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31.
Assessment of Geochemical Anomaly Uncertainty Through Geostatistical Simulation and Singularity Analysis 总被引:1,自引:0,他引:1
Liu Yue Cheng Qiuming Carranza Emmanuel John M. Zhou Kefa 《Natural Resources Research》2019,28(1):199-212
Natural Resources Research - Geochemical anomalies are commonly separated into different geochemical anomaly levels based on one or more thresholds. However, this practice may cause some important... 相似文献
32.
Ghezelbash Reza Maghsoudi Abbas Carranza Emmanuel John M. 《Natural Resources Research》2019,28(4):1299-1316
Natural Resources Research - Assigning realistic weights to targeting criteria in order to synthesize various geo-spatial datasets is one of the most important challenging tasks for mineral... 相似文献
33.
Emmanuel John M. Carranza 《Resource Geology》2010,60(2):129-149
Wildcat modelling of mineral prospectivity has been proposed for greenfields geologically-permissive terranes where mineral targets have not yet been discovered but a geological map is available as a source of spatial data of predictors of mineral prospectivity. This paper (i) revisits the initial way of assigning wildcat scores (Sc) to predictors of mineral prospectivity and (ii) proposes an improvement by transforming Sc into improved wildcat scores (ISc) by using a logistic function. This was shown in wildcat modelling of prospectivity for low-sulphidation epithermal-Au (LSEG) deposits in Aroroy district (Philippines). Based on knowledge of characteristics of and controls on LSEG mineralization in the Philippines, the spatial predictors of LSEG prospectivity used in the study are proximity to porphyry plutonic stocks, faults/fractures and fault/fracture intersections. The Sc and ISc of spatial predictors are input separately to principal components analysis to extract a favourability function that can be interpreted as a wildcat model of LSEG prospectivity. The predictive capacity of the wildcat model of LSEG prospectivity based on the ISc of geological predictors is roughly 70% higher than that of the wildcat model of LSEG prospectivity based on the Sc of geological predictors. A slight increase of predictive capacity of wildcat modelling of LSEG prospectivity is also achieved when the ISc of geological predictors are integrated with the ISc of geochemical anomalies, but not with the Sc of geochemical anomalies. The proposed improvement is significant because if the study district were a greenfields exploration area, then a wildcat model of LSEG prospectivity based on the old wildcat methodology would have caused several LSEG targets to be missed. 相似文献
34.
Results of H interferometric observations of NGC 7793 are reported. This galaxy contains about 93 HII regions and a general emission background. Its radial velocity is 215 km s–1.The total mass is low, 2–3×109 solar masses, as well as the average density; the meanM/L is 0.4 suggesting a high proportion of young objects. 相似文献
35.
Qualitative and quantitative knowledge about the spatial association between mineral occurrences and geological features are important in mineral potential mapping. Two existing methods for quantifying spatial association between mineral occurrences and curvilinear geological features are applied to the Baguio district of the Philippines. An experimental method is described and applied to the study area as well. The results of the three methods are highly similar, which demonstrates the effectiveness of the experimental method presented here for quantifying spatial association between mineral occurrences and curvilinear geological features. It is shown that gold occurrence in the Baguio district are strongly spatially associated with northeasterly trending faults/fractures rather than with northwesterly trending faults/fractures. It is also shown that the spatial association between the gold occurrence and older batholithic intrusives is stronger than the spatial association between gold occurrence and younger porphyry intrusives. These spatial geoinformation characteristics can be used as evidential data layers in GIS-based mineral potential mapping. 相似文献
36.
Natural Resources Research - 相似文献
37.
The kinematics of the central zones of NGC 55 is discussed on the basis of interferometric observations. The emission regions have radial velocities well differentiated showing also a significant gradient and coinciding in general with those obtained in 21 cm. The exception consisting of an emission complex of high velocity is interpreted as moving towards the centre of the galaxy indicating flux of material along the bar. 相似文献
38.
The kinematics and structure of NGC 1313 are discussed on the basis of interferometric observations. Several uniformly rotating components, a total mass of 2×1010 solar masses, and deviations from pure circular movement of an amplitude of almost 20 km s–1 are found. 相似文献
39.
Geologically Constrained Probabilistic Mapping of Gold Potential, Baguio District, Philippines 总被引:1,自引:0,他引:1
Binary predictor patterns of geological features are integrated based on a probabilistic approach known as weights of evidence modeling to predict gold potential. In weights of evidence modeling, the log
e
of the posterior odds of a mineral occurrence in a unit cell is obtained by adding a weight, W
+ or W
– for presence of absence of a binary predictor pattern, to the log
e
of the prior probability. The weights are calculated as log
e
ratios of conditional probabilities. The contrast, C = W
+ – W
–, provides a measure of the spatial association between the occurrences and the binary predictor patterns. Addition of weights of the input binary predictor patterns results in an integrated map of posterior probabilities representing gold potential. Combining the input binary predictor patterns assumes that they are conditionally independent from one another with respect to occurrences. 相似文献
40.
E. Alonso L. R. Alejano F. Varas G. Fdez‐Manin C. Carranza‐Torres 《国际地质力学数值与分析法杂志》2003,27(13):1153-1185
A literature review has shown that there exist adequate techniques to obtain ground reaction curves for tunnels excavated in elastic‐brittle and perfectly plastic materials. However, for strain‐softening materials it seems that the problem has not been sufficiently analysed. In this paper, a one‐dimensional numerical solution to obtain the ground reaction curve (GRC) for circular tunnels excavated in strain‐softening materials is presented. The problem is formulated in a very general form and leads to a system of ordinary differential equations. By adequately defining a fictitious ‘time’ variable and re‐scaling some variables the problem is converted into an initial value one, which can be solved numerically by a Runge–Kutta–Fehlberg method, which is implemented in MATLAB environment. The method has been developed for various common particular behaviour models including Tresca, Mohr–Coulomb and Hoek–Brown failure criteria, in all cases with non‐associative flow rules and two‐segment piecewise linear functions related to a principal strain‐dependent plastic parameter to model the transition between peak and residual failure criteria. Some particular examples for the different failure criteria have been run, which agree well with closed‐form solutions—if existing—or with FDM‐based code results. Parametric studies and specific charts are created to highlight the influence of different parameters. The proposed methodology intends to be a wider and general numerical basis where standard and newly featured behaviour modes focusing on obtaining GRC for tunnels excavated in strain‐softening materials can be implemented. This way of solving such problems has proved to be more efficient and less time consuming than using FEM‐ or FDM‐based numerical 2D codes. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献