana and Eurasia. Suprasubduction zone ophiolites (i.e., emerged fragments of ancient oceanic lithosphere formed at suprasubduction spreading centers) were generated during this subduction event and are today distributed in the eastern Mediterranean region along three E-W trending ophiolitic belts. Several models have been proposed to explain the formation of these ophiolites and the evolution of the associated intra-Neo-Tethyan subduction zone. Here we present new paleospreading directions from six Upper Cretaceous ophiolites of Turkey, Cyprus, and Syria, calculated by using new and published paleomagnetic data from sheeted dyke complexes. Our results show that NNE-SSW subduction zones were formed within the Neo-Tethys during the Late Cretaceous, which we propose were part of a major step-shaped subduction system composed of NNE-SSW and WNW-ESE segments. We infer that this subduction system developed within old (Triassic?) lithosphere, along fracture zones and perpendicular weakness zones, since the Neo-Tethyan spreading ridge formed during Gondwana fragmentation would have already been subducted at the Pontides subduction zone by the Late Cretaceous. Our new results provide an alternative kinematic model of Cretaceous Neo-Tethyan subduction initiation and call for future research on the mechanisms of subduction inception within old (and cold) lithosphere and the formation of metamorphic soles below suprasubduction zone ophiolites in the absence of nearby spreading ridges.

Petrographical and geochemical properties of plagiogranites and gabbros in Guleman ophiolite

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Ayşe Didem KILIÇ

2009-06-01

Full Text Available Petrographical and geochemical properties of gabbros and plagiogranites of Guleman ophiolite are determined. It was concluded that gabbros can be basic rocks on subduction zone and plagioclase-rich leucocratic rocks (plagiogranite are differentiation products of fractional crystallization of a basic magma in the magma chamber.

A Fragment of Ophiolite Assemblage of Kasargi Lake Area: East-Urals Megazone, Northern Part of the Southern Urals

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D. E. Saveliev

2014-03-01

Full Text Available The results of study of rocks of ophiolite assemblage exposed on the east coast of Kasargi Lake are presented. The ophiolite assemblage is formed with the serpentinised ultramafic rocks of dunite-harzburgite association, which are residual and the shlirenbanded gabbros with a number of later dikes of diabases and porphiritic gabbros. The chemical content of mafic and ultramafic rocks of Kasargi massif shows that they are likely the equivalent rocks encountered within the backarc spreading ridges.

Alteration, age, and emplacement of the Tangihua Complex ophiolite, New Zealand

International Nuclear Information System (INIS)

Nicholson, K.N.; Black, P.M.; Picard, C.; Cooper, P.; Hall, C.M.; Itaya, T.

2007-01-01

The Tangihua Complex, New Zealand, represents an upper sequence of Late Cretaceous oceanic crustal material: massive basalt flows, pillow lavas, and dolerites. Three phases of alteration are preserved within the complex, each characterised by zeolite precipitation, which correlate to stratigraphic position. The mylonitised sole contains greenschist assemblages (c. 325 degrees C) grading upwards into the initial phase of alteration (250-300 degrees C), and is characterised by actinolite, epidote, albite, and Na-rich zeolites. This phase is cut by lower temperature veins of chlorite-smectite and Ca-rich zeolites. The final alteration phase ( + and Ca 2+ rich minerals, including apophyllite and calcite. Disruption of Ar/Ar spectra around 50 Ma correlate with rifting in the Loyalty Basin and initiation of obduction along the Loyalty-Three Kings Ridge system. We suggest that these events resulted in initial dismemberment, alteration, and movement of the ophiolite, whereas Ar/Ar plateaux at 25-35 Ma correspond to ophiolite emplacement and the last phases of alteration. (author). 49 refs., 5 figs., 3 tabs

Strongly foliated garnetiferous amphibolite clasts in ophiolitic melanges, Yarlung Zangbo Suture Zone, Tibet; Early Cretaceous disruption of a back-arc basin?

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Guilmette, C.; Hebert, R.; Wang, C.; Indares, A. D.; Ullrich, T. D.; Dostal, J.; Bedard, E.

2007-12-01

Metre to decameter-size clasts of amphibolite are found embedded in ophiolitic melanges underlying the Yarlung Zangbo Suture Zone Ophiolites, South Tibet, China. These ophiolites and melanges occur at the limit between Indian and Tibetan-derived rocks and represent remnants of an Early Cretaceous intraoceanic supra-subduction zone domain, the Neo-Tethys. In the Saga-Dazuka segment (500 km along-strike), we discovered new occurrences of strongly foliated amphibolites found as clasts in the ophiolitic melange. In garnet-free samples, hornblende is green-blue magnesio-hornblende and cpx is low-Al diopside. In garnet- bearing samples, garnet is almandine with a strong pyrope component (up to 30 mol%) whereas coexisting hornblende is brown Ti-rich tschermakite and clinopyroxene is Al-diopside. Plagioclase composition was ubiquitously shifted to albite during a late metasomatic event. Geochemistry of these rocks indicates that their igneous protoliths crystallized from a slightly differentiated tholeiitic basaltic liquid that did not undergo major fractionation. Trace element patterns reveal geochemical characteristics identical to those of the overlying ophiolitic crust. These are 1) trace element abundances similar to that of N-MORBs or BABBs, 2) a slight depletion of LREE and 3) a moderate to strong Ta-Nb negative anomaly and a slight Ti anomaly. Such characteristics suggest genesis over a spreading center close to a subduction zone, possibly a back-arc basin. Step-heating Ar/Ar plateau ages were obtained from hornblende separates. All ages fall in the range of 123-128 Ma, overlapping the crystallization ages from the overlying ophiolite (126-131 Ma). Pseudosections were built with the THERMOCALC software in the system NCFMASH. Results indicate that the observed assemblage Hb+Pl+Gt+Cpx is stable over a wide range of P-T conditions, between 10-18 kbars and at more than 800°C. Measured mineral modes and solid solution compositions were successfully modeled, indicating

Orogenic, Ophiolitic, and Abyssal Peridotites

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Bodinier, J.-L.; Godard, M.

2003-12-01

"Tectonically emplaced" mantle rocks include subcontinental, suboceanic, and subarc mantle rocks that were tectonically exhumed from the upper mantle and occur:(i) as dispersed ultramafic bodies, a few meters to kilometers in size, in suture zones and mountain belts (i.e., the "alpine," or "orogenic" peridotite massifs - De Roever (1957), Thayer (1960), Den Tex (1969));(ii) as the lower ultramafic section of large (tens of kilometers) ophiolite or island arc complexes, obducted on continental margins (e.g., the Oman Ophiolite and the Kohistan Arc Complex - Coleman (1971), Boudier and Coleman (1981), Burg et al. (1998));(iii) exhumed above the sea level in ocean basins (e.g., Zabargad Island in the Red Sea, St. Paul's islets in the Atlantic and Macquarie Island in the southwestern Pacific - Tilley (1947), Melson et al. (1967), Varne and Rubenach (1972), Bonatti et al. (1981)).The "abyssal peridotites" are samples from the oceanic mantle that were dredged on the ocean floor, or recovered from drill cores (e.g., Bonatti et al., 1974; Prinz et al., 1976; Hamlyn and Bonatti, 1980).Altogether, tectonically emplaced and abyssal mantle rocks provide insights into upper mantle compositions and processes that are complementary to the information conveyed by mantle xenoliths (See Chapter 2.05). They provide coverage to vast regions of the Earth's upper mantle that are sparsely sampled by mantle xenoliths, particularly in the ocean basins and beneath passive continental margins, back-arc basins, and oceanic island arcs.Compared with mantle xenoliths, a disadvantage of some tectonically emplaced mantle rocks for representing mantle compositions is that their original geodynamic setting is not exactly known and their significance is sometimes a subject of speculation. For instance, the provenance of orogenic lherzolite massifs (subcontinental lithosphere versus upwelling asthenosphere) is still debated (Menzies and Dupuy, 1991, and references herein), as is the original setting

Spring and surface water quality of the Cyprus ophiolites

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C. Neal

2002-01-01

Full Text Available A survey of surface, spring and borehole waters associated with the ophiolite rocks of Cyprus shows five broad water types (1 Mg-HCO3, (2 Na-SO4-Cl-HCO3, (3 Na-Ca-Cl-SO4-OH-CO3, (4 Na-Cl-SO4 and (5 Ca-SO4. The waters represent a progression in chemical reactivity from surface waters that evolve within a groundwater setting due to hydrolysis of the basic/ultrabasic rock as modified by CO2-weathering. An increase in salinity is also observed which is due to mixing with a saline end-member (modified sea-water and dissolution of gypsum/anhydrite. In some cases, the waters have pH values greater than 11. Such high values are associated with low temperature serpentinisation reactions. The system is a net sink for CO2. This feature is related not only to the hydrolysis of the primary minerals in the rock, but also to CaCO3 or Ca-Mg-CO3 solubility controls. Under hyperalkaline conditions, virtually all the carbon dioxide is lost from the water due to the sufficiently high calcium levels and carbonate buffering is then insignificant. Calcium sulphate solubility controls may also be operative when calcium and sulphate concentrations are particularly high. Keywords: Cyprus, Troodos, ophiolite, serpentinisation, spring, stream, water quality, bromide, iodine, boron, trace elements, hyperalkaline.

Petrology and Rock Magnetism of the peridotites of Pindos Ophiolite (Greece), insights into the serpentinization process

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Bonnemains, D.; Carlut, J. H.; Mevel, C.; Andreani, M.; Escartin, J.; Debret, B.

2015-12-01

We present a petrological and magnetic study of a suite of serpentinized peridotites from the Pindos ophiolite spanning a wide range in the degree of serpentinization (from ~10 to 100%). The Pindos ophiolite, in Northern Greece, is a portion of Late Triassic oceanic lithosphere obducted during the convergence of the Apulian and Pelagonian micro-continents. This ophiolite is interpreted mainly as the result of a supra-subduction zone spreading process but its complete history remains largely unknown. Therefore, it is not clear when the ultramafic section was exposed to fluid circulation that resulted in its serpentinization. Element partitioning during serpentinization reactions is dependent on parameters such as temperature and water-rock ratio. In particular, they affect the behavior of the iron released by olivine, which can be taken up either by magnetite, serpentine and/or brucite. Analyses of the reaction products are therefore a key to constrain the conditions during the main stage of the alteration. Our study was designed to gain insight on the conditions prevailing during hydration. Our results indicate that even fully serpentinized samples have a very low magnetization and magnetite content. Moreover, microprobe and μXanes results show that serpentine is the main host of iron in the divalent but also trivalent form. These results are compared with a set of data from serpentinized ultramafics sampled from the ocean floors, as well as from various other ophiolites. We suggest that serpentinization at Pindos occurred at relatively low-temperature (less than 200 °C), therefore not at a ridge environment. In addition, we stress that the presence of trivalent iron in serpentine indicates that serpentinization may remain a producer of hydrogen even when very little magnetite is formed.

Reduced gas seepages in ophiolitic complexes: Evidences for multiple origins of the H2-CH4-N2 gas mixtures

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Vacquand, Christèle; Deville, Eric; Beaumont, Valérie; Guyot, François; Sissmann, Olivier; Pillot, Daniel; Arcilla, Carlo; Prinzhofer, Alain

2018-02-01

This paper proposes a comparative study of reduced gas seepages occurring in ultrabasic to basic rocks outcropping in ophiolitic complexes based on the study of seepages from Oman, the Philippines, Turkey and New Caledonia. This study is based on analyses of the gas chemical composition, noble gases contents, stable isotopes of carbon, hydrogen and nitrogen. These seepages are mostly made of mixtures of three main components which are H2, CH4 and N2 in various proportions. The relative contents of the three main gas components show 4 distinct types of gas mixtures (H2-rich, N2-rich, N2-H2-CH4 and H2-CH4). These types are interpreted as reflecting different zones of gas generation within or below the ophiolitic complexes. In the H2-rich type, associated noble gases display signatures close to the value of air. In addition to the atmospheric component, mantle and crustal contributions are present in the N2-rich, N2-H2-CH4 and H2-CH4 types. H2-bearing gases are either associated with ultra-basic (pH 10-12) spring waters or they seep directly in fracture systems from the ophiolitic rocks. In ophiolitic contexts, ultrabasic rocks provide an adequate environment with available Fe2+ and alkaline conditions that favor H2 production. CH4 is produced either directly by reaction of dissolved CO2 with basic-ultrabasic rocks during the serpentinization process or in a second step by H2-CO2 interaction. H2 is present in the gas when no more carbon is available in the system to generate CH4. The N2-rich type is notably associated with relatively high contents of crustal 4He and in this gas type N2 is interpreted as issued mainly from sediments located below the ophiolitic units.

Enriched and depleted characters of the Amnay Ophiolite upper crustal section and the regionally heterogeneous nature of the South China Sea mantle

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Perez, Americus d. C.; Faustino-Eslava, Decibel V.; Yumul, Graciano P.; Dimalanta, Carla B.; Tamayo, Rodolfo A.; Yang, Tsanyao Frank; Zhou, Mei-Fu

2013-03-01

The volcanic section of the Middle Oligocene Amnay Ophiolite in Mindoro, Philippines has previously been shown to be of normalmid-oceanic ridge basalt (NMORB) composition. Here we report for the first time an enriched mantle component that is additionally recorded in this crustal section. New whole rock major and trace element data are presented for nine mafic volcanic rocks from a section of the ophiolite that has not been previously examined. These moderately evolved tholeiitic basalts were found to have resulted from the bulk mixing of ˜10% ocean island basalt components with depleted mantle. Drawing together various geochemical characteristics reported for different rock suites taken as representatives of the South China Sea crust, including the enriched MORB (EMORB) and NMORB of the East Taiwan Ophiolite, the NMORB from previous studies of the Amnay Ophiolite and the younger ocean floor eruptives of the Scarborough Seamount-Reed Bank region, a veined mantle model is proposed for the South China Sea mantle. The NMORB magmatic products are suggested to have been derived from the more depleted portions of the mantle whereas the ocean island basalt (OIB) and EMORB-type materials from the mixing of depleted and veined/enriched mantle regions.

Interpretation of recent gravity profiles over the ophiolite belt, Northern Oman Mountains, United Arab Emirates

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Khattab, M. M.

1993-04-01

The compiled Bouguer gravity anomaly map over parts of the ophiolite rocks of the Northern Oman Mountains suggests the existence of three partially serpentinized nappes: two along the Gulf of Oman coast with axes near Dadnah, near Fujira and the third 17 km SSE of Masafi. Modeling of the subsurface geology, beneath two gravity profiles (Diba-Kalba and Masafi-Fujira), is based on the occurrence (field evidence) of multiphase low-angle thrusting of the members of the Tethyan lithosphere in northern and Oman Mountains. An assumed crustal model at the Arabian continental margin, beneath the Masafi-Fujira profile, is made to explain an intense gravity gradient. Gravity interpretation is not inconsistent with a gliding mechanism for obduction of the ophiolite on this part of the Arabian continental margin.

Controls on rheology of peridotite at a palaeosubduction interface: a transect across the base of the Oman-UAE ophiolite

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Ambrose, T. K.; Wallis, D.; Hansen, L. N.; Waters, D. J.; Searle, M. P.

2017-12-01

Studies of experimentally deformed rocks and small-scale natural shear zones have demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth and promoting grain-size sensitive deformation mechanisms. Such studies are often used to infer a critical role for minor phases in the development of plate boundaries. However, the role of of minor phases in strain localisation at plate boundaries remains to be tested by direct observation. To test the hypothesis that minor phases control strain localisation at plate boundaries, we conducted microstructural analyses of peridotite samples collected across the base of the Oman-UAE ophiolite. The base of the ophiolite is marked by the Semail thrust, which represents the now exhumed contact between subducted oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the opportunity to directly examine a former plate boundary. Our results demonstrate that the mean olivine grain size is inversely proportional to the abundance of minor phases (primarily pyroxene), consistent with suppression of grain growth by grain-boundary pinning. Our results also reveal that mean olivine grain size is proportional to CPO strength, suggesting that the fraction of strain accommodated by different deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the inferred deformation conditions the viscosity of olivine was grain-size sensitive. As such, grain size, and thereby the abundance of minor phases, influenced viscosity during subduction-related deformation along the base of the mantle wedge. We calculate that viscosity and strain rate respectively decrease and increase by approximately an order of magnitude towards the base of the ophiolite. Our data indicate that this rheological weakening was primarily the result of more abundant secondary phases near the base of the ophiolite. Our interpretations are consistent with those of

Petrography and mineral chemistry of wehrlites in contact zone of gabbro intrusions and mantle peridotites of the Naein ophiolite

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Farhad Ghaseminejad

2014-10-01

Full Text Available Introduction Geological background Ophiolites have played a major role in our understanding of Earth’s processes ranging from seafloor spreading, melt evolution and magma transport in oceanic spreading centers, and hydrothermal alteration and mineralization of oceanic crust to collision tectonics, mountain building processes, and orogeny. They provide the essential structural, petrological, geochemical, and geochronological evidence to document the evolutionary history of ancient continental margins and ocean basin. Ophiolites include a peridotitic mantle sequence, generally characterized by high-temperature plastic deformation and residual chemistry, and a comagmatic crustal sequence (gabbros, diabase dikes, and submarine basalts, weakly or not deformed. According to this interpretation, ophiolites were allochthonous with respect to their country rocks. They were assembled during a primary accretion stage at an oceanic spreading center, and later tectonically emplaced on a continental margin or island arc (Dilek, 2003. The indigenous dikes of pyroxenites and gabbros that were injected into a melting peridotite, or intrusive dikes of pyroxenite and gabbro that injected when the peridotite was fresh and well below its solidus, are discussed in different ophiolite papers. Pyroxenite formation and contact of gabbro and mantle peridotite are discussed in different articles (Dilek, 2003. When a gabbro intrude a fresh mantle peridotite could not significantly react with it, but if intrusion occurs during the serpentinization, the gabbro will change to rodingite. Geological setting The Naein ophiolitic melanges comprise the following rock units: mantle peridotites (harzburgite, lherzolite, dunite, with associated chromitite, gabbro, pyroxenite, sheeted and swarm dikes, massive basalts, pillow lava, plagiogranite, radiolarian chert, glaubotruncana limestone, rodingite, listvenite, and metamorphic rocks (foliated amphibolitic dike, amphibolite, skarn

The internal structure of eclogite-facies ophiolite complexes: Implications from the Austroalpine outliers within the Zermatt-Saas Zone, Western Alps

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Weber, Sebastian; Martinez, Raul

2016-04-01

The Western Alpine Penninic domain is a classical accretionary prism that formed after the closure of the Penninic oceans in the Paleogene. Continental and oceanic nappes were telescoped into the Western Alpine stack associated with continent-continent collision. Within the Western Alpine geologic framework, the ophiolite nappes of the Zermatt-Saas Zone and the Tsate Unit are the remnants of the southern branch of the Piemonte-Liguria ocean basin. In addition, a series of continental basement slices reported as lower Austroalpine outliers have preserved an eclogitic high-pressure imprint, and are tectonically sandwiched between these oceanic nappes. Since the outliers occur at an unusual intra-ophiolitic setting and show a polymetamorphic character, this group of continental slices is of special importance for understanding the tectono-metamorphic evolution of Western Alps. Recently, more geochronological data from the Austroalpine outliers have become available that make it possible to establish a more complete picture of their complex geological history. The Lu-Hf garnet-whole rock ages for prograde growth of garnet fall into the time interval of 52 to 62 Ma (Weber et al., 2015, Fassmer et al. 2015), but are consistently higher than the Lu-Hf garnet-whole rock ages from several other locations throughout the Zermatt-Saas zone that range from 52 to 38 Ma (Skora et al., 2015). This discrepancy suggests that the Austroalpine outliers may have been subducted earlier than the ophiolites of the Zermatt-Saas Zone and therefore have been tectonically emplaced into their present intra-ophiolite position. This points to the possibility that the Zermatt-Saas Zone consists of tectonic subunits, which reached their respective pressure peaks over a prolonged time period, approximately 10-20 Ma. The pressure-temperature estimates from several members of the Austroalpine outliers indicate a complex distribution of metamorphic peak conditions, without ultrahigh

Plagiogranites as late-stage immiscible liquids in ophiolite and mid-ocean ridge suites - An experimental study

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Dixon, S.; Rutherford, M. J.

1979-01-01

A study of relationships between basic and acidic rocks was made by fractionating primitive basalt at low pressure anhydrous conditions at various fugacities. Fractionally crystallized basalt became increasingly enriched in iron which became silicate liquid immiscible, producing Fe-enriched basaltic and granitic liquids. The latter is similar to plagiogranites found in mid-oceanic rift (MOR) regions, showing that silicate liquid immiscibility could be the petrogenic process which produces plagiogranites in some MOR regions and ophiolites. The major problem in considering plagiogranites as products of silicate liquid immiscibility is absence of any description of the Fe-enriched conjugate liquid in the ophiolite or MOR literature, and the identification of this magma is essential for a definite case of silicate liquid immiscibility.

Circum-Pacific accretion of oceanic terranes to continental blocks: accretion of the Early Permian Dun Mountain ophiolite to the E Gondwana continental margin, South Island, New Zealand

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Robertson, Alastair

2016-04-01

Accretionary orogens, in part, grow as a result of the accretion of oceanic terranes to pre-existing continental blocks, as in the circum-Pacific and central Asian regions. However, the accretionary processes involved remain poorly understood. Here, we consider settings in which oceanic crust formed in a supra-subduction zone setting and later accreted to continental terranes (some, themselves of accretionary origin). Good examples include some Late Cretaceous ophiolites in SE Turkey, the Jurassic Coast Range ophiolite, W USA and the Early Permian Dun Mountain ophiolite of South Island, New Zealand. In the last two cases, the ophiolites are depositionally overlain by coarse clastic sedimentary rocks (e.g. Permian Upukerora Formation of South Island, NZ) that then pass upwards into very thick continental margin fore-arc basin sequences (Great Valley sequence, California; Matai sequence, South Island, NZ). Field observations, together with petrographical and geochemical studies in South Island, NZ, summarised here, provide evidence of terrane accretion processes. In a proposed tectonic model, the Early Permian Dun Mountain ophiolite was created by supra-subduction zone spreading above a W-dipping subduction zone (comparable to the present-day Izu-Bonin arc and fore arc, W Pacific). The SSZ oceanic crust in the New Zealand example is inferred to have included an intra-oceanic magmatic arc, which is no longer exposed (other than within a melange unit in Southland), but which is documented by petrographic and geochemical evidence. An additional subduction zone is likely to have dipped westwards beneath the E Gondwana margin during the Permian. As a result, relatively buoyant Early Permian supra-subduction zone oceanic crust was able to dock with the E Gondwana continental margin, terminating intra-oceanic subduction (although the exact timing is debatable). The amalgamation ('soft collision') was accompanied by crustal extension of the newly accreted oceanic slab, and

Reconstructing Plate Boundaries in the Jurassic Neo-Tethys From the East and West Vardar Ophiolites (Greece and Serbia)

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Maffione, Marco; van Hinsbergen, Douwe J. J.

2018-03-01

Jurassic subduction initiation in the Neo-Tethys Ocean eventually led to the collision of the Adria-Africa and Eurasia continents and the formation of an 6,000 km long Alpine orogen spanning from Iberia to Iran. Reconstructing the location and geometry of the plate boundaries of the now disappeared Neo-Tethys during the initial moments of its closure is instrumental to perform more realistic plate reconstructions of this region, of ancient ocean basins in general, and on the process of subduction initiation. Neo-Tethyan relics are preserved in an ophiolite belt distributed above the Dinaric-Hellenic fold-thrust belt. Here we provide the first quantitative constraints on the geometry of the spreading ridges and trenches active in the Jurassic Neo-Tethys using a paleomagnetically based net tectonic rotation analysis of sheeted dykes and dykes from the West and East Vardar Ophiolites of Serbia (Maljen and Ibar) and Greece (Othris, Pindos, Vourinos, and Guevgueli). Based on our results and existing geological evidence, we show that initial Middle Jurassic ( 175 Ma) closure of the western Neo-Tethys was accommodated at a N-S trending, west dipping subduction zone initiated near and parallel to the spreading ridge. The West Vardar Ophiolites formed in the forearc parallel to this new trench. Simultaneously, the East Vardar Ophiolites formed above a second N-S to NW-SE trending subduction zone located close to the European passive margin. We tentatively propose that this second subduction zone had been active since at least the Middle Triassic, simultaneously accommodating the closure of the Paleo-Tethys and the back-arc opening of Neo-Tethys.

Protrusive intrusion, dehydration and polymorphism in minerals as possible reason of seismic activity, relation between ophiolite belts and seismic zonation of the territory of Armenia

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Harutyunyan, A. V.; Petrosyan, H. M.

2010-05-01

seismic zonation, location of the ophiolite belts and petrophisical section three-dimensional model of the Earth crust has been created. The full coincidence of both most seismic hazardous zones (M= 7.0-7,5) and both ophiolite belts with deep faults is noted. Comparing the results of research at high temperatures and pressures, and seismological data may somewhat highlight the formation of earthquake sources at deep horizons of the crust in the territory of Armenia. In ophiolite belts the earthquake sources up to depth of 35km (roof of serpentizied layer) may be caused by permanent protrusive intrusion of serpentized masses and their dehydration. In other regions of Armenia especially in the central flexur the earthquake sources located at the depth of 10-20km may be triggered by polymorphous transformations in minerals. Therefore, there is the possibility of earthquake source physics definition which understanding may allow to bring nearer the solution of earthquake prediction problem.

Uranium-lead isotopic ages of the Samail ophiolite, Oman, with applicatons to Tethyan ocean ridge tectonics

International Nuclear Information System (INIS)

Tilton, G.R.; Hopson, C.A.; Wright, J.E.

1981-01-01

Plagiogranites are a minor but widespread component of the Samail ophiolite plutonic member. They crystallized from the most fractionated melts generated by magmatic crystallization and differentiation of a steady state magma chamber beneath the Tethyan spreading ocean ridge, and their ages are thought to mark the time of ocean crust formation. Isotopic U--Pb ages of zircons from 13 plagiogranites collected along a 270-km segment of the Samail ophiolite subparallel to the regional trend of the sheeted dike complex (the former spreading ridge axis direction) define a narrow time interval of 93.5--97.9 m.y., with a pronounced clustering about 95 m.y. The zircon ages of the plagiogranites agree remarkably well with the early Cenomanian to early Turonian biostratigraphic ages of sediments that are intercalated within the ophiolite pillow lavas and that lie just above them (Tippit et al., 1981). The agreement of radiometric and biostratigraphic ages provides strong support for the conclusion that the plagiogranite U--Pb ages closely date the time span of ocean crust formation. No step changes in age patterns are observed along the ridge axis (sheeted dike) direction, suggesting that there are no major internal offsets of the ophiolite by transform or other faults along most of the traverse. One possible exception occurs at the southeastern end of the sampled interval (Ibra area), where a 3 m.y. discontinuity might be caused by an unmapped fault. Assuming that the regional trend of the sheeted dikes (N10 0 --25 0 W) marks the direction of the former spreading ridge axis, the present array of sample localities spans a distance of 130 to 195 km normal to that axis (i.e., in the spreading direction). The data as a whole do not define a clear-cut age trend normal to the spreading axis, but by eliminating samples that may be aberrant due to faulting, the data array suggests a pattern of increasing ages from east to west

Chemistry of chromites from Arroio Grande Ophiolite (Dom Feliciano Belt, Brazil) and their possible connection with the Nama Group (Namibia)

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Ramos, Rodrigo Chaves; Koester, Edinei; Porcher, Carla Cristine

2017-12-01

The present paper shows a mineral chemistry study in chromites found in serpentine-talc schists of the Arroio Grande Ophiolite, located in the southeastern Dom Feliciano Belt, near the Brazil/Uruguay border. Using electron microscope scanning and electron microprobe techniques, this study found a supra-subduction zone signature in the chromites, together with evidence of metasomatism. It corroborates previous hypothesis that suggested a supra-subduction zone origin for the protoliths of the Arroio Grande meta-igneous rocks and a metasomatic origin for the chromite-bearing magnesian schists. The studied chromites present high Cr# (0.65-0.77) and Fe2+# (0.88-0.95), low MgO (0.85-2.47 wt%) and TiO2 (0.01-0.19 wt%) and anomalous high concentration of ZnO (up to 1.97 wt%). The results were compared with chemical data from detrital chromites from the Schwarzrand and Fish River Subgroups of the Nama Group (Namibia), demonstrating that they are compositionally similar with those found in the latter. These chromites, in turn, are believed to have been derived from the oceanic Marmora Terrane (Gariep Belt) in the west (present-day coordinates). Taking into consideration that oceanic metamafites from both the latter and the Arroio Grande Ophiolite share common bulk-rock geochemical features (in this paper interpreted as fragments of the same paleo-ocean floor - the Marmora back-arc basin), it is possible to raise the hypothesis that detrital material derived from the studied ophiolite might also be found in Nama Group. It is reinforced by the fact that sediments (related to the Pelotas-Aiguá Batholith granitoids) derived from the easternmost Dom Feliciano Belt, i.e. the region where Arroio Grande Ophiolite is located, is found in both Schwarzrand and Fish River Subgroups. Thus, we suggest that Arroio Grande Ophiolite detrital sediments might also have contributed to the Nama Basin infilling during Late Ediacaran-Lower Cambrian.

Synthesis of inverse ringwoodite sheds light on the subduction history of Tibetan ophiolites.

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Bindi, Luca; Griffin, William L; Panero, Wendy R; Sirotkina, Ekaterina; Bobrov, Andrey; Irifune, Tetsuo

2018-04-03

Tibetan ophiolites are shallow mantle material and crustal slabs that were subducted as deep as the mantle transition zone, a conclusion supported by the discovery of high-pressure phases like inverse ringwoodite in these sequences. Ringwoodite, Mg 2 SiO 4 , exhibits the normal spinel structure, with Mg in the octahedral A site and Si in the tetrahedral B site. Through A and B site-disorder, the inverse spinel has four-coordinated A cations and the six-coordinated site hosts a mixture of A and B cations. This process affects the density and impedance contrasts across the boundaries in the transition zone and seismic-wave velocities in this portion of the Earth. We report the first synthesis at high pressure (20 GPa) and high temperature (1600 °C) of a Cr-bearing ringwoodite with a completely inverse-spinel structure. Chemical, structural, and computational analysis confirm the stability of inverse ringwoodite and add further constraints to the subduction history of the Luobusa peridotite of the Tibetan ophiolites.

87Sr enrichment of ophiolitic sulphide deposits in Cyprus confirms ore formation by circulating seawater

International Nuclear Information System (INIS)

Chapman, H.J.; Spooner, E.T.C.

1977-01-01

The hypothesis that seawater was the source of the hydrothermal fluid which formed the Upper Cretaceous ophiolitic cupriferous pyrite ore deposits of the Troodos Massif (Cyprus) has been tested by analysing the strontium isotopic composition of thirteen mineralized samples from four mines. Initial 87 Sr/ 86 Sr ratios range from 0.7052+-0.0001 to 0.7075+-0.00002, the latter value being indistinguishable from that of Upper Cretaceous seawater at 0.7076+-0.0006 (2 sigma). Hence, the mineralized metabasalt samples have been contaminated with 87 Sr, relative to initial magmatic strontium isotope ratios of the Troodos ophiolitic complex (0.70338+-0.00010 to 0.70365+-0.00005). Since seawater was the only source of strontium available during formation of the Troodos Complex which was isotopically relatively enriched in 87 Sr, the data confirm that seawater was the source of the hydrothermal oreforming fluid. (Auth.)

Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia and their provenance

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Gawlick Hans-Jürgen

2017-08-01

Full Text Available Oceanic radiolarite components from the Middle Jurassic ophiolitic mélange between Trnava and Rožanstvo in the Zlatibor Mountains (Dinaridic Ophiolite Belt west of the Drina–Ivanjica unit yield Late Triassic radiolarian ages. The microfacies characteristics of the radiolarites show pure ribbon radiolarites without crinoids or thin-shelled bivalves. Beside their age and the preservation of the radiolarians this points to a deposition of the radiolarites on top of the oceanic crust of the Neo-Tethys, which started to open in the Late Anisian. South of the study area the ophiolitic mélange (Gostilje–Ljubiš–Visoka–Radoševo mélange contains a mixture of blocks of 1 oceanic crust, 2 Middle and Upper Triassic ribbon radiolarites, and 3 open marine limestones from the continental slope. On the basis of this composition we can conclude that the Upper Triassic radiolarite clasts derive either from 1 the younger parts of the sedimentary succession above the oceanic crust near the continental slope or, more convincingly 2 the sedimentary cover of ophiolites in a higher nappe position, because Upper Triassic ribbon radiolarites are only expected in more distal oceanic areas. The ophiolitic mélange in the study area overlies different carbonate blocks of an underlying carbonate-clastic mélange (Sirogojno mélange. We date and describe three localities with different Upper Triassic radiolarite clasts in a mélange, which occurs A on top of Upper Triassic fore-reef to reefal limestones (Dachstein reef, B between an Upper Triassic reefal limestone block and a Lower Carnian reef limestone (Wetterstein reef, and C in fissures of an Upper Triassic lagoonal to back-reef limestone (Dachstein lagoon. The sedimentary features point to a sedimentary and not to a tectonic emplacement of the ophiolitic mélange (= sedimentary mélange filling the rough topography of the topmost carbonate-clastic mélange below. The block spectrum of the underlying and

Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia) and their provenance

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Gawlick, Hans-Jürgen; Djerić, Nevenka; Missoni, Sigrid; Bragin, Nikita Yu.; Lein, Richard; Sudar, Milan; Jovanović, Divna

2017-08-01

Oceanic radiolarite components from the Middle Jurassic ophiolitic mélange between Trnava and Rožanstvo in the Zlatibor Mountains (Dinaridic Ophiolite Belt) west of the Drina-Ivanjica unit yield Late Triassic radiolarian ages. The microfacies characteristics of the radiolarites show pure ribbon radiolarites without crinoids or thin-shelled bivalves. Beside their age and the preservation of the radiolarians this points to a deposition of the radiolarites on top of the oceanic crust of the Neo-Tethys, which started to open in the Late Anisian. South of the study area the ophiolitic mélange (Gostilje-Ljubiš-Visoka-Radoševo mélange) contains a mixture of blocks of 1) oceanic crust, 2) Middle and Upper Triassic ribbon radiolarites, and 3) open marine limestones from the continental slope. On the basis of this composition we can conclude that the Upper Triassic radiolarite clasts derive either from 1) the younger parts of the sedimentary succession above the oceanic crust near the continental slope or, more convincingly 2) the sedimentary cover of ophiolites in a higher nappe position, because Upper Triassic ribbon radiolarites are only expected in more distal oceanic areas. The ophiolitic mélange in the study area overlies different carbonate blocks of an underlying carbonate-clastic mélange (Sirogojno mélange). We date and describe three localities with different Upper Triassic radiolarite clasts in a mélange, which occurs A) on top of Upper Triassic fore-reef to reefal limestones (Dachstein reef), B) between an Upper Triassic reefal limestone block and a Lower Carnian reef limestone (Wetterstein reef), and C) in fissures of an Upper Triassic lagoonal to back-reef limestone (Dachstein lagoon). The sedimentary features point to a sedimentary and not to a tectonic emplacement of the ophiolitic mélange (= sedimentary mélange) filling the rough topography of the topmost carbonate-clastic mélange below. The block spectrum of the underlying and slightly older

Geochemistry of reduced gas related to serpentinization of the Zambales ophiolite, Philippines

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Abrajano, T.A.; Sturchio, N.C.; Kennedy, B.M.; Lyon, G.L.; Muehlenbachs, K.; Böhlke, J.K.

1990-01-01

Methane-hydrogen gas seeps with mantle-like C and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the Zambales ophiolite, Philippines. New measurements of noble gas and 14C isotope abundances, rock/mixed-volatile equilibrium calculations, and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration. The gas seeps are produced in rock-dominated zones of serpentinization, and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization.

Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case

OpenAIRE

Duretz , Thibault; Agard , Philippe; Yamato , Philippe; Ducassou , Céline; Burov , Evgenii ,; Gerya , T. V.

2016-01-01

International audience; Obduction emplaces regional-scale fragments of oceanic lithosphere (ophiolites) over continental lithosphere margins of much lower density. For this reason, the mechanisms responsible for obduction remain enigmatic in the framework of plate tectonics. We present two-dimensional (2D) thermo-mechanical models of obduction and investigate possible dynamics and physical controls of this process. Model geometry and boundary conditions are based on available geological and g...

Mineral chemistry and petrology of highly magnesian ultramafic cumulates from the Sarve-Abad (Sawlava) ophiolites (Kurdistan, NW Iran): New evidence for boninitic magmatism in intra-oceanic fore-arc setting in the Neo-Tethys between Arabia and Iran

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Allahyari, Khalil; Saccani, Emilio; Rahimzadeh, Bahman; Zeda, Ottavia

2014-01-01

The Sarve-Abad (Sawlava) ophiolitic complex consists of several tectonically dismembered ophiolitic sequences. They are located along the Main Zagros Thrust Zone, which marks the ophiolitic suture between the Arabian and Sanandaj-Sirjan continental blocks. They represent a portion of the southern Neo-Tethyan oceanic lithosphere, which originally existed between the Arabian (to the south) and Eurasian (to the north) continental margins. The Sarve-Abad ophiolites include cumulitic lherzolites bearing minor dunite and chromitite lenses in places. The main rock-forming minerals in ultramafic cumulates are cumulus olivine and inter-cumulus clinopyroxene and orthopyroxene. Minor (<5%) chromian spinel occurs as both cumulus and inter-cumulus phases.

Potential Hydrogen Yields from Ultramafic Rocks of the Coast Range Ophiolite and Zambales Ophiolite: Inferences from Mössbauer Spectroscopy

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Stander, A.; Nelms, M.; Wilkinson, K.; Dyar, M. D.; Cardace, D.

2013-12-01

The reduced status of mantle rocks is a possible controller and indicator of deep life habitat, due to interactions between water and ultramafic (Fe, Mg-rich) minerals, which, under reducing conditions, can yield copious free hydrogen, which is an energy source for rock-hosted chemosynthetic life. In this work, Mössbauer spectroscopy was used to parameterize the redox status of Fe in altering peridotites of the Coast Range Ophiolite (CRO) in California, USA and Zambales Ophiolite (ZO) in the Philippines. Fe-bearing minerals were identified and data were collected for the percentages of Fe(III)and Fe(II)and bulk Fe concentration. Thin section analysis shows that relict primary olivines and spinels generally constitute a small percentage of the ZO and CRO rock, and given satisfactory estimates of the volume of the ultramafic units of the ZO and CRO, a stoichiometric H2 production can be estimated. In addition, ZO serpentinites are ~63,000 ppm Fe in bulk samples; they contain ~41-58% Fe(III)and ~23-34% Fe(II) in serpentine and relict minerals along with ~8-30% of the total Fe as magnetite. CRO serpentinites are ~42,000 ppm Fe in bulk samples; they contain ~15-50% Fe(III), ~22-88% Fe(II) in serpentine and relict minerals, and ~0-52% of total Fe is in magnetite (Fe(II)Fe(III)2O4). Assuming stoichiometric production of H2, and given the following representation of serpentinization 2(FeO)rock + H2O → (Fe2O3)rock +H2, we calculated the maximum quantity of hydrogen released and yet to be released through the oxidation of Fe(II). Given that relatively high Fe(III)/Fetotal values can imply higher water:rock ratios during rock alteration (Andreani et al., 2013), we can deduce that ZO ultramafics in this study have experienced a net higher water:rock ratio than CRO ultramafics. We compare possible H2 yields and contrast the tectonic and alteration histories of the selected ultramafic units. (M. Andreani, M. Muñoz, C. Marcaillou, A. Delacour, 2013, μXANES study of iron

The Armenian and NW Anatolian ophiolites: new insights for the closure of the Tethys domain and obduction onto the South Armenian Block and Anatolian-Tauride Platform before collision through dynamic modeling

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Hässig, Marc; Rolland, Yann; Sosson, Marc; Hassani, Riad; Topuz, Gultekin; Faruk Çelik, Ömer; Gerbault, Muriel; Galoyan, Ghazar; Müller, Carla; Sahakyan, Lilit; Avagyan, Ara

2013-04-01

In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the South Armenian Block (SAB), a Gondwanian-derived continental terrane; (2) scattered outcrops of ophiolites coming up against the Sevan-Akera suture zone; and (3) the Eurasian plate. The Armenian ophiolites represent remnants of an oceanic domain which disappeared during Eurasia-Arabia convergence. Previous works using geochemical whole-rock analyses, 40Ar/39Ar and paleontological dating have shown that the ophiolite outcrops throughout this area were emplaced during the Late Cretaceous as one non-metamorphic preserved ophiolitic nappe of back-arc origin that formed during Middle to Late Jurassic. From these works, tectonic reconstructions include two clearly identified subductions, one related to the Neotethys subduction beneath the Eurasian margin and another to intra-oceanic subduction responsible for the opening of the back-arc basin corresponding to the ophiolites of the Lesser Caucasus. The analysis of the two stages of metamorphism of the garnet amphibolites of the ophiolite obduction sole at Amasia (M1: HT-LP peak of P = 6-7 kbar and T > 630°C; M2; MP-MT peak at P = 8-10 kbar and T = 600°C) has allowed us to deduce the onset of subduction of the SAB at 90 Ma for this locality, which age coincides with other paleontological ages at the obduction front. A preliminary paleomagnetic survey has also brought quantification to the amount of oceanic domain which disappeared by subduction between the SAB and Eurasia before collision. We propose a dynamic finite element model using ADELI to test the incidence of parameters such as the density of the different domains (or the interval between the densities), closing speed (or speeds if sporadic), the importance and interactions of mantle discontinuities with the subducting lithosphere and set a lithospheric model. Our field observations and analyses are used to validate combinations of factors. The aim is to better qualify the

Paleomagnetic Constraints on the Tectonic History of the Mesozoic Ophiolite and Arc Terranes of Western Mexico

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Boschman, L.; Van Hinsbergen, D. J. J.; Langereis, C. G.; Molina-Garza, R. S.; Kimbrough, D. L.

2017-12-01

The North American Cordillera has been shaped by a long history of accretion of arcs and other buoyant crustal fragments to the western margin of the North American Plate since the Early Mesozoic. Accretion of these terranes resulted from a complex tectonic history interpreted to include episodes of both intra-oceanic subduction within the Panthalassa/Pacific Ocean, as well as continental margin subduction along the western margin of North America. Western Mexico, at the southern end of the Cordillera, contains a Late Cretaceous-present day long-lived continental margin arc, as well as Mesozoic arc and SSZ ophiolite assemblages of which the origin is under debate. Interpretations of the origin of these subduction-related rock assemblages vary from far-travelled exotic intra-oceanic island arc character to autochthonous or parautochthonous extended continental margin origin. We present new paleomagnetic data from four localities: (1) the Norian SSZ Vizcaíno peninsula Ophiolite; (2) its Lower Jurassic sedimentary cover; and (3) Barremian and (4) Aptian sediments derived from the Guerrero arc. The data show that the Mexican ophiolite and arc terranes have a paleolatitudinal plate motion history that is equal to that of the North American continent. This suggests that these rock assemblages were part of the overriding plate and were perhaps only separated from the North American continent by temporal fore- or back-arc spreading. These spreading phases resulted in the temporal existence of tectonic plates between the North American and Farallon Plates, and upon closure of the basins, in the growth of the North American continent without addition of any far-travelled exotic terranes.

Magmatic Diversity of the Wehrlitic Intrusions in the Oceanic Lower Crust of the Northern Oman Ophiolite

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Kaneko, R.; Adachi, Y.; Miyashita, S.

2014-12-01

The Oman ophiolite extends along the east coast of Oman, and is the world's largest and best-preserved slice of obducted oceanic lithosphere. The magmatic history of this ophiolite is complex and is generally regarded as having occurred in three stages (MOR magmatism, subduction magmatism and intraplate magmatism). Wehrlitic intrusions constitute an important element of oceanic lower crust of the ophiolite, and numerous intrusions cut gabbro units in the northern Salahi block of this ophiolite. In this study area, we identified two different types of wehrlitic intrusions. One type of the intrusions mainly consists of dunite, plagioclase (Pl) wehrlite and mela-olivine (Ol) gabbro, in which the crystallization sequence is Ol followed by the contemporaneous crystallization of Pl and clinopyroxene (Cpx). This type is called "ordinary" wehrlitic intrusions and has similar mineral compositions to host gabbros (Adachi and Miyashita 2003; Kaneko et al. 2014). Another type of the intrusions is a single intrusion that crops out in an area 250 m × 150 m along Wadi Salahi. This intrusion consists of Pl-free "true" wehrlite, in which the crystallization sequence is Ol and then Cpx. The forsterite contents (Fo%) of Ol from the "ordinary" wehrlitic intrusions and "true" wehrlitic intrusions have ranges of 90.8-87.0 (NiO = 0.36-0.13 wt%) and 84.7 (NiO = 0.31 wt%), respectively. Cr numbers (Cr#) of Cr-spinel from the "true" wehrlitic intrusions show higher Cr# value of 0.85 than those of the "ordinary" wehrlitic intrusions (0.48-0.64). But the former is characterized by very high Fe3+ values (YFe3+ = 0.49-0.68). Kaneko et al. (2014) showed that the "ordinary" ubiquitous type has similar features to MOR magmatism and the depleted type in the Fizh block (Adachi and Miyashita 2003) links to subduction magmatism. These types are distinguished by their mineral chemistries (TiO2 and Na2O contents of Cpx). The TiO2 and Na2O contents of Cpx from the "true" wehrlitic intrusions have 0

A middle Permian ophiolite fragment in Late Triassic greenschist- to blueschist-facies rocks in NW Turkey: An earlier pulse of suprasubduction-zone ophiolite formation in the Tethyan belt

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Topuz, Gültekin; Okay, Aral I.; Schwarz, Winfried H.; Sunal, Gürsel; Altherr, Rainer; Kylander-Clark, Andrew R. C.

2018-02-01

The Eastern Mediterranean region within the Tethyan belt is characterised by two main pulses of suprasubduction-zone ophiolite formation during the Early-Middle Jurassic and Late Cretaceous. Despite vast exposures of the Permo-Triassic accretionary complexes, related suprasubduction-zone ophiolites and the timing of subduction initiation leading to the formation of Permo-Triassic accretionary complexes are unknown so far. Here we report on a 40 km long and 0.3 to 1.8 km wide metaophiolite fragment within transitional greenschist- to blueschist-facies oceanic rocks from NW Turkey. The metaophiolite fragment is made up mainly of serpentinite and minor dykes or stocks of strongly sheared metagabbro with mineral assemblages involving actinolite/winchite, chlorite, epidote, albite, titanite and phengite. The metagabbro displays (i) variable CaO and MgO contents, (ii) anomalously high Mg# (= 100 ∗ molar MgO/(MgO + FeOtot)) of 75-88, and (iii) positive Eu anomalies, together with low contents of incompatible elements such as Ti, P and Zr, suggesting derivation from former plagioclase cumulates. The serpentinites comprise serpentine, ± chlorite, ± talc, ± calcite and relict Cr-Al spinel surrounded by ferrichromite to magnetite. Relict Cr-Al spinels are characterised by (i) Cr/(Cr + Al) ratios of 0.45-0.56 and Mg/(Mg + Fe2 +) ratio of 0.76-0.22, (ii) variable contents of ZnO and MnO, and (iii) extremely low TiO2 contents. Zn and Mn contents are probably introduced into Cr-Al spinels during greenschist- to blueschist metamorphism. Compositional features of the serpentinite such as (i) Ca- and Al-depleted bulk compositions, (ii) concave U-shaped, chondrite-normalised rare earth element patterns (REE) with enrichment of light and heavy REEs, imply that serpentinites were probably derived from depleted peridotites which were refertilised by light rare earth element enriched melts in a suprasubduction-zone mantle wedge. U-Pb dating on igneous zircons from three metagabbro

Genesis and transport of hexavalent chromium in the system ophiolitic rocks - groundwater

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Shchegolikhina, Anastasia; Guadagnini, Laura; Guadagnini, Alberto

2015-04-01

Our study aims at contributing to the quantification and characterization of chromium transport processes from host rocks and soil matrices to groundwater. We focus on dissolved hexavalent chromium detected in groundwaters of geological regions with ophiolitic rocks (ophiolites and serpentinites) inclusions due to its critical ecological impact. (Oze et al., 2004). Despite the large number of analyses on the occurrence of high concentrations of hazardous hexavalent chromium ions in natural waters, only few studies were performed with the objective of identifying and investigating the geochemical reactions which could occur in the natural system rock - groundwater - dissolved chromium (Fantoni et al., 2002, Stephen and James, 2004, Lelli et al., 2013). In this context, there is a need for integration of results obtained from diverse studies in various regions and settings to improve our knowledge repository. Our theoretical analyses are grounded and driven by practical scenarios detected in subsurface reservoirs exploited for civil and industrial use located in the Emilia-Romagna region (Italy). Available experimental datasets are complemented with data from other international regional-scale settings (Altay mountains region, Russia). Modeling of chromium transformation and migration particularly includes characterization of the multispecies geochemical system. A key aspect of our study is the analysis of the complex competitive sorption processes governing heavy metal evolution in groundwater. The results of the research allow assessing the critical qualitative features of the mechanisms of hexavalent chromium ion mobilization from host rocks and soils and the ensuing transformation and migration to groundwater under the influence of diverse environmental factors. The study is then complemented by the quantification of the main sources of uncertainty associated with prediction of heavy metal contamination levels in the groundwater system explored. Fantoni, D

Hydrogen Gas from Serpentinite, Ophiolites and the Modern Ocean Floor as a Source of Green Energy

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Coveney, R. M.

2008-12-01

Hydrogen gas is emitted by springs associated with serpentinites and extensive carbonate deposits in Oman, The Philippines, the USA and other continental locations. The hydrogen springs contain unusually alkaline fluids with pH values between 11 and 12.5. Other workers have described off-ridge submarine springs with comparably alkaline fluid compositions, serpentinite, abundant free hydrogen gas, and associated carbonate edifices such as Lost City on the Atlantis Massif 15 km west of the Mid-Atlantic Ridge (D.S. Kelley and associates, Science 2005). The association of hydrogen gas with ultramafites is a consistent one that has been attributed to a redox couple involving oxidation of divalent iron to the trivalent state during serpentinization, although other possibilities exist. Some of the hydrogen springs on land are widespread. For example in Oman dozens of alkaline springs (Neal and Stanger, EPSL 1983) can be found over thousands of sq km of outcropping ophiolite. While the deposits in Oman and the Philippines are well-known to much of the geochemical community, little interest seems to have been displayed toward either the ophiolitic occurrences or the submarine deposits for energy production. This may be a mistake as the showings because they could lead to an important source of green energy. Widespread skepticism currently exists about hydrogen as a primary energy source. It is commonly said that free hydrogen does not occur on earth and that it is therefore necessary to use other sources of energy to produce hydrogen, obviating the general environmental benefit. However the existence of numerous occurrences of hydrogen gas associated with ophiolites and submarine occurrences of hydrogen suggests the likelihood that natural hydrogen gas may be an important source of clean energy for modern society remaining to be tapped. Calculations in progress should establish whether or not this is likely to be the case.

Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman-UAE ophiolite

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Ambrose, Tyler K.; Wallis, David; Hansen, Lars N.; Waters, Dave J.; Searle, Michael P.

2018-06-01

Studies of experimentally deformed rocks and small-scale natural shear zones have demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth and promoting grain-size sensitive deformation mechanisms. These small-scale studies are often used to infer a critical role for minor phases in the development of plate boundaries. However, the role of minor phases in strain localisation at an actual plate boundary remains to be tested by direct observation. In order to test the hypothesis that minor phases control strain localisation at plate boundaries, we conducted microstructural analyses of peridotite samples collected along a ∼1 km transect across the base of the Oman-United Arab Emirates (UAE) ophiolite. The base of the ophiolite is marked by the Semail thrust, which represents the now exhumed contact between subducted oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the opportunity to directly examine a former plate boundary. Our results demonstrate that the mean olivine grain size is inversely proportional to the abundance of minor phases (primarily orthopyroxene, as well as clinopyroxene, hornblende, and spinel), consistent with suppression of grain growth by grain-boundary pinning. Our results also reveal that mean olivine grain size is proportional to CPO strength (both of which generally decrease towards the metamorphic sole), suggesting that the fraction of strain produced by different deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the inferred deformation conditions, the viscosity of olivine was grain-size sensitive. As such, grain size, and thereby the abundance of minor phases, influenced viscosity during subduction-related deformation along the base of the mantle wedge. We calculate an order of magnitude decrease in the viscosity of olivine towards the base of the ophiolite, which suggests strain was localised near the

Microbial Community Structure in a Serpentine-Hosted Abiotic Gas Seepage at the Chimaera Ophiolite, Turkey.

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Neubeck, Anna; Sun, Li; Müller, Bettina; Ivarsson, Magnus; Hosgörmez, Hakan; Özcan, Dogacan; Broman, Curt; Schnürer, Anna

2017-06-15

The surface waters at the ultramafic ophiolitic outcrop in Chimaera, Turkey, are characterized by high pH values and high metal levels due to the percolation of fluids through areas of active serpentinization. We describe the influence of the liquid chemistry, mineralogy, and H 2 and CH 4 levels on the bacterial community structure in a semidry, exposed, ultramafic environment. The bacterial and archaeal community structures were monitored using Illumina sequencing targeting the 16S rRNA gene. At all sampling points, four phyla, Proteobacteria , Actinobacteria , Chloroflexi , and Acidobacteria , accounted for the majority of taxa. Members of the Chloroflexi phylum dominated low-diversity sites, whereas Proteobacteria dominated high-diversity sites. Methane, nitrogen, iron, and hydrogen oxidizers were detected as well as archaea and metal-resistant bacteria. IMPORTANCE Our study is a comprehensive microbial investigation of the Chimaera ophiolite. DNA has been extracted from 16 sites in the area and has been studied from microbial and geochemical points of view. We describe a microbial community structure that is dependent on terrestrial, serpentinization-driven abiotic H 2 , which is poorly studied due to the rarity of these environments on Earth. Copyright © 2017 Neubeck et al.

Characterization of ophiolites from northern Havana-Matanzas petroleum fields using instrumental neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Montero Cabrera, M.E. E-mail: montero@yakko.cimav.edu.mx; Ortueta Milan, M.; Herrera Peraza, E.F.; Herrera Hernandez, H.; Rodriguez Martinez, N.; Olivares Rieumont, S.; Lopez Reyes, M.C

2001-01-15

Concentrations of 16 elements from 14 serpentinitic samples from Basilio and Cantel petroleum fields were obtained by instrumental neutron activation analysis (INAA): Cr, Co, Ni, La, Nd, Sm, Eu, Gd, Tb, Ce Yb, Lu, Rb, Cs, Hf and Th. Relative INAA was performed using certified reference materials and laboratory standards. Average elemental concentrations showed that the ophiolites have a basic character, suggesting the use of a well-logging method designed for volcano-sedimentary petroleum fields.

Characterization of ophiolites from northern Havana-Matanzas petroleum fields using instrumental neutron activation analysis

International Nuclear Information System (INIS)

Montero Cabrera, M.E.; Ortueta Milan, M.; Herrera Peraza, E.F.; Herrera Hernandez, H.; Rodriguez Martinez, N.; Olivares Rieumont, S.; Lopez Reyes, M.C.

2001-01-01

Concentrations of 16 elements from 14 serpentinitic samples from Basilio and Cantel petroleum fields were obtained by instrumental neutron activation analysis (INAA): Cr, Co, Ni, La, Nd, Sm, Eu, Gd, Tb, Ce Yb, Lu, Rb, Cs, Hf and Th. Relative INAA was performed using certified reference materials and laboratory standards. Average elemental concentrations showed that the ophiolites have a basic character, suggesting the use of a well-logging method designed for volcano-sedimentary petroleum fields

The ophiolite massif of Kahnuj (western Makran, Southern Iran): new geological and geochronological data

International Nuclear Information System (INIS)

Kananian, A.; Juteau, Th.; Bellon, H.; Darvishzadeh, A.; Sabzehi, M.; Whitechurch, H.; Ricou, L.E.

2001-01-01

The ophiolite massif of Kahnuj (600 km 2 ) consists, from bottom to top, of layered gabbros, isotropic gabbros and ouralite gabbros, agmatites of dioritic to plagio-granitic composition, a sheeted dyke complex and lastly a basaltic pillow lava unit. Amphiboles from gabbros were dated ( 40 K- 40 Ar ages) between 156 and 139 Ma and the agmatites are nearly contemporaneous. Potassic granitic veins dated at 93-88 Ma are related to the development of the Ganj arc complex. (authors)

Incipient boninitic arc crust built on denudated mantle: the Khantaishir ophiolite (western Mongolia)

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Gianola, Omar; Schmidt, Max W.; Jagoutz, Oliver; Sambuu, Oyungerel

2017-12-01

The 570 Ma old Khantaishir ophiolite is built by up to 4 km harzburgitic mantle with abundant pyroxenites and dunites followed by 2 km of hornblende-gabbros and gabbronorites and by a 2.5 km thick volcanic unit composed of a dyke + sill complex capped by pillow lavas and some volcanoclastics. The volcanics are mainly basaltic andesites and andesites (or boninites) with an average of 58.2 ± 1.0 wt% SiO2, X Mg = 0.61 ± 0.03 ( X Mg = molar MgO/(MgO + FeOtot), TiO2 = 0.4 ± 0.1 wt% and CaO = 7.5 ± 0.6 wt% (errors as 2 σ). Normalized trace element patterns show positive anomalies for Pb and Sr, a negative Nb-anomaly, large ion lithophile elements (LILE) concentrations between N- and E-MORB and distinctly depleted HREE. These characteristics indicate that the Khantaishir volcanics were derived from a refractory mantle source modified by a moderate slab-component, similar to boninites erupted along the Izu-Bonin-Mariana subduction system and to the Troodos and Betts Cove ophiolites. Most strikingly and despite almost complete outcrops over 260 km2, there is no remnant of any pre-existing MORB crust, suggesting that the magmatic suite of this ophiolite formed on completely denudated mantle, most likely upon subduction initiation. The architecture of this 4-5 km thick early arc crust resembles oceanic crust formed at mid ocean ridges, but lacks a sheeted dyke complex; volcanic edifices are not observed. Nevertheless, low melting pressures combined with moderate H2O-contents resulted in high-Si primitive melts, in abundant hornblende-gabbros and in a fast enrichment in bulk SiO2. Fractional crystallization modeling starting from the observed primitive melts (56.6 wt% SiO2) suggests that 25 wt% pyroxene + plagioclase fractionation is sufficient to form the average Khantaishir volcanic crust. Most of the fractionation happened in the mantle, the observed pyroxenite lenses and layers in and at the top of the harzburgites account for the required cumulate volumes. Finally

A deep hydrothermal fault zone in the lower oceanic crust, Samail ophiolite Oman

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Zihlmann, B.; Mueller, S.; Koepke, J.; Teagle, D. A. H.

2017-12-01

Hydrothermal circulation is a key process for the exchange of chemical elements between the oceans and the solid Earth and for the extraction of heat from newly accreted crust at mid-ocean ridges. However, due to a dearth of samples from intact oceanic crust, or continuous samples from ophiolites, there remain major short comings in our understanding of hydrothermal circulation in the oceanic crust, especially in the deeper parts. In particular, it is unknown whether fluid recharge and discharge occurs pervasively or if it is mainly channeled within discrete zones such as faults. Here, we present a description of a hydrothermal fault zone that crops out in Wadi Gideah in the layered gabbro section of the Samail ophiolite of Oman. Field observations reveal a one meter thick chlorite-epidote normal fault with disseminated pyrite and chalcopyrite and heavily altered gabbro clasts at its core. In both, the hanging and the footwall the gabbro is altered and abundantly veined with amphibole, epidote, prehnite and zeolite. Whole rock mass balance calculations show enrichments in Fe, Mn, Sc, V, Co, Cu, Rb, Zr, Nb, Th and U and depletions of Si, Ca, Na, Cr, Zn, Sr, Ba and Pb concentrations in the fault rock compared to fresh layered gabbros. Gabbro clasts within the fault zone as well as altered rock from the hanging wall show enrichments in Na, Sc, V, Co, Rb, Zr, Nb and depletion of Cr, Ni, Cu, Zn, Sr and Pb. Strontium isotope whole rock data of the fault rock yield 87Sr/86Sr ratios of 0.7046, which is considerably more radiogenic than fresh layered gabbro from this locality (87Sr/86Sr = 0.7030 - 0.7034), and similar to black smoker hydrothermal signatures based on epidote, measured elsewhere in the ophiolite. Altered gabbro clasts within the fault zone show similar values with 87Sr/86Sr ratios of 0.7045 - 0.7050, whereas hanging wall and foot wall display values only slightly more radiogenic than fresh layered gabbro.The secondary mineral assemblages and strontium isotope

Quantification of Tremolite in Friable Material Coming from Calabrian Ophiolitic Deposits by Infrared Spectroscopy

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Antonella Campopiano

2015-01-01

Full Text Available The aim of this study is to identify the infrared absorption band suitable for quantifying tremolite in three powdered samples (fine, medium, and large size classes coming from a quarry of ophiolitic friable rocks in the western part of the Calabria region of Italy. Three IR bands were considered: OH stretching band between 3700 and 3650 cm−1, the stretching bands of the Si-O-Si linkage between 1200 and 900 cm−1, and the absorbance band at 756 cm−1 attributable to tremolite. The amount of tremolite in the test samples was quantified by using the curve parameters of the three analytical bands. The quantitative analysis of tremolite using the band due to OH stretchings (3700–3650 cm−1 and the bands attributed to the Si-O-Si stretchings (1200–900 cm−1 showed high values for all test samples. Their use overestimated the tremolite amount because both bands were affected at the interfering mineral silicates such as talc, kaolinite, chlorite, and serpentinites. The abundant presence of antigorite in studied samples mainly in medium size class sample had a key role in our findings. The band at 756 cm−1 was not affected at the interfering minerals and can be used for quantitative analysis of tremolite in sample coming from ophiolitic deposits.

The recycling of chromitites in ophiolites from southwestern North America

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González-Jiménez, José M.; Camprubí, Antoni; Colás, Vanessa; Griffin, William L.; Proenza, Joaquín A.; O'Reilly, Suzanne Y.; Centeno-García, Elena; García-Casco, Antonio; Belousova, Elena; Talavera, Cristina; Farré-de-Pablo, Júlia; Satsukawa, Takako

2017-12-01

Podiform chromitites occur in mantle peridotites of the Late Triassic Puerto Nuevo Ophiolite, Baja California Sur State, Mexico. These are high-Cr chromitites [Cr# (Cr/Cr + Al atomic ratio = 0.61-0.69)] that contain a range of minor- and trace-elements and show whole-rock enrichment in IPGE (Os, Ir, Ru). That are similar to those of high-Cr ophiolitic chromitites crystallised from melts similar to high-Mg island-arc tholeiites (IAT) and boninites in supra-subduction-zone mantle wedges. Crystallisation of these chromitites from S-undersaturated melts is consistent with the presence of abundant inclusions of platinum-group minerals (PGM) such as laurite (RuS2)-erlichmanite (OsS2), osmium and irarsite (IrAsS) in chromite, that yield TMA ≈ TRD model ages peaking at 325 Ma. Thirty-three xenocrystic zircons recovered from mineral concentrates of these chromitites yield ages (2263 ± 44 Ma to 278 ± 4 Ma) and Hf-O compositions [ɛHf(t) = - 18.7 to + 9.1 and 18O values the mantle via subduction. They were captured by the parental melts of the chromitites when the latter formed in a supra-subduction zone mantle wedge polluted with crustal material. In addition, the Puerto Nuevo chromites have clinopyroxene lamellae with preferred crystallographic orientation, which we interpret as evidence that chromitites have experienced high-temperature and ultra high-pressure conditions (the formation of chromitite in the supra-subduction zone mantle wedge underlying the Vizcaino intra-oceanic arc ca. 250 Ma ago, deep-mantle recycling, and subsequent diapiric exhumation in the intra-oceanic basin (the San Hipólito marginal sea) generated during an extensional stage of the Vizcaino intra-oceanic arc ca. 221 Ma ago. The TRD ages at 325 Ma record a partial melting event in the mantle prior to the construction of the Vizcaino intra-oceanic arc, which is probably related to the Permian continental subduction, dated at 311 Ma.

A new method of discriminating different types of post-Archean ophiolitic basalts and their tectonic significance using Th-Nb and Ce-Dy-Yb systematics

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Emilio Saccani

2015-07-01

Full Text Available In this paper, a new discrimination diagram using absolute measures of Th and Nb is applied to post-Archean ophiolites to best discriminate a large number of different ophiolitic basalts. This diagram was obtained using >2000 known ophiolitic basalts and was tested using ∼560 modern rocks from known tectonic settings. Ten different basaltic varieties from worldwide ophiolitic complexes have been examined. They include two basaltic types that have never been considered before, which are: (1 medium-Ti basalts (MTB generated at nascent forearc settings; (2 a type of mid-ocean ridge basalts showing garnet signature (G-MORB that characterizes Alpine-type (i.e., non volcanic rifted margins and ocean-continent transition zones (OCTZ. In the Th-Nb diagram, basalts generated in oceanic subduction-unrelated settings, rifted margins, and OCTZ can be distinguished from subduction-related basalts with a misclassification rate <1%. This diagram highlights the chemical variation of oceanic, rifted margin, and OCTZ basalts from depleted compositions to progressively more enriched compositions reflecting, in turn, the variance of source composition and degree of melting within the MORB-OIB array. It also highlights the chemical contributions of enriched (OIB-type components to mantle sources. Enrichment of Th relative to Nb is particularly effective for highlighting crustal input via subduction or crustal contamination. Basalts formed at continental margin arcs and island arc with a complex polygenetic crust can be distinguished from those generated in intra-oceanic arcs in supra-subduction zones (SSZ with a misclassification rate <1%. Within the SSZ group, two sub-settings can be recognized with a misclassification rate <0.5%. They are: (1 SSZ influenced by chemical contribution from subduction-derived components (forearc and intra-arc sub-settings characterized by island arc tholeiitic (IAT and boninitic basalts; (2 SSZ with no contribution from subduction

Characterizing and quantifying superparamagnetic magnetite particles in serpentinized mantle peridotite observed in continental ophiolite complexes.

