Intermittent generation of mafic enclaves in the 1991–1995 dacite of Unzen Volcano recorded in mineral chemistry     

Hiroaki?SatoEmail author  Francois?Holtz  Roman?E.?Botcharnikov  Setsuya?Nakada 《Contributions to Mineralogy and Petrology》2017,172(4):22

Mafic enclaves in the 1991–1995 dacite of Unzen volcano show chemical and textural variability, such as bulk SiO₂ contents ranging from 52 to 62 wt% and fine- to coarse-grained microlite textures. In this paper, we investigated the mineral chemistry of plagioclase and hornblende microlites and distinguished three enclave types. Type-I mafic enclaves contain high-Mg plagioclase and low-Cl hornblende as microlites, whereas type-III enclaves include low-Mg plagioclase and high-Cl hornblende. Type-II enclaves have an intermediate mineral chemistry. Type-I mafic enclaves tend to show a finer-grained matrix, have slightly higher bulk rock SiO₂ contents (56–60 wt%) when compared with the type-III mafic enclaves (SiO₂?=?53–59 wt%), but the overall bulk enclave compositions are within the trend of the basalt–dacite eruptive products of Quaternary monogenetic volcanoes around Unzen volcano. The origin of the variation of mineral chemistry in mafic enclaves is interpreted to reflect different degree of diffusion-controlled re-equilibration of minerals in a low-temperature mushy dacitic magma reservoir. Mafic enclaves with a long residence time in the dacitic magma reservoir, whose constituent minerals were annealed at low-temperature to be in equililbrium with the rhyolitic melt, represent type-III enclaves. In contrast, type-I mafic enclaves result from recent mafic injections with a mineral assemblage that still retains the high-temperature mineral chemistry. Taking temperature, Ca/(Ca?+?Na) ratio of plagioclase, and water activity of the hydrous Unzen magma into account, the Mg contents of plagioclase indicate that plagioclase microlites in type-III enclaves initially crystallized at high temperature and were subsequently re-equilibrated at low-temperature conditions. Compositional profiles of Mg in plagioclase suggest that older mafic enclaves (Type-III) had a residence time of ~100 years at 800 °C in a stagnant magma reservoir before their incorporation into the mixed dacite of the 1991–1995 Unzen eruption. Presence of different types of mafic enclaves suggests that the 1991–1995 dacite of Unzen volcano tapped mushy magma reservoir intermittently replenished by high-temperature mafic magmas.  相似文献   

Numerical simulation of the 30–45 ka debris avalanche flow of Montagne Pelée volcano,Martinique: from volcano flank collapse to submarine emplacement     

Brunet  Morgane  Moretti  Laurent  Le Friant  Anne  Mangeney  Anne  Fernández Nieto  Enrique Domingo  Bouchut  Francois 《Natural Hazards》2017,85(2):1189-1208

Natural Hazards - In November 2015, China government announced that the national carbon emissions trading market is expected to start in 2017. Carbon emission trading system is a raising concern...  相似文献   

Twentieth century precipitation trends in the upper Mzingwane sub-catchment of the northern Limpopo basin,Zimbabwe     

Maviza  Auther  Grab  Stefan  Engelbrecht  Francois 《Theoretical and Applied Climatology》2022,149(1-2):309-325

Theoretical and Applied Climatology - This study evaluates precipitation trends in the upper Mzingwane sub-catchment (UMS) of Zimbabwe using ten World Meteorological Organization (WMO)’s...  相似文献   

The effect of titanium and phosphorus on ferric/ferrous ratio in silicate melts: an experimental study     

Alexander Borisov  Harald Behrens  Francois Holtz 《Contributions to Mineralogy and Petrology》2013,166(6):1577-1591

