Ranking of Placer Gold Prospects in Chile Through Analytic Hierarchy Process     

Jara  J. Joaquín  Moreno  Francisco  Jara  Raúl  Dubournais  Francisco  Mata  Rodrigo  Peters  David  Marquardt  Carlos  Lagos  Gustavo 《Natural Resources Research》2019,28(3):813-832

Chile has a rich, but poorly known history of placer gold mining. At present, this sector is almost nonexistent and there are some restrictions for its revival: disperse and partial information on existing resources and limited technical expertise to assess the potential of placer gold mine sites. This paper presents the background, methodology and results of the prioritization process of known prospects of this kind in Chile. This research was part of a publicly funded project aimed to incentivize the development of this industry. The ranking was carried out using the analytic hierarchy process, which allowed to include different quantitative and qualitative variables related to the economic potential, technical aspects, contextual viability and socioeconomic factors in the analysis. The results show that, despite the increasing relevance of environmental and community issues in mining development, the business potential and the economic/technical aspects are the main factors in the early selection of a site to advance in exploration and development activities. Both variables represented around 40% and 37% of weights in the final selection, respectively. In contrast, contextual viability and local socioeconomic impacts only accounted for the remaining 23%. This study also shows that the inclusion of experts with different backgrounds in the process enriches the analysis and does not significantly distort the final outcome of the prioritization. Finally, the relevance of using MCDM tools when assessing the attractiveness of mine sites for their development is highlighted, particularly when public funds for subsequent exploration activities are committed.

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Late Quaternary vegetation and climate dynamics in central-eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome     

Ingrid Horák-Terra  Antonio Martínez Cortizas  Cynthia Fernandes Pinto Da Luz  Alexandre Christófaro Silva  Tim Mighall  Plínio Barbosa De Camargo  Carlos Victor Mendonça-Filho  Paulo Eduardo De Oliveira  Francisco Willian Cruz  Pablo Vidal-Torrado 《第四纪科学杂志》2020,35(5):664-676

The late Quaternary evolution of central-eastern Brazil has been under-researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi-deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi-proxy approach: stable isotopes (δ¹³C, δ¹⁵N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid-Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp ) and over (~16.5 to ~6.1 k cal a bp ) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp .  相似文献   

New age constraints on the western Betic intramontane basins: A late Tortonian closure of the Guadalhorce Corridor?          下载免费PDF全文

Marlies van der Schee  Bas C. J. van den Berg  Walter Capella  Dirk Simon  Francisco J. Sierro  Wout Krijgsman 《地学学报》2018,30(5):325-332

Several gateways connected the Mediterranean with the Atlantic during the late Miocene but the timing of closure and therefore their role prior to and during the Messinian Salinity Crisis (5.97–5.33 Ma) is still under debate. The timing of closure of the Guadalhorce Corridor is especially disputed as the common lack of marine microfossils hampers precise age determination. Here we present new biostratigraphic age constraints on the sediments of the Ronda, Antequera and Arcos regions, which formed the northern part of the Guadalhorce Corridor. The general presence of Globorotalia menardii 4 in the youngest deep‐marine sediments of all three regions indicates a late Tortonian age, older than 7.51 Ma. We conclude that the Guadalhorce Corridor closed during the late Tortonian, well before the onset of the Messinian Salinity Crisis and that the late Tortonian tectonic uplift of the eastern Betics extended into the western Betics.  相似文献   

Bismuth‐melt trails trapped in cassiterite–quartz veins     

Frederico Sousa Guimares  Alexandre Raphael Cabral  Bernd Lehmann  Francisco Javier Rios  Moiss Augusto Bacellar vila  Marco Paulo de Castro  Glucia Nascimento Queiroga 《地学学报》2019,31(4):358-365

Native bismuth in the form of metallic melt has been considered instrumental to the formation of some metallic ore deposits via a mechanism dubbed the “Liquid Bismuth Collector Model.” Here, we provide petrographical documentation of trail‐forming, μm‐sized blebs of native bismuth in cassiterite–quartz veins from the Santa Bárbara greisen Sn deposit in the Rondônia tin province of northern Brazil. These inclusions suggest the trapping of a Bi melt that took place during vein formation, in a mechanism similar to the entrapment of fluid inclusions.  相似文献   

Characterization of complex groundwater flows in the environment of singular buildings by combining hydrogeological and non-destructive geophysical (ground-penetrating radar) techniques: Punta Begoña Galleries (Getxo,Spain)     

Jesus A. Uriarte  Laura Damas Mollá  Maialen Sagarna  Arantza Aranburu  Francisco García  Iñaki Antigüedad  Tomás Morales 《水文研究》2020,34(4):1004-1015

Locating and quantifying groundwater flow in many built-up areas are a priority with regard to its complete restoration. In this work, a hydrogeological survey of the surroundings of the Punta Begoña Galleries (Getxo, Bizkaia), built on a coastal cliff, was completed by using ground penetrating radar (GPR) testing. Thus, the preliminary characterization of soils and rocks in accessible areas of the cliff was first improved by hydrogeological information gathered from a single survey borehole, including permeability measurements by low pressure injection tests (LPTs) and continuous water level monitoring. As a complementary method, the non-destructive GPR technique was performed during both dry and wet hydrological periods and in tandem with the injection tests, providing more complete spatial and temporal images of water flows. Specifically, GPR allows mapping of flow paths in soils and assessing the continuity of fractures in rock masses. Altogether, this complementary approach provides greater knowledge of complex underground flow dynamics in built environments, thus making it easier to make decisions for their management.  相似文献   

