Geologia Croatica最新文献

{"title":"Multi-point geostatistics for ore grade estimation","authors":"Yu-Chen Song, Zhan-Ning Liu, Hai-Dong Meng, Xiao-Yan Yu","doi":"10.4154/gc.2019.23","DOIUrl":"https://doi.org/10.4154/gc.2019.23","url":null,"abstract":"A multi-point geostatistical method for ore grade estimation is introduced in order to fully utilize existing sampling information. A block model is used to construct a new three-dimensional training image instead of a variogram. Data events and pattern matching is improved, and the directionality of the data template is considered in the matching. The inverse distance weighted method is used to make up for the lack of multi-point geostatistics. The research improves the reliability of multi-point geostatistical estimation. Optimal estimation results for Li2O and Ta2O5 come from the inverse distance weighted, ordinary Kriging, and multi-point geostatistical methods. Multi-point geostatistical estimation results are compared with those of the inverse distance weighted and ordinary Kriging methods. Deviation, trend, and variogram analyses are used to assess the effect of multipoint geostatistical estimation. This study shows that reducing the samples participating in the estimation can reduce the maximum and minimum deviation of the estimated grade to a certain extent. The grade distribution pattern is the primary factor affecting minimum and maximum deviation. This study proves the reliability and accuracy of the multi-point geostatistical method for ore grade estimation.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44187233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of in situ soil nitrogen mineralization in a Picea-Abies forest in Tibet Plateau: effects of increased nitrogen input","authors":"Ge Wang, Lin Han, Xinying Tang, Yu Yang","doi":"10.4154/gc.2019.27","DOIUrl":"https://doi.org/10.4154/gc.2019.27","url":null,"abstract":"The main objective of this study was to quantify the dynamics of ammonium (NH4+) and nitrate (NO3-) in the humus (0-7cm) and the uppermost mineral layer (0-15cm) of a forest soil. The soil was treated annually from 2012 to 2013 with one single dose of nitrogen (0, 15, 30kg N ha-1yr-1 applied as (NH4)2SO4, NH4Cl, KNO3). Net N mineralization, including net ammonification and net nitrification was determined in four in situ incubation periods over 2 years in a Picea-Abies forest stand at the Qinghai-Tibet Plateau, Southwest China. Measurements were done using soil cores (7cm or 15cm deep) with a resin bag filled with combined anion and cation exchange resins placed at the base to collect the N leaching from the soil. The accumulation rate of N was corrected for both deposition and fertilizer N inputs. In all treatments, both the content and accumulation of the mineral N were dominated by NH4+ which accounts for about 76-89% of the net mineralization. The accumulation rate of N decreased to 64-83% in KNO3 treatments. The net N mineralization rate increased with nitrogen input, especially in NH4+-N treatments (p<0.05). However, this promoting role decreased over time. At the highest (NH4)2SO4 additions, the net ammonification and net mineralization rate increased notably in the humus (0-7cm) rather than in the uppermost mineral layer (0-15 cm). Previous studies that reported on soil net mineralization from forests under different environmental conditions were compiled and assessed for the effects of atmospheric N deposition and environmental factors, annual precipitation, and annual temperature on annual fluxes of net nitrogen mineralization in forest soils, worldwide. The results show that an increase in atmospheric N deposition significantly enhances the soil net nitrogen mineralization rate. Variation in atmospheric N deposition accounts for 48% of the variation in the rate of soil net nitrogen mineralization across the forests.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49109266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modification of slope stability probability classification and its application to rock slopes in hydropower engineering regions","authors":"L. Xiuzhen, Tan Rong-zhi, G. Yan","doi":"10.4154/gc.2019.20","DOIUrl":"https://doi.org/10.4154/gc.2019.20","url":null,"abstract":"Stability assessment of rock slopes in hydropower engineering regions is an important and complex issue. Rock mass classification systems are a good approach because they can thoroughly consider many factors influencing rock slope stability. The slope stability probability classification (SSPC) system is a novel method. However, it has two limitations when applied to rock slopes: 1) it is only suitable for slopes less than 45 m in height, and 2) there is great subjectivity and randomness in the estimation of intact rock strength. Therefore, this study