The effect of TiO₂ and P₂O₅ on the ferric/ferrous ratio in silicate melts was investigated in model silicate melts at air conditions in the temperature range 1,400–1,550 °C at 1-atm total pressure. The base composition of the anorthite–diopside eutectic composition was modified with 10 wt % Fe₂O₃ and variable amounts of TiO₂ (up to 30 wt %) or P₂O₅ (up to 20 wt %). Some compositions also contained higher SiO₂ concentrations to compare the role of SiO₂, TiO₂, and P₂O₅ on the Fe³⁺/Fe²⁺ ratio. The ferric/ferrous ratio in experimental glasses was analyzed using a wet chemical technique with colorimetric detection of ferrous iron. It is shown that at constant temperature, an increase in SiO₂, TiO₂, and P₂O₅ content results in a decrease in the ferric/ferrous ratio. The effects of TiO₂ and SiO₂ on the Fe³⁺/Fe²⁺ ratio was found to be almost identical. In contrast, adding P₂O₅ was found to decrease ferric/ferrous ratio much more effectively than adding silica. The results were compared with the predictions from the published empirical equations forecasting Fe³⁺/Fe²⁺ ratio. It was demonstrated that the effects of TiO₂ are minor but that the effects of P₂O₅ should be included in models to better describe ferric/ferrous ratio in phosphorus-bearing silicate melts. Based on our observations, the determination of the prevailing fO₂ in magmas from the Fe³⁺/Fe²⁺ ratio in natural glasses using empirical equations published so far is discussed critically.  相似文献   

A Compilation of Silicon,Rare Earth Element and Twenty‐One other Trace Element Concentrations in the Natural River Water Reference Material SLRS‐5 (NRC‐CNRC)     

Delphine Yeghicheyan  Cécile Bossy  Martine Bouhnik Le Coz  Chantal Douchet  Guy Granier  Alexie Heimburger  Francois Lacan  Aurélie Lanzanova  Tristan C. C. Rousseau  Jean‐Luc Seidel  Mickaël Tharaud  Frédéric Candaudap  Jérôme Chmeleff  Christophe Cloquet  Sophie Delpoux  Marie Labatut  Rémi Losno  Catherine Pradoux  Yann Sivry  Jeroen E. Sonke 《Geostandards and Geoanalytical Research》2013,37(4):449-467

The natural river water certified reference material SLRS‐5 (NRC‐CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP‐MS. Because no certified values are assigned by NRC‐CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given.  相似文献   

The Ultimate CCD for Laser Guide Star Wavefront Sensing on Extremely Large Telescopes     

James W. Beletic  Sean Adkins  Barry Burke  Robert Reich  Bernie Kosicki  Vyshnavi Suntharalingham  Charlie Bleau  Ray DuVarney  Richard Stover  Jerry Nelson  Francois Rigaut 《Experimental Astronomy》2005,19(1-3):103-109

All of the extremely large telescopes (ELTs) will utilize sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these telescopes plan to use the Shack-Hartmann approach for wavefront sensing. In these AO systems, the laser spots in subapertures at the edge of the pupil will suffer from spot elongation due to the 10 km extent of the sodium layer and the large separation from the projection laser. This spot elongation will severely degrade the performance of standard geometry wavefront sensing systems. In this paper, we present a CCD with custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This CCD design will give better performance than a standard geometry CCDs for continuous wave lasers. In addition, this CCD design is optimal for a pulsed sodium laser. The pixel geometry enables each subaperture to follow a laser pulse traversing the sodium layer, providing optimal sampling of a limited number of detected photons. In addition to novel pixel layout, this CCD will also incorporate experimental JFET sense amplifiers and use CMOS design approaches to simplify the routing of biases, clocks and video output. This CCD will attain photon-noise limited performance at high frame rates, and is being incorporated in the plans for the Thirty Meter Telescope (TMT).  相似文献   

Towards bridging the gap between climate change projections and maize producers in South Africa     

Landman  Willem A.  Engelbrecht  Francois  Hewitson  Bruce  Malherbe  Johan  van der Merwe  Jacobus 《Theoretical and Applied Climatology》2018,132(3-4):1153-1163

Theoretical and Applied Climatology - Multi-decadal regional projections of future climate change are introduced into a linear statistical model in order to produce an ensemble of austral...  相似文献   