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Ortiz, E.; Vento, N. F. R.; Tominaga, M.; Beinlich, A.; Einsle, J. F.; Buisman, I.; Ringe, E.; Schrenk, M. O.; Cardace, D.

2017-12-01

Serpentinization of mantle peridotite has been recognized as one of the most important energy factories for the deep biosphere. To better evaluate the habitability of the deep biosphere, it is crucial to understand the link between in situ peridotite serpentinization processes and associated magnetite and hydrogen production. Previous efforts in correlating magnetite and hydrogen production during serpentinization processes are based primarily on laboratory experiments and numerical modeling, being challenged to include the contribution of superparamagnetic-sized magnetites (i.e., extremely fine-grained magnetite, petrographically observed as a "pepper flake" like texture in many natural serpentinized rock samples). To better estimate the abundance of superparamagnetic grains, we conducted frequency-dependent susceptibility magnetic measurements at the Institute of Rock Magnetism on naturally serpentinized rock samples from the Coast Range Ophiolite Microbial Observatory (CROMO) in California, USA and the Atlin Ophiolite (British Columbia). In addition, we conducted multiscale EDS phase mapping, BackScattered Electron (BSE) scanning, FIB-nanotomography and STEM-EELS to identify and quantify the superparamagnetic minerals that contribute to the measured magnetic susceptibility signals in our rock samples. Utilizing a multidisciplinary approach, we aim to improve the estimation of hydrogen production based on the abundance of magnetite, that includes the contribution of superparamagnetic particle size magnetite, to ultimately provide a more accurate estimation of bulk deep-biomass hosted by in situ serpentinization processes.

ALPINE MAGMATIC-METALLOGENIC FORMATIONS OF THE NORTHWESTERN AND CENTRAL DINARIDES

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Jakob Pamić

1997-12-01

Full Text Available In the paper are presented basic geological, petrologieca1, geochemi-cal and mineral deposit data for five main magmatic-metallogenic formations of the northwestern and central Dinarides: (lThe Permo Triassic rifting related andesite-diorite formations; (2 The Jurassic-Lower Cretaceous accretionary (ophiolite formations; (3 The Upper Cretaceous-Paleogene subduction related basalt-rhyohite formations; (4 The Paleogene collisional granite formations, and (5 The Oligo-cene-Neogene postsubduction andesite formations. All these magmatic-metallogenic formations originated in different geotectonic settings during the Alpine evolution of the Dinaridic parts of thc Tethys and the postorogenic evolution of the Paratethys and the Pannonian Basin, respectively.

Geochronological constraints on the polycyclic magmatism in the Bou Azzer-El Graara inlier (Central Anti-Atlas Morocco)

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Blein, O.; Baudin, T.; Chèvremont, P.; Soulaimani, A.; Admou, H.; Gasquet, P.; Cocherie, A.; Egal, E.; Youbi, N.; Razin, P.; Bouabdelli, M.; Gombert, P.

2014-11-01

New U-Pb SHRIMP zircon ages from the Bou Azzer-El Graara onlier constrains the Neoproterozoic evolution of the Anti-Atlas during Pan-African orogenesis. Within the Central Anti-Atlas, the Bou Azzer-El Graara inlier exposes a dismembered ophiolite, long considered to mark a late Neoproterozoic suture between the West African Craton in the south, and Neoproterozoic arcs to the north. From north to south, this inlier includes four main geological units: a volcanic-arc, an ophiolite, a metamorphic complex and a continental platform. Several plutons intrude the volcanic-arc, the ophiolite, the metamorphic complex, and post-orogenic volcanic and sedimentary deposits unconformably cover these terranes. The age of the volcanic-arc is reported here for the first time. Analyses of zircon of two rhyolites provide ages of 761 ± 7 Ma and 767 ± 7 Ma. Zircons from two gneisses provide dates of 755 ± 9 Ma and 745 ± 5 Ma. Both dates are considered best estimates of the crystallization ages of their igneous protoliths. Analyses of zircon from two granitic bodies, which crosscut gneisses, provide younger dates of 702 ± 5 Ma and 695 ± 7 Ma. The age of an aplitic body of the ophiolite is reported here for the first time, as 658 ± 8 Ma (SHRIMP U-Pb on zircons). Theses ages suggest the existence of three distinct orogenic events during Cryogenian times: (i) 770-760 Ma Tasriwine-Tichibanine orogeny with rollback of the subducting oceanic plate, leading to the formation of back-arc basins; (ii) 755-695 Ma Iriri-n'Bougmmane orogeny; and (iii) the 660-640 Ma Bou Azzer orogeny involving the formation and the emplacement of the Bou Azer ophiolite. During Ediacaran times, the Bou Azzer-El Graara inlier is characterized with the development of a continental volcanic arc between 630 and 580 Ma (Bou Lbarod Group, 625 ± 8 Ma; Bleïda granodiorite, 586 ± 15 Ma), and strike-slip pull-apart basins (Tiddiline Group, 606 ± 4 Ma and 606 ± 5 Ma). These volcanic and sedimentary Lower Ediacaran

Post-magmatic structural evolution of the Troodos Ophiolite Pillow Lavas revealed by microthermometry within vein precipitates, with application to Alpine-Mediterranean supra-subduction zone settings

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Kurz, W.; Quandt, D.; Micheuz, P.; Krenn, K.

2017-12-01

The Troodos ophiolite, Cyprus, is one of the best preserved ophiolites. Based on geochemical data a supra-subduction zone (SSZ) setting was proposed. Microtextures and fluid inclusions of veins and vesicles within the Pillow Lavas record the post-magmatic structural and geochemical evolution of this SSZ beginning at 75 Ma. Three different vein types from the Upper and Lower Pillow Lavas are distinguished and imply vein precipitation under a dominant extensional regime: (1) syntaxial calcite-, quartz- and zeolite-bearing veins are interpreted as mineralized extension fractures that were pervaded by seawater. This advective fluid flow in an open system changed later into a closed system characterized by geochemical self-organization. (2) Blocky and (3) antitaxial fibrous calcite veins are associated with brecciation due to hydrofracturing and diffusion-crystallization processes, respectively. Based on aqueous fluid inclusion chemistry with seawater salinities in all studied vein types, representative fluid inclusion isochores crossed with calculated litho- and hydrostatic pressure conditions yield mineral precipitation temperatures between 180 and 210 °C, for veins and vesicles hosted in the Upper and Lower Pillow Lavas. This points to a heat source for the circulating seawater and implies that vein and vesicle minerals precipitated shortly after pillow lava crystallization under dominant isobaric cooling conditions. Compared to previous suggestions derived from secondary mineralization a less steep geothermal gradient of 200 °C from the Sheeted Dyke Complex to the Pillow Lavas of the Troodos SSZ is proposed. Further fossil and recent SSZ like the Mirdita ophiolite, Albania, the South-Anatolian ophiolites, Turkey, and the Izu-Bonin fore arc, respectively, reveal similar volcanic sequences. Vein samples recovered during International Ocean Discovery Program expedition 351 and 352 in the Izu-Bonin back and fore arc, respectively, indicate also seawater infiltration

Serpentinite with and without brucite: A reaction pathway analysis of a natural serpentinite in the Josephine ophiolite, California

OpenAIRE

Sonzogni, Yann; Treiman, Allan H.; Schwenzer, Susanne P.

2017-01-01

A partially serpentinized peridotite from the Josephine ophiolite has been studied in detail in order to characterize the chemical processes of its serpentinization. The original rock was harzburgite, and its olivine and orthopyroxene are partially replaced by veins and patches of lizardite serpentine and magnetite; brucite and talc are completely absent from the serpentinite, regardless of whether the precursor mineral was olivine or pyroxene. Petrographic and mineral-chemical data suggest a...

Mineralogy of Surface Serpentinite Outcrops in the Coast Range Ophiolite: Implications for the Deep Biosphere and Astrobiology

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Mccann, A. R.; Cardace, D.; Carnevale, D.; Ehlmann, B. L.

2011-12-01

California contains a number of ultramafic (Fe- and Mg rich) rock bodies, including the Coast Range Ophiolite, a block of oceanic crust and upper mantle tectonically emplaced onto land. These ultramafic rocks are primarily composed of olivine and pyroxene, both of which are stable at the high temperatures and pressures in the deep subsurface where they crystallize but become unstable at low temperature and low pressure conditions near the surface. They are highly reduced rocks, creating chemical disequilibria, which can theoretically provide energy to chemoautotrophic organisms. Serpentinization (serpentine-forming) reactions between the rocks and water produce hydrogen molecules, which can be metabolized by diverse organisms. Earth and Mars have shown evidence of similar early geologic histories, possibly with widespread reducing habitable environments (Schulte et al., 2006). Recent data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) have shown serpentine-bearing outcrops near Nili Fossae (21 N, 282 W) and elsewhere in Mars' cratered highlands. Serpentine-bearing outcrops are rare, but their presence confirms that such systems involving the aqueous alteration of ultramafic rocks were active in the past (specifically during the Noachian epoch (older than ~3.7 billion years), possibly producing aqueous habitats suitable for chemoautotrophic life (Ehlmann et al., 2010). Remotely sensed data cannot confirm whether there is active serpentinization on Mars, however exposed, presently serpentinizing ultramafics in terrestrial ophiolites such as those of the California Coast Range provide points of comparison for similar Martian rocks. Volume expansion during serpentinization fractures the host rock, exposing new reaction surfaces, allowing further serpentinization. If subsurface liquid water is present on Mars, serpentinization may still be occurring. We will provide x-ray diffraction and petrographic data for surface serpentinites from the Coast

Summary of the stratigraphy and structural elements related to plate convergence of the Quetta-Muslim Bagh-Sibi region, Balochistan, west-central Pakistan

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Maldonado, Florian; Mengal, Jan M.; Khan, Shahid H.; Warwick, Peter D.

2011-01-01

Obduction of an ophiolite complex onto the northwestern continental margin of the India plate occurred during the Late Cretaceous to early Paleocene, followed by collision of the ophiolitic complex of the India plate with the Eurasia plate in the Eocene. Lower Eocene marine strata overlie the ophiolitic complex suggesting that suturing was completed by early Eocene time.

Clinopyroxenite dykes within a banded unit in the basal mantle section of the northern part of the Oman ophiolite: A record of the latest deep-seated magmatism

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Ishimaru, Satoko; Arai, Shoji; Tamura, Akihiro

2017-11-01

We found clinopyroxenite dykes in a banded harzburgite block within the Sumeini area in the uppermost part of the metamorphic sole of the northern part of the Oman ophiolite. The dykes clearly cut the deformational structure of the harzburgite and contain its fragments, indicating dyke formation during obduction of the ophiolite. The Mg# [= Mg / (Mg + total Fe)] of clinopyroxenes in the dykes ranges from 0.81 to 0.91, and increases up to 0.93 proximal to harzburgite fragments. Mantle minerals in the harzburgite fragments were modified chemically through interaction with the magma that formed the dyke, yielding lower clinopyroxene and spinel Mg#, and spinels with higher TiO2 contents than those in the unaltered harzburgite. These geochemical features indicate that the clinopyroxenite dykes are cumulates derived from a relatively deep-seated primitive magma enriched in light rare earth elements (LREE) with an ocean island basalt (OIB)-like affinity, geochemically similar to the V3 lavas of an off-ridge origin. Combining these data with geological observations suggests that the clinopyroxenite dykes represent root system of the V3 lavas. Our analyses of the clinopyroxenite dykes testify to the external nature of the V3 magmas, which was added to the sliced oceanic lithosphere from the outside. It is likely that the V3 magma underwent deep-seated crystallization of clinopyroxene and had limited interaction with mantle peridotite en route to the surface. The mode of occurrence of the Sumeini clinopyroxenites (i.e., emplaced into a banded harzburgite block surrounded by garnet amphibolite) is consistent with the generation of OIB-like magmas (V3 lava) beneath the Oman ophiolite resulting from the break-off of the "subducting slab" and subsequent infiltration of hot asthenospheric mantle. This view is consistent with the limited distribution of V3-related rocks in the Oman ophiolite. The production of such OIB-like magmas during ophiolite obduction is not a rare event

Biofilm formation and potential for iron cycling in serpentinization-influenced groundwater of the Zambales and Coast Range ophiolites.

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Meyer-Dombard, D'Arcy R; Casar, Caitlin P; Simon, Alexander G; Cardace, Dawn; Schrenk, Matthew O; Arcilla, Carlo A

2018-05-01

Terrestrial serpentinizing systems harbor microbial subsurface life. Passive or active microbially mediated iron transformations at alkaline conditions in deep biosphere serpentinizing ecosystems are understudied. We explore these processes in the Zambales (Philippines) and Coast Range (CA, USA) ophiolites, and associated surface ecosystems by probing the relevance of samples acquired at the surface to in situ, subsurface ecosystems, and the nature of microbe-mineral associations in the subsurface. In this pilot study, we use microcosm experiments and batch culturing directed at iron redox transformations to confirm thermodynamically based predictions that iron transformations may be important in subsurface serpentinizing ecosystems. Biofilms formed on rock cores from the Zambales ophiolite on surface and in-pit associations, confirming that organisms from serpentinizing systems can form biofilms in subsurface environments. Analysis by XPS and FTIR confirmed that enrichment culturing utilizing ferric iron growth substrates produced reduced, magnetic solids containing siderite, spinels, and FeO minerals. Microcosms and enrichment cultures supported organisms whose near relatives participate in iron redox transformations. Further, a potential 'principal' microbial community common to solid samples in serpentinizing systems was identified. These results indicate collectively that iron redox transformations should be more thoroughly and universally considered when assessing the function of terrestrial subsurface ecosystems driven by serpentinization.

Compositionally heterogeneous podiform chromitite in the Shetland Ophiolite Complex (Scotland): Implications for chromitite petrogenesis and late-stage alteration in the upper mantle portion of a supra-subduction zone ophiolite

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Derbyshire, E. J.; O'Driscoll, B.; Lenaz, D.; Gertisser, R.; Kronz, A.

2013-03-01

The mantle sequence of the ~ 492 Ma Shetland Ophiolite Complex (SOC; Scotland) contains abundant compositionally heterogeneous podiform chromitite bodies enclosed in elongate dunite lenses in the vicinity of the petrological Moho. Chromitite petrogenesis and late-stage alteration events recorded in these seams are examined here using petrography, mineral chemistry and crystal structural data. The resistant nature of Cr-spinel to serpentinisation and other late-stage alteration means that primary igneous compositions are preserved in unaltered crystal cores. Chromitite mineralogy and texture from five sampled localities at The Viels, Hagdale, Harold's Grave, Nikka Vord and Cliff reveal significant inter-pod chemical heterogeneity. The Cr-spinel mineral chemistry is consistent with supra-subduction zone melt extraction from the SOC peridotites. The occurrence of chromitite seams in the centres of the dunite lenses combined with variable Cr-spinel compositions at different chromitite seam localities supports a model of chromitite formation from spatially (and temporally?) fluctuating amounts of melt-rock interaction through channelised and/or porous melt flow. Pervasive serpentinisation of the SOC has led to the almost complete replacement of the primary (mantle) silicate mineral assemblages with serpentine (lizardite with minor chrysotile and antigorite). Magmatic sulphide (e.g., pentlandite) in dunite and chromitite is locally converted to reduced Ni-sulphide varieties (e.g., heazlewoodite and millerite). A post-serpentinisation (prograde) oxidisation event is recorded in the extensively altered Cliff chromitite seams in the west of the studied area, where chromitite Cr-spinel is extensively altered to ferritchromit. The ferritchromit may comprise > 50% of the volume of the Cliff Cr-spinels and contain appreciable quantities of 1-2 μm inclusions of sperrylite (PtAs2) and Ni-arsenide, signifying the coeval formation of these minerals with ferritchromit at

Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

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Poisson, André; Vrielynck, Bruno; Wernli, Roland; Negri, Alessandra; Bassetti, Maria-Angela; Büyükmeriç, Yesim; Özer, Sacit; Guillou, Hervé; Kavak, Kaan S.; Temiz, Haluk; Orszag-Sperber, Fabienne

2016-01-01

We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene-Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments

Geochemistry and Nd-isotope systematics of chemical and terrigenous sediments from the Dun Mountain Ophiolite, New Zealand

International Nuclear Information System (INIS)

Sivell, W.J.

2002-01-01

Two sedimentary associations closely related to temporally discrete ophiolitic magma suites occur within the Early Permian Dun Mountain Ophiolite Belt (DMOB), New Zealand. These are: (1) a suite of diverse chemical sediments and turbidite argillites (TA) that bear an intimate depositional relationship to early-formed pillow lavas (back-arc basin basalts); and (2) a younger, lithic-dominated, bimodal, coarse sandstone-ophiolitic rudite assemblage of proximal turbidite/mass-flow origin, rich in clasts of infant-arc magmas which comprise the bulk of the ophiolite. There are four groups of DMOB chemical sediments. Red hematitic chert (group 1) fills interstices between basalt pillows, and black nodular Fe-Mn deposits (group 2) occur along pillow lava/sediment interfaces. These facies are overlain by red mudstones (group 3), and mottled orange-olive brown mudstones (altered hyaloclastites; group 4). Geochemical features (including REE contents, Fe/Ti and transition ratios) indicate that the cherts reflect silica and metalliferous contributions to sea water, promoted by low-temperature hydrothermal alteration of glassy basalt, while group 4 muds represent residual components in halmyrolytically altered volcanic glass. Transition metal and REE enrichments in group 2 nodules (with high Ce/Ce*, Ni/Fe, and Cu/Fe ratios) reflect hydrogenous chemisorption to a hydothermal component (with high Ba and Sr). The nodules possess ε Nd (T) values (c. 0) identical to those calculated for Permian sea water. Group 3 red muds have lower ε Nd (T) = -1 to -2, and Nd model ages (T) Nd DM) that indicate contributions from continentally derived fluvial particulate fallout of mean Proterozoic age. For the nodules and red muds, strong negative correlations between Mn/Fe, Nd, Ce*/Ce, and ε Nd (T) are attributed to increasing diagenetic influence in the muds. ε Nd (T) values (c. +2) in group 4 muds are transitional toward higher values in their (hyaloclastite) basalt glass precursors

Mineral compositions of plutonic rocks from the Lewis Hills massif, Bay of Islands ophiolite

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Smith, Susan E.; Elthon, Don

1988-01-01

Mineral compositions of residual and cumulate rocks from the Lewis Hills massif of the Bay of Islands ophiolite complex are reported and interpreted in the context of magnetic processes involved in the geochemical evolution of spatially associated diabase dikes. The mineral compositions reflect greater degrees of partial melting than most abyssal peridotites do and appear to represent the most depleted end of abyssal peridotite compositions. Subsolidus equilibration between Cr-Al spinal and olivine generally has occurred at temperatures of 700 to 900 C. The spinel variations agree with the overall fractionation of basaltic magmas producing spinels with progressively lower Cr numbers. The compositions of clinopyroxenes suggest that the fractionation of two different magma series produced the various cumulate rocks.

Serpentinization and fluid-rock interaction in Jurassic mafic and ultramafic sea-floor: constraints from Ligurian ophiolite sequences

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Vogel, Monica; Früh-Green, Gretchen L.; Boschi, Chiara; Schwarzenbach, Esther M.

2014-05-01

The Bracco-Levanto ophiolitic complex (Eastern Liguria) represents one of the largest and better-exposed ophiolitic successions in the Northern Apennines. It is considered to be a fragment of heterogeneous Jurassic lithosphere that records tectono-magmatic and alteration histories similar to those documented along the Mid-Atlantic Ridge, such as at the 15°20'N area and the Atlantis Massif at 30°N. Structural and petrological studies on these rocks provide constraints on metamorphic/deformation processes during formation and hydrothermal alteration of the Jurassic oceanic lithosphere. We present a petrological and geochemical study of deformation processes and fluid-rock interaction in the Bracco-Levanto ophiolitic complex and compare these to modern oceanic hydrothermal systems, such as the Lost City Hydrothermal Field hosted in ultramafic rocks on the Atlantis Massif. A focus is on investigating mass transfer and fluid flow paths during high and low temperature hydrothermal activity, and on processes leading to hydrothermal carbonate precipitation and the formation of ophicalcites, which are characteristic of the Bracco-Levanto sequences. Major element and mineral compositional data allow us to distinguish a multiphase history of alteration characterized by: (1) widespread SiO2 metasomatism during progressive serpentinization, and (2) multiple phases of veining and carbonate precipitation associated with circulation of seawater and high fluid-rock ratios in the shallow ultramafic-dominated portions of the Jurassic seafloor. We observe regional variations in MgO, SiO2 and Al2O3, suggesting Si-flux towards stratigraphically higher units. In general, the ophicalcites have higher Si, Al and Fe concentrations and lower Mg than the serpentinite basement rocks or serpentinites with minimal carbonate veins. Bulk rock trace element data and Sr isotope ratios indicate seawater reacting with rocks of more mafic composition, then channeled towards stratigraphically higher

Comparison of support vector machine and neutral network classification method in hyperspectral mapping of ophiolite mélanges–A case study of east of Iran

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Bahram Bahrambeygi

2017-06-01

Full Text Available Ophiolitic regions are one of the most complex geology settings. Mapping in these parts need broad and precise studies and tools because of the mixture rocks and confusion units. Hyperion hyperspectral sensor data are one of the advanced tools for earth surface mapping that containing rich information of shallow electromagnetic reflection in 242 continuous bands. Because of some contaminated noise in tens of these bands we removed 87 most noisy bands and focused our study on 155 low noisy bands. In present study, tow spectral based classification algorithms of support vector machine and neutral network are compared on hyperion image for classification of cluttered units in an ophiolite set. Study area is Mesina region in collision ophiolitic belt of south east of Iran. In this region for design processing results validation rate, lots of random locations and control points were studied in field scale and were sampled for laboratory surveys. Samples were investigated in microscopic section and by electron microprobe system. Based on laboratory-field studies, the lithology of this area can divided into five general groups: (Melange series, metamorphic units, Oligocene – Miocene to Quaternary volcanic units, lime and flysch units. Based on field-laboratory works, some standard points defined for validate processing results accuracy rate. Therefore, the Support Vector Machine and neutral network method as advanced hyperspectral image processing methods respectively have overall accuracies of 52% and 65%. Consequently the method based neutral network theory for hyperspectral classification have acceptable ratio in separation of blended complicated units.

A Paleozoic Japan-type subduction-accretion system in the Beishan orogenic collage, southern Central Asian Orogenic Belt

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Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Tian, Zhonghua

2015-05-01

Magmatic arcs ascribed to oceanic lithosphere subduction played a dominant role in the construction of the accretionary Central Asian Orogenic Belt (CAOB). The Beishan orogenic collage, situated between the Tianshan Orogen to the west and the Inner Mongolia Orogen to the east, is a key area to understanding the subduction and accretionary processes of the southern CAOB. However, the nature of magmatic arcs in the Beishan and the correlation among different tectonic units along the southern CAOB are highly ambiguous. In order to investigate the subduction-accretion history of the Beishan and put a better spatial and temporal relationship among the tectonic belts along the southern CAOB, we carried out detailed field-based structural geology and LA-ICP-MS zircon U-Pb geochronological as well as geochemical studies along four cross-sections across crucial litho-tectonic units in the central segment of the Beishan, mainly focusing on the metamorphic assemblages and associated plutons and volcanic rocks. The results show that both the plutonic and volcanic rocks have geochemical characteristics similar to those of subduction-related rocks, which favors a volcanic arc setting. Zircons from all the plutonic rocks yield Phanerozoic ages and the plutons have crystallization ages ranging from 464 ± 2 Ma to 398 ± 3 Ma. Two volcanic-sedimentary rocks yield zircons with a wide age range from Phanerozoic to Precambrian with the youngest age peaks at 441 Ma and 446 Ma, estimated to be the time of formation of the volcanic rocks. These new results, combined with published data on ophiolitic mélanges from the central segment of the Beishan, favor a Japan-type subduction-accretion system in the Cambrian to Carboniferous in this part of the Paleo-Asian Ocean. The Xichangjing-Niujuanzi ophiolite probably represents a major suture zone separating different tectonic units across the Beishan orogenic collage, while the Xiaohuangshan-Jijitaizi ophiolitic mélange may represent a

Hydrogen generation during serpentinisation in ophiolite complexes: A comparison of H2-rich gases from Oman, Philippines and Turkey.

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Beaumont, Valérie; Vacquand, Christèle; Deville, Eric; Prinzhofer, Alain

2013-04-01

H2-rich gas seepages in ultrabasic to basic contexts both in marine and continental environment are by-products of serpentinisation. Hydrothermal systems at MOR expose ultrabasic rocks to thermodynamic conditions favouring oxidation of FeII bearing minerals and water reduction. In continental context such thermodynamic conditions do not exist although active serpentinisation occurs in all known ophiolitic complexes (Barnes et al., 1978; Bruni et al., 2002; Cipolli et al., 2004; Boschetti and Toscani, 2008; Marques et al., 2008). Hyperalkaline springs are reported in these contexts as evidence of this active serpentinisation (Barnes et al., 1967) and are often associated with seepages of reduced gases (Neal and Stanger, 1983; Sano et al., 1993). Dry gas seepages are also observed (Abrajano et al., 1988, 1990; Hosgörmez, 2007; Etiope et al., 2011) Such H2-rich gases from ophiolite complexes were sampled in the Sultanate of Oman, the Philippines and Turkey and were analysed for chemical composition, noble gases contents, stable isotopes of carbon, hydrogen and nitrogen. The conditions for present-day serpentinisation in ophiolites were recognised as low temperature processes in Oman with high rock/water ratios (Neal and Stanger, 1985), while the origin of gases is not as univocal for Philippines and Turkey gas seepages. Although, H2 generation is directly linked with FeII oxidation, different reactions can occur during peridotite hydration (McCollom and Bach, 2009; Marcaillou et al., 2011) and serpentine weathering. Produced H2 can react with carbonate species to produce methane via processes that could be biological or abiotic, while carbon availability depends on water recharge chemistry. In the present study, the geochemical properties of gases sampled from three different ophiolite complexes are compared and provide evidence that weathering reactions producing H2 depend on structural, geological, geomorphologic and hydrological local features. REFERENCES Abrajano

Natural flows of H2-rich fluids in the ophiolites of Oman and the Philippines: Tectonic control of migration pathways and associated diagenetic processes

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Deville, E. P.; Prinzhofer, A.; Vacquand, C.; Chavagnac, V.; Monnin, C.; Ceuleneer, G.; Arcilla, C. A.

2009-12-01

We compare the geological environments of sites of emission of natural hydrogen in the Oman ophiolite and the Zambales ophiolite (Luzon, Philippines). The genesis of natural H2 results from the interaction between ultrabasic rocks and aqueous solutions circulating in deep fracture networks, by oxidation of metals (Fe2+, Mn2+) and reduction of water, probably under high temperature conditions. This process generates very reducing conditions capable of destabilizing other molecules (notably reduction of deep CO2 being transformed into CH4 by Fisher-Tropsch type reactions). Nitrogen is also commonly associated to the H2-rich fluids. H2 flows are associated with the expulsion of hyperalkaline waters rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal thrust plane of the ophiolites and the peridotite-gabbro contact (Moho). Within the fracture networks, gas and water separate probably at shallow depth, i.e. close to the top of the upper aquifer level. Locally high flows of gas migrate vertically through fracture pathways and they are able to inflame spontaneously on the surface. Aqueous fluids tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. This water circulation induces a chain of diagenetic reactions starting in the fracture systems and continuing at the surface where it leads to the precipitation of calcite, aragonite, brucite and more rarely portlandite. This chain of diagenetic reactions is associated with the capture of the atmospheric CO2 during the precipitation of carbonates.

Clinopyroxenite dikes crosscutting banded peridotites just above the metamorphic sole in the Oman ophiolite: early cumulates from the primary V3 lava

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Ishimaru, Satoko; Arai, Shoji; Tamura, Akihiro

2013-04-01

Oman ophiolite is one of the well-known ophiolites for excellent exposures not only of the mantle section but also of the crustal section including effusive rocks and the underlying metamorphic rocks. In the Oman ophiolite, three types of effusive rocks (V1, V2 and V3 from the lower sequences) are recognized: i.e., V1, MORB-like magma, V2, island-arc type lava, and V3, intra-plate lava (Godard et al., 2003 and references there in). V1 and V2 lavas are dominant (> 95 %) as effusive rocks and have been observed in almost all the blocks of northern part of the Oman ophiolite (Godard et al., 2003), but V3 lava has been reported only from Salahi area (Alabaster et al., 1982). It is clear that there was a time gap of lava eruption between V1-2 and V3 based on the presence of pelagic sediments in between (Godard et al., 2003). In addition, V3 lavas are fed by a series of doleritic dikes crosscutting V2 lava (Alley unit) (Alabaster et al., 1982). We found clinopyroxenite (CPXITE) dikes crosscutting deformation structure of basal peridotites just above the metamorphic sole in Wadi Ash Shiyah. The sole metamorphic rock is garnet amphibolite, which overlies the banded and deformed harzburgite and dunite. The CPXITE is composed of coarse clinopyroxene (CPX) with minor amount of chlorite, garnet (hydrous/anhydrous grossular-andradite) with inclusions of titanite, and serpentine formed at a later low-temperature stage. The width of the CPXITE dikes is 2-5 cm (10 cm at maximum) and the dikes contain small blocks of wall harzburgite. Almost all the silicates are serpentinized in the harzburgite blocks except for some CPX. The Mg# (= Mg/(Mg + Fe) atomic ratio) of the CPX is almost constant (= 0.94-0.95) in the serpentinite blocks but varies within the dikes, highest at the contact with the block (0.94) and decreasing with the distance from the contact to 0.81 (0.85 on average). The contents of Al2O3, Cr2O3, and TiO2 in the CPX of the dikes are 0.5-2.0, 0.2-0.6, and 0

Mineral textures in Serpentine-hosted Alkaline Springs from the Oman ophiolite

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Giampouras, Manolis; Garcia-Ruiz, Juan Manuel; Bach, Wolfgang; Garrido, Carlos J.; Los, Karin; Fussmann, Dario; Monien, Monien

2017-04-01

Meteoric water infiltration in ultramafic rocks leads to serpentinization and the formation of subaerial, low temperature, hydrothermal alkaline springs. Here, we present a detailed investigation of the mineral precipitation mechanisms and textural features of mineral precipitates, along as the geochemical and hydrological characterization, of two alkaline spring systems in the Semail ophiolite (Nasif and Khafifah sites, Wadi Tayin massif). The main aim of the study is to provide new insights into mineral and textural variations in active, on-land, alkaline vents of the Oman ophiolite. Discharge of circulating fluids forms small-scale, localized hydrological catchments consisting in unevenly interconnected ponds. Three different types of waters can be distinguished within the pond systems: i) Mg-type; alkaline (7.9 11.6), Ca-OH-rich waters; and iii) Mix-type waters arising from the mixing of Mg-type and Ca-type waters (9.6 ponds were carried out by X-ray diffraction (XRD), Raman spectroscopy and field-emission scanning electron microscopy coupled to dispersive energy spectroscopy (FE-SEM-EDS). Aragonite and calcite are the dominant minerals (95 vol.%) of the total mineralogical index in all sites. Mg-type waters host hydrated magnesium carbonates (nesquehonite) and magnesium hydroxycarbonate hydrates (artinite) due to evaporation. Brucite, hydromagnesite and dypingite presence in Mix-type waters is spatially controlled by the hydrology of the system and is localized around mixing zones between Ca-type with Mg-type waters. Residence time of discharging waters in the ponds before mixing has an impact on fluid chemistry as it influences the equilibration time with the atmosphere. Acicular aragonite is the main textural type in hyper-alkaline Ca-type waters, acting as a substratum for the growth of calcite and brucite crystals. Low crystallinity, dumbbell shaped and double pyramid aragonite dominates in Mix-type water precipitates. Rate of supersaturation is essential

Natural analogue studies of bentonite reaction under hyperalkaline conditions. Overview of ongoing work at the Zambales ophiolite, Philippines

International Nuclear Information System (INIS)

Fujii, N.; Yanakawa, M.; Arcilla, C.A.; Pascua, C.; Namiki, K.; Sato, T.; Shikazono, N.; Alexander, W.R.

2011-01-01

Bentonite is one of the safety-critical components of the engineered barrier system for the disposal concepts developed for many types of radioactive waste. However, bentonite - especially the swelling clay component that contributes to its essential barrier functions - is unstable at high pH. To date, results from laboratory tests on bentonite degradation have been ambiguous as the reaction rates are so slow as to be difficult to observe. As such, a key goal in this project is to examine the reaction of natural bentonites in contact with natural hyperalkaline groundwaters to determine if any long-term alteration of the bentonite occurs. Ophiolites have been identified as sources of hyperalkaline groundwaters that can be considered natural analogues of the leachates produced by some cementitious materials in repositories for radioactive waste. At the Zambales ophiolite in the Philippines, widespread active serpentinisation results in hyperalkaline groundwaters with measured pH values of up to 11.7, falling into the range typical of low-alkali cement porewaters. These cements are presently being developed worldwide to minimise the geochemical perturbations which are expected to result from the use of OPC-based concretes (see Kamei et al., this conference, for details). In particular, it is hoped that the lower pH of the low-alkali cement leachates will reduce, or even avoid entirely, the potential degradation of the bentonite buffer which is expected at the higher pH levels (12.5 and above) common to OPC-based concretes. During recent field campaigns at two sites in the Zambales ophiolite (Mangatarem and Bigbiga), samples of bentonite and the associated hyperalkaline groundwaters have been collected by drilling and trenching. At Mangatarem, qualitative data from a 'fossil' (i.e. no groundwater is currently present) reaction zone indicates some alteration of the bentonite to zeolite, serpentine and CSH phases. Preliminary reaction path modelling suggests that the

Mineralogy, composition and PGM of chromitites from Pefki, Pindos ophiolite complex (NW Greece): evidence for progressively elevated fAs conditions in the upper mantle sequence

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Kapsiotis, Argirios; Grammatikopoulos, Tassos A.; Tsikouras, Basilios; Hatzipanagiotou, Konstantin; Zaccarini, Federica; Garuti, Giorgio

2011-01-01

The Pindos ophiolite complex, located in the northwestern part of continental Greece, hosts various chromite deposits of both metallurgical (high-Cr) and refractory (high-Al) type. The Pefki chromitites are banded and sub-concordant to the surrounding serpentinized dunites. The Cr# [Cr/(Cr + Al)] of magnesiochromite varies between 0.75 and 0.79. The total PGE grade ranges from 105.9 up to 300.0 ppb. IPGE are higher than PPGE, typical of mantle hosted ophiolitic chromitites. The PGM assemblage in chromitites comprises anduoite, ruarsite, laurite, irarsite, sperrylite, hollingworthite, Os-Ru-Ir alloys including osmium and rutheniridosmine, Ru-bearing oxides, braggite, paolovite, platarsite, cooperite, vysotskite, and palladodymite. Iridarsenite and omeiite were also observed as exsolutions in other PGM. Rare electrum and native Ag are recovered in concentrates. This PGM assemblage is of great petrogenetic importance because it is significantly different from that commonly observed in podiform mantle-hosted and banded crustal-hosted ophiolitic chromitites. PGE chalcogenides of As and S are primary, and possibly crystallized directly from a progressively enriched in As boninitic melt before or during magnesiochromite precipitation. The presence of Ru-bearing oxides implies simultaneous desulfurization and dearsenication processes. Chemically zoned laurite and composite paolovite-electrum intergrowths are indicative of the relatively high mobility of certain PGE at low temperatures under locally oxidizing conditions. The PGM assemblage and chemistry, in conjunction with geological and petrologic data of the studied chromitites, indicate that it is characteristic of chromitites found within or close to the petrologic Moho. Furthermore, the strikingly different PGM assemblages between the high-Cr chromitites within the Pindos massif is suggestive of non-homogeneous group of ores.

The Juchatengo complex: an upper-level ophiolite assemblage of late Paleozoic age in Oaxaca, southern Mexico

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Grajales-Nishimura, José Manuel; Ramos-Arias, Mario Alfredo; Solari, Luigi; Murillo-Muñetón, Gustavo; Centeno-García, Elena; Schaaf, Peter; Torres-Vargas, Ricardo

2018-04-01

The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated by late Paleozoic magmatism. It consists of mafic and sedimentary rocks that have oceanic affinities, with internal pseudostratigraphic, structural and metamorphic characteristics, which resemble a typical upper-level ophiolite assemblage. New U-Pb zircon and previous hornblende K-Ar analyses yield ages of ca. 291-313 Ma (U-Pb) for plagiogranites and ca. 282-277 Ma for tonalites intruding the entire sequence, including pelagic sediments at the top, with a maximum deposition age of ca. 278 Ma and noteworthy local provenance. These data constrain the age of the JC to the Late Pennsylvanian-Early Permian period. Hf isotopic analyses obtained from zircons in the JC plagiogranite and tonalite show that they come from a similar primitive mantle source (176Hf/177Hf: 0.282539-0.283091; ƐHf(t): + 3.2 to + 15.0). ƐHf(t) values from near 0 to - 2.8 in the tonalites indicate a contribution from the continental crust. Trace elements and REE patterns in whole rock and zircons point to a primitive mantle source for differentiated mafic, plagiogranite dykes and tonalitic plutons. Geochronological and geochemical data address the generation of new oceanic crust above the subduction zone, probably in a backarc setting. In this tectonic scenario, the JC ophiolite originated due to the convergence of the paleo-Pacific plate below the already integrated Oaxacan and Acatlán complexes in western Pangea. The dextral displacement places the deformation in a transtensional regime during the late Paleozoic age.

An oceanic core complex (OCC) in the Albanian Dinarides? Preliminary paleomagnetic and structural results from the Mirdita Ophiolite (northern Albania)

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Maffione, M.; Morris, A.; Anderson, M.

2010-12-01

Oceanic core complexes (OCCs) are dome-shaped massifs commonly associated with the inside corners of the intersection of transform faults and slow (and ultra-slow) spreading centres. They represent the uplifted footwalls of large-slip oceanic detachment faults (e.g. Cann et al., 1997; Blackman et al., 1998) and are composed of mantle and lower crustal rocks exhumed during fault displacement (Smith et al., 2006, 2008). Recent paleomagnetic studies of core samples from OCCs in the Atlantic Ocean (Morris et al., 2009; MacLeod et al., in prep) have confirmed that footwall sections undergo substantial rotation around (sub-) horizontal axes. These studies, therefore, support “rolling hinge” models for the evolution of OCCs, whereby oceanic detachment faults initiate at a steep angle at depth and then “roll-over” to their present day low angle orientations during unroofing (Buck, 1988; Wernicke & Axen, 1988; Lavier et al., 1999). However, a fully integrated paleomagnetic and structural analysis of this process is hampered by the one-dimensional sampling provided by ocean drilling of OCC footwalls. Therefore, ancient analogues for OCCs in ophiolites are of great interest, as these potentially provide 3-D exposures of these important structures and hence a more complete understanding of footwall strain and kinematics (providing that emplacement-related phases of deformation can be accounted for). Recently, the relationship between outcropping crustal and upper mantle rocks led Tremblay et al. (2009) to propose that an OCC is preserved within the Mirdita ophiolite of the Albanian Dinarides (northern Albania). This is a slice of Jurassic oceanic lithosphere exposed along a N-S corridor which escaped the main late Cenozoic Alpine deformation (Robertson, 2002, 2004; Dilek et al., 2007). Though in the eastern portion of the Mirdita ophiolite a Penrose-type sequence is present, in the western portion mantle rocks are in tectonic contact with upper crustal lithologies

Geochemical bioenergetics during low-temperature serpentinization: An example from the Samail ophiolite, Sultanate of Oman

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Canovas, Peter A.; Hoehler, Tori; Shock, Everett L.

2017-07-01

Various classes of microbial and biomolecular evidence from global studies in marine and continental settings are used to identify a set of reactions that appear to support microbial metabolism during serpentinization of ultramafic rocks. Geochemical data from serpentinizing ecosystems in the Samail ophiolite of Oman are used to evaluate the extent of disequilibria that can support this set of microbial metabolisms and to provide a ranking of potential metabolic energy sources in hyperalkaline fluids that are direct products of serpentinization. Results are used to construct hypotheses for how microbial metabolism may be supported in the subsurface for two cases: ecosystems hosted in rocks that have already undergone significant serpentinization and those hosted by deeper, active serpentinization processes.

Sr isotopic tracer study of the Samail ophiolite, Oman

International Nuclear Information System (INIS)

Lanphere, M.A.; Coleman, R.G.; Hopson, C.A.

1981-01-01

We have measured Rb and Sr concentrations and Sr isotopic compositions in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite diabase dikes, and gabbro and websterite dikes within the metamorphic peridotite. Ten samples of cummulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have mean 87 Sr/ 86 Sr ratios and standard deviations of 0.70314 +- 0.00030 and 0.70306 +- 0.00034, respectively. The dispersion in Sr isotopic composition may reflect real heterogeneities in the magma source region. The average Sr isotopic composition of cumulate gabbro falls in the range of isotopic compositions of modern midocean ridge basalt. The 87 Sr/ 86 Sr ratios of noncumulate gabbro, plagiogranite, and diabase dikes range from 0.7034 to 0.7047, 0.7038 to 0.7046, and 0.7037 to 0.7061, respectively. These higher 87 Sr/ 86 Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with seawater. Mineral separates from dikes that cut harzburgite tectonite have Sr isotopic compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dikes were derived from partial melting of source regions that had similar long-term histories and chemical compositions

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

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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.

Isotopic and trace element constraints on the genesis of a boninitic sequence in the Thetford Mines ophiolitic complex, Quebec, Canada

International Nuclear Information System (INIS)

Olive, V.; Hebert, R.; Loubet, M.

1997-01-01

The Mont Ham Massif (part of the Thetford Mines ophiolite, south Quebec) represents a magmatic sequence made up of tholeiitic and boninitic derived products. A geochemical study confirms the multicomponent mixing models that have been classically advanced for the source of boninites, with slab-derived components added to the main refractory harzburgitic peridotite. An isochron diagram of the boninitic rocks is interpreted as a mixing trend between two components: (i) a light rare earth element (LREE) enriched component (A), interpreted as slab-derived fluid-melts equilibrated with sedimentary materials (ε Nd = -3, 147 Sm/ 144 Nd = 0.140), and (ii) a LREE-depleted component (B) (0.21 147 Sm/ 144 Nd Nd = 9). A multicomponent source is also necessary to explain the Nd-isotope and trace element composition of the tholeiites, which are explained by the melting of a more fertile, Iherzolitic mantle and (or) mid-ocean ridge basalt source (component C), characterized by a large-ion lithophile element depicted pattern and an lapetus mantle Nd isotopic composition (ε Nd = 9), mixed in adequate proportions with the two previously infered slab-derived components (A and B). The genesis of the boninites of Mont Ham is not significantly different from those of boninites located in the Pacific. An intraoceanic subduction zone appears to be an appropriate geodynamic environment for the Mont Ham ophiolitic sequence. (author)

Listwaenite in the Sartohay ophiolitic mélange (Xinjiang, China): A genetic model based on petrology, U-Pb chronology and trace element geochemistry

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Qiu, Tian; Zhu, Yongfeng

2018-03-01

Listwaenite lenses in the Sartohay ophiolitic mélange (Xinjiang, China) were formed via reactions between serpentinite and metasomatic fluids. First, serpentinite changed into talc schist via the reaction of serpentine + CO2 → talc + magnesite + H2O. Second, talc schist changed into listwaenite via the reaction of talc + CO2 → magnesite + quartz + H2O. Magnetite was progressively destroyed during transformation from serpentinite to talc schist, and completely consumed in listwaenite. Zircon crystals 30-100 μm long, disseminating in talc schist, undeformed listwaenite and mylonitized listwaenite, coexist with talc, quartz and magnesite, while micron-sized zircon grains (ages (302.9 ± 6.8 Ma, 299.7 ± 5.5 Ma and 296.5 ± 3.5 Ma), and are thought to represent the age of formation of the talc schist and listwaenite. These ages are indistinguishable within errors and suggest a rapid transformation from talc schist to listwaenite. Some zircon rims in samples of the undeformed listwaenite and mylonitized listwaenite give much younger apparent U-Pb ages (280-277 Ma), which could be interpreted as a recrystallization age reflecting late-stage shearing in the Sartohay ophiolitic mélange.

Mineralogical assemblages forming at hyperalkaline warm springs hosted on ultramafic rocks: A case study of Oman and Ligurian ophiolites

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Chavagnac, Valérie; Ceuleneer, Georges; Monnin, Christophe; Lansac, Benjamin; Hoareau, Guilhem; Boulart, Cédric

2013-07-01

We report on the mineralogical assemblages found in the hyperalkaline springs hosted on Liguria and Oman ophiolites based on exhaustive X-ray diffraction and scanning electron microprobe analyses. In Liguria, hyperalkaline springs produce a thin brownish calcite precipitate that covers the bedrock due to the concomitant atmospheric CO2 uptake and neutralization of the hyperalkaline waters. No brucite and portlandite minerals are observed. The discharge of alkaline waters in Oman ophiolite forms white-orange precipitates. Calcium carbonate minerals (calcite and/or aragonite) are the most abundant and ubiquitous precipitates and are produced by the same mechanism as in Liguria. This process is observed as a thin surface crust made of rhombohedral calcite. Morphological features of aragonite vary from needle-, bouquet-, dumbbell-, spheroidal-like habitus according to the origin of carbon, temperature, and ionic composition of the hyperalkaline springs, and the biochemical and organic compounds. Brucite is observed both at hyperalkaline springs located at the thrust plane and at the paleo-Moho. The varying mixing proportions between the surface runoff waters and the hyperalkaline ones control brucite precipitation. The layered double hydroxide minerals occur solely in the vicinity of hyperalkaline springs emerging within the bedded gabbros. Finally, the dominant mineralogical associations we found in Oman (Ca-bearing carbonates and brucite) in a serpentinizing environment driven by the meteoric waters are surprisingly the same as those observed at the Lost City hydrothermal site in a totally marine environment.

PALLADIUM, PLATINUM, RHODIUM, RUTHENIUM AND IRIDIUM IN PERIDOTITES AND CHROMITITES FROM OPHIOLITE COMPLEXES IN NEWFOUNDLAND.

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Page, Norman J; Talkington, Raymond W.

1984-01-01

Samples of spinel lherzolite, harzburgite, dunite, and chromitite from the Bay of Islands, Lewis Hills, Table Mountain, Advocate, North Arm Mountain, White Hills Periodite Point Rousse, Great Bend and Betts Cove ophiolite complexes in Newfoundland were analyzed for the platinum-group elements (PGE) Pd, Pt, Rh, Ru and Ir. The ranges of concentration (in ppb) observed for all rocks are: less than 0. 5 to 77 (Pd), less than 1 to 120 (Pt), less than 0. 5 to 20 (Rh), less than 100 to 250 (Ru) and less than 20 to 83 (Ir). Chondrite-normalized PGE ratios suggest differences between rock types and between complexes. Samples of chromitite and dunite show relative enrichment in Ru and Ir and relative depletion in Pt and Pd.

Metaultramafic schists and dismembered ophiolites of the Ashe Metamorphic Suite of northwestern North Carolina, USA

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Raymond, Loren A.; Merschat, Arthur J.; Vance, R. Kelly

2016-01-01

both chemical composition and metamorphic history. Spot sampling of heterolithic MUR bodies does not reveal MUR body character or history or allow ‘type’ designations. We recommend that the subdivision of MUR bodies into ‘types’ be abandoned and that the metasomatic hypothesis be carefully applied. AMS MURs and associated metamafic rocks likely represent fragments of dismembered ophiolites from various ophiolite types.

Metabolic Potential and Activity in Fluids of the Coast Range Ophiolite Microbial Observatory, California, USA

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Hoehler, T.; Som, S.; Schrenk, M.; McCollom, T.; Cardace, D.

2016-01-01

Metabolic potential and activity associated with hydrogen and carbon monoxide were characterized in fluids sampled from the the Coast Range Ophiolite Microbial Observatory (CROMO). CROMO consists of two clusters of science-dedicated wells drilled to varying depths up to 35m in the actively serpentinizing, Jurassic-age Coast Range Ophiolite of Northern California, along with a suite of pre-existing monitoring wells at the same site. Consistent with the fluid chemistry observed in other serpentinizing systems, CROMO fluids are highly alkaline, with pH up to 12.5, high in methane, with concentrations up 1600 micromolar, and low in dissolved inorganic carbon (DIC), with concentrations of 10's to 100's of micromolar. CROMO is conspicuous for fluid H2 concentrations that are consistently sub-micromolar, orders of magnitude lower than is typical of other systems. However, higher H2 concentrations (10's -100's of micromolar) at an earlier stage of fluid chemical evolution are predicted by, or consistent with: thermodynamic models for fluid chemistry based on parent rock composition equivalent to local peridotite and with water:rock ratio constrained by observed pH; the presence of magnetite at several wt% in CROMO drill cores; and concentrations of formate and carbon monoxide that would require elevated H2 if formed in equilibrium with H2 and DIC. Calculated Gibbs energy changes for reaction of H2 and CO in each of several metabolisms, across the range of fluid composition encompassed by the CROMO wells, range from bioenergetically feasible (capable of driving ATP synthesis) to thermodynamically unfavorable. Active consumption relative to killed controls was observed for both CO and H2 during incubation of fluids from the pre-existing monitoring wells; in incubations of freshly cored solids, consumption was only observed in one sample set (corresponding to the lowest pH) out of three. The specific metabolisms by which H2 and CO are consumed remain to be determined.

Accreted seamounts in North Tianshan, NW China: Implications for the evolution of the Central Asian Orogenic Belt

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Yang, Gaoxue; Li, Yongjun; Kerr, Andrew C.; Tong, Lili

2018-03-01

The Carboniferous Bayingou ophiolitic mélange is exposed in the North Tianshan accretionary complex in the southwestern part of the Central Asian Orogenic Belt (CAOB). The mélange is mainly composed of serpentinised ultramafic rocks (including harzburgite, lherzolite, pyroxenite, dunite and peridotite), pillowed and massive basalts, layered gabbros, radiolarian cherts, pelagic limestones, breccias and tuffs, and displays block-in-matrix structures. The blocks of ultramafic rocks, gabbros, basalts, cherts, and limestones are set in a matrix of serpentinised ultramafic rocks, massive basalts and tuffs. The basaltic rocks in the mélange show significant geochemical heterogeneity, and two compositional groups, one ocean island basalt-like, and the other mid-ocean ridge-like, can be distinguished on the basis of their isotopic compositions and immobile trace element contents (such as light rare earth element enrichment in the former, but depletion in the latter). The more-enriched basaltic rocks are interpreted as remnants/fragments of seamounts, derived from a deep mantle reservoir with low degrees (2-3%) of garnet lherzolite mantle melting. The depleted basalts most likely formed by melting of a shallower spinel lherzolite mantle source with ∼15% partial melting. It is probable that both groups owe their origin to melting of a mixture between plume and depleted MORB mantle. The results from this study, when integrated with previous work, indicate that the Junggar Ocean crust (comprising a significant number of seamounts) was likely to have been subducted southward beneath the Yili-Central Tianshan block in the Late Devonian-Early Carboniferous. The seamounts were scraped-off and accreted along with the oceanic crust in an accretionary wedge to form the Bayingou ophiolitic mélange. We present a model for the tectonomagmatic evolution of this portion of the CAOB involving prolonged intra-oceanic subduction with seamount accretion.

PGE mineralization and melt composition of chromitites in Proterozoic ophiolite complexes of Eastern Sayan, Southern Siberia

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O. Kiseleva

2017-07-01

Full Text Available The Ospino-Kitoi and Kharanur ultrabasic massifs represent the northern and southern ophiolite branches respectively of the Upper Onot ophiolitic nappe and they are located in the southeastern part of the Eastern Sayan (SEPES ophiolites. Podiform chromitites with PGE mineralization occur as lensoid pods within dunites and rarely in harzburgites or serpentinized peridotites. The chromitites are classified into type I and type II based on their Cr#. Type I (Cr# = 59–85 occurs in both northern and southern branches, whereas type II (Cr# = 76–90 occurs only in the northern branch. PGE contents range from ∑PGE 88–1189 ppb, Pt/Ir 0.04–0.42 to ∑PGE 250–1700 ppb, Pt/Ir 0.03–0.25 for type I chromitites of the northern and southern branches respectively. The type II chromitites of the northern branch have ∑PGE contents higher than that of type I (468–8617 ppb, Pt/Ir 0.1–0.33. Parental melt compositions, in equilibrium with podiform chromitites, are in the range of boninitic melts and vary in Al2O3, TiO2 and FeO/MgO contents from those of type I and type II chromitites. Calculated melt compositions for type I chromitites are (Al2O3melt = 10.6–13.5 wt.%, (TiO2melt = 0.01–0.44 wt.%, (Fe/Mgmelt = 0.42–1.81; those for type II chromitites are: (Al2O3melt = 7.8–10.5 wt.%, (TiO2melt = 0.01–0.25 wt.%, (Fe/Mgmelt = 0.5–2.4. Chromitites are further divided into Os-Ir-Ru (I and Pt-Pd (II based on their PGE patterns. The type I chromitites show only the Os-Ir-Ru pattern whereas type II shows both Os-Ir-Ru and Pt-Pd patterns. PGE mineralization in type I chromitites is represented by the Os-Ir-Ru system, whereas in type II it is represented by the Os-Ir-Ru-Rh-Pt system. These results indicate that chromitites and PGE mineralization in the northern branch formed in a suprasubduction setting from a fluid-rich boninitic melt during active subduction. However, the chromitites and PGE mineralization of the southern

Petro-structural, geochemical and carbon and oxygen isotopic study on carbonates crosscuting the Oman Ophiolite peridotites: evidence of polygenic CO2 trapping

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Noël, J.; Godard, M.; Martinez, I.; Oliot, E.; Williams, M. J.; Rodriguez, O.; Chaduteau, C.; Gouze, P.

2017-12-01

Carbon trapping in ophiolitic peridotites contributes to the global carbon cycle between solid Earth and its outer envelopes (through subduction and/or modern alteration). To investigate this process, we performed petro-structural (microtomography, EBSD, EPMA) and geochemical studies (LA-ICP-MS, carbon and oxygen isotopes on bulk and minerals using SHRIMP) of harzburgites cored in the Oman Ophiolite. Studied harzburgites are highly serpentinized (> 90 %) and crosscut by 3 generations of carbonates (> 20 Vol%) with compositions from calcite to dolomite (Mg/Ca = 0-0.85). Type 1 carbonates are fine penetrative veinlets and mesh core after olivine. They have low REE (e.g., Yb = 0.08-0.23 x CI-chondrite) and negative Ce anomalies. They have δ13CPDB = -15.2 to 1.10‰ and δ18OSMOW = 17.5 to 33.7‰, suggesting precipitation temperatures up to 110°C. Type 2 carbonates are pluri-mm veins bounded by cm-thick serpentinized vein selvages, oriented dominantly parallel to mantle foliation. Dynamic recrystallization is observed, indicating polygenetic formation: well crystallized calcite with REE abundances similar to Type 1 carbonates are locally replaced by small dolomite and calcite grains with higher REE (e.g., Yb = 0.35-1.0 x CI-chondrite) and positive Gd anomaly. Type 2 carbonates have δ13CPDB = -12.6 to -4.1‰ and δ18OSMOW = 25.0 to 32.7‰, suggesting precipitation temperatures from 10 to 60°C. Type 3 carbonates are late pluri-mm to cm veins reactivating Type 2 veins. They consist of small grains of dolomite and calcite with REE abundances similar to recrystallized Type 2 carbonates. Type 3 carbonates have δ13CPDB = -8.3 to -5.8‰ and δ18OSMOW = 28.8 to 32.7‰, suggesting precipitation temperatures 100°C). Formation of carbonate veins (Type 2) indicates localization of fluid flux, while serpentinization remains the dominant alteration process. Low T carbonate veins (Type 3) remain the main flow path through ophiolitic peridotites. Our study suggests that

Petrology and geochemistry of the high-Cr podiform chromitites of the Köycegiz ophiolite, southwest Turkey: implications for the multi-stage evolution of the oceanic upper mantle

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Xiong, Fahui; Yang, Jingsui; Dilek, Yildirim; Wang, ChunLian; Hao, Xiaolin; Xu, Xiangzhen; Lian, Dongyang

2018-03-01

Ophiolites exposed across the western Tauride belt in Turkey represent tectonically emplaced fragments of oceanic lithosphere obducted onto the continental margin following the closure of the Neotethys Ocean during the Late Cretaceous. The ultramafic massif of Köycegiz, which is located in the ophiolitic belt of southwestern Turkey, is a major source of metallurgical chromitite ore. The massif comprises a base of tectonized harzburgite with minor dunite overlain by a magmatic sequence of wehrlite, pyroxenite, troctolite and gabbro. Only sparse refractory chromitites occur within the harzburgites; in contrast, the upper and middle sections of the peridotite sequence contain abundant metallurgical chromitites. The peridotites record abundant evidence of mantle metasomatism on various scales, as the Fo values of olivine in harzburgite are 90.1-95.4, whereas those in dunite are 90.1-91.8. The compositions of the melts passing through the peridotites changed gradually from arc tholeiite to boninite due to melt-rock reactions, thus producing more Cr-rich chromitites in the upper part of the body. Most of the chromitites have high Cr numbers (77-78), although systematic changes in the compositions of the olivine and chromian spinel occur from the harzburgites to the dunite envelopes to the chromitites, reflecting melt-rock reactions. The calculated ΔlogfO2 (FMQ) values range from - 2.77 to + 1.03 in the chromitites, - 2.73 to -0.01 in the harzburgites, and - 1.65 to + 0.45 in the dunites. All of the available evidence suggests that the Köycegiz ophiolite formed in a supra-subduction zone (SSZ) mantle wedge. These models indicate that the harzburgites represent the products of first-stage melting and low degrees of melt-rock interaction that occurred in a mid-ocean ridge (MOR) environment. In contrast, the chromitites and dunites represent the products of second-stage melting and related refertilization, which occurred in an SSZ environment.

Unraveling P-T-t-D Evolution of Zermatt-Saas Ophiolites from Valtournanche: from Ocean Opening to Mountain Building

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Rebay, G.; Tiepolo, M.; Zanoni, D.; Langone, A.; Spalla, M. I.

2015-12-01

The Zermatt-Saas (ZS) Zone, formerly part of Tethyan oceanic crust and variously affected by oceanic metamorphism, is now part of the orogenic suture that developed in the Western European Alps during the Alpine subduction and collision. The ZS rocks preserve a dominant HP to UHP metamorphic imprint overprinted by greenschist facies metamorphism. The age of the oceanic protoliths is considered to be middle to upper Jurassic whereas the HP metamorphism is mostly considered to be Eocene. In upper Valtournanche ZS ophiolites, the dominant regional S2 foliation is mapped with spatial continuity in serpentinite, metarodingite and eclogite and is defined by HP/UHP parageneses in all lithotypes. It developed at 2.5 ± 0.3 GPa and 600 ± 20°C during Alpine subduction. S2 foliation of serpentinites wraps rare clinopyroxene and zircon relics. Trace element composition of clinopyroxene suggests that they crystallised from a melt in equilibrium with plagioclase: they most likely represent relicts of gabbroic assemblages. The clinopyroxene porphyroclasts have rims indented within S2 and compositions similar to fine-grained clinopyroxeneII defining S2, suggesting that they recrystallised during Alpine subduction. Zircon cores show, under CL, sector zoning typical of magmatic growth. U-Pb dates suggest their crystallisation during Middle Jurassic. Magmatic cores have thin fringe overgrowths parallel to the S2 foliation. U-Pb concordant analyses on these domains reveal an Upper Cretaceous-Paleocene crystallization most likely representing the HP to UHP Alpine re-equilibration. This suggests that some sections of the ZS have experienced HP to UHP metamorphism earlier than previously thought, opening new interpretative geodynamic scenarios. Remarkably, these new dates are similar to those recorded for the HP re-equilibration in the continental crust of the adjacent Austroalpine units (upper plate of the Alpine subduction system) and to those recorded for prograde metamorphism in

Making a report of a short trip in an ophiolitic complex with Google Earth

Science.gov (United States)

Aubret, Marianne

2017-04-01

Plate tectonics is taught in French secondary school (lower and upper-sixth). According to the curriculum, the comprehension of plate-tectonic processes and concepts should be based on field data. For example, the Alpine's ocean history is studied to understand how mountain ranges are formed. In this context, Corsica is a great open-air laboratory, but unfortunately, the traffic conditions are very difficult in the island and despite the short distances, it's almost impossible for teachers to take their students to the remarkable geologic spots. The «défilé de l'Inzecca» is one of them: there you can see a part of the alpine's ophiolitic complex. The aim of this activity is to elaborate a « KMZ folder » in Google Earth as a report of a short trip thanks to the students' data field; it is also the occasion to enrich the Google Earth KMZ folder already available for our teaching.

Iron transformations during low temperature alteration of variably serpentinized rocks from the Samail ophiolite, Oman

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Mayhew, Lisa E.; Ellison, Eric T.; Miller, Hannah M.; Kelemen, Peter B.; Templeton, Alexis S.

2018-02-01

Partially serpentinized peridotites in the Samail ophiolite in the Sultanate of Oman currently undergo low temperature alteration and hydration both at shallow levels, with water recently in contact with the atmosphere, and at depth, with anoxic, reducing fluids. However, it is unclear how changes in the distribution and oxidation state of Fe are driving the production of energy-rich gases such as hydrogen and methane detected in peridotite catchments. We track the Fe transformations in a suite of outcrop samples representing a subset of the spectrum of least to most altered end-members of the Oman peridotites. We use microscale mineralogical and geochemical analyses including QEMSCAN, Raman spectroscopy, synchrotron radiation X-ray fluorescence (XRF) mapping, and electron microprobe wavelength dispersive spectroscopy. The less-altered peridotites possess a diversity of Fe-bearing phases including relict primary minerals (e.g. olivine, pyroxene, chromite) and secondary phases (e.g. serpentine and brucite). Raman spectroscopy and electron microprobe data (Si/(Mg + Fe)) indicate that much of the serpentine is significantly intergrown with brucite on the sub-micron scale. These data also indicate that the Fe content of the brucite ranges from 10 to 20 wt% FeO. The mineral assemblage of the highly reacted rocks is less diverse, dominated by serpentine and carbonate while olivine and brucite are absent. Magnetite is relatively rare and mainly associated with chromite. Goethite and hematite, both Fe(III)-hydroxides, were also identified in the highly altered rocks. Whole rock chemical analyses reflect these mineralogical differences and show that Fe in the partially serpentinized samples is on average more reduced (∼0.40-0.55 Fe3+/FeTotal) than Fe in the highly reacted rocks (∼0.85-0.90 Fe3+/FeTotal). We propose that olivine, brucite, chromite and, perhaps, serpentine in the less-altered peridotites act as reactive phases during low temperature alteration of the Oman

Crystallization Temperatures of Lower Crustal Gabbros from the Oman Ophiolite and the Persistence of the 'Mush Zone' at Intermediate/Fast Spreading Ridges

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VanTongeren, J. A.

2017-12-01

Oceanic crust is formed when mantle-derived magmas are emplaced at the ridge axis, a zone of intense rifting and extension. Magmas begin to cool and crystallize on-axis, forming what is termed the "Mush Zone", a region of partially molten rocks. Several attempts have been made to understand the nature of the Mush Zone at fast spreading mid-ocean ridges, specifically how much partial melt exists and how far off-axis the Mush Zone extends. Geophysical estimates of P-wave velocity perturbations at the East Pacific Rise show a region of low velocity approximately 1.5-2.5 km off-axis, which can be interpreted to be the result of higher temperature [e.g. Dunn et al., 2000, JGR] or the existence of partial melt. New petrological and geochemical data and methods allow for the calculation of the lateral extent of the Mush Zone in the lower oceanic crust on exposed sections collected from the Oman ophiolite, a paleo-fast/intermediate spreading center. I will present new data quantifying the crystallization temperatures of gabbros from the Wadi Khafifah section of lower oceanic gabbros from the Oman ophiolite. Crystallization temperatures are calculated with the newly developed plagioclase-pyroxene REE thermometer of Sun and Liang [2017, Contrib. Min. Pet.]. There does not appear to be any systematic change in the crystallization temperature of lower crustal gabbros with depth in the crust. In order to quantify the duration of crystallization and the lateral extent of the Mush Zone of the lower crust, crystallization temperatures are paired with estimates of the solidus temperature and cooling rate determined from the same sample, previously constrained by the Ca diffusion in olivine geothermometer/ geospeedometer [e.g. VanTongeren et al., 2008 EPSL]. There is no systematic variation in the closure temperature of Ca in olivine, or the cooling rate to the 800°C isotherm. These results show that gabbros throughout the lower crust of the Oman ophiolite remain in a partially

Mineral chemistry and geothemobarometry of mantle harzburgites in the Eastern Metamorphic Complex of Khoy ophiolite -NW Iran

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Morovvat Faridazad

2017-02-01

Full Text Available Introduction Khoy ophiolite at the global scale is in the middle part of the Alp-Himalaya orogenic belt and it is extended over 3900 Km2 which indicates remnant Neotethys oceanic lithosphere in the Mesozoic era (Kananian et al., 2010. In this paper, in addition to a review of previous investigations about Khoy ophiolite, we will try to determine the nature and kind of minerals, origin and partial melting rate as well as the equilibrium pressure and temperature of harzburgites from the Eastern Metamorphic Complex of Khoy ophiolite. Materials and methods Thin sections microscopy studies were carried out following field investigations. EPMA analysis was carried out with using a Superprobe JEOL, JXA 8200 Microprobe unit at the state of WDS and under condition of 15kv accelerating voltage, 10nA current beam, 1µm beam diameter and collection of natural and synthetic standards for calibration. Results The study area is located at the NW of Iran and north of the Khoy city in the west Azarbaijan province. This area is part of the ophiolitic complex of NW Iran and belongs to its Eastern Metamorphic Complex. This metamorphic zone has large tectonically segments of the metamorphic ophiolites which mainly include serpentinized peridotites with associated metagabbros. There are three types of peridotitic rocks in this area which are: Lherzolites, harzburgites and dunites. Lherzolites are composed of olivine (60-70%, orthopyroxene (10-30% and clinopyroxene (~10-20% with minor amounts (~2% of Cr-spinel mineral. Harzburgites are composed of olivine (70-80%, orthopyroxene (10-20% and clinopyroxene (~5% with minor amounts (~2% of Cr-spinel mineral. Dunites are composed of olivine (90-95%, orthopyroxene (5-10% with minor amounts (~1-2% of Cr-spinel mineral. Composition range of olivines is between Fo89.46 Fa10.37 to Fo89.86 Fa10.0 as well as NiO content range is 018-046 (wt %. The calculated Mg# of olivines is 0.90 and the composition of olivines in Fo-Fa diagram

Sulphide mineralization and wall-rock alteration in ophiolites and modern oceanic spreading centres

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Koski, R.A.

