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Philip?SchütteEmail author Massimo?Chiaradia Fernando?Barra Diego?Villagómez Bernardo?Beate 《Mineralium Deposita》2012,47(4):383-410
Mineralization and alteration events at ten Miocene porphyry Cu and porphyry-related epithermal mineral deposits in southern,
central, and northern Ecuador were dated by means of molybdenite Re-Os, biotite and alunite 40Ar/39Ar, and titanite U-Pb geochronology. Most of these hydrothermal events show a spatio-temporal correlation with porphyry intrusion
emplacement as constrained by zircon U-Pb ages. The total age range for these events spans the 23.5–6.1 Ma period, without
displaying systematic along- or across-arc age distribution trends. While epithermal deposits tend to be spatially associated
with volcanic rocks of a similar age, porphyry Cu deposits in Ecuador are frequently spatially associated with deeper-seated
basement units and batholith-scale precursor intrusive systems assembled over ≥5 m.y. time periods. In most cases, formation
of the porphyry Cu deposits is related to the youngest magmatic (-hydrothermal) event in a given area, postdating batholith
construction at a regional scale. The majority of Miocene deposits occurs in southern Ecuador where areally extensive, post-mineralization
(late Miocene to recent) volcanic sequences with the potential to conceal mineralization at depth are lacking. Only few Miocene
deposits occur in northern-central Ecuador, where they mainly crop out in the Western Cordillera, west of the productive present-day
volcanic arc. The surface distribution of post-mineralization arc volcanism reflects along-arc variations in subducting slab
geometry. Porphyry Cu and epithermal deposits in Ecuador define a Miocene metallogenic belt broadly continuous with its coeval
counterpart in northern-central Peru. Although both belt segments were formed in an overall similar tectonomagmatic and metallogenic
setting, their respective metal endowments differ significantly. 相似文献
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Joachim W. Stock Christopher S. Boxe Ralph Lehmann J. Lee Grenfell A. Beate C. Patzer Heike Rauer Yuk L. Yung 《Icarus》2012,219(1):13-24
The chemical composition of a planetary atmosphere plays an important role for atmospheric structure, stability, and evolution. Potentially complex interactions between chemical species do not often allow for an easy understanding of the underlying chemical mechanisms governing the atmospheric composition. In particular, trace species can affect the abundance of major species by acting in catalytic cycles. On Mars, such cycles even control the abundance of its main atmospheric constituent CO2. The identification of catalytic cycles (or more generally chemical pathways) by hand is quite demanding. Hence, the application of computer algorithms is beneficial in order to analyze complex chemical reaction networks. Here, we have performed the first automated quantified chemical pathways analysis of the Martian atmosphere with respect to CO2-production in a given reaction system. For this, we applied the Pathway Analysis Program (PAP) to output data from the Caltech/JPL photochemical Mars model. All dominant chemical pathways directly related to the global CO2-production have been quantified as a function of height up to 86 km. We quantitatively show that CO2-production is dominated by chemical pathways involving HOx and Ox. In addition, we find that NOx in combination with HOx and Ox exhibits a non-negligible contribution to CO2-production, especially in Mars’ lower atmosphere. This study reveals that only a small number of chemical pathways contribute significantly to the atmospheric abundance of CO2 on Mars; their contributions to CO2-production vary considerably with altitude. This analysis also endorses the importance of transport processes in governing CO2-stability in the Martian atmosphere. Lastly, we identify a previously unknown chemical pathway involving HOx, Ox, and HO2-photodissociation, contributing 8% towards global CO2-production by chemical pathways using recommended up-to-date values for reaction rate coefficients. 相似文献
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Land use scenario development and stakeholder involvement as tools for watershed management within the Havel River Basin 总被引：5，自引：0，他引：5
The implementation of the European Water Framework Directive (WFD) will address land use issues in river catchments in order to reduce diffuse pollution and work towards the aim of achieving good ecological status, or good ecological potential in surface water bodies. The WFD also requires the active involvement of all interested parties in developing the best approach to achieve its objectives. The paper demonstrates how scenario analysis can be applied to investigate the impacts of land use changes and how stakeholder interviews can be used to evaluate the results of the scenarios.The study was carried out in the Havel Basin in the northeast of Germany. ‘Landscape-ecological spatial units’ were derived from similar characteristics of soil and groundwater