ALBERT

Description: 〈span〉〈div〉Abstract〈/div〉The abundance and spatial distribution of mercury in soil samples covering nearly the whole of China (approximately 9 million km2) were obtained by the China Geochemical Baseline (CGB) project from 2008 to 2015. This project allows a further systematic study on national-scale Hg geochemical distribution patterns in soils. Comparing the data and maps, it was found that the Hg contents both in the top (0-25 cm) and deep soil (below 100 cm or C-horizon) of the karst area in southwestern China were relatively richer than that of any other geographical landscape areas. This regional-scale high Hg distribution is mainly due to high Hg geochemical background of bedrocks and soil formation on limestone. A large-scale epithermal metallogenic domain developed in southwestern China and the extensive distribution of Lower Cambrian black shale in southwest China lead to a high Hg geochemical background for parent rocks of soils. The chemical weathering of carbonate minerals and the geochemical behavior of Hg in the epigenetic environment result in Hg enrichment by ferric oxides, iron hydroxide and organic carbon in limestone soils. Human activities mostly result in local-scale Hg anomalies, but have little effect on this regional-scale anomaly.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉As the junction of the Silk Roads, the Tarim Basin played a critical role in human migration and cultural interaction between the East and the West. Recently, population migration patterns have been increasingly reconstructed from strontium isotope ratios (〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr) in archaeological human skeletons, and further constraints on their provenance require a bioavailable 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr map across the basin. Based on measurement data from 44 river samples in this study and 29 samples from published data, we generate the first map of bioavailable 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr values across the Tarim Basin and the neighbouring area. From the baseline map, three geologically distinct regions can be identified: (1) the Yili Block, Tian Shan orogenic belt and northern Tarim Block with lower ratios (0.7105 ± 0.0007 (1σ), 〈span〉n〈/span〉 = 25); (2) the southern Tarim Block with higher ratios (0.7118 ± 0.0008, 〈span〉n〈/span〉 = 29); and (3) the eastern Pamir Block with diverse values (0.7110 ± 0.0009, 〈span〉n〈/span〉 = 19). This map is a promising tool for recognizing the origins of immigrants in the Tarim Basin and may aid understanding of the migration patterns and cultural communication along the Silk Roads.〈/span〉

Description: In the Three Gorges major landslides are the primary disasters, and endanger the normal running of the Three Gorges Dam and the life and property of the residents in the region. Hence, it is very important to formulate effective strategies for the prevention and remediation of landslides in this region, as part of which landslide mechanism analysis is an important task. In this paper, landslide mechanism analysis in the Three Gorges is carried out based on spatial data mining and knowledge discovery. The 1:50000 geological map, 1:10000 relief map and China-Brazil Earth Resources Satellite (Cbers) images were adopted to produce the key factors influencing landslide development, including engineering rock group, reservoir water fluctuation, vegetation coverage, slope structure, elevation, slope and aspect. A soft partition method was adopted to elevate the knowledge levels and formulate the quantification factors qualitatively based on the cloud model. In terms of these qualitative factors, a concept grid is built based on formal concept analysis and a concept grid algorithm. Based on this concept grid, the knowledge related to landslide mechanism is mined from the multi-theme landslide data, including the associations between the various factors that influence a landslide, the circumstances in which a landslide is easily triggered, and the relationship between landslide probability and factor combination. The experimental results show that the knowledge of landslide causes mined by our method possesses high confidence and is in agreement with the field circumstances. Therefore, the spatial data mining method proposed in this paper is suitable for landslide mechanism analysis. It can achieve the transformation between quantitative detection data of landslides and qualitative human mind, thereby leading to an innovative approach for landslide mechanism analysis.