1983-01-01

Massive and stockwork Fe-Cu-Zn (Cyprus type) sulphide deposits in the upper parts of ophiolite complexes represent hydrothermal mineralization at ancient accretionary plate boundaries. These deposits are probable metallogenic analogues of the polymetallic sulphide deposits recently discovered along modern oceanic spreading centres. Genetic models for these deposits suggest that mineralization results from large-scale circulation of sea-water through basaltic basement along the tectonically active axis of spreading, a zone of high heat flow. The high geothermal gradient above 1 to 2 km deep magma chambers emplaced below the ridge axis drives the convective circulation cell. Cold oxidizing sea-water penetrating the crust on the ridge flanks becomes heated and evolves into a highly reduced somewhat acidic hydrothermal solvent during interaction with basaltic wall-rock. Depending on the temperature and water/rock ratio, this fluid is capable of leaching and transporting iron, manganese, and base metals; dissolved sea-water sulphate is reduced to sulphide. At the ridge axis, the buoyant hydrothermal fluid rises through permeable wall-rocks, and fluid flow may be focussed along deep-seated fractures related to extensional tectonic processes. Metal sulphides are precipitated along channelways as the ascending fluid undergoes adiabatic expansion and then further cooling during mixing with ambient sub-sea-floor water. Vigorous fluid flow results in venting of reduced fluid at the sea-floor/sea-water interface and deposition of massive sulphide. A comparison of sulphide mineralization and wall-rock alteration in ancient and modern spreading centre environments supports this genetic concept. Massive sulphide deposits in ophiolites generally occur in clusters of closely spaced (stacked sequences of pillow basalt and sheet flows, the sea-floor underlying numerous deposits in Guaymas Basin consists of diatomaceous ooze and terrigenous clastic sediment that is intruded by diabase

Tholeitic basalts and ophiolitic complexes of the Mesorif Zone (External Rif, Morocco) at the Jurassic-Cretaceous boundary and the importance of the Ouerrha Accident in the palaeogeographic and geodynamic evolution of the Rif Mountains

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Benzaggagh, M.

2016-10-01

The stratigraphical series around the Jurassic-Cretaceous boundary of the External Rif Mountains, in particular those in the Mesorif Zone, exhibits many outcrops with volcanic materials spread westwards over 200 km. These materials show diverse aspects: basalt lithoclasts reworked into calcareous breccia beds or in marly matrix breccia, interstratified lava flows and volcanoclastic complexes incorporated within the Berriasian marls. In the Central Rif, several magmatic blocks outcrop, usually regarded as granite scales from the Paleozoic basement or as intrusive gabbros of Barremian age. Actually these magmatic massifs display typical ophiolitic sequences and they are overlaid by mega-olistoliths of Jurassic materials and locally by radiolarite layers. Geochemical analysis of several basalt and gabbro samples belonging to the Mesorif Zone evidenced that both display a typical E-MORB magma indicating at least partial oceanization of the Mesorif basement. Concerning geodynamics, the Mesorif Zone had undergone, at the Jurassic-Cretaceous boundary interval, two successive palaeogeographic phases: an uplift, close to emersion during the Kimmeridgian-Early Tithonian interval, stressed by important submarine volcanic activities and intense brecciation of the carbonate formations, followed by a general collapse at the Late Tithonian, underlined by lava flows, slumping as mega-olistoliths and the formation of an oceanic crust, at least in the Central Rif. These magmatic materials, distributed on both sides of the Ouerrha Valley, evidence that this westwards extending valley (the Nekor Accident), may correspond in the Central Rif, to two palaeo-subduction planes which become two major overlapping thrusts in the western part of the Rif Mountains. (Author)

The Behaviour of Fe Stable Isotopes Accompanying Fluid Migration in Subducted Serpentinite from the Zermatt-Saas Ophiolite of the Swiss Alps

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Inglis, E.; Bouilhol, P.; Burton, K. W.; Debret, B.; Millet, M. A.; Williams, H. M.

2016-12-01

During subduction the destabilisation of hydrous serpentine group phases can generate significant fluid fluxes between the subducting slab and the overlying mantle wedge. Despite our knowledge of this, the exact process and nature of the fluids released during serpentinite devolatilisation remain poorly understood. This study presents new field observations alongside petrographic and geochemical data for metamorphic veins and host serpentinite from the Zermatt-Saas ophiolite from the Swiss Alps, which underwent high-pressure metamorphism during the Alpine orogeny. Samples were collected from the serpentinised ultramafic section of the Zermatt-Saas ophiolite, which is mainly comprised of variably foliated and sheared antigorite serpentine. High-pressure metamorphic veins hosted within the antigorite serpentinite, are observed within the least deformed part of the massif, occurring as cm scale laterally continuous channels or mm scale interconnected anastomosing networks. Preliminary high-precision Fe isotope data for the host antigorite serpentine yield a mean δ56Fe value of -0.09‰ ± 0.04‰ (n=3), notably lighter than previously measured Alpine and abyssal serpentinites (Debret et al., 2016). In contrast, samples of cm scale olivine-bearing veins display a mean δ56Fe value of 0.07 ± 0.05‰ (n=3), resolvably heavier than that of the host serpentinite. These preliminary results suggest preferential mobility of isotopically heavy Fe within the vein forming fluids, but at this stage it is unclear if this fluid is related to local devolatilisation of the host serpentinite or input from an external source. Debret et al., 2016. Isotopic evidence for iron mobility during subduction. Geology, v. 44, no. 3, pp. 215 -218.

Paleomagnetism of Jurassic radiolarian chert above the Coast Range ophiolite at Stanley Mountain, California, and implications for its paleogeographic origins

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Hagstrum, J.T.; Murchey, B.L.

1996-01-01

Upper Jurassic red tuffaceous chert above the Coast Range ophiolite at Stanley Mountain, California (lat 35??N, long 240??E), contains three components of remanent magnetization. The first component (A; removed by ???100-???200 ??C) has a direction near the present-day field for southern California and is probably a recently acquired thermoviscous magnetization. A second component (B; removed between ???100 and ???600 ??C) is identical to that observed by previous workers in samples of underlying pillow basalt and overlying terrigenous sedimentary rocks. This component has constant normal polarity and direction throughout the entire section, although these rocks were deposited during a mixed polarity interval of the geomagnetic field. The B magnetization, therefore, is inferred to be a secondary magnetization acquired during accretion, uplift, or Miocene volcanism prior to regional clockwise rotation. The highest temperature component (C; removed between ???480 and 680 ??C) is of dual polarity and is tentatively interpreted as a primary magnetization, although it fails a reversal test possibly due to contamination by B. Separation of the B and C components is best shown by samples with negative-inclination C directions, and a corrected mean direction using only these samples indicates an initial paleolatitude of 32??N ?? 8??. Paleobiogeographic models relating radiolarian faunal distribution patterns to paleolatitude have apparently been incorrectly calibrated using the overprint B component. Few other paleomagnetic data have been incorporated in these models, and faunal distribution patterns are poorly known and mostly unqualified. The available data, therefore, do not support formation of the Coast Range ophiolite at Stanley Mountain near the paleoequator or accretion at ???10??N paleolatitude, as has been previously suggested based on paleomagnetic data, but indicate deposition near expected paleolatitudes for North America (35??N ?? 4??) during Late Jurassic

Geology of gemstone deposit Ugljarevats (Central Serbia) and contributions to genetic model

International Nuclear Information System (INIS)

Kureshevicj, Lidija; Vushovicj, Olivera; Delicj-Nikolicj, Ivana

2017-01-01

Silica gemstone deposit Ugljarevats is situated within the ophiolite sequence of the Vardar zone central deep fault. Genetic processes of this deposit are connected to the Neogene calc-alkaline magmatic activity of the Vardar zone and hydrothermal activity triggered by it. Based on surface occurrences of listwenitized serpentinite containing silica mineralization, it can be inferred that the ore body is an elongated oval stock. Within the stock of hydrothermally altered serpentinite, the gemstone mineralization occurs as veins, stock works and irregular bodies. Present gemstone types include chalcedony varieties (jasper, colourless and greenish chalcedony, carnelian and sard) and opal (opalized serpentinite). Homogenous pieces are very rare. Most often, various types of silica are intimately intermixed and combined. The mineralization has formed in two distinct hydrothermal phases, apparently in close time succession. Jasper and coloured chalcedony (and rare magnesite) are the products of the first phase of hydro- thermal activity, while the colourless chalcedony is formed in the second phase. Newly discovered type of silica vein with central-symmetrical parallel banding gives new contributions to a genetic model, proving the precipitation process and its products are unpredictably changeable, heterogeneous and depending on the evolution of the local environment physico-chemical conditions, notably the contents of impurities and system's openness degree. (author)

Late Precambrian Balkan-Carpathian ophiolite — a slice of the Pan-African ocean crust?: geochemical and tectonic insights from the Tcherni Vrah and Deli Jovan massifs, Bulgaria and Serbia

Science.gov (United States)

Savov, Ivan; Ryan, Jeff; Haydoutov, Ivan; Schijf, Johan

2001-10-01

The Balkan-Carpathian ophiolite (BCO), which outcrops in Bulgaria, Serbia and Romania, is a Late Precambrian (563 Ma) mafic/ultramafic complex unique in that it has not been strongly deformed or metamorphosed, as have most other basement sequences in Alpine Europe. Samples collected for study from the Tcherni Vrah and Deli Jovan segments of BCO include cumulate dunites, troctolites, wehrlites and plagioclase wehrlites; olivine and amphibole-bearing gabbros; anorthosites; diabases and microgabbros; and basalts representing massive flows, dikes, and pillow lavas, as well as hyaloclastites and umbers (preserved sedimentary cover). Relict Ol, Cpx and Hbl in cumulate peridotites indicate original orthocumulate textures. Plagioclase in troctolites and anorthosites range from An60 to An70. Cumulate gabbro textures range from ophitic to poikilitic, with an inferred crystallization order of Ol-(Plag+Cpx)-Hbl. The extrusive rocks exhibit poikilitic, ophitic and intersertal textures, with Cpx and/or Plag (Oligoclase-Andesine) phenocrysts. The major opaques are Ti-Magnetite and Ilmenite. The metamorphic paragenesis in the mafic samples is Chl-Trem-Ep, whereas the ultramafic rocks show variable degrees of serpentinization, with lizardite and antigorite as dominant phases. Our samples are compositionally and geochemically similar to modern oceanic crust. Major element, trace element and rare earth element (REE) signatures in BCO basalts are comparable to those of MORB. In terms of basalt and dike composition, the BCO is a 'high-Ti' or 'oceanic' ophiolite, based on the classification scheme of Serri [Earth Planet. Sci. Lett. 52 (1981) 203]. Our petrologic and geochemical results, combined with the tectonic position of the BCO massifs (overlain by and in contact with Late Cambrian island arc and back-arc sequences), suggest that the BCO may have formed in a mid-ocean ridge setting. If the BCO records the existence of a Precambrian ocean basin, then there may be a relationship

Lower crustal section of the Oman Ophiolite drilled in Hole GT1A, ICDP Oman Drilling Project

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Umino, S.; Kelemen, P. B.; Matter, J. M.; Coggon, J. A.; Takazawa, E.; Michibayashi, K.; Teagle, D. A. H.

2017-12-01

Hole GT1A (22° 53.535'N, 58° 30.904'E) was drilled by the Oman Drilling Project (OmDP) into GT1A of the Samail ophiolite, Oman. OmDP is an international collaboration supported by the International Continental Scientific Drilling Program, the Deep Carbon Observatory, NSF, IODP, JAMSTEC, and the European, Japanese, German and Swiss Science Foundations, with in-kind support in Oman from the Ministry of Regional Municipalities and Water Resources, Public Authority of Mining, Sultan Qaboos University, and the German University of Technology. Hole GT1A was diamond cored in 22 Jan to 08 Feb 2017 to a total depth of 403.05 m. The outer surfaces of the cores were imaged and described on site before being curated, boxed and shipped to the IODP drill ship Chikyu, where they underwent comprehensive visual and instrumental analysis. Hole GT1A drilled the lower crustal section in the southern Oman Ophiolite and recovered 401.52 m of total cores (99.6% recovery). The main lithology is dominated by olivine gabbro (65.9%), followed in abundance by olivine-bearing gabbro (21.5%) and olivine melagabbro (3.9%). Minor rock types are orthopyroxene-bearing olivine gabbro (2.4%), oxide-bearing olivine gabbro (1.5%), gabbro (1.1%), anorthositic gabbro (1%), troctolitic gabbro (0.8%); orthopyroxene-bearing gabbro (0.5%), gabbronorite (0.3%); and dunite (0.3%). These rocks are divided into Lithologic Unit I to VII at 26.62 m, 88.16 m, 104.72 m, 154.04 m, 215.22 m, 306.94 m in Chikyu Curated Depth in descending order; Unit I and II consist of medium-grained olivine gabbro with lower olivine abundance in Unit II. Unit III is medium-grained olivine melagabbros, marked by an increase in olivine. Unit IV is relatively homogenous medium-grained olivine gabbros with granular textures. Unit V is identified by the appearance of fine-grained gabbros, but the major rocktypes are medium grained olivine gabbros. Unit VI is medium-grained olivine gabbro, marked by appearance of orthopyroxene. Unit VII

Processes Governing Alkaline Groundwater Chemistry within a Fractured Rock (Ophiolitic Mélange Aquifer Underlying a Seasonally Inhabited Headwater Area in the Aladağlar Range (Adana, Turkey

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Cüneyt Güler

2017-01-01

Full Text Available The aim of this study was to investigate natural and anthropogenic processes governing the chemical composition of alkaline groundwater within a fractured rock (ophiolitic mélange aquifer underlying a seasonally inhabited headwater area in the Aladağlar Range (Adana, Turkey. In this aquifer, spatiotemporal patterns of groundwater flow and chemistry were investigated during dry (October 2011 and wet (May 2012 seasons utilizing 25 shallow hand-dug wells. In addition, representative samples of snow, rock, and soil were collected and analyzed to constrain the PHREEQC inverse geochemical models used for simulating water-rock interaction (WRI processes. Hydrochemistry of the aquifer shows a strong interseasonal variability where Mg–HCO3 and Mg–Ca–HCO3 water types are prevalent, reflecting the influence of ophiolitic and carbonate rocks on local groundwater chemistry. R-mode factor analysis of hydrochemical data hints at geochemical processes taking place in the groundwater system, that is, WRI involving Ca- and Si-bearing phases; WRI involving amorphous oxyhydroxides and clay minerals; WRI involving Mg-bearing phases; and atmospheric/anthropogenic inputs. Results from the PHREEQC modeling suggested that hydrogeochemical evolution is governed by weathering of primary minerals (calcite, chrysotile, forsterite, and chromite, precipitation of secondary minerals (dolomite, quartz, clinochlore, and Fe/Cr oxides, atmospheric/anthropogenic inputs (halite, and seasonal dilution from recharge.

Peridote-water interaction generating migration pathways of H2-rich fluids in subduction context: Common processes in the ophiolites of Oman, New-Caledonia, Philippines and Turkey

Science.gov (United States)

Deville, E. P.; Prinzhofer, A.; Pillot, D.; Vacquand, C.; Sissmann, O.

2010-12-01

The occurrence of H2 flows which were punctually known notably in the ophiolites of Oman, Zambales (Philippines) and Antalya (Turkey) appears to be a widespread phenomenon in these major peridotite massifs associated with ancient or active subduction processes. Similar H2-rich gas flows have been discovered also in the peridotite of New-Caledonia. H2 concentrations are locally high (commonly 60 to90% in Oman). H2 is frequently degassing in hyperalkaline springs but the highest flows were found directly expelled from fractures in the peridotites. Obviously, within the fracture systems, gas and associated hyperalkaline water separate at shallow depth close to the top of the upper aquifer level. Locally high flows of gas migrate vertically in the fractures, whereas water with degassing H2 tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. The genesis of natural H2 is interpreted as the result of the interaction, at depth, between ultrabasic mantle rocks in the upper plate and water expelled by the subducted sediments by oxidation of metals (Fe2+, Mn2+) and reduction of water during serpentinisation. CH4 is commonly associated to the H2-rich fluids and it is interpreted as the result of the reduction of available CO2 at depth. N2 is also commonly associated to the H2-rich fluids in the ophiolites, whereas N2 flows (within H2) were found in the subducted sediments (below the sole décollement of the peridotite) where it can be observed (Oman and New-Caledonia). Within the peridotites, the hyperalkaline water is rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal décollement of the ophiolites and the peridotite-gabbro contact (Moho). This hyperalkaline water migration induces a chain of diagenetic reactions starting at depth within the fracture systems by the

Transfer of subduction fluids into the deforming mantle wedge during nascent subduction: Evidence from trace elements and boron isotopes (Semail ophiolite, Oman)

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Prigent, C.; Guillot, S.; Agard, P.; Lemarchand, D.; Soret, M.; Ulrich, M.

2018-02-01

The basal part of the Semail ophiolitic mantle was (de)formed at relatively low temperature (LT) directly above the plate interface during "nascent subduction" (the prelude to ophiolite obduction). This subduction-related LT deformation was associated with progressive strain localization and cooling, resulting in the formation of porphyroclastic to ultramylonitic shear zones prior to serpentinization. Using petrological and geochemical analyses (trace elements and B isotopes), we show that these basal peridotites interacted with hydrous fluids percolating by porous flow during mylonitic deformation (from ∼850 down to 650 °C). This process resulted in 1) high-T amphibole crystallization, 2) striking enrichments of minerals in fluid mobile elements (FME; particularly B, Li and Cs with concentrations up to 400 times those of the depleted mantle) and 3) peridotites with an elevated δ11B of up to +25‰. These features indicate that the metasomatic hydrous fluids are most likely derived from the dehydration of subducting crustal amphibolitic materials (i.e., the present-day high-T sole). The rapid decrease in metasomatized peridotite δ11B with increasing distance to the contact with the HT sole (to depleted mantle isotopic values in <1 km) suggests an intense interaction between peridotites and rapid migrating fluids (∼1-25 m.y-1), erasing the initial high-δ11B subduction fluid signature within a short distance. The increase of peridotite δ11B with increasing deformation furthermore indicates that the flow of subduction fluids was progressively channelized in actively deforming shear zones parallel to the contact. Taken together, these results also suggest that the migration of subduction fluids/melts by porous flow through the subsolidus mantle wedge (i.e., above the plate interface at sub-arc depths) is unlikely to be an effective mechanism to transport slab-derived elements to the locus of partial melting in subduction zones.

The ophiolite massif of Kahnuj (western Makran, Southern Iran): new geological and geochronological data; Le massif ophiolitique de Kahnuj (Makran occidental, Iran meridional): nouvelles donnees geologiques et geochronologiques

Energy Technology Data Exchange (ETDEWEB)

Kananian, A. [University of Tarbiat Modarress, Geological Dept., Faculty of Science, Teheran (Iran, Islamic Republic of); Juteau, Th.; Bellon, H. [Universite de Bretagne Occidentale, IUEM, 29 - Brest (France); Darvishzadeh, A. [University of Teheran, Geological Dept., Faculty of Science, Teheran (Iran, Islamic Republic of); Sabzehi, M. [Geological Survey of Iran, Teheran (Iran, Islamic Republic of); Whitechurch, H. [Universite Louis Pasteur, EOST, Institut de Physique du Globe, 67 - Strasbourg (France); Ricou, L.E. [Institut de Physique du Globe, 75 - Paris (France)

2001-05-01

The ophiolite massif of Kahnuj (600 km{sup 2}) consists, from bottom to top, of layered gabbros, isotropic gabbros and ouralite gabbros, agmatites of dioritic to plagio-granitic composition, a sheeted dyke complex and lastly a basaltic pillow lava unit. Amphiboles from gabbros were dated ({sup 40}K-{sup 40}Ar ages) between 156 and 139 Ma and the agmatites are nearly contemporaneous. Potassic granitic veins dated at 93-88 Ma are related to the development of the Ganj arc complex. (authors)

The subduction-accretion history of the Bangong-Nujiang Ocean: Constraints from provenance and geochronology of the Mesozoic strata near Gaize, central Tibet

Science.gov (United States)

Li, Shun; Ding, Lin; Guilmette, Carl; Fu, Jiajun; Xu, Qiang; Yue, Yahui; Henrique-Pinto, Renato

2017-04-01

The Mesozoic strata, within the Bangong-Nujiang suture zone in central Tibet, recorded critical information about the subduction-accretion processes of the Bangong-Nujiang Ocean prior to the Lhasa-Qiangtang collision. This paper reports detailed field observations, petrographic descriptions, sandstone detrital zircon U-Pb ages and Hf isotopic analyses from an accretionary complex (preserved as Mugagangri Group) and the unconformably overlying Shamuluo Formation near Gaize. The youngest detrital zircon ages, together with other age constraints from literature, suggest that the Mugagangri Group was deposited during late Triassic-early Jurassic, while the Shamuluo Formation was deposited during late Jurassic-early Cretaceous. Based on the differences in lithology, age and provenance, the Mugagangri Group is subdivided into the upper, middle and lower subunits. These units are younging structurally downward/southward, consistent with models of progressive off-scrapping and accretion in a southward-facing subduction complex. The upper subunit, comprising mainly quartz-sandstone and siliceous mud/shale, was deposited in abyssal plain environment close to the Qiangtang passive margin during late Triassic, with sediments derived from the southern Qiangtang block. The middle and lower subunits comprise mainly lithic-quartz-sandstone and mud/shale, containing abundant ultramafic/ophiolitic fragments. The middle subunit, of late Triassic-early Jurassic age, records a transition in tectono-depositional setting from abyssal plain to trench-wedge basin, with sudden influx of sediments sourced from the central Qiangtang metamorphic belt and northern Qiangtang magmatic belt. The appearance of ultramafic/ophiolitic fragments in the middle subunit reflects the subduction initiation. The lower subunit was deposited in a trench-wedge basin during early Jurassic, with influx of Jurassic-aged zircons originating from the newly active southern Qiangtang magmatic arc. The lower subunit

Tectonic Evolution of Jabal Tays Ophiolite Complex, Eastern Arabian Shield, Saudi Arabia

Science.gov (United States)

AlHumidan, Saad; Kassem, Osama; Almutairi, Majed; Al-Faifi, Hussain; Kahal, Ali

2017-04-01

Microstructural analysis is important for investigation of tectonic evaluation of Jable Tays area. Furthermore, the Jable Tays ophiolite complex is effected by Al Amar -Idsas fault. The nature of the Al Amar-Idsas fault is a part of the Eastern Arabian Shield, which was subjected to multiple interpretations. Through fieldwork investigation, microscopic examination, and microstructural analysis, we aim to understand the evolution and tectonic setting of the Jable Tays area. Finite-strain data displays that the Abt schist, the metavolcanics and the metagranites are highly to moderately deformed. The axial ratios in the XZ section range from 1.40 to 2.20. The long axes of the finite-strain ellipsoids trend NW- SE and W-E in the Jable Tays area while, their short axes are subvertical to subhorizontal foliations. The strain magnitude does not increase towards the tectonic contacts between the Abt schist and metavolcano-sedimentary. While majority of the obtained data indicate a dominant oblate with minor prolate strain symmetries in the Abt schist, metavolcano-sedimentary and metagranites. The strain data also indicate flattening with some constriction. We assume that the Abt schist and the metavolcano-sedimentry rocks have similar deformation behavior. The finite strain in the studied rocks accumulated during the metamorphism that effected by thrusting activity. Based on these results, we finally concluded that the contact between Abt schist and metavolcano-sedimentary rocks were formed during the progressive thrusting under brittle to semi-ductile deformation conditions by simple shear that also involved a component of vertical shortening, causing subhorizontal foliation in Jable Tays area.

Tectonics of the Qinling (Central China): Tectonostratigraphy, geochronology, and deformation history

Science.gov (United States)

Ratschbacher, L.; Hacker, B.R.; Calvert, A.; Webb, L.E.; Grimmer, J.C.; McWilliams, M.O.; Ireland, T.; Dong, S.; Hu, Jiawen

2003-01-01

The Qinling orogen preserves a record of late mid-Proterozoic to Cenozoic tectonism in central China. High-pressure metamorphism and ophiolite emplacement (Songshugou ophiolite) assembled the Yangtze craton, including the lower Qinling unit, into Rodinia during the ~1.0 Ga Grenvillian orogeny. The lower Qinling unit then rifted from the Yangtze craton at ~0.7 Ga. Subsequent intra-oceanic arc formation at ~470-490 Ma was followed by accretion of the lower Qinling unit first to the intra-oceanic arc and then to the Sino-Korea craton. Subduction then imprinted a ~400 Ma Andean-type magmatic arc onto all units north of the northern Liuling unit. Oblique subduction created Silurian-Devonian WNW-trending, sinistral transpressive wrench zones (e.g., Lo-Nan, Shang-Dan), and Late Permian-Early Triassic subduction reactivated them in dextral transpression (Lo-Nan, Shang-Xiang, Shang-Dan) and subducted the northern edge of the Yangtze craton. Exhumation of the cratonal edge formed the Wudang metamorphic core complex during dominantly pure shear crustal extension at ~230-235 Ma. Post-collisional south-directed shortening continued through the Early Jurassic. Cretaceous reactivation of the Qinling orogen started with NW-SE sinistral transtension, coeval with large-scale Early Cretaceous crustal extension and sinistral transtension in the northern Dabie Shan; it presumably resulted from the combined effects of the Siberia-Mongolia-Sino-Korean and Lhasa-West Burma-Qiangtang-Indochina collisions and Pacific subduction. Regional dextral wrenching was active within a NE-SW extensional regime between ~60 and 100 Ma. An Early Cretaceous Andean-type continental magmatic arc, with widespread Early Cretaceous magmatism and back-arc extension, was overprinted by shortening related to the collision of Yangtze-Indochina Block with the West Philippines Block. Strike-slip and normal faults associated with Eocene half-graben basins record Paleogene NNE-SSW contraction and WNW-ESE extension

One-carbon (bio ?) Geochemistry in Subsurface Waters of the Serpentinizing Coast Range Ophiolite

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Hoehler, Tori M.; Mccollom, Tom; Schrenk, Matt; Cardace, Dawn

2011-01-01

Serpentinization - the aqueous alteration of ultramafic rocks - typically imparts a highly reducing and alkaline character to the reacting fluids. In turn, these can influence the speciation and potential for metabolism of one-carbon compounds in the system. We examined the aqueous geochemistry and assessed the biological potential of one-carbon compounds in the subsurface of the McLaughlin Natural Reserve (Coast Range Ophiolite, California, USA). Fluids from wells sunk at depths of 25-90 meters have pH values ranging from 9.7 to 11.5 and dissolved inorganic carbon (DIC concentrations) generally below 60 micromolar. Methane is present at concentrations up to 1.3 millimolar (approximately one-atmosphere saturation), and hydrogen concentrations are below 15 nanomolar, suggesting active consumption of H2 and production of CH4. However, methane production from CO2 is thermodynamically unfavorable under these conditions. Additionally, the speciation of DIC predominantly into carbonate at these high pH values creates a problem of carbon availability for any organisms that require CO2 (or bicarbonate) for catabolism or anabolism. A potential alternative is carbon monoxide, which is present in these waters at concentrations 2000-fold higher than equilibrium with atmospheric CO. CO is utilized in a variety of metabolisms, including methanogenesis, and bioavailability is not adversely affected by pH-dependent speciation (as for DIC). Methanogenesis from CO under in situ conditions is thermodynamically favorable and would satisfy biological energy requirements with respect to both Gibbs Energy yield and power.

An eclogite-bearing continental tectonic slice in the Zermatt-Saas high-pressure ophiolites at Trockener Steg (Zermatt, Swiss Western Alps)

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Weber, Sebastian; Bucher, Kurt

2015-09-01

The Theodul Glacier Unit (TGU) at "Trockener Steg" represents a continental slice, embedded within the ophiolitic Zermatt-Saas Zone. The Zermatt-Saas Zone is the remnant of the Piemonte-Liguria oceanic lithosphere, formed in the middle Jurassic and subducted up to eclogite facies conditions in the Early Tertiary. The close spatial association of the TGU to the Zermatt-Saas Zone permits a comparison of the metamorphic evolution of the units by detailed field mapping and a petrological investigation of eclogites. The eclogites from both tectono-metamorphic units can be clearly distinguished by their textures, mineral assemblages and by mineral and bulk-rock composition. Geothermobarometry and computed assemblage stability diagrams for the TGU eclogites indicate P-T conditions of 2.2 ± 0.1 GPa and 580 ± 50 °C. These derived P-T conditions must be considered as minimum peak metamorphic conditions the rocks achieved during subduction. The P-T data are different from those derived for eclogites of Zermatt-Saas Zone adjacent to the Theodul Glacier Unit, that reached maximal burial depths at 2.3-2.4 GPa and 500 ± 50 °C. While the estimates of the eclogites of Zermatt-Saas Zone are in good agreement with some of the previous studies, the contrasting P-T estimates for the TGU eclogites suggest that the Zermatt-Saas complex must be subdivided into several tectonic subunits. The non-uniform peak conditions over the "Trockener Steg" area and the maximum pressures conditions reported from ultra-high pressure localities within Zermatt-Saas Zone suggest, that individual tectonic slices have been assembled after detachment from the slab at the return-point, i.e. along the exhumation path. Detached packages of rocks may range from small tectonic slices up to several kilometer-sized fragments. The TGU is separated from the surrounding rocks of the ophiolite unit by two major tectonic contacts. In addition, the formation of biotite-rich crusts along the basal contact of the TGU

Aqueous Geochemical Dynamics at the Coast Range Ophiolite Microbial Observatory and The Case for Subsurface Mixing of Regional Groundwaters

Science.gov (United States)

Cardace, D.; Schrenk, M. O.; McCollom, T. M.; Hoehler, T. M.

2017-12-01

Serpentinization is the aqueous alteration (or hydration) of olivine and pyroxene minerals in ultramafic rocks, occurring in the seabed and ultramafic units on continents, such as at the Coast Range Ophiolite (CRO) in northern California, USA. Mineral products of serpentinization include serpentine, magnetite, brucite, talc, oxyhydroxides, carbonates, and diverse clay minerals. Such mineral transformations generate extremely high pH solutions with characteristic cation and dissolved metal loads, transmitting CH4, H2, and CO gas mixtures from depth; deep life in ultramafic terrains is thought to be fueled by chemical energy derived from these geochemical reactions. The installation of 8 groundwater monitoring wells in the CRO has allowed frequent monitoring since 2011. Influx of deeply sourced, serpentinization-influenced waters is evidenced by related geochemical shifts (e.g., pH, oxidation-reduction potential), but is apparently mixing with other, regionally important groundwater types. Evaluation salinity loads in concert with other parameters, we model the mixing scenario of this site of ongoing scientific study and experimentation.

Endeavor research into evolving paradigms around ophiolites: the case of the oceanic igneous complexes of Costa Rica

International Nuclear Information System (INIS)

Alvarado, Guillermo E.; Denyer, Perci; Gazel, Esteban

2009-01-01

Studies on the radiolarite igneous (ophiolitic) complexes were done for more than one century in Costa Rica that range from Jurassic to Eocene. These studies can be grouped in four stages of knowledge: 1) from 1904 to 1957 were recognized the cherts, and the mafic and ultramafic igneous complexes, the first regional maps were done, and the first time were recognized ellipsoidal basalts, now widely known as pillow lavas. 2) From 1958 to 1978 the complexes were seen under the concept of the association of ophiolites (serpentine, gabbro, diabase, basalts, and related rocks) and interpreted the radiolarites as deep-sea sediments. The stage is characterized by the seminal work of Gabriel Dengo and by the first geochemical analyses in the framework of the plate tectonics. 3) A huge amount of geochemical data, paleontological and K/Ar ages were published from 1979 to 1994 and it was the stage of more controversial papers, their interpretation varied for the same locality (i.e. (Nicoya Peninsula) from relative simple stratigraphic model to a very complex nappe slices, and from a simple tectonic evolution (in situ and formed by a mid oceanic ridge volcanism) to a multistage evolution (terrains, and mid oceanic ridge, aseismic ridge, intraplate and island arc volcanism). The situation was similar in the other Costa Rican oceanic complexes. 4) The outlook for 1995 to the present it has been clarified and mutual agreement between the different groups. The stage is characterized by joint collaboration, the use of modern laboratory techniques as Sr, Nd, and Pb isotopes, major, trace and complete rare earth elements. 40A r/ 39 Ar dating, and volcanological criteria, together with detailed field mapping. The main new result of these studies was that the radiolarites (164-84 Ma) in the Nicoya Peninsula were significatively older than the basic igneous rocks (140-84 Ma), indicating a complex magmatic event intruding and erupting into the thick sedimentary sequence. For other areas

Petrogenesis and tectonic implications of gabbro and plagiogranite intrusions in mantle peridotites of the Myitkyina ophiolite, Myanmar

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Xu, Yang; Liu, Chuan-Zhou; Chen, Yi; Guo, Shun; Wang, Jian-Gang; Sein, Kyaing

2017-07-01

Centimeter-size intrusions of gabbros and plagiogranites occur in mantle peridotites of the Myitkyina ophiolite, Myanmar. The gabbros mainly consist of plagioclase and clinopyroxene, whereas orthopyroxene occasionally occurs. The plagiogranites are mainly composed of plagioclase, quartz and amphibole, with small amount of accessory minerals, such as zircon, apatite and rutile. Plagioclase in the gabbros varies from andesine to anorthite (An37-91), whereas plagioclase in the plagiogranites is less calcic (An1-40). Clinopyroxene in the gabbros is pervasively altered to hornblende. The gabbros contain 42.97-52.88 wt% SiO2, which show negative correlations with Al2O3, CaO and MgO, but positive correlations with Na2O, P2O5 and TiO2. Microtextural relations reveal the crystallization of clinopyroxene prior to plagioclase in the Myitkyina gabbros. This suggests that the gabbros were crystallized from hydrous melts, which is also supported by the occurrence of orthopyroxene and anorthitic plagioclase in some gabbros. The gabbros have slightly enriched Sr-Nd isotopes, with initial 87Sr/86Sr ratios of 0.703938-0.706609 and εNd(t) values of + 2.4-+7.2, and relatively variable Hf isotopes, with εHf(t) values of + 13.4-+24.9. A subduction component is required to explain the decoupled Nd-Hf isotopes of the gabbros. Binary mixing suggests that addition of ca 2% subducted sediments to a depleted mantle can account for the Nd-Hf decoupling. Therefore, both petrological and geochemical data of the gabbros support that the Myitkyina ophiolite was originated in a supra-subduction zone setting. The plagiogranites have compositions of tonalites and trondhjemites, containing 56.93-77.93 wt% SiO2, 1.27-10.79 wt% Na2O and 0.05-0.71 wt% K2O. They are slightly enriched in LREE over HREE and display positive anomalies in Eu, Zr, Hf but negative Nb anomalies. Very low TiO2 contents (0.03-0.2 wt%) of the plagiogranites suggest that they were not products of fractional crystallization of MORB

A stable isotope study of serpentinization in the Fengtien ophiolite, Taiwan

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Tzen-Fu Yui; Hsueh-Wen Yeh (Univ. of Hawaii, Honolulu (USA)); Chihming Wang Lee (National Taiwan Univ. (Taiwan))

1990-05-01

Detailed H- and O-isotopic studies of serpentinites of Fengtien ophiolite have been made in order to enhance our knowledge on the process of serpentinization. Pseudomorphic lizardites have {delta}{sup 18}O = +3.6{per thousand} and {delta}D = {minus}48 to {minus}49{per thousand}; bladed-mat and foliated antigorites have {delta}{sup 18}O = +3.5 to +5.8{per thousand} and {delta}D = {minus}45 to {minus}69{per thousand}; slickensided antigorites have {delta}{sup 18}O = +4.1 to +4.9{per thousand} and {delta}D = {minus}46 to {minus}50{per thousand}; picrolites have {delta}{sup 18}O = +4.2 to +4.3{per thousand} and {delta}D = {minus}65 to {minus}67{per thousand}; and slickensided chrysotiles have {delta}{sup 18}O = +4.1 to +4.5{per thousand} and {delta}D = {minus}80{per thousand}. It is suggested that lizardite might have formed in an oceanic environment, whereas antigorite and chrysotile have formed in continental environments. These results depict complicated multiple serpentinization processes. Isotopic temperatures calculated using {delta}{sup 18}O values of coexisting fissure-filling minerals range from 325 to 370{degree}C, which are consistent with those derived from phase equilibria involving serpentines. The narrow range of {delta}{sup 18}O and wide range of {delta}D values for antigorite and chrysotile also demonstrate that water/rock ratios during these serpentinizations should not have been high. These Fengtien serpentines fall outside either of the continental domains described by Wenner and Taylor (1973, 1974); and fall within their oceanic domain. We suggest that the domains proposed by Wenner and Taylor (1973, 1974) should be extended and that the terms, especially the continental antigorite and the continental lizardite-chrysotile, should be purely occurrence-descriptive.

Preliminary isotopic data from some amphibolites of the metamorphic basement of the Colombian Central Cordillera

International Nuclear Information System (INIS)

Correa M, Ana Maria; Martens K, Uwe; Ordonez C, Oswaldo; Pimentel, Marcio M; Restrepo A, Jorge Julian

2001-01-01

Various amphibolite bodies are exposed in the Antioquia Department, Colombia, mainly around the cities of Medellin and El Retiro. Two types of amphibolites occur in the study area; the first one is considered as part of an ophiolite complex and the second one correspond to amphibolites associated to metasediments from the basement of the Colombian Central Cordillera. The present work refers to these last ones. The relationships between amphibolite bodies and other lythological units are the following ones: Intercalation of amphibolites layers with metasediments in the unit migmatites and granulites of El Retiro. The Medellin amphibolites are conformably overlaid by the paragneisses of Las Penas. The granodiorite body represented by the Antioquian Batolith is intrusive in the metamorphic rocks and the Medellin Dunites unit is in thrust fault contact with Medellin amphibolites. These amphibolites have been studied by Botero (1963), Gonzalez (1976 and 1980), Restrepo and Toussaint (1984), Ardila (1986), Restrepo (1986), Rendon (1999) and, Correa and Martens (2000). Available radiometric ages on the amphibolites come from former works by Restrepo y Toussaint (1978), Restrepo et al. (1991) that presented K-Ar ages in amphiboles and a Rb-Sr isochron which yielded a Cretaceous age that they interpreted as a metamorphic age. This work presents new evidences, obtained from field work, petrography, rock geochemistry and specially the first isotopic data on these amphibolites from the Central Cordillera Metamorphic Basement (au)

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Indian Academy of Sciences (India)

AAA. E. Tethys-Himalaya. (Paleozoic-Eocene). - Zanskar Shear Zone (ZSZ). Higher Himalaya Crystalline. Dras Wolcanics ha-. Ophiolite Melange Main Central Thrust (MCT). (Jurassic - Cretaceous) HID Kishtwar Window. Lesser Himalaya. "T" indus Thrust -A-A- Main Boundary Thrust (MBT). BSS Siwaliks Molasse (Neogene).

Distribution and PGE mineralization in the formation of chromitite in ophiolite complexes (Ospina-Kitoi Kharanur and ultrabasic massifs of Eastern Sayan, Sousern Siberia)

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Kiseleva, Olga; Zhmodik, Sergei

2015-04-01

New study of PGE in restitic ultrabasic (Kharanur and Ospin-Kitoi) massifs from North and South branches (Dobretsov et al., 1985) of the ophiolite complexes in south-eastern part of the Eastern Sayan show their presence in chromitites of both branches belonging to the different geodynamic settings. Modern concepts model includes several mechanisms of podiform chromitite origin reflected in the chemistry of Cr-spinels (Arai, Yurimoto, 1994; Ballhaus, 1998; Uysal et al., 2009 et al.): 1) partial melting of upper mantle rocks, 2) mixing of primitive melts with melts enriched in SiO2, 3) melt-rock interaction. We estimated the types of interaction of mafic melts with mantle peridotites, with the formation of chromite bodies. For ore chrome spinelides from northern branch (Al2O3) melt = 8 - 14 wt%, (TiO2) melt = 0 - 0,4 wt%, (Fe/Mg) melt = 0,5 - 2,4; Southern branch (Al2O3) melt = 10 - 13 wt%, (TiO2) melt = 0,1 wt%, (Fe/Mg) melt = 0,3 - 1 (Kiseleva, 2014). There are two types of PGE distribution Os-Ir-Ru (I) and Pt-Pd (II). Type I chromitites (mid-Al#Cr-spinels) revealed only Os-Ir-Ru distributions; type II (low-Al#Cr spinelides) show both Os-Ir-Ru and (Pt-Pd) distributions (Kiseleva et al., 2012, 2014). PGE distribution in ultramafic peridotites and chromitites reflects PGE fractionation during partial melting (Barnes et al., 1985; Rehkämper et al., 1997). Processes bringing to extreme fractionation of PGE, may be associated with fluid-saturated supra subduction environment where melting degree near 20% and above is sufficient for the release of PGE from the mantle source (Dick, Bullen, 1984; Naldrett, 2010). Enrichment in PPGE together with a high content of IPGE in same chromite bodies is attributed to the second step of melting, and formation of S-enriched and saturated in PGE melts (Hamlyn, Keays, 1986; Prichard et al., 1996). For type I chromitites platinum group minerals (PGM) are presented by Os-Ir-Ru system. In type II chromitites PGM are represented by Os

Differences in composition of shallow-water marine benthic communities associated with two ophiolitic rock substrata

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Bavestrello, Giorgio; Bo, Marzia; Betti, Federico; Canessa, Martina; Gaggero, Laura; Rindi, Fabio; Cattaneo-Vietti, Riccardo

2018-01-01

On marine rocky shores, several physical, chemical and biological processes operate to maintain the benthic assemblages' heterogeneity, but among the abiotic factors, the composition and texture of the rocky substrata have been only sporadically considered. However, biomineralogical studies have demonstrated an unsuspected ability of the benthic organisms to interact at different levels with rocky substrata. Therefore, the mineralogy of the substratum can affect the structure of benthic communities. To evaluate this hypothesis, the macrobenthic assemblages developed on two different ophiolitic rocks (serpentinites and metagabbros) in contact at a restricted stretch of the western Ligurian Riviera (western Mediterranean Sea), with identical environmental and climatic conditions, were analysed. Samplings were carried out at four bathymetric levels (+1m, 0m, -1m, and -3m respect to the mean sea level) and the analysis of the data evidenced differences in terms of species distribution and percent coverage. Algal communities growing on metagabbros were poorer in species richness and showed a much simpler structure when compared to the assemblages occurring on the serpentinites. The most widely distributed animal organism, the barnacle Chthamalus stellatus, was dominant on serpentinites, and virtually absent on metagabbros. Our results suggest a complex pattern of interactions between lithology and benthic organisms operating through processes of inhibition/facilitation related to the mineral properties of the substratum.

Modélisation magnétique de la suture ophiolitique de Bou Azzer El Graara (Anti-Atlas central, Maroc). Implications sur la reconstitution géodynamique panafricaine

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Soulaimani, Abderrahmane; Jaffal, Mohammed; Maacha, Lhou; Kchikach, Azzouz; Najine, Abdessamad; Saidi, Abdellatif

2006-02-01

Aeromagnetic data of the Anti-Atlas Mountains show an important magnetic anomaly along the 'Major Anti-Atlas Fault', produced by different mafic and ultramafic rocks of a Neoproterozoic ophiolite complex. The magnetic modelling of Bou Azzer-El Graara ophiolitic suture shows a deep-seated anomaly through the upper continental crust corresponding to a north-dipping subduction. The polarity of the Pan-African subduction in the Anti-Atlas is therefore compatible with the contemporaneous Pan-African orogenic belts, where polarity of subduction dipped away from the West African Craton during the amalgamation of Western Gondwana. To cite this article: A. Soulaimani et al., C. R. Geoscience 338 (2006).

Digital geologic map and Landsat image map of parts of Loralai, Sibi, Quetta, and Khuzar Divisions, Balochistan Province, west-central Pakistan

Science.gov (United States)

Maldonado, Florian; Menga, Jan Mohammad; Khan, Shabid Hasan; Thomas, Jean-Claude

2011-01-01

This generalized digital geologic map of west-central Pakistan is a product of the Balochistan Coal-Basin Synthesis Study, which was part of a cooperative program of the Geological Survey of Pakistan and the United States Geological Survey. The original nondigital map was published by Maldonado and others (1998). Funding was provided by the Government of Pakistan and the United States Agency for International Development. The sources of geologic map data are primarily 1:253,440-scale geologic maps obtained from Hunting Survey Corporation (1961) and the geologic map of the Muslim Bagh Ophiolite Complex and Bagh Complex area. The geology was modified based on reconnaissance field work and photo interpretation of 1:250,000-scale Landsat Thematic Mapper photo image. The descriptions and thicknesses of map units were based on published and unpublished reports and converted to U.S. Geological Survey format. In the nomenclature of the Geological Survey of Pakistan, there is both an Urak Group and an Urak Formation.

Metamorphic history and geodynamic significance of the Early Cretaceous Sabzevar granulites (Sabzevar structural zone, NE Iran

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M. Nasrabady

2011-11-01

Full Text Available The Iranian ophiolites are part of the vast orogenic suture zones that mark the Alpine-Himalayan convergence zone. Few petrological and geochronological data are available from these ophiolitic domains, hampering a full assessment of the timing and regimes of subduction zone metamorphism and orogenic construction in the region. This paper describes texture, geochemistry, and the pressure-temperature path of the Early Cretaceous mafic granulites that occur within the Tertiary Sabzevar ophiolitic suture zone of NE Iran. Whole rock geochemistry indicates that the Sabzevar granulites are likely derived from a MORB-type precursor. They are thus considered as remnants of a dismembered dynamo-thermal sole formed during subduction of a back-arc basin (proto-Sabzevar Ocean formed in the upper-plate of the Neotethyan slab. The metamorphic history of the granulites suggests an anticlockwise pressure-temperature loop compatible with burial in a hot subduction zone, followed by cooling during exhumation. Transition from a nascent to a mature stage of oceanic subduction is the geodynamic scenario proposed to accomplish for the reconstructed thermobaric evolution. When framed with the regional scenario, results of this study point to diachronous and independent tectonic evolutions of the different ophiolitic domains of central Iran, for which a growing disparity in the timing of metamorphic equilibration and of pressure-temperature paths can be expected to emerge with further investigations.

Palladium, platinum, rhodium, iridium and ruthenium in chromite- rich rocks from the Samail ophiolite, Oman.

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Page, N.J.; Pallister, J.S.; Brown, M.A.; Smewing, J.D.; Haffty, J.

1982-01-01

30 samples of chromitite and chromite-rich rocks from two stratigraphic sections, 250 km apart, through the basal ultramafic member of the Samail ophiolite were spectrographically analysed for platinum-group elements (PGE) and for Co, Cu, Ni and V. These data are reported as are Cr/(Cr + Al), Mg/(Mg + Fe) and wt.% TiO2 for most samples. The chromitite occurs as pods or lenses in rocks of mantle origin or as discontinuous layers at the base of the overlying cumulus sequence. PGE abundances in both sections are similar, with average contents in chromite-rich rocks: Pd 8 ppb, Pt 14 ppb, Rh 6 ppb, Ir 48 ppb and Ru 135 ppb. The PGE data, combined with major-element and petrographic data on the chromitite, suggest: 1) relatively larger Ir and Ru contents and highest total PGE in the middle part of each section; 2) PGE concentrations and ratios do not correlate with coexisting silicate and chromite abundances or chromite compositions; 3) Pd/PGE, on average, increases upward in each section; 4) Samail PGE concentrations, particularly Rh, Pt and Pd, are lower than the average values for chromite-rich rocks in stratiform intrusions. 2) suggests that PGEs occur in discrete alloy or sulphide phases rather than in the major oxides or silicates, and 4) suggests that chromite-rich rocks from the oceanic upper mantle are depleted in PGE with respect to chondrites. L.C.C.

Early Carboniferous adakite-like and I-type granites in central Qiangtang, northern Tibet: Implications for intra-oceanic subduction and back-arc basin formation within the Paleo-Tethys Ocean

Science.gov (United States)

Liu, Jin-Heng; Xie, Chao-Ming; Li, Cai; Wang, Ming; Wu, Hao; Li, Xing-Kui; Liu, Yi-Ming; Zhang, Tian-Yu

2018-01-01

Recent studies have proposed that the Late Devonian ophiolites in the central Qiangtang region of northern Tibet were formed in an oceanic back-arc basin setting, which has led to controversy over the subduction setting of the Longmucuo-Shuanghu-Lancangjiang Suture Zone (LSLSZ) during the Late Devonian to Early Carboniferous. In this paper we present new data about a suite of granite plutons that intrude into ophiolite in central Qiangtang. Our aim was to identify the type of subduction and to clarify the existence of an intra-oceanic back-arc basin in the LSLSZ during the Late Devonian to Early Carboniferous. The suite of granites consists of monzogranites, syenogranites, and granodiorites. Our laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb data yielded Early Carboniferous crystallization ages of 357.2 Ma, 357.4 Ma and 351.1 Ma. We subsequently investigated the petrogenesis and tectonic setting of these granites based on their geochemical and Hf isotopic characteristics. First, we divided the granites into high Sr/Y (HSG) and low Sr/Y granites (LSG). The HSG group contains monzogranites and granodiorites that have similar geochemical characteristics to adakites (i.e., high Sr/Y and La/Yb ratios, low MgO, Y, and Yb contents, and no pronounced negative Eu anomaly), although they have slightly lower Sr and Al2O3 contents, caused by crystal fractionation during late magmatic evolution. Therefore, we define the HSG group as adakite-like granites. The study of the HSG shows that they are adakite-like granites formed by partial melting of oceanic crust and experience fractional crystallization process during late evolution. However, some differences between the monzogranites and granodiorites indicate that there are varying degree contributions of subducted sediments during diagenesis. The LSG group contains syenogranites that have distinct negative correlations between their P2O5 and SiO2 contents, and Y and Th contents have significant positive

Seawater Circulation and Thermal Sink at OCEAN Ridges - FIELD Evidence in Oman Ophiolite

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Nicolas, A. A.; Boudier, F. I.; Cathles, L. M.; Buck, W. R.; Celerier, B. P.

2014-12-01

Exceptionally, the lowermost gabbros in the Oman ophiolite are black and totally fresh, except for minute traces of impregnation by seawater fluids at very high temperature (~1000°C). These black gabbros sharply contrast with normal, whitish gabbros altered down to Low-T~500-350°C. These hydrous alterations are ascribed to an unconventional model of seawater circulation and cooling of the permanent magma chambers of fast spreading ocean ridges. In this model, gabbros issued from the magma chamber cross a ~100 m thick thermal boundary layer (TBL) before reaching a narrow, Low-T high permeability channel where the heated return seawater is flowing towards black smokers and the local gabbros are altered. Uprising mantle diapirs in Oman diverge at ~5 km on each side of the palaeo-ridge axis and feed an overlying magma chamber that closes at this distance from axis. Preservation of black gabbros along the Moho implies that the loop of seawater alteration locally does not reach Moho beyond this ~5km distance (otherwise black gabbros would be altered in whitish gabbros). This defines an internal "thermal sink" within ~5 km to the ridge axis. There, the sink is efficiently cooled by the active hydrothermal convection that is ridge transverse. This has been documented near the Galapagos ridge by marine geophysical data, within the same distance. Beyond this critical distance, the cooling system becomes dominantly conductive and ridge-parallel. The TBL and attached return flow channels must be rising into the overcooled, accreted crust. Beyond the thermal sink, the 500°C isotherm rebounds into the crust. It is only after ~ 1My of crustal drift that this isotherm penetrates into the uppermost mantle in a sustained fashion, developing serpentinites at the expense of peridotites.

Tethyan Anhydrite Preserved in the Lower Ocean Crust of the Samail Ophiolite? Evidence from Oman Drilling Project Holes GT1A and 2A

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Teagle, D. A. H.; Harris, M.; Crispini, L.; Deans, J. R.; Cooper, M. J.; Kelemen, P. B.; Alt, J.; Banerjee, N.; Shanks, W. C., III

2017-12-01

Anhydrite is important in mid-ocean ridge hydrothermal systems because of the high concentrations of calcium and sulfate in modern seawater and anhydrite's retrograde solubility. Because anhydrite hosts many powerful tracers of fluid-rock interactions (87Sr/86Sr, δ18O, δ34S, trace elements, fluid inclusions) it is useful for tracing the chemical evolution of hydrothermal recharge fluids and estimating time-integrated fluid fluxes. Anhydrite can form from heated seawater (>100°C), through water-rock reaction, or by mixing of seawater and hydrothermal fluids. Although abundant in active hydrothermal mounds, and predicted to form from downwelling, warming fluids during convection, anhydrite is rare in drill core from seafloor lavas, sheeted dikes and upper gabbros, with only minor amounts in ODP Holes 504B and 1256D. Because anhydrite can dissolve during weathering, its occurrence in ophiolites is unexpected. Instead, gypsum is present in Macquarie Island lavas and Miocene gypsum fills cavities within the Cretaceous Troodos ore deposits. Thus, the occurrence of numerous anhydrite veins in cores from the gabbroic lower crust of the Samail ophiolite in Oman was unanticipated. To our knowledge, anhydrite in Oman gabbros has not been previously reported. Oman Drilling Project Holes GT1A and GT2A were drilled into the Wadi Gideah section of the Wadi Tayin massif. Both recovered 400 m of continuous core from sections of layered gabbros (GT1) and the foliated-layered gabbro transition (GT2). Anhydrite is present throughout both holes, some in vein networks but more commonly as isolated 1-110 mm veins (>60 mm ave). Anhydrite is mostly the sole vein filling but can occur with greenschist minerals such as epidote, quartz, chlorite and prehnite. Anhydrite commonly exhibits prismatic and bladed textures but can also be capriciously microcrystalline. Though definitive cross cutting relationships are elusive, anhydrite veins cut across some greenschist veins. Anhydrite is

Geophysical Characterization of Serpentinite Hosted Hydrogeology at the McLaughlin Natural Reserve, Coast Range Ophiolite

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Ortiz, Estefania; Tominaga, Masako; Cardace, Dawn; Schrenk, Matthew O.; Hoehler, Tori M.; Kubo, Michael D.; Rucker, Dale F.

2018-01-01

Geophysical remote sensing both on land and at sea has emerged as a powerful approach to characterize in situ water-rock interaction processes in time and space. We conducted 2-D Electrical Resistivity Tomography (ERT) surveys to investigate in situ hydrogeological architecture within the Jurassic age tectonic mélange portion of the Coast Range Ophiolite Microbial Observatory (CROMO) during wet and dry seasons, where water-rock interactive processes are thought to facilitate a subsurface biosphere. Integrating survey tracks traversing two previously drilled wells, QV1,1 and CSW1,1 at the CROMO site with wireline and core data, and the Serpentine Valley site, we successfully documented changes in hydrogeologic properties in the CROMO formation, i.e., lateral and vertical distribution of conductive zones and their temporal behavior that are dependent upon seasonal hydrology. Based on the core-log-ERT integration, we propose a hydrogeological architectural model, in which the formation is composed of three distinct aquifer systems: perched serpentinite aquifer without seasonal dependency (shallow system), well-cemented serpentine confining beds with seasonal dependency (intermediate system), serpentinite aquifer (deep system), and the ultramafic basement that acts as a quasi-aquiclude (below the deep system). The stunning contrast between the seasonality in the surface water availability and groundwater storativity in the formation allowed us to locate zones where serpentinite weathering and possibly deeper serpentinization processes might have taken place. We based our findings primarily on lithological composition and the distribution of the conductive formation, our work highlights the link between serpentinite weathering processes and possible sources of water in time and space.

An alkaline spring system within the Del Puerto ophiolite (California USA): A Mars analog site

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Blank, J.G.; Green, S.; Blake, D.; Valley, J.; Kita, N.; Treiman, A.; Dobson, P.F.

2008-10-01

Mars appears to have experienced little compositional differentiation of primitive lithosphere, and thus much of the surface of Mars is covered by mafic lavas. On Earth, mafic and ultramafic rocks present in ophiolites, oceanic crust and upper mantle that have been obducted onto land, are therefore good analogs for Mars. The characteristic mineralogy, aqueous geochemistry, and microbial communities of cold-water alkaline springs associated with these mafic and ultramafic rocks represent a particularly compelling analog for potential life-bearing systems. Serpentinization, the reaction of water with mafic minerals such as olivine and pyroxene, yields fluids with unusual chemistry (Mg-OH and Ca-OH waters with pH values up to {approx}12), as well as heat and hydrogen gas that can sustain subsurface, chemosynthetic ecosystems. The recent observation of seeps from pole-facing crater and canyon walls in the higher Martian latitudes supports the hypothesis that even present conditions might allow for a rockhosted chemosynthetic biosphere in near-surface regions of the Martian crust. The generation of methane within a zone of active serpentinization, through either abiogenic or biogenic processes, could account for the presence of methane detected in the Martian atmosphere. For all of these reasons, studies of terrestrial alkaline springs associated with mafic and ultramafic rocks are particularly timely. This study focuses on the alkaline Adobe Springs, emanating from mafic and ultramafic rocks of the California Coast Range, where a community of novel bacteria is associated with the precipitation of Mg-Ca carbonate cements. The carbonates may serve as a biosignature that could be used in the search for evidence of life on Mars.

Methane Dynamics in a Tropical Serpentinizing Environment: The Santa Elena Ophiolite, Costa Rica

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Melitza Crespo-Medina

2017-05-01

Full Text Available Uplifted ultramafic rocks represent an important vector for the transfer of carbon and reducing power from the deep subsurface into the biosphere and potentially support microbial life through serpentinization. This process has a strong influence upon the production of hydrogen and methane, which can be subsequently consumed by microbial communities. The Santa Elena Ophiolite (SEO on the northwestern Pacific coast of Costa Rica comprises ~250 km2 of ultramafic rocks and mafic associations. The climatic conditions, consisting of strongly contrasting wet and dry seasons, make the SEO a unique hydrogeological setting, where water-rock reactions are enhanced by large storm events (up to 200 mm in a single storm. Previous work on hyperalkaline spring fluids collected within the SEO has identified the presence of microorganisms potentially involved in hydrogen, methane, and methanol oxidation (such as Hydrogenophaga, Methylobacterium, and Methylibium spp., respectively, as well as the presence of methanogenic Archaea (such as Methanobacterium. Similar organisms have also been documented at other serpentinizing sites, however their functions have not been confirmed. SEO's hyperalkaline springs have elevated methane concentrations, ranging from 145 to 900 μM, in comparison to the background concentrations (<0.3 μM. The presence and potential activity of microorganisms involved in methane cycling in serpentinization-influenced fluids from different sites within the SEO were investigated using molecular, geochemical, and modeling approaches. These results were combined to elucidate the bioenergetically favorable methane production and/or oxidation reactions in this tropical serpentinizing environment. The hyperalkaline springs at SEO contain a greater proportion of Archaea and methanogens than has been detected in any terrestrial serpentinizing system. Archaea involved in methanogenesis and anaerobic methane oxidation accounted from 40 to 90% of total

Jurassic-Paleogene intra-oceanic magmatic evolution of the Ankara Mélange, North-Central Anatolia, Turkey

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Sarifakioglu, E.; Dilek, Y.; Sevin, M.

2013-11-01

Oceanic rocks in the Ankara Mélange along the Izmir-Ankara-Erzincan suture zone (IAESZ) in North-Central Anatolia include locally coherent ophiolite complexes (~179 Ma and ~80 Ma), seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma), metamorphic rocks with ages of 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (~67-63 Ma). All but the arc rocks occur in a shaly-graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the Middle to Late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB) and island arc tholeiite (IAT) affinities showing moderate to significant LILE enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB) affinities. The arc-related volcanic rocks, lamprophyric dikes and syeno-dioritic plutons exhibit high-K shoshonitic to medium-to high-K calc-alkaline compositions with strong enrichment in LILE, REE and Pb, and initial ϵNd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syeno-dioritic plutons) in the southern part. The Early to Late Jurassic and Late Cretaceous epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the Northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the seamount volcanic rocks indicate that the Northern Neotethys was an open ocean with its MORB-type oceanic lithosphere by the Early Triassic. The Latest Cretaceous-Early Paleocene island arc volcanic, dike and plutonic rocks with

Petrology and geochemistry of mafic magmatic rocks from the Sarve-Abad ophiolites (Kurdistan region, Iran): Evidence for interaction between MORB-type asthenosphere and OIB-type components in the southern Neo-Tethys Ocean

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Saccani, Emilio; Allahyari, Khalil; Rahimzadeh, Bahman

2014-05-01

The Sarve-Abad (Sawlava) ophiolites crop out in the Main Zagros Thrust Zone and represent remnants of the Mesozoic southern Neo-Tethys Ocean that was located between the Arabian shield and Sanandaj-Sirjan continental block. They consist of several incomplete ophiolitic sequences including gabbroic bodies, a dyke complex, and pillow lava sequences. These rocks generally range from sub-alkaline to transitional character. Mineral chemistry and whole-rock geochemistry indicate that they have compositions akin to enriched-type mid-ocean ridge basalts (E-MORB) and plume-type MORB (P-MORB). Nonetheless, the different depletion degrees in heavy rare earth elements (HREE), which can be observed in both E-MORB like and P-MORB like rocks enable two main basic chemical types of rocks to be distinguished as Type-I and Type-II. Type-I rocks are strongly depleted in HREE (YbN 9.0). Petrogenetic modeling shows that Type-I rocks originated from 7 to 16% polybaric partial melting of a MORB-type mantle source, which was significantly enriched by plume-type components. These rocks resulted from the mixing of variable fractions of melts generated in garnet-facies and the spinel-facies mantle. In contrast, Type-II rocks originated from 5 to 8% partial melting in the spinel-facies of a MORB-type source, which was moderately enriched by plume-type components. A possible tectono-magmatic model for the generation of the southern Neo-Tethys oceanic crust implies that the continental rift and subsequent oceanic spreading were associated with uprising of MORB-type asthenospheric mantle featuring plume-type component influences decreasing from deep to shallow mantle levels. These deep plume-type components were most likely inherited from Carboniferous mantle plume activity that was associated with the opening of Paleo-Tethys in the same area.

Paleomagnetism of the Oman Ophiolite: New Results from Oman Drilling Project Cores

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Horst, A. J.; Till, J. L.; Koornneef, L.; Usui, Y.; Kim, H.; Morris, A.

2017-12-01

The Oman Drilling Project drilled holes at four sites in a transect through the southern massifs of the Samail ophiolite, and recovered 1500 m of igneous and metamorphic rocks. We focus on three sites from the oceanic crustal section including lower layered gabbros (GT1A), the mid-crustal layered to foliated gabbro transition (GT2A), and the shallower transition from sheeted dikes to varitextured gabbros (GT3A). Detailed core descriptions, analyses, and paleomagnetic measurements, were made on D/V Chikyu from July to September 2017 to utilize the core laboratory facilities similar to IODP expeditions. Shipboard measurements included anisotropy of magnetic susceptibility (AMS) and alternating field and thermal demagnetization of 597 discrete samples. Sample demagnetization behavior is varied from each of the cores, with some revealing multiple components of magnetization, and others yielding nearly univectorial data. The interpretation of results from the lower crustal cores is complicated by the pervasive presence of secondary magnetite. In almost all samples, a stable component was resolved (interpreted as a characteristic remanent magnetization) after removal of a lower-coercivity or lower unblocking-temperature component. The inclinations of the stable components in the core reference frame are very consistent in Hole GT1A. However, a transition from negative to positive inclinations in GT2A suggests some structural complexity, possibly as a result of intense late faulting activity. Both abrupt and gradual transitions between multiple zones of negative and positive inclinations occur in Hole GT3A. Interpretation and direct comparison of remanence between drill sites is difficult as recovered core pieces currently remain azimuthally unoriented, and GT2A was drilled at a plunge of 60°, whereas GT1A and GT3A were both drilled vertically. Work is ongoing to use borehole imagery to reorient the core pieces and paleomagnetic data into a geographic in situ reference

Structural Characterization of the Foliated-Layered Gabbro Transition in Wadi Tayin of the Samail Ophiolite, Oman; Oman Drilling Project Holes GT1A and GT2A

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Deans, J. R.; Crispini, L.; Cheadle, M. J.; Harris, M.; Kelemen, P. B.; Teagle, D. A. H.; Matter, J. M.; Takazawa, E.; Coggon, J. A.

2017-12-01

Oman Drilling Project Holes GT1A and GT2A were drilled into the Wadi Tayin massif, Samail ophiolite and both recovered ca. 400 m of continuous core through a section of the layered gabbros and the foliated-layered gabbro transition. Hole GT1A is cut by a discrete fault system including localized thin ultracataclastic fault zones. Hole GT2A is cut by a wider zone of brittle deformation and incipient brecciation. Here we report the structural history of the gabbros reflecting formation at the ridge to later obduction. Magmatic and high temperature history- 1) Both cores exhibit a pervasive, commonly well-defined magmatic foliation delineated by plagioclase, olivine and in places clinopyroxene. Minor magmatic deformation is present. 2) The dip of the magmatic foliation varies cyclically, gradually changing dip by 30o from gentle to moderate over a 50 m wavelength. 3) Layering is present throughout both cores, is defined by changes in mode and grain size ranging in thickness from 2 cm to 3 m and is commonly sub-parallel to the foliation. 4) There are no high temperature crystal-plastic shear zones in the core. Key observations include: no simple, systematic shallowing of dip with depth across the foliated-layered gabbro transition and layering is continuous across this transition. Cyclic variation of magmatic foliation dip most likely reflects the process of plate separation at the ridge axis. Near-axis faulting- i) On or near-axis structures consist of epidote-amphibole bearing hydraulic breccias and some zones of intense cataclasis with intensely deformed epidote and seams of clay and chlorite accompanied by syntectonic alteration of the wall rock. Early veins are filled with amphibole, chlorite, epidote, and anhydrite. ii) The deformation ranges from brittle-ductile, causing local deflection of the magmatic foliation, to brittle offset of the foliation and core and mantle structures in anhydrite veins. iii) The prevalent sense of shear is normal and slickenfibers

Syn- and Post-Accretionary Structures in the Neoproterozoic Central Allaqi-Heiani Suture Zone, Southeastern Egypt

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Abdeen, M. M.; Abdelghaffar, A. A.