Temporal and spatial variation of soil erosion in wooded rangelands of southwest Spain     

Judit Rubio-Delgado  Susanne Schnabel  Álvaro Gómez-Gutiérrez  Joaquín Francisco Lavado-Contador 《地球表面变化过程与地形》2019,44(11):2141-2155

Changes in land use are common in Mediterranean areas and are reported as having produced changes in the intensity of soil erosion. Dehesas are rangelands with a disperse tree cover, widespread in the south-western part of the Iberian Peninsula and similar ecosystems are also common in other areas with a Mediterranean climate. The aim of the present study is to analyse temporal and spatial variations of soil erosion rates estimated along three hillsides, located in two farms (Buitrera and Parapuños) in southwest Spain. To understand the temporal variation, soil erosion rates were studied in light of land use-management changes that took place during the last few centuries. Results indicate very low erosion rates prior to the 18^th century in both farms. In Buitrera, a first increase of soil loss rates was identified during the period 1831-1897, amounting to 7.4 t ha^-1 y^-1. A further increase took place during the 20^th century, reaching a mean erosion rate of 29.1 t ha^-1 y^-1. In Parapuños, data points to a significant increase from 1881 onwards, with an estimated mean erosion rate of 18.5 t ha^-1 y^-1. Those increases were presumably connected with an intensification of land use, such as cultivation and excessive livestock populations. Regarding spatial variation, the bare surface and the erosive power of run-off along the hillsides accounts for 76% of the soil erosion rates dispersion. At a local scale, the variability of erosion rates could not be explained, because of (i) uncertainty related to the micromorphology of the past soil surface and (ii) the role of tillage erosion in the past. However, the results obtained offer valuable data on the temporal and spatial variation of erosion rates in dehesas at the hillslope scale and a similar approach could be used for other rangelands with a disperse tree cover. © 2019 John Wiley & Sons, Ltd.  相似文献   

A method to estimate maximum and minimum air temperature using MODIS surface temperature and vegetation data: application to the Maipo Basin,Chile     

Eduardo Bustos  Francisco J. Meza 《Theoretical and Applied Climatology》2015,120(1-2):211-226

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Reconciling Discrepancies Between Airborne and Buoy-Based Measurements of Wind Stress Over Mixed Seas     

Héctor García-Nava  Francisco J. Ocampo-Torres  Paul A. Hwang 《Boundary-Layer Meteorology》2015,155(3):515-526

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Erratum to: Central European Journal of Geosciences, volume 3, number 2     

János Kovács  Szabolcs Á. Fábián  Gábor Varga  Karoly Németh  Corina Risso  Francisco Nullo  Gabor Kereszturi  Titusz Bugya  Szabolcs Á. Fábián  Noémi L. Görcs  István P. Kovács  Bertalan Radvánszky  Gabriella Barta  Rudolf Musil  Alice Ghiselli  Marzio Merazzi  Andrea Strini  Roberto Margutti  Michele Mercuriali  Rauf Gardashov  Daria Gushchina  Boris Dewitte  Martin Michálek  Marián Putiš  Christoph A. Hauzenberger  Jindřich Šancer  Martin Štrejbar  Aneta Maleňáková  George Migiros  George D. Bathrellos  Hariklia D. Skilodimou  Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):229-229

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On the use of IPCC-class models to assess the impact of climate on Living Marine Resources     

Charles A. Stock  Michael A. Alexander  Nicholas A. Bond  Keith M. Brander  William W.L. Cheung  Enrique N. Curchitser  Thomas L. Delworth  John P. Dunne  Stephen M. Griffies  Melissa A. Haltuch  Jonathan A. Hare  Anne B. Hollowed  Patrick Lehodey  Simon A. Levin  Jason S. Link  Kenneth A. Rose  Ryan R. Rykaczewski  Jorge L. Sarmiento  Ronald J. Stouffer  Franklin B. Schwing  Francisco E. Werner 《Progress in Oceanography》2011,88(1-4):1-27

The study of climate impacts on Living Marine Resources (LMRs) has increased rapidly in recent years with the availability of climate model simulations contributed to the assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Collaboration between climate and LMR scientists and shared understanding of critical challenges for such applications are essential for developing robust projections of climate impacts on LMRs. This paper assesses present approaches for generating projections of climate impacts on LMRs using IPCC-class climate models, recommends practices that should be followed for these applications, and identifies priority developments that could improve current projections. Understanding of the climate system and its representation within climate models has progressed to a point where many climate model outputs can now be used effectively to make LMR projections. However, uncertainty in climate model projections (particularly biases and inter-model spread at regional to local scales), coarse climate model resolution, and the uncertainty and potential complexity of the mechanisms underlying the response of LMRs to climate limit the robustness and precision of LMR projections. A variety of techniques including the analysis of multi-model ensembles, bias corrections, and statistical and dynamical downscaling can ameliorate some limitations, though the assumptions underlying these approaches and the sensitivity of results to their application must be assessed for each application. Developments in LMR science that could improve current projections of climate impacts on LMRs include improved understanding of the multi-scale mechanisms that link climate and LMRs and better representations of these mechanisms within more holistic LMR models. These developments require a strong baseline of field and laboratory observations including long time series and measurements over the broad range of spatial and temporal scales over which LMRs and climate interact. Priority developments for IPCC-class climate models include improved model accuracy (particularly at regional and local scales), inter-annual to decadal-scale predictions, and the continued development of earth system models capable of simulating the evolution of both the physical climate system and biosphere. Efforts to address these issues should occur in parallel and be informed by the continued application of existing climate and LMR models.  相似文献