Description: 〈span〉〈div〉Abstract〈/div〉The strata of the Linxi Formation (LXF) occupy an extensive area in eastern Inner Mongolia, NE China, and have close spatial and genetic relationship with some significant Mesozoic Sn-Cu-Pb-Zn-Ag veins and porphyry polymetallic deposits (ore occurrence). The rock types of the LXF mainly include sandstone, siltstone and shale. Major and trace element data (including REE) of rocks from the LXF in Hanmiao area indicate that these rocks have a greywacke protolith, derived from intermediate-acid arc igneous rocks and deposited during intensive tectonic activity. LA-ICP-MS U-Pb dating of detrital zircons from sandstone of the LXF yields ages of 985±10 Ma to 242±2 Ma. The youngest population of ages shows a peak at ca. 258 Ma, suggesting that the major deposition period of the LXF was in the late Permian. These ages, together with the youngest zircon age (ca. 242Ma), suggest that the deposition of the LXF mainly occurred during the late Permian and extended to the early Triassic. According to the results of analysis of 44 sandstone and siltstone samples, ore elements, e.g. W, Sn, Ag and Mo, are significantly enriched in the LXF of the study area. Combined with the fact that more and more polymetallic deposits have been discovered within the LXF strata in the southern Great Xing'an Range (GXR), it can be concluded that the strata of the LXF might be the ore source bed, and there is a large ore-prospecting potential for polymetallic deposits in the LXF of the GXR.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The strata of the Linxi Formation (LXF) occupy an extensive area of eastern Inner Mongolia, NE China and have close spatial and genetic relationships with important Mesozoic Sn–Cu–Pb–Zn–Ag veins and porphyry polymetallic deposits (ores). The rock types of the LXF include sandstone, siltstone and shale. Major and trace element (including rare earth element) data for rocks from the LXF in the Hanmiao area indicate that these rocks have a greywacke protolith derived from intermediate to acidic arc igneous rocks and were deposited during intensive tectonic activity. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of detrital zircons from sandstones in the LXF yields ages of 985 ± 10 to 242 ± 2 Ma. The youngest population of ages shows a peak at 〈span〉c.〈/span〉 258 Ma, suggesting that the main period of deposition of the LXF was in the late Permian. These ages, together with the youngest zircon age (〈span〉c.〈/span〉 242 Ma), suggest that the deposition of the LXF mainly occurred during the late Permian and extended to the early Triassic. According to the results of the analysis of 44 sandstone and siltstone samples, ore elements (e.g. W, Sn, Ag and Mo) are significantly enriched in the LXF in this region. Combined with the fact that increasing numbers of polymetallic deposits have been discovered within the LXF strata in the southern Great Xing'an Range, we conclude that the strata of the LXF may be the source bed of the ore and there is potential for ore prospecting in the polymetallic deposits of the LXF in the Great Xing'an Range.〈/span〉

Description: Multivariate statistical methods can be applied to analyse a complete set of multidimensional geochemical data and to identify latent relationships among these data. In this paper, we used multivariate statistical analysis, including k-means clustering, principal component analysis (PCA) and factor analysis (FA), to study the similarity of the sampling points and the relationships between metal mineralization and geological environment in the Nanling metallogenic belt, South China. The dataset consists of 1617 sediment samples analysed for 39 elements. The dataset was divided into three clusters by k-means clustering which were strongly associated with the distribution of lithostratigraphic units and the level of metal mineralization. Each cluster was analysed by PCA to identified principal components. Three factors extracted by the factor analysis explained c. 62% of the total variance and allow identification of the dominant ore-forming environment. Factor 1 describes c. 30% of the common variance and is highly loaded by Zn, Cu, Cr, Co, Ni, Mn, P, Ti, V, Mg and Fe. Factor 2 includes rare metals, rare earth elements (REE) and radioactive elements with Y, La, Nb, Zr and U, explaining c. 19% of the common variance. Factor 3 describes c. 14% of the common variance and is highly loaded by W, Sn, Mo, Pb, Be and Bi, representing tungsten polymetallic mineralization. In this paper, the Student’s t-test derived from weights-of-evidence modeling was used to measure the significance of spatial correlation between factor scores and mineral deposits.