conditions, ground relief and inundation to enable spatial allocation of potential land use and link different scales when describing possible changes in land use. As a first step, in three sub-catchments of the Havel River (distinguished by different physical characteristics) detailed surveys were carried out to investigate the various interests of the stakeholders. The interviews were used to identify the key problems of each area with respect to water quality and quantity and facilitated stakeholder engagement with the catchment planning issues in the Havel River Basin. The information from the stakeholder interviews was used to determine the initial conditions for the land use scenarios which were developed to demonstrate possible changes to land use for achieving better water quality. The land use scenarios also were required as an input into the hydrological modelling of their effects on water quality and to calculate their socio-economic effects. In a second survey, the results of the scenarios and the hydrological modelling were presented to the stakeholders. The consultation process identified the priorities of the stakeholders which could then be taken into account when developing management options. 相似文献
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The use of adaptive cluster sampling for hydroacoustic surveys 总被引：5，自引：0，他引：5
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ABSTRAKT Feltarbeid har en lang tradisjon i geografiundervisningen, men er fremdeles utfordrende å gjennomføre i skolefaget geografi. Denne artikkelen tar utgangspunkt i et kompetansemål i den nye læreplanen i geografi for videregående skole, utviklet gjennom Fagfornyelsen 2020. I kompetansemålet heter det at elevene skal kunne «gjennomføre eit feltarbeid for å undersøkje og presentere geografiske forhold». Dybdelæring er et viktig begrep i Fagfornyelsen, som blant annet innebærer å utvikle forståelse av begreper og sammenhenger i faget. Dette er ambisiøst for elever som får undervisning i geografi to timer per uke i ett år i videregående skole. I artikkelen undersøkes elementer som kan være viktige å ta hensyn til i undervisning av det overnevnte kompetansemålet. Gjennom drøfting av teori og empiriske eksempler identifiseres elementer som kan fremme dybdelæring: gi et oppdrag om å løse en arealsak og åpne for at elevene kan trekke inn egne etno-geografiske erfaringer, forbered elevene på feltarbeidet gjennom å øve på ferdigheter, gjennomfør feltarbeidet i nærmiljøet, diskuter data i lys av teori og etno-geografiske erfaringer, og reflekter over egne beslutninger i arealsaken. Disse elementene kan til sammen fungere som et rammeverk for lærere og forskere som skal designe feltarbeid i geografiundervisning som fremmer dybdelæring. 相似文献
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Tadasore C. Devaraju Kallada R. Jayaraj Thavaraghatta L. Sudhakara Tuomo T. Alapieti Beate Spiering Risto J. Kaukonen 《Central European Journal of Geosciences》2014,6(4):518-548
The Channagiri Mafic-Ultramafic Complex occupies lowermost section of the Neoarchaean Shimoga supracrustal group in the Western Dharwar Craton. It is a segmented body occupying the interdomal troughs of granitoids. The magnetite deposits occur in the northeastern portion; typically occupying the interface zone between gabbro and anorthositic. Mineralogically, the deposits are simple with abundant magnetite and ilmenite. Hogbomite is a consistent minor mineral. Magnetites are typically vanadiferous (0.7–1.25% V2O5). Ilmenite consistently analyses more MgO and MnO than coexisting magnetite. Chlorite, almost the only silicate present; lies in the range of ripidolite, corundophilite and sheridanite. The chromiferous suit occupying eastern side of Hanumalapur block (HPB) contains Fe-Cr-oxide analysing 37.8–11.9% Cr2O3 and 40.5–80% FeO t . In these too, chlorite, typically chromiferous (0.6–1.2% Cr2O3), is the most dominant silicate mineral. Geochemistry of V-Ti-magnetite is dominated by Fe, Ti and V with Al, Si, Mg and Mn contributing most of the remaining. Cr, Ni, Zn, Co, Cu, Ga and Sc dominate trace element geochemistry. The Cr-magnetite is high in Cr2O3 and PGE. Two separate cycles of mafic magmatism are distinguished in the CMUC. The first phase of first cycle, viz., melagabbro-gabbro, emplaced in the southeastern portion, is devoid of magnetite deposits. The second phase, an evolved ferrogabbroic magma emplaced in differentiated pulses, occupying northeastern portion of the complex, consists of melagabbro→gabbro-anorthosite→V-Ti magnetite→ferrogabbro sequence. Increase in oxygen fugacity facilitated deposition of V-Ti magnetite from ferrogabbroic magma pulse emplaced in late stages. The second cycle of chromiferous PGE mineralized suite comprises fine-grained ultramafite→alternation of pyroxinite-picrite→Crmagnetite sequence formed from fractionation of ferropicritic magma. HPB also includes >65m thick sill-like dioritic phase at the base of the ferriferous suit and a sinuous band of coarse-grained ultramafite enclosed within the chromiferous suit; both unrelated to the two mafic magmatic cycles. 相似文献