2012-04-01

The Allaqi-Heiani suture (AHS) is the western part of the main Allaqi-Heiani-Gerf-Onib-Sol Hamed-Yanbu suture and represents one of the Neoproterozoic, arc-arc sutures in the Arabian-Nubian Shield (ANS). It separates the ca. 750 Ma South Eastern Desert terrane in the north from the ca. 830-720 Ma Gabgaba terrane in the south. The AHS is a deformed belt of ophiolitic rocks, syn-tectonic granitoids and metasediments. The central AHS zone is divided into three structural domains. The western domain (Ι) is characterized by NNE low thrusts and SSW-vergent folds. The central domain (ΙΙ) includes upright tight to isoclinal NNW-SSE oriented folds and transpressional faults. The eastern domain (ΙΙΙ) shows NNW-SSE oriented open folds. Structural analysis indicates that the area has a poly-phase deformation history involving at least two events. Event D1 was an N-S to NNE-SSW regional shortening generating the SSW-verging folds and the NNE dipping thrusts. Event D2 was an ENE-WSW shortening producing NNW-SSE oriented folds in the central and eastern parts of the study area and reactivating older thrusts with oblique-slip reverse fault movement. The tectonic evolution of the area involves two episodes of collision: an early collision between the South Eastern Desert terrane and the Gabgaba terrane along the AHS after the consumption of a basin floored by oceanic crust above a north-dipping subduction zone; and a later collision between East- and West-Gondwanas at ca. 750-650 Ma, leading to the closure of the Mozambique Ocean. This collision deformed the AHS along N-S trending shortening zones and produced NW-SE and NE-SW oriented sinistral and dextral transpressional faults, respectively. The early collision episode is related to the terrane accretion during the early Pan-African orogen, while the later phase is related to a late Pan-African or Najd orogen.

Lithological Classification Using Sentinel-2A Data in the Shibanjing Ophiolite Complex in Inner Mongolia, China

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Wenyan Ge

2018-04-01

Full Text Available As a source of data continuity between Landsat and SPOT, Sentinel-2 is an Earth observation mission developed by the European Space Agency (ESA, which acquires 13 bands in the visible and near-infrared (VNIR to shortwave infrared (SWIR range. In this study, a Sentinel-2A imager was utilized to assess its ability to perform lithological classification in the Shibanjing ophiolite complex in Inner Mongolia, China. Five conventional machine learning methods, including artificial neural network (ANN, k-nearest neighbor (k-NN, maximum likelihood classification (MLC, random forest classifier (RFC, and support vector machine (SVM, were compared in order to find an optimal classifier for lithological mapping. The experiment revealed that the MLC method offered the highest overall accuracy. After that, Sentinel-2A image was compared with common multispectral data ASTER and Landsat-8 OLI (operational land imager for lithological mapping using the MLC method. The comparison results showed that the Sentinel-2A imagery yielded a classification accuracy of 74.5%, which was 2.5% and 5.08% higher than those of the ASTER and OLI imagery, respectively, indicating that Sentinel-2A imagery is adequate for lithological discrimination, due to its high spectral resolution in the VNIR to SWIR range. Moreover, different data combinations of Sentinel-2A + ASTER + DEM (digital elevation model and OLI + ASTER + DEM data were tested on lithological mapping using the MLC method. The best mapping result was obtained from Sentinel-2A + ASTER + DEM dataset, demonstrating that OLI can be replaced by Sentinel-2A, which, when combined with ASTER, can achieve sufficient bandpasses for lithological classification.

Heavy Metal Resistant, Alkalitolerant Bacteria Isolated From Serpentinizing Springs in the Zambales Ophiolite, Philippines

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Vallalar, B.; Meyer-Dombard, D. R.; Cardace, D.; Arcilla, C. A.

2016-12-01

Serpentinization involves hydrologic alteration of ultramafic mantle rocks containing olivine and pyroxene to produce serpentine minerals. The fluids resulting from this reaction are reduced, extremely depleted in dissolved inorganic carbon, and are highly alkaline with pH values typically exceeding 10. Major byproducts of the serpentinizing reaction include iron oxides, hydrogen, methane, and small amounts of organic molecules that provide chemosynthetic energy for subsurface microbial communities. In addition, weathering of serpentine rocks often produces fluids and sediments that have elevated concentrations of various toxic heavy metals such as chromium, nickel, cobalt, copper, and zinc. Thus, microorganisms inhabiting these unique ecological niches must be adapted to a variety of physicochemical extremes. The purpose of this study is to isolate bacteria that are capable of withstanding extremely high concentrations of multiple heavy metals from serpentine fluid-associated sediments. Fluid and sediment samples for microbial culturing were collected from Manleluag Spring National Park located on the island of Luzon, Philippines. The area is part of the Zambales ophiolite range, and hosts several serpentinizing fluid seeps. Fluid emanating from the source pool of the spring, designated Manleluag 2 (ML2), has a pH of 10.83 and temperature of 34.4 °C. Luria-Bertani agar medium was supplemented with varying concentrations of five trace elements - Cu, Cr, Co, Ni, and Zn. Environmental samples were spread on each of these media and colony forming units were subsequently chosen for isolation. In all, over 20 isolates were obtained from media with concentrations ranging from 25 mg/L - 400 mg/L of each metal. Taxonomic identity of each isolate was determined using 16S rRNA gene sequences. The isolates were then tested for tolerance to alkaline conditions by altering LB medium to pH values of 8, 9, 10, 11, and 12. The majority of strains exhibit growth at the highest p

Jurassic-Paleogene intraoceanic magmatic evolution of the Ankara Mélange, north-central Anatolia, Turkey

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Sarifakioglu, E.; Dilek, Y.; Sevin, M.

2014-02-01

Oceanic rocks in the Ankara Mélange along the Izmir-Ankara-Erzincan suture zone (IAESZ) in north-central Anatolia include locally coherent ophiolite complexes (∼ 179 Ma and ∼ 80 Ma), seamount or oceanic plateau volcanic units with pelagic and reefal limestones (96.6 ± 1.8 Ma), metamorphic rocks with ages of 256.9 ± 8.0 Ma, 187.4 ± 3.7 Ma, 158.4 ± 4.2 Ma, and 83.5 ± 1.2 Ma indicating northern Tethys during the late Paleozoic through Cretaceous, and subalkaline to alkaline volcanic and plutonic rocks of an island arc origin (∼ 67-63 Ma). All but the arc rocks occur in a shale-graywacke and/or serpentinite matrix, and are deformed by south-vergent thrust faults and folds that developed in the middle to late Eocene due to continental collisions in the region. Ophiolitic volcanic rocks have mid-ocean ridge (MORB) and island arc tholeiite (IAT) affinities showing moderate to significant large ion lithophile elements (LILE) enrichment and depletion in Nb, Hf, Ti, Y and Yb, which indicate the influence of subduction-derived fluids in their melt evolution. Seamount/oceanic plateau basalts show ocean island basalt (OIB) affinities. The arc-related volcanic rocks, lamprophyric dikes and syenodioritic plutons exhibit high-K shoshonitic to medium- to high-K calc-alkaline compositions with strong enrichment in LILE, rare earth elements (REE) and Pb, and initial ɛNd values between +1.3 and +1.7. Subalkaline arc volcanic units occur in the northern part of the mélange, whereas the younger alkaline volcanic rocks and intrusions (lamprophyre dikes and syenodioritic plutons) in the southern part. The late Permian, Early to Late Jurassic, and Late Cretaceous amphibole-epidote schist, epidote-actinolite, epidote-chlorite and epidote-glaucophane schists represent the metamorphic units formed in a subduction channel in the northern Neotethys. The Middle to Upper Triassic neritic limestones spatially associated with the seamount volcanic rocks indicate that the northern

Anomalous hydrogen emissions from the San Andreas fault observed at the Cienega Winery, central California

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Sato, Motoaki; Sutton, A. J.; McGee, K. A.

1984-03-01

We began continuous monitoring of H2 concentration in soil along the San Andreas and Calaveras faults in central California in December 1980, using small H2/O2 fuel-cell sensors. Ten monitoring stations deployed to date have shown that anomalous H2 emissions take place occasionally in addition to diurnal changes. Among the ten sites, the Cienega Winery site has produced data that are characterized by very small diurnal changes, a stable baseline, and remarkably distinct spike-like H2 anomalies since its installation in July 1982. A major peak appeared on 1 10 November 1982, and another on 3 April 1983, and a medium peak on 1 November 1983. The occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site. In order to methodically assess how these peaks are related to earthquakes, three H2 degassing models were examined. A plausible correlational pattern was obtained by using a model that (1) adopts a hemicircular spreading pattern of H2 along an incipient fracture plane from the hypocenter of an earthquake, (2) relies on the FeO-H2O reaction for H2 generation, and (3) relates the accumulated amount of H2 to the mass of serpentinization of underlying ophiolitic rocks; the mass was tentatively assumed to be proportional to the seismic energy of the earthquake.

Metamorphic complexes in accretionary orogens: Insights from the Beishan collage, southern Central Asian Orogenic Belt

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Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Yang, Lei

2016-10-01

The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf(t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other

Geodynamic interpretation of the 40Ar/39Ar dating of ophiolitic and arc-related mafics and metamafics of the northern part of the Anadyr-Koryak region

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Palandzhyan, S.A.; Layer, P.W.; Patton, W.W.; Khanchuk, A.I.

2011-01-01

Isotope datings of amphibole-bearing mafics and metamafics in the northern part of the Anadyr-Koryak region allow clarification of the time of magmatic and metamorphic processes, which are synchronous with certain stages of the geodynamic development of the northwest segment of the Pacific mobile belt in the Phanerozoic. To define the 40Ar/39Ar age of amphiboles, eight samples of amphibole gabbroids and metamafics were selected during field work from five massifs representing ophiolites and mafic plutons of the island arc. Rocks from terranes of three foldbelts: 1) Pekulnei (Chukotka region), 2) Ust-Belaya (West Koryak region), and 3) the Tamvatnei and El'gevayam subterranes of the Mainits terrane (Koryak-Kamchatka region), were studied. The isotope investigations enabled us to divide the studied amphiboles into two groups varying in rock petrographic features. The first was represented by gabbroids of the Svetlorechensk massif of the Pekulnei Range and by ophiolites of the Tamvatnei Mts.; their magmatic amphiboles show the distribution of argon isotopes in the form of clearly distinguished plateau with an age ranging within 120-129 Ma. The second group includes metamorphic amphiboles of metagabbroids and apogabbro amphibolites of the Ust-Belaya Mts., Pekulnei and Kenkeren ranges (El'gevayam subterranes). Their age spectra show loss of argon and do not provide well defined plateaus the datings obtained for them are interpreted as minimum ages. Dates of amphiboles from the metagabbro of the upper tectonic plate of the Ust-Belaya allochthon points to metamorphism in the suprasubduction environment in the fragment of Late Neoproterozoic oceanic lithosphere in Middle-Late Devonian time, long before the Uda-Murgal island arc system was formed. The amphibolite metamorphism in the dunite-clinopyroxenite-metagabbro Pekulnei sequence was dated to occur at the Permian-Triassic boundary. The age of amphiboles from gabbrodiorites of the Kenkeren Range was dated to be Early

Characterizing the nature of melt-rock reaction in peridotites from the Santa Elena Ophiolite, NW Costa Rica

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Carr, D.; Loocke, M. P.; Snow, J. E.; Gazel, E.

2017-12-01

The Santa Elena Ophiolite (SEO), located on the northwestern coast of Costa Rica, consists primarily of preserved oceanic mantle and crustal rocks thrust above an accretionary complex. The SEO is predominantly characterized by mantle peridotites (i.e., primarily spinel lherzolite with minor amounts of harzburgite and dunite) cut and intruded by minor pegmatitic gabbros, layered gabbros, plagiogranites, and doleritic and basaltic dykes. Previous studies have concluded that the complex formed in a suprasubduction zone (SSZ) setting based on the geochemical nature of the layered gabbros and plagiogranites (i.e., depleted LREE and HFSE and enriched LILE and Pb), as well, as the peridotites (i.e., low-TiO2, Zr, and V, and high MgO, Cr, and Ni)(Denyer and Gazel, 2009). Eighteen ultramafic samples collected during the winter 2010/2011 field season (SECR11) exhibit abundant evidence for melt-rock reaction (e.g., disseminated plagioclase and plagioclase-spinel, clinopyroxene-spinel, and plagioclase-clinopyroxene symplectites) and provide a unique opportunity to characterize the textural and chemical nature of melt-rock reaction in the SEO. We present the results of a petrologic investigation (i.e., petrography and electron probe microanalysis) of 28 thin sections (19 spinel lherzolites, of which 14 are plagioclase-bearing, 4 pyroxenite veins, and 5 harzburgites) derived from the SECR11 sample set. The results of this investigation have the potential to better our understanding of the nature of melt generation and migration and melt-rock interaction in the SEO mantle section and shed further light on the complex petrogenetic history of the SEO. Denyer, P., Gazel, E., 2009, Journal of South American Earth Sciences, 28:429-442.

Subsurface geometry of the San Andreas-Calaveras fault junction: influence of serpentinite and the Coast Range Ophiolite

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Watt, Janet Tilden; Ponce, David A.; Graymer, Russell W.; Jachens, Robert C.; Simpson, Robert W.

2014-01-01

While an enormous amount of research has been focused on trying to understand the geologic history and neotectonics of the San Andreas-Calaveras fault (SAF-CF) junction, fundamental questions concerning fault geometry and mechanisms for slip transfer through the junction remain. We use potential-field, geologic, geodetic, and seismicity data to investigate the 3-D geologic framework of the SAF-CF junction and identify potential slip-transferring structures within the junction. Geophysical evidence suggests that the San Andreas and Calaveras fault zones dip away from each other within the northern portion of the junction, bounding a triangular-shaped wedge of crust in cross section. This wedge changes shape to the south as fault geometries change and fault activity shifts between fault strands, particularly along the Calaveras fault zone (CFZ). Potential-field modeling and relocated seismicity suggest that the Paicines and San Benito strands of the CFZ dip 65° to 70° NE and form the southwest boundary of a folded 1 to 3 km thick tabular body of Coast Range Ophiolite (CRO) within the Vallecitos syncline. We identify and characterize two steeply dipping, seismically active cross structures within the junction that are associated with serpentinite in the subsurface. The architecture of the SAF-CF junction presented in this study may help explain fault-normal motions currently observed in geodetic data and help constrain the seismic hazard. The abundance of serpentinite and related CRO in the subsurface is a significant discovery that not only helps constrain the geometry of structures but may also help explain fault behavior and the tectonic evolution of the SAF-CF junction.

Characterization of Serpentine Samples from the Coast Range Ophiolite Microbial Observatory with μ-FTIR and XRD. ­­

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Sousa, A.; Cardace, D.

2017-12-01

Serpentinizing systems hold much promise as potentially habitable environments in diverse planetary settings. They involve abundant and simple ingredients (i.e., the mineral olivine, liquid water), support subsurface microbial communities on Earth (Crespo-Medina et al. 2014; Suzuki et al. 2014; Kelley et al. 2005) and are thought to occur elsewhere in our solar system such as Mars (Schulte et al. 2006; Ehlmann et al. 2010)and possibly ocean worlds (Waite et al. 2017; Vance 2009). Although geochemical and microbial data collection continues in serpentinizing systems, the identification and resolution of potential biosignatures in serpentinites are not yet clear. Specifically, the micro-scale mineralogical contexts in which cell fragments or biofilm residues may be formed and preserved is lacking. Here we report preliminary transmission and reflection mode μ-FTIR spectral maps and XRD diffractograms, obtained with instruments relevant to robotic exploration missions (Blake et al. 2012; Igisu et al. 2009; Leroi et al. 2009). Samples analyzed include ultramafic rock and constituent mineral standards (e.g., olivine) and rocks collected from near surface sites associated with the NASA Astrobiology Institute-funded initiative, the Coast Range Ophiolite Microbial Observatory (CROMO), in Lower Lake, CA (Cardace et al. 2013). These new results provide co-registered, complementary data on astrobiologically important rock and mineral phases related to serpentinization (Crespo-Medina et al. 2014; Twing et al. 2017). Future work will leverage this data set in microbial colonization experiments aimed at parsing background organic loads in serpentinites from surficial/fracture-localized modern biofilm signatures.

Ophiolite Emplacement and the Effects of the Subduction of the Active Chile Ridge System: Heterogeneous Paleostress Regimes Recorded in the Taitao Ophiolite (Southern Chile Emplazamiento de ofiolitas y los efectos de la subducción de la dorsal activa de Chile: Regímenes heterogéneos de paleostress registrados en la Oflolita Taitao (Sur de Chile

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Eugenio E Veloso

2009-01-01

Full Text Available The repeated north and southward migration of the Chile Triple junction, offshore the Península de Taitao, is expected to have imposed contrasting stress fields in the forearc for the last 6 Ma because of changes in convergence direction and rate of subducting plates. NNW-SSE to E-W and minor NE-SW striking brittle faults developed in the plutonic units of the Mio-Pliocene Taitao Ophiolite, whereas NNE-SSW and minor NW-SE trending faults developed in its eastern border (Bahía Barrientes fault-zone. These brittle faults are studied to elucídate the style of ophiolite emplacement and the tectonic effects resulting from the alternated migration of the Chile Triple junction in the área. Analyses of heterogeneous fault-slip data on both áreas suggest that faults were activated by different stress fields. Two different compressional stress fields were identified in the plutomc units (A and B, whereas three different stress fields, ranging from compressional to strike-slip, were identified in the BahíaBarrientos fault-zone (C, D and E. Calculated directions of Oj axes for A, C, D and E solutions are mostly E-W trending, roughly similar to the convergence direction of subducting plates, whereas that for B solution is counterclockwise rotated ca. 60° with respect to the previous E-W trend. Brittle structures related to solution B were attributed to an early deformation of the ophiolite, most probably developed shortly after its emplacement {ca. 6 Ma. These structures were further counterclockwise rotated, while new structures (related to solution A developed in the plutomc units in order to absorb the continuous deformation. In the eastern margin of the ophiolite, the stress field divided inte compressional and strike-slip components. During periods of relatively strong compression (fast subduction of the Nazca píate, the fault-zone experienced well defined compressional and strike-slip movements (solutions C and D. In contrast, during periods of

Characterizing Dissolved Organic Matter and Metabolites in an Actively Serpentinizing Ophiolite Using Global Metabolomics Techniques

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Seyler, L. M.; Rempfert, K. R.; Kraus, E. A.; Spear, J. R.; Templeton, A. S.; Schrenk, M. O.

2017-12-01

Environmental metabolomics is an emerging approach used to study ecosystem properties. Through bioinformatic comparisons to metagenomic data sets, metabolomics can be used to study microbial adaptations and responses to varying environmental conditions. Since the techniques are highly parallel to organic geochemistry approaches, metabolomics can also provide insight into biogeochemical processes. These analyses are a reflection of metabolic potential and intersection with other organisms and environmental components. Here, we used an untargeted metabolomics approach to characterize dissolved organic carbon and aqueous metabolites from groundwater obtained from an actively serpentinizing habitat. Serpentinites are known to support microbial communities that feed off of the products of serpentinization (such as methane and H2 gas), while adapted to harsh environmental conditions such as high pH and low DIC availability. However, the biochemistry of microbial populations that inhabit these environments are understudied and are complicated by overlapping biotic and abiotic processes. The aim of this study was to identify potential sources of carbon in an environment that is depleted of soluble inorganic carbon, and to characterize the flow of metabolites and describe overlapping biogenic and abiogenic processes impacting carbon cycling in serpentinizing rocks. We applied untargeted metabolomics techniques to groundwater taken from a series of wells drilled into the Semail Ophiolite in Oman.. Samples were analyzed via quadrupole time-of-flight liquid chromatography tandem mass spectrometry (QToF-LC/MS/MS). Metabolomes and metagenomic data were imported into Progenesis QI software for statistical analysis and correlation, and metabolic networks constructed using the Genome-Linked Application for Metabolic Maps (GLAMM), a web interface tool. Further multivariate statistical analyses and quality control was performed using EZinfo. Pools of dissolved organic carbon could

Polymineralic inclusions in mantle chromitites from the Oman ophiolite indicate a highly magnesian parental melt

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Rollinson, Hugh; Mameri, Lucan; Barry, Tiffany

2018-06-01

Polymineralic inclusions interpreted as melt inclusions in chromite from the dunitic Moho Transition Zone in the Maqsad area of the Oman ophiolite have been analysed and compositions integrated using a rastering technique on the scanning electron microscope. The inclusions now comprise a range of inter-grown hydrous phases including pargasite, aspidolite, phlogopite and chlorite, indicating that the parental melts were hydrous. Average inclusion compositions for seven samples contain between 23.1 and 26.8 wt% MgO and 1.7-3.6 wt% FeO. Compositions were corrected to allow for the low FeO concentrations using coexisting olivine compositions. These suggest that the primary melt has between 20 and 22 wt% MgO and 7-9.7 wt% FeO and has an affinity with boninitic melts, although the melts have a higher Ti content than most boninites. Average rare earth element concentrations suggest that the melts were derived from a REE depleted mantle source although fluid-mobile trace elements indicate a more enriched source. Given the hydrous nature of the inclusions this enrichment could be fluid driven. An estimate of the melt temperature can be made from the results of homogenisation experiments on these inclusions and suggests 1300 °C, which implies for a harzburgite solidus, relatively shallow melting at depths of <50 km and is consistent with a boninitic origin. The current "basaltic" nature of the chromite host to highly magnesian melt inclusions suggests that the dunitic Moho Transition Zone operated as a reaction filter in which magnesian melts were transformed into basalts by the removal of high magnesian olivines, particularly in areas where the Moho Transition Zone is unusually thick. We propose therefore that podiform mantle chromitites, even those with an apparent MORB-like chemical signature, have crystallised from a highly magnesian parental melt. The data presented here strongly support the view that this took place in a subduction initiation setting.

Weathering and transport of chromium and nickel from serpentinite in the Coast Range ophiolite to the Sacramento Valley, California, USA

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Morrison, Jean M.; Goldhaber, Martin B.; Mills, Christopher T.; Breit, George N.; Hooper, Robert L.; Holloway, JoAnn M.; Diehl, Sharon F.; Ranville, James F.

2015-01-01

A soil geochemical study in northern California was done to investigate the role that weathering and transport play in the regional distribution and mobility of geogenic Cr and Ni, which are both potentially toxic and carcinogenic. These elements are enriched in ultramafic rocks (primarily serpentinite) and the soils derived from them (1700–10,000 mg Cr per kg soil and 1300–3900 mg Ni per kg soil) in the Coast Range ophiolite. Chromium and Ni have been transported eastward from the Coast Range into the western Sacramento Valley and as a result, valley soil is enriched in Cr (80–1420 mg kg−1) and Ni (65–224 mg kg−1) compared to median values of U.S. soils of 50 and 15 mg kg−1, respectively. Nickel in ultramafic source rocks and soils is present in serpentine minerals (lizardite, antigorite, and chrysotile) and is more easily weathered compared to Cr, which primarily resides in highly refractory chromite ([Mg,Fe2+][Cr3+,Al,Fe3+]2O4). Although the majority of Cr and Ni in soils are in refractory chromite and serpentine minerals, the etching and dissolution of these minerals, presence of Cr- and Ni-enriched clay minerals and development of nanocrystalline Fe (hydr)oxides is evidence that a significant fractions of these elements have been transferred to potentially more labile phases.

Active Microbial Sulfate Reduction in Serpentinization Fluids of the Semail Ophiolite in Oman

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Glombitza, C.; Rempfert, K. R.; Templeton, A. S.; Hoehler, T. M.

2017-12-01

Dissimilatory sulfate reduction (SR) is among the oldest known microbial processes on Earth. It is the predominant anaerobic microbial process in sulfur-rich marine sediments but it also occurs in subsurface lithoautotrophic ecosystems, where it is driven by radiolytically produced H2 and sulfate [1]. Serpentinization is a process by which H2 is generated in a reaction of water with peridotite rock. This abiotic generation of H2 suggests its potential to power life in rocks as a stand-alone process, independent of the photosynthetic biosphere, because the generated H2 is a key energy source for microbial metabolism. This is of particular interest in understanding the role of water-rock reactions in generating habitable conditions on and beyond Earth. Sulfate is plausibly available in several of the water-bearing environments now known beyond Earth, making SR a potentially important metabolism in those systems. Sulfate minerals are abundant on the surface of Mars [2], suggesting that Martian groundwaters may be sulfate-rich. Sulfate is also postulated to be a component of the oceans of Europa and Enceladus [3, 4]. The inferred presence of both sulfate and peridotite rocks in these environments points toward a potential niche for sulfate reducers and highlights the need to understand how and where SR occurs in serpentinizing systems on Earth. We incubated formation fluids sampled from in the Semail Ophiolite in Oman with a 35-S labelled sulfate tracer and determined the rates of in-situ microbial sulfate reduction. The selected fluids represent different environmental conditions, in particular varying substrate concentrations (sulfate, H2 and CH4) and pH (pH 8.4 to pH 11.2). We found active microbial SR at very low rates in almost all fluids, ranging from 2 fmol mL-1 d-1 to 2 pmol mL-1 d-2. Lowest rates were associated with the hyperalkaline fluids (pH > 10), that had also the lowest sulfate concentration (50-90 µmol L-1). In line with previously determined species

Compositional Variation of Chrome Spinels in the Ore-bearing Zones of the Kraka Ophiolite and the Chromitite Origin

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D. E. Saveliev

2017-07-01

Full Text Available The article considers a chemical variation of accessory and ore-forming chrome spinels from the Kraka ultramafic massif at the different scales, from the deposit to the thin section. A correlation analysis of compositional and structural features of ultramafic rocks and ores was performed. The ultramafic rocks and chromitites in the studied massif show the distinct deformation structures and tectonite olivine fabric. A typical chemical gap (i.e. Cr#=Cr/(Cr+Al was observed between peridotite, on the one hand, and dunite and chromitite, on the other hand, on the scale of deposits and ore-bearing zones. The location and size of this gap depend on the type of deposit. The gap becomes wider from the disseminated tabular bodies to the typical podiform ones. It has been found that in the thin initial dunite veinlets in peridotite the chrome spinels chemistry changes gradually and there is no Cr# gap between peridotite and dunite. The dunite venlets show a strong olivine fabric, which is an evidence of their high-temperature plastic flow origin. It has been revealed that new chrome spinel grains previously formed as rods or needles and then coarsened. We explained this observation as the result of impurity segregation, coalescence and spheroidization induced by the plastic deformation of olivine. It is inferred that a solid crystal flow is the main requirement for the dunite and chromitite body formation in the Kraka ophiolite massif. In the solid stream, the mineral phase separation takes place. For example, olivine and orthopyroxene grains of parental peridotite separate from one another, and weaker (more mobile olivine grains form dunite bodies in which chromitite appears as a result of impurity segregation.

Thermal Evolution of Juvenile Subduction Zones ' New Constraints from Lu-Hf Geochronology on HP oceanic rocks (Halilbaǧi, Central Anatolia)

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Pourteau, Amaury; Scherer, Erik; Schmidt, Alexander; Bast, Rebecca

2015-04-01

The thermal structure of subduction zones plays a key role on mechanical and chemical processes taking place along the slab-mantle interface. Until now, changes through time of this thermal structure have been explored mostly by the means of numerical simulations. However, both "warm" (i.e., epidote-bearing), and "cold" (i.e., lawsonite-bearing) HP oceanic rocks have been reported in some fossil subduction complexes exposed at the Earth's surface (e.g., Franciscan Complex, California; Rio San Juan Complex, Hispañola; Halilbağı Unit, Central Anatolia). These a-priori "incompatible" rocks witness different thermal stages of ancient subduction zones and their study might provide complementary constraints to numerical models. To decipher the meaning of these contrasting metamorphic rocks in the Halilbağı Unit, we are carrying out Lu-Hf geochronology on garnet (grt) and lws from a variety of HP oceanic rocks, as well as the metamorphic sole of the overlying ophiolite. We selected five samples that are representative of the variety of metamorphic evolutions (i.e. peak conditions and P-T paths) encountered in this area. Preliminary analyses yielded 110 Ma (grt-hbl isochron) for a sub-ophiolitic grt amphibolite; 92 Ma (grt-omp) for an eclogite with prograde and retrograde ep; 90 Ma (grt-omp) for an eclogitic metabasite with prograde ep and retrograde ep+lws; 87 Ma (grt-gln) for a lws eclogite with prograde ep; and 86 Ma (grt-gln) for a blueschist with prograde and retrograde lws. These ages are mainly two-point isochrons. Further-refined data will be presented at the EGU General Assembly 2015, in Vienna. The consistent younging trend from "warm" to "cold" metamorphic rocks revealed by these first-order results points to metamorphic-sole formation during the initiation of intra-oceanic subduction at ~110 Ma, and subsequent cooling of the slab-mantle interface between 92 and 86 Ma. Therefore, the contrasting metamorphic evolutions encountered in the Halilbağı Unit

Suprasubduction volcanic rocks of the Char ophiolite belt, East Kazakhstan: new geochemical and first geochronological data

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Safonova, Inna; Simonov, Vladimir; Seltmann, Reimar; Yamamoto, Shinji; Xiao, Wenjiao

2016-04-01

The Char ophiolite belt is located in the western Central Asian Orogenic Belt, a world largest accretionary orogen, which has evolved during more than 800 Ma. The Char belt formed during Kazakhstan - Siberia collision. It has been known for hosting fragments of Late Devonian-Early Carboniferous oceanic crust, MORB, OPB and OIB, of the Paleo-Asian Ocean (Safonova et al., 2012). The Char is surrounded by two Paleozoic island-arc terranes: Zharma-Saur in the west and Rudny Altai in the east, however, until recent times, no island-arc units have been found within it. We were the first to find island-arc units as tectonic sheets occurring adjacent to those consisting of oceanic rocks. In places, island-arc andesites cut oceanic basalts. The Char volcanic and subvolcanic rocks of a probable suprasubduction origin are basalt, microgabbro, dolerite, andesite, tonalite and dacite. The mafic to andesitic volcanics possessing low TiO2 (0.85 wt.%av.) and show MgO vs. major elements crystallization trends suggesting two magma series: tholeiitic and calc-alkaline. The tholeiitic varieties are less enriched in incompatible elements then the calc-alkaline ones. Two samples are high-Mg and low-Ti andesibasalts similar to boninites. The rocks possess moderately LREE enriched rare-earth element patterns and are characterized by negative Nb anomalies present on the multi-element spectra (Nb/Lapm = 0.14-0.47; Nb/Thpm = 0.7-1.6).The distribution of rare-earth elements (La/Smn = 0.8-2.3, Gd/Ybn = 0.7-1.9) and the results of geochemical modeling in the Nb-Yb system suggest high degrees of melting of a depleted harzburgite-bearing mantle source at spinel facies depths. Fractional crystallization of clinopyroxene, plagioclase and opaque minerals also affected the final composition of the volcanic rocks. Clinopyroxene monomineral thermometry indicates crystallization of melts at 1020-1180°C. Melt inclusion composition based numerical calculations show that primary melts were derived at 1350

Retrodeforming the Sivas Basin (Turkey): Structural style of the central Anatolian basins and their integration in the geodynamic framework of Eastern Anatolia

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Legeay, Etienne; Ringenbach, Jean-Claude; Callot, Jean-Paul; Mohn, Geoffroy; Kavak, Kaan

2017-04-01

Anatolia is the result of the amalgamation of Gondwandian microcontinents against Eurasia active margin. These were originally separated by several Neotethyan oceanic domains consumed by north-dipping subductions. Prior to the continental collision, regional convergence resulted in an obduction event, from north to south in Campanian time, which led to the emplacement of ophiolite nappes and ophiolitic mélanges onto the Tauride passive margin. Several sedimentary basins subsequently developed above the former sutures zones recorded the long-lasting geological evolution of the Anatolian domain from Late Cretaceous to Present The Sivas Basin is all together the richest, the most studied and also most complex of the group of Tertiary basins. The Sivas Basin formed above the northern leading edge of the Tauride platform, the Kırşehir micro-continent, the edge of the Pontide arc and the related sutures. Its complex structure is that of a fold-and-thrust belt with syn-orogenic salt tectonics. After the obduction, the Sivas basin recorded a relative quiet tectonic phase from Maastrichtian to Paleocene with basinal pelagic sedimentation and carbonate platform emplacement on its southern edge. Then shortening resumed in the Early Eocene with the development of north-verging thrusts. It is recorded by a coarse clastic input, with conglomeratic deltas fans grading up to basinal turbidites until the Late Eocene. Then the basin is progressively isolated and becomes an isolated foreland in which a thick evaporite formation deposited. Oligocene to Miocene continental clastics deposition was then mainly controlled by halokinesis: minibasin, salt ridges and salt sheets development. A first canopy is attributed to the second pulse of contraction from Late-Oligocene to Middle Miocene. This second stage end with the formation of back-thrust within the Sivas Basin and southward as a passive roof above a pre-salt triangle zone. This study relies both on extensive fieldwork (4 Ph

Feature level fusion for enhanced geological mapping of ophiolile complex using ASTER and Landsat TM data

International Nuclear Information System (INIS)

Pournamdari, M; Hashim, M

2014-01-01

Chromite ore deposit occurrence is related to ophiolite complexes as a part of the oceanic crust and provides a good opportunity for lithological mapping using remote sensing data. The main contribution of this paper is a novel approaches to discriminate different rock units associated with ophiolite complex using the Feature Level Fusion technique on ASTER and Landsat TM satellite data at regional scale. In addition this study has applied spectral transform approaches, consisting of Spectral Angle Mapper (SAM) to distinguish the concentration of high-potential areas of chromite and also for determining the boundary between different rock units. Results indicated both approaches show superior outputs compared to other methods and can produce a geological map for ophiolite complex rock units in the arid and the semi-arid region. The novel technique including feature level fusion and Spectral Angle Mapper (SAM) discriminated ophiolitic rock units and produced detailed geological maps of the study area. As a case study, Sikhoran ophiolite complex located in SE, Iran has been selected for image processing techniques. In conclusion, a suitable approach for lithological mapping of ophiolite complexes is demonstrated, this technique contributes meaningfully towards economic geology in terms of identifying new prospects

Evaluation of Cr in ophiolite and groundwater and its potential to contaminate the environment in SE of Birjand

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Zahra Khaledi

2012-10-01

Full Text Available The presence of Cr(VI in groundwater resources is governed by pH and Eh of water and its compounds are generally soluble and have more toxicicity and mobility in oxidizing environments. In this article, the Cr concentration in ophiolite units, in sediments, and in groundwater resources, and also its potential to contaminate the environment have been investigated in southeast of Birjand. During sampling, 17 water samples (2 rain water samples and 15 groundwater samples, and 8 sediment samples were collected. The concentrations of cations (major cations and Cr and anions in water samples were measured at Ottawa University, Canada using IC and ICP-AES methods, respectively. Cr concentrations of sediments were measured using XRF, and concentrations of Cr in collected Selective Sequential Extraction (SSE fractions were measured using Atomic Absorption (AA at Ferdowsi University of Mashhad, Iran. The average Cr concentrations in sediments and water resources are 627 and 0.026 ppm, respectively. According to the pH of sediments and Eh-pH of water samples, the Cr in water resources is as Cr(VI. Furthermore, the results of SSE show that the majority of Cr was found with residual matter, attached to the iron and manganese oxides, bound to carbonates, organic matter, and the soluble fractions, respectively. The hydrogeochemical properties of water resources show that the average values of EC, TDS and pH are 509 mg/l, 1045 µs/cm and 8.1, respectively, and the concentrations of Cl-, Na+, Mg2+ and SO42- ions are higher than the levels of WHO and Iran National Standard (1053. According to the WQI classification, while 20 percent of the water resources have excellent quality, 53 percent show good quality and 20 percent of water resources are poor in quality.

Origin of the Luobusa diamond-bearing peridotites from the sub-arc mantle

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Liu, Chuanzhou; Zhang, Chang; Wu, Fuyuang; Chung, Sunlin

2016-04-01

Ophiolites are the remnants of ancient oceanic lithosphere that were emplaced onto continental margins. Ophiolites along the E-W trending Yarlung-Tsangpo Suture (YTS), which separates the Indian plate from the Eurasian plate, have been regarded as relics of the Neo-Tethys Ocean. The Luobusa ophiolite outcrops at the eastern YTS and mainly consists of harzburgites and dunites that have been intruded by gabbroic/diabase dykes at ca 130 Ma (Zhang et al., 2015). Basaltic lavas are rarely outcropped, and volumetrically minor (C., Liu, C. Z., Wu, F. Y., Zhang, L. L. & Ji, W. Q. Geochemistry and geochronology of maifc rocks from the Luobusa ophiolite, South Tibet. Lithos, 10.1016/j.lithos.2015.1006.1031 (2015). Zhou, M. F., Robinson, P. T., Malpas, J. & Li, Z. J. Podiform chromitites in the Luobusa Ophiolite (Southern Tibet): Implications for melt-rock interaction and chromite segregation in the upper mantle. J. Petrol. 37, 3-21 (1996).

The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

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Inglis, Edward C.; Debret, Baptiste; Burton, Kevin W.; Millet, Marc-Alban; Pons, Marie-Laure; Dale, Christopher W.; Bouilhol, Pierre; Cooper, Matthew; Nowell, Geoff M.; McCoy-West, Alex J.; Williams, Helen M.

2017-07-01

Arc lavas display elevated Fe3+/ΣFe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt-Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone P-T conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S-bearing and C-bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of δ56Fe of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.

The Correlation Between Porosity, Density and Degree of Serpentinization in Ophiolites from Point Sal, California: Implications for Strength of Oceanic Lithosphere

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Karrasch, A. K.; Farough, A.; Lowell, R. P.

2017-12-01

Hydration and serpentinization of oceanic lithosphere influences its strength and behavior under stress. Serpentine content is the limiting factor in deformation and the correlation between crustal strength and the degree of serpentinization is not linear. Escartin et al., [2001] shows that the presence of only 10% serpentine results in a nominally non-dilatant mode of brittle deformation and reduces the strength of peridotites dramatically. In this study, we measured density and porosity of ophiolite samples from Point Sal, CA that had various degrees of serpentinization. The densities ranged between 2500- 3000 kg/m3 and porosities ranged between 2.1-4.8%. The degree of serpentinization was estimated from mineralogical analysis, and these data were combined with that of 4 other samples analyzed by Farough et al., [2016], which were obtained from various localities. The degree of serpentinization varied between 0.6 and 40%. We found that degree of serpentinization was inversely correlated with density with a slope of 7.25 (kg/m3)/%. Using Horen et al., [1996] models, estimated P-wave velocity of the samples ranged between 6.75-7.90 km/s and S-wave velocity ranged between 3.58-4.35 km/s. There were no distinguishable difference in the results between olivine-rich or pyroxene-rich samples. These results, along with correlations to strength and deformation style, can be used as a reference for mechanical properties of the crust at depth, analysis of deep drill cores and to estimate the rate of weakening of the oceanic crust after the onset of serpentinization reactions.

Accretionary and collisional orogenesis in the south domain of the western Central Asian Orogenic Belt (CAOB)

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Cai, Keda; Long, Xiaoping; Chen, Huayong; Sun, Min; Xiao, Wenjiao

2018-03-01

The Central Asian Orogenic Belt (CAOB) was the result of long-lived multi-stage tectonic evolution, including Proterozoic to Paleozoic accretion and collision, Mesozoic intracontinental modification, and Cenozoic rapid deformation and uplift. The accretionary and collisional orogenesis of its early history generated a huge orogenic collage consisting of diverse tectonic units including island arcs, ophiolites, accretionary prisms, seamounts, oceanic plateaus and micro-continents. These incorporated orogenic components preserved valuable detailed information on orogenic process and continental crust growth, which make the CAOB a key region to understanding of continental evolution, mantle-crust interaction and associated mineralization. The western CAOB refers to the west region in North Xinjiang of China and circum-Balkash of Kazakhstan, with occurrences of the spectacular Kazakhstan orocline and its surrounding mountain belts. Because orogenic fabrics of this part mostly preserve their original features caused by the interactions among the southern Siberian active margin in the north and the Tarim Craton in the south, the western CAOB can be regarded as an ideal region to study the processes of the accretionary and collisional orogenesis and associated mineralization. Since a large number of researchers have been working on this region, research advances bloom strikingly in a short-time period. Therefore, we, in this special issue, focus on these new study advances on the south domain of the western CAOB, including the Kazakhstan collage system, Tianshan orogenic belt and Beishan region, and it is anticipated that this issue can draw more attention from the international research groups to be interested in the studies on orogenesis of the CAOB.

Overview of Hole GT2A: Drilling middle gabbro in Wadi Tayin massif, Oman ophiolite

Science.gov (United States)

Takazawa, E.; Kelemen, P. B.; Teagle, D. A. H.; Coggon, J. A.; Harris, M.; Matter, J. M.; Michibayashi, K.

2017-12-01

Hole GT2A (UTM: 40Q 655960.7E / 2529193.5N) was drilled by the Oman Drilling Project (OmDP) into Wadi Gideah of Wadi Tayin massif in the Samail ophiolite, Oman. OmDP is an international collaboration supported by the International Continental Scientific Drilling Program, the Deep Carbon Observatory, NSF, IODP, JAMSTEC, and the European, Japanese, German and Swiss Science Foundations, with in-kind support in Oman from the Ministry of Regional Municipalities and Water Resources, Public Authority of Mining, Sultan Qaboos University, and the German University of Technology. Hole GT2A was diamond cored in 25 Dec 2016 to 18 Jan 2017 to a total depth of 406.77 m. The outer surfaces of the cores were imaged and described on site before being curated, boxed and shipped to the IODP drill ship Chikyu, where they underwent comprehensive visual and instrumental analysis. 33 shipboard scientists were divided into six teams (Igneous, Alteration, Structural, Geochem, Physical Properties, Paleomag) to describe and analyze the cores. Hole GT2A drilled through the transition between foliated and layered gabbro. The transition zone occurs between 50 and 150 m curation corrected depth (CCD). The top 50 m of Hole GT2A is foliated gabbro whereas the bottom 250 m consists of layered gabbro. Brittle fracture is observed throughout the core. Intensity of alteration vein decreases from the top to the bottom of the hole. On the basis of changes in grain size and/or modal abundance and/or appearance/disappearance of igneous primary mineral(s) five lithological units are defined in Hole GT2A (Unit I to V). The uppermost part of Hole GT2A (Unit I) is dominated by fine-grained granular olivine gabbro intercalated with less dominant medium-grained granular olivine gabbro and rare coarse-grained varitextured gabbro. The lower part of the Hole (Units II, III and V) is dominated by medium-grained olivine gabbro, olivine melagabbro and olivine-bearing gabbro. Modally-graded rhythmic layering with

Basalts and picrites from a plume-type ophiolite in the South Qilian Accretionary Belt, Qilian Orogen: Accretion of a Cambrian Oceanic Plateau?

Science.gov (United States)

Zhang, Yuqi; Song, Shuguang; Yang, Liming; Su, Li; Niu, Yaoling; Allen, Mark B.; Xu, Xin

2017-05-01

Oceanic plateaus with high-Mg rocks in the present-day oceanic crust have attracted much attention for their proposed mantle-plume origins and abnormally high mantle potential temperatures (Tp). However, equivalent rocks in ancient oceanic environments are usually poorly preserved because of deformation and metamorphism. Here we present petrological, geochronological and geochemical data for pillow lavas from Cambrian ophiolites in the Lajishan and Yongjing regions of the South Qilian Accretionary Belt (SQAB), from the southern part of the Qilian Orogen, northern China. Three rock groups can be identified geochemically: (1) sub-alkaline basalts with enriched mid- ocean ridge basalt (E-MORB) affinity; (2) alkaline basalts with oceanic island basalt (OIB) features, probably derived from partial melting of an enriched mantle source; and (3) picrites with MgO (18-22 wt%). Cr-numbers [Cr# = Cr/(Cr + Al)] of spinels from the picrites suggest 18-21% degree of partial melting at the estimated mantle potential temperature (Tp) of 1489-1600 °C, equivalent to values of Cenozoic Hawaiian picrites (1500-1600 °C). Zircons from one gabbro sample yielded a U-Pb Concordia age of 525 ± 3 Ma, suggesting the oceanic crust formed in the Cambrian. Available evidence suggests that Cambrian mantle plume activity is preserved in the South Qilian Accretionary Belt, and influenced the regional tectonics: "jamming" of the trench by thick oceanic crust explains the emplacement and preservation of the oceanic plateau, and gave rise to the generation of concomitant Ordovician inner-oceanic island arc basalts via re-organisation of the subduction zones in the region.

TERRAIN TECTONICS OF THE CENTRAL ASIAN FOLDED BELT

Directory of Open Access Journals (Sweden)

M. M. Buslov

2014-01-01

-Baikal continent. The base of the Kazakhstan-Baikal continent was formed in the Vend-Cambrian due to subduction of the oceanic crust of the Paleo-Asian Ocean, including the Precambrian microcontinents and terrains of the Gondvana group, underneath the south-eastern margin of the Siberian continent (in the current coordinates. Due to subduction followed by collision of the microcontinents with the Kazakhstan-Tuva-Mongolia island arc, the crust had consolidated, and a complex continent was formed. Another major plate is the plate of the Paleo-Pacific Ocean. It is characterized by the long-term tectono-magmatic evolution without any involvement of the continental crust and by complex processes of the formation of the continental margins. Its evolution resulted in the formation of the Vend-Paleozoic continental margin complexes of the western segment of the Siberian continent which comprise the Vend-Cambrian Kuznetsk-Altai island arc and a complex of rocks of the Ordovic-Early Devonian passive margin and the Devon-Early Carbonic active margin. In the accretional wedges of the Kuznetsk-Altai island arc, abundant are only fragments of the Vend-Early Cambrian oceanic crust including ophiolites and paleo-oceanic uplifts. The contemporary analogue of the Central Asian folded belt is the south-eastern margin of Asia, represented by the junction area of the Indo-Australian and Pacific plates.  

Centralized vs. de-centralized multinationals and taxes

OpenAIRE

Nielsen, Søren Bo; Raimondos-Møller, Pascalis; Schjelderup, Guttorm

2005-01-01

The paper examines how country tax differences affect a multinational enterprise's choice to centralize or de-centralize its decision structure. Within a simple model that emphasizes the multiple conflicting roles of transfer prices in MNEs – here, as a strategic pre-commitment device and a tax manipulation instrument –, we show that (de-)centralized decisions are more profitable when tax differentials are (small) large. Keywords: Centralized vs. de-centralized decisions, taxes, MNEs. ...

Source-to-sink constraints on tectonic and sedimentary evolution of the western Central Range and Cenderawasih Bay (Indonesia)

Science.gov (United States)

Babault, Julien; Viaplana-Muzas, Marc; Legrand, Xavier; Van Den Driessche, Jean; González-Quijano, Manuel; Mudd, Simon M.

2018-05-01

The island of New Guinea is the result of continent-arc collision that began building the island's Central Range during the late Miocene. Recent studies have shown that rapid subduction, uplift and exhumation events took place in response to rapid, oblique convergence between the Pacific and the Australian plates. The tectonic and sedimentary evolution of Cenderawasih Bay, in the northwestern part of the New Guinea Island is still poorly understood: this bay links a major structural block, the Kepala Burung block, to the island's Central Ranges. Previous studies have shown that Cenderawasih Bay contains a thick (>8 km) sequence of undated sediments. One hypothesis claims that the embayment resulted from a 3 Ma opening created by anticlockwise rotation of the Kepala Burung block with respect to the northern rim of the Australian plate. Alternatively, the current configuration of Cenderawasih Bay could have resulted from the southwest drift of a slice of volcanics and oceanic crust between 8 and 6 Ma. We test these hypotheses using (i) a geomorphologic analysis of the drainage network dynamics, (ii) a reassessment of available thermochronological data, and (iii) seismic lines interpretation. We suggest that sediments started to accumulate in Cenderawasih Bay and onshore in the Waipoga Basin in the late Miocene since the inception of growth of the Central Range, beginning at 12 Ma, resulting in sediment accumulation of up to 12,200 m. This evidence is more consistent with the second hypothesis, and the volume of sediment accumulated means it is unlikely that the embayment was the result of recent (2-3 Ma) rotation of structural blocks. At first order, we predict that infilling is mainly composed of siliciclastics sourced in the graphite-bearing Ruffaer Metamorphic Belt and its equivalent in the Weyland Overthrust. Ophiolites, volcanic arc rocks and diorites contribute minor proportions. From the unroofing paths in the Central Range we deduce two rates of solid phase

Fragments of deeper parts of the hanging wall mantle preserved as orogenic peridotites in the central belt of the Seve Nappe Complex, Sweden

Science.gov (United States)

Clos, Frediano; Gilio, Mattia; van Roermund, Herman L. M.

2014-04-01

Formation conditions of olivine microstructures are investigated in the Kittelfjäll spinel peridotite (KSP), a fragment of lithospheric mantle which occurs as an isolated body within high grade metamorphic crustal rocks of the Seve Nappe Complex (SNC), southern Västerbotten, central Sweden. The KSP is an orogenic peridotite containing a well developed penetrative compositional layering, defined by highly depleted dunite with olivine Mg# (100 × Mg/Mg + Fe) of 92.0-93.5 and harzburgite with lower Mg# (91.0-92.5). Dunite is characterized by three contrasting olivine microstructures formed in response to different tectonometamorphic events: Coarse-grained, highly strained olivine porphyroclasts (M1) up to 20 cm long are surrounded by dynamically recrystallized olivine grains (M2) defining a characteristic olivine "foam" microstructure (grain size: 200-2000 μm). An olivine "mortar" (M3) microstructure (10-50 μm) forms a penetrative fabric element only in strongly localized, cm-to-m sized shear zones that crosscut earlier structures/foliations. Olivine fabric analysis in synergy, with mineralogical and chemical analyses, reveals that the KSP body represents old, possibly Archean, sub-continental lithospheric mantle that was crustally emplaced into the Caledonian tectonic edifice from the hanging wall mantle during exhumation of the subducted Seve Nappe Complex (Jämtlandian orogeny ~ 454 Ma). Olivine porphyroclasts (M1) grew at high temperature during dominant isobaric cooling after extensive polybaric melt extraction (> 40%) and subsequent refertilization. The onset of the early Caledonian deformation is interpreted to be related to the crustal emplacement of the KSP during eduction of the SNC. This phase is characterized by the development of the olivine M2 foam microstructure, formed at 650-830 °C/1-2 GPa by dislocation creep processes producing an E-type CPO's by the operation of the [100](001) and subordinate [001](100) slip systems with operating flow stress

Geochemical characteristics of mafic and ultramafic rocks from the Naga Hills Ophiolite, India: Implications for petrogenesis

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Ajoy Dey

2018-03-01

Full Text Available The Naga Hills Ophiolite (NHO represents one of the fragments of Tethyan oceanic crust in the Himalayan Orogenic system which is exposed in the Phek and Kiphire districts of Nagaland, India. The NHO is composed of partially serpentinized dunite, peridotite, gabbro, basalt, minor plagiogranite, diorite dyke and marine sediments. The basalts are mainly composed of fine grained plagioclase feldspar, clinopyroxene and orthopyroxene and show quenching and variolitic textures. The gabbros are characterized by medium to coarse grained plagioclase, orthopyroxene and clinopyroxene with ophitic to sub-ophitic textures. The ultramafic cumulates are represented by olivine, Cpx and Opx. Geochemically, the basalts and gabbros are sub-alkaline to alkaline and show tholeiitic features. The basalts are characterized by 44.1–45.6 wt.% of SiO2 with 28–38 of Mg#, and the gabbros by 38.7–43.7 wt.% of SiO2, and 26–79 of Mg#. The ultramafic rocks are characterized by 37.4–52.2 wt.% of SiO2, and 80–88 of Mg#. In multi-element diagrams (spidergrams both basalts and gabbros show fractionated trends with strong negative anomalies of Zr, Nb, Sr and a gentle negative anomaly of P. However, the rare earth element (REE plots of the basalts and gabbros show two distinct patterns. The first pattern, represented by light REE (LREE depletion, suggests N-MORB features and can be interpreted as a signature of Paleo-Tethyan oceanic crust. The second pattern, represented by LREE enrichment with negligible negative Eu anomaly, conforms to E-MORB, and may be related to an arc tectonic setting. In V vs. Ti/1000, Cr vs. Y and AFM diagrams, the basalts and gabbros plot within Island Arc Tholeiite (IAT and MORB fields suggesting both ridge and arc related settings. The ultramafic rocks exhibit two distinct patterns both in spidergrams and in REE plots. In the spidergram, one group displays highly enriched pattern, whereas the other group shows near flat pattern compared

Radioactivity of heavy minerals and geochemistry of trace elements and radon, resulting from the weathering of the ophiolitic complex, Northwest of Syria

International Nuclear Information System (INIS)

Kattaa, B.; Al-Hilal, M.; Jubeli, Y.

1999-06-01

Geochemical and radiometric survey of stream sediments resulting from the weathering of ophiolitic complex at Al-Basit area were carried out. Several exploration techniques have been used to evaluate the radioactive elements and minerals in the area, and to estimate the significance of the radioactivity of the source rocks of these elements and minerals. determination of radioelements and some trace elements in stream sediments, in addition to gamma-ray spectrometry and radon gas measurement in water of springs and wells were carried out in the study area. The results show that the high values of radioactive elements and radon concentration are related to the occurrence of syenite nepheline and plageogranite, characterized by higher content of these elements compared to mafic and ultramafic rocks. Mineralogical study of the heavy minerals shows that the abundant minerals are pyroxene and amphibole, while less abundant minerals are iron oxides (limonite and hematite), chromite, ilmenite, olivine and magnetite. Rare minerals are zircon, apatite, barite, tourmaline and sphen. The absence of monazite, xenotime and thorite in the collected samples is mainly attributed to the very limited occurrence of their source rocks. However, this results is rather restricted to the collected samples. High concentration of magnetite and ilmenite in some samples was noted, in addition to the presence of mineral called galaxite which was not reported previously. Gold flake was also found in one of the samples. The study of grain morphology suggests that the heavy minerals were transported for short distance from their source rocks. Grain size analyse of heavy minerals reveals that the concentration of economic minerals such as chromite and ilmenite increases with the decrease of the grain size. (author)

Probing the Cypriot Lithosphere: Insights from Broadband Seismology

Science.gov (United States)

Ogden, C. S.; Bastow, I. D.; Pilidou, S.; Dimitriadis, I.; Iosif, P.; Constantinou, C.; Kounoudis, R.

2017-12-01

Cyprus, an island in the eastern Mediterranean Sea, is an ideal study locale for understanding both the final stages of subduction, and the internal structure of so-called `ophiolites' - rare, on-land exposures of oceanic crust. The Troodos ophiolite offers an excellent opportunity to interrogate a complete ophiolite sequence from mantle rocks to pillow lavas. However, determining its internal architecture, and that of the subducting African plate deep below it, cannot be easily achieved using traditional field geology. To address this issue, we have built a new network of five broadband seismograph stations across the island. These, along with existing permanent stations, record both local and teleseismic earthquakes that we are now using to image Cyprus' crust and mantle seismic structure. Receiver functions are time series, computed from three-component seismograms, which contain information about lithospheric seismic discontinuities. When a P-wave strikes a velocity discontinuity such as the Moho, energy is converted to S-waves (direct Ps phase). The widely-used H-K Stacking technique utilises this arrival, and subsequent crustal reverberations (PpPs and PsPs+PpSs), to calculate crustal thickness (H) and bulk-crustal Vp/Vs ratio (K). Central to the method is the assumption that the Moho produces the largest amplitude conversions, after the direct P-arrival, which is valid where the Moho is sharp. Where the Moho is gradational or upper crustal discontinuities are present, the Moho signals are weakened and masked by shallow crustal conversions, potentially rendering the H-K stacking method unreliable. Using a combination of synthetic and observed seismograms, we explore Cyprus' crustal structure and, specifically, the reliability of the H-K method in constraining it. Data quality is excellent across the island, but the receiver function Ps phase amplitude is low, and crustal reverberations are almost non-existent. Therefore, a simple, abrupt wavespeed jump at the

Troodos: a giant serpentinite diapir

NARCIS (Netherlands)

Schuiling, R.D.

2011-01-01

Troodos is a classical ophiolite complex. It is proposed that the serpentinized harzburgites that now form the top of the mountain and represent the originally lowest part of the ophiolite sequence rose as a diapir. This diapiric rise is caused by the pervasive serpentinization of a suboceanic

The ophiolite of the Eohellenic nappe in the island of Skyros, Greece: Geotectonic environment of formation and metamorphic conditions inferred by mineralogical and geochemical data

Science.gov (United States)

Karkalis, Christos; Magganas, Andreas; Koutsovitis, Petros

2014-05-01

The island of Skyros is located in the Sporades-Aegean region. It includes an ophiolitic mélange sequence consisting of serpentinites, gabbroic and doleritic rocks, and also lavas which mostly appear in massive form, but in rare cases as deformed pillows. The ophiolitic mélange sequence also includes rodingites, ophicalcites, as well as radiolarites. This formation belongs to the Eohellenic tectonic nappe, which encompasses marbles, sandstones and schists and was emplaced onto the Pelagonian Zone during Early Cretaceous [1, 2]. Serpentinites were most likely formed after serpentinization of harzburgitic protoliths and consist of serpentine, bastite, spinel and magnetite. The chemistry of spinels (TiO2=0.14-0.25 wt.%, Al2O3=35.1-35.21 wt.%, Cr#=37.38-38.87), shows that the harzburgitic protoliths plausibly resemble back-arc basin peridotites [3]. Gabbros and dolerites present mostly subophitic textures, between the hornblende/clinopyroxene and plagioclase grains. Based upon their petrography and on their mineral chemistry hornblendes have been distinguished into magmatic and metamorphic hornblendes, with the first occurring mostly in gabbroic rocks. Magmatic hornblendes exhibit relatively high TiO2 (1.42-1.62 wt.%), Al2O3 (5.11-5.86 wt.%) and Na2O (1.01-1.09 wt.%) contents, with their presence implying that the magma was at least to some degree hydrous. Lavas are tholeiitic basalts with relatively high FeOt≡12 wt.% and low K2O and Th contents, consisting mostly albite, altered clinopyroxene and devitrified glass. Tectonomagmatic discrimination diagrams [4, 5] illustrate that the studied gabbros and lavas of Skyros are most likely associated with SSZ processes. Gabbroic rocks, subvolcanic dolerites and lavas have been subjected to greenschist/subgreenschist metamorphic processes, as confirmed by the presence of secondary amphiboles (metamorphic hornblende, actinolite/tremolite), epidote, pumpellyite and chlorite in all of the studied samples. On the other hand

Compositional diversity in peridotites as result of a multi-process history: The Pacific-derived Santa Elena ophiolite, northwest Costa Rica

Science.gov (United States)

Escuder-Viruete, Javier; Baumgartner, Peter O.; Castillo-Carrión, Mercedes

2015-08-01

The Santa Elena ophiolite (SEO) is an ultramafic nappe of more than 270 km2 overlying a tectonic serpentinite-matrix mélange in northwest Costa Rica. It is mainly composed of Cpx-rich and Cpx-poor harzburgites (~ 2.5 km-thick), with minor lherzolite, dunite and chromitite, as well as intrusive mafic sills and subvertical dikes, which coalesce into an upper Isla Negritos gabbroic sill complex. Minerals and whole-rock features of the Cpx-rich and Cpx-poor harzburgites share features of the abyssal and supra-subduction zone (SSZ) peridotites, respectively. To explain these characteristics two-stages of melting and refertilization processes are required. By means of trace element modeling, the composition of Cpx-rich harzburgites may be reproduced by up to ~ 5-10% melting of a primitive mantle source, and the composition of Cpx-poor harzburgites and dunites by ~ 15-18% melting of an already depleted mantle. Therefore, the Cpx-rich harzburgites can be interpreted as product of first-stage melting and low-degrees of melt-rock interaction in a mid-ocean ridge environment, and the Cpx-poor harzburgites and dunites as the product of second-stage melting and refertilization in a SSZ setting. The mafic sills and the Isla Negrito gabbros are genetically related and can be explained as crystallization from the liquids that were extracted from the lower SSZ mantle levels and emplaced at shallow conditions. The Murciélagos Island basalts are not directly related to the ultramafic and mafic rocks of the SEO. Their E-MORB-like composition is similar to most of the CLIP mafic lavas and suggests a common Caribbean plume-related source. The SEO represents a fragment of Pacific-derived, SSZ oceanic lithosphere emplaced onto the southern North America margin during the late Cretaceous. Because of the predominance of rollback-induced extension during its history, only a limited amount of crustal rocks were formed and preserved in the SEO.

Anatomy of a frozen axial melt lens from a fast-spreading paleo-ridge (Wadi Gideah, Oman ophiolite)

Science.gov (United States)

Müller, T.; Koepke, J.; Garbe-Schönberg, C.-D.; Dietrich, M.; Bauer, U.; Wolff, P. E.

2017-02-01

At fast-spreading mid-ocean ridges, axial melt lenses (AMLs) sandwiched between the sheeted dyke section and the uppermost gabbros are assumed to be the major magma source of crust formation. Here, we present our results from a field study based on a single outcrop of a frozen AML in the Samail ophiolite in the Sultanate of Oman which presents a whole suite of different lithologies and complex cutting relationships: varitextured gabbro with relics of primitive poikilitic clinopyroxene is intruded by massive quartz diorites and tonalites bearing relics of assimilated sheeted dykes, which in turn are cut by trondhjemite dykes. The whole is cut by basaltic dykes with chilled margins. The geochemical evolutionary trend of the varitextured gabbros, including some of the quartz diorites and tonalites, can be best modelled by fractional crystallisation of an experimental MORB parental melt composition containing 0.4 to 0.8 wt.% H2O. Patchy varitextured gabbros containing domains of primitive poikilitic clinopyroxene and evolved granular networks represent the record of in situ crystallisation. Some quartz diorites, often with xenoliths of sheeted dykes and exceptionally high Al2O3 contents, show a bulk trace element pattern more in accord with melts generated by experimental partial melting of dyke material. Highly evolved, crosscutting trondhjemite dykes show characteristic trace element patterns implying a formation by partial melting of sheeted dykes under lower water activity which is indicated by relatively low Al2O3 contents. The late basaltic dykes with chilled margins crosscutting all other lithologies show a relatively depleted geochemical character with pronounced negative Nb-Ta anomalies implying a genetic relationship to the second phase of magmatic Oman paleo-ridge activity (V2). The field relationships in combination with the petrological/geochemical trends reveal multiple sequences of MORB-type magma cooling (resulting in fractional crystallisation) and re

Origin of multiple serpentinization events in New Caledonia

Science.gov (United States)

Ulrich, M.; Guillot, S.; Muñoz, M.; Picard, C.

2011-12-01

Studies on serpentinites around the world have shown that various polymorphs can coexist depending on the temperature, pressure and chemistry of the formation environment. Identifying serpentine polymorphs can thus provide significant constrains on the geodynamic environment at the time of formation. The New Caledonia ophiolite (Southwest Pacific) is one of the world's largest (500 km long, 50 km wide and 2 km thick). Emplaced during Eocene, it is thrust upon the continental Norfolk ridge, which derived from the splitting of the East Gondwana margin during Lower Late Cretaceous. The ophiolite consists of a large continuous massif occurring in the south of the island and some smaller isolated klippes located along the West coast. The peridotites are mostly harzburgite, related to a supra-subduction zone environment. The northernmost massifs are also composed of lherzolites, inherited from the opening of the South Loyalty Basin where the ophiolite was formed. Serpentinization is ubiquitous (usually >50%) independently from the nature of the peridotite. However, numerous studies have focused on the ophiolite but very few on the serpentinite. In this study, we use the Raman spectroscopy to identify serpentine polymorph in each part of the ophiolite. In situ trace element measurements were performed to constrain the behavior of fluid mobile element (FME: As, Sb, B, Li, Cs, Pb, U, Ba, Sr), and we are currently analyzing stable isotopic ratios to investigate the origin of fluids. Our results show that lizardite represents ~90% of the serpentine in the New Caledonia ophiolite. Only the serpentine sole has recorded multiple serpentinization events. In this horizon, the lizardite is crosscut by millimeter to centimeter antigorite veins. Chrysotile is the last polymorph to crystallize in millimeter crackseals. If the formation of the lizardite can be easily related to abyssal history of the ophiolite for the lherzolite and its supra-subduction history for the harzburgite, the

From ocean depths to mountain tops: uplift of the Troodos Massif (Cyprus) constrained by (U-Th)/He thermochronology and geomorphic analysis

Science.gov (United States)

Morag, N.; Haviv, I.; Katzir, Y.

2013-12-01

The Troodos Massif of Cyprus, rising to nearly 2000 meters above sea level, encompasses one of the world's classic ophiolites. Following its formation at a seafloor spreading center in Late Cretaceous times, this slice of the NeoTethyan oceanic lithosphere was uplifted and eventually exposed on mountain tops during the Neogene. The final uplift and exhumation of the Troodos was previously assigned to Pleistocene age by observations in the circum-Troodos sedimentary strata. However, quantitative thermochronological and geomorphological data from the Massif itself were not available. Here we use apatite (U-Th)/He low-temperature thermochronology complemented by zircon (U-Th)/He and apatite fission track data, and combined with geomorphic analysis to constrain the exhumation and uplift history of the Troodos ophiolite. Apatite (U-Th)/He ages vary with depth from ~ 22 Ma at the top of the Gabbro sequence to ~ 6 Ma at the bottom of the sequence. The deepest sample from a Gabbro pegmatitic dyke intruding the ultramafic sequence yielded an age of ~ 3 Ma. Thermal modeling of apatite (U-Th)/He and fission track data delineates Plio - Pleistocene initiation of rapid uplift and exhumation of the Troodos ophiolite. The estimated cumulative exhumation since its initiation is 2-3 km. No evidence was found for significant uplift of the central Troodos area prior to that time. The geomorphic analysis delineates a bull's-eye zone at the center of the Troodos Massif, where local relief and channel steepness index are highest. The boundaries of this zone roughly correspond with the Mt. Olympus mantle outcrop and suggest recent, differential uplift of this zone relative to its surroundings. The most likely mechanism, which could drive such a focused bull's-eye uplift pattern is hydration of ultramafic rocks (serpentinization) leading to a decrease in rock density and subsequent diapiric uplift of the serpentinized lithospheric mantle.

