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Interplay between the glass and the gel transition

Science China(Physics,Mechanics & Astronomy) 2019年第10期62卷 45-50页

作者： Annalisa Fierro antonio de Candia antonio coniglio CNR-SPIN c/o Complesso di Monte S.AngeloNapoli 80126Italy Dipartimento di Fisica"Pancini" Universita di Napoli"FedericoⅡ"Complesso di Monte S.AngeloNapoli 80126Italy

By changing the control parameters, many physical systems reach a slow dynamics regime followed by an arrested or a quasiarrested state. Examples, among others, are gels and glasses. In this paper, we discuss some experimental and theoretical results in polymer and colloidal systems, where gel and glass transitions interfere, and use models from Mode Coupling Theory（MCT）to illustrate the rich phenomenology observed. The continuous and the discontinuous transition lines, found in the MCT models,are considered suitable to describe respectively the gel and the glass transitions, so we suggest that the interplay between gel and glass may be interpreted in terms of the F13 MCT model, clarifying also the origin of logarithmic decays often observed in such systems. In particular, the theoretical predictions of the MCT in the F13 model are compared with Molecular Dynamics simulations in model systems for chemical gels and charged colloids.

关键词： glass gel and sol colloid

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Mantle derived crystal-poor rhyolitic ignimbrites:Eruptive mechanism from geochemical and geochronological data of the Piedra Parada caldera,Southern Argentina

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Geoscience Frontiers 2018年第5期9卷 1529-1553页

作者： Eugenio Aragon antonio Castro Juan Diaz-Alvarado Lucio Pinotti Fernando D'eramo Manuel Demartis Jorge coniglio Irene Hernando Carmen Rodriguez Centro de Investigaciones Geológicas(UNLP-CONICET) 1 N^o 644(1900)La PlataBuenos AiresArgentina Departamento de Geología Universidad de Huelva21071 HuelvaSpain Departamento de Geología Universidad de AtacamaCopayapu 485CopiapóChile Departamento de Geología Universidad Nacional de Río Cuarto(UNRC-CONICET)Ruta 36 km 601Río CuartoCórdobaArgentina

Trace elements, isotopic modeling and U-Th-Pb SHRIMP zircon age constraints are used to reconstruct the eruption history and magmatic processes of the Piedra Parada Caldera. In the early Eocene, the crystal-poor Barda Colorada ignimbrite(BCI), having >>15% micro-porphyritic crystals with respect to magmatic components, erupted a volume estimated in more than 300 km^3. The Piedra Parada caldera is located in the Patagonian Andes foreland, at the southern end of the calderas field of the Pilcaniyeu Volcanic Belt(PVB). This belt is related to an extensional tectonic setting as a result of the collision of the Farallon-Aluk ridge with South America, which enabled the development of a transform ocean/continental plate margin followed by the detachment of the Aluk plate and the opening of a slab window. The BCI extra-caldera Plateau is a >100 m thick deposit, having a lower unit with high silica(Si O_2> 76 wt.%),potassium poor rhyolitic composition(trondhjemitic like magma), and an upper unit with normal to high potassium rhyolitic composition(granitic like magma). A trace elements modeling of the BCI units shows that the BCI lower and upper units did not evolve from fractionation or immiscibility in the shallow magma reservoir. The BCI also have a primitive isotopic signature(initial87 Sr/86 Sr =0.7031-0.7049 and ε_(Nd)= +3.4 to +3.65). Thus, tectonic, compositional and isotopic constraints suggest the fast ascent of high silica magmas to a shallow reservoir, and point to an upper mantle origin for these rhyolitic magmas in a transitional(Orogenic-Anorogenic) tectono-magmatic setting. U-Th-Pb SHRIMP zircon crystallization ages of the Syn-caldera stage BCI units(56 -51.5 Ma) show a protracted life of 5 Ma for this caldera reservoir. The age of 52.9 ± 0.3 Ma is considered the best fit for the possible maximum age for the caldera collapse. The Late-caldera magmatism has trachyandesitic and rhyolitic *** trace element modeling suggests that these rhyolites evolv

