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Spikings R.A.,University of Geneva | Crowhurst P.V.,Teck Cominco Ltd. | Winkler W.,ETH Zurich | Villagomez D.,University of Geneva
Journal of South American Earth Sciences

New 40Ar/39Ar, apatite fission track and (U-Th)/He data from the late Cretaceous indenting and buttressing margins of Ecuador have been combined with previous thermochronological studies to constrain the timing of syn- and post-accretionary tectonic events in the Ecuadorian Andes to within ±1 Ma. Our interpretations are more accurate than previous hypotheses because i) they are more sensitive to lower temperatures (<60 °C), ii) we directly compare data obtained from in-situ and detrital rocks, and iii) they are constrained by recently published palaeomagnetic, stratigraphic and geochronological data. The response of the buttressing Ecuadorian margin to the collision of the Caribbean Plateau and its overlying arc was diachronous. Exhumation occurred as an immediate response to collision at ∼75 Ma, south of S1°30', whereas the northern region started to exhume at ∼65 Ma, suggesting that accretion may have been oblique. Elevated cooling and exhumation rates within specific massifs dispersed along the entire length of the Ecuadorian cordilleras, during 43-30 and 25-18 Ma, are attributed to i) an increase in convergence rates between the Farallon and South American plates during 42-37 Ma, and an increase in spreading rates in the southern Atlantic ocean, and ii) a change in the vector of the subducting plate, which changed from ESE to E at 25 Ma in response to fragmentation of the Farallon Plate. Previous suggestions that Eocene reactivation of the buttressing margin were driven by collision of the Macuchi Arc are shown to be incorrect. 40Ar/39Ar, zircon fission track, and apatite fission track and (U-Th)/He analyses from the Eastern Cordillera north of S1°30' reveal well defined periods of rapid cooling and exhumation at 15 Ma, 9-7 Ma and 5.5-0 Ma. Apatite (U-Th)/He data reveals late Miocene-Recent cooling and exhumation (≤1.3 km) of the southern Eastern Cordillera by a lower quantity than that experienced to the north (≥3.5 km). These distinguishable differences in cooling and exhumation are attributed to the collision of the Carnegie Ridge with the northern SOAM Plate at 15 Ma, and the subsequent subduction of high topography along the ridge at ∼5 Ma, which reactivated the serpentinised Campanian suture via dextral transcurrent displacement. © 2010. Source

Su X.,Jiangsu Polytechnic University | Su X.,Xiangtan University | Yang S.,Xiangtan University | Wang J.,Xiangtan University | And 4 more authors.
Journal of Phase Equilibria and Diffusion

An equation to predict the temperature dependence of solute impurity diffusivity in liquid metals has been derived by combining the Sutherland-Einstein formula with Kaptay's unified equation on the dynamic viscosity of liquid metals. It has been demonstrated that consideration of the temperature dependence of the atomic radius of the diffusing species results in better agreement of the predicted diffusivities with the experimental data compared to when the temperature independent Goldschmidt atomic radius is used. Due to the simple-parameter nature of the equation, it could be very useful in predicting the solute impurity diffusivity in liquid metal when experimental data are scarce. © 2010 ASM International. Source

Dong S.,Xiamen University | Zhao B.,Xiamen University | Lin C.,Xiamen University | Lin C.,Luoyang Ship Material Research Institute | And 3 more authors.
Construction and Building Materials

The corrosion behavior of epoxy/zinc duplex coated rebar embedded in concrete is evaluated comparing with the black steel, galvanized and epoxy coated rebars for a long term in ocean environment. The effect of mechanical damages of epoxy coatings on the corrosion protection is examined. The epoxy coated and epoxy/zinc duplex coated rebars show the higher anti-corrosion performance than other types of rebars. However, once the epoxy coating is mechanically damaged, the more serious corrosion may occur in the damaged area of epoxy coated rebar in concrete. The epoxy/zinc duplex coating remains a good corrosion protection to steel in concrete even when suffering from some mechanical damages. © 2011 Elsevier Ltd. All rights reserved. Source

Welsby S.D.D.,Teck Cominco Ltd.
Materials Science and Technology Conference and Exhibition 2013, MS and T 2013

To consider seawater as a viable option during the early stages of a mineral processing project, a reliable laboratory flotation test procedure is required. This paper documents the development of such a procedure. Flotation with seawater was compared directly to flotation with fresh water. Flotation with seawater had higher variability in selectivity, caused by variable pyrite recovery. Mitigation techniques were unable to alleviate test variability; switching to an inert grinding environment completely eliminated test variability. There was a direct relationship between the recovery of pyrite and the redox potential of the mill discharge when grinding in a mild steel mill with seawater. These results showed that the source of variability with seawater was galvanic interactions between the mild steel mill and the ore, particularly those leading to oxidation of pyrite. Future test work will focus on controlling the extent of these galvanic interactions to improve the reliability of the procedure. Copyright © 2013 MS&T'13®. Source

Electrochemical cells having a cathode, a zinc anode including a mixture of zinc fibers and zinc powder, and electrolyte are provided. The zinc fiber and zinc powder may have selected physical and compositional attributes. Methods of preparing such electrochemical cells are also provided. Such electrochemical cells may provide improved discharging performance under power-demanding conditions.

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