Central sleep apnea

Science.gov (United States)

Sleep apnea - central; Obesity - central sleep apnea; Cheyne-Stokes - central sleep apnea; Heart failure - central sleep apnea ... Central sleep apnea results when the brain temporarily stops sending signals to the muscles that control breathing. The condition ...

Basement control in the development of the early cretaceous West and Central African rift system

Science.gov (United States)

Maurin, Jean-Christophe; Guiraud, René

1993-12-01

The structural framework of the Precambrian basement of the West and Central African Rift System (WCARS) is described in order to examine the role of ancient structures in the development of this Early Cretaceous rift system. Basement structures are represented in the region by large Pan-African mobile belts (built at ca. 600 Ma) surrounding the > 2 Ga West African, Congo and Sao Francisco cratons. Except for the small Gao trough (eastern Mali) located near the contact nappe of the Pan-African Iforas suture zone along the edge of the West African craton, the entire WCARS is located within the internal domains of the Pan-African mobile belts. Within these domains, two main structural features occur as the main basement control of the WCARS: (1) an extensive network of near vertical shear zones which trend north-south through the Congo, Brazil, Nigeria, Niger and Algeria, and roughly east-west through northeastern Brazil and Central Africa. The shear zones correspond to intra-continental strike-slip faults which accompanied the oblique collision between the West African, Congo, and Sao Francisco cratons during the Late Proterozoic; (2) a steep metamorphic NW-SE-trending belt which corresponds to a pre-Pan-African (ca. 730 Ma) ophiolitic suture zone along the eastern edge of the Trans-Saharian mobile belt. The post-Pan-African magmatic and tectonic evolution of the basement is also described in order to examine the state of the lithosphere prior to the break-up which occurred in the earliest Cretaceous. After the Pan-African thermo-tectonic event, the basement of the WCARS experienced a long period of intra-plate magmatic activity. This widespread magmatism in part relates to the activity of intra-plate hotspots which have controlled relative uplift, subsidence and occasionally block faulting. During the Paleozoic and the early Mesozoic, this tectonic activity was restricted to west of the Hoggar, west of Aïr and northern Cameroon. During the Late Jurassic

Lithological discrimination of accretionary complex (Sivas, northern Turkey) using novel hybrid color composites and field data

Science.gov (United States)

Özkan, Mutlu; Çelik, Ömer Faruk; Özyavaş, Aziz

2018-02-01

One of the most appropriate approaches to better understand and interpret geologic evolution of an accretionary complex is to make a detailed geologic map. The fact that ophiolite sequences consist of various rock types may require a unique image processing method to map each ophiolite body. The accretionary complex in the study area is composed mainly of ophiolitic and metamorphic rocks along with epi-ophiolitic sedimentary rocks. This paper attempts to map the Late Cretaceous accretionary complex in detail in northern Sivas (within İzmir-Ankara-Erzincan Suture Zone in Turkey) by the analysis of all of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) bands and field study. The new two hybrid color composite images yield satisfactory results in delineating peridotite, gabbro, basalt, and epi-ophiolitic sedimentary rocks of the accretionary complex in the study area. While the first hybrid color composite image consists of one principle component (PC) and two band ratios (PC1, 3/4, 4/6 in the RGB), the PC5, the original ASTER band 4 and the 3/4 band ratio images were assigned to the RGB colors to generate the second hybrid color composite image. In addition to that, the spectral indices derived from the ASTER thermal infrared (TIR) bands discriminate clearly ultramafic, siliceous, and carbonate rocks from adjacent lithologies at a regional scale. Peridotites with varying degrees of serpentinization illustrated as a single color were best identified in the spectral indices map. Furthermore, the boundaries of ophiolitic rocks based on fieldwork were outlined in detail in some parts of the study area by superimposing the resultant maps of ASTER maps on Google Earth images of finer spatial resolution. Eventually, the encouraging geologic map generated by the image analysis of ASTER data strongly correlates with lithological boundaries from a field survey.

Eclogitic breccia from the Monviso ophiolite complex: new field and petrographic data

Science.gov (United States)

Locatelli, Michele; Verlaguet, Anne; Federico, Laura; Agard, Philippe

2015-04-01

The Monviso meta-ophiolite complex (Northern Italy, Western Alps) represents a coherent portion of oceanic lithosphere metamorphosed under eclogite facies conditions during the Alpine orogeny (2.6 GPa - 550°C, Lago Superiore Unit, Angiboust et al., 2011), and exhibits from bottom to top a thick serpentinite sole locally capped by metasediments, Mg-Al-rich metagabbros, then Fe-Ti-metagabbros capped by metabasalts. This section is disrupted by three main shear zones. Our study focusses on the Lower Shear Zone (LSZ), situated between the serpentinite sole (to the East) and the Mg-metagabbro bodies (to the West), and composed of blocks of both Fe-Ti and Mg-Al metagabbros embedded in a talc and tremolite-rich serpentinite matrix. Among these blocks, some were described as eclogitic breccias and interpreted as the result of a seismic rupture plane (Angiboust et al., 2012). These breccias correspond to blocks of Fe-Ti-metagabbros that were brecciated in eclogitic facies conditions (as attested by the omphacite + garnet ± lawsonite cement of the breccia) in a fluid-rich environment, as suggested by the abundance of lawsonite in the cement. Here we present new field data on the distribution and petrographic characterization of these eclogitic blocks in the LSZ. The aim of this work is twofold: (I) detailed mapping of the eclogitic block distribution along the LSZ, in order to determine precisely the extent and representativity of the breccias and (II) characterization of the brecciated blocks, at the outcrop scale, to explore the brecciation processes and structures. Between Pian del Re and Colle di Luca localities, the occurrence of eclogite blocks is uniform along the strike of the shear-zone, resulting in a 16 km-long belt of outcropping eclogitic bodies embedded in serpentinite matrix. The shear-zone width, by contrast, varies from 1.3 km to 0.8 km. Three types of eclogitic blocks can be distinguished: (1) intact (i.e., not brecciated) blocks of Fe

Orden monetario y bancos centrales Monetary order and Central Banks

Directory of Open Access Journals (Sweden)

Aglietta Michel

1996-06-01

Full Text Available Con el enfoque evolucionista e institucionalista de la economía de las convenciones francesa, este trabajo analiza el surgimiento histórico de la banca central y la creación institucional del 'arte de la banca central'. El artículo estudia los modelos formales del orden monetario, la banca libre y la banca central, y analiza los eventos históricos que llevaron a que el Banco de Inglaterra inventara el arte de manejar los bancos centrales en conjunción con el aprendizaje colectivo e institucional que lo hizo posible. Aglietta muestra que la banca central no es una creación del Estado sino una creación institucional endógena al sistema de mercado.With the evolutionist and institutionalist focus of the economics of the French conventions, this paper analyzes the historical rise of the central bank and the institutional creation of the 'art of the central bank'. The article studies formal models of the monetary order, free banking and the central bank, and analyzes the historie events that led to the Bank of England inventing the art of managing the central banks, in conjunction with the collective and institutional learning that made it possible. Aglietta shows that the central bank is not a creation of the State, but rather aninstitutional creation endogenous to the market system.

The Regional Centrality of Vietnam’s Central Highlands

DEFF Research Database (Denmark)

Salemink, Oscar

2018-01-01

strategic value turned it into a battleground among various Vietnamese parties, France, and the United States. It was here that the outcome of the Indochina wars was determined, but at a terrible price for the local population. After the adoption of economic reforms in reunified Vietnam the Central......Vietnam’s Central Highlands—or Tây Nguyên—area is usually described as remote, backward, and primitive, but this region has played a central role in the history of the surrounding states and the wider East and Southeast Asia region. Far from isolated, the Central Highlands engaged in trade...... various rivalrous polities now known as Vietnam, Champa, Cambodia, Laos, and Thailand, the area occupied a strategic position in the wider mainland Southeast Asia region. With the emergence of a unified, neo-Confucianist Vietnamese state the region lost its centrality until the late colonial era, when its...

First-order similarities and differences between Alps, Dinarides, Hellenides and Anatolides-Taurides

Science.gov (United States)

Schmid, Stefan M.; Bernoulli, Daniel; Fügenschuh, Bernhard; Matenco, Liviu; Schefer, Senecio; Oberhänsli, Roland; van Hinsbergen, Douwe; Ustaszewski, Kamil

2013-04-01

We correlated tectonic units across several circum-Mediterranean orogen strands between the Alps, Carpathians, the Balkan Peninsula, the Aegean and Western Turkey. Our compilation allows discussing fundamental along-strike similarities and differences. One first-order difference is that Dinarides-Hellenides, Anatolides and Taurides represent orogens of opposite subduction polarity and age with respect to the Alps and Carpathians. The internal Dinarides are linked to the Alps and Western Carpathians along the Mid-Hungarian fault zone, a suspected former trench-trench transform fault; its lithospheric root was obliterated during Neogene back-arc extension that formed the Pannonian Basin. Dinarides and Hellenides alike consist of far-travelled nappes detached from the Adriatic continental margin along décollement horizons in Paleozoic or younger stratigraphic levels during Cretaceous and Cenozoic orogeny. The more internal nappes (i.e. Jadar-Kopaonik, Drina-Ivanjica, East Bosnian-Durmitor and their Pelagonian and Almopias equivalents in the Hellenides) are composite nappes whereby the allochthonous Adriatic margin sequences passively carry ophiolites (Western Vardar Ophiolitic Unit) obducted during the latest Jurassic-earliest Cretaceous. These obducted ophiolitic units, as well as ophiolites obducted onto Europe-derived units presently found in the East Carpathians (Eastern Vardar Ophiolitic Unit obducted onto the Dacia continental block), root in one single Neotethys ocean that started closing with the initiation of obduction in the latest Jurassic; final suturing occurred during Cretaceous times, terminating with the formation of the Sava-Izmir-Ankara suture in the latest Cretaceous. Ophiolitic "massifs" found outside the Sava-Izmir-Ankara suture zone do not mark oceanic sutures, nor do the Drina-Ivanjica and Pelagonian "massifs" represent independent continental fragments (terranes). The same logic applies to Western Turkey with the difference that the ophiolites

Centralized vs. De-centralized Multinationals and Taxes

DEFF Research Database (Denmark)

Nielsen, Søren Bo; Raimondos-Møller, Pascalis; Schjelderup, Guttorm

2005-01-01

The paper examines how country tax differences affect a multinational enterprise's choice to centralize or de-centralize its decision structure. Within a simple model that emphasizes the multiple conflicting roles of transfer prices in MNEs - here, as a strategic pre-commitment device and a tax...

Autotrophic Ecosystems on the Early Earth

Science.gov (United States)

Schulte, M.

2003-01-01

Ophiolite sequences, sections of lower oceanic crust and upper mantle that have been thrust onto continental craton, are located in northern and central California and provide easily accessible areas that serve as good analogs for similar, more extensive areas of the early Earth. We have begun investigating and characterizing these sites in order to understand better the processes that may be responsible for the water chemistry, mineralogy and biology of similar environments on the early Earth. The geophysical and geochemical processes in these terranes provide niches for unique communities of extremeophiles and likely provide a good analog to the location that first gave rise to life on Earth. The ophiolites found in northern and central California include the Trinity, Josephine, Coast Range and Point Sal, all of which are approximately 160 million years old. Fluids from serpentinizing springs are generally alkaline with high pH and H2 contents, indicating that the mafic rock compositions control the fluid composition through water-rock reactions during relatively low-grade hydrothermal processes. There are significant amounts of primary mineralogy remaining in the rocks, meaning that substantial alteration processes are still occurring in these terranes. The general reaction for serpentinization of olivine is given by one of the authors. olivine + H2O = serpentine + brucite + magnetite + H2. We have analyzed the mineralogical composition of several rock samples collected from the Coast Range Ophiolite near Clear Lake, CA by electron microprobe. The remnant primary mineralogy is fairly urnform in composition, with an olivine composition of Fo(sub 90), and with pyroxene compositions of En(sub 90) for orthopyroxene and En(sub 49)Wo(sub 48)Fs(sub 03) for the clinopyroxene. Other primary phases observed include chromites and other spinels. Examination of petrographic thin sections reveals that serpentinization reactions have occurred in these locations. The serpentine

A perspective multidisciplinary geological approach for mitigation of effects due to the asbestos hazard

Science.gov (United States)

Vignaroli, Gianluca; Rossetti, Federico; Belardi, Girolamo; Billi, Andrea

2010-05-01

Asbestos-bearing rock sequences constitute a remarkable natural hazard that poses important threat to human health and may be at the origin of diseases such as asbestosis, mesothelioma and lung cancer). Presently, asbestos is classified as Category 1 carcinogen by world health authorities. Although regulatory agencies in many countries prohibit or restrict the use of asbestos, and discipline the environmental asbestos exposure, the impact of asbestos on human life still constitutes a major problem. Naturally occurring asbestos includes serpentine and amphibole minerals characterised by fibrous morphology and it is a constituent of mineralogical associations typical of mafic and ultramafic rocks within the ophiolitic sequences. Release of fibres can occur both through natural processes (erosion) and through human activities requiring fragmentation of ophiolite rocks (quarrying, tunnelling, railways construction, etc.). As a consequence, vulnerability is increasing in sites where workers and living people are involved by dispersion of fibres during mining and milling of ophiolitic rocks. By analysing in the field different exposures of ophiolitic sequences from the Italian peninsula and after an extensive review of the existing literature, we remark the importance of the geological context (origin, tectonic and deformation history) of ophiolites as a first-order parameter in evaluating the asbestos hazard. Integrated structural, textural, mineralogical and petrological studies significantly improve our understanding of the mechanisms governing the nucleation/growth of fibrous minerals in deformation structures (both ductile and brittle) within the ophiolitic rocks. A primary role is recognised in the structural processes favouring the fibrous mineralization, with correlation existing between the fibrous parameters (such as mineralogical composition, texture, mechanics characteristics) and the particles released in the air (such as shape, size, and amount liberated

Geology and mineral resources of central Antioquia Department (Zone IIA), Colombia

Science.gov (United States)

Hall, R.B.; Alvarez A., Jairo; Rico H., Hector

1973-01-01

This report summarizes the geology of an area of some 6000 square kilometers in the northern part of the Central Cordillera of the Colombian Andes. The area, in north-central Department of Antioquia, was mapped between 1964 and 1968 as part of the Inventario Minero Nacional (IMN) project. Mineral resources are summarized within a larger area, designated as subzone ILK of IMN Zone If, which comprises almost 22,000 sq. kin, including the area mapped geologically by IMN and additional areas mapped by other agencies. The oldest formation is a micaceous paragneiss of early Paleozoic or possibly late Precambrian age. A thick geosynclinal sedimentary series accumulated during the Paleozoic Era and became regionally metamorphosed to greenschist (locally amphibolite) facies during the Permian or early Triassic; these schists and gneisses are designated collectively as the Valdivia Group. The Permian(?) orogenic episode included intrusion of concordant syntectonic plutons, mostly of tonalitic composition. Rocks of unequivocal Triassic or Jurassic age are not recognized. The Cretaceous is well represented by both igneous and sedimentary assemblages. Eugeosynclinal alpine ophiolites comprising submarine basalt flows and numerous intrusions of gabbro and serpentinite are prominent in the Lower Cretaceous, together with flysch composed of marine shale and lesser sandstone and conglomerate. The Upper Cretaceous is represented along the west border of the mapped area by submarine basalt flows and pyroclastic rocks, locally Interbedded with fine-grained clastic sedimentary beds, and lenses of dark laminated chert, at least part of which is radiolarian. The Late Cretaceous was marked by an orogenic event that profoundly folded and faulted all rocks and in the Central Cordillera caused low-grade metamorphism, the overprint of which is hardly observable in pre-Cretaceous rocks elsewhere. The Late Cretaceous orogeny culminated with discordant intrusion of the epizonal tonalitic

The role and conditions of second-stage mantle melting in the generation of low-Ti tholeiites and boninites: the case of the Manihiki Plateau and the Troodos ophiolite

Science.gov (United States)

Golowin, Roman; Portnyagin, Maxim; Hoernle, Kaj; Sobolev, Alexander; Kuzmin, Dimitry; Werner, Reinhard

2017-12-01

High-Mg, low-Ti volcanic rocks from the Manihiki Plateau in the Western Pacific share many geochemical characteristics with subduction-related boninites such as high-Ca boninites from the Troodos ophiolite on Cyprus, which are believed to originate by hydrous re-melting of previously depleted mantle. In this paper we compare the Manihiki rocks and Troodos boninites using a new dataset on the major and trace element composition of whole rocks and glasses from these locations, and new high-precision, electron microprobe analyses of olivine and Cr-spinel in these rocks. Our results show that both low-Ti Manihiki rocks and Troodos boninites could originate by re-melting of a previously depleted lherzolite mantle source (20-25% of total melting with 8-10% melting during the first stage), as indicated by strong depletion of magmas in more to less incompatible elements (Sm/Yb Y 0.5). In comparison with Troodos boninites, the low-Ti Manihiki magmas had distinctively lower H2O contents ( 2 wt% in boninites), 100 °C higher liquidus temperatures at a given olivine Fo-number, lower fO2 (ΔQFM + 0.2) and originated from deeper and hotter mantle (1.4-1.7 GPa, 1440 °C vs. 0.8-1.0 GPa, 1300 °C for Troodos boninites). The data provide new evidence that re-melting of residual upper mantle is not only restricted to subduction zones, where it occurs under hydrous conditions, but can also take place due to interaction of previously depleted upper mantle with mantle plumes from the deep and hotter Earth interior.

Geology of the Ulugh Muztagh area, northern Tibet

International Nuclear Information System (INIS)

Burchfiel, B.C.; Molnar, P.

1989-01-01

Within the Ulugh Muztagh area, north central Tibet, an east-west-trending ophiolitic melange marks a suture that apparently was formed during a late Triassic or slightly younger collision between a continental fragment to the south and the rest of Asia. The southern continental fragment carries a thick sequence of upper Triassic sandstone, but the contact between the sandstone and the ophiolitic melange is covered by a younger redbed sequence of unknown age. A suite of 2-mica, tourmaline-bearing leucogranite plutons and dikes intruded the Triassic sandstone at shallow crustal levels 10.5 to 8.4 Ma. These rocks range from granite to tonalite in composition, are geochemically very similar to slightly older High Himalayan leucogranite and are interpreted to have been derived by the partial melting of crustal material. We interpret this to mean that crustal thickening began in this part of the Tibetan plateau at least by 10.5 Ma. Welded rhyolitic tuff rests on a conglomerate that consists of abundant debris from the Ulugh Muztagh intrusive rocks and has yielded Ar/Ar ages of about 4 Ma. The tuffs are geochemically identical to the intrusive rocks suggesting that crustal thickening may have continued to 4 Ma. Crustal thickening probably occurred by distributed crustal shortening similar to shortening now occurring north of Ulugh Muztagh along the northern margin of the Tibetan Plateau. (orig.)

Geochronology and geochemistry of the Niujuanzi ophiolitic mélange, Gansu Province, NW China: implications for tectonic evolution of the Beishan Orogenic Collage

Science.gov (United States)

Wang, Shengdong; Zhang, Kexin; Song, Bowen; Li, Shucai; Li, Ming; Zhou, Jie

2018-01-01

The Niujuanzi ophiolitic mélange (NOM), located in the Beishan Orogenic Collage, marks the termination between the Huaniushan arc and Mingshui-Hanshan Massifs. The NOM is mainly composed of gabbros, diabases, plagiogranites, basalts, and greywacke. Two gabbros have ages of 433.8 ± 3.1 and 354.0 ± 3.3 Ma, two plagiogranites have ages of 429.8 ± 2 and 448.7 ± 2.0 Ma, and a diabase has an age of 433.4 ± 3.2 Ma. The gabbros and diabases are calc-alkaline and tholeiitic, with high Al2O3, CaO, and TiO2 contents and low FeOT contents. The gabbros have high Mg# values (49-82), while the diabases have relatively low Mg# values (46-61). The plagiogranites are calc-alkaline and metaluminous, with high SiO2 and Na2O contents and low Al2O3 and K2O contents. The gabbros and diabases are enriched in large iron lithophile elements and slightly depleted in high field strength elements relative to N-MORB and their trace element characteristics are similar to E-MORB. With respect to rare earth element (REE), they have slightly enriched LREEs relative to HREEs. The majority of the plagiogranite trace elements approximate those of the volcanic arc granite. The plagiogranites have obviously enriched LREEs relative to HREEs, with a slightly to strongly negative Eu anomaly, which is similar to ORG but distinct from volcanic arc and within plate granite. The NOM was formed from the Ordovician to the Carboniferous, representing the expansion period of the Niujuanzi Ocean. The gabbros, diabases, and plagiogranites were formed in a mid-ocean ridge environment. The gabbros and diabases were generated by different degrees of partial melting of the mantle, and the plagiogranites derived from both the crystallization differentiation of basaltic magma and the partial melting of amphibolites in the crust.

Structural styles and zircon ages of the South Tianshan accretionary complex, Atbashi Ridge, Kyrgyzstan: Insights for the anatomy of ocean plate stratigraphy and accretionary processes

Science.gov (United States)

Sang, Miao; Xiao, Wenjiao; Orozbaev, Rustam; Bakirov, Apas; Sakiev, Kadyrbek; Pak, Nikolay; Ivleva, Elena; Zhou, Kefa; Ao, Songjian; Qiao, Qingqing; Zhang, Zhixin

2018-03-01

The anatomy of an ancient accretionary complex has a significance for a better understanding of the tectonic processes of accretionary orogens and complex because of its complicated compositions and strong deformation. With a thorough structural and geochronological study of a fossil accretionary complex in the Atbashi Ridge, South Tianshan (Kyrgyzstan), we analyze the structure and architecture of ocean plate stratigraphy in the western Central Asian Orogenic Belt. The architecture of the Atbashi accretionary complex is subdivisible into four lithotectonic assemblages, some of which are mélanges with "block-in-matrix" structure: (1) North Ophiolitic Mélange; (2) High-pressure (HP)/Ultra-high-pressure (UHP) Metamorphic Assemblage; (3) Coherent & Mélange Assemblage; and (4) South Ophiolitic Mélange. Relationships between main units are tectonic contacts presented by faults. The major structures and lithostratigraphy of these units are thrust-fold nappes, thrusted duplexes, and imbricated ocean plate stratigraphy. All these rock units are complicatedly stacked in 3-D with the HP/UHP rocks being obliquely southwestward extruded. Detrital zircon ages of meta-sediments provide robust constraints on their provenance from the Ili-Central Tianshan Arc. The isotopic ages of the youngest components of the four units are Late Permian, Early-Middle Triassic, Early Carboniferous, and Early Triassic, respectively. We present a new tectonic model of the South Tianshan; a general northward subduction polarity led to final closure of the South Tianshan Ocean in the End-Permian to Late Triassic. These results help to resolve the long-standing controversy regarding the subduction polarity and the timing of the final closure of the South Tianshan Ocean. Finally, our work sheds lights on the use of ocean plate stratigraphy in the analysis of the tectonic evolution of accretionary orogens.

Is banking supervision central to central banking?

OpenAIRE

Joe Peek; Eric S. Rosengren; Geoffrey M. B. Tootell

1997-01-01

Whether central banks should play an active role in bank supervision and regulation is being debated both in the United States and abroad. While the Bank of England has recently been stripped of its supervisory responsibilities and several proposals in the United States have advocated removing bank supervision from the Federal Reserve System, other countries are considering enhancing central bank involvement in this area. Many of the arguments for and against these proposals hinge on the effe...

Lithosphere destabilization by melt percolation during pre-oceanic rifting: Evidence from Alpine-Apennine ophiolitic peridotites

Science.gov (United States)

Piccardo, Giovanni; Ranalli, Giorgio

2017-04-01

Orogenic peridotites from Alpine-Apennine ophiolite Massifs (Lanzo, Voltri, External and Internal Ligurides, - NW Italy, and Mt. Maggiore - Corsica) derive from the mantle lithosphere of the Ligurian Tethys. Field/structural and petrologic/geochemical studies provide constraints on the evolution of the lithospheric mantle during pre-oceanic passive rifting of the late Jurassic Ligurian Tethys ocean. Continental rifting by far-field tectonic forces induced extension of the lithosphere by means of km-scale extensional shear zones that developed before infiltration of melts from the asthenosphere (Piccardo and Vissers, 2007). After significant thinning of the lithosphere, the passively upwelling asthenosphere underwent spinel-facies decompression melting along the axial zone of the extensional system. Silica-undersaturated melt fractions percolated through the lithospheric mantle via diffuse/focused porous flow and interacted with the host peridotite through pyroxenes-dissolving/olivine-precipitating melt/rock reactions. Pyroxene dissolution and olivine precipitation modified the composition of the primary silica-undersaturated melts into derivative silica-saturated melts, while the host lithospheric spinel lherzolites were transformed into pyroxene-depleted/olivine-enriched reactive spinel harzburgites and dunites. The derivative liquids interacted through olivine-dissolving/orthopyroxene+plagioclase-crystallizing reactions with the host peridotites that were impregnated and refertilized (Piccardo et al., 2015). The saturated melts stagnated and crystallized in the shallow mantle lithosphere (as testified by diffuse interstitial crystallization of euhedral orthopyroxene and anhedral plagioclase) and locally ponded, forming orthopyroxene-rich/olivine-free gabbro-norite pods (Piccardo and Guarnieri, 2011). Reactive and impregnated peridotites are characterized by high equilibration temperatures (up to 1250 °C) even at low pressure, plagioclase-peridotite facies

Geologic Map of the Weaverville 15' Quadrangle, Trinity County, California

Science.gov (United States)

Irwin, William P.

2009-01-01

The Weaverville 15' quadrangle spans parts of five generally north-northwest-trending accreted terranes. From east to west, these are the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, and Western Hayfork terranes. The Eastern Klamath terrane was thrust westward over the Central Metamorphic terrane during early Paleozoic (Devonian?) time and, in Early Cretaceous time (approx. 136 Ma), was intruded along its length by the massive Shasta Bally batholith. Remnants of overlap assemblages of the Early Cretaceous (Hauterivian) Great Valley sequence and the Tertiary Weaverville Formation cover nearly 10 percent of the quadrangle. The base of the Eastern Klamath terrane in the Weaverville quadrangle is a peridotite-gabbro complex that probably is correlative to the Trinity ophiolite (Ordovician), which is widely exposed farther north beyond the quadrangle. In the northeast part of the Weaverville quadrangle, the peridotite-gabbro complex is overlain by the Devonian Copley Greenstone and the Mississippian Bragdon Formation. Where these formations were intruded by the Shasta Bally batholith, they formed an aureole of gneissic and other metamorphic rocks around the batholith. Westward thrusting of the Eastern Klamath terrane over an adjacent body of mafic volcanic and overlying quartzose sedimentary rocks during Devonian time formed the Salmon Hornblende Schist and the Abrams Mica Schist of the Central Metamorphic terrane. Substantial beds of limestone in the quartzose sedimentary unit, generally found near the underlying volcanic rock, are too metamorphosed for fossils to have survived. Rb-Sr analysis of the Abrams Mica Schist indicates a metamorphic age of approx. 380 Ma. West of Weavervillle, the Oregon Mountain outlier of the Eastern Klamath terrane consists mainly of Bragdon Formation(?) and is largely separated from the underlying Central Metamorphic terrane by serpentinized peridotite that may be a remnant of the Trinity ophiolite. The North Fork

Reassessment of the origin of the Dun Mountain Ophiolite, New Zealand : Nd-isotopic and geochemical evolution of magma suites

International Nuclear Information System (INIS)

Sivell, W.J.; McCulloch, M.T.

2000-01-01

Magmatic suites with contrasting isotopic and geochemical compositions, sequentially emplaced in different tectonic regimes, comprise the Dun Mountain Ophiolite Belt (DMOB), New Zealand. At D'Urville Island, the northernmost exposure of the DMOB, earliest erupted (stage 1) pillow basalts ε Nd (T) = +6.3 to +7.5, and are incompatible element enriched, like basalts from geochemically anomalous ridge segments. Overlying stage 2 basalts (sheeted flows) show a narrow range of ε Nd (T) = +8.3 + or -0.2, with chemical characteristics of depleted backarc basin basalts. These rocks are intruded by mafic to silicic stage 3 magmas, which have high uniform initial 143 Nd/ 144 Nd ratios (ε Nd (T) = +9.3 + or -0.2) over a wide range of 147 Sm/ 144 Nd values (yielding a precise Early Permian Nd-isotope age of 278 ± 4 Ma (MSWD = 0.48)). Stage 3 magmas show pronounced subduction-related geochemical signatures similar to island arc tholeiites (IAT) from immature arcs. They are closely analogous to some (boninite)-IAT magmas which characterise 'infant arc' eruptive activity in forearc basins of present-day Western Pacific island arc systems. A wide variety of stage 3 magma compositions, ranging from near-primary basaltic dikes (Mg = 74) to extremely fractionated silicic plagiogranites with uniformly very depleted isotopic ratios, is consistent with slow spreading rates which gave rise to polybaric, closed-system fractionation of magmas and periodic chamber abandonment. Some stage 3 rocks with SiO 2 levels in the andesite range have low-TiO 2 contents and high Mg, and may be fractionated equivalents of boninites. High ε Nd (T) values of stage 3 magmas indicate a lack of subducted sediment with inherited crustal residence signatures, and reflect the extent of supra-subduction zone (SSZ) mantle wedge depletion. DMOB stage 3 magmas may represent foreac magmatism that was the precursor to normal subduction-related volcanism established by c. 265 Ma in the Brook Street Arc and derived

A Crystallization-Temperature Profile Through Paleo-Oceanic Crust (Wadi Gideah Transect, Oman Ophiolite): Application of the REE-in-Plagioclase-Clinopyroxene Partitioning Thermometer

Science.gov (United States)

Mueller, S.; Hasenclever, J.; Garbe-Schönberg, D.; Koepke, J.; Hoernle, K.

2017-12-01

The accretion mechanisms forming oceanic crust at fast spreading ridges are still under controversial discussion. Thermal, petrological, and geochemical observations predict different end-member models, i.e., the gabbro glacier and the sheeted sill model. They all bear implications for heat transport, temperature distribution, mode of crystallization and hydrothermal heat removal over crustal depth. In a typical MOR setting, temperature is the key factor driving partitioning of incompatible elements during crystallization. LA-ICP-MS data for co-genetic plagioclase and clinopyroxene in gabbros along a transect through the plutonic section of paleo-oceanic crust (Wadi Gideah Transect, Oman ophiolite) reveal that REE partitioning coefficients are relatively constant in the layered gabbro section but increase for the overlying foliated gabbros, with an enhanced offset towards HREEs. Along with a systematic enrichment of REE's with crustal height, these trends are consistent with a system dominated by in-situ crystallization for the lower gabbros and a change in crystallization mode for the upper gabbros. Sun and Liang (2017) used experimental REE partitioning data for calibrating a new REE-in-plagioclase-clinopyroxene thermometer that we used here for establishing the first crystallization-temperature depth profile through oceanic crust that facilitates a direct comparison with thermal models of crustal accretion. Our results indicate crystallization temperatures of about 1220±8°C for the layered gabbros and lower temperatures of 1175±8°C for the foliated gabbros and a thermal minimum above the layered-to-foliated gabbro transition. Our findings are consistent with a hybrid accretion model for the oceanic crust. The thermal minimum is assumed to represent a zone where the descending crystal mushes originating from the axial melt lens meet with mushes that have crystallized in situ. These results can be used to verify and test thermal models (e.g., Maclennan et al

Effect of Hydrochemistry on Mineral Precipitation and Textural Diversity in Serpentinization-driven Alkaline Environments; Insights from Thermal Springs in the Oman Ophiolite.

Science.gov (United States)

Bach, W.; Giampouras, M.; Garcia-Ruiz, J. M.; Garrido, C. J.; Los, C.; Fussmann, D.; Monien, P.

2017-12-01

Interactions between meteoric water and ultramafic rocks within Oman ophiolite give rise to the formation of thermal spring waters of variable composition and temperature. Discharge of two different types of water forms complex hydrological networks of streams and ponds, in which the waters mix, undergo evaporation, and take up atmospheric CO2. We conducted a pond-by-pond sampling of waters and precipitates in two spring sites within the Wadi Tayin massif, Nasif and Khafifah, and examined how hydrochemistry and associated mineral saturation states affect the variations in mineral phases and textures. Three distinctive types of waters were identified in the system: a) Mg-type (7.9 11.6); Ca-OH-rich waters, and c) Mix-type (9.6 < pH < 11.5); waters arising upon mixing of Mg-type and Ca-type. PHREEQC was used to evaluate the role of mixing in aqueous speciation and the evolution of the saturation index value of different mineral phases. Mineral and textural characterization by X-ray diffraction, Raman spectroscopy and scanning electron microscopy were combined with these hydrogeochemical constraints to determine the factors controlling mineralogical and textural diversity in the system. In Ca-type waters, uptake of CO2 during the exposure of the fluids to the atmosphere is the predominant precipitation mechanism of CaCO3. High Mg:Ca ratios and high supersaturation rate of CaCO3 favor the growth of aragonite over calcite in mixed fluids. Changes in morphology and texture of aragonite crystals and crystal aggregates indicate the variations in the values of supersaturation and supersaturation rate of CaCO3 in the different water types. Brucite precipitation is common and driven by fluid mixing, while interaction with air-derived CO2 causes its alteration to hydromagnesite. The proximity of gabbroic lithologies appears to affect the presence of Al-bearing layered double hydroxides (LDHs). Furthermore, transformation of nesquehonite to dypingite in Mg-type waters record a

By-products of the serpentinization process on the Oman ophiolite : chemical and isotopic composition of carbonate deposits in alkaline springs, and associated secondary phases

Science.gov (United States)

Sissmann, O.; Martinez, I.; Deville, E.; Beaumont, V.; Pillot, D.; Prinzhofer, A.; Vacquand, C.; Chaduteau, C.; Agrinier, P.; Guyot, F. J.

2014-12-01

The isotopic compositions (d13C, d18O) of natural carbonates produced by the alteration of basic and ultrabasic rocks on the Oman ophiolite have been measured in order to better understand their formation mechanisms. Fossil carbonates developed on altered peridotitic samples, mostly found in fractures, and contemporary carbonates were studied. The samples bear a large range of d13C. Those collected in veins are magnesian (magnesite, dolomite) and have a carbon signature reflecting mixing of processes and important fractionation (-11‰ to 8‰). Their association with talc and lizardite suggests they are by-products of a serpentinization process, that must have occurred as a carbon-rich fluid was circulating at depth. On the other hand, the carbonates are mostly calcic when formed in alkaline springs, most of which are located in the vicinity of lithological discontinuities such as the peridotite-gabbro contact (Moho). Aragonite forms a few meters below the surface of the ponds in Mg-poor water, and is systematically associated with brucite (Mg(OH)2). This suggests most of the Mg dissolved at depth has reprecipitated during the fluid's ascension through fractures or faults as carbonates and serpentine. Further up, on the surface waters of the ponds (depleted in Mg and D.I.C.), thin calcite films precipitate and reach extremely negative d13C values (-28‰), which could reflect either a biological carbon source, or kinetic fractionation from pumping atmospheric CO2. Their formation represent an efficient and natural process for carbon dioxide mineral sequestration. The d18O signature from all samples confirm the minerals crystallized from a low-temperature fluid. The hyperalkaline conditions (pH between 11 and 12) allowing for these fast precipitation kinetics are generated by the serpentinization process occurring at depth, as indicated by the measured associated H2-rich gas flows (over 50%) seeping out to the surface.

Late Cretaceous intra-oceanic magmatism in the internal Dinarides (northern Bosnia and Herzegovina): Implications for the collision of the Adriatic and European plates

Science.gov (United States)

Ustaszewski, Kamil; Schmid, Stefan M.; Lugović, Boško; Schuster, Ralf; Schaltegger, Urs; Bernoulli, Daniel; Hottinger, Lukas; Kounov, Alexandre; Fügenschuh, Bernhard; Schefer, Senecio

2009-03-01

The Kozara Mountains of northern Bosnia and Hercegovina form part of the internal Dinarides and host two tectonically juxtaposed ophiolitic successions of different age. The southern part of the Kozara Mountains exposes the Western Vardar Ophiolitic Unit, which was obducted onto the Adriatic margin in the Late Jurassic. The northern part exposes a bimodal igneous succession that was thrust onto the Western Vardar Ophiolitic Unit during the latest Cretaceous to Early Paleogene. This bimodal igneous succession comprises isotropic gabbros, doleritic dikes, basaltic pillow lavas and rhyolites. Pelagic limestones, intercalated with pillow lavas, yielded a Campanian globotruncanid association, consistent with concordant U-Pb ages on zircons from dolerites and rhyolites of 81.39 ± 0.11 and 81.6 ± 0.12 Ma, respectively. Chondrite-normalised rare earth element patterns of the bimodal igneous rocks show enrichment of LREE over HREE. Primitive mantle-normalised multi-element diagrams do not reveal significant depletion of HFSE. The ɛNd(T) and initial 87Sr/ 86Sr isotopic values range from + 4.4 to + 6.3 and from 0.70346 to 0.70507 respectively, suggesting an intraoceanic origin. The bimodal igneous succession is unconformably overlain by Maastrichtian to Paleocene siliciclastics that contain abundant ophiolitic detritus, suggesting reworking of the Campanian magmatics. An Eocene turbiditic sandstone succession unconformably covers both the Western Vardar Ophiolitic Unit and the Late Cretaceous bimodal igneous successions. These observations suggest that the Adriatic Plate and the Europe-derived Tisza and Dacia Mega-Units were still separated by a deep basin floored by oceanic lithosphere until the Campanian and that its closure did not occur before the Maastrichtian to earliest Paleogene. This Late Cretaceous oceanic domain probably represented a remnant of the Vardar Ocean, or alternatively, the Alpine Tethys; possibly the traces of both oceanic domains were connected in

Reduced gas seepages in serpentinized peridotite complexes: Evidences for multiple origins of the H2-CH4-N2 gas mixtures

Science.gov (United States)

Deville, E.; Vacquand, C.; Beaumont, V.; Francois, G.; Sissmann, O.; Pillot, D.; Arcilla, C. A.; Prinzhofer, A.

2017-12-01

A comparative study of reduced gas seepages associated to serpentinized ultrabasic rocks was conducted in the ophiolitic complexes of Oman, the Philippines, Turkey and New Caledonia. This study is based on analyzes of the gas chemical composition, noble gases contents, and stable isotopes of carbon, hydrogen and nitrogen. These gas seepages are mostly made of mixtures of three main components which are H2, CH4 and N2 in various proportions. The relative contents of the three main gas components show 4 distinct families of gas mixtures (H2-rich, N2-rich, N2-H2-CH4 and H2-CH4). These families are interpreted as reflecting different zones of gas generation within or below the ophiolitic complexes. In the H2-rich family associated noble gases display signatures close to the value of air. In addition to the atmospheric component, mantle and crustal contributions are present in the N2-rich, N2-H2-CH4 and H2-CH4 families. H2-bearing gases are either associated to ultra-basic (pH 10-12) spring waters or they seep directly in fracture systems from the ophiolitic rocks. In ophiolitic contexts, ultrabasic rocks provide an adequate environment with available Fe2+ and high pH conditions that favor H2 production. CH4 is produced either directly by reaction of dissolved CO2 with basic-ultrabasic rocks during the serpentinization process or in a second step by H2-CO2 interaction. H2 is present in the gas when no more carbon is available in the system to generate CH4 (conditions of strong carbon restriction). The N2-rich family is associated with relatively high contents of crustal 4He. In this family N2 is interpreted as issued mainly from sediments located below the ophiolitic units.

Central Nervous System Vasculitis

Science.gov (United States)

... of Vasculitis / Central Nervous System (CNS) Vasculitis Central Nervous System (CNS) Vasculitis Swap out your current Facebook Profile ... Facebook personal page. Replace with this image. Central nervous system (CNS) vasculitis is inflammation of blood vessel walls ...

Outsourcing central banking

DEFF Research Database (Denmark)

Khoury, Sarkis Joseph; Wihlborg, Clas

2005-01-01

The literature on Currency Boards (CB) stops at the water edge in terms of dealing with the totality of the functions of a central bank. Monetary policy, and banking supervisioncan be "outsourced" in an open economy with substantial foreign direct investment (FDI)in the banking sector if political...... nationalism does not trump economic rationality. An orthodox CB renders the central banking function redundant in terms of interest rate and exchange rate determination. FDI in banking could perform the same role for the supervisory function of central banks. We use the case of Estonia to illustrate...... the feasibility of, and constraints on, outsourcing of central bank functions. A brief discussion of the Argentinian experience is used for contrast.Key words: Currency Board, Foreign Banks, Supervision, Regional Integration,outsourcing....

NIDDK Central Repository

Data.gov (United States)

U.S. Department of Health & Human Services — The NIDDK Central Repository stores biosamples, genetic and other data collected in designated NIDDK-funded clinical studies. The purpose of the NIDDK Central...

CENTRAL PLATEAU REMEDIATION

International Nuclear Information System (INIS)

ROMINE, L.D.

2006-01-01

A systematic approach to closure planning is being implemented at the Hanford Site's Central Plateau to help achieve the goal of closure by the year 2035. The overall objective of Central Plateau remediation is to protect human health and the environment from the significant quantity of contaminated material that resulted from decades of plutonium production in support of the nation's defense. This goal will be achieved either by removing contaminants or placing the residual contaminated materials in a secure configuration that minimizes further migration to the groundwater and reduces the potential for inadvertent intrusion into contaminated sites. The approach to Central Plateau cleanup used three key concepts--closure zones, closure elements, and closure process steps--to create an organized picture of actions required to complete remediation. These actions were merged with logic ties, constraints, and required resources to produce an integrated time-phased schedule and cost profile for Central Plateau closure. Programmatic risks associated with implementation of Central Plateau closure were identified and analyzed. Actions to mitigate the most significant risks are underway while high priority remediation projects continue to make progress

Actual versus Perceived Central Bank Transparency : The Case of the European Central Bank

NARCIS (Netherlands)

van der Cruijsen, C.A.B.; Eijffinger, S.C.W.

2007-01-01

Central banks have become more and more transparent about their monetary policy making process. In the central bank transparency lit- erature the distinction between actual and perceived central bank trans- parency is often lacking. However, as perceptions are crucial for the ac- tions of economic

Environmental exposure to asbestos: from geology to mesothelioma.

Science.gov (United States)

Bayram, Mehmet; Bakan, Nur Dilek

2014-05-01

This article aims to review the geological background of environmental asbestos exposure and the distribution of asbestos-related disease (ARD) in association with naturally occurring asbestos (NOA), and discusses the potential health risks associated with exposure to non-occupational asbestos. With the motion of continental and oceanic plates, in some parts of the world serpentinites in the lower layer of the oceanic plate move into the continental plate and form the so-called ophiolites. Ophiolites consist of soil and rocks containing serpentine-type asbestos. There is an increase in ARDs in regions close to ophiolites. Indoor exposure and outdoor exposure to NOA, outdoor exposure to industrial asbestos and mines, urbanization and construction works in NOA regions are the known sources and types of environmental asbestos exposure. Although there is an expectance of decline in ARDs caused by industrial exposure to asbestos, the environmental exposure to asbestos is still a challenge waiting to be overcome.

Structure and history of Hellenides

Energy Technology Data Exchange (ETDEWEB)

Argyriadis, I.; Forti, S.

2016-10-01

This study is based on some new field observations made on the group of the Eastern Hellenic regions. Our observations have led us to adopt a simplified view of the paleogeography of the Greek mainland before the Alpine orogenesis. The subsequent varied tectonic units originate mainly from the following paleogeographic areas: A carbonate Arabo-African shelf margin which displays several lateral transitions, ridges and basins. On the Greek mainland this margin is represented by the Preapulian, Ionian, Gavrovo-Tripolis, Parnassos zones, the Olympus platform and probably the Kavala and Thassos marble. A transition zone from the shelf units to the Tethys ophiolites (Pindos Zone, Styra, Argolis and Hydra, Eretrias new unit). Tethys ophiolites, which might represent either an ocean fault zone or subduction of the lithosphere along a weak area. A Hercynian continental mass (Serbomacedonian). This group is currently completed by the presence of a large tectonic melange connected to the ophiolite overthrust. (Author)

Orogenesis of the Oman Mountains - a new geodynamic model based on structural geology, plate reconstructions and thermochronology

Science.gov (United States)

Grobe, Arne; Virgo, Simon; von Hagke, Christoph; Ralf, Littke; Urai, Janos L.

2017-04-01

Ophiolite obduction is an integral part of mountain building in many orogens. However, because the obduction stage is usually overprinted by later tectonic events, obduction geodynamics and its influence on orogenesis are often elusive. The best-preserved ophiolite on Earth is the Semail Ophiolite, Oman Mountains. 350 km of ophiolite and the entire overthrusted margin sequence are exposed perpendicular to the direction of obduction along the northeastern coast of the Sultanate of Oman. Despite excellent exposure, it has been debated whether early stages of obduction included formation of a micro-plate, or if the Oman Mountains result from collision of two macro-plates (e.g. Breton et al., 2004). Furthermore, different tectonic models for the Oman Mountains exist, and it is unclear how structural and tectonic phases relate to geodynamic context. Here we present a multidisciplinary approach to constrain orogenesis of the Oman Mountains. To this end, we first restore the structural evolution of the carbonate platform in the footwall of the Semail ophiolite. Relative ages of nine structural generations can be distinguished, based on more than 1,500 vein and fault overprintings. Top-to-S overthrusting of the Semail ophiolite is witnessed by three different generations of bedding confined veins in an anticlockwise rotating stress field. Rapid burial induced the formation of overpressure cells, and generation and migration of hydrocarbons (Fink et al., 2015; Grobe et al., 2016). Subsequent tectonic thinning of the ophiolite took place above a top-to-NNE crustal scale, ductile shear zone, deforming existing veins and forming a cleavage in clay-rich layers. Ongoing extension formed normal- to oblique-slip faults and horst-graben structures. This was followed by NE-SW oriented ductile shortening, the formation of the Jebel Akhdar anticline, potentially controlled by the positions of the horst-graben structures. Exhumation in the Cenozoic was associated with low angle normal

Development of Next-Generation Borehole Magnetometer and Its Potential Application in Constraining the Magnetic Declination of Oman Samail Ophiolite at ICDP Drill Sites

Science.gov (United States)

Lee, S. M.; Parq, J. H.; Kim, H.; Moe, K.; Lee, C. S.; Kanamatsu, T.; Kim, K. J.; Bahk, K. S.

2017-12-01

Determining the azimuthal orientation of core samples obtained from deep drilling is extremely difficult because the core itself could have rotated during drilling operations. Several indirect methods have been devised to address this issue, but have certain limitations. Thus it is still a challenge to determine the azimuthal orientation consistently over the entire length of the hole. Provided that the recovery rate is high and thus all the other magnetic properties such as magnetization intensity and inclination are measured from the recovered cores, one possible method for ascertaining magnetic declination information is to measure the magnetic field inside the empty borehole and invert for the best fitting declination. However, there are two major problems: one is that present-day borehole magnetometers are not precise enough to resolve changes in direction of magnetization, and the other is that in most rock drilling experiments the rate of recovery is low. To overcome the first major problem which is technical, scientists from Korea and Japan jointly conducted the development for the next-generation borehole magnetometer, namely 3GBM (3rd Generation Borehole Magnetometer). The borehole magnetometer which uses fiber-optic laser gyro promises to provide accurate information on not only the magnetic field itself but also the orientation of the instrument inside the borehole. Our goal is to deploy this borehole magnetometer in the ICDP Oman Drilling Project Phase 2 drilling experiment early 2018. The site may be suitable for the investigation because, as recent Phase 1 of the Oman Samail Ophiolite drilling has demonstrated, the recovery rate was very high. Also the post-drilling measurements onboard DV Chikyu have shown that much of the recovered samples has moderate magnetization intensity on the order of 0.1 and 1 A/m. Here, we present the results of numerical simulation of magnetic field inside the borehole using finite element method to show that magnetic

Anomalously low strength of serpentinite sheared against granite and implications for creep on the Hayward and Calaveras Faults

Science.gov (United States)

Moore, Diane E.; Lockner, David A.; Ponce, David A.

2010-01-01

Serpentinized ophiolitic rocks are juxtaposed against quartzofeldspathic rocks at depth across considerable portions of the Hayward and Calaveras Faults. The marked compositional contrast between these rock types may contribute to fault creep that has been observed along these faults. To investigate this possibility, we are conducting hydrothermal shearing experiments to look for changes in frictional properties resulting from the shear of ultramafic rock juxtaposed against quartzose rock units. In this paper we report the first results in this effort: shear of bare-rock surfaces of serpentinite and granite, and shear of antigorite-serpentinite gouge between forcing blocks of granitic rock. All experiments were conducted at 250°C. Serpentinite sheared against granite at 50 MPa pore-fluid pressure is weaker than either rock type separately, and the weakening is significantly more pronounced at lower shearing rates. In contrast, serpentinite gouge sheared dry between granite blocks is as strong as the bare granite surface. We propose that the weakening is the result of a solution-transfer process involving the dissolution of serpentine minerals at grain-to-grain contacts. Dissolution of serpentine is enhanced by modifications to pore-fluid chemistry caused by interaction of the fluid with the quartz-bearing rocks. The compositional differences between serpentinized ultramafic rocks of the Coast Range Ophiolite and quartzofeldspathic rock units such as those of the Franciscan Complex may provide the mechanism for aseismic slip (creep) in the shallow crust along the Hayward, Calaveras, and other creeping faults in central and northern California.

SECURITY THREATS IN CENTRAL ASIA

Directory of Open Access Journals (Sweden)

Çağla Gül Yesevi

2013-07-01

Full Text Available This study will analyze main security threats in Central Asia. It is obvious thatsince the end of Cold War, there have been many security threats in Central Asiaas internal weakness of Central Asian states, terrorism, transnational crime,economic insecurity, environmental issues, drug trafficking, ethnic violence,regional instability. This study will propose thatwith increasing interdependence,states need each other to solve these global security problems. In that sense,regional and sub-regional cooperation between Central Asian states and with otherregional actors has been witnessed. It is clear that the withdrawal of NATO fromAfghanistan will destabilize Central Asia. This study will investigate overallsecurity situation in Central Asia and affects andcontributions of regionalorganizations to Eurasian security

Demographic tensions in Central America.

Science.gov (United States)

1986-08-01

This discussion of Central America focuses on the rapid growth of its population, its stagnating economy, and those countries that are socioeconomically advanced. Between 1950-85 the population of Central America tripled, from 9.1 million to 26. 4 million, due to marked mortality declines and the absence of off-setting fertility declines. The distribution of Central Americas's growing populations sets its population growth apart from that of other developing regions. Currently, almost half of all Central Americans live in cities. Although the average growth rate for Central American countries has fallen and is expected to drop further, the decline does not counterbalance the effect of the absolute rise in population numbers. The average annual growth rate of more than 3% annually in the 1960s fell to about 2.6% in recent years, but this decline is due primarily to socioeconomically advanced Costa Rica and Panama. Central America's age structure further complicates the population crisis. About 43% of Central Americans are under the age of 15. When the increasingly larger young population group enters it reproductive years, the potential for future growth (albeit the falling rate of population increase) is unparalleled. UN population projections show the region's population at 40 million by the year 2000. The 1973 oil crisis began a downward spiral for the buoyant post World War II Central American economy. Between 1950-79, real per capita income growth in Central America doubled, with Central American economies growing an average of 5.3% annually. By the early 1980s, overseas markets of the trade-dependent countries of Central America had dried up due to protectionism abroad and slumping basic commodity prices. These and other factors plunged Central America into its current economic malaise of falling real per capita income, rising unemployment, curtailed export led economic growth, and a rising cost of living. In general, economic growth in Central America

Europa central

Directory of Open Access Journals (Sweden)

Karel BARTOSEK

2010-02-01

Full Text Available La investigación francesa continúa interesándose por Europa Central. Desde luego, hay límites a este interés en el ambiente general de mi nueva patria: en la ignorancia, producto del largo desinterés de Francia por este espacio después de la Segunda Guerra Mundial, y en el comportamiento y la reflexión de la clase política y de los medios de comunicación (una anécdota para ilustrar este ambiente: durante la preparación de nuestro coloquio «Refugiados e inmigrantes de Europa Central en el movimiento antifascista y la Resistencia en Francia, 1933-1945», celebrado en París en octubre de 1986, el problema de la definición fue planteado concreta y «prácticamente». ¡Y hubo entonces un historiador eminente, para quién Alemania no formaría parte de Europa Central!.

Drilling the leading edge of the mantle wedge and the underlying metamorphic sole of the Samail Ophiolite: Hole BT1B, Oman Drilling Project

Science.gov (United States)

Morishita, T.; Kelemen, P. B.; Coggon, J. A.; Harris, M.; Matter, J. M.; Michibayashi, K.; Takazawa, E.; Teagle, D. A. H.

2017-12-01

Hole BT1B (23°21.861' N, 58°10.957' E) was drilled by the Oman Drilling Project (OmDP) on the north side of Wadi Mansah in the Samail ophiolite, Oman. OmDP is an international collaboration supported by the International Continental Scientific Drilling Program, Deep Carbon Observatory, NSF, IODP, JAMSTEC, and the European, Japanese, German and Swiss Science Foundations, with in-kind support in Oman from the Ministry of Regional Municipalities and Water Resources, Public Authority of Mining, Sultan Qaboos University, and the German University of Technology. Hole BT1B was cored from 6 to 23 March 2017, to a depth of 300.05 m. The outer surfaces of the cores were imaged and described onsite before being curated, boxed and shipped to the IODP drill ship Chikyu. Hole BT1B sampled carbonated peridotite (listvenite), 2 carbonate-veined serpentinite bands at 80-100 and 180-185 m depth, a few cm of ultracataclasite and 70 cm of fault gouge at 197 m depth, followed by 103 m metamorphic sole. Onboard Chikyu, BT1B underwent X-ray computed tomography (CT) and multi-sensor logging, imaging and spectroscopy, macroscopic and thin section observations, physical properties measurements, and XRF, XRD and ICP-MS analyses. 1st authors of abstracts reporting initial results are Beinlich (matrix characteristics), de Obeso (modeling mass transfer), Godard (XRF and ICP-MS whole rock data), Greenberger (infrared spectroscopy), Johnson (XRF core scanner), Kelemen (overall petrology), Manning (veins), and Michibayashi (X-ray CT). Listvenite is composed of carbonate + quartz + Fe-oxyhydroxides, + minor relict spinel ± chromian mica (fuchsite). The mineralogy suggests formation at < 150°C. The bulk rock density is similar to that of gabbro but the P-wave velocity is generally higher. Rock textures suggest viscous deformation, while additional brittle deformation is recorded by older veins and younger breccias and faults. The metamorphic sole consists of fine-grained to microcrystalline

Effects of interaction between ultramafic tectonite and mafic magma on Nd-Pb-Sr isotopic systems in the Neoproterozoic Chaya Massif, Baikal-Muya ophiolite belt

Science.gov (United States)

Amelin, Yuri V.; Ritsk, Eugeni Yu.; Neymark, Leonid A.

1997-04-01

Sm-Nd, Rb-Sr and U-Pb isotopic systems have been studied in minerals and whole rocks of harzburgites and mafic cumulates from the Chaya Massif, Baikal-Muya ophiolite belt, eastern Siberia, in order to determine the relationship between mantle ultramafic and crustal mafic sections. Geological relations in the Chaya Massif indicate that the mafic magmas were emplaced into, and interacted with older solid peridotite. Hand picked, acid-leached, primary rock-forming and accessory minerals (olivine, orthopyroxene, clinopyroxene and plagioclase) from the two harzburgite samples show coherent behavior and yield 147Sm/ 144Nd- 143Nd/ 144Nd and 238U/ 204Pb- 206Pb/ 204Pb mineral isochrons, corresponding to ages of 640 ± 58 Ma (95% confidence level) and 620 ± 71 Ma, respectively. These values are indistinguishable from the crystallization age of the Chaya mafic units of 627 ± 25 Ma (a weighted average of internal isochron Sm-Nd ages of four mafic cumulates). The Rb-Sr and Sm-Nd isotopic systems in the harzburgite whole-rock samples were disturbed by hydrothermal alteration. These alteration-related isotopic shifts mimic the trend of variations in primary isotopic compositions in the mafic sequence, thus emphasizing that isotopic data for ultramafic rocks should be interpreted with great caution. On the basis of initial Sr and Nd values, ultramafic and mafic rocks of the Chaya Massif can be divided into two groups: (1) harzburgites and the lower mafic unit gabbronorites withɛ Nd = +6.6 to +7.1 andɛ Sr = -11 to -16; and (2) websterite of the lower unit and gabbronorites of the upper mafic unit:ɛ Nd = +4.6 to +6.1 andɛ Sr = -8 to -9. Initial Pb isotopic ratios are identical in all rocks studied, with mean values of 206Pb/ 204Pb= 16.994 ± 0.023 and 207Pb/ 204Pb= 15.363 ± 0.015. The similarity of ages and initial isotopic ratios within the first group indicates that the isotopic systems in the pre-existing depleted peridotite were reset by extensive interaction with

Structure and evolution of the northern Oman margin: gravity and seismic constraints over the Zagros-Makran-Oman collision zone

Science.gov (United States)

Ravaut, P.; Bayer, R.; Hassani, R.; Rousset, D.; Yahya'ey, A. Al

1997-09-01

The obduction process in Oman during Late Cretaceous time, and continental-to-oceanic subduction along the Zagros-Makran region during the Tertiary are consequences of the Arabian-Eurasian collision, resulting in construction of complex structures composed of the Oman ophiolite belt, the Zagros continental mountain belt and the Makran subduction zone with its associated accretionary wedge. In this paper, we jointly interpret Bouguer anomaly and available petroleum seismic profiles in terms of crustal structures. We show that the gravity anomaly in northern Oman is characterized by a high-amplitude negative-positive couple. The negative anomaly is coincident with Late Cretaceous (Fiqa) and Tertiary (Pabdeh) foreland basins and with the Zagros-Oman mountain belts, whereas the positive anomaly is correlated to the ophiolite massifs. The Bouguer anomaly map indicates the presence of a post-Late Cretaceous sedimentary basin, the Sohar basin, centred north of the Batinah plain. We interpret the negative/positive couple in terms of loading of the elastic Arabian lithosphere. We estimate the different Cretaceous-to-Recent loads, including topography, ophiolite nappes, sedimentary fill and the accretionary prism of the Makran trench. A new method, using Mindlin's elastic plate theory, is proposed to model the 2D deflection of the heterogeneous elastic Arabian plate, taking into account boundary conditions at the ends of the subducted plate. We show that remnant ophiolites are isolated from Tethyan oceanic lithosphere in the Gulf of Oman by a continental basement ridge, a NW prolongation of the Saih-Hatat window. Loading the northward-limited ophiolite blocks explains the deflection of the Fiqa foredeep basin. West of the Musandam Peninsula, the Tertiary Pabdeh foredeep is probably related to the emplacement of a 8-km-thick tectonic prism located on the Musandam Peninsula and in the Strait of Hormuz. Final 2D density models along profiles through the Oman mountain belt and

Central Banking after the Crisis

OpenAIRE

Frederick S. Mishkin

2013-01-01

This paper explores where central banking is heading after the recent financial crisis. First it discusses the central bank consensus before the crisis and then outlines the key facts learned from the crisis that require changes in the way central banks conduct their business. Finally, it discusses four main areas in which central banks are altering their policy frameworks: 1) the interaction between monetary and financial stability policies, 2) nonconventional monetary policy, 3) risk manage...

Central ignition scenarios for TFTR

International Nuclear Information System (INIS)

Zweben, S.J.; Redi, M.H.; Bateman, G.

1986-03-01

The possibility of obtaining ignition in TFTR by means of very centrally peaked density profiles is examined. It is shown that local central alpha heating can be made to exceed local central energy losses (''central ignition'') under global conditions for which Q greater than or equal to 1. Time dependent 1-D transport simulations show that the normal global ignition requirements are substantially relaxed for plasmas with peaked density profiles. 18 refs., 18 figs

Colloquium on Central Asia; Colloque sur l'Asie centrale

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This colloquium on Azerbaijan was organized by the direction of international relations of the French Senate and the French center of foreign trade (CFCE). This document gathers the interventions of the participants and the debates with the audience following these interventions. The topics treated concern: - the present day political-economical situation of Central Asia countries (problem of borders, relations with Russia and China); - the economies of Central Asia countries: short term problems and medium-term perspectives; - the relations with the European Union (political, economical, trade and investments, perspectives); - the European energy stakes of Caspian sea (oil and gas reserves, development of hydrocarbon resources, exploitation and transport constraints, stakes for Europe and France); - TotalFinaElf company in Central Asia (Kazakhstan, Azerbaijan, enclavement problem); - the economical impacts of the TRACECA pathway (Transport Corridor Europe Caucasus Asia). (J.S.)

Alpha current flow betweenness centrality

NARCIS (Netherlands)

Avrachenkov, K.; Litvak, Nelli; Medyanikov, V.; Sokol, M.

2013-01-01

A class of centrality measures called betweenness centralities reflects degree of participation of edges or nodes in communication between different parts of the network. The original shortest-path betweenness centrality is based on counting shortest paths which go through a node or an edge. One of

Observations of central stars

International Nuclear Information System (INIS)

Lutz, J.H.

1978-01-01

Difficulties occurring in the observation of central stars of planetary nebulae are reviewed with emphasis on spectral classifications and population types, and temperature determination. Binary and peculiar central stars are discussed. (U.M.G.)

[Central diabetes insipidus: diagnostic difficulties].

Science.gov (United States)

Matoussi, N; Aissa, K; Fitouri, Z; Hajji, M; Makni, S; Bellagha, I; Ben Becher, S

2008-06-01

Central diabetes insipidus is rare in children. Characteristic features include polyuria and polydipsia due to arginine vasopressin deficiency. The differential diagnosis of polyuric states may be difficult. Etiologic diagnosis of central diabetes insipidus may be an equally difficult task. To specify the difficulties encountered in the diagnosis of central diabetes insipidus and to point out features of the etiologic work-up and of long-term follow-up of children with idiopathic central diabetes insipidus. A retrospective study of 12 children admitted with a polyuria/polydipsia syndrome to the pediatric - consultation and emergency unit of the children's hospital of Tunis between 1988 and 2005. Children with acquired nephrogenic central diabetes insipidus were excluded. Fourteen-hour fluid restriction test and/or desmopressin test were used without plasma vasopressin measurement. Eight patients were classified as having central diabetes insipidus, which was severe in seven children and partial in one girl. One patient was classified as having primary polydipsia. The diagnosis remains unclear in three patients. The etiological work-up in eight patients with central diabetes insipidus enabled the identification of Langerhan's-cell histiocytosis in two patients and neurosurgical trauma in one. The cause was considered idiopathic in five patients. The median follow-up of the five patients with idiopathic central diabetes insipidus was five years two months plus or minus six years seven months (range five months, 14.5 years). During this follow-up, neither brain magnetic resonance imaging scans findings nor anterior pituitary function have changed. Fluid restriction and desmopressin tests did not enable an accurate distinction between partial diabetes insipidus and primary polydipsia. Regular surveillance is warranted in patients with idiopathic central diabetes insipidus to identify potential etiologies.

Sedimentary record of the obduction of the Samail ophiolite in northern Oman: the Muti Formation in the Sail Hatat window

Science.gov (United States)

Ducassou, Céline; Robin, Cecile; Poujol, Marc; Al-Rahbi, Basim; Estournes, Guilhem

2016-04-01

The obduction of the Samail Ophiolite in Oman took place during the Upper Cretaceous. Since then, the northern part of Oman has been relatively preserved from deformation and is therefore one of the best places to study obduction processes. In addition, radiometric data provide good constraints on the timing of obduction from the formation of the metamorphic sole until the exhumation of the high-pressure / low-temperature metamorphic rocks involved in the subduction zone below the oceanic lithosphere. However, the response of the continental margin during the obduction is still poorly constrained. If most of the models suggest the development of a flexural basin and an associated forebulge such as in continental collision, their recognition within the syn-tectonic deposits led to different interpretations. The geometry of the youngest syn-tectonic deposits (Fiqa Formation) is relatively well constrained by sub-surface data that suggest a southward migration of the depocenter and progressive onlaps on the southern margin of the basin. The context of sedimentation of the oldest syn-tectonic deposits (Muti Formation) preserved below the nappes in the Oman Mountains is, however, still poorly understood. The location of the sedimentation area with respect of the forebulge, for instance, remains unclear. In order to acquire better constraints on the record, on the Arabian platform, of first steps of the obduction, the analysis of several sections of the Muti Formation has been performed. We present here our main results for the north-eastern part of the Oman Mountains, in the Sail Hatat window, where the thickest successions have been described in Quryat and Bidbid area, respectively located in the eastern and western part of the Sail Hatat window. Sedimentological and structural analysis have been combined to reconstitute the evolution of depositional environments in areas strongly affected by deformation. In addition, systematic measurements and restoration of

Gangs in Central America

National Research Council Canada - National Science Library

Ribando, Clare

2005-01-01

... activities of Central American gangs. Citizens in several Central American countries have identified crime and gang violence among the top issues of popular concern, and Honduras and El Salvador have recently enacted tough anti-gang legislation...

Influence of arm movement on central tip location of peripherally inserted central catheters (PICCs)

International Nuclear Information System (INIS)

Connolly, Bairbre; Amaral, Joao; Walsh, Sharon; Temple, Michael; Chait, Peter; Stephens, Derek

2006-01-01

PICCs are increasingly employed in children. Some of their risks relate to the location of the central tip. Despite care when placing lines, they sometimes move. To evaluate the influence of arm movement on the central tip location of PICCs placed in children. The central tip location of PICCs was studied in 85 children, with the arm placed in six positions. The variables of side, vein, site and arm position were examined to measure the direction and range of tip movement. The side, site or vein used did not influence the range of movement of the central tip. Change in position of the arm had a significant influence on the central tip location, moving it an average of 2.2 rib spaces, a maximum of 3.5 ribs. Elbow bending and adduction of the arm caused the central tip to move deeper into the chest, compared to when the arm was straight and abducted 90 . Arm position is the significant variable influencing PICC movement. Side, site and vein do not influence the range of movement significantly. Most PICCs descend deeper into the chest with arm adduction and elbow bending. (orig.)

