Application of geostatistical methods in gold geochemical anomalies identification (Montemor-O-Novo, Portugal)   总被引：1，自引：0，他引：1  

A. P. Reis  A. J. Sousa  E. Cardoso Fonseca 《Journal of Geochemical Exploration》2003,77(1):45-63

The study described herein concerns the application of geostatistical methods to data soil from Montemor-O-Novo area (Southern Portugal). In the area, the gold mineralised zones (Banhos, Caeiras, Falés, Gamela, Malaca and Monfurado) are characterised by different geological settings and mineralogical assemblages. A total of 1211 soil samples were collected in Montemor-O-Novo area and analysed for Cu, Pb, Zn, As, Ba and Au by atomic absorption spectrometry.To account for spatial structure, simple and cross variograms were computed for the main directions of the grid sampling. From the experimental variograms a linear model of coregionalization composed of three structures, a nugget effect and two anisotropic spherical structures, was fitted to each of the six variables. The coregionalization matrices deduced from the theoretical model show the relationships between the variables at different scales. These matrices were compared with those obtained by principal component analysis (PCA).This methodology was the basis for estimating the corresponding spatial components (Y0, Y1 and Y2) using factorial kriging analysis (FKA). Maps of raw data, Y0, Y1 and Y2 were made for each variable.The use of multivariate analysis permit the study of the spatial structure intrinsic to geochemical data and the identification and refinement of significant anomalies related to Au-bearing mineral deposits.  相似文献   

Reply to Discussion on "Giant versus small porphyry copper deposits of Cenozoic age in northern Chile: adakitic versus normal calc-alkaline magmatism" by Oyarzun R,Márquez A,Lillo J,López I,Rivera S (Mineralium Deposita 36:794–798, 2001)     

Roberto Oyarzun  Alvaro Márquez  Javier Lillo  Ivan López  Sergio Rivera 《Mineralium Deposita》2002,37(8):795-799

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Editors' Introduction     

Carlos Nunes Silva  Max Barlow 《GeoJournal》2002,58(1):1-2

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Visual discrimination of surface features of salt affected soils using satellite images in arid region of Rajasthan (India)     

D C Joshi  Tibor Tóth  Diana Sári 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):33-38

The study has been carried for visual discrimination of natural salt affected soils on FCC images of IRS 1 B in Pali district of Rajasthan. The salt affected soils show wide variations in salinity (EC_2.53.7 to 28 dSm^-1), alkalinity (pH 8.5-9.8), cover ofP. juliflora (10-90%), salt tolerant grasses (10–55%) and gravelly surface (20–35%). ThoughP. juliflora and grasses were present at most of the observation points their cover decreased with soil EC_2.5 values more than 10 and 13 dSm^-1, respectively. Five darkness categories derived as the result of visual interpretation of FCCs; and ground and laboratory studies revealed that the darkness category 1 represented fewer plant community with high salinity (EC 28.7 dSm^-1) and gravelly surface, categories 2 and 3 were characterised by grass cover and moderate salt affected soils (EC 3-10 dSm^-1) whereas category 4 was dominated by thicket ofP. juliflora. The derived numerical darkness categories of the FCC images were slightly low for February images. The darkness values of observation pixel on February images correlated positively withP. juliflora cover and negatively with grass cover and soil pH indicating that surface features on FCC were related with the immediate observation pixels.  相似文献   

Structure of the Padul-Nigüelas Basin (S Spain) from H/V Ratios of Ambient Noise: Application of the Method to Study Peat and Coarse Sediments     

J. Delgado  P. Alfaro  J. Galindo-Zaldivar  A. Jabaloy  A. C. López Garrido  C. Sanz de Galdeano 《Pure and Applied Geophysics》2002,159(11-12):2733-2749

—?This paper presents the results of the application of a technique of geophysical surveying based on resonance frequency of materials, in a small basin within the Internal Zones of the Betic Cordillera (southern Spain). The frequencies determined have enabled the main features of the basin's structure to be delineated, clearly identifying its asymmetry due to variations in the position of the rigid basement in different sectors. The results show that this method does not guarantee a perfect identification of coarse sediments, unless these overlie substantial more rigid materials. On the other hand, the same method was very effective for studying very soft sediments (peat), and it was possible to establish a quantitative relationship for determining the thickness of these sediments based on their resonance frequency. This relationship was then used to map peat thickness in the basin. The results have been compared with gravity studies and mechanical drillings undertaken in the region.  相似文献   

A ‘core-complex-like structure’ formed by superimposed extension,folding and high-angle normal faulting. The Santi Petri dome (western Betics,Spain)     