presents two modifications of the SSPC system by adopting the Hoek-Brown strength criterion and an empirical formula for maximum slope height. Evaluation of results from of 34 typical rock slopes of the major hydropower engineering regions in China indicated that the accuracy rate of the modified SSPC for stability evaluation of these slopes was 61.8%, and the accuracy for stability evaluation of 10 slopes with non-structural control failure was 80%. The stability values of stable and unstable slopes obtained using the modified SSPC were different to those obtained using the Chinese Slope Mass Rating (CSMR) and modified CSMR systems. In addition, the identification accuracy rate of the modified SSPC was significantly higher than that of the CSMR and modified CSMR. Therefore, the modified SSPC can be applied to hydropower engineering regions, providing a new means of rapidly evaluating the slope stability of high rock slopes (slopes > 45 m in height) in these regions.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4154/gc.2019.20","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48068072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry and U-Pb ages of the diabases from the Luoji area, western Yunnan, China: implications for the timing of initial rifting of the Ganzi-Litang Ocean","authors":"Chan Wang, Hao Liu, H. Feng, Jianghong Deng, Xian-fan Liu, Fufeng Zhao","doi":"10.4154/gc.2019.25","DOIUrl":"https://doi.org/10.4154/gc.2019.25","url":null,"abstract":"Detailed geochemical and U-Pb studies of two diabases (Luoji and Cuiyi) from the Luoji area have been undertaken. The diabases are high-K calc-alkaline and belonging to the tholeiitic series, enriched in large ion lithophile elements, Ti, Zr and light rare earth elements, and depleted in high field strength elements. These characteristics are different from the oceanic island basalt but highly consistent with the continental rift basalt, indicating the Luoji and Cuiyi diabases are the products of the intracontinental rift related to the initial opening of the Ganzi-Litang Ocean. The Luoji and Cuiyi diabases originated from an enriched mantle source with a small degree of crustal contamination during their emplacement. Zircon U-Pb ages show that the Luoji and Cuiyi diabases were emplaced at 293.4 +/- 5.4Ma. Therefore, we propose that the time of initial rifting of the Ganzi-Litang Ocean occurred during the very Early Permian.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42678226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochronology, geochemistry, and tectonic significance of the Shirenshan gneiss in the southern margin of the North China Block","authors":"Jingya Wang, S. Ren, S. Dong, Longming Li, D. Jiang, Yong-hong Shi, Jiahao Li, Chuanzhong Song, Xu Hang, Zhenqiang Li, J. Ouyang","doi":"10.4154/gc.2019.21","DOIUrl":"https://doi.org/10.4154/gc.2019.21","url":null,"abstract":"The Shirenshan Block is a complex geological body located in the southern margin of the North China Block (NCB). From south to north, it can be divided into the Taihua Group migmatite, and the Shirenshan gneiss and magmatic rocks. The petrographic features, tectonic setting, provenance, and geological age of the Shirenshan gneiss using comprehensive field investigations, microstructural analysis, zircon U-Pb radioactive dating, and geochemical analyses were investigated for this study. The petrology, geochemistry, and geochronology of the Shirenshan gneiss suggests that it is mainly a felsic rock and its protolith was a high-K calc-alkaline series A-type granite. The protolith is high in SiO2, Al2O3, K2O, Na2O, and low in CaO and MgO. Overall, the Sr-Nd isotope composition of the samples showed no significant difference, indicating that the Taihua Group migmatite and the Shirenshan gneiss have the same source material. The Shirenshan block may be partially melted from the Taihua group and formed during activity of the Luo-Luan Fault. By the method of zircon dating analysis, the protolith age of the Shirenshan block was determined as 1559±16Ma (Early Proterozoic). Then, the crystallization age of the syntectonic migmatite is 439.2±7.6Ma, which was formed by subduction of the Taihua Group. During the early Cretaceous (119.5±1.3Ma), the Shirenshan gneiss may have experienced regional migmatization and formed the zircon rims age of the Yanshanian period. Litho-geochemical features of the Shirenshan block are similar to A1-type granites indicating that they are post-orogenic. Therefore, the metamorphic deformation of the Shirenshan gneiss reflects the tectonics in the southern margin of the NCB.