Oceanic units in the core of the External Rif (Morocco): Intramargin hiatus or South-Tethyan remnants?

Science.gov (United States)

Benzaggagh, Mohamed; Mokhtari, Abdelkader; Rossi, Philippe; Michard, André; El Maz, Abdelkhader; Chalouan, Ahmed; Saddiqi, Omar; Rjimati, Ech-Cherki

2014-07-01

The aim of this paper is to describe the mafic rocks that crop out in the central-western Mesorif Zone (External Rif Belt), and discuss their geodynamic signification. Basalt flows, olistoliths and breccias occur in Oxfordian-Berriasian deposits of Mesorif units ascribed to the distal part of the African paleomargin. The climax of volcanic activity is observed at the northern border of a Kimmeridgian carbonate platform progressively dismembered during the Tithonian-Berriasian. In spite of the alteration of the basalts, their petrological and geochemical characters point to E-MORB affinities. The studied gabbro massifs (Bou Adel, Kef el Rhar west and north) occur as restricted slivers or klippes within the Senhadja nappe or mélange of the internal Mesorif, which overlies the basalt-bearing units and other, more external Mesorif units. The compositions range from troctolitic olivine gabbro to ferrogabbro with frequent ortho- to heteradcumulate textures; they display typical tholeiitic affinity. The gabbro massifs are crosscut by trondjhemite dykes and overlain by metabasalts, fault-scarp breccias, ophicalcites, marbles and radiolarites. Composition featuring initial near liquid composition, display multi elements patterns close to those of E-MORB, with a weak Eu negative anomaly and evidence of slight crustal contamination. These gabbro massifs were regarded as Jurassic-Cretaceous intrusions, locally dated (K-Ar) at 166 ± 3 Ma. Conversely, we assume they represent discrete samples of a Jurassic-Cretaceous oceanic basement (ophiolites), emplaced tectonically in the Senhadja nappe (mélange) of the central Mesorif. The correlation of both these types of mafic rock associations (paleomargin basalts and ophiolite klippes) with the serpentinites of the eastern Mesorif (Beni Malek) and Oran mountains (Algeria) is then briefly discussed. We conclude that the previous hypothesis of an intramargin “Mesorif suture zone” must be reconsidered, being challenged by that of a

Geochemistry and jasper beds from the Ordovician Løkken ophiolite, Norway: origin of proximal and distal siliceous exhalites

Science.gov (United States)

Grenne, Tor; Slack, John F.

2005-01-01

Stratiform beds of jasper (hematitic chert), composed essentially of SiO2 (69-95 wt %) and Fe2O3 (3-25 wt %), can be traced several kilometers along strike in the Ordovician L??kken ophiolite, Norway. These siliceous beds are closely associated with volcanogenic massive sulfide (VMS) deposits and are interpreted as sea-floor gels that were deposited by fallout from hydrothermal plumes in silica-rich seawater, in which plume-derived Fe oxyhydroxide particles promoted flocculation and rapid settling of large (???200 ??m) colloidal particles of silica-iron oxyhydroxide. Concentrations of chalcophile elements in the jasper beds are at the parts per million level implying that sulfide particle fallout was insignificant and that the Si-Fe gel-forming plumes were mainly derived from intermediate- (100??-250??C) to high-temperature (>250??) white smoker-type vents with high Fe/S ratios. The interpreted setting is similar to that of the Lau basin, where high-temperature (280??-334??C) white smoker venting alternates or overlaps with sulfide mound-forming black smoker venting. Ratios of Al, Sc, Th, Hf, and REE to iron are very low and show that the detrital input was <0.1 percent of the bulk jasper. Most jasper beds are enriched in U, V, P, and Mo relative to the North American Shale Composite, reflecting a predominantly seawater source, whereas REE distribution patterns (positive Eu and negative Ce anomalies) reflect variable mixing of hydrothermal solutions with oxic seawater at dilution ratios of ???102 to 104. Trace element variations in the gel precursor to the jasper are thought to have been controlled by coprecipitation and/or adsorption by Fe oxyhydroxide particles that formed by the oxidation of hydrothermal Fe2+ within the variably seawater-diluted hydrothermal plume(s). Thick jasper layers near the H??ydal VMS orebody show distinct positive As/Fe and Sb/Fe anomalies that are attributed to near-vent rapid settling of Si-Fe particles derived from As- and Sb

Abyssal and hydrated mantle wedge serpentinised peridotites: a comparison of the 15°20'N fracture zone and New Caledonia serpentinites

Science.gov (United States)

Mothersole, Fiona Elizabeth; Evans, Katy; Frost, B. Ronald

2017-08-01

Subduction of serpentinised mantle transfers oxidised and hydrated mantle lithosphere into the Earth, with consequences for the oxidation state of sub-arc mantle and the genesis of arc-related ore deposits. The role of subducted serpentinised mantle lithosphere in earth system processes is uncertain because subduction fluxes are poorly constrained. Most subducted serpentinised mantle is serpentinised on the ocean floor settings. Yet this material is poorly represented in the literature because it is difficult to access. Large volumes of accessible serpentinite are available in ophiolite complexes, and most interpretations of subduction fluxes associated with ultramafic rocks are based on ophiolite studies. Seafloor and ophiolite serpentinisation can occur under different conditions, so it is necessary to assess if ophiolite serpentinites are a good proxy for seafloor serpentinites. Serpentinites sampled during ODP cruise 209 were compared with serpentinites from New Caledonia. The ODP209 serpentinites were serpentinised by modified seawater in a shallow hydrothermal seafloor setting. The New Caledonia serpentinites were serpentinised in a mantle wedge setting by slab-derived fluids, with possible contributions from oceanic serpentinisation and post-obduction serpentinisation. Petrological, whole rock and mineralogical analyses were combined to compare the two sample sets. Petrologically, the evolution of serpentinisation was close to identical in the two environments. However, more oxidised iron, Cl, S and C is present in serpentine from the ODP209 serpentinites relative to the New Caledonia serpentinites. Given these observations, the use of serpentinites from different geodynamic settings as a proxy for abyssal serpentinites from spreading settings must be undertaken with caution.

Middle to Late Jurassic Tectonic Evolution of the Klamath Mountains, California-Oregon

Science.gov (United States)

Harper, Gregory D.; Wright, James E.

1984-12-01

The geochronology, stratigraphy, and spatial relationships of Middle and Late Jurassic terranes of the Klamath Mountains strongly suggest that they were formed in a single west-facing magmatic arc built upon older accreted terranes. A Middle Jurassic arc complex is represented by the volcanic rocks of the western Hayfork terrane and consanguineous dioritic to peridotitic plutons. New U/Pb zircon dates indicate that the Middle Jurassic plutonic belt was active from 159 to 174 Ma and is much more extensive than previously thought. This plutonic belt became inactive just as the 157 Ma Josephine ophiolite, which lies west and structurally below the Middle Jurassic arc, was generated. Late Jurassic volcanic and plutonic arc rocks (Rogue Formation and Chetco intrusive complex) lie outboard and structurally beneath the Josephine ophiolite; U/Pb and K/Ar age data indicate that this arc complex is coeval with the Josephine ophiolite. Both the Late Jurassic arc complex and the Josephine ophiolite are overlain by the "Galice Formation," a Late Jurassic flysch sequence, and are intruded by 150 Ma dikes and sills. The following tectonic model is presented that accounts for the age and distribution of these terranes: a Middle Jurassic arc built on older accreted terranes undergoes rifting at 160 Ma, resulting in formation of a remnant arc/back-arc basin/island arc triad. This system collapsed during the Late Jurassic Nevadan Orogeny (150 Ma) and was strongly deformed and stacked into a series of east-dipping thrust sheets. Arc magmatism was active both before and after the Nevadan Orogeny, but virtually ceased at 140 Ma.

Central presbycusis: an emerging view.

Science.gov (United States)

Gates, George A

2012-07-01

Age-related dysfunction of the central auditory system (central presbycusis) is common but rarely looked for by those who provide aural rehabilitation. Patients who complain of difficulty hearing in noise--the key symptom of central presbycusis--are generally disadvantaged with conventional rehabilitation. This symptom should be documented with commercially available speech-in-noise tests, which use materials that are uncomplicated to administer. Those patients who perform poorly on such tests should have a customized rehabilitation program aimed at optimizing their remaining communication abilities. Otolaryngologists who provide auditory rehabilitation may wish to consider expanding their practices to meet the communication needs of older patients with central presbycusis. Central presbycusis is an emerging area for basic and clinical research in auditory neurotology, particularly in the relation of cognitive dysfunction to impaired auditory processing.

Central Diffraction in ALICE

CERN Document Server

Schicker, R

2012-01-01

The ALICE experiment at the Large Hadron Collider (LHC) at CERN consists of a central barrel, a muon spectrometer and of additional detectors for trigger and event classification purposes. The low transverse momentum threshold of the central barrel gives ALICE a unique opportunity to study the low mass sector of central production at the LHC. I will report on first analysis results of meson production in double gap events in minimum-bias proton-proton collisions at sqrt{s} = 7 TeV, and will describe a dedicated double gap trigger for future data taking.

Late Eocene Uplift of the Al Hajar Mountains, Oman, Supported by Stratigraphy and Low-Temperature Thermochronology

Science.gov (United States)

Hansman, Reuben J.; Ring, Uwe; Thomson, Stuart N.; den Brok, Bas; Stübner, Konstanze

2017-12-01

Uplift of the Al Hajar Mountains in Oman has been related to either Late Cretaceous ophiolite obduction or the Neogene Zagros collision. To test these hypotheses, the cooling of the central Al Hajar Mountains is constrained by 10 apatite (U-Th)/He (AHe), 15 fission track (AFT), and four zircon (U-Th)/He (ZHe) sample ages. These data show differential cooling between the two major structural culminations of the mountains. In the 3 km high Jabal Akhdar culmination AHe single-grain ages range between 39 ± 2 Ma and 10 ± 1 Ma (2σ errors), AFT ages range from 51 ± 8 Ma to 32 ± 4 Ma, and ZHe single-grain ages range from 62 ± 3 Ma to 39 ± 2 Ma. In the 2 km high Saih Hatat culmination AHe ages range from 26 ± 4 to 12 ± 4 Ma, AFT ages from 73 ± 19 Ma to 57 ± 8 Ma, and ZHe single-grain ages from 81 ± 4 Ma to 58 ± 3 Ma. Thermal modeling demonstrates that cooling associated with uplift and erosion initiated at 40 Ma, indicating that uplift occurred 30 Myr after ophiolite obduction and at least 10 Myr before the Zagros collision. Therefore, this uplift cannot be related to either event. We propose that crustal thickening supporting the topography of the Al Hajar Mountains was caused by a slowdown of Makran subduction and that north Oman took up the residual fraction of N-S convergence between Arabia and Eurasia.

Central control of body temperature.

Science.gov (United States)

Morrison, Shaun F

2016-01-01

Central neural circuits orchestrate the behavioral and autonomic repertoire that maintains body temperature during environmental temperature challenges and alters body temperature during the inflammatory response and behavioral states and in response to declining energy homeostasis. This review summarizes the central nervous system circuit mechanisms controlling the principal thermoeffectors for body temperature regulation: cutaneous vasoconstriction regulating heat loss and shivering and brown adipose tissue for thermogenesis. The activation of these thermoeffectors is regulated by parallel but distinct efferent pathways within the central nervous system that share a common peripheral thermal sensory input. The model for the neural circuit mechanism underlying central thermoregulatory control provides a useful platform for further understanding of the functional organization of central thermoregulation, for elucidating the hypothalamic circuitry and neurotransmitters involved in body temperature regulation, and for the discovery of novel therapeutic approaches to modulating body temperature and energy homeostasis.

A global central banker competency model

Directory of Open Access Journals (Sweden)

David W. Brits

2014-07-01

Full Text Available Orientation: No comprehensive, integrated competency model exists for central bankers. Due to the importance of central banks in the context of the ongoing global financial crisis, it was deemed necessary to design and validate such a model. Research purpose: To craft and validate a comprehensive, integrated global central banker competency model (GCBCM and to assess whether central banks using the GCBCM for training have a higher global influence. Motivation for the study: Limited consensus exists globally about what constitutes a ‘competent’ central banker. A quantitatively validated GCBCM would make a significant contribution to enhancing central banker effectiveness, and also provide a solid foundation for effective people management. Research approach, design and method: A blended quantitative and qualitative research approach was taken. Two sets of hypotheses were tested regarding the relationships between the GCBCM and the training offered, using the model on the one hand, and a central bank’s global influence on the other. Main findings: The GCBCM was generally accepted across all participating central banks globally, although some differences were found between central banks with higher and lower global influence. The actual training offered by central banks in terms of the model, however, is generally limited to technical-functional skills. The GCBCM is therefore at present predominantly aspirational. Significant differences were found regarding the training offered. Practical/managerial implications: By adopting the GCBCM, central banks would be able to develop organisation-specific competency models in order to enhance their organisational capabilities and play their increasingly important global role more effectively. Contribution: A generic conceptual framework for the crafting of a competency model with evaluation criteria was developed. A GCBCM was quantitatively validated.

CENTRAL BANKING IN THE NEW ERA

Directory of Open Access Journals (Sweden)

Bilal Bagis

2017-12-01

Full Text Available This paper analyzes the evolution of central banking, and in particular the American experience of central banking. It provides projections for the future of central banking in the new era of post 2008. The paper initially demonstrates recent improvements in the financial and banking sectors, regulations and different measures of monetary and financial rules both in the USA and the rest of the advanced economies. Then, it claims institutions, such as central banks, will gain new objectives and more significance in this new era and thus will be given new roles, over time and along with the improvements and deepening in the financial system. The paper argues centuries long central bank evolution is not complete yet and that more objectives should be expected to come forward. In that line, there is need for a shift in the conventional policy measures. New trends in central banking such as the helicopter money, popular nominal GDP targeting regime and the retro developmental central banking are all critically analyzed. The paper provides a breakdown of financial development and central banking activities in a historical context and provides a rationale and a new basis for possible future innovations.

Actual versus perceived central bank transparency: the case of the European Central Bank

NARCIS (Netherlands)

van der Cruijsen, C.; Eijffinger, S.

2008-01-01

Central banks have become more and more transparent about their monetary policy making process. In the central bank transparency literature the distinction between actual and perceived transparency is often lacking. However, as perceptions are crucial for the actions of economic agents this

Optimal Central Bank Transparency

NARCIS (Netherlands)

van der Cruijsen, C.A.B.; Eijffinger, S.C.W.; Hoogduin, L.H.

2008-01-01

Should central banks increase their degree of transparency any further? We show that there is likely to be an optimal intermediate degree of central bank transparency. Up to this optimum more transparency is desirable: it improves the quality of private sector inflation forecasts. But beyond the

Optimal central bank transparency

NARCIS (Netherlands)

van der Cruijsen, C.A.B.; Eijffinger, S.C.W.; Hoogduin, L.

2008-01-01

Should central banks increase their degree of transparency any further? We show that there is likely to be an optimal intermediate degree of central bank transparency. Up to this optimum more transparency is desirable: it improves the quality of private sector inflation forecasts. But beyond the

Optimal central bank transparency

NARCIS (Netherlands)

van der Cruijsen, C.A.B.; Eijffinger, S.C.W.; Hoogduin, L.H.

2010-01-01

Should central banks increase their degree of transparency any further? We show that there is likely to be an optimal intermediate degree of central bank transparency. Up to this optimum more transparency is desirable: it improves the quality of private sector inflation forecasts. But beyond the

Approximating centrality in evolving graphs: toward sublinearity

Science.gov (United States)

Priest, Benjamin W.; Cybenko, George

2017-05-01

The identification of important nodes is a ubiquitous problem in the analysis of social networks. Centrality indices (such as degree centrality, closeness centrality, betweenness centrality, PageRank, and others) are used across many domains to accomplish this task. However, the computation of such indices is expensive on large graphs. Moreover, evolving graphs are becoming increasingly important in many applications. It is therefore desirable to develop on-line algorithms that can approximate centrality measures using memory sublinear in the size of the graph. We discuss the challenges facing the semi-streaming computation of many centrality indices. In particular, we apply recent advances in the streaming and sketching literature to provide a preliminary streaming approximation algorithm for degree centrality utilizing CountSketch and a multi-pass semi-streaming approximation algorithm for closeness centrality leveraging a spanner obtained through iteratively sketching the vertex-edge adjacency matrix. We also discuss possible ways forward for approximating betweenness centrality, as well as spectral measures of centrality. We provide a preliminary result using sketched low-rank approximations to approximate the output of the HITS algorithm.

Central venous pressure monitoring via peripherally or centrally inserted central catheters: a systematic review and meta-analysis.

Science.gov (United States)

Sanfilippo, Filippo; Noto, Alberto; Martucci, Gennaro; Farbo, Marco; Burgio, Gaetano; Biasucci, Daniele G

2017-07-14

The central venous pressure (CVP) is the most commonly used static marker of preload for guiding fluid therapy in critically ill patients, though its usefulness remains controversial. Centrally inserted central catheters (CICCs) are the gold-standard devices for CVP monitoring but peripherally inserted central catheters (PICCs) may represent a valid alternative. We undertook a systematic review and meta-analysis with the aim to investigate whether the difference between PICC- and CICC-measured CVP is not significant. We searched for clinical studies published in PubMed and EMBASE databases from inception until December 21st 2016. We included studies providing data on paired and simultaneous CVP measurement from PICCs and CICCs. We conducted two analyses on the values of CVP, the first one according to the total number of CVP assessments, the second one considering the number of patients recruited. Four studies matched the inclusion criteria, but only three of them provided data for the meta-analyses. Both analyses showed non-significant differences between PICC-measured and CICC-measured CVP: 1489 paired simultaneous CVP assessments (MD 0.16, 95%CI -0.14, 0.45, p = 0.30) on a total of 57 patients (MD 0.22, 95%CI -1.46, 1.91, p = 0.80). Both analyses showed no heterogeneity (I2 = 0%). Available evidence supports that CVP monitoring with PICCs is accurate and reproduces similar values to those obtained from CICCs. The possibility to monitor CVP should not be used among clinical criteria for preferring a CICC over a PICC line.

Controlling centrality in complex networks

Science.gov (United States)

Nicosia, V.; Criado, R.; Romance, M.; Russo, G.; Latora, V.

2012-01-01

Spectral centrality measures allow to identify influential individuals in social groups, to rank Web pages by popularity, and even to determine the impact of scientific researches. The centrality score of a node within a network crucially depends on the entire pattern of connections, so that the usual approach is to compute node centralities once the network structure is assigned. We face here with the inverse problem, that is, we study how to modify the centrality scores of the nodes by acting on the structure of a given network. We show that there exist particular subsets of nodes, called controlling sets, which can assign any prescribed set of centrality values to all the nodes of a graph, by cooperatively tuning the weights of their out-going links. We found that many large networks from the real world have surprisingly small controlling sets, containing even less than 5 – 10% of the nodes. PMID:22355732

EIGENVECTOR-BASED CENTRALITY MEASURES FOR TEMPORAL NETWORKS*

Science.gov (United States)

TAYLOR, DANE; MYERS, SEAN A.; CLAUSET, AARON; PORTER, MASON A.; MUCHA, PETER J.

2017-01-01

Numerous centrality measures have been developed to quantify the importances of nodes in time-independent networks, and many of them can be expressed as the leading eigenvector of some matrix. With the increasing availability of network data that changes in time, it is important to extend such eigenvector-based centrality measures to time-dependent networks. In this paper, we introduce a principled generalization of network centrality measures that is valid for any eigenvector-based centrality. We consider a temporal network with N nodes as a sequence of T layers that describe the network during different time windows, and we couple centrality matrices for the layers into a supra-centrality matrix of size NT × NT whose dominant eigenvector gives the centrality of each node i at each time t. We refer to this eigenvector and its components as a joint centrality, as it reflects the importances of both the node i and the time layer t. We also introduce the concepts of marginal and conditional centralities, which facilitate the study of centrality trajectories over time. We find that the strength of coupling between layers is important for determining multiscale properties of centrality, such as localization phenomena and the time scale of centrality changes. In the strong-coupling regime, we derive expressions for time-averaged centralities, which are given by the zeroth-order terms of a singular perturbation expansion. We also study first-order terms to obtain first-order-mover scores, which concisely describe the magnitude of nodes’ centrality changes over time. As examples, we apply our method to three empirical temporal networks: the United States Ph.D. exchange in mathematics, costarring relationships among top-billed actors during the Golden Age of Hollywood, and citations of decisions from the United States Supreme Court. PMID:29046619

Central gain control in tinnitus and hyperacusis

Directory of Open Access Journals (Sweden)

Benjamin D Auerbach

2014-10-01

Full Text Available Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders.

Central Gain Control in Tinnitus and Hyperacusis

Science.gov (United States)

Auerbach, Benjamin D.; Rodrigues, Paulo V.; Salvi, Richard J.

2014-01-01

Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders. PMID:25386157

Granuloma central de células gigantes Giant cells central granuloma

Directory of Open Access Journals (Sweden)

Ayelén María Portelles Massó

2011-03-01

Full Text Available El granuloma reparativo central de células gigantes es una lesión proliferativa no neoplásica de etiología desconocida. Se presenta un paciente masculino de 40 años de edad, portador de prótesis parcial superior. Fue remitido al Servicio de Cirugía Maxilofacial del Hospital "V. I. Lenin" por presentar aumento de volumen en reborde alveolar superior, de color rojo grisáceo y que provocaba expansión de corticales óseas. Una vez analizados los exámenes clínicos, radiográficos e histopatológicos se diagnosticó un granuloma reparativo central de células gigantes Se realizó exéresis quirúrgica de la lesión y extracción de dientes adyacentes con una evolución satisfactoria sin señales de recidivas luego de tres años del tratamiento. El granuloma reparativo central de células gigantes se presentó como respuesta a un trauma. La correcta interpretación de los datos clínicos, radiográficos e histopatológicos nos permitió llegar al correcto diagnóstico y plan de tratamiento.Giant-cell central reparative granuloma is non neoplastic proliferative lesion of unknown etiology. We report a 40 years old male patient who was admitted at the Maxillofacial Service of the "V. I. Lenin" Hospital. The patient had partial upper prosthesis and was complaining of red-grey volume increase lesion in upper alveolar ridge which led to the expansion of cortical bone. Having analyzed clinical, radiographic and histopathological findings the case was concluded as a giant-cell central reparative granuloma. Surgical exeresis and adjunct tooth extraction were done. After three years of treatment, satisfactory follow up without recurrence is reported.

AAPT Diagnostic Criteria for Central Neuropathic Pain

DEFF Research Database (Denmark)

Widerstrom-Noga, Eva; Loeser, John D.; Jensen, Troels Staehelin

2017-01-01

Central neuropathic pain, which is pain caused by a lesion or disease of the central somatosensory nervous system, is a serious consequence of spinal cord injury, stroke, multiple sclerosis, and other conditions affecting the central nervous system. A collaborative effort between the Analgesic....... This article focuses on central neuropathic pain associated with spinal cord injury, stroke, and multiple sclerosis, but the AAPT framework can be extended to central pain due to other causes such as traumatic brain injury. The classification of central neuropathic pain is organized according to the AAPT...

Idiopathic central diabetes Insipidus.

Science.gov (United States)

Grace, Mary; Balachandran, Venu; Menon, Sooraj

2011-10-01

Idiopathic central diabetes insipidus (CDI) is a rare disorder characterized clinically by polyuria and polydipsia, and an abnormal urinary concentration without any identified etiology. We report a case of central diabetes insipidus in a 60-year-old lady in the absence of secondary causes like trauma, infection, and infiltrative disorders of brain.

Central Diabetes Insipidus, Central Hypothyroidism, Renal Tubular ...

African Journals Online (AJOL)

readmitted to the hospital because of jaundice and failure to thrive, for which he was investigated and diagnosed to have central congenital hypothyroidism. Shortly thereafter, he was admitted to our institute with a history of vomiting, decreased oral intake, polyuria, and dehydration having lasted 5 days. He was investigated ...

Early Archean serpentine mud volcanoes at Isua, Greenland, as a niche for early life.

Science.gov (United States)

Pons, Marie-Laure; Quitté, Ghylaine; Fujii, Toshiyuki; Rosing, Minik T; Reynard, Bruno; Moynier, Frederic; Douchet, Chantal; Albarède, Francis

2011-10-25

The Isua Supracrustal Belt, Greenland, of Early Archean age (3.81-3.70 Ga) represents the oldest crustal segment on Earth. Its complex lithology comprises an ophiolite-like unit and volcanic rocks reminiscent of boninites, which tie Isua supracrustals to an island arc environment. We here present zinc (Zn) isotope compositions measured on serpentinites and other rocks from the Isua supracrustal sequence and on serpentinites from modern ophiolites, midocean ridges, and the Mariana forearc. In stark contrast to modern midocean ridge and ophiolite serpentinites, Zn in Isua and Mariana serpentinites is markedly depleted in heavy isotopes with respect to the igneous average. Based on recent results of Zn isotope fractionation between coexisting species in solution, the Isua serpentinites were permeated by carbonate-rich, high-pH hydrothermal solutions at medium temperature (100-300 °C). Zinc isotopes therefore stand out as a pH meter for fossil hydrothermal solutions. The geochemical features of the Isua fluids resemble the interstitial fluids sampled in the mud volcano serpentinites of the Mariana forearc. The reduced character and the high pH inferred for these fluids make Archean serpentine mud volcanoes a particularly favorable setting for the early stabilization of amino acids.

Central bank independence and inflation revisited

NARCIS (Netherlands)

Klomp, Jeroen; de Haan, Jakob

We re-examine the relationship between central bank independence (CBI), proxied by the central bank governor's turnover rate and an indicator based on central bank laws in place, and inflation using a random coefficient model with the Hildreth-Houck estimator for more than 100 countries in the

Central bank independence and inflation revisited

NARCIS (Netherlands)

Klomp, J.G.; Haan, de J.

2010-01-01

We re-examine the relationship between central bank independence (CBI), proxied by the central bank governor's turnover rate and an indicator based on central bank laws in place, and inflation using a random coefficient model with the Hildreth-Houck estimator for more than 100 countries in the

Performance contracting in central government in Denmark

DEFF Research Database (Denmark)

Kristiansen, Mads Bøge

2015-01-01

) are observed across central government agencies, when the content of the performance contracts is compared. This makes it interesting to examine how variation in the content of the performance contracts across agencies can be explained? Based on a broad theoretical framework in which variation......This paper looks into performance contracting in Danish central government. Management by Objectives and Results (MBOR) was adopted in central government in Denmark during the 1980s and early 1990s. In 1991, performance contracts between parent ministries and their agencies were introduced...... in Danish central government. Since their introduction, performance contracts have become central elements in the steering and management of agencies in central government in Denmark, and today they are nearly universally adopted in central government. In Denmark, the Ministry of Finance is responsible...

Central Bank independence

Directory of Open Access Journals (Sweden)

Vasile DEDU

2012-08-01

Full Text Available In this paper we present the key aspects regarding central bank’s independence. Most economists consider that the factor which positively influences the efficiency of monetary policy measures is the high independence of the central bank. We determined that the National Bank of Romania (NBR has a high degree of independence. NBR has both goal and instrument independence. We also consider that the hike of NBR’s independence played an important role in the significant disinflation process, as headline inflation dropped inside the targeted band of 3% ± 1 percentage point recently.

Central Venous Access

International Nuclear Information System (INIS)

Ganeshan, Arul; Warakaulle, Dinuke R.; Uberoi, Raman

2007-01-01

Central venous access plays an important role in the management of an ever-increasing population of patients ranging from those that are critically ill to patients with difficult clinical access. Interventional radiologists are key in delivering this service and should be familiar with the wide range of techniques and catheters now available to them. A comprehensive description of these catheters with regard to indications, technical aspects of catheterization, success rates, and associated early and late complications, as well as a review of various published guidelines on central venous catheter insertion are given in this article

Risk Premium and Central Bank Intervention

OpenAIRE

Pinar Ozlu

2006-01-01

This study examines the relation between the risk premium and central bank intervention. Forward rates are calculated for the Turkish Lira-USD exchange market and then the effect of central bank intervention on the risk premium is estimated. Using high quality daily intervention data from the Central Bank of Turkey as well as implied forward rates, an MA (21)-GARCH (1,1) model is estimated. Both purchases and sales of US dollars by the Central Bank of Turkey appear to have no effect on the si...

Big Data and central banks

OpenAIRE

David Bholat

2015-01-01

This commentary recaps a Centre for Central Banking Studies event held at the Bank of England on 2–3 July 2014. The article covers three main points. First, it situates the Centre for Central Banking Studies event within the context of the Bank’s Strategic Plan and initiatives. Second, it summarises and reflects on major themes from the event. Third, the article links central banks’ emerging interest in Big Data approaches with their broader uptake by other economic agents.

Big Data and central banks

Directory of Open Access Journals (Sweden)

David Bholat

2015-04-01

Full Text Available This commentary recaps a Centre for Central Banking Studies event held at the Bank of England on 2–3 July 2014. The article covers three main points. First, it situates the Centre for Central Banking Studies event within the context of the Bank’s Strategic Plan and initiatives. Second, it summarises and reflects on major themes from the event. Third, the article links central banks’ emerging interest in Big Data approaches with their broader uptake by other economic agents.

Central Bank Independence, Centralization of Wage Bargaining, Inflation and Unemployment - Theory and Some Evidence

NARCIS (Netherlands)

Cukierman, A.; Lippi, F.

1998-01-01

This paper proposes a conceptual framework to investigate the effects of central bank independence, of the degree of centralization of wage bargaining and of the interaction between those institutional variables, on real wages, unemployment and inflation, in a framework in which unions are averse to

Central Asia's raging waters the prospects of water conflict in Central Asia

OpenAIRE

Hartman, William B.

2007-01-01

This thesis examines the prospects of conflict caused by water scarcity in Central Asia. The thesis analyzes the three most recent political eras of Central Asia, Tsarist Russia, the Soviet Union and independence, utilizing indicators of water tensions including: water quality, water quantity, the management of water for multiple uses, the political divisions and geopolitical setting, state institutions and national water ethos. Although water is not likely to be the sole cause of a majo...

Central blood pressure and chronic kidney disease

Science.gov (United States)

Ohno, Yoichi; Kanno, Yoshihiko; Takenaka, Tsuneo

2016-01-01

In this review, we focused on the relationship between central blood pressure and chronic kidney diseases (CKD). Wave reflection is a major mechanism that determines central blood pressure in patients with CKD. Recent medical technology advances have enabled non-invasive central blood pressure measurements. Clinical trials have demonstrated that compared with brachial blood pressure, central blood pressure is a stronger risk factor for cardiovascular (CV) and renal diseases. CKD is characterized by a diminished renal autoregulatory ability, an augmented direct transmission of systemic blood pressure to glomeruli, and an increase in proteinuria. Any elevation in central blood pressure accelerates CKD progression. In the kidney, interstitial inflammation induces oxidative stress to handle proteinuria. Oxidative stress facilitates atherogenesis, increases arterial stiffness and central blood pressure, and worsens the CV prognosis in patients with CKD. A vicious cycle exists between CKD and central blood pressure. To stop this cycle, vasodilator antihypertensive drugs and statins can reduce central blood pressure and oxidative stress. Even in early-stage CKD, mineral and bone disorders (MBD) may develop. MBD promotes oxidative stress, arteriosclerosis, and elevated central blood pressure in patients with CKD. Early intervention or prevention seems necessary to maintain vascular health in patients with CKD. PMID:26788468

Payments and Central Bank Policy

DEFF Research Database (Denmark)

Korsgaard, Søren

This thesis consists of three chapters. The rst, "Paying for Payments", examines the role of interchange fees in payment card networks. The second, "Bank Liquidity and the Interbank Market" (co-authored with Mikael Reimer Jensen), investigates how banks' liquidity holdings at the central bank a ect...... outcomes in the money market. The third, "Collateralized Lending and Central Bank Collateral Policy", considers the emergence of credit constraints under collateralized lending, and how central banks use collateral policy to mitigate these constraints. While the chapters can be read independently......, they share common themes. Each chapter is concerned with payments in one way or another, each is concerned with the e ciency of market outcomes, and, to the extent that there is scope for improving these outcomes, each discusses the appropriate role for policy, in particular central bank policy....

Do central bank law reforms affect the term in office of central bank governors?

NARCIS (Netherlands)

Klomp, J.G.; de Haan, J.

In this paper we confirm the hypothesis that central bank independence reforms reduce the likelihood that a central bank governor will be replaced. However, the strength of this effect depends on the rule of law and the degree of political polarization. (c) 2009 Elsevier B.V. All rights reserved.

Current status of laparoscopic central pancreatectomy

Directory of Open Access Journals (Sweden)

CAO Yang

2017-04-01

Full Text Available Central pancreatectomy is an ideal surgical procedure for the treatment of benign or low-grade malignant tumors in the pancreatic neck or the proximal body of the pancreas, and it can preserve more normal pancreatic tissue in order to reduce the incidence of endocrine and exocrine insufficiency after surgery. Although some clinical studies have demonstrated the feasibility and safety of this procedure, laparoscopic central pancreatectomy was technically challenging with a few number of cases. This article reviews the current status of laparoscopic central pancreatectomy and introduces our clinical experience of laparoscopic central pancreatectomy and pancreaticojejunostomy.

Central cell confinement in MFTF-B

International Nuclear Information System (INIS)

Jong, R.A.

1981-01-01

The point code TANDEM has been used to survey the range of plasma parameters which can be attained in MFTF-B. The code solves for the electron and ion densities and temperatures in the central cell, yin-yang, barrier, and A-cell regions as well as the plasma potential in each region. In these studies, the A-cell sloshing ion beams were fixed while the neutral beams in the yin-yang and central cell, the gas feed in the central cell, and the applied ECRH power β, central cell ion density and temperature, and the confining potential are discussed

Central Hypothyroidism in Miniature Schnauzers

NARCIS (Netherlands)

Voorbij, Annemarie M W Y; Leegwater, Peter A J; Buijtels, Jenny J C W M; Daminet, Sylvie; Kooistra, Hans S

2016-01-01

BACKGROUND: Primary hypothyroidism is a common endocrinopathy in dogs. In contrast, central hypothyroidism is rare in this species. OBJECTIVES: The objective of this article is to describe the occurrence and clinical presentation of central hypothyroidism in Miniature Schnauzers. Additionally, the

Complications of central venous stenosis due to permanent central venous catheters in children on hemodialysis.

Science.gov (United States)

Rinat, Choni; Ben-Shalom, Efrat; Becker-Cohen, Rachel; Feinstein, Sofia; Frishberg, Yaacov

2014-11-01

Central venous catheters are frequently used as access for hemodialysis (HD) in children. One of the known complications is central venous stenosis. Although this complication is not rare, it is often asymptomatic and therefore unacknowledged. Superior vena cava (SVC) stenosis is obviously suspected in the presence of upper body edema, but several other signs and symptoms are often unrecognized as being part of this syndrome. We describe four patients with various manifestations of central venous stenosis and SVC syndrome. These sometimes life- or organ-threatening conditions include obstructive sleep apnea, unresolving stridor, increased intracranial pressure, increased intraocular pressure, right-sided pleural effusion, protein-losing enteropathy and lymphadenopathy. The temporal relationship of these complications associated with the use of central venous catheters and documentation of venous stenosis, together with their resolution after alleviation of high venous pressure, points to a causal role. We suggest pathophysiological mechanisms for the formation of each of these complications. In patients with occlusion of the SVC, various unexpected clinical entities can be caused by high central venous pressure. As often the etiology is not obvious, a high index of suspicion is needed as in some cases prompt alleviation of the high pressure is mandatory.

Source and tectonic implications of tonalite-trondhjemite magmatism in the Klamath Mountains

Science.gov (United States)

Barnes, C.G.; Petersen, S.W.; Kistler, R.W.; Murray, R.; Kays, M.A.

1996-01-01

In the Klamath Mountains, voluminous tonalite-trondhjemite magmatism was characteristic of a short period of time from about 144 to 136 Ma (Early Cretaceous). It occurred about 5 to l0 m.y. after the ??? 165 to 159 Ma Josephine ophiolite was thrust beneath older parts of the province during the Nevadan orogeny (thrusting from ??? 155 to 148 Ma). The magmatism also corresponds to a period of slow or no subduction. Most of the plutons crop out in the south-central Klamath Mountains in California, but one occurs in Oregon at the northern end of the province. Compositionally extended members of the suite consist of precursor gabbroic to dioritic rocks followed by later, more voluminous tonalitic and trondhjemitic intrusions. Most plutons consist almost entirely of tonalite and trondhjemite. Poorlydefined concentric zoning is common. Tonalitic rocks are typically of the Iow-Al type but trondhjemites are generally of the high-Al type, even those that occur in the same pluton as low-Al tonalite??. The suite is characterized by low abundances of K2O, Rb, Zr, and heavy rare earth elements. Sr contents are generally moderate ( ???450 ppm) by comparison with Sr-rich arc lavas interpreted to be slab melts (up to 2000 ppm). Initial 87Sr/ 86Sr, ??18O, and ??Nd are typical of mantle-derived magmas or of crustally-derived magmas with a metabasic source. Compositional variation within plutons can be modeled by variable degrees of partial melting of a heterogeneous metabasaltic source (transitional mid-ocean ridge to island arc basalt), but not by fractional crystallyzation of a basaltic parent. Melting models require a residual assemblage of clinopyroxene+garnet??plagioclase??amphibole; residual plagioclase suggests a deep crustal origin rather than melting of a subducted slab. Such models are consistent with the metabasic part of the Josephine ophiolite as the source. Because the Josephine ophiolite was at low T during Nevadan thrusting, an external heat source was probably

Thermotectonic evolution of the Apuseni mountains (Romania) based on structural and geothermochronological data

Science.gov (United States)

Reiser, M. K.; Fügenschuh, B.; Schuster, R.

2012-04-01

The Apuseni Mountains in Romania take a central position in the Alpine Carpathian Dinaride system between the Pannonian basin in the West and the Transylvanian basin in the East. Following the final Mid-Cretaceous obduction of the East Vardar ophiolite a NW-vergent nappe stack formed, which involves from bottom to top: Tisza- (Bihor and Codru) and Dacia-derived (Biharia) units, overlain by the South Apuseni or Transylvanian ophiolite belt (see Schmid et al, 2008). This study tries to provide new and additional information on the complex structural and metamorphic evolution of these units, from the onset of obduction during Jurassic times, to the (final?) exhumation processes observed during the Eocene (according to Merten, 2011). Based on observed stretching lineations, kinematic indicators such as porphyroclasts, shearbands etc. were analyzed to establish a relative chronological order of deformation and tectonic transport. Microstructural studies provided additional data on the relative succession of events and the relevant synkinematic temperatures. A thermochronological study, based on the integration of newly aquired Rb-Sr, Sm-Nd, Ar-Ar and fission track ages with existing data allowed the construction of a time-temperature deformation path. Our data indicate three major events, a Late Jurassic-Earliest Cretaceous exhumation event, which cannot be directly constrained by structural data so far. Yet the position of the Transsylvanian ophiolites tectonically overlying the Biharia unit as well as distinct thermochronological data are self-explaining. The second event ("Austrian Phase" in local nomenclature), documented by structural and thermochronological data, is related to the top to the NE thrusting (i.e. in present-day coordinates) of Tisza over Dacia during the Mid-Cretaceous. This penetrative event in the Biharia unit is overprinted at the contact between nappes by a third, top to the NW event during the Turonian, which relates to the NW directed

Accountability of central banks: aspects and quantification

Directory of Open Access Journals (Sweden)

J. DE HAAN

1999-06-01

Full Text Available The work examines the relationship between central bank independence and accountability. The authors do this by using an indicator for central bank accountability based on the laws of 16 central banks. Central bank accountability is identified as having three distinct features, namely, the explicit definition and ranking of the objectives of monetary policy, the transparency of the actual monetary policy, and the final responsibility to monetary policy.

Colloquium on Central Asia

International Nuclear Information System (INIS)

2005-01-01

This colloquium on Azerbaijan was organized by the direction of international relations of the French Senate and the French center of foreign trade (CFCE). This document gathers the interventions of the participants and the debates with the audience following these interventions. The topics treated concern: - the present day political-economical situation of Central Asia countries (problem of borders, relations with Russia and China); - the economies of Central Asia countries: short term problems and medium-term perspectives; - the relations with the European Union (political, economical, trade and investments, perspectives); - the European energy stakes of Caspian sea (oil and gas reserves, development of hydrocarbon resources, exploitation and transport constraints, stakes for Europe and France); - TotalFinaElf company in Central Asia (Kazakhstan, Azerbaijan, enclavement problem); - the economical impacts of the TRACECA pathway (Transport Corridor Europe Caucasus Asia). (J.S.)

The Naive Central Banker

Directory of Open Access Journals (Sweden)

Marcelo de Carvalho Griebeler

2015-09-01

Full Text Available There has been in some countries a trend of assigning other functions to central banks besides price stability. The most suggested function to be added to monetary authority’s obligations is to pursue economic growth or full employment. In this paper we characterize the behavior and analyse the optimal monetary policy of, what we call, a naive central banker. We describe the naive behavior as one that does face the inflation-unemployment trade-off, but it tries to minimize both variables simultaneously. Our findings, both under discretion and commitment, indicate that the naive central banker delivers lower expected inflation and inflation variance than the benchmark behavior whenever the economy is rigid enough. However, the degree of conservativeness also affects this result, such that the less conservative the naive policymaker, the more rigidity is necessary.

The central nervous system

International Nuclear Information System (INIS)

Holmes, R.A.

1984-01-01

The first section presents a comprehensive evaluation of radionuclide imaging of the central nervous system and provides a comparison of the detection accuracies of radionuclide imaging (RNI) and XCT in certain lesions, realizing that the XCT results may vary when radiocontrast or newer generation XCT scanners are used. Although conventional radionuclide imaging of the central nervous system has experienced no significant changes over the last 7 years except for mild refinements, a new section has been added on positron emission tomography (PET). Most positron radiopharmaceuticals passively cross the intact blood-brain barrier, and their localization has catalyzed renewed interest in our ability to metabolically study and obtain images of the central nervous system. The section on radionuclide cisternography has been rewritten to reflect present day practice and the wider application of XCT in describing conditions affecting the ventricular system

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

Science.gov (United States)

Azizi, Hossein; Hadi, Ayten; Asahara, Yoshihiro; Mohammad, Youssef Osman

2013-12-01

The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ɛ Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.

Report of the Central Tracking Group

International Nuclear Information System (INIS)

Cassel, D.G.; Hanson, G.G.

1986-10-01

Issues involved in building a realistic central tracking system for a general-purpose 4π detector for the SSC are addressed. Such a central tracking system must be capable of running at the full design luminosity of 10 33 cm -2 s -1 . Momentum measurement was required in a general-purpose 4π detector. Limitations on charged particle tracking detectors at the SSC imposed by rates and radiation damage are reviewed. Cell occupancy is the dominant constraint, which led us to the conclusion that only small cells, either wires or straw tubes, are suitable for a central tracking system at the SSC. Mechanical problems involved in building a central tracking system of either wires or straw tubes were studied, and our conclusion was that it is possible to build such a large central tracking system. Of course, a great deal of research and development is required. We also considered central tracking systems made of scintillating fibers or silicon microstrips, but our conclusion was that neither is a realistic candidate given the current state of technology. We began to work on computer simulation of a realistic central tracking system. Events from interesting physics processes at the SSC will be complex and will be further complicated by hits from out-of-time bunch crossings and multiple interactions within the same bunch crossing. Detailed computer simulations are needed to demonstrate that the pattern recognition and tracking problems can be solved

Centralized mouse repositories.

Science.gov (United States)

Donahue, Leah Rae; Hrabe de Angelis, Martin; Hagn, Michael; Franklin, Craig; Lloyd, K C Kent; Magnuson, Terry; McKerlie, Colin; Nakagata, Naomi; Obata, Yuichi; Read, Stuart; Wurst, Wolfgang; Hörlein, Andreas; Davisson, Muriel T

2012-10-01

Because the mouse is used so widely for biomedical research and the number of mouse models being generated is increasing rapidly, centralized repositories are essential if the valuable mouse strains and models that have been developed are to be securely preserved and fully exploited. Ensuring the ongoing availability of these mouse strains preserves the investment made in creating and characterizing them and creates a global resource of enormous value. The establishment of centralized mouse repositories around the world for distributing and archiving these resources has provided critical access to and preservation of these strains. This article describes the common and specialized activities provided by major mouse repositories around the world.

Building the foundations for a new central bank doctrine: Redefining central banks’ missions in the 21st century

Directory of Open Access Journals (Sweden)

Eric Pichet

2013-05-01

Full Text Available The 2007-2008 financial crisis demonstrated both the responsibilities that central bankers, alongside other actors, bear for turbulences of this kind as well as how economics can be used to provide central bankers and governments with the understanding and tools that they need to prevent the international financial system from collapsing. At the same time, central banks’ responses to the crisis have taken monetary policy into unknown territory. The paper’s first section diagnoses good and bad practice in post-crisis central banking; assesses the efficiency of pre-crisis doctrines; and identifies the dangers of actions exceeding certain limits. It specifically focuses on the European Central Bank’s much-debated intervention in certain peripheral bond markets, particularly Greece. The second section is more normative and lays the foundations for a social science perspective of how to manage modern central banks, an approach that draws on a variety of disciplines including economics, governance theory and management. This starts with a definition of the new doctrine and its underlying philosophy, followed by an identification of sound central banking practices (revolving around a few key concepts, notably inflation and financial stability. The missions and objectives of these practices are then defined (along with a choice of indicators, culminating in an exploration of which strategies and tools might be used in both normal and turbulent times. Lastly, a few concrete rules of governance are offered, built on the triptych of central banks’ independence, accountability and composition, with specific focus placed on the process for selecting governors fit to handle the new role that modern central banks are destined to assume in developed countries.

Central Bank independence in Latin America La independencia de la Banca Central en América Latina

Directory of Open Access Journals (Sweden)

Junguito Bonnet Roberto

1996-06-01

Full Text Available This article describes the origin and evolution of the central banks of Argentina, Brazil, Chile, Colombia, Mexico, and Venezuela, and analyzes their respective institutional structures. It also studies the contribution of the central bank to stabilization and the problems for maintaining this independence into the future.Este artículo describe el origen y la evolución de los Bancos Centrales de Argentina, Brasil, Chile, Colombia, México y Venezuela, y analiza sus respectivas estructruras institucionales. También estudia la contribución de la banca central a la estabilización y los problemas para que esta independencia se mantenga en el futuro.

The European Central Bank and the Eurosystem

OpenAIRE

Carol C. Bertaut

2002-01-01

The Eurosystem comprises the European Central Bank at its center as well as the national central banks of the twelve countries currently participating in monetary union. The European Central Bank was established in July 1998, six months before the beginning of Stage Three of economic and monetary union. Although decisions regarding monetary policy are made centrally by the Governing Council of the Eurosystem, the operational aspects of monetary policy-including open market operations, adminis...

Incidence of thrombosis in children with tunneled central venous access devices versus peripherally inserted central catheters (PICCs).

Science.gov (United States)

Kanin, Maralee; Young, Guy

2013-11-01

The recent proliferation of deep vein thrombosis in children has been attributed to the increased use of central venous catheters, specifically tunneled lines and peripherally inserted central catheters. A formal comparison of the incidence rate for deep vein thrombosis between tunneled lines and peripherally inserted central catheters has not been undertaken. Children inclusion. Data were extracted from the hospital discharge database which includes data on all procedures and up to 20 diagnoses per admission. Diagnoses and procedures were identified by International Classification of Disease, Ninth Revision coding. Patients were excluded if they received more than one central line. Data collected included type of central line, deep vein thrombosis event, and underlying medical illnesses classified according to chronic complex conditions. Over the seven year study period there was an overall rate of 73 deep vein thromboses per 10,000 hospital discharges. Of the 6915 eligible subjects, 181 had a deep vein thrombosis for an overall incidence rate of 2.6%. There were 152 thrombi (2.6%) in subjects with peripherally inserted central catheters and 29 thrombi (3.1%) in subjects with tunneled lines [OR=.83 (0.55, 1.29), p=0.38]. Despite the relative ease and simplicity of use of peripherally inserted central catheters leading to a substantial rise in their use, this study demonstrates that such lines pose a substantial risk for venous thrombosis and no difference in incidence was detected between such lines and tunneled lines. © 2013.

Dynamics-based centrality for directed networks.

Science.gov (United States)

Masuda, Naoki; Kori, Hiroshi

2010-11-01

Determining the relative importance of nodes in directed networks is important in, for example, ranking websites, publications, and sports teams, and for understanding signal flows in systems biology. A prevailing centrality measure in this respect is the PageRank. In this work, we focus on another class of centrality derived from the Laplacian of the network. We extend the Laplacian-based centrality, which has mainly been applied to strongly connected networks, to the case of general directed networks such that we can quantitatively compare arbitrary nodes. Toward this end, we adopt the idea used in the PageRank to introduce global connectivity between all the pairs of nodes with a certain strength. Numerical simulations are carried out on some networks. We also offer interpretations of the Laplacian-based centrality for general directed networks in terms of various dynamical and structural properties of networks. Importantly, the Laplacian-based centrality defined as the stationary density of the continuous-time random walk with random jumps is shown to be equivalent to the absorption probability of the random walk with sinks at each node but without random jumps. Similarly, the proposed centrality represents the importance of nodes in dynamics on the original network supplied with sinks but not with random jumps.

Community centrality and social science research.

Science.gov (United States)

Allman, Dan

2015-12-01

Community centrality is a growing requirement of social science. The field's research practices are increasingly expected to conform to prescribed relationships with the people studied. Expectations about community centrality influence scholarly activities. These expectations can pressure social scientists to adhere to models of community involvement that are immediate and that include community-based co-investigators, advisory boards, and liaisons. In this context, disregarding community centrality can be interpreted as failure. This paper considers evolving norms about the centrality of community in social science. It problematises community inclusion and discusses concerns about the impact of community centrality on incremental theory development, academic integrity, freedom of speech, and the value of liberal versus communitarian knowledge. Through the application of a constructivist approach, this paper argues that social science in which community is omitted or on the periphery is not failed science, because not all social science requires a community base to make a genuine and valuable contribution. The utility of community centrality is not necessarily universal across all social science pursuits. The practices of knowing within social science disciplines may be difficult to transfer to a community. These practices of knowing require degrees of specialisation and interest that not all communities may want or have.

Central banks: Paradise lost

OpenAIRE

Issing, Otmar

2012-01-01

The focus of the paper is to analyze how the concept behind central bank policy developed over time and how the recent financial crisis and its consequences will have an influence. While the principles of the institutional arrangement for central banks (independence, clear mandate, prohibition of monetary financing) are relevant as ever, pre- crisis consensus strategies of monetary policy have been revealed as flawed. The close monitoring of money and credit developments, a key lesson to be d...

Central European gas market perspectives

International Nuclear Information System (INIS)

Vanous, Jan

1999-01-01

This presentation deals with (1) Definition of the Central European market, (2) Factors driving up consumption of natural gas in Central and Eastern Europe, (3) Role of natural gas in regional energy consumption, (4) Position of natural gas in individual country markets, (5) Future sources of imported natural gas into the region. The Central European market are the eleven countries Albania, Bulgaria, Croatia, Czech Republic, Hungary, Macedonia, Poland, Romania, Serbia and Montenegro, Slovakia, and Slovenia, with a total population of 121 million. This market is comparable to combined France and Italy in terms of population, but only 30% of its size in terms of GDP

Close-binary central stars of planetary nebulae

International Nuclear Information System (INIS)

Bond, H.E.; Grauer, A.D.

1987-01-01

Recent observations of PN central stars identified as binary systems are reviewed. The theoretical significance of binary central stars is discussed, and the characteristics of UU Sge, V 477 Lyr, MT Ser, LSS 2018, VW Pyx, and the central star of HFG 1 are briefly summarized. All of these binaries are shown to have periods less than 1 day, and it is estimated that about 10 percent of all binary central stars are close binaries. 27 references

Central Station Design Options

DEFF Research Database (Denmark)

2011-01-01

. The work identifies the architecture, sizing and siting of prospective Central Stations in Denmark, which can be located at shopping centers, large car parking lots or gas stations. Central Stations are planned to be integrated in the Danish distribution grid. The Danish island of Bornholm, where a high...... overloading, more reference points might be necessary to represent various transformer loading levels. The subject of safety in Central Station is also addressed. A number of safety rules based on European standards apply to AC charging equipment up to 44 kW. The connection interlock and the automatic de......-energization are identified as fundamental requirements for safety in such a charging station. The connection interlock is a solution which ensures that no power is applied to the DC cable when the EV connector is not connected. The automatic de-energization device ensures that whenever a strain on the cable is detected, e...

48 CFR 52.204-7 - Central Contractor Registration.

Science.gov (United States)

2010-10-01

... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Central Contractor....204-7 Central Contractor Registration. As prescribed in 4.1105, use the following clause: Central Contractor Registration (APR 2008) (a) Definitions. As used in this clause— Central Contractor Registration...

Comparison of blood loss between using non central part cutting knee prosthesis and distal central part cutting.

Science.gov (United States)

Malairungsakul, Anan

2014-12-01

Patients who undergo knee replacement surgery may need to receive a blood transfusion due to blood loss during the operation. Therefore it was important to improve the design of knee implant operative procedures in an attempt to reduce the rate of blood loss. The present study aimed to compare the blood loss between two types of knee replacement surgery. This is a retrospective study in which 78 patients received cemented knee replacements in Phayao Hospital between October 2010 and March 2012. There were two types of surgical procedure: 1) using an implant position covering the end of the femoral bone without cutting into the central part of the distal femoral, 2) using an implant position covering the end of the femoral bone cutting the central part of the distal femoral. Blood loss, blood transfusion, hemoglobin and hematocrit were recorded preoperatively, immediately postsurgery and 48 hours after surgery. Findings revealed that the knee replacement surgery using the implant position covering the end of the femoral bone without cutting the central part of the distal femoral significantly lowered the rate of blood loss when compared to using the implant position covering the end of the femoral bone with central cutting of the distal femor. The average blood loss during the operation without cutting at the central part of distal femoral was 49.50 ± 11.11 mL; whereas the operation cutting the central part of the distal femoral was 58.50 ± 11.69 mL. As regards blood loss, the knee replacement surgery using the implant position covering the end ofthefemoral bone without cutting the central part of distal femor was better than using the implant position covering the end of the femoral bone cutting at the central part of the distal femor.

A new paradigm of modern central banking

Directory of Open Access Journals (Sweden)

Aleksandra Szunke

2013-05-01

Full Text Available The changes in the modern monetary policy, which took place at the beginning of the twenty-first century, in response to the global financial crisis led to the transformation of the place and the role of central banks. The strategic aim of the central monetary institutions has become preventing financial instability. So far, central banks have defined financial stability as a public good, which took care independently of other monetary purposes (Pyka, 2010. Unconventional monetary policy resulted in changes the global central banking. The aim of the study is to identify a new paradigm of the role and place of the central bank in the financial system and its new responsibilities, aimed at countering financial instability.

Central hypothyroidism - a neglected thyroid disorder.

Science.gov (United States)

Beck-Peccoz, Paolo; Rodari, Giulia; Giavoli, Claudia; Lania, Andrea

2017-10-01

Central hypothyroidism is a rare and heterogeneous disorder that is characterized by a defect in thyroid hormone secretion in an otherwise normal thyroid gland due to insufficient stimulation by TSH. The disease results from the abnormal function of the pituitary gland, the hypothalamus, or both. Moreover, central hypothyroidism can be isolated or combined with other pituitary hormone deficiencies, which are mostly acquired and are rarely congenital. The clinical manifestations of central hypothyroidism are usually milder than those observed in primary hypothyroidism. Obtaining a positive diagnosis for central hypothyroidism can be difficult from both a clinical and a biochemical perspective. The diagnosis of central hypothyroidism is based on low circulating levels of free T 4 in the presence of low to normal TSH concentrations. The correct diagnosis of both acquired (also termed sporadic) and congenital (also termed genetic) central hypothyroidism can be hindered by methodological interference in free T 4 or TSH measurements; routine utilization of total T 4 or T 3 measurements; concurrent systemic illness that is characterized by low levels of free T 4 and normal TSH concentrations; the use of the sole TSH-reflex strategy, which is the measurement of the sole level of TSH, without free T 4 , if levels of TSH are in the normal range; and the diagnosis of congenital hypothyroidism based on TSH analysis without the concomitant measurement of serum levels of T 4 . In this Review, we discuss current knowledge of the causes of central hypothyroidism, emphasizing possible pitfalls in the diagnosis and treatment of this disorder.

"Christofest" New Yorgi Central Parkis / Rael Artel

Index Scriptorium Estoniae

Artel, Rael, 1980-

2004-01-01

12. II 2005. a. avatakse Christo ja Jeanne-Claude'i keskkonnainstallatsioon "The Gates" New Yorgi Central Parkis. Paralleelselt toimub Metropolitan Muuseumis näitus "Christo and Jeanne-Claude : The Gates, Central Park, New York", kus eksponeeritakse Central Parki installatsiooni ettevalmistavaid materjale: joonistusi, diagramme, fotosid jne

Centrality metrics and localization in core-periphery networks

International Nuclear Information System (INIS)

Barucca, Paolo; Lillo, Fabrizio; Tantari, Daniele

2016-01-01

Two concepts of centrality have been defined in complex networks. The first considers the centrality of a node and many different metrics for it have been defined (e.g. eigenvector centrality, PageRank, non-backtracking centrality, etc). The second is related to large scale organization of the network, the core-periphery structure, composed by a dense core plus an outlying and loosely-connected periphery. In this paper we investigate the relation between these two concepts. We consider networks generated via the stochastic block model, or its degree corrected version, with a core-periphery structure and we investigate the centrality properties of the core nodes and the ability of several centrality metrics to identify them. We find that the three measures with the best performance are marginals obtained with belief propagation, PageRank, and degree centrality, while non-backtracking and eigenvector centrality (or MINRES [10], showed to be equivalent to the latter in the large network limit) perform worse in the investigated networks. (paper: interdisciplinary statistical mechanics )

Central Laboratories Services

Data.gov (United States)

Federal Laboratory Consortium — The TVA Central Laboratories Services is a comprehensive technical support center, offering you a complete range of scientific, engineering, and technical services....

RELATION BETWEEN ISLAMIC BANK AND CENTRAL BANK

OpenAIRE

PAKSOY, H. Mustafa; ABAROSS, Nour

2015-01-01

This study deals with the nature of Islamic banks and their features, and requirements of these features in terms of control tools and methods appropriate with the particularity of their business and their relation with the traditional central bank. At the same time aims to view the relationship between Islamic bank and central bank. To explain this relation the researcher started to explain what is the central bank, objectives of central bank, and characteristics, what is Islamic bank and ob...

Distributed trace using central performance counter memory

Science.gov (United States)

Satterfield, David L.; Sexton, James C.

2013-01-22

A plurality of processing cores, are central storage unit having at least memory connected in a daisy chain manner, forming a daisy chain ring layout on an integrated chip. At least one of the plurality of processing cores places trace data on the daisy chain connection for transmitting the trace data to the central storage unit, and the central storage unit detects the trace data and stores the trace data in the memory co-located in with the central storage unit.

Serpentinization and its implications for life on the early Earth and Mars.

Science.gov (United States)

Schulte, Mitch; Blake, David; Hoehler, Tori; McCollom, Thomas

2006-04-01

Ophiolites, sections of ocean crust tectonically displaced onto land, offer significant potential to support chemolithoautotrophic life through the provision of energy and reducing power during aqueous alteration of their highly reduced mineralogies. There is substantial chemical disequilibrium between the primary olivine and pyroxene mineralogy of these ophiolites and the fluids circulating through them. This disequilibrium represents a potential source of chemical energy that could sustain life. Moreover, E (h)-pH conditions resulting from rock- water interactions in ultrabasic rocks are conducive to important abiotic processes antecedent to the origin of life. Serpentinization--the reaction of olivine- and pyroxene-rich rocks with water--produces magnetite, hydroxide, and serpentine minerals, and liberates molecular hydrogen, a source of energy and electrons that can be readily utilized by a broad array of chemosynthetic organisms. These systems are viewed as important analogs for potential early ecosystems on both Earth and Mars, where highly reducing mineralogy was likely widespread in an undifferentiated crust. Secondary phases precipitated during serpentinization have the capability to preserve organic or mineral biosignatures. We describe the petrology and mineral chemistry of an ophiolite-hosted cold spring in northern California and propose criteria to aid in the identification of serpentinizing terranes on Mars that have the potential to harbor chemosynthetic life.

Accountability of Central Banks : Aspects and Quantification

NARCIS (Netherlands)

de Haan, J.; Amtenbrink, F.; Eijffinger, S.C.W.

1998-01-01

This paper starts with a discussion of the various aspects of accountability of central banks. On the basis of this discussion we construct an indicator for accountability for 16 central banks, including the European Central Bank. It is shown that the degree of accountability differs considerably

48 CFR 18.102 - Central contractor registration.

Science.gov (United States)

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Central contractor... Central contractor registration. Contractors are not required to be registered in the Central Contractor.... (See 4.1102). However, contractors are required to register with CCR in order to gain access to the...

Closed central slip injuries--a missed diagnosis?

LENUS (Irish Health Repository)

Nugent, N

2011-09-01

The extensor apparatus of the finger is a complex structure and injury can lead to significant digital dysfunction. Closed central slip injuries may be missed or diagnosis delayed because of lack of an open wound and often no radiographic abnormality, and can result in boutonniere deformities if untreated. This study aimed to quantify the number of patients attending with closed central slip injuries and to ascertain if the initial diagnosis was correct. The number of patients presenting to us over a 6 month period was recorded. The original diagnosis, time to diagnosis of central slip injury and the presence\\/absence of a boutonniere deformity were recorded. Ten patients were included in the study. Seven (70%) injuries were due to sport. Eight (80%) had a delayed diagnosis of central slip injury. Six (60%) had previously presented to general practitioners or emergency departments. Seven (70%) had boutonniere deformities. Closed central slip injuries can be missed. Simple clinical tests can diagnose central slip disruption.

Central Pain Syndrome

Science.gov (United States)

... such as neurontin (gabapentin) can be useful. Lowering stress levels appears to reduce pain. View Full Treatment Information Definition Central pain syndrome is a neurological condition caused ...

Centralized digital control of accelerators

International Nuclear Information System (INIS)

Melen, R.E.

1983-09-01

In contrasting the title of this paper with a second paper to be presented at this conference entitled Distributed Digital Control of Accelerators, a potential reader might be led to believe that this paper will focus on systems whose computing intelligence is centered in one or more computers in a centralized location. Instead, this paper will describe the architectural evolution of SLAC's computer based accelerator control systems with respect to the distribution of their intelligence. However, the use of the word centralized in the title is appropriate because these systems are based on the use of centralized large and computationally powerful processors that are typically supported by networks of smaller distributed processors

Fast network centrality analysis using GPUs

Directory of Open Access Journals (Sweden)

Shi Zhiao

2011-05-01

Full Text Available Abstract Background With the exploding volume of data generated by continuously evolving high-throughput technologies, biological network analysis problems are growing larger in scale and craving for more computational power. General Purpose computation on Graphics Processing Units (GPGPU provides a cost-effective technology for the study of large-scale biological networks. Designing algorithms that maximize data parallelism is the key in leveraging the power of GPUs. Results We proposed an efficient data parallel formulation of the All-Pairs Shortest Path problem, which is the key component for shortest path-based centrality computation. A betweenness centrality algorithm built upon this formulation was developed and benchmarked against the most recent GPU-based algorithm. Speedup between 11 to 19% was observed in various simulated scale-free networks. We further designed three algorithms based on this core component to compute closeness centrality, eccentricity centrality and stress centrality. To make all these algorithms available to the research community, we developed a software package gpu-fan (GPU-based Fast Analysis of Networks for CUDA enabled GPUs. Speedup of 10-50× compared with CPU implementations was observed for simulated scale-free networks and real world biological networks. Conclusions gpu-fan provides a significant performance improvement for centrality computation in large-scale networks. Source code is available under the GNU Public License (GPL at http://bioinfo.vanderbilt.edu/gpu-fan/.

Microsurgical anatomy of the central lobe.

Science.gov (United States)

Frigeri, Thomas; Paglioli, Eliseu; de Oliveira, Evandro; Rhoton, Albert L

2015-03-01

The central lobe consists of the pre- and postcentral gyri on the lateral surface and the paracentral lobule on the medial surface and corresponds to the sensorimotor cortex. The objective of the present study was to define the neural features, craniometric relationships, arterial supply, and venous drainage of the central lobe. Cadaveric hemispheres dissected using microsurgical techniques provided the material for this study. The coronal suture is closer to the precentral gyrus and central sulcus at its lower rather than at its upper end, but they are closest at a point near where the superior temporal line crosses the coronal suture. The arterial supply of the lower two-thirds of the lateral surface of the central lobe was from the central, precentral, and anterior parietal branches that arose predominantly from the superior trunk of the middle cerebral artery. The medial surface and the superior third of the lateral surface were supplied by the posterior interior frontal, paracentral, and superior parietal branches of the pericallosal and callosomarginal arteries. The venous drainage of the superior two-thirds of the lateral surface and the central lobe on the medial surface was predominantly through the superior sagittal sinus, and the inferior third of the lateral surface was predominantly through the superficial sylvian veins to the sphenoparietal sinus or the vein of Labbé to the transverse sinus. The pre- and postcentral gyri and paracentral lobule have a morphological and functional anatomy that differentiates them from the remainder of their respective lobes and are considered by many as a single lobe. An understanding of the anatomical relationships of the central lobe can be useful in preoperative planning and in establishing reliable intraoperative landmarks.

Several Centuries of Centrality

OpenAIRE

Dana L. Roth

2015-01-01

As Carolyn Bertozzi mentioned in her inaugural editorial, the relationship of “Central Science” to “Chemistry” became popularized over 40 years ago with the publication of the first edition of Brown and LeMay’s Chemistry: The Central Science, now in its 13th edition. Yet as late as 2003, Prof. Sason Shaik at The Hebrew University claimed “popularization of chemistry remains scant.” He goes on to share [his] “own experience of popularizing chemistry by delivering the following universal messag...

