Search results for "PACE"
showing 10 items of 21903 documents
Os isotopes and highly siderophile elements (HSE) in the Ligurian Ophiolites, Italy.
2000
The Os isotopic and highly siderophile element (HSE) concentration systematics of the upper mantle have been the focus of much recent interest. However, little systematic study has addressed the combined HSE and Os isotopes in mantle rocks from MOR ophiolites. The Ligurian ophiolites in northern Italy represent an important class of ophiolites representing, like Zabargad or the Galicia margin, crust with clear ocean ridge affinity floored by older mantle with arguably more continental affinities [Rampone et al., J. Petrol. 36, 18–105, 1995; Rampone et al., Contrib. Mineral. Petrol. 123, 61–67, 1996]. We have studied a suite of 15 geochemically and geologically well characterized mantle peri…
Craton reactivation on the Labrador Sea margins: 40Ar/39Ar age and Sr–Nd–Hf–Pb isotope constraints from alkaline and carbonatite intrusives
2007
Abstract The once-contiguous North Atlantic craton (NAC) is crosscut by the Labrador Sea that opened during the Early Cenozoic after extensive Mesozoic continental rifting and removal of cratonic mantle. This large-scale structural change within the cratonic lithosphere was followed at about 150 Ma by the cessation of ultrapotassic and potassic-to-carbonatitic magma production, which had prevailed throughout much of the NAC history. At Aillik Bay, a sequence of olivine lamproites (1374.2 ± 4.2 Ma, 2σ), aillikites/carbonatites (590–555 Ma), and nephelinites (141.6 ± 1.0 Ma, 2σ) erupted through the southern NAC edge on the present-day Labrador Sea margin. Links between these alkaline magma ty…
Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records
2015
Abstract A comprehensive understanding of explosive basaltic eruption processes in the deep-sea relies upon detailed analysis and comparison of the variety of volcaniclastic lithologies on the seafloor, which has been challenged by insufficient sample recovery. A dedicated ROV-based sampling approach using long push cores offers an unparalleled opportunity to fully characterize the diversity of unconsolidated volcaniclastic lithofacies on a recently active seamount. Lithofacies from Axial Seamount record two styles of pyroclastic eruptions, strombolian and phreatomagmatic, at 1.5 km water depth. Strombolian eruptions are represented by abundant fluidal and highly vesicular (up to 50%) vitri…
Recycling and transport of continental material through the mantle wedge above subduction zones: A Caribbean example
2016
Abstract Estimates of global growth rates of continental crust critically depend upon knowledge of the rate at which crustal material is delivered back into the mantle at subduction zones and is then returned to the crust as a component of mantle-derived magma. Quantification of crustal recycling by subduction-related magmatism relies on indirect chemical and isotopic tracers and is hindered by the large range of potential melt sources (e.g., subducted oceanic crust and overlying chemical and clastic sediment, sub-arc lithospheric mantle, arc crust), whose composition may not be accurately known. There is also uncertainty about how crustal material is transferred from subducted lithosphere …
Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem
2013
Abstract We present a speleothem stable oxygen isotope record for the last 12.5 ka based on two stalagmites from western Cuba. The δ18O signal is interpreted to represent past precipitation variability. Both stalagmites show a pronounced transition from higher δ18O values (indicating drier conditions) to more negative δ18O values (suggesting wetter conditions) between 10 and 6 ka. This transition is also visible in a planktonic δ18O record off Haiti. On orbital timescales, the δ18O value of Caribbean precipitation, thus, strongly resembles the oxygen isotope composition of Caribbean surface water. On millenial timescales, the speleothem δ18O record shows a high correlation to a North Atlant…
Ice age at the Middle–Late Jurassic transition?
2003
A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (δ18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle–Late Callovian widespread dep…
Pants complex, TQFT and hyperbolic geometry
2021
We present a coarse perspective on relations of the $SU(2)$-Witten-Reshetikhin-Turaev TQFT, the Weil-Petersson geometry of the Teichm\"uller space, and volumes of hyperbolic 3-manifolds. Using data from the asymptotic expansions of the curve operators in the skein theoretic version of the $SU(2)$-TQFT, as developed by Blanchet, Habegger, Masbaum and Vogel, we define the quantum intersection number between pants decompositions of a closed surface. We show that the quantum intersection number admits two sided bounds in terms of the geometric intersection number and we use it to obtain a metric on the pants graph of surfaces. Using work of Brock we show that the pants graph equipped with this …
Polski i ukraiński nauczyciel w kontekście globalizacji w europejskiej przestrzeni edukacyjnej
2014
The book attempts to release space of Polish and Uk rainian teacher in a globalized community. This theme has proved to be the most present because both countries are transforming to the information society related to the transition of the international community to the new development strategy. Intellec tual potential of the man and his education appears in the strategic sources and these are the top priorities for all countries of the world. In that sense education appears as a factor in the success of their own identity, its activity, creativity and freedom. For the present time characteristic thing is that the most of countries come to the educational policies with the perpetuation of t…
Determinanty współpracy studentów i wykładowców jako czynnik optymalizacji zawodowego przygotowania nauczycieli w Polsce i na Ukrainie
2015
W artykule postawiono tezę, że głównym zadaniem nauk pedagogicznych jest stworzenie prawidłowo funkcjonującego systemu edukacji zawodowej przyszłego nauczyciela, nakreślenie kierunków ukraińskich innowacji, jak również możliwości współpracy w tych sektorach ukraińskich i polskich nauczycieli. W artykule poruszono również problem interakcji pedagogicznej jako społecznej i psychologicznej adaptacji i dostosowania procesu tworzenia i rozwoju osobistego przyszłego nauczyciela w kontekście globalizacji społeczeństwa opartego na wiedzy.
I ‘graffi’ della protesta. Street art, barriere artificiali e forme di espressione del dissenso
2013
Street art is any art – specifically visual art – developed in public spaces. It can include traditional graffiti artwork, stencil, sculpture, sticker art, street poster art, video projection, guerrilla art, flash mobbing, wheatpasting, etc. Typically, the term is used to refer to unsanctioned or “prohibited” art, as opposed to institutional artistic initiatives. So, is it possible to speak about street art as a form of protest art? If so, what are the signs, texts, codes and practices through which graffiti, stencils and other forms of street art can serve as means to express opposition and dissent? The present paper aims at answering these questions at first through a general historic int…