Malusa M.G.,University of Milan Bicocca |
Villa I.M.,University of Milan Bicocca |
Villa I.M.,Institute For Geologie |
Vezzoli G.,University of Milan Bicocca |
Garzanti E.,University of Milan Bicocca
Earth and Planetary Science Letters | Year: 2011
Tectonic reconstructions and quantitative models of landscape evolution are increasingly based on detailed analysis of detrital systems. Since the definition of closure temperature in the 1960s, mineral ages of low-temperature geochronometers are traditionally interpreted as the result of cooling induced by erosion, whose rate is a simple, unique function of age patterns. Such an approach can lead to infer paradoxically high erosion rates that conflict with compelling geological evidence from sediment thickness in basins. This indicates that tectonic and landscape models that solely interpret mineral ages as due to cooling during exhumation may not be valid.Here we propose a new approach that takes into account the effects of both crystallization and exhumational cooling on geochronometers, from U-Pb on zircon to fission tracks on apatite. We first model the mechanical erosion of an unroofing magmatic complex and the resulting accumulation and burial of the eroded units in reverse order in the basin. Detrital mineral ages follow a regular pattern downsection. Some mineral ages, such as e.g. U-Pb ages of zircons, cluster around the "magmatic age", i.e. the crystallization of the magma. Its value is constant along the stratigraphic column in the sedimentary basin; we refer to this behavior as "stationary age peak". Some other mineral ages, such as e.g. apatite fission-track ages, are often younger than the magmatic age. When they vary smoothly with depth, they define a "moving age peak", which is the only possible effect of undisturbed cooling during overburden removal, and can therefore be used to calculate an erosion rate.The predictions of our model were tested in detail on the extremely well-studied Bregaglia (Bergell) orogenic pluton in the Alps, and on the sedimentary succession derived from its erosion, the Gonfolite Group. The consistency between predicted and observed age patterns validates the model. Our results resolve a long-standing paradox in quantitative modelling of erosion-sedimentation, namely the scarcity of sediment during apparently fast erosion. Starved basins are the observational baseline, and modelling must be tuned to include a correct analysis of detrital mineral geochronology in order to reconcile perceived discrepancies between stratigraphical and geochronological information. In addition, our data demonstrate that volcanoes were active on top of the growing Oligocene Alps.This study illustrates rigorous criteria for detrital mineral geochronology that are applicable to any geological setting, including magmatic arcs and collision orogens, and provides fundamental interpretive keys to solve complex puzzles and apparent paradoxes in geological reconstructions. © 2010 Elsevier B.V.
Gies H.,Institute For Geologie |
Muller U.,BASF |
Yilmaz B.,BASF |
Feyen M.,BASF |
And 10 more authors.
Chemistry of Materials | Year: 2012
The hydrous layer silicate RUB-36, (C 6H 16N) 4 [H 4Si 36O 76], has been used for an interlayer expansion reaction with dichlorodimethylsilane to interconnect neighboring ferrierite-type layers to a three-dimensional framework silicate. The linker group (-O-Si(CH 3) 2-O-) still has the two methyl groups in the as-synthesized form (material name COE-3 [Si 20O 38(CH 3) 4] for the silicate framework) rendering hydrophobic properties. The interlayer expanded zeolite, IEZ, is thermally stable and can be calcined at 550 °C to yield a hydrophilic material COE-4 [Si 20O 38(OH) 4]. 29Si solid state MAS NMR experiments confirm the insertion of the linker group and the methyl and hydroxyl substitution in the as-made and calcined form, respectively. The BET surface area is 238 m 2/g for COE-3 and 350 m 2/g for COE-4. COE-3 and COE-4 crystallize in space group Pm with a = 12.2503(3) Å b = 13.9752(2) Å c = 7.3850(1) Å and β = 107.33(1)° and a = 12.16985(4) Ã?, b = 13.95066(3) Å c = 7.37058(2) Å, and β = 107.30(1)°, respectively. Rietveld crystal structure refinement of the PXRD pattern of COE-3 and COE-4 reveal the expanded, two-dimensional 10-ring pore system including the linker group as homogeneous structural property of the materials. © 2012 American Chemical Society.