Central Chile

Science.gov (United States)

2002-01-01

The beginning of spring in central Chile looked like this to SeaWiFS. The snow-covered Andes mark the country's eastern border, and phytoplankton blooms and river sediment plumes fill the waters off its west coast. A large eddy due west of Concepcion is highlighted by the phytoplankton it contains.

Analyzing complex networks through correlations in centrality measurements

International Nuclear Information System (INIS)

Ricardo Furlan Ronqui, José; Travieso, Gonzalo

2015-01-01

Many real world systems can be expressed as complex networks of interconnected nodes. It is frequently important to be able to quantify the relative importance of the various nodes in the network, a task accomplished by defining some centrality measures, with different centrality definitions stressing different aspects of the network. It is interesting to know to what extent these different centrality definitions are related for different networks. In this work, we study the correlation between pairs of a set of centrality measures for different real world networks and two network models. We show that the centralities are in general correlated, but with stronger correlations for network models than for real networks. We also show that the strength of the correlation of each pair of centralities varies from network to network. Taking this fact into account, we propose the use of a centrality correlation profile, consisting of the values of the correlation coefficients between all pairs of centralities of interest, as a way to characterize networks. Using the yeast protein interaction network as an example we show also that the centrality correlation profile can be used to assess the adequacy of a network model as a representation of a given real network. (paper)

Central voice production and pathophysiology of spasmodic dysphonia.

Science.gov (United States)

Mor, Niv; Simonyan, Kristina; Blitzer, Andrew

2018-01-01

Our ability to speak is complex, and the role of the central nervous system in controlling speech production is often overlooked in the field of otolaryngology. In this brief review, we present an integrated overview of speech production with a focus on the role of central nervous system. The role of central control of voice production is then further discussed in relation to the potential pathophysiology of spasmodic dysphonia (SD). Peer-review articles on central laryngeal control and SD were identified from PUBMED search. Selected articles were augmented with designated relevant publications. Publications that discussed central and peripheral nervous system control of voice production and the central pathophysiology of laryngeal dystonia were chosen. Our ability to speak is regulated by specialized complex mechanisms coordinated by high-level cortical signaling, brainstem reflexes, peripheral nerves, muscles, and mucosal actions. Recent studies suggest that SD results from a primary central disturbance associated with dysfunction at our highest levels of central voice control. The efficacy of botulinum toxin in treating SD may not be limited solely to its local effect on laryngeal muscles and also may modulate the disorder at the level of the central nervous system. Future therapeutic options that target the central nervous system may help modulate the underlying disorder in SD and allow clinicians to better understand the principal pathophysiology. NA.Laryngoscope, 128:177-183, 2018. © 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Making Central Banks Serve The Real Economy

Directory of Open Access Journals (Sweden)

Suleika Reiners

2013-10-01

Full Text Available The challenge is to redirect central bank money into the real economy and to the needs of society. If new money is issued to expand the productive capacity, there is no reason for inflation. Long-term financing could become available at an affordable price. Central bank money must not replace a sound tax system and the distribution of income and wealth, but complement them. The remaining task, apart from the financing of real needs, is the prevention of speculative asset price inflation. For this, central banks and regulators should install debt brakes for the financial sector. Furthermore, independent monetary policy calls for capital account management. It enables national central banks to find space for the conduct of their own policies in an interdependent global economy. Coordination between central banks and governments might increase as policies combine monetary, fiscal and regulatory facets. The future role of central banks should particularly lie in their insights regarding capital flows and leverage cycles and in their ability to create and withdraw money, depend­ing on economic conditions.

Geometric origin of central charges

International Nuclear Information System (INIS)

Lukierski, J.; Rytel, L.

1981-05-01

The complete set of N(N-1) central charge generators for D=4 N-extended super Poincare algebra is obtained by suitable contraction of OSp (2N; 4) superalgebra. The superspace realizations of the spinorial generators with central charges are derived. The conjugate set of N(N-1) additional bosonic superspace coordinates is introduced in an unique and geometric way. (author)

Afrique Centrale

African Journals Online (AJOL)

PR BOKO

(Afrique Centrale) : peuplement de protozoaires ciliés et macro invertébrés ... Le lac d'Obili est un écosystème aquatique situé en plein cœur de Yaoundé en ...... électrique des eaux est assez stable, autour de 200 ; ce qui suppose que la ...

Reconnaissance Geologic Map of the Hayfork 15' Quadrangle, Trinity County, California

Science.gov (United States)

Irwin, William P.

2010-01-01

The Hayfork 15' quadrangle is located just west of the Weaverville 15' quadrangle in the southern part of the Klamath Mountains geologic province of northern California. It spans parts of six generally north-northwest-trending tectonostratigraphic terranes that are, from east to west, the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, Western Hayfork, and Rattlesnake Creek terranes. Remnants of a once-widespread postaccretionary overlap assemblage, the Cretaceous Great Valley sequence, crop out at three localities in the southern part of the Hayfork quadrangle. The Tertiary fluvial and lacustrine Weaverville Formation occupies a large, shallow, east-northeast-trending graben in the south half of the quadrangle. The small area of Eastern Klamath terrane is part of the Oregon Mountain outlier, which is more widely exposed to the east in the Weaverville 15' quadrangle. It was originally mapped as a thrust plate of Bragdon(?) Formation, but it is now thought by some to be part of an outlier of Yreka terrane that has been dislocated 60 km southward by the La Grange Fault. The Central Metamorphic terrane, which forms the footwall of the La Grange Fault, was formed by the eastward subduction of oceanic crustal basalt (the Salmon Hornblende Schist) and its overlying siliceous sediments with interbedded limestone (the Abrams Mica Schist) beneath the Eastern Klamath terrane. Rb-Sr analysis of the Abrams Mica Schist indicates a Middle Devonian metamorphic age of approximately 380 Ma, which probably represents the age of subduction. The North Fork terrane, which is faulted against the western boundary of the Central Metamorphic terrane, consists of the Permian(?) North Fork ophiolite and overlying broken formation and melange of Permian to Early Jurassic (Pliensbachian) marine metasedimentary and metavolcanic rocks. The ophiolite, which crops out along the western border of the terrane, is thrust westward over the Eastern Hayfork terrane. The Eastern

Atmospheres of central stars

International Nuclear Information System (INIS)

Hummer, D.G.

1978-01-01

The author presents a brief summary of atmospheric models that are of possible relevance to the central stars of planetary nebulae, and then discusses the extent to which these models accord with the observations of both nebulae and central stars. Particular attention is given to the significance of the very high Zanstra temperature implied by the nebulae He II lambda 4686 A line, and to the discrepancy between the Zanstra He II temperature and the considerably lower temperatures suggested by the appearance of the visual spectrum for some of these objects. (Auth.)

Representation of Central Asia and Traveling Self in Vambery’s Travels in Central Asia

Directory of Open Access Journals (Sweden)

Ahmad Gholi

2016-03-01

Full Text Available In the course of the nineteenth century Arminius Vambery, an anglophile travel writer, in the guise of a mendicant dervish with a group of Tartar pilgrims departs to secluded and sealed Central Asia. After six months travel in the Khanates of Central Asia, he undertakes a journey to England where he offers his observations to the Royal Geographical Society and publishes his travelogue, Travel in Central Asia. Despite its literary merits and connection with British imperialism, the travelogue has not been scrutinized separately by the scholars of travel writing. To fill the gap, this article by drawing on the theories of post-structuralism: Orientalism and Postcolonialism, endeavors to unveil the political agenda behind the travel writer’s representation of his travelees, destination, and his own traveling self. Additionally, it argues that the travel writer in dialogue with other Western travel writers to deterritorialize his traversed region or justify the prospective presence of Britain in Central Asia, represents his journey destination as the locus of barbarity, a region under the grip of despotic rulers, as well as an area with frozen time, while to exhibit his Eurocentrism, he portrays his traveling subject as the a suffering hero and a benign traveler.

What makes you more central? : antecedents of changes in betweenness-centrality in technology-based alliance networks

NARCIS (Netherlands)

Gilsing, V.A.; Cloodt, M.M.A.H.; Bertrand-Cloodt, D.A.M.

2016-01-01

Although central network positions have been associated with above average performance effects, an important void that still remains is how firms come to occupy a more central position in the first place. Whereas recently made exogenous explanations have shed some more light on aggregate changes in

Central venous obstruction in the thorax

International Nuclear Information System (INIS)

Collin, G.; Jones, R.G.; Willis, A.P.

2015-01-01

Central venous stenosis and occlusion can occur secondary to a spectrum of conditions ranging from aggressive malignancy to benign extrinsic anatomical compression in otherwise healthy individuals. Irrespective of aetiology, significant morbidity in the acute setting and long term can occur unless prompt accurate diagnosis and appropriate management is initiated, the radiologist being central to both. The present review will provide radiologists with a thorough illustration and explanation of the range of central venous conditions in the thorax (including deep vein thrombosis, thoracic outlet syndrome, haemodialysis, and malignancy related causes), the salient imaging findings and interventional management using case examples from the authors' practice. - Highlights: • We show a range of causes of central venous disease in the thorax. • We provide information about different imaging and management strategies. • We show several cases with successes and complications of endovascular management

Central station market development strategies for photovoltaics

Science.gov (United States)

1980-01-01

Federal market development strategies designed to accelerate the market penetration of central station applications of photovoltaic energy system are analyzed. Since no specific goals were set for the commercialization of central station applications, strategic principles are explored which, when coupled with specific objectives for central stations, can produce a market development implementation plan. The study includes (1) background information on the National Photovoltaic Program, photovoltaic technology, and central stations; (2) a brief market assessment; (3) a discussion of the viewpoints of the electric utility industry with respect to solar energy; (4) a discussion of commercialization issues; and (5) strategy principles. It is recommended that a set of specific goals and objectives be defined for the photovoltaic central station program, and that these goals and objectives evolve into an implementation plan that identifies the appropriate federal role.

California's Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California's Central Valley

Science.gov (United States)

Faunt, Claudia C.; Hanson, Randall T.; Belitz, Kenneth; Rogers, Laurel

2009-01-01

Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley's population has nearly doubled to 3.8 million people. It is expected to increase to 6 million by 2020. Statewide population growth, anticipated reductions in Colorado River water deliveries, drought, and the ecological crisis in the Sacramento-San Joaquin Delta have created an intense demand for water. Tools and information can be used to help manage the Central Valley aquifer system, an important State and national resource.

Interest Rate Policy Of Selected Central Banks In Central And Eastern Europe

Directory of Open Access Journals (Sweden)

GRABIA TOMASZ

2015-03-01

Full Text Available The aim of this article is to present and evaluate interest rate policies of three selected central banks in Central and Eastern Europe (Poland, the Czech Republic, and Hungary from 2001 to 2013. The study consists of an introduction (Section 1 and three main parts. The introduction contains a theoretical description of the role of interest rate policy, the dilemmas connected with it, as well as an analysis of the strategies and goals of monetary policies of the National Bank of Poland (NBP, the Czech National Bank (CzNB, and the National Bank of Hungary (NBH in the context of existing legal and institutional conditions. In turn, the first empirical part (Section 2 examines how the analysed central banks responded to changes in inflation, unemployment, and economic growth rates. The tools of the analysis are the nominal and real interest rates of those banks. The subsequent research part (Section 3 attempts to evaluate the degree of the contractionary nature of interest rate policies in specific countries in the context of the Taylor rule. The text ends with a summary (Section 4 encompassing concise conclusions drawn from the earlier analyses.

D Central Line Extraction of Fossil Oyster Shells

Science.gov (United States)

Djuricic, A.; Puttonen, E.; Harzhauser, M.; Mandic, O.; Székely, B.; Pfeifer, N.

2016-06-01

Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii) extraction of Voronoi vertices and construction of a connected graph tree from them; iii) reduction of the graph to the longest possible central line via Dijkstra's algorithm; iv) extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v) integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which is deemed

Central Bank Independence, Transparency and Accountability Indexes: a Survey

Directory of Open Access Journals (Sweden)

Dumiter Florin Cornel

2014-06-01

Full Text Available Recently, the remarkable trend upon central bank independence and the efficient monetary policy were seriously highlighted in the monetary economics field. Starting from 1990s’ central bank independence was at the core of policy making and central banking problems, because of the widespread economical, political, personal and budgetary autonomy of the central bank. Nowadays, we can observe an increasing trend upon central bank transparency, for evaluating more accurate the central bank’s performances by the wide public, mass-media and financial markets. Consequently, a central bank must encompass a high degree of accountability and responsibility, because of the final liability in case of failure. In this paper we present, analyze and assess the construction of the most important indices regarding central bank independence, transparency and accountability in a chronological manner, presenting also the advantages and disadvantages of these indices related to actual practices of central banks. Moreover, we analyze the analytical results of the empirical testing of these indices with a considerable impact upon the developed and developing country group. In regard with the empirical results of different authors, we suggest the importance and the necessity for constructing an aggregate index for measuring central bank independence, transparency and accountability, based on de jure stipulations and the actual practices of the central banks.

CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY

Energy Technology Data Exchange (ETDEWEB)

BERGMAN, T. B.; STEFANSKI, L. D.; SEELEY, P. N.; ZINSLI, L. C.; CUSACK, L. J.

2012-09-19

THE CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY WAS CONDUCTED TO DEVELOP AN OPTIMAL SEQUENCE OF REMEDIATION ACTIVITIES IMPLEMENTING THE CERCLA DECISION ON THE CENTRAL PLATEAU. THE STUDY DEFINES A SEQUENCE OF ACTIVITIES THAT RESULT IN AN EFFECTIVE USE OF RESOURCES FROM A STRATEGIC PERSPECTIVE WHEN CONSIDERING EQUIPMENT PROCUREMENT AND STAGING, WORKFORCE MOBILIZATION/DEMOBILIZATION, WORKFORCE LEVELING, WORKFORCE SKILL-MIX, AND OTHER REMEDIATION/DISPOSITION PROJECT EXECUTION PARAMETERS.

"Central Station" Londonis

Index Scriptorium Estoniae

2000-01-01

Londoni galeriis Milch seitsme läti, leedu ja eesti kunstniku projekt "Central Station". Kuraatorid Lisa Panting, Sally Tallant. Eestist osalevad Hanno Soans (Catarina Campinoga koostöös valminud video), Kiwa, Kai Kaljo

Central Pontine Myelinolysis

Science.gov (United States)

... Clinical Trials Organizations Publications Definition Central pontine myelinolysis (CPM) is a neurological disorder that most frequently occurs ... Experts estimate that 10 percent of those with CPM will also have areas of EPM. The initial ...

[Centralization in obstetrics: pros and cons].

Science.gov (United States)

Roemer, V M; Ramb, S

1996-01-01

Possible advantages and disadvantages of a general centralization of German obstetric facilities are analysed in the study. The need for centralization of risk cases, especially premature births (regionalization) is pointed out. Centralization appears appropriate, since every fifth maternity unit in Germany (19.78%) has 300 or fewer deliveries per year. This one fifth of perinatal clinics accounts for 6.3% of all deliveries (N = 49450). There are appreciable differences between the old and new federal states (Bundesländer): in the recently acceded federal states, 48.7% of all perinatal clinics have deliveries of 300 and less per year. This group of perinatal clinics accounts for 29% of all deliveries in the new federal states. We have carried out a survey of the mother's attitude to centralization: out of 416 patients in the Detmold women's hospital whose mean age was 29.0 +/- 4.2 years, 90.4% were not in favor of general centralization of obstetrics. 43% were also against a centralization of risk cases (regionalization). 75% of the women surveyed objected to centralized obstetrics because of the 'possible absence of the family', the 'possible absence of students and trainees' (44.9%), the 'unfamiliarity with staff and premises' (41.8%) and 'fear of anonymity' (44.5%). The majority of all women (84.1%) did not want to have a drive more than 20 km to an obstetrics center. Fear of 'delivery in a taxi'(78.6%), the 'fear that the husband will come too late to the delivery' (65.4%) and that the 'overall course of the delivery might not be adequate for reasons of time'. The presence of a pediatrics department in conjunction with the perinatal clinic was rated very positively (93%). It is concluded from the data and further juridical considerations that centralization of risk cases (regionalization) is indispensable in the near future and that somewhat more further into the future decentralization should be carried out by closing obstetrics departments with substantially

District Central Office Leadership as Teaching: How Central Office Administrators Support Principals' Development as Instructional Leaders

Science.gov (United States)

Honig, Meredith I.

2012-01-01

Purpose: Research on educational leadership underscores the importance of principals operating as instructional leaders and intensive job-embedded supports for such work; this research also identifies central office staff as key support providers. However, it teaches little about what central office staff do when they provide such support and how…

Modelling Central Bank Independence and Inflation: Deus Ex Machina?

Directory of Open Access Journals (Sweden)

Dumiter Florin

2015-11-01

Full Text Available Central bank independence represents the core element of assessing the complex relationship between government and central bank, having at background the fundamental issue of a free monetary policy decision-making process from the hands of the political circle. However, central bank independence is a multilevel concept within some social, economic and behavioral implications both for the central banks and for the society at whole. Central bank independence is needed in order to establish an autonomous central bank with a high degree of freedom in choosing its’ instruments, objectives, techniques and tactics. Moreover, a high degree of transparency for the public disclosure and monitoring of central bank operation and transaction is needed for the social barometer of the central bank. Consequently the central bank must have a high degree of accountability and responsibility vis - á - vis of the most democratic institution, i.e. Parliament. In this article it is presented a comprehensive study regarding the complex relationship between central bank independence and inflation by modeling these two monetary policy panacea, in order to make a fine tuning regarding the causal relationship established in a heterodox manner.

Geochemical and Mineralogical Profiles Across the Listvenite- Metamorphic Transition in the Basal Megathrust of the Oman Ophiolite: First Results from Drilling at Oman Drilling Project Hole BT1B

Science.gov (United States)

Godard, M.; Bennett, E.; Carter, E.; Kourim, F.; Lafay, R.; Noël, J.; Kelemen, P. B.; Michibayashi, K.; Harris, M.

2017-12-01

The transition from the base of the Oman ophiolite to the underlying metamorphic sole was drilled at Hole BT1B (Sumail Massif) during Phase 1 of Oman Drilling Project (Winter 2016-2017). 74 samples were collected from the 300m of recovered cores for whole rock geochemical and XRD analyses. 55 listvenites, ophicarbonates and serpentinites, and 19 schists and greenstones were analyzed for major and minor elements (XRF) and for CO2 and S concentrations (CHNS) aboard DV Chikyu (ChikyuOman, Summer 2017). Analyses for trace elements (ICP-MS) at the University of Montpellier are in progress. The composition of listvenites, ophicalcites and serpentinites recovered at Hole BT1B record extensive interactions between CO2-rich fluids and the serpentinized peridotites. These reactions involved addition of SiO2 and formation of carbonates at the expense of the serpentinized peridotite protolith. All samples recovered from the mantle section are enriched in fluid mobile and incompatible trace elements compared to the mean composition of the Oman mantle. These enrichments are up to 103 times the Oman mantle for Rb and Ba. They mimic the pattern of the samples from the metamorphic sole. This suggests that the composition of the listvenites in these elements is controlled by that of contaminating fluids that may have originated in the same lithologies as those drilled at the base of Hole BT1B. Listvenites, ophicalcites and serpentinites also show notable downhole chemical variations, with listvenites showing marked variations in Al2O3 and TiO2. Occurrence of lherzolites and cpx-harzburgites has been reported at the base of the Oman dominantly harzburgitic mantle section. The observed variations in the listvenites (Al2O3 and TiO2) could be related to the composition of their protolith, the deepest having more fertile compositions. Alternatively, the observed downhole changes in the composition of listvenites may relate to the progressive equilibration of the reacting ultramafic

CENTRAL ROTATIONS OF MILKY WAY GLOBULAR CLUSTERS

International Nuclear Information System (INIS)

Fabricius, Maximilian H.; Rukdee, Surangkhana; Saglia, Roberto P.; Bender, Ralf; Hopp, Ulrich; Thomas, Jens; Williams, Michael J.; Noyola, Eva; Opitsch, Michael

2014-01-01

Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements

The pre-Cenozoic evolution of the Apuseni Mountains (Romania) in the light of new (thermo)geochronological data

Science.gov (United States)

Reiser, Martin; Schuster, Ralf; Spikings, Richard; Tropper, Peter; Fügenschuh, Bernhard

2013-04-01

The Apuseni Mountains in Romania occupy a central position within the Alpine-Carpathian-Dinaride system between the Pannonian basin in the West and the Transylvanian basin in the East. Following the final Late-Jurassic obduction of the East Vardar ophiolites, a NW-vergent nappe stack formed, which involves from bottom to top: Tisza- and Dacia-derived units, overlain by the South Apuseni or Transylvanian ophiolite belt (i.e. East Vardar ophiolites according to Schmid et al., 2008). This study addresses the tectonometamorphic evolution of Tisza and Dacia during the Late Jurassic/Cretaceous by means of newly obtained Rb-Sr, Sm-Nd, Ar-Ar and fission track ages together with geothermometric estimates from the eastern part of the Apuseni Mountains. The Tisza unit experienced a polyphase metamorphic evolution (Variscan and Cretaceous) and shows mostly strong retrograde overprinting. Dacia, on the other hand, only underwent lower amphibolite-facies (545°C/7.3 Kbar) metamorphic overprint during the Cretaceous and later retrogression is very moderate. Only the Vidolm Unit, the uppermost nappe within the Dacia nappe stack directly underlying the South Apuseni Ophiolites, recorded a pre-Alpine peak metamorphic event of the uppermost amphibolite-facies (635°C/10.6 Kbar) and therefore yielded older ages. Thus, the Vidolm Unit has to be treated differently from the rest of Dacia, regarding its tectonometamorphic evolution. Garnets from the Iara valley (Tisza unit) yielded an Albian Sm/Nd age (103 Ma), which points towards Mid-Cretaceous peak metamorphism. Ar/Ar ages on muscovite (95-100 Ma) from adjacent samples confirm this observation and are in good agreement with age data from the literature (see Dallmeyer et al., 1999). For the Dacia unit on the other hand, Sm/Nd ages of garnet and Ar/Ar analyses of muscovite (110-117 Ma) yielded lower Cretaceous ages. Additional Rb/Sr analyses of biotite from the Tisza and Dacia units further support the distinct evolution of both units

On the centrality of some graphs

Directory of Open Access Journals (Sweden)

Vecdi Aytac

2017-10-01

Full Text Available A central issue in the analysis of complex networks is the assessment of their stability and vulnerability. A variety of measures have been proposed in the literature to quantify the stability of networks and a number of graph-theoretic parameters have been used to derive formulas for calculating network reliability. Different measures for graph vulnerability have been introduced so far to study different aspects of the graph behavior after removal of vertices or links such as connectivity, toughness, scattering number, binding number, residual closeness and integrity. In this paper, we consider betweenness centrality of a graph. Betweenness centrality of a vertex of a graph is portion of the shortest paths all pairs of vertices passing through a given vertex. In this paper, we obtain exact values for betweenness centrality for some wheel related graphs namely gear, helm, sunflower and friendship graphs.

Petrologic and Microstructural Constraints on Focused Melt Transport in Dunites and Rheology of the Shallow Mantle

National Research Council Canada - National Science Library

Braun, Michael

2004-01-01

.... Chapter 2 uses the size distribution and abundance of dunites measured in the Oman ophiolite to place limits on the potential mechanisms by which dunites form and subsequently estimate the flux...

Computing betweenness centrality in external memory

DEFF Research Database (Denmark)

Arge, Lars; Goodrich, Michael T.; Walderveen, Freek van

2013-01-01

Betweenness centrality is one of the most well-known measures of the importance of nodes in a social-network graph. In this paper we describe the first known external-memory and cache-oblivious algorithms for computing betweenness centrality. We present four different external-memory algorithms...

Central bank independence and financial instability

NARCIS (Netherlands)

Klomp, J.G.; de Haan, J.

2009-01-01

It has been argued that central bank independence (CBI) may not only be beneficial for reaching the objective of price stability, but also for maintaining financial stability. Greater independence from external pressure implies that central banks are less politically constrained in acting to prevent

Central nervous system

Science.gov (United States)

The central nervous system is composed of the brain and spinal cord. Your brain and spinal cord serve as the main "processing center" for your entire nervous system. They control all the workings of your body.

Finasteride for chronic central serous chorioretinopathy.

Science.gov (United States)

Forooghian, Farzin; Meleth, Annal D; Cukras, Catherine; Chew, Emily Y; Wong, Wai T; Meyerle, Catherine B

2011-04-01

To evaluate the safety and efficacy of finasteride, an inhibitor of dihydrotestosterone synthesis, in the treatment of chronic central serous chorioretinopathy. Five patients with chronic central serous chorioretinopathy were prospectively enrolled in this pilot study. Patients were administered finasteride (5 mg) daily for 3 months, after which study medication was withheld and patients were observed for 3 months. Main outcome measures included best-corrected visual acuity, central subfield macular thickness, and subretinal fluid volume as assessed by optical coherence tomography. Serum dihydrotestosterone, serum testosterone, and urinary cortisol were also measured. There was no change in mean best-corrected visual acuity. Mean center-subfield macular thickness and subretinal fluid volume reached a nadir at 3 months and rose to levels that were below baseline by 6 months. The changes in both optical coherence tomography parameters paralleled those in serum dihydrotestosterone level. In four patients, center-subfield macular thickness and/or subretinal fluid volume increased after discontinuation of finasteride. In the remaining patient, both optical coherence tomography parameters normalized with finasteride and remained stable when the study medication was discontinued. Finasteride may represent a novel medical treatment for chronic central serous chorioretinopathy. Larger controlled clinical trials are needed to further assess the efficacy of finasteride for the treatment of central serous chorioretinopathy.

(De)centralization of the global informational ecosystem

OpenAIRE

Möller, Johanna; Rimscha, M. Bjørn von

2017-01-01

Centralization and decentralization are key concepts in debates that focus on the (anti)democratic character of digital societies. Centralization is understood as the control over communication and data flows, and decentralization as giving it (back) to users. Communication and media research focuses on centralization put forward by dominant digital media platforms, such as Facebook and Google, and governments. Decentralization is investigated regarding its potential in civil society, i.e., h...

Centrality and Creativity:

DEFF Research Database (Denmark)

Andersen, Kristina Vaarst; Lorenzen, Mark

2009-01-01

To provide new insights into urban hierarchy, this article brings together one of economic geography’s oldest and most well-established notions with one of its newest and most disputed notions: Christäller’s centrality and Florida’s creative class. Using a novel original database, the article...... compares the distribution of the general population and the creative class across 444 city regions in 8 European countries. It finds that the two groups are both distributed according to the rank-size rule, but exhibit different distinct phases with different slopes. The article argues that the two...... distributions are different because market thresholds for creative services and jobs are lower than thresholds for less specialized services and jobs. The article hence concludes that centrality exerts a strong influence upon urban hierarchies of creativity and that the study of creative urban city hierarchies...

Central Asia's Raging Waters: The Prospects of Water Conflict in Central Asia

National Research Council Canada - National Science Library

Hartman, William B

2007-01-01

.... The thesis analyzes these three political eras of Central Asian history using indicators of water conflict, including water quality, water quantity, water management for multiple uses, political...

Health challenges in Kazakhstan and Central Asia.

Science.gov (United States)

Adambekov, Shalkar; Kaiyrlykyzy, Aiym; Igissinov, Nurbek; Linkov, Faina

2016-01-01

The Central Asian region, which encompasses Kazakhstan, Uzbekistan, Tajikistan, Turkmenistan and Kyrgyzstan, is an interesting geographic region with a rich history dating back to the Silk Road, Mongol conquests and expansion of the Russian Empire. However, from a public health viewpoint, the Central Asian region is under-investigated, and many public health challenges exist, as countries of Central Asia inherited the centralised medical systems practiced in the Soviet Union, and are currently undergoing rapid transitions. A large number of low and middle-income countries around the world, including countries of Central Asia, face a double burden of chronic and infectious disease. This essay focuses on the exploration of the most important public health challenges in the Central Asian region, including limited scientific productivity, the double burden of chronic and infectious disease, the need for healthcare reform and the reduction in care variation. Central Asia has a large number of medical schools, medical centres, and emerging research institutes that can be used to foster a change in medical and public health practice in the region. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Central Rotations of Milky Way Globular Clusters

Science.gov (United States)

Fabricius, Maximilian H.; Noyola, Eva; Rukdee, Surangkhana; Saglia, Roberto P.; Bender, Ralf; Hopp, Ulrich; Thomas, Jens; Opitsch, Michael; Williams, Michael J.

2014-06-01

Most Milky Way globular clusters (GCs) exhibit measurable flattening, even if on a very low level. Both cluster rotation and tidal fields are thought to cause this flattening. Nevertheless, rotation has only been confirmed in a handful of GCs, based mostly on individual radial velocities at large radii. We are conducting a survey of the central kinematics of Galactic GCs using the new Integral Field Unit instrument VIRUS-W. We detect rotation in all 11 GCs that we have observed so far, rendering it likely that a large majority of the Milky Way GCs rotate. We use published catalogs of GCs to derive central ellipticities and position angles. We show that in all cases where the central ellipticity permits an accurate measurement of the position angle, those angles are in excellent agreement with the kinematic position angles that we derive from the VIRUS-W velocity fields. We find an unexpected tight correlation between central rotation and outer ellipticity, indicating that rotation drives flattening for the objects in our sample. We also find a tight correlation between central rotation and published values for the central velocity dispersion, most likely due to rotation impacting the old dispersion measurements. This Letter includes data taken at The McDonald Observatory of The University of Texas at Austin.

Decentralization or centralization: striking a balance.

Science.gov (United States)

Dirschel, K M

1994-09-01

An Executive Vice President for Nursing can provide the necessary link to meet diverse clinical demands when encountering centralization--decentralization decisions. Centralized communication links hospital departments giving nurses a unified voice. Decentralization acknowledges the need for diversity and achieves the right balance of uniformity through a responsive communications network.

Testing the Predictions of the Central Capacity Sharing Model

Science.gov (United States)

Tombu, Michael; Jolicoeur, Pierre

2005-01-01

The divergent predictions of 2 models of dual-task performance are investigated. The central bottleneck and central capacity sharing models argue that a central stage of information processing is capacity limited, whereas stages before and after are capacity free. The models disagree about the nature of this central capacity limitation. The…

NCEP Central Operations

Science.gov (United States)

) NCO Organizational Chart NOAA's Weather and Climate Operational Supercomputing System is known as Climate Climate Prediction Climate Archives Weather Safety Storm Ready NOAA Central Library Photo Library NCO's MISSION * Execute the NCEP operational model suite - Create climate, weather, ocean, space and

Centrality measures for immunization of weighted networks

Directory of Open Access Journals (Sweden)

Mohammad Khansari

2016-03-01

Full Text Available Effective immunization of individual communities with minimal cost in vaccination has made great discussion surrounding the realm of complex networks. Meanwhile, proper realization of relationship among people in society and applying it to social networks brings about substantial improvements in immunization. Accordingly, weighted graph in which link weights represent the intensity and intimacy of relationships is an acceptable approach. In this work we employ weighted graphs and a wide variety of weighted centrality measures to distinguish important individuals in contagion of diseases. Furthermore, we propose new centrality measures for weighted networks. Our experimental results show that Radiality-Degree centrality is satisfying for weighted BA networks. Additionally, PageRank-Degree and Radiality-Degree centralities showmoreacceptable performance in targeted immunization of weighted networks.

BWR plant advanced central control panel PODIA

International Nuclear Information System (INIS)

Fujii, K.; Hayakawa, H.; Ikeda, Y.; Neda, T.; Suto, O.; Takamiya, S.

1983-01-01

BWR plant central control panels have become more and more enlarged and complicated recently due to the magnification of the scale of a plant and the requirement to reinforce safety. So, it is important to make communication between men and the complicated central control panel smooth. Toshiba has developed an advanced central control panel, named PODIA, which uses many computers and color CRTs, and PODIA is now in the stage of application to practical plants. In this article, the writers first touch upon control functions transition in the central control room, the PODIA position concerning the world-wide trend in this technology phase and the human engineering on the design. Then they present concrete design concepts for the control board and computer system which constitute PODIA

Central beta-adrenergic modulation of cognitive flexibility.

Science.gov (United States)

Beversdorf, David Q; White, Dawn M; Chever, Daquesha C; Hughes, John D; Bornstein, Robert A

2002-12-20

Situational stressors and anxiety impede performance on creativity tests requiring cognitive flexibility. Preliminary research revealed better performance on a task requiring cognitive flexibility, the anagram task, after propranolol (beta-adrenergic antagonist) than after ephedrine (beta-adrenergic agonist). However, propranolol and ephedrine have both peripheral and central beta-adrenergic effects. In order to determine whether noradrenergic modulation of cognitive flexibility is a centrally or peripherally mediated phenomenon, we compared the effects of propranolol (peripheral and central beta-blocker), nadolol (peripheral beta-blocker), and placebo on anagram task performance. Solution latency scores for each subject were compared across the drug conditions. Anagram solution latency scores after propranolol were significantly lower than after nadolol. This suggests a centrally mediated modulatory influence of the noradrenergic system on cognitive flexibility.

African Journals Online: Central African Republic

African Journals Online (AJOL)

African Journals Online: Central African Republic. Home > African Journals Online: Central African Republic. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free to read Titles This ...

Central Sensitization-Based Classification for Temporomandibular Disorders: A Pathogenetic Hypothesis

Directory of Open Access Journals (Sweden)

Annalisa Monaco

2017-01-01

Full Text Available Dysregulation of Autonomic Nervous System (ANS and central pain pathways in temporomandibular disorders (TMD is a growing evidence. Authors include some forms of TMD among central sensitization syndromes (CSS, a group of pathologies characterized by central morphofunctional alterations. Central Sensitization Inventory (CSI is useful for clinical diagnosis. Clinical examination and CSI cannot identify the central site(s affected in these diseases. Ultralow frequency transcutaneous electrical nerve stimulation (ULFTENS is extensively used in TMD and in dental clinical practice, because of its effects on descending pain modulation pathways. The Diagnostic Criteria for TMD (DC/TMD are the most accurate tool for diagnosis and classification of TMD. However, it includes CSI to investigate central aspects of TMD. Preliminary data on sensory ULFTENS show it is a reliable tool for the study of central and autonomic pathways in TMD. An alternative classification based on the presence of Central Sensitization and on individual response to sensory ULFTENS is proposed. TMD may be classified into 4 groups: (a TMD with Central Sensitization ULFTENS Responders; (b TMD with Central Sensitization ULFTENS Nonresponders; (c TMD without Central Sensitization ULFTENS Responders; (d TMD without Central Sensitization ULFTENS Nonresponders. This pathogenic classification of TMD may help to differentiate therapy and aetiology.

Central depression of nuclear charge density distribution

International Nuclear Information System (INIS)

Chu Yanyun; Ren Zhongzhou; Wang Zaijun; Dong Tiekuang

2010-01-01

The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of 46 Ar and 44 S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in 46 Ar and 44 S prefer to occupy the 1d 3/2 state rather than the 2s 1/2 state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of 46 Ar and 44 S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.

Central Bank Independence and Inflation IN EU-28

Directory of Open Access Journals (Sweden)

Beju Daniela-Georgeta

2017-12-01

Full Text Available Today, both policymakers and academicians consider that the central bank’s main goal is to guarantee price stability. The central bank can sustain the government’s economic policies, but only without prejudicing this objective. In order to focus on price stability several studies found that central bank should have a high level of independence. This is why during the recent decades the majority of developed countries, but also several emerging economies have employed institutional reforms that conferred their monetary authorities – the central bank – more independence.

Paleaostress/strain study and its implications for the geodynamic history of the Jabal Akhdar Dome (Oman)

Science.gov (United States)

Scharf, Andreas; Amrouch, Khalid; Mattern, Frank

2016-04-01

Field observations, including oolite-, styolite, fracture analyses combined with laboratory measurements using calcite twin analysis show a ductile-to-brittle multiple-phase deformation history of the Arabian carbonate platform, ranging from Late Cretaceous to Neogene times. The Arabian carbonate platform, belonging to a passive continental margin since the Late Permian, was the site of the obduction of Tethyan oceanic lithosphere (Semail Ophiolite) during the Late Cretaceous, caused by the northward drift of Africa (Hanna, 1995). After or during the obduction, large parts of the entire nape pile composed of the Arabian platform and the Hawasina/Semail nappes, where folded and exhumed. This led to the exhumation of the Jabal Akhdar Dome. Our oolite samples from the Jabal Akhdar Dome and from below the ophiolite thrust reveal the strain ellipsoid related to the obduction. This strain ellipsoid shows components of pure and simple shear. In the latter case the longest axes of the strain ellipsoid are parallelly oriented to the direction of obduction (NE to SW), which is in good agreement with the direction of obduction as depicted by Hacker et al. (1996) for the study area. The pure-shear component (flattening) is interpreted to be a result of the overburden of the up to 7 km thick oceanic lithosphere. The oolites that are located approximately 200 m below the ophiolite thrust contact provide evidence for ductile deformation during the Late Cretaceous. These results are compared with strain and stress tensors obtained from styolites, calcite twins and fracture analyses, derived from the uppermost part of the Arabian platform of the Jabal Akhdar Dome. Our results show a complex and detailed structural deformation of the post-obduction history of the Jabal Akhdar Dome, including its folding and exhumation. Hanna, S. (1995) Field guide to the Geology of Oman. Ruwi (Historical Association of Oman. 178 pp. Hacker, B.R., Mosenfelder, J.L. & Gnos, E. (1996) Rapid emplacement

Ethnic Harassment, Ethnic Identity Centrality, and Well-Being.

Science.gov (United States)

Wolfram, Hans-Joachim; Linton, Kenisha; McDuff, Nona

2018-02-12

In this study, we examined the direct effect of (positive vs. negative) evaluation of potentially harassing experiences due to ethnic background on impaired well-being as well as the moderating effect of ethnic identity centrality on the relationship between (lower vs. higher) frequency of potentially harassing experiences and impaired well-being. Using a gender-balanced sample with equal proportions of black and minority ethnic and white undergraduate students (N = 240), we found that, expectedly, ethnic identity centrality intensified the effects of higher frequency of potentially harassing experiences on lower self-esteem and lower positive affect. Unexpectedly, however, gender identity centrality buffered the effects of higher frequency as well as more negative evaluation of potentially harassing experiences on lower self-esteem, indicating that gender identity centrality may be a protective resource, even though it is not specific to ethnic harassment. Exploratory analyses revealed that for black and minority ethnic respondents with high ethnic identity centrality and for white respondents with low ethnic identity centrality, there were associations between more negative evaluation of potentially harassing experiences and lower self-esteem and lower positive affect. This finding might indicate that ethnic identity centrality was a risk factor in black and ethnic minority respondents, but a protective factor in white respondents.

31 CFR 535.433 - Central Bank of Iran.

Science.gov (United States)

2010-07-01

... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Central Bank of Iran. 535.433 Section 535.433 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF... § 535.433 Central Bank of Iran. The Central Bank of Iran (Bank Markazi Iran) is an agency...

endodontic treatment of unusually long discolored maxillary central ...

African Journals Online (AJOL)

a few cases of dual–rooted maxillary central incisor have been reported in literature1-5. Maxillary central incisors vary in root ... The following case report describes the endodontic management of a patient with an unusually long maxillary central incisor in our environment. CASE PROFILE. A 31 year-old male was referred ...

GFT centrality: A new node importance measure for complex networks

Science.gov (United States)

Singh, Rahul; Chakraborty, Abhishek; Manoj, B. S.

2017-12-01

Identifying central nodes is very crucial to design efficient communication networks or to recognize key individuals of a social network. In this paper, we introduce Graph Fourier Transform Centrality (GFT-C), a metric that incorporates local as well as global characteristics of a node, to quantify the importance of a node in a complex network. GFT-C of a reference node in a network is estimated from the GFT coefficients derived from the importance signal of the reference node. Our study reveals the superiority of GFT-C over traditional centralities such as degree centrality, betweenness centrality, closeness centrality, eigenvector centrality, and Google PageRank centrality, in the context of various arbitrary and real-world networks with different degree-degree correlations.

Speaker Profiles and Abstracts

Indian Academy of Sciences (India)

2017-11-03

Nov 3, 2017 ... Origin of Manipur Ophiolite Complex, Indo-Myanmar Range, .... remote sensing to coastal and marine environments and has developed products for coastal management and .... industry giants at the cost of old businesses.

Chromian spinel-rich black sands from eastern shoreline of ...

Indian Academy of Sciences (India)

Chromian spinel; detrital sand; ophiolites; Andaman Island; India. J. Earth Syst. .... (olivine: ol) inclusion; (e) peridotitic spinel with extensive fracturing; and (f) heavily altered rim of a peridotitic spinel. ..... The authors acknowledge the financial.

The central image of a gravitationally lensed quasar.

Science.gov (United States)

Winn, Joshua N; Rusin, David; Kochanek, Christopher S

2004-02-12

A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts that there should be an odd number of images produced by the lens, but hitherto almost all lensed objects have two or four images. The missing 'central' images, which should be faint and appear near the centre of the lensing galaxy, have long been sought as probes of galactic cores too distant to resolve with ordinary observations. There are five candidates for central images, but in one case the third image is not necessarily the central one, and in the others the putative central images might be foreground sources. Here we report a secure identification of a central image, based on radio observations of one of the candidates. Lens models using the central image reveal that the massive black hole at the centre of the lensing galaxy has a mass of 20,000M(o) pc(-2), which is in agreement with expections based on observations of galaxies that are much closer to the Earth.

Multifocal electroretinogram and central visual field testing in central areolar choroidal dystrophy.

Science.gov (United States)

Gundogan, Fatih Cakir; Dinç, Umut Asli; Erdem, Uzeyir; Ozge, Gokhan; Sobaci, Gungor

2010-01-01

To study multifocal electroretinogram (mfERG) and its relation to retinal sensitivity assessed by Humphrey visual field (HVF) analysis in central areolar choroidal dystrophy (CACD). Seven eyes of 4 patients with CACD and 15 normal control subjects were examined. mfERG and central 30/2 HVF were tested for each participant. Ring analysis in mfERG was evaluated. HVF results were evaluated in 5 concentric rings in order to compare the results to concentric ring analysis in mfERG. The differences between control subjects and patients were evaluated by Mann-Whitney U test and the correlations were assessed by Spearman test. Mean Snellen acuity was 0.49+/-0.10 in patients. HVF revealed central scotoma in 6 of 7 eyes (85.7%), whereas a paracentral scotoma extending to fixation point was detected in 1 eye. The retinal sensitivities in 5 concentric rings in HVF were significantly lower (p<0.001 for ring 1 to ring 4, and p=0.017 in ring 5) in CACD patients. Similarly, CACD patients had lower P1/N1 amplitudes (p<0.05) and delayed P1/N1 implicit times (p<0.05). In CACD, in the areas of scotoma detected by HVF, mfERG values were depressed. However, both mfERG and HVF abnormalities were found outside the areas of ophthalmoscopically normal retinal areas.

Central nervous system mesenchymal chondrosarcoma

Energy Technology Data Exchange (ETDEWEB)

Salvati, M.; Frati, A.; Piccirilli, M.; Agrillo, A.; Brogna, C.; Occhiogrosso, G.; Giangaspero, F. [INM Neuromed IRCCS, Pozzilli (Italy). Dept. of Neurosurgery; Caroli, E. [Policlinico S. Andrea, Rome (Italy). Dept. of Neurological Sciences, Neurosurgery

2005-06-15

Central nervous system mesenchymal chondrosarcomas are rare malignant tumors that constitute a separate entity from the classical chondrosarcoma and myxoid variant. Clinical behaviour of central nervous system chondrosarcomas is still unknown. We describe two rare examples of intracranial mesenchymal chondrosarcoma with a review of the literature, in an attempt to clarify the clinical characteristics, prognosis and treatment of choice of these unusual tumors. Among the 55 reported cases, 23 had postoperative radiotherapy. Although there is no statistical significance according to the Log-Rank test (p=0.7), the patients treated with radiation therapy seem to have a better chance of survival. Patients who had adjuvant chemotherapy (only 5) showed survival times similar to those patients who had none. Although clinical behaviour of central nervous system chondrosarcomas remains to be defined, data from our series as well as literature show that radical removal is the best therapeutic choice. In addition, patients treated with postoperative radiotherapy seem to show a trend toward increased survival.

Central nervous system mesenchymal chondrosarcoma

International Nuclear Information System (INIS)

Salvati, M.; Frati, A.; Piccirilli, M.; Agrillo, A.; Brogna, C.; Occhiogrosso, G.; Giangaspero, F.; Caroli, E.

2005-01-01

Central nervous system mesenchymal chondrosarcomas are rare malignant tumors that constitute a separate entity from the classical chondrosarcoma and myxoid variant. Clinical behaviour of central nervous system chondrosarcomas is still unknown. We describe two rare examples of intracranial mesenchymal chondrosarcoma with a review of the literature, in an attempt to clarify the clinical characteristics, prognosis and treatment of choice of these unusual tumors. Among the 55 reported cases, 23 had postoperative radiotherapy. Although there is no statistical significance according to the Log-Rank test (p=0.7), the patients treated with radiation therapy seem to have a better chance of survival. Patients who had adjuvant chemotherapy (only 5) showed survival times similar to those patients who had none. Although clinical behaviour of central nervous system chondrosarcomas remains to be defined, data from our series as well as literature show that radical removal is the best therapeutic choice. In addition, patients treated with postoperative radiotherapy seem to show a trend toward increased survival

Centralization and decentralization in energy systems and associated risks

International Nuclear Information System (INIS)

Rehm, W.; Schinner, F.; Kromp, W.

1998-01-01

Full text of publication follows: the concept of centralization/decentralization is - considering its widespread use - surprisingly ill-defined. Within the SERF-program (Socio Economic Research on Fusion) an attempt is made to clarify the complex issue of centralization/decentralization and to analyze its expected interaction with electricity production system in the case of nuclear fusion. Fusion research at the time is a multinational, highly centralized undertaking. As a result of this, and due to the expected large energy production units, it is generally expected that fusion will be embedded in a highly centralized, international energy supply system. The degree of centralization of an energy supply system, however, is believed to have for reaching consequences on the stability of the system, and beyond that, on decision making processes in energy policy, as well as democratic structures on the national or even international level. Internationalization might require control instruments that do not exist so far. Amongst other reservations, it is the possibly unwanted consequences of such a highly centralized, international energy supply system that limit acceptance of the fusion technology in the public. Therefore, centralization and decentralization trends of energy supply systems over the years are being looked at, to study their influence on the political and social systems (and vice-versa). In a first step, an attempt is made to classify centralization. Careful analyses and evaluation of available literature revealed a broad spectrum of different forms and degrees of centralization. Various parameters describing energy production and distribution are used. A differentiation of centralization on a technical and on an organizational level seems necessary, although they are not fully independent of each other. Beyond this, the choice of parameters must depend on the questions to be addressed. A new approach defining different levels and degrees of

Centralization and decentralization in energy systems and associated risks

Energy Technology Data Exchange (ETDEWEB)

Rehm, W.; Schinner, F.; Kromp, W. [Vienna Univ., Institute of Risk Research, IRR (Austria)

1998-07-01

Full text of publication follows: the concept of centralization/decentralization is - considering its widespread use - surprisingly ill-defined. Within the SERF-program (Socio Economic Research on Fusion) an attempt is made to clarify the complex issue of centralization/decentralization and to analyze its expected interaction with electricity production system in the case of nuclear fusion. Fusion research at the time is a multinational, highly centralized undertaking. As a result of this, and due to the expected large energy production units, it is generally expected that fusion will be embedded in a highly centralized, international energy supply system. The degree of centralization of an energy supply system, however, is believed to have for reaching consequences on the stability of the system, and beyond that, on decision making processes in energy policy, as well as democratic structures on the national or even international level. Internationalization might require control instruments that do not exist so far. Amongst other reservations, it is the possibly unwanted consequences of such a highly centralized, international energy supply system that limit acceptance of the fusion technology in the public. Therefore, centralization and decentralization trends of energy supply systems over the years are being looked at, to study their influence on the political and social systems (and vice-versa). In a first step, an attempt is made to classify centralization. Careful analyses and evaluation of available literature revealed a broad spectrum of different forms and degrees of centralization. Various parameters describing energy production and distribution are used. A differentiation of centralization on a technical and on an organizational level seems necessary, although they are not fully independent of each other. Beyond this, the choice of parameters must depend on the questions to be addressed. A new approach defining different levels and degrees of

Central American Climatology

Science.gov (United States)

1985-04-01

Central America, as where mean temperatures are relatively warm throughout the year de- so spite seasonal rainfall changes. 75 Elevation, solar angle...November 1982 Control Hidalgo Anos.1952-1963, Republica de Nicaragua, Ministerio de Formento Y O0.PP, Comision Nacional de Energia . Craig, Richard A., The

3D CENTRAL LINE EXTRACTION OF FOSSIL OYSTER SHELLS

Directory of Open Access Journals (Sweden)

A. Djuricic

2016-06-01

Full Text Available Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm and digital surface models (1 mm are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii extraction of Voronoi vertices and construction of a connected graph tree from them; iii reduction of the graph to the longest possible central line via Dijkstra’s algorithm; iv extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which

Central obscuration effects on optical synthetic aperture imaging

Science.gov (United States)

Wang, Xue-wen; Luo, Xiao; Zheng, Li-gong; Zhang, Xue-jun

2014-02-01

Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.

Research on centrality of urban transport network nodes

Science.gov (United States)

Wang, Kui; Fu, Xiufen

2017-05-01

Based on the actual data of urban transport in Guangzhou, 19,150 bus stations in Guangzhou (as of 2014) are selected as nodes. Based on the theory of complex network, the network model of Guangzhou urban transport is constructed. By analyzing the degree centrality index, betweenness centrality index and closeness centrality index of nodes in the network, the level of centrality of each node in the network is studied. From a different point of view to determine the hub node of Guangzhou urban transport network, corresponding to the city's key sites and major transfer sites. The reliability of the network is determined by the stability of some key nodes (transport hub station). The research of network node centralization can provide a theoretical basis for the rational allocation of urban transport network sites and public transport system planning.

Carboniferous continental arc in the Hegenshan accretionary belt: Constrains from plutonic complex in central Inner Mongolia

Science.gov (United States)

Wei, Ruihua; Gao, Yongfeng; Xu, Shengchuan; Santosh, M.; Xin, Houtian; Zhang, Zhenmin; Li, Weilong; Liu, Yafang

2018-05-01

The architecture and tectonic evolution of the Hegenshan accretionary belt in the Central Asian Orogenic Belt (CAOB) remains debated. Here we present an integrated study of zircon U-Pb isotopic ages, whole rock major-trace elements, and Sr-Nd-Pb isotopic data from the Hegenshan volcanic-plutonic belt in central Inner Mongolia. Field observations and zircon U-Pb ages allow us to divide the intrusive complex into an early phase at 329-306 Ma and a late phase at 304 to 299 Ma. The intrusive bodies belong to two magma series: calc-alkaline rocks with I-type affinity and A-type granites. The early intrusions are composed of granodiorite, monzogranite and porphyritic granite, and the late calc-alkaline intrusions include gabbro though diorite to granodiorite. The calc-alkaline intrusive rocks exhibit a well-defined compositional trend from gabbro to granite, reflecting continuous fractional crystallization. These rocks show obvious enrichment in LILEs and LREEs and relative depletion of HFSEs, typical of subduction-related magma. They also exhibit isotopic characteristics of mantle-derived magmas such as low initial 87Sr/86Sr (0.7029-0.7053), positive ɛNd(t) values (0.06-4.76) and low radiogenic Pb isotopic compositions ((206Pb/204Pb)I = 17.907-19.198, (207Pb/204Pb)I = 15.474-15.555, (208Pb/204Pb)I = 37.408-38.893). The marked consistency in geochemical and isotopic compositions between the intrusive rocks and the coeval Baoligaomiao volcanic rocks define a Carboniferous continental arc. Together with available regional data, we infer that this east-west trending continental arc was generated by northward subduction of the Hegenshan ocean during Carboniferous. The late alkali-feldspar granites and the high-Si rhyolites of the Baoligaomiao volcanic succession show similar geochemical compositions with high SiO2 and variable total alkali contents, and low TiO2, MgO and CaO. These rocks are characterized by unusually low Sr and Ba, and high abundances of Zr, Th, Nb, HREEs

The andean ophiolitic megastructures on the Buga-Buenaventura transverse (Western Cordillera—Valle Colombia)

Science.gov (United States)

Bourgois, Jacques; Calle, Bernardo; Tournon, Jean; Toussaint, Jean-François

1982-02-01

A structural study of the Buga-Buenaventura transverse in the central part of the Western Cordillera of Colombia, has shown the presence of three structural units which, from bottom to top and from west to east, are: the Rio Dagua unit, the Rio Calima unit, and the Loboguerrero window unit. All three units comprise strata between 120 and 80 m.y. old overlying a basement of green rocks showing the characteristics of submarine flows. The Bolivar ultrabasic and basic massif is geographically linked to the Rio Calima unit, in which green rocks predominate, and is separated from it by a tectonic contact. The upper part of the massif, on the other hand, shows high-temperature metamorphic rocks formed during its emplacement. The Rio Dagua unit shows two tectonic phases with isoclinal folding and development of schistosity. The first phase is contemporaneous with low-grade metamorphism equivalent to lower greenschist facies conditions. The Loboguerrero window unit shows a large recumbent fold oriented towards the southeast. Deformation in the Rio Calima unit is weaker and appears to correspond to a higher structural level than in the two other units. As the attitudes of the S1, schistosity in the Rio Dagua unit and of the shear zones located at the green rocks-sediments contact in this same unit are similar to that of the overthrust at the base of the Rio Calima unit, we are led to postulate that the overthrust belongs to the first phase of deformation, as also does the recumbent fold in the Loboguerrero window unit. We are thus led to propose a southeastward direction of emplacement for the nappes in the Western Cordillera of Colombia. In conclusion, the authors extend their observations and propose a new structural interpretation of the "Occidente Colombiano".

Russian Language in the Central Asia Region

Directory of Open Access Journals (Sweden)

Ksenia Petrovna Borishpolets

2014-01-01

Full Text Available He article is devoted to the role of the Russian language in Central Asia and its development perspectives in the context of the Eurasian integration processes. Russian language has a long historical tradition in Central Asia and hasn't lost its importance even at the background of two waves of "derussification" that took place after 1991. Notwithstanding the decrease of the status, it keeps substantial public significance. During last two decades only in Turkmenistan we are witnessing the decrease in spreading of the Russian language among title population of the Central Asia region. Its positions as an active communication channel is secured not only by the social tradition, but also by the competitiveness of the Russian language education, advantages of the bilingual business, requirements of the labor migrants, HR interests and by some other pragmatic thoughts, which role within the context of Eurasian economic integration will increase. Despite the difficulties, it is too early to speak about the decrease of the Russian language in the Central Asia region. It is more likely that the institutes itself that maintain it and promoting it are at the low ebb. New scales and forms of practical work that is interested not only for Russia, but also Central Asia countries are required. Pressure on the resources of the Russian language increases the possibility of ethnic conflicts and strengthens the positions of political radicalism in Central Asia region.

Central alarm system replacement in NPP Krsko

International Nuclear Information System (INIS)

Cicvaric, D.; Susnic, M.; Djetelic, N.

2004-01-01

Current NPP Krsko central alarm system consists of three main segments. Main Control Board alarm system (BETA 1000), Ventilation Control Board alarm system (BETA 1000) and Electrical Control Board alarm system (BETA 1100). All sections are equipped with specific BetaTone audible alarms and silence, acknowledge as well as test push buttons. The main reason for central alarm system replacement is system obsolescence and problems with maintenance, due to lack of spare parts. Other issue is lack of system redundancy, which could lead to loss of several Alarm Light Boxes in the event of particular power supply failure. Current central alarm system does not provide means of alarm optimization, grouping or prioritization. There are three main options for central alarm system replacement: Conventional annunciator system, hybrid annunciator system and advanced alarm system. Advanced alarm system implementation requires Main Control Board upgrade, integration of process instrumentation and plant process computer as well as long time for replacement. NPP Krsko has decided to implement hybrid alarm system with patchwork approach. The new central alarm system will be stand alone, digital, with advanced filtering and alarm grouping options. Sequence of event recorder will be linked with plant process computer and time synchronized with redundant GPS signal. Advanced functions such as link to plant procedures will be implemented with plant process computer upgrade in outage 2006. Central alarm system replacement is due in outage 2004.(author)

Central Hemodynamics and Microcirculation in Critical Conditions

Directory of Open Access Journals (Sweden)

A. A. Kosovskikh

2013-01-01

Full Text Available Objective: to compare central hemodynamic and microcirculatory changes in critical conditions caused by different factors and to reveal their possible differences for a further differentiated approach to intensive therapy. Subjects and methods. The study covered 16 subjects with severe concomitant injury (mean age 41.96±2.83 years and 19 patients with general purulent peritonitis (mean age 45.34±2.16 years. Their follow-up was 7 days. The central hemodynamics was estimated by transpulmonary thermodilution using a Pulsion PiCCO Plus system (Pulsion Medical Systems, Germany. The microcirculatory bed was evaluated by cutaneous laser Doppler flowmetry using a LAKK-02 capillary blood flow laser analyzer (LAZMA Research-and-Production Association, Russian Federation. Results. The pattern of central hemodynamic and microcirculatory disorders varies with the trigger that has led to a critical condition. Central hemodynamics should be stabilized to ensure the average level of tissue perfusion in victims with severe concomitant injury. In general purulent peritonitis, microcirculatory disorders may persist even if the macrohemodynamic parameters are normal. Conclusion. The macrohemodynamic and microcirculatory differences obtained during the study suggest that a complex of intensive therapy should be differentiated and, if the latter is used, it is necessary not only to be based on the central hemodynamics, but also to take into consideration functional changes in microcirculation. Key words: severe concomitant injury, general purulent peritonitis, micro-circulation, central hemodynamics, type of circulation.

Central Neuropathic Pain in Spinal Cord Injury

Science.gov (United States)

Lee, Sujin; Zhao, Xing; Hatch, Maya; Chun, Sophia; Chang, Eric

2015-01-01

Spinal cord injury (SCI) is a devastating medical condition affecting 1.2 million people in the United States. Central neuropathic pain is one of the most common medical complications of SCI. Current treatment options include opioids, antiepileptic agents such as gabapentin, antispastic agents such as baclofen or tizanidine, and tricyclic acid. Other options include complementary, nonpharmacological treatment such as exercise or acupuncture, interventional treatments, and psychological approaches. Although these treatment options exist, central neuropathic pain in patients with SCI is still extremely difficult to treat because of its complexity. To develop and provide more effective treatment options to these patients, proper assessment of and classification tools for central neuropathic pain, as well as a better understanding of the pathophysiology, are needed. A combination of approaches, from standard general pain assessments to medically specific questions unique to SCI pathophysiology, is essential for this population. A multidisciplinary approach to patient care, in addition with a better understanding of pathophysiology and diagnosis, will lead to improved management and treatment of patients with SCI displaying central neuropathic pain. Here we summarize the most recent classification tools, pathophysiology, and current treatment options for patients with SCI with central neuropathic pain. PMID:25750485

Groundwater availability of the Central Valley Aquifer, California

Science.gov (United States)

Faunt, Claudia C.

2009-01-01

California's Central Valley covers about 20,000 square miles and is one of the most productive agricultural regions in the world. More than 250 different crops are grown in the Central Valley with an estimated value of $17 billion per year. This irrigated agriculture relies heavily on surface-water diversions and groundwater pumpage. Approximately one-sixth of the Nation's irrigated land is in the Central Valley, and about one-fifth of the Nation's groundwater demand is supplied from its aquifers. The Central Valley also is rapidly becoming an important area for California's expanding urban population. Since 1980, the population of the Central Valley has nearly doubled from 2 million to 3.8 million people. The Census Bureau projects that the Central Valley's population will increase to 6 million people by 2020. This surge in population has increased the competition for water resources within the Central Valley and statewide, which likely will be exacerbated by anticipated reductions in deliveries of Colorado River water to southern California. In response to this competition for water, a number of water-related issues have gained prominence: conservation of agricultural land, conjunctive use, artificial recharge, hydrologic implications of land-use change, and effects of climate variability. To provide information to stakeholders addressing these issues, the USGS Groundwater Resources Program made a detailed assessment of groundwater availability of the Central Valley aquifer system, that includes: (1) the present status of groundwater resources; (2) how these resources have changed over time; and (3) tools to assess system responses to stresses from future human uses and climate variability and change. This effort builds on previous investigations, such as the USGS Central Valley Regional Aquifer System and Analysis (CV-RASA) project and several other groundwater studies in the Valley completed by Federal, State and local agencies at differing scales. The

Centralized rehabilitation after servere traumatic brain injury

DEFF Research Database (Denmark)

Engberg, Aase Worså; Liebach, Annette; Nordenbo, Annette Mosbæk

2006-01-01

OBJECTIVES: To present results from the first 3 years of centralized subacute rehabilitation after very severe traumatic brain injury (TBI), and to compare results of centralized versus decentralized rehabilitation. MATERIAL AND METHODS: Prospectively, the most severely injured group of adults from...... post-trauma was 0.29, and at 1 year 0.055 per 100,000 population. By comparison of 39 patients from the centralized unit injured in 2000-2003 with 21 patients injured in 1982, 1987 or 1992 and with similar PTA- and age distributions and male/female ratio, Glasgow Outcome Scale score at discharge...

Linfoma no-Hodgkin del sistema nervioso central

OpenAIRE

Iglesias Rozas, José Rafael, 1942-

2000-01-01

Diecisiete imágenes de un linfoma no-Hodgkin del sistema nervioso central en una paciente de 66 años. Seventeen pictures of a non-Hodgkin lymphoma of the central nervous system in a 66-year-old female patient.

Centralized rehabilitation after servere traumatic brain injury

DEFF Research Database (Denmark)

Engberg, Aase Worså; Liebach, Annette; Nordenbo, Annette Mosbæk

2006-01-01

OBJECTIVES: To present results from the first 3 years of centralized subacute rehabilitation after very severe traumatic brain injury (TBI), and to compare results of centralized versus decentralized rehabilitation. MATERIAL AND METHODS: Prospectively, the most severely injured group of adults fr...

The Cartan Matrix of a Centralizer Algebra

Indian Academy of Sciences (India)

2010-12-20

Dec 20, 2010 ... The centralizer algebra of a matrix consists of those matrices that commute with it. We investigate the basic representation-theoretic invariants of centralizer algebras, namely their radicals, projective indecomposable modules, injective indecomposable modules, simple modules and Cartan matrices.

Parallel Algorithm for Incremental Betweenness Centrality on Large Graphs

KAUST Repository

Jamour, Fuad Tarek

2017-10-17

Betweenness centrality quantifies the importance of nodes in a graph in many applications, including network analysis, community detection and identification of influential users. Typically, graphs in such applications evolve over time. Thus, the computation of betweenness centrality should be performed incrementally. This is challenging because updating even a single edge may trigger the computation of all-pairs shortest paths in the entire graph. Existing approaches cannot scale to large graphs: they either require excessive memory (i.e., quadratic to the size of the input graph) or perform unnecessary computations rendering them prohibitively slow. We propose iCentral; a novel incremental algorithm for computing betweenness centrality in evolving graphs. We decompose the graph into biconnected components and prove that processing can be localized within the affected components. iCentral is the first algorithm to support incremental betweeness centrality computation within a graph component. This is done efficiently, in linear space; consequently, iCentral scales to large graphs. We demonstrate with real datasets that the serial implementation of iCentral is up to 3.7 times faster than existing serial methods. Our parallel implementation that scales to large graphs, is an order of magnitude faster than the state-of-the-art parallel algorithm, while using an order of magnitude less computational resources.

Social network analysis using k-Path centrality method

Science.gov (United States)

Taniarza, Natya; Adiwijaya; Maharani, Warih

2018-03-01

k-Path centrality is deemed as one of the effective methods to be applied in centrality measurement in which the influential node is estimated as the node that is being passed by information path frequently. Regarding this, k-Path centrality has been employed in the analysis of this paper specifically by adapting random-algorithm approach in order to: (1) determine the influential user’s ranking in a social media Twitter; and (2) ascertain the influence of parameter α in the numeration of k-Path centrality. According to the analysis, the findings showed that the method of k-Path centrality with random-algorithm approach can be used to determine user’s ranking which influences in the dissemination of information in Twitter. Furthermore, the findings also showed that parameter α influenced the duration and the ranking results: the less the α value, the longer the duration, yet the ranking results were more stable.

Encouraging Diversity- and Representation-Awareness in Geographically Centralized Content

OpenAIRE

Graells-Garrido, Eduardo; Lalmas, Mounia; Baeza-Yates, Ricardo

2015-01-01

In centralized countries, not only population, media and economic power are concentrated, but people give more attention to central locations. While this is not inherently bad, this behavior extends to micro-blogging platforms: central locations get more attention in terms of information flow. In this paper we study the effects of an information filtering algorithm that decentralizes content in such platforms. Particularly, we find that users from non-central locations were not able to identi...

Investigating for failure of central ventilation fan blade

International Nuclear Information System (INIS)

Koo, Jae Raeyang; Ko Woo Sig; Kim, Yeon Hwan; Park, Kwang Ha

2002-01-01

During the operation, central ventilation fan stopped when switch 'on' condition. When central ventilation fan disassemble, ten blades of fan fractured. We have searched cause of failure. We had modeling one of the fan blades and analysis with computer programs. Thus we have find that fracture of central ventilation fan blades is alternative stress and vibration at hub. In this paper, we have described cause of failure

Non-linear realizations of supersymmetry with off-shell central charges

International Nuclear Information System (INIS)

Santos Filho, P.B.; Oliveira Rivelles, V. de.

1985-01-01

A new class of non-linear realizations of the extended supersymmetry algebra with central charges is presented. They were obtained by applying the technique of dimensional reduction by Legendre transformation to a non-linear realization without central charges in one higher dimension. As a result an off-shell central charge is obtained. The non-linear lagrangian is the same as is the case of vanishing central charge. On-shell the central charge vanishes so this non-linear realization differs from that without central charges only off-shell. It is worked in two dimensions and its extension to higher dimensions is discussed. (Author) [pt

Central Odontogenic Fibroma of Simple Type

Directory of Open Access Journals (Sweden)

Prasanth Thankappan

2014-01-01

Full Text Available Central odontogenic fibroma (COF is an extremely rare benign tumor that accounts for 0.1% of all odontogenic tumors. It is a lesion associated with the crown of an unerupted tooth resembling dentigerous cyst. In this report, a 10-year-old male patient is presented, who was diagnosed with central odontogenic fibroma of simple type from clinical, radiological, and histopathological findings.

