Geochemical soil prospecting in Northwest Kalimantan, Indonesia     

W. Viaene  T. Suhanda  N. Vandenberghe  Y. Sunarya  R. Ottenburgs 《Journal of Geochemical Exploration》1981,15(1-3)

A target area in northwestern Kalimantan, Indonesia, already defined by a geochemical stream-sediment survey, has been further investigated by geochemical analysis of soils and samples of test pits. Overlapping geochemical anomalies in the soils were found for Cu, Mo, Au and Bi. Anomalies and high values of the other elements, Pb, Zn, Fe, Mn and As, can be explained by lithology and by scavenging and coprecipitation phenomena at the break of slopes.With the aid of detailed geochemical mapping and mineralogical and petrographic analysis the Cu-Mo-Au-Bi anomaly was explained by a porphyry-type mineralization consisting mainly of chalcopyrite and molybdenite within a quartz-enriched granodiorite. Hydrothermal alteration consists of a potassic zone, including the anomaly, and a broad propylitic zone. This type of mineralization is related to the plate-tectonic evolution of Sundaland. The possibility of a belt of porphyry-type mineralization in western Kalimantan is proposed.  相似文献   

Comparing Training-Image Based Algorithms Using an Analysis of Distance   总被引：1，自引：1，他引：0  

Xiaojin Tan  Pejman Tahmasebi  Jef Caers 《Mathematical Geosciences》2014,46(2):149-169

As additional multiple-point statistical (MPS) algorithms are developed, there is an increased need for scientific ways for comparison beyond the usual visual comparison or simple metrics, such as connectivity measures. In this paper, we start from the general observation that any (not just MPS) geostatistical simulation algorithm represents two types of variability: (1) the within-realization variability, namely, that realizations reproduce a spatial continuity model (variogram, Boolean, or training-image based), (2) the between-realization variability representing a model of spatial uncertainty. In this paper, it is argued that any comparison of algorithms needs, at a minimum, to be based on these two randomizations. In fact, for certain MPS algorithms, it is illustrated with different examples that there is often a trade-off: Increased pattern reproduction entails reduced spatial uncertainty. In this paper, the subjective choice that the best algorithm maximizes pattern reproduction is made while at the same time maximizes spatial uncertainty. The discussion is also limited to fairly standard multiple-point algorithms and that our method does not necessarily apply to more recent or possibly future developments. In order to render these fundamental principles quantitative, this paper relies on a distance-based measure for both within-realization variability (pattern reproduction) and between-realization variability (spatial uncertainty). It is illustrated in this paper that this method is efficient and effective for two-dimensional, three-dimensional, continuous, and discrete training images.  相似文献   

Aeolian origin and palaeoclimatic implications of the ‘red clay’ (north China) as evidenced by grain‐size distribution     

Huayu Lu  Jef Vandenberghe  Zhisheng An 《第四纪科学杂志》2001,16(1):89-97

The ‘Red Clay’ is an important deposit underlying the Quaternary loess–palaeosol sequence in the Chinese Loess Plateau, being regarded as an excellent record of palaeoclimate changes in the late Tertiary. Several properties of the ‘Red Clay’ have been measured previously in order to derive climatic information. However, the sedimentary processes involved and the origin of the materials remain controversial. Here we present results of grain‐size analyses of the ‘Red Clay’ from four representative sites in the Chinese Loess Plateau. In particular their grain‐size distribution is compared with that of typical Quaternary aeolian loess–palaeosol, as well as lacustrine and fluvial sediments. It appears from the sedimentological evidence that the major part of the ‘Red Clay’ is of aeolian origin. It is rather similar in some of its properties to the Quaternary loessic palaeosols. The dust forming the ‘Red Clay’ was transported by a wind system that was weaker than that involved in the accretion of the Quaternary loess. Furthermore, the ‘Red Clay’ sediment has been modified by post‐depositional weathering. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献