Steck A.,University of Lausanne |
Masson H.,University of Lausanne |
Robyr M.,Institute For Geologie
Swiss Journal of Geosciences | Year: 2015
The Monte Rosa basement fold nappe, surrounded by other continental units of the Briançonnais s.l. domain and ophiolites of the Piemont Ocean, represents a major structure of the Pennine Alps situated at the border of the Canton Valais (Switzerland) and Italy. The Central Alps were formed during the collision and SE-directed underthrusting of the European below the Adriatic plate by successive underthrusting, detachment and accretion of the Austroalpine Sesia continental crust, the Piemont oceanic crust and the continental Briançonnais–Europe plate border. The 90–60 Ma Sesia high-pressure metamorphism, followed by the 50–38 Ma Zermatt-Saas Fee and Monte Rosa high-pressure metamorphism, and since 40 Ma by the Barrovian regional metamorphism, reveal a long-lasting Alpine evolution during convergence of both plates. The superposition of the ultra-high pressure Zermatt-Saas Fee ophiolites by the continental Cimes Blanche unit of the Briançonnais domain and the medium pressure ophiolitic Tsaté nappe is explained by delamination and tectonic flake detachment of the Cimes Blanches from the Briançonnais crust and its south directed thrust over the Zermatt-Saas Fee and Tsaté ophiolites. The main ductile deformational structures, related to the NW-directed nappe emplacement, were generated after 40 Ma under greenschist to amphibolite facies Barrovian orogenic metamorphism. Early extrusional structures have been transposed by the younger thrust structures. The NW-directed thrust of the Alps was accompanied since about 35 Ma by ductile dextral shear and backfolding in the zone of dextral transpression between the converging European and Adriatic plates. © 2015, Swiss Geological Society.
Zhang H.,Jilin University |
Xie B.,Jilin University |
Meng X.,Zhejiang University |
Muller U.,BASF |
And 9 more authors.
Microporous and Mesoporous Materials | Year: 2013
Beta zeolite as efficient catalyst has been widely used in industrial processes, and its synthesis is normally performed in the presence of tetraethylammonium hydroxide as organic template. Recent works show successful organotemplate-free and seed-directed synthesis of Beta zeolite (Beta-SDS) in the presence of Beta seeds at 140 C, providing a novel route for synthesizing low-cost zeolite catalysts. Notably, in the case for synthesizing Beta-SDS at 140 C (Beta-SDS140), the use of seeds is still very high (8-10% in silica source) and impurity of MOR zeolite easily appears due to the fast crystallization rate. We demonstrate here a rational synthesis of Beta-SDS at 120 C (Beta-SDS120) with pure BEA structure and improved zeolite quality in the presence of a very small amount of Beta seeds (as low as 1.4%) by decreasing zeolite crystallization rate. X-ray diffraction patterns show that calcination at 550 C for 4 h results in the loss of crystallinity at 8.0% and 15.8% for Beta-SDS120 and Beta-SDS140, respectively, suggesting that Beta-SDS120 has higher thermal stability than Beta-SDS140. N2 adsorption isotherms show that Beta-SDS120 has much higher surface area (655 m2/g) and micropore volume (0.25 cm3/g) than Beta-SDS140 (450 m 2/g, 0.18 cm3/g). These phenomena are reasonably assigned to that Beta-SDS120 samples have much less framework defects such as terminal Si-OH groups than Beta-SDS140. The Beta-SDS120 samples with good crystallinity, high thermal stability, large surface area and pore volume offer a good opportunity for their industrial applications as efficient and low-cost catalytic and adsorptive materials.© 2013 Elsevier Inc. All rights reserved.
Cenki-Tok B.,Montpellier University |
Berger A.,Institute For Geologie |
Gueydan F.,Montpellier University
International Journal of Earth Sciences | Year: 2015
Highly restitic rocks from the Antananarivo Block in northern Madagascar are investigated in this study in order to unravel processes of H2O-rich biotite formation in HT rocks. Polyphase metamorphism and melt migration occurred at 0.6 GPa and 850 °C. Biotite remains stable together with orthopyroxene and makes up to 45 vol% of the rock. In addition, three well-characterised and delimited microdomains having different textural, chemical and petrological characteristics are preserved. Thermodynamic models using the specific bulk compositions of the domains are in agreement with petrological observations. These rocks provide evidence that the lower crust may be strongly heterogeneous, locally associated to the formation of hydrous restites controlled by episodes of melt production and melt escape. This has significant consequences for understanding of the lower crust. © 2015 Springer-Verlag Berlin Heidelberg