The Trade Off Between Central Bank Independence and Conservativeness

NARCIS (Netherlands)

Eijffinger, S.C.W.; Hoeberichts, M.M.

1996-01-01

This paper introduces a parameter for central bank independence in a monetary policy game with a conservative central banker.It tries to explain the optimal degree of central bank independence and conservativeness by four economic and political determinants, both theoretically and empirically.There

7 CFR 1032.2 - Central marketing area.

Science.gov (United States)

2010-01-01

... 7 Agriculture 9 2010-01-01 2009-01-01 true Central marketing area. 1032.2 Section 1032.2 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Milk), DEPARTMENT OF AGRICULTURE MILK IN THE CENTRAL MARKETING AREA Order Regulating...

Central nervous system depressant activityof Leonurus sibiricus ...

African Journals Online (AJOL)

The methanol extract of aerial parts of Leonurus sibiricus was shown to possess central nervous system depressant action by significantly decreased the time of onset of sleep and potentiated the pentobarbital induced sleeping time in mice. Keywords: Leonurus sibiricus, labiatae, central nervous depressant, sedation

Concept of the central clip

DEFF Research Database (Denmark)

Alegria-Barrero, Eduardo; Chan, Pak Hei; Foin, Nicolas

2014-01-01

AIMS: Percutaneous edge-to-edge mitral valve repair with the MitraClip(®) was shown to be a safe and feasible alternative compared to conventional surgical mitral valve repair. We analyse the concept of the central clip and the predictors for the need of more than one MitraClip(®) in our high.......8±10.7 years (30 males, 13 females; mean logistic EuroSCORE 24.1±11, mean LVEF 47.5±18.5%; mean±SD) were treated. Median follow-up was 385 days (104-630; Q1-Q3). Device implantation success was 93%. All patients were treated following the central clip concept: 52.5% of MR was degenerative in aetiology and 47....... The presence of a restricted posterior mitral valve leaflet (PML) was inversely correlated with the need for more than one clip (p=0.02). A cut-off value of ≥7.5 mm for vena contracta predicted the need for a second clip (sensitivity 83%, specificity 90%, p=0.01). CONCLUSIONS: The central MitraClip(®) concept...

Central Venous Occlusion in the Hemodialysis Patient.

Science.gov (United States)

Krishna, Vinay Narasimha; Eason, Joseph B; Allon, Michael

2016-11-01

Central venous stenosis (CVS) is encountered frequently among hemodialysis patients. Prior ipsilateral central venous catheterization and cardiac rhythm device insertions are common risk factors, but CVS can also occur in the absence of this history. Chronic CVS can cause thrombosis with partial or complete occlusion of the central vein at the site of stenosis. CVS is frequently asymptomatic and identified as an incidental finding during imaging studies. Symptomatic CVS presents most commonly as an upper- or lower-extremity edema ipsilateral to the CVS. Previously unsuspected CVS may become symptomatic after placement of an ipsilateral vascular access. The likelihood of symptomatic CVS may be affected by the central venous catheter (CVC) location; CVC side; duration of CVC dependence; type, location, and blood flow of the ipsilateral access; and extent of collateral veins. Venous angiography is the gold standard for diagnosis. Percutaneous transluminal angioplasty and stent placement can improve the stenosis and alleviate symptoms, but CVS typically recurs frequently, requiring repeated interventions. Refractory symptomatic CVS may require ligation of the ipsilateral vascular access. Because no available treatment option is curative, the goal should be to prevent CVS by minimizing catheters and central vein instrumentation in patients with chronic kidney disease and dialysis patients. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Estrogen- and progesterone-receptor status in ECOG 2197: comparison of immunohistochemistry by local and central laboratories and quantitative reverse transcription polymerase chain reaction by central laboratory.

Science.gov (United States)

Badve, Sunil S; Baehner, Frederick L; Gray, Robert P; Childs, Barrett H; Maddala, Tara; Liu, Mei-Lan; Rowley, Steve C; Shak, Steven; Perez, Edith A; Perez, Edith D; Shulman, Lawrence J; Martino, Silvana; Davidson, Nancy E; Sledge, George W; Goldstein, Lori J; Sparano, Joseph A

2008-05-20

Central and local laboratory concordance for hormone receptor measurement is therapeutically important. This study compares estrogen receptor (ER) and progesterone receptor (PR) measured by local laboratory immunohistochemistry (IHC), central IHC, and central reverse-transcriptase polymerase chain reaction (RT-PCR) using a proprietary 21-gene assay. A case-control sample of 776 breast cancer patients from Eastern Cooperative Oncology Group (ECOG) study E2197 was evaluated. Central IHC Allred score for ER and PR was obtained using tissue microarrays and 1D5 ER antibody and 636 PR antibody. Quantitative RT-PCR for ER and PR in whole sections was performed using the 21-gene assay. For ER, the concordance between local and central IHC was 90% (95% CI, 88% to 92%), between local IHC and central RT-PCR was 91% (95% CI, 89% to 93%), and between central IHC and central RT-PCR was 93% (95% CI, 91% to 95%). For PR, the concordance between local IHC and central IHC was 84% (95% CI, 82% to 87%), between local IHC and central RT-PCR was 88% (95% CI, 85% to 90%), and between central IHC and central RT-PCR was 90% (95% CI, 88% to 92%). Although concordance was high, IHC ER-negative cases that were RT-PCR positive were more common than IHC ER-positive cases that were RT-PCR negative. In ER-positive patients, ER expression by central IHC Allred score was marginally associated with recurrence (P = .091), and ER expression by central RT-PCR was significantly associated with recurrence (P = .014). However, recurrence score, which incorporates additional genes/pathways, was a highly significant predictor of recurrence (P < .0001). There is a high degree of concordance among local IHC, central IHC, and central RT-PCR by the proprietary gene assay for ER and PR status. Although ER expression is marginally associated with relapse in ER-positive patients treated with chemohormonal therapy, recurrence score is a highly significant predictor of recurrence.

Heterogeneity across emerging market central bank reaction functions

Directory of Open Access Journals (Sweden)

Mesut Turkay

2017-09-01

Full Text Available The purpose of this study is to analyze monetary policy reaction functions of inflation targeting emerging market economies. Heterogeneity across central bank behavior is modelled using dynamic common correlated effects estimator in a panel data framework of 15 countries. The empirical method allows us to obtain country specific coefficients and shows differences across central bank reaction functions. Model results imply that central banks behave according to an extended Taylor rule and respond to deviation of inflation from the target, output gap, real exchange rate and external financial conditions. The study finds that emerging market central banks consider not only price stability, but also financial stability in setting of interest rates.

International Regulation of Central Arctic Ocean Fisheries

NARCIS (Netherlands)

Molenaar, E.J.

Due in particular to the impacts of climate change, the adequacy of the international regulation of Central Arctic Ocean fisheries has come under increasing scrutiny in recent years. As shown in this article, however, international regulation of Central Arctic Ocean fisheries is by no means entirely

Genetics Home Reference: congenital central hypoventilation syndrome

Science.gov (United States)

... Kravis EM, Zhou L, Rand CM, Weese-Mayer DE. Congenital central hypoventilation syndrome: PHOX2B mutations and phenotype. Am J Respir Crit ... BA, Leurgans SE, Berry-Kravis EM, Weese-Mayer DE. Congenital central hypoventilation syndrome: PHOX2B genotype determines risk for sudden death. Pediatr ...

Central Hardwoods ecosystem vulnerability assessment and synthesis: a report from the Central Hardwoods Climate Change Response Framework project

Science.gov (United States)

Leslie Brandt; Hong He; Louis Iverson; Frank R. Thompson; Patricia Butler; Stephen Handler; Maria Janowiak; P. Danielle Shannon; Chris Swanston; Matthew Albrecht; Richard Blume-Weaver; Paul Deizman; John DePuy; William D. Dijak; Gary Dinkel; Songlin Fei; D. Todd Jones-Farrand; Michael Leahy; Stephen Matthews; Paul Nelson; Brad Oberle; Judi Perez; Matthew Peters; Anantha Prasad; Jeffrey E. Schneiderman; John Shuey; Adam B. Smith; Charles Studyvin; John M. Tirpak; Jeffery W. Walk; Wen J. Wang; Laura Watts; Dale Weigel; Steve. Westin

2014-01-01

The forests in the Central Hardwoods Region will be affected directly and indirectly by a changing climate over the next 100 years. This assessment evaluates the vulnerability of terrestrial ecosystems in the Central Hardwoods Region of Illinois, Indiana, and Missouri to a range of future climates. Information on current forest conditions, observed climate trends,...

Proteomic landscape in Central and Eastern Europe: the 9th Central and Eastern European Proteomic Conference, Poznan, Poland

Czech Academy of Sciences Publication Activity Database

Gadher, S. J.; Marczak, L.; Luczak, M.; Stobiecki, M.; Widlak, P.; Kovářová, Hana

2016-01-01

Roč. 13, č. 1 (2016), s. 5-7 ISSN 1478-9450. [Central and Eastern European Proteomic Conference (CEEPC) /9./. Poznaň, 15.06.2015-18.06.2015] Institutional support: RVO:67985904 Keywords : Central and Eastern Proteomic Conference * proteomics * mass spectrometry imaging Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.849, year: 2016

Can the European Central Bank Create a European identity?

DEFF Research Database (Denmark)

Ravn Sørensen, Anders

2014-01-01

In what ways do central banks construct community, and how may the European Central Bank (ECB) contribute to a supranational European identity? In this paper I seek to answer these two questions by developing a conceptual framework for the ways that central banks construct national identities and...

Contested Communication; A Critical Analysis of Central Bank Speech

NARCIS (Netherlands)

L.H.J. Noordegraaf-Eelens (Liesbeth)

2010-01-01

textabstractThe more important words become, the more difficult it is to say things. This is the central message of this study on the communication by central bank presidents. Since the end of the twentieth century, central bank presidents see communication as an important means to influence

Central Asian Republic Info

Data.gov (United States)

US Agency for International Development — CAR Info is designed and managed by the Central Asian Republic Mission to fill in the knowledge and reporting gaps in existing agency systems for that Mission. It...

Divergent Roles of Central Serotonin in Adult Hippocampal Neurogenesis

Directory of Open Access Journals (Sweden)

Ning-Ning Song

2017-06-01

Full Text Available The central serotonin (5-HT system is the main target of selective serotonin reuptake inhibitors (SSRIs, the first-line antidepressants widely used in current general practice. One of the prominent features of chronic SSRI treatment in rodents is the enhanced adult neurogenesis in the hippocampus, which has been proposed to contribute to antidepressant effects. Therefore, tremendous effort has been made to decipher how central 5-HT regulates adult hippocampal neurogenesis. In this paper, we review how changes in the central serotonergic system alter adult hippocampal neurogenesis. We focus on data obtained from three categories of genetically engineered mouse models: (1 mice with altered central 5-HT levels from embryonic stages, (2 mice with deletion of 5-HT receptors from embryonic stages, and (3 mice with altered central 5-HT system exclusively in adulthood. These recent findings provide unique insights to interpret the multifaceted roles of central 5-HT on adult hippocampal neurogenesis and its associated effects on depression.

Transmission Reinforcements in the Central American Regional Power System

Energy Technology Data Exchange (ETDEWEB)

Elizondo, Marcelo A.; Vallem, Mallikarjuna R.; Samaan, Nader A.; Makarov, Yuri V.; Vyakaranam, Bharat; Nguyen, Tony B.; Munoz, Christian; Herrera, Ricardo; Midence, Diego; Shpitsberg, Anna

2016-07-25

The Central American regional interconnected power system (SER) connects the countries members of the Central American regional electricity market (MER): Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama. The SER was a result of a long term regional effort, and was initially conceived to transfer 300 MW between countries. However, the current transfer limits between countries range from 70 MW to 300 MW. Regional entities, like CRIE (Regional Commission of Electrical Interconnection), EOR (Central American Regional System Operator), and CDMER (Board of Directors of the Central American Market) are working on coordinating the national transmission expansion plans with regional transmission planning efforts. This paper presents experience in Central America region to recommend transmission reinforcements to achieve 300 MW transfer capacity between any pair of member countries of the Central American regional electricity market (MER). This paper also provides a methodology for technical analysis and for coordination among the regional and national entities. This methodology is unique for transmission systems of these characteristics.

Chapter 1. Central nervous system

International Nuclear Information System (INIS)

Planiol, T.; Veyre, A.; Plagne, R.

1975-01-01

The present situation with regard to explorations of the central nervous system by radioactive compounds is reviewed. For the sake of clarity the brain and cerebrospinal fluid examinations are described separately, with emphasis nevertheless on their complementarity. The tracers used in each of these examinations are listed, together with the criteria governing their choice. The different techniques employed are described. Scintigraphy is presented apart from gamma-angio-encephalography since it is not possible with rectilinear scintigraphs to observe the circulatory phase. The results are interpreted by an analysis of normal and pathological aspects of the different stages of the central nervous system [fr

The democratic accountability of the European Central Bank

Directory of Open Access Journals (Sweden)

L. BINI-SMAGHI

1998-06-01

Full Text Available The European Central Bank (ECB is considered to be an institution with a high level of accountability compared with other central banks. However, the matter has yet to be investigated in practice. Accountability of the ECB will have to be checked by governing bodies both within and outside the ECB as well as the public. A survey is undertaken of the main reasons for central bank accountability, especially for the ECB.

Charmed and beauty baryon in hyper central model

International Nuclear Information System (INIS)

Patel, Bhavin; Vinodkumar, P.C.; Rai, Ajay Kumar

2006-01-01

For the present study the hyper central description of the three-body problem has been employed for the baryons constituting one or more charm and beauty quarks. The confinement potential is assumed in the hyper central co-ordinates as hyper central coulomb plus power potential. The charm and beauty baryons under this potential has been studied for different power indices starting from 0.5 to 2.0. The methods and results are briefly described

Neural correlates of central inhibition during physical fatigue.

Directory of Open Access Journals (Sweden)

Masaaki Tanaka

Full Text Available Central inhibition plays a pivotal role in determining physical performance during physical fatigue. Classical conditioning of central inhibition is believed to be associated with the pathophysiology of chronic fatigue. We tried to determine whether classical conditioning of central inhibition can really occur and to clarify the neural mechanisms of central inhibition related to classical conditioning during physical fatigue using magnetoencephalography (MEG. Eight right-handed volunteers participated in this study. We used metronome sounds as conditioned stimuli and maximum handgrip trials as unconditioned stimuli to cause central inhibition. Participants underwent MEG recording during imagery of maximum grips of the right hand guided by metronome sounds for 10 min. Thereafter, fatigue-inducing maximum handgrip trials were performed for 10 min; the metronome sounds were started 5 min after the beginning of the handgrip trials. The next day, neural activities during imagery of maximum grips of the right hand guided by metronome sounds were measured for 10 min. Levels of fatigue sensation and sympathetic nerve activity on the second day were significantly higher relative to those of the first day. Equivalent current dipoles (ECDs in the posterior cingulated cortex (PCC, with latencies of approximately 460 ms, were observed in all the participants on the second day, although ECDs were not identified in any of the participants on the first day. We demonstrated that classical conditioning of central inhibition can occur and that the PCC is involved in the neural substrates of central inhibition related to classical conditioning during physical fatigue.

MRI diagnosis of intraspinal dermoid ruptured into central spinal canal

International Nuclear Information System (INIS)

Zhang Yong; Cheng Jingliang; Wang Juan; Li Huali; Ren Cuiping; Zhang Yan; Gao Xuemei

2009-01-01

Objective: To evaluate the appearances of intraspinal dermoid ruptured into the central spinal canal, as well as the MRI diagnosis and differential diagnosis. Methods: Eleven cases of intraspinal dermoid ruptured into the central spinal canal were reviewed. Six cases underwent whole spine MRI scan, 2 cases with thoracic and lumbar spine MRI, as well as 3 cases only with lumbar spine MRI. Results: Free fat droplets within spinal cord central canal demonstrated high signal intensity on T 1 WI, slight declined signal intensity on T 2 WI, and extremely low signal on fat suppression sequence. Of the 11 cases, 2 cases broke into neighboring central spinal canal of the dermoid, 3 cases scattered within thoracic spinal cord central canal, 4 cases discontinuously distributed in the whole spinal cord central canal, 2 cases showed continuous distribution. Conclusion: Intraspinal dermoid ruptured in the central spinal canal had specific appearance on MRI, when a dermoid tumor is suspected, MRI of the entire spine were recommended to detect possible leakage of' fat within central spinal canal. (authors)

12 CFR 741.210 - Central liquidity facility.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Central liquidity facility. 741.210 Section 741... Unions That Also Apply to Federally Insured State-Chartered Credit Unions § 741.210 Central liquidity... Liquidity Facility, shall adhere to the requirements stated in part 725 of this chapter. ...

Centralized co-digestion and efficient nutrient recycling

Energy Technology Data Exchange (ETDEWEB)

Tafdrup, S [Danish Energy Agency, Copenhagen (Denmark)

1997-08-01

The centralized biogas plants co-digest animal manure and organic waste, producing biogas and liquid fertilizer as a result. 19 centralized biogas plants are in operation in Denmark. In 1996 they digested 200,000 tonnes organic industrial wastes with 800,000 tonnes manure. The average gate fee for waste reception is around DKK 50 per tonne. Thus, the centralized biogas plants provide the organic waste producers with an economically attractive as well as environmentally sound recycling option. The farmers play a key role. It is a precondition that the farmers benefit sufficiently from the operation of the centralized biogas plant. An average economic advantage for the farmers of approximately DKK 5 in all per m{sup 3} slurry has been calculated. Even though this is a relatively modest amount, it is enough to generate interest on the part of the farmers. A further tightening of the legislation is expected in a few years concerning utilization of nutrients in manure and land applied organic wastes. This, together with increasing focus on odour reduction, is expected to add to the farmers interests in centralized biogas plants. At present biogas contributes with 2 PJ per year to the energy supply in Denmark. According to the official energy action plan, the total biogas production from all kinds of biogas plants is to be doubled by the year 2000 and increased 10-fold by the year 2020. A major part of this increase is expected to come from new centralized biogas plants. The annual potential for biogas production from biomass resources available in Denmark is estimated to be approximately 30 PJ. Animal manure comprises about 80% of this potential. (au)

Chromite alteration processes within Vourinos ophiolite

Science.gov (United States)

Grieco, Giovanni; Merlini, Anna

2012-09-01

The renewed interest in chromite ore deposits is directly related to the increase in Cr price ruled by international market trends. Chromite, an accessory mineral in peridotites, is considered to be a petrogenetic indicator because its composition reflects the degree of partial melting that the mantle experienced while producing the chromium spinel-bearing rock (Burkhard in Geochim Cosmochim Acta 57:1297-1306, 1993). However, the understanding of chromite alteration and metamorphic modification is still controversial (e.g. Evans and Frost in Geochim Cosmochim Acta 39:959-972, 1975; Burkhard in Geochim Cosmochim Acta 57:1297-1306, 1993; Oze et al. in Am J Sci 304:67-101, 2004). Metamorphic alteration leads to major changes in chromite chemistry and to the growth of secondary phases such as ferritchromite and chlorite. In this study, we investigate the Vourinos complex chromitites (from the mines of Rizo, Aetoraches, Xerolivado and Potamia) with respect to textural and chemical analyses in order to highlight the most important trend of alteration related to chromite transformation. The present study has been partially funded by the Aliakmon project in collaboration between the Public Power Corporation of Greece and Institute of Geology and Mineral Exploration of Kozani.

Control of gaseous emissions in central Costanera S.A. of Argentina; Control de emisiones gaseosas en central Costanera S. A. de Argentina

Energy Technology Data Exchange (ETDEWEB)

Brabenec, Edgardo [Unidad de Negocios Central Costanera, S. A., (Argentina)

1997-12-31

A description is presented of the equipment utilized at the Central Costanera, S.A. of Argentina, the requirements and the Environmental Management established for this Power Station, and the Standards and the resolutions and law instruments on Environmental issues. Also it is presented the Environmental Management plan of the Ente Nacional Regulador de Electricidad of Argentina as well as the controls and environmental corrective actions implemented at the Central Costanera, S.A. [Espanol] Se presenta una descripcion del equipo utilizado en la Central Costanera S.A. de Argentina, los requerimientos de gestion ambiental establecidos para esta central y las normas, resoluciones e instrumentos juridicos en materia ambiental. Se presenta ademas el plan de gestion ambiental del Ente Nacional Regulador de la Electricidad de Argentina asi como los controles y acciones correctivas ambientales implantadas en la Central Costanera S. A.

Control of gaseous emissions in central Costanera S.A. of Argentina; Control de emisiones gaseosas en central Costanera S. A. de Argentina

Energy Technology Data Exchange (ETDEWEB)

Brabenec, Edgardo [Unidad de Negocios Central Costanera, S. A., (Argentina)

1996-12-31

A description is presented of the equipment utilized at the Central Costanera, S.A. of Argentina, the requirements and the Environmental Management established for this Power Station, and the Standards and the resolutions and law instruments on Environmental issues. Also it is presented the Environmental Management plan of the Ente Nacional Regulador de Electricidad of Argentina as well as the controls and environmental corrective actions implemented at the Central Costanera, S.A. [Espanol] Se presenta una descripcion del equipo utilizado en la Central Costanera S.A. de Argentina, los requerimientos de gestion ambiental establecidos para esta central y las normas, resoluciones e instrumentos juridicos en materia ambiental. Se presenta ademas el plan de gestion ambiental del Ente Nacional Regulador de la Electricidad de Argentina asi como los controles y acciones correctivas ambientales implantadas en la Central Costanera S. A.

Midwifery education in Central-Eastern Europe.

Science.gov (United States)

Mivšek, Polona; Baškova, Martina; Wilhelmova, Radka

2016-02-01

Problems in midwifery in many Central-Eastern European countries are very similar; it is possible to speak about the evolving Central-Eastern model of midwifery care. The educational models of this region have a relatively strong theoretical part; however, there is an insufficient practical dimension. Theoretical part of midwifery education in the universities is relatively autonomous and is slowly changing the professional identity of graduates. Copyright © 2015 Elsevier Ltd. All rights reserved.

Legislation on renewable energy sources in Central America

International Nuclear Information System (INIS)

Rebollo, Jose

2000-01-01

This paper presents the development of renewable energy in Central America and the cooperation given by the European Comission in the promotion of renewable energy sources. Also discuss the current situation in energy demand in Central America and possible solutions linked to legislation that promotes the inversion of the private sector. The legal framework in each country of Central America is presented and its impact in the increasing of generation of energy through tax reductions, trading and prices

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge.

Science.gov (United States)

Stoner, Lee; Bonner, Chantel; Credeur, Daniel; Lambrick, Danielle; Faulkner, James; Wadsworth, Daniel; Williams, Michelle A

2015-08-01

Monitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (augmentation index) responses to a 5 min orthostatic challenge (modified tilt-table). Twenty healthy adults (26.4 y (SD 5.2), 55% F, 24.7 kg/m(2) (SD 3.8)) were tested on 3 different mornings in the fasted state, separated by a maximum of 7 days. Central hemodynamic variables were assessed on the left arm using an oscillometric device. Repeated measures analysis of variance indicated a significant main effect of the modified tilt-table for all central hemodynamic variables (P response to the tilt, central diastolic pressure increased by 4.5 mmHg (CI: 2.6, 6.4), central systolic blood pressure increased by 2.3 (CI: 4.4, 0.16) mmHg, and augmentation index decreased by an absolute - 5.3%, (CI: -2.7, -7.9%). The intra-class correlation coefficient values for central diastolic pressure (0.83-0.86), central systolic blood pressure (0.80-0.87) and AIx (0.79-0.82) were above the 0.75 criterion in both the supine and tilted positions, indicating excellent between-day reliability. Central hemodynamic responses to an orthostatic challenge can be assessed with acceptable between-day reliability using oscillometric pulse wave analysis. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

FUNDUS AUTOFLUORESCENCE LIFETIMES AND CENTRAL SEROUS CHORIORETINOPATHY.

Science.gov (United States)

Dysli, Chantal; Berger, Lieselotte; Wolf, Sebastian; Zinkernagel, Martin S

2017-11-01

To quantify retinal fluorescence lifetimes in patients with central serous chorioretinopathy (CSC) and to identify disease specific lifetime characteristics over the course of disease. Forty-seven participants were included in this study. Patients with central serous chorioretinopathy were imaged with fundus photography, fundus autofluorescence, optical coherence tomography, and fluorescence lifetime imaging ophthalmoscopy (FLIO) and compared with age-matched controls. Retinal autofluorescence was excited using a 473-nm blue laser light and emitted fluorescence light was detected in 2 distinct wavelengths channels (498-560 nm and 560-720 nm). Clinical features, mean retinal autofluorescence lifetimes, autofluorescence intensity, and corresponding optical coherence tomography (OCT) images were further analyzed. Thirty-five central serous chorioretinopathy patients with a mean visual acuity of 78 ETDRS letters (range, 50-90; mean Snellen equivalent: 20/32) and 12 age-matched controls were included. In the acute stage of central serous chorioretinopathy, retinal fluorescence lifetimes were shortened by 15% and 17% in the respective wavelength channels. Multiple linear regression analysis showed that fluorescence lifetimes were significantly influenced by the disease duration (P autofluorescence lifetimes, particularly in eyes with retinal pigment epithelial atrophy, were associated with poor visual acuity. This study establishes that autofluorescence lifetime changes occurring in central serous chorioretinopathy exhibit explicit patterns which can be used to estimate perturbations of the outer retinal layers with a high degree of statistical significance.

Distributed generation and centralized power system in Thailand

DEFF Research Database (Denmark)

Sukkumnoed, Decharut

2004-01-01

The paper examines and discusses conflicts between the development of distributed power and centralized power system.......The paper examines and discusses conflicts between the development of distributed power and centralized power system....

Centralization and Decentralization in American Education Policy

Science.gov (United States)

DeBoer, Jennifer

2012-01-01

This article examines the trend toward centralization in American education policy over the last century through a variety of lenses. The overall picture that emerges is one of a continuous tug-of-war, with national and local policymakers stumbling together toward incrementally more standardized and centralized policies. There is a center of power…

Percutaneous transfemoral repositioning of malpositioned central venous catheters.

Science.gov (United States)

Hartnell, G G; Roizental, M

1995-04-01

Central venous catheters inserted by blind surgical placement may not advance into a satisfactory position and may require repositioning. Malpositioning via surgical insertion is common in patients in whom central venous catheters have previously been placed, as these patients are more likely to have central venous thrombosis and distortion of central venous anatomy. This is less of a problem when catheter placement is guided by imaging; however, even when insertion is satisfactory, central venous catheters may become displaced spontaneously after insertion (Fig. 1). Repositioning can be effected by direct manipulation using guidewires or tip-deflecting wires [1, 2], by manipulation via a transfemoral venous approach [3-5], and by injection of contrast material or saline [6]. Limitations of the direct approach include (1) the number and type of maneuvers that can be performed to effect repositioning when anatomy is distorted, (2) difficulty in accessing the catheter, and (3) the risk of introducing infection. Moreover, these patients are often immunosuppressed, and there is a risk of introducing infection by exposing and directly manipulating the venous catheter. Vigorous injection of contrast material or saline may be unsuccessful for the same reasons: It seldom exerts sufficient force to reposition large-caliber central venous catheters and may cause vessel damage or rupture if injection is made into a small or thrombosed vessel. We illustrate several alternative methods for catheter repositioning via a transfemoral venous approach.

Energy sector developments in Central America and the Caribbean

International Nuclear Information System (INIS)

Perez, J.

1997-01-01

Energy sector developments in Central America and the Caribbean were discussed. Central America is composed of six small countries whose total population is 32 million. The Caribbean population is 20.5 million. Central America is generally poor in hydrocarbon reserves but the geological prospects in several of the countries are encouraging. The oil and petroleum products supply and demand picture, the main characteristics of the hydrocarbon market, structure of the oil industry, hydrocarbon market reforms, pricing issues and recent trend towards reforms in the electric power industry in Central America were discussed. An overview of the Inter-American Development Bank's (IDB) effort to provide technical assistance and loans to strengthen the energy sector development in Central America and the Caribbean was also given. 17 refs., 2 tabs., 23 figs

Fractal systems of central places based on intermittency of space-filling

International Nuclear Information System (INIS)

Chen Yanguang

2011-01-01

Highlights: → The idea of intermittency is introduced into central place model. → The revised central place model suggests incomplete space filling. → New central place fractals are presented for urban analysis. → The average nearest distance is proposed to estimate the fractal dimension. → The concept of distance-based space is replaced by that of dimension-based space. - Abstract: The central place models are fundamentally important in theoretical geography and city planning theory. The texture and structure of central place networks have been demonstrated to be self-similar in both theoretical and empirical studies. However, the underlying rationale of central place fractals in the real world has not yet been revealed so far. This paper is devoted to illustrating the mechanisms by which the fractal patterns can be generated from central place systems. The structural dimension of the traditional central place models is d = 2 indicating no intermittency in the spatial distribution of human settlements. This dimension value is inconsistent with empirical observations. Substituting the complete space filling with the incomplete space filling, we can obtain central place models with fractional dimension D < d = 2 indicative of spatial intermittency. Thus the conventional central place models are converted into fractal central place models. If we further integrate the chance factors into the improved central place fractals, the theory will be able to explain the real patterns of urban places very well. As empirical analyses, the US cities and towns are employed to verify the fractal-based models of central places.

MR findings of central nerocytoma

International Nuclear Information System (INIS)

Lee, Chang Hoon; Kim, Dong Ik; Lee, Byung Hee; Kim, Myung Soon

1997-01-01

Central neurocytoma is a reae neuronal differentiated intraventricular tomor of young adults. The purpose of this study was to evaluate the characteristic MR appearance of central neurocytoma. We retrospectively reviewed MR images of 12 patients with central neurocytoma, confirmed by ultrastructural and immunohistochemical study. We analyzed patient age, and on all sequences, tumor location, extension into the third ventricle, involvement of brain parenchyma, cyst, hemorrhage, vascular signal void and signal intensity ; and egree of Gd-enhancement was examined on MR images, pattern of calcification on CT, and neovascularity, tumor staining on angiography. Age distribution was wide ranging from 26 to 64 years ; the most frequent age group was the fourth decade (five patients). All tumors except one (in the third ventricle) were located in the lateral ventricle and most were seen in the region of the foramen of Monro (10 cases). Tumors showed extension into the third ventricle and involvement of parenchyma in three cases. The internal architecture of the tumor was heterogenous and consisted of cysts (83%), hemorrhage (25%) and vascular signal void (25%). The solid portion of the tumor showed variable signal intensity on T1-weighted images and iso or high signal intensity on T2- and proton density-weighted images. On MR imaging, mild to moderate heterogenous Gd-enhancement was seen in ten cases (83%), and on CT, a spotted, amorphous, nodular pattern of calcifications was seen in seven cases (63%). On angiography, neovasevlarity and tumor staining was seen in three cases (100%). The typical location of the lateral and third ventricles and MR imaging characteristics including variable signal intensity and heterogenous internal architecture are helpful in the diagnosis of central neurocytoma in young adults

Prevalence and lifestyle determinants of central obesity in children.

Science.gov (United States)

Grigorakis, Dimitris A; Georgoulis, Michael; Psarra, Glykeria; Tambalis, Konstantinos D; Panagiotakos, Demosthenes B; Sidossis, Labros S

2016-08-01

Central obesity is a strong risk factor for metabolic disorders and cardiometabolic diseases in children and adolescents. The aim of the present study was to evaluate the prevalence of central obesity and to determine its cross-sectional association with lifestyle habits in a sample of school-aged children in Greece. The study sample consisted of 124,113 children (9.9 ± 1.1 years old, 51 % boys) attending the third and fifth grade of primary school. Anthropometric measurements were performed by trained physical education teachers, and central obesity was defined as waist-to-height ratio ≥0.5. Children's lifestyle habits were assessed through 7-day recall questionnaires. Of the participating children, 33.4 % were classified as centrally obese. Central obesity was significantly more prevalent in boys than in girls (36.0 vs. 30.7 %, P obese children, as well as in a significant percentage of overweight (69.5 %) and normal-weight ones (12.0 %). Children with central obesity, compared to their non-centrally obese counterparts, reported poorer dietary habits and were less physically active. According to multiple logistic regression analysis, frequent breakfast (OR 0.72, 95 % CI 0.69-0.75) and snack consumption (OR 0.70, 95 % CI 0.67-0.74), as well as frequent participation in sedentary activities (OR 1.10, 95 % CI 1.07-1.14), were the strongest lifestyle determinants of central obesity. Strategies for the prevention of central obesity and associated comorbidities are urgently needed, for both obese and non-obese children. Our results suggest the need for a shift towards a healthier environment for our children, with emphasis on specific lifestyle habits, such as regular meal consumption and low sedentariness.

The central noradrenergic system

African Journals Online (AJOL)

2006-07-27

Jul 27, 2006 ... recognition of a direct influence of the central noradrenergic system on peripheral ... influences on cerebral function and behavior it is impossible to imagine ... stimuli and to speed-up information processing.4. The influence of ...

Central nervous system complications in non-Hodgkin-lymphomas and radiotherapy

International Nuclear Information System (INIS)

Liffers, R.

1981-01-01

261 case historys of malignant non-Hodgkin-lymphomas were analysed in the years from 1969 until 1978 in the 'Radiologische Universitaetsklinik Kiel'/West-Germany. 18 Patients got a central nervous complication of Non Hodgkin-Lymphoma earlier or later, a percentage of about 7. There were 7 cases of lymphoblastic lymphoma (LB), a percentage of 10 for this entity. In the group of immunoblastic lymphoma (IB) 6 cases of central nervous infiltration were detected, that is a ratio of 7.7 percent. 4 case histories M. Brill-Symmers (CC/CB) were complicated by central nervous dissemination, a percentage of 5.3. Patients with lymphoblastic lymphoma have the highest risk of central nervous complication. The beginning of central nervous dissemination in the single case histories is very different between the histological groups. Patients with lymphoblastic lymphoma suffered from central nervous complication in an early phase of history, in cases of M. Brill-Symmers central nervous infiltration can occur also in a late phase. The results may determine the discussion about stratifying of radiotherapy. Early radiotherapy including central nervous system may be discussed and investigated in special histological entities of malignant non-Hodgkin-lymphoma. (orig.) [de

Brain MR imaging finding in patients with central vertigo

Energy Technology Data Exchange (ETDEWEB)

Jeong, Chun Keun; Kim, Sang Joon; Kim, You Me; Cha, Min Jung; Lee, Young Seok; Kim, Jae Il; Lee, Geun Ho; Rhee, Chung Koo; Park, Hyun Min [Dankook Univ. College of Medicine, Chonan (Korea, Republic of)

1998-11-01

To investigate brain lesions and their locations in patients with central vertigo, as seen on MR imaging. We retrospectively reviewed MR images of 85 patients with central type vertigo diagnosed on the basis of clinical symptoms and vestibular function test(VFT), and analyzed lesions fand their locations. Those located along the known central vestibular pathway were included in our study. In 29 of 85 patients(34%), lesions considered to be associated with central vertigo were detected on MR imaging. These included infarction(18 patients), hemorrhage(5), tumor(2), cavernous angioma(1), cerebellopontine angle cyst(1), tuberous sclerosis(1) and olivopontocerebellar atrophy (1);they were located in the parietal lobe(6 patients), the lateral medulla(5), the pons(5), the middle cerebellar peduncle(4), the corona radiata(3), and the cerebellar vermis(3). Thirty-eight cases showed high signal intensity lesions in deep cerebral matter, the basal ganglia, and pons but these were considered to be unrelated to central vertigo. MR imaging could be a useful tool for the evaluation of patients with central vertigo.=20.

Brain MR imaging finding in patients with central vertigo

International Nuclear Information System (INIS)

Jeong, Chun Keun; Kim, Sang Joon; Kim, You Me; Cha, Min Jung; Lee, Young Seok; Kim, Jae Il; Lee, Geun Ho; Rhee, Chung Koo; Park, Hyun Min

1998-01-01

To investigate brain lesions and their locations in patients with central vertigo, as seen on MR imaging. We retrospectively reviewed MR images of 85 patients with central type vertigo diagnosed on the basis of clinical symptoms and vestibular function test(VFT), and analyzed lesions fand their locations. Those located along the known central vestibular pathway were included in our study. In 29 of 85 patients(34%), lesions considered to be associated with central vertigo were detected on MR imaging. These included infarction(18 patients), hemorrhage(5), tumor(2), cavernous angioma(1), cerebellopontine angle cyst(1), tuberous sclerosis(1) and olivopontocerebellar atrophy (1);they were located in the parietal lobe(6 patients), the lateral medulla(5), the pons(5), the middle cerebellar peduncle(4), the corona radiata(3), and the cerebellar vermis(3). Thirty-eight cases showed high signal intensity lesions in deep cerebral matter, the basal ganglia, and pons but these were considered to be unrelated to central vertigo. MR imaging could be a useful tool for the evaluation of patients with central vertigo.=20

The interdealer market and the central bank intervention

OpenAIRE

Paula Albuquerque

2005-01-01

This paper studies the consequences of having either an interventionist or a non-interventionist central bank in the foreign exchange market, in a market microstructure framework. Although a simple one-period model is used, it allows the characterization of the effect of the central bank intervention on the behaviour of dealers. The model also identifies the conditions for the dealer that acts as the counterpart of the central bank to be better or worse than the other dealers. The price is ex...

Archives: East and Central African Journal of Surgery

African Journals Online (AJOL)

Items 1 - 40 of 40 ... Archives: East and Central African Journal of Surgery. Journal Home > Archives: East and Central African Journal of Surgery. Log in or Register to get access to full text downloads.

central t

Directory of Open Access Journals (Sweden)

Manuel R. Piña Monarrez

2007-01-01

Full Text Available Dado que la Regresión Ridge (RR, es una estimación sesgada que parte de la solución de la regresión de Mínimos Cuadrados (MC, es vital establecer las condiciones para las que la distribución central t de Student que se utiliza en la prueba de hipótesis en MC, sea también aplicable a la regresión RR. La prueba de este importante resultado se presenta en este artículo.

Reliability of oscillometric central hemodynamic responses to an orthostatic challenge

OpenAIRE

Stoner, Lee; Bonner, Chantel; Credeur, Daniel; Lambrick, Danielle; Faulkner, James; Wadsworth, Daniel; Williams, Michelle A.

2015-01-01

BackgroundMonitoring central hemodynamic responses to an orthostatic challenge may provide important insight into autonomic nervous system function. Oscillometric pulse wave analysis devices have recently emerged, presenting clinically viable options for investigating central hemodynamic properties. The purpose of the current study was to determine whether oscillometric pulse wave analysis can be used to reliably (between-day) assess central blood pressure and central pressure augmentation (a...

An overview of CMS central hadron calorimeter

CERN Document Server

Katta, S

2002-01-01

The central hadron calorimeter for CMS detector is a sampling calorimeter with active medium as scintillator plates interleaved with brass absorber plates. It covers the central pseudorapidity region (¿ eta ¿<3.0). The design and construction aspects are reported. The status of construction and assembly of various subdetectors of HCAL are presented. (5 refs).

Switchings, extensions, and reductions in central digraphs

DEFF Research Database (Denmark)

Kündgen, André; Leander, Gregor; Thomassen, Carsten

2011-01-01

A directed graph is called central if its adjacency matrix A satisfies the equation A2=J, where J is the matrix with a 1 in each entry. It has been conjectured that every central directed graph can be obtained from a standard example by a sequence of simple operations called switchings, and also ...

Visualizing the Central Limit Theorem through Simulation

Science.gov (United States)

Ruggieri, Eric

2016-01-01

The Central Limit Theorem is one of the most important concepts taught in an introductory statistics course, however, it may be the least understood by students. Sure, students can plug numbers into a formula and solve problems, but conceptually, do they really understand what the Central Limit Theorem is saying? This paper describes a simulation…

Central nervous system resuscitation

DEFF Research Database (Denmark)

McIntosh, T K; Garde, E; Saatman, K E

1997-01-01

Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities...

alpha-MSH in systemic inflammation. Central and peripheral actions.

Science.gov (United States)

Catania, A; Delgado, R; Airaghi, L; Cutuli, M; Garofalo, L; Carlin, A; Demitri, M T; Lipton, J M

1999-10-20

Until recently, inflammation was believed to arise from events taking place exclusively in the periphery. However, it is now clear that central neurogenic influences can either enhance or modulate peripheral inflammation. Therefore, it should be possible to improve treatment of inflammation by use of antiinflammatory agents that reduce peripheral host responses and inhibit proinflammatory signals in the central nervous system (CNS). One such strategy could be based on alpha-melanocyte stimulating hormone (alpha-MSH). Increases in circulating TNF-alpha and nitric oxide (NO), induced by intraperitoneal administration of endotoxin in mice, were modulated by central injection of a small concentration of alpha-MSH. Inducible nitric oxide synthase (iNOS) activity and iNOS mRNA in lungs and liver were likewise modulated by central alpha-MSH. Increase in lung myeloperoxidase (MPO) activity was significantly less in lungs of mice treated with central alpha-MSH. Proinflammatory agents induced by endotoxin were significantly greater after blockade of central alpha-MSH. The results suggest that antiinflammatory influences of neural origin that are triggered by alpha-MSH could be used to treat systemic inflammation. In addition to its central influences, alpha-MSH has inhibitory effects on peripheral host cells, in which it reduces release of proinflammatory mediators. alpha-MSH reduces chemotaxis of human neutrophils and production of TNF-alpha, neopterin, and NO by monocytes. In research on septic patients, alpha-MSH inhibited release of TNF-alpha, interleukin-1 beta (IL-1 beta), and interleukin-8 (IL-8) in whole blood samples in vitro. Combined central and peripheral influences can be beneficial in treatment of sepsis.

Monitoring System with Two Central Facilities Protocol

Directory of Open Access Journals (Sweden)

Caesar Firdaus

2017-03-01

Full Text Available The security of data and information on government’s information system required proper way of defending against threat. Security aspect can be achieved by using cryptography algorithm, applying information hiding concept, and implementing security protocol. In this research, two central facilities protocol was implemented on Research and Development Center of Mineral and Coal Technology’s Cooperation Contract Monitoring System by utilizing AES and whitespace manipulation algorithm. Adjustment on the protocol by creating several rule of validation ID’s generation and checking processes could fulfill two of four cryptography objectives, consist of authentication and non-repudiation. The solid collaboration between central legitimization agency (CLA, central tabulating facility (CTF, and client is the main idea in two central facilities protocol. The utilization of AES algorithm could defend the data on transmission from man in the middle attack scenario. On the other hand, whitespace manipulation algorithm provided data integrity aspect of the document that is uploaded to the system itself. Both of the algorithm fulfill confidentiality, data integrity, and authentication.

Central extensions of some Abelian finite gauge groups

International Nuclear Information System (INIS)

Combe, Ph.; Rodriguez, R.; Sirugue, M.; Sirugue-Collin, M.

1981-01-01

The authors describe central extensions of Abelian finite gauge groups on lattices which are permutation invariant. Moreover some remarks are made on the gauge models on lattice associated with these non-commutative central extensions. (Auth.)

Inventory Centralization Decision Framework for Spare Parts

DEFF Research Database (Denmark)

Gregersen, Nicklas; Herbert-Hansen, Zaza Nadja Lee

2018-01-01

Within the current literature, there is a lack of a holistic and multidisciplinary approach to managing spare parts and their inventory configuration. This paper addresses this research gap by examining the key contextual factors which influence the degree of inventory centralization and proposes...... a novel holistic theoretical framework, the Inventory Centralization Decision Framework (ICDF), useful for practitioners. Through an extensive review of inventory management literature, six contextual factors influencing the degree of inventory centralization have been identified. Using the ICDF...... practitioners can assess the most advantageous inventory configuration of spare parts. The framework is tested on a large global company which, as a result, today actively uses the ICDF; thus showing its practical applicability....

Centralized vs. decentralized child mental health services.

Science.gov (United States)

Adams, M S

1977-09-01

One of the basic tenets of the Community Mental Health Center movement is that services should be provided in the consumers' community. Various centers across the country have attempted to do this in either a centralized or decentralized fashion. Historically, most health services have been provided centrally, a good example being the traditional general hospital with its centralized medical services. Over the years, some of these services have become decentralized to take the form of local health centers, health maintenance organizations, community clinics, etc, and now various large mental health centers are also being broken down into smaller community units. An example of each type of mental health facility is delineated here.

Rapid fore-arc extension and detachment-mode spreading following subduction initiation

NARCIS (Netherlands)

Morris, Antony; Anderson, Mark W.; Omer, Ahmed; Maffione, Marco; van Hinsbergen, Douwe J.J.

2017-01-01

Most ophiolites have geochemical signatures that indicate formation by suprasubduction seafloor spreading above newly initiated subduction zones, and hence they record fore-arc processes operating following subduction initiation. They are frequently underlain by a metamorphic sole formed at the top

Composite Sunrise Butte pluton: Insights into Jurassic–Cretaceous collisional tectonics and magmatism in the Blue Mountains Province, northeastern Oregon

Science.gov (United States)

Johnson, Kenneth H.; Schwartz, J.J.; Žák, Jiří; Verner, Krystof; Barnes, Calvin G.; Walton, Clay; Wooden, Joseph L.; Wright, James E.; Kistler, Ronald W.

2015-01-01

shortening and deformation were diachronous, progressing from north to south. We envision that Late Jurassic deformation may have collapsed a Gulf of California–style oceanic extensional basin that extended from the Klamath Mountains (e.g., Josephine ophiolite) to the central Blue Mountains Province, and possibly as far north as the North Cascades (i.e., the coeval Ingalls ophiolite).

Nuclear Energy in Central Europe 98, Proceedings

International Nuclear Information System (INIS)

Ravnik, M.; Jencic, I.; Zagar, T.

1998-01-01

Regional Meeting for Nuclear Energy in Central Europe is an annual meeting of the Nuclear Society of Slovenia. The proceedings contain 63 articles from Slovenia, sorounding countries and countries of the Central and Eastern European Region. Topics are: Research Reactors, Nuclear Methods, Reactor Physics, Thermal Hydraulics, Structural Analysis, Probabilistic Safety Assessment, Severe Accidents, NPP Operation and Nuclear Waste disposal

Central control system for the EAST tokamak

International Nuclear Information System (INIS)

Sun Xiaoyang; Ji Zhenshan; Wu Yicun; Luo Jiarong

2008-01-01

The architecture, the main function and the design scheme of the central control system and the collaboration system of EAST tokamak are described. The main functions of the central control system are to supply a union control interface for all the control, diagnoses, and data acquisition (DAQ) subsystem and it is also designed to synchronize all those subsystem. (authors)

Centralized, Decentralized, and Hybrid Purchasing Organizations

DEFF Research Database (Denmark)

Bals, Lydia; Turkulainen, Virpi

This paper addresses one of the focal issues in purchasing and supply management – global sourcing – from an organizational design perspective. In particular, we elaborate the traditional classification of global sourcing organization designs into centralized, decentralized, and hybrid models. We...... organization we can identify organization designs beyond the classical centralization-decentralization continuum. We also provide explanations for the observed organization design at GCC. The study contributes to research on purchasing and supply management as well as research on organization design....

Central nervous system complications after liver transplantation.

Science.gov (United States)

Kim, Jeong-Min; Jung, Keun-Hwa; Lee, Soon-Tae; Chu, Kon; Roh, Jae-Kyu

2015-08-01

We investigated the diversity of central nervous system complications after liver transplantation in terms of clinical manifestations and temporal course. Liver transplantation is a lifesaving option for end stage liver disease patients but post-transplantation neurologic complications can hamper recovery. Between 1 January 2001 and 31 December 2010, patients who had undergone liver transplantation at a single tertiary university hospital were included. We reviewed their medical records and brain imaging data and classified central nervous system complications into four categories including vascular, metabolic, infectious and neoplastic. The onset of central nervous system complications was grouped into five post-transplantation intervals including acute (within 1 month), early subacute (1-3 months), late subacute (3-12 months), chronic (1-3 years), and long-term (after 3 years). During follow-up, 65 of 791 patients (8.2%) experienced central nervous system complications, with 30 occurring within 1 month after transplantation. Vascular etiology was the most common (27 patients; 41.5%), followed by metabolic (23; 35.4%), infectious (nine patients; 13.8%), and neoplastic (six patients). Metabolic encephalopathy with altered consciousness was the most common etiology during the acute period, followed by vascular disorders. An initial focal neurologic deficit was detected in vascular and neoplastic complications, whereas metabolic and infectious etiologies presented with non-focal symptoms. Our study shows that the etiology of central nervous system complications after liver transplantation changes over time, and initial symptoms can help to predict etiology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Central European projects could alter oil movement patterns

International Nuclear Information System (INIS)

Deffarges, E.H.; Howard, D.J.; Treat, J.E.

1991-01-01

This paper reports that several oil transportation projects are set to transform the flows of oil in Central Europe, with potentially important implications for crude oil and product prices in the region. These projects are spurred by the desires of the newly opened economies of Central Europe to diversify their sources of oil supplies away from the U.S.S.R. and by expectations of economic growth in this region. Today, Central European countries (Poland, Czechoslovakia, Hungary, Yugoslavia, Romania, and Bulgaria) rely heavily on Soviet crude supplies. Of the 1.7 million b/d of crude oil consumed by these six countries, about 55% is imported from the U.S.S.R. This is down significantly from the more than 75% import dependence in the mid-1980s. This dependency on U.S.S.R. crude - for countries that either have a history of indigenous production (Romania) or access to Middle East or North African supplies (Yugoslavia) - testifies to more than 40 years of centrally planned economics in which Moscow provided the energy and raw materials and Central European countries delivered finished goods. Since the end of World War II, the pipeline flow of crude oil and products from Western to Central Europe has been almost nonexistent. In fact, the Western European crude and product pipeline network itself is a rather poorly integrated system, with only limited interconnections between northern and southern networks and no real competition across the major flow routes

Does Al Qaeda Central Still Matter?

Directory of Open Access Journals (Sweden)

Kangil Lee

2015-01-01

Full Text Available El artículo discute si Al Qaeda central es todavía relevante o no. Tras estudiar la actividades de Al Qaeda central cuyo objetivo es provocar la violencia en Afganistán y Pakistán, así como los planes continuos de ataques directos contra los Estados Unidos, el artículo muestra que la capacidad operativa de Al Qaeda es más sólida y fuerte que la que Estados Unidos y otros investigadores y eruditos han anticipado. Además, el apoyo virulento y la contribución Al Qaeda en la Península Arábiga a la red de Al Qaeda muestra que la longevidad de Al Qaeda depende de la relación con sus afiliados. El artículo concluye que, en estas condiciones, Al Qaeda central todavía ocupa un lugar en las discusiones de seguridad global.

Central neurotoxicity of immunomodulatory drugs in multiple myeloma

Directory of Open Access Journals (Sweden)

Urmeel H. Patel

2015-03-01

Full Text Available Immunomodulatory drugs (IMiDs currently used in the treatment of multiple myeloma, are thalidomide, lenalidomide and pomalidomide. One of the most common side effects of thalidomide is neurotoxicity, predominantly in the form of peripheral neuropathy. We report 6 cases of significant central neurotoxicity associated with IMiD therapy. Treatment with thalidomide (1 patient, lenalidomide (4 patients, and pomalidomide (1 patient was associated with various clinical manifestations of central neurotoxicity, including reversible coma, amnesia, expressive aphasia, and dysarthria. Central neurotoxicity should be recognized as an important side effect of IMiD therapy.

Central neurotoxicity of immunomodulatory drugs in multiple myeloma.

Science.gov (United States)

Patel, Urmeel H; Mir, Muhammad A; Sivik, Jeffrey K; Raheja, Divisha; Pandey, Manoj K; Talamo, Giampaolo

2015-02-24

Immunomodulatory drugs (IMiDs) currently used in the treatment of multiple myeloma, are thalidomide, lenalidomide and pomalidomide. One of the most common side effects of thalidomide is neurotoxicity, predominantly in the form of peripheral neuropathy. We report 6 cases of significant central neurotoxicity associated with IMiD therapy. Treatment with thalidomide (1 patient), lenalidomide (4 patients), and pomalidomide (1 patient) was associated with various clinical manifestations of central neurotoxicity, including reversible coma, amnesia, expressive aphasia, and dysarthria. Central neurotoxicity should be recognized as an important side effect of IMiD therapy.

Seismotectonic model of Central Europe

International Nuclear Information System (INIS)

Prochazkova, D.; Roth, Z.

1994-01-01

Earthquakes belong to natural disasters which are associated with tectonic processes in the interior of the Earth. They are extremely devastating in populated areas; they cause human losses and damage personal estates and the environment. To mitigate the potential effects of earthquakes it is necessary that relief and mitigation structures operate following an earthquake, but it is also essential to stimulate and enhance preparedness and prevention. Prevention includes the development of scenarios of potential earthquakes, hazard mapping, formulation of regulations, etc. Preparedness includes the installation and operation of warning systems, establishing communication networks to operate before, during, and after earthquakes. As nuclear technology belongs to high-risk technologies with regard to human health and the environment and its hazard substantially increases in consequence of earthquakes, in the siting of a nuclear plant engineering solutions are generally available to mitigate the potential vibratory effects through design. For the choice of a suitable engineering solution, reliable data must be processed by reliable techniques. The IAEA safety guide of the safety series No. 50-SG-S1(Rev. 1) specifies the demands on data and on their processing and also on the regional seismotectonic model. With a view of this the regional seismotectonic model of Central Europe was created. The paper presents regional geological characteristics of Central Europe and a chronological model of neotectonic movements in Central Europe with specification of neotectonic regional units and their present movements. Moreover, it contains earthquake characteristics for Central Europe and the specification of seismogenic movements. It was found that the genesis of local regions with occurrence of the strongest earthquakes is connected with several movement trends in the last 5 Ma. Six more or less tectonically separate regional units were revealed. The earthquake epicenters often

Understanding the centrality deficit: insight from foreign language learners.

Science.gov (United States)

Miller, Amanda C; Keenan, Janice M

2011-07-01

This study replicated and extended a phenomenon in the text memory literature referred to as the centrality deficit Miller & Keenan (Annals of Dyslexia 59:99-113, 2009). It examined how reading in a foreign language (L2) affects one's text representation and ability to recall the most important information. Readers recalled a greater proportion of central than of peripheral ideas, regardless of whether reading in their native language (L1) or a foreign language (L2). Nonetheless, the greatest deficit in participants' L2 recalls, as compared with L1 recalls, was on the central, rather than the peripheral, information. This centrality deficit appears to stem from resources being diverted from comprehension when readers have to devote more cognitive resources to lower level processes (e.g., L2 word identification and syntactic processing), because the deficit was most evident among readers who had lower L2 proficiency. Prior knowledge (PK) of the passage topic helped compensate for the centrality deficit. Readers with less L2 proficiency who did not have PK of the topic displayed a centrality deficit, relative to their L1 recall, but this deficit dissipated when they did possess PK.

Central dot sign in entities other than Caroli disease

International Nuclear Information System (INIS)

Ahmadi, T.; Itai, Yuji; Minami, Manabu.

1997-01-01

The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ''central dot sign'' on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

Central dot sign in entities other than Caroli disease

Energy Technology Data Exchange (ETDEWEB)

Ahmadi, T.; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine; Minami, Manabu

1997-11-01

The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ``central dot sign`` on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

Budget deficits, monetization, and central-bank independence in developing countries

NARCIS (Netherlands)

Sikken, BJ; de Haan, J

Using various indicators for central bank independence we examine the relationship between central bank independence and government budget deficits. Using a two-stage procedure we also analyze whether central bank independence affects the monetization of deficits. First, the monetization relation in

The organisational structure of protein networks: revisiting the centrality-lethality hypothesis.

Science.gov (United States)

Raman, Karthik; Damaraju, Nandita; Joshi, Govind Krishna

2014-03-01

Protein networks, describing physical interactions as well as functional associations between proteins, have been unravelled for many organisms in the recent past. Databases such as the STRING provide excellent resources for the analysis of such networks. In this contribution, we revisit the organisation of protein networks, particularly the centrality-lethality hypothesis, which hypothesises that nodes with higher centrality in a network are more likely to produce lethal phenotypes on removal, compared to nodes with lower centrality. We consider the protein networks of a diverse set of 20 organisms, with essentiality information available in the Database of Essential Genes and assess the relationship between centrality measures and lethality. For each of these organisms, we obtained networks of high-confidence interactions from the STRING database, and computed network parameters such as degree, betweenness centrality, closeness centrality and pairwise disconnectivity indices. We observe that the networks considered here are predominantly disassortative. Further, we observe that essential nodes in a network have a significantly higher average degree and betweenness centrality, compared to the network average. Most previous studies have evaluated the centrality-lethality hypothesis for Saccharomyces cerevisiae and Escherichia coli; we here observe that the centrality-lethality hypothesis hold goods for a large number of organisms, with certain limitations. Betweenness centrality may also be a useful measure to identify essential nodes, but measures like closeness centrality and pairwise disconnectivity are not significantly higher for essential nodes.

Connecting Students, Creating Futures at Central Campus

Science.gov (United States)

Rosin, Julie; Erbes, Elizabeth; Britt, James; Good, Bill

2012-01-01

Des Moines is an urban community located in the heart of Iowa. Des Moines Public Schools serves 32,000 students in a system with 62 buildings, including Central Campus--a Regional Academy. Central Campus is housed in four buildings, including the main campus at 1800 Grand located on the western edge of downtown Des Moines. As a regional academy,…

Cenozoic Structural and Stratigraphic Evolution of the Ulukışla and Sivas Basins (Central and Eastern Turkey)

Science.gov (United States)

Gürer, Derya; Darin, Michael H.; van Hinsbergen, Douwe J. J.; Umhoefer, Paul J.

2017-04-01

Because subduction is a destructive process, the surface record of subduction-dominated systems is naturally incomplete. Sedimentary basins may hold the most complete record of processes related to subduction, accretion, collision, and ocean closure, and thus provide key information for understanding the kinematic evolution of orogens. In central and eastern Anatolia, the Late Cretaceous-Paleogene stratigraphic record of the Ulukışla and Sivas basins supports the hypothesis that these once formed a contiguous basin. Importantly, their age and geographic positions relative to their very similar basement units and ahead of the Arabian indenter provide a critical record of pre-, syn- and post-collisional processes in the Anatolian Orogen. The Ulukışla-Sivas basin was dissected and translated along the major left-lateral Ecemiş fault zone. Since then, the basins on either side of the fault evolved independently, with considerably more plate convergence accommodated to the east in the Sivas region (eastern Anatolia) than in the Ulukışla region (central Anatolia). This led to the deformation of marine sediments and underlying ophiolites and structural growth of the Sivas Fold-and-Thrust Belt (SSFTB) since latest Eocene time, which played a major role in marine basin isolation and disconnection, along with a regionally important transition to continental conditions with evaporite deposition starting in the early Oligocene. We use geologic mapping, fault kinematic analysis, paleomagnetism, apatite fission track (AFT) thermochronology, and 40Ar/39Ar geochronology to characterize the architecture, deformation style, and structural evolution of the region. In the Ulukışla basin, dominantly E-W trending normal faults became folded or inverted due to N-S contraction since the Lutetian (middle Eocene). This was accompanied by significant counter-clockwise rotations, and post-Lutetian burial of the Niǧde Massif along the transpressional Ecemiş fault zone. Since Miocene

Nonlinear Squeeze Film Dampers without Centralized Springs

Directory of Open Access Journals (Sweden)

Zhu Changsheng

2000-01-01

Full Text Available In this paper, the bifurcation behavior of a flexible rotor supported on nonlinear squeeze film dampers without centralized springs is analyzed numerically by means of rotor trajectories, Poincar maps, bifurcation diagrams and power spectra, based on the short bearing and cavitated film assumptions. It is shown that there also exist two different operations (i.e., socalled bistable operations in some speed regions in the rotor system supported on the nonlinear squeeze film dampers without centralized springs. In the bistable operation speed regions, the rotor system exhibits synchronous, sub-synchronous, sub-super-synchronous and almost-periodic as well as nonperiodic motions. The periodic bifurcation behaviors of the rotor system supported on nonlinear squeeze film dampers without centralized springs are very complex and require further investigations.

Centralized versus distributed propulsion

Science.gov (United States)

Clark, J. P.

1982-01-01

The functions and requirements of auxiliary propulsion systems are reviewed. None of the three major tasks (attitude control, stationkeeping, and shape control) can be performed by a collection of thrusters at a single central location. If a centralized system is defined as a collection of separated clusters, made up of the minimum number of propulsion units, then such a system can provide attitude control and stationkeeping for most vehicles. A distributed propulsion system is characterized by more numerous propulsion units in a regularly distributed arrangement. Various proposed large space systems are reviewed and it is concluded that centralized auxiliary propulsion is best suited to vehicles with a relatively rigid core. These vehicles may carry a number of flexible or movable appendages. A second group, consisting of one or more large flexible flat plates, may need distributed propulsion for shape control. There is a third group, consisting of vehicles built up from multiple shuttle launches, which may be forced into a distributed system because of the need to add additional propulsion units as the vehicles grow. The effects of distributed propulsion on a beam-like structure were examined. The deflection of the structure under both translational and rotational thrusts is shown as a function of the number of equally spaced thrusters. When two thrusters only are used it is shown that location is an important parameter. The possibility of using distributed propulsion to achieve minimum overall system weight is also examined. Finally, an examination of the active damping by distributed propulsion is described.

Centrally Banked Cryptocurrencies

OpenAIRE

Danezis, George; Meiklejohn, Sarah

2015-01-01

Current cryptocurrencies, starting with Bitcoin, build a decentralized blockchain-based transaction ledger, maintained through proofs-of-work that also generate a monetary supply. Such decentralization has benefits, such as independence from national political control, but also significant limitations in terms of scalability and computational cost. We introduce RSCoin, a cryptocurrency framework in which central banks maintain complete control over the monetary supply, but rely on a distribut...

Centrally Banked Cryptocurrencies

OpenAIRE

Danezis, G.; Meiklejohn, S.

2016-01-01

Current cryptocurrencies, starting with Bitcoin, build a decentralized blockchain-based transaction ledger, maintained through proofs-of-work that also serve to generate a monetary supply. Such decentralization has benefits, such as independence from national political control, but also significant limitations in terms of computational costs and scalability. We introduce RSCoin, a cryptocurrency framework in which central banks maintain complete control over the monetary supply, but rely on...

A centralized audio presentation manager

Energy Technology Data Exchange (ETDEWEB)

Papp, A.L. III; Blattner, M.M.

1994-05-16

The centralized audio presentation manager addresses the problems which occur when multiple programs running simultaneously attempt to use the audio output of a computer system. Time dependence of sound means that certain auditory messages must be scheduled simultaneously, which can lead to perceptual problems due to psychoacoustic phenomena. Furthermore, the combination of speech and nonspeech audio is examined; each presents its own problems of perceptibility in an acoustic environment composed of multiple auditory streams. The centralized audio presentation manager receives abstract parameterized message requests from the currently running programs, and attempts to create and present a sonic representation in the most perceptible manner through the use of a theoretically and empirically designed rule set.

Alternative Fuels Data Center: Central Ohio Turns Trash Into Natural Gas

Science.gov (United States)

Central Ohio Turns Trash Into Natural Gas to someone by E-mail Share Alternative Fuels Data Center : Central Ohio Turns Trash Into Natural Gas on Facebook Tweet about Alternative Fuels Data Center: Central Ohio Turns Trash Into Natural Gas on Twitter Bookmark Alternative Fuels Data Center: Central Ohio Turns

[The unnecessary application of central venous catheterization in surgical patients].

Science.gov (United States)

Uemura, Keiko; Inoue, Satoki; Kawaguchi, Masahiko

2018-04-06

Perioperative physicians occasionally encounter situations where central venous catheters placed preoperatively turn out to be unnecessary. The purpose of this retrospective study is to identify the unnecessary application of central venous catheter placement and determine the factors associated with the unnecessary application of central venous catheter placement. Using data from institutional perioperative central venous catheter surveillance, we analysed data from 1,141 patients who underwent central venous catheter placement. We reviewed the central venous catheter registry and medical charts and allocated registered patients into those with the proper or with unnecessary application of central venous catheter according to standard indications. Multivariate analysis was used to identify factors associated with the unnecessary application of central venous catheter placement. In 107 patients, representing 9.38% of the overall population, we identified the unnecessary application of central venous catheter placement. Multivariate analysis identified emergencies at night or on holidays (odds ratio [OR] 2.109, 95% confidence interval [95% CI] 1.021-4.359), low surgical risk (OR=1.729, 95% CI 1.038-2.881), short duration of anesthesia (OR=0.961/10min increase, 95% CI 0.945-0.979), and postoperative care outside of the intensive care unit (OR=2.197, 95% CI 1.402-3.441) all to be independently associated with the unnecessary application of catheterization. Complications related to central venous catheter placement when the procedure consequently turned out to be unnecessary were frequently observed (9/107) compared with when the procedure was necessary (40/1034) (p=0.032, OR=2.282, 95% CI 1.076-4.842). However, the subsequent multivariate logistic model did not hold this significant difference (p=0.0536, OR=2.115, 95% CI 0.988-4.526). More careful consideration for the application of central venous catheter is required in cases of emergency surgery at night or on

Endogenous Central Bank Information and the Optimal Degree of Transparency

OpenAIRE

Romain Baeriswyl

2011-01-01

As a policymaker, the central bank both observes and shapes the economy. The central bank scrutinizes market activity to assess the state of the economy, and its policy strongly shapes market outcomes. When transparency allows the central bank to shape the economy more effectively, it may also cause the informational role of the economic aggregate to deteriorate. This paper presents a simple model to capture the endogenous nature of central bank information and to address welfare issues. Firs...

CMS Central Hadron Calorimeter

OpenAIRE

Budd, Howard S.

2001-01-01

We present a description of the CMS central hadron calorimeter. We describe the production of the 1996 CMS hadron testbeam module. We show the results of the quality control tests of the testbeam module. We present some results of the 1995 CMS hadron testbeam.