Description: Delineation of vertical distribution patterns of elements in overburden over a concealed deposit is essential for determining potential upward migration mechanism of elements and for predicting undiscovered mineral deposits. The aim of this study is to identify the vertical distribution features of elements in the regolith over the Jinwozi gold field, NW China by using factor analysis (FA) and concentration-volume (C-V) fractal modeling based on the data-set generated from 70 overburden drilling boreholes. Firstly, the zones of different gold enrichment states were obtained by the C-V fractal method. Secondly, FA was utilized to define the mineralization-related element association. Finally, the C-V method was applied to the relevant association defined by FA. The results showed that: (1) the C-V fractal method distinguished four enrichment states determined by Au thresholds of 1.6, 7.9 and 39.9 ng/g and by factor scores of –1.14, 0.33 and 1.45; (2) the first factor that describes 41.5% of the common variance has positive loadings in Au, As, Sb and Mo; (3) the zones of both high Au contents and factor scores generally showed horizontally northeasterly distribution along the ductile-shearing alteration belt and vertically top-bottom symmetric distribution in the regolith over the deposit; (4) the rest of the zones determined by the C-V fractal model properly delineated the zones of low and high backgrounds and moderate Au enrichment; and (5) the moderately-enriched zones of the raw Au data are better than those of the factor scores, and the rest of the zones have the similar distributions. These results indicate that: (1) the distribution of elements in the regolith was the product of nonlinear natural processes resulting in an enrichment pattern at the surface over the deposit; and (2) the integration of FA and C-V fractal model is effective for the delineation of 3D geochemical patterns.

Description: 〈p〉Lacustrine-tsunami risk from landslides can be significant yet for most locations globally the hazard remains unquantified. Lake Tekapo, in the tectonically active mountain belt of New Zealand's South Island, has been chosen to develop surveying and modelling techniques to assess the hazard from landslide tsunamis. Lake Tekapo is ideal for this study due to the high sedimentation rates, steep surrounds and the proximity to active faulting that indicate a high landslide potential. The shoreline tourist settlement and hydropower infrastructure mean the impact of any tsunami could be significant. In 2016 a survey was carried out to collect high-resolution (1 m grid) EM2040 multibeam bathymetry, high-resolution seismic reflection data (Boomer and chirp) and 6 m long sediment cores. These data reveal a diverse range of sedimentary processes in response to high sediment input and numerous landslides with varied styles of emplacement. For example, a one-off landslide initiated 40 m above the shoreline with debris deposits that have runout onto the lake floor to 100 m water depth contrasts with the Cass River delta on the western shore that has failed multiple times during the lake-basin infilling history. Landslide-generated tsunami scenarios are used to determine the relative hazard at different regions of the lake to guide development of a probabilistic tsunami model.〈/p〉

Description: 〈span〉〈div〉Abstract〈/div〉The Qinling region is located in the central part of the China mainland and carries abundant mineral resources. Stream sediment and rock geochemical data of the Qinling region collected from the Regional Geochemistry-National Reconnaissance Project of China and the China Geochemical Baselines Project, respectively, were used to identify the Pb distribution pattern and to explain the geogenic sources of geochemical anomalies. The singularity mapping technique was applied to extract local Pb ore-related geochemical anomalies from complicated geochemical backgrounds. One geochemical mega-province, one geochemical province, and three regional anomalies were delineated in a Pb geochemical map of the Qinling region. The spatial distributions of the regional anomalies are all consistent with that of known Pb metallogenic districts, but only local high anomalous areas in the geochemical province and mega-province contain economic Pb ore deposits. Regions with singularity indices of less than 1.884 occupy 2.70% of the total study area, but contain 60% of the total known Pb deposits in a Pb singularity map of the Qinling region. Targets delineated in the Pb singularity map not only highlighted known areas of Pb mineralization, but also identified areas of high potential for undiscovered ore deposits in the Qinling region.〈/span〉

Description: The increasing demand in recent years for energy in China has resulted in coal being mined in complex geological conditions. This has included the mining of coal seams located beneath reservoirs, aquifers and flooded abandoned mine workings. Throughout China the extraction of coal in these circumstances has resulted in groundwater inrushes into working mines. This has caused loss of lives, disruption or abandonment of coal mining, and the sterilization of coal resources. This paper demonstrates that numerical modelling using ANSYS-2D, FLAC-2D and FLAC-3D combined with field observations may provide a method for the modelling of fractures that develop in the rock mass above a roof of coal mines. These fractures may increase significantly the permeability of the strata and groundwater flows into mine workings.