High‐resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics          下载免费PDF全文

Estelle Leroux  Marina Rabineau  Daniel Aslanian  Christian Gorini  Stéphane Molliex  Francois Bache  Cécile Robin  Laurence Droz  Maryline Moulin  Jeffrey Poort  Jean‐Loup Rubino  Jean‐Pierre Suc 《Basin Research》2017,29(3):305-339

Basin‐wide correlation of Messinian units and Plio‐Quaternary chronostratigraphic markers (5.3 Ma, 2.6 Ma, 0.9 Ma and 0.45 Ma), the mapping of total sediment thickness and the determination of overall sedimentary volumes enabled us to provide a high‐resolution quantitative history of sediment volumes for the last 6 Ma along the Gulf of Lions margin. The results point to (i) a dramatic increase in terrigenous sediment input during the Messinian Salinity Crisis. This increased sedimentation reflects enhanced regional fluvial erosion related to the dramatic fall of Mediterranean base‐level. Stronger weathering due to a regional wetter climate probably also increased erosional fluxes. (ii) A sediment input three times higher during the Plio‐Quaternary compared to the Miocene seems in agreement with published measurements from World's ocean. However, the timing of this increase being uncertain, it implies that the trigger(s) also remain(s) uncertain. (iii) A decrease in detrital volume around 2.6 Ma is attributed to a regional change in the drainage pattern of rivers in the northwestern Alps. (iv) This study also highlights the Mid‐Pleistocene Revolution around 0.9 Ma, which resulted in an almost doubling of sediment input in the Provencal Basin.  相似文献   

The UV cameras on the High Energy Transient Experiment (HETE)     

Roland Vanderspek  Alia Atlas  Tye M. Brady  Geoffrey B. Crew  John P. Doty  Steven E. Kissel  George R. Ricker  Peter C. Tappan  Francois Martel  M. Tim Jones 《Astrophysics and Space Science》1995,231(1-2):479-482

The High Energy Transient Experiment (HETE), scheduled for launch this year, is a small satellite dedicated to multiwavelength observations of -ray and X-ray bursts. The HETE spacecraft will be equipped with gamma-ray detectors, X-ray detectors with a coded mask, and ultraviolet-sensitive CCD cameras. The UV cameras on HETE are wide-field imagers which will a) provide UV images of the regions in which -ray or X-ray bursts are detected, before, duringand after the burst, b) detect UV transients, whether associated with a high-energy transient or not, c) monitor the brightnesses of field stars for variability over a wide range of timescales, and d) serve as star trackers for HETE. In this poster, we describe the HETE UV instrumentation, control software, and data products.  相似文献   

Contextualizing vulnerability assessment: a support to geo-risk management in central Africa     

Michellier  Caroline  Pigeon  Patrick  Kervyn  Francois  Wolff  Eleonore 《Natural Hazards》2016,81(1):27-43

European Union directives as well as national legislation are placing great emphasis on the inclusion of stakeholder perspectives in the governance of risks from natural hazards. This should help decision makers formulate better policies. However, to date, there is little information on stakeholders’ perspectives with respect to landslide risk governance. This paper addresses the gap by reporting on research in Nocera Inferiore, Italy. The research is based on a documentary analysis, 43 semi-structured interviews and a survey submitted to 373 residents. The political instability, the unfairness of national funding allocation across municipalities and the residents’ lack of knowledge about risk assessment and emergency planning are some of the main barriers to effective risk governance. Moreover, there are divergent, sometimes even opposite, stakeholders’ views on several issues, such as the relevance of illegal development in risky areas. The results highlight the importance of addressing these divergent views and including the plurality of voices as a prerequisite for inclusive risk governance. The research provided essential background information for a participatory process, which was designed to support decisions on landslide risk mitigation measures in Nocera Inferiore (Linnerooth-Bayer et al. this issue). The methodology will be of more general interest to researchers and policymakers intent upon including stakeholder perspectives in natural risk governance.  相似文献