Guillermo Booth-Rea  José Miguel Azañón  Vı́ctor Garcı́a-Dueñas  Romain Augier  Mario Sánchez-Gómez 《Comptes Rendus Geoscience》2003,335(2):265-274

The Santi Petri dome (western Betics, southern Spain) shows a core-complex-like structure, where migmatitic gneisses and schists outcrop below low-grade slates and phyllites, all of which form the basement of the Neogene Málaga basin. The migmatites and schists suffered a coaxial-flattening event during isothermal decompression and were later exhumed by ductile ESE non-coaxial stretching. Further exhumation was achieved by W- to SW-transport brittle low-angle normal faulting. Subsequently these extensional structures were gently folded in the core of a NE/SW-oriented antiform during the Tortonian. Finally the Santi Petri domal geometry was accentuated by the interference of orthogonal high-angle faults with ENE–WSW and NNW–SSE orientation. This core-complex-like structure, formed by superposition of extensional and compressive tectonic events, does not represent a classical, purely extensional core complex, which shows that metamorphic structure and geometry are not decisive criteria to define a core-complex.  相似文献   

Governing Metropolitan Lisbon: A tale of fragmented urban governance     

Carlos Nunes Silva 《GeoJournal》2002,58(1):23-32

This article is concerned with the nature of the present governance framework in the Lisbon metropolitan area and with the conditions responsible for the lack of any consistent intergovernmental and inter-tier co-ordination. It shows how Lisbon, where a form of metropolitan government was introduced only in 1991, is different from other European cities, but at the same time similar with regard to the limits associated with the associative or (polycentric) model adopted. The article concludes by discussing alternative scenarios for the reform of metropolitan government as well as the institutional and policy challenges facing the Lisbon metropolitan area. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

A record of late Holocene precipitation on the Central Tibetan Plateau inferred from varved lake sediments     

Ji  Kejia  Zhu  Erlei  Chu  Guoqiang  Aquino-López  Marco A.  Hou  Juzhi 《Journal of Paleolimnology》2021,66(4):439-452

Journal of Paleolimnology - Lake sediments on the Tibetan Plateau are important natural archives for studying past climate and environment changes. A precise sediment core chronology is a...  相似文献   

Plant macrofossil assemblages from surface sediment represent contemporary species and growth forms of aquatic vegetation in a shallow Mediterranean lake     

Jorge García-Girón  Camino Fernández-Aláez  Alejandro Nistal-García  Margarita Fernández-Aláez 《Journal of Paleolimnology》2018,60(4):495-509

Macrofossils are known as a useful tool in reconstructing their original plant communities. However, most studies have been focused on comparing the composition and distribution of living plant communities and their remains in temperate lakes. Mediterranean shallow lakes have been historically far less studied and little is known about the relationships between Mediterranean macrophyte communities and their remains. The aim of our study is to assess how contemporary aquatic macrophyte communities are represented by their sedimentary remains in terms of composition, distribution and concordance between the contemporary and the subfossil assemblages in a procrustean superimposition space, and to determine which surface sediment cores, collected along a depth gradient, may represent best the whole-lake macrofossil assemblage. These analyses were carried out for both species and macrophyte growth forms (submerged hydrophytes, floating-leaved hydrophytes, helophytes and charophytes) in order to check which of the two (species and growth forms) were represented best by their macro-remains. The most abundant present-day species (Myriophyllum alterniflorum DC. and Potamogeton trichoides L.) were under-represented while Characeae and some floating-leaved hydrophytes (Polygonum amphibium L. and Ranunculus peltatus Schrank) were over-represented in sedimentary samples. Additionally, macro-remains of submerged hydrophytes and helophytes were generally found in the central areas and in close proximity to contemporary vegetation, whereas floating-leaved hydrophytes distributed close to the near-shore. Notwithstanding some disparities between contemporary vegetation and their macrofossil assemblages, we found a good agreement between present-day and sedimentary datasets for both species and macrophyte growth forms. Furthermore, our study suggests that sediment cores from deep areas are more likely to represent best the whole-lake macrofossil assemblage because of their high diversity, equitability and heterogeneity. We conclude that aquatic macrophyte subfossils from the central areas of the basin can be a very useful tool in tracking the species composition and structure of the original macrophyte communities in shallow Mediterranean lakes. Additionally, when considering the use of macro-remains to reconstruct the composition and structure of macrophyte growth forms, we recommend a multicore approach that uses transects running from the shore to the lake center.  相似文献   

IAG Newsletter     

Gyula Tóth 《Journal of Geodesy》2009,83(2):189-190

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