关键词： Mantle derived rhyolite Crystal-poor ignimbrite Bimodal volcanism Slab window volcanism K poor-rhyolite

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The Farallon-Aluk ridge collision with South America:Implications for the geochemical changes of slab window magmas from fore- to back-arc

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Geoscience Frontiers 2013年第4期4卷 377-388页

作者： Eugenio Aragón Lucio Pinotti Fernando D'Eramo antonio Castro Osvaldo Rabbia Jorge coniglio Manuel Demartis Irene Hernando Claudia E.Cavarozzi Yolanda E.Aguilera Centro de Investigaciones Geologicas(UNLP-CONICET) 1 N°644(1900) La Plata.Buenos Aires.Argentina Facultad de Ciencias Naturales y Museo Universidad Nacional de la Plata122 y 60s/n.(1900).La PlataBuenos AiresArgentina Departamento de Geologia.Universidad Nacional de Rio Cuarto.(UNRC-CONICET).Ruta 36 km 601.Rio Cuarto.Cordoba.Argentina Departamento de Geologia.Universidad de Huelva.21071 Huelva.Spain Instituto de Geologia Economica Aplicada.Universidad de Concepcion.Concepcion.Chile Departamento de Geologia.Universidad Nacional de Rio Cuarto.(UNRC-CONICET) Ruta 36 km 601.Rio Cuarto.CordobaArgentina Centro de Investigaciones Geologicas(UNLP-CONICET).1 N°644.(1900) La Plata.Buenos Aires.Argentina Facultad de Ciencias Naturales y Museo.Universidad Nacional de la Plata.122 y 60 s/n.(1900).La PlataBuenos Aires.Argentina Facultad de Ciencias Naturales y Museo.Universidad National dela Plata.122 y 60 s/n(1900)La Plata.Buenos Aires.Argentina Direccion de Aplicacion de Imagenes Satelitarias(M.O.S.P.).58 e/ 7 y 8.piso 2.1900 La Plata.Buenos Aires.Argentina

The collision of a divergent ocean ridge may evolve into two end cases： in the continuity of ocean-floor subduction, or in the detachment of the subducted plate. The northern Patagonia active plate margin has the unique situation that in Cenozoic time it has been subjected to two divergent ridge collisions, each one representing one of the end members. The Neogene Antarctica-Nazca divergent ridge collision evolved as a continuous ocean-floor subduction system, promoting a magmatic hiatus at the arc axis, the obduction of part of the ridge ocean-floor in the fore-arc, and basaltic volcanism in the back-arc. In contrast, the Paleogene Farallon-Aluk divergent ridge collision evolved into a transform margin, with the detachment and sinking of the Aluk plate and the development of a large slab window. As in the previous case, this collision promoted a magmatic hiatus at the arc axis, but the tectono-magmatic scenario changed to postorogenic synextensional volcanism that spread to the former fore-arc （basalt, andesite, rhyolite） and former back-arc （bimodal ignimbrite flare-up, basalt）. Geochemistry of this slab window synextensional volcanism shows more MORB-like basalts towards the former fore-arc, and MORB-OIB-Iike basalts towards the former back-arc. Instead, an isolated undeformable crustal block in the former back-arc, with an ＂epeirogenic＂ response to the slab window and extensional regime, was covered by OIB-type basalts after uplift. Major elements show that slab window basalts reach TiO2 values up to 3 wt%, as compared with the top value of 1.5 wt% of arc magmas. Besides, the MgO with respect to （FeOt ＋ A1203） ratio helps to distinguish slab window magma changes from the former fore-arc to the former back-arc and also with respect to the ＂epeirogenic＂ block. Higher contents of HFS elements such as Nb and Ta also help to distinguish this slab window from arc magmas and also, to distinguish slab window magma changes from the former fore-arc to the former back-arc

关键词： AndesActive ridge collisionSubduction-transform transitionSlab window volcanismSynextensional calc-alkalineBimodal volcanism

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