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49511342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Integrated 3D modeling of Quaternary sediments in the Beijing Plain, based on a sequential indicator simulation","authors":"Xiaoyan Ai, B. Sun, Xiangzhao Chen","doi":"10.4154/gc.2019.28","DOIUrl":"https://doi.org/10.4154/gc.2019.28","url":null,"abstract":"The study of Quaternary sediments has long been a focus for geologists, primarily because they are closely aligned with urban safety assessment, energy exploitation and sustainable development. The Beijing Plain was selected for this study. Using existing drilling data and knowledge of the sedimentary characteristics in this study area, a geological model was developed with Petrel software using the sequential indicator simulation algorithm. The main aims were firstly, to integrate ArcGIS and Petrel with drilling information, a digital elevation model, a stratum sedimentary thickness plan and other multi-platform data on the same platform. Secondly, establish a lithology variogram model and then construct a quaternary lithology model based on the variogram model and finally, use the established lithology model to preliminarily analyze the lateral and vertical distribution rules of Quaternary lithology in the study area. These results provide new methods for the establishment of geologic modeling during the preliminary stages when studying engineering geology. The results will also provide baseline information for later research.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70281179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ore-forming fluids of the Fancha gold deposit, Lingbao, Henan Province","authors":"Zhang-fa Yu, Ca Yi, Li Hongmeng","doi":"10.4154/gc.2019.22","DOIUrl":"https://doi.org/10.4154/gc.2019.22","url":null,"abstract":"The Fancha gold deposit is a representative of the auriferous quartz vein type gold deposits in the Xiaoqingling gold district where the ore-forming fluid is one of the key controlling factors in the deposits formation, and also the main focus of ore deposit research. Here, the geological characteristics and fluid inclusions of the Fancha deposit are presented in detail, with a description of the potential origin and evolution of the fluid and the genesis of the deposit. Field investigation and petrographic observation show that ore-bodies in the Fancha deposit are preferentially hosted in the amphibolites of the Taihua Group and are controlled by brittle fracture. Hydrothermal alteration in the Fancha deposit includes silicification, potash feldspathization, sericitization, pyritization and carbonatization. The mineral assemblage, cross-cutting and replacement relationships indicate that the ore-forming process can be divided into quartz-K-feldspar (I), quartz-coarse pyrite (Ⅱ), quartz-fine pyrite (III), quartz-polymetallic sulfide (IV) and carbonate stages (V). Gold is mainly precipitated in stages III and IV. Three types of fluid inclusions have been identified in the Fancha deposit, based on their characteristics at room temperature: three-phase CO2-rich, three-phase CO2-bearing and two-phase aqueous inclusions. The fluid inclusions demonstrate the modes of homogenization temperatures of 363.3℃, 325.5℃, 273℃, 258.62℃ and salinities of 14.53, 9.59, 11.61, 8.03 wt% NaCl.equiv., for stages II, III, IV, and V respectively. The ore-forming fluid in the Fancha deposit belonged to the CO2-H2O-NaCl-(±CH4) fluid system with mid-low temperature and mid-low salinity. The δ18OH2O of the metallogenic fluids was between 1.36 and 6.28, and the δDH2O was between -87 and -53.1. Hydrogen and oxygen isotope data indicate that the ore-forming fluids were dominated by metamorphic fluids in the early stage, and that the metamorphic fluid gradually mixed with circulating meteoric water during the later stages. Petrographic observation and microthermometry suggest that fluid mixing and immiscibility obviously occurred during the main metallogenic stage. Fluid mixing and fluid immiscibility probably led to gold deposition in the Fancha deposit.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47337253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Meso/Micro-texture analysis of the landslide-dam outburst sediments in the Upper Jinsha River, SE Tibetan Plateau","authors":"Jian Chen, Z. Cui, Chaohui Liu, Wendy Zhou, Ruichen Chen","doi":"10.4154/gc.2019.29","DOIUrl":"https://doi.org/10.4154/gc.2019.29","url":null,"abstract":"Outburst sediments are widely distributed in the Upper Jinsha River in the Southeastern (SE) Tibetan Plateau. In order to understand the sedimentary characteristics of these sediments, gravel fabric, particle size distribution and quartz sand surface textures were used to analyze the mesotextures and microtextures of the Xuelongnang outburst sediments. It was determined that these sediments usually have a short transport distance, and are distributed over a distance of approximately 3.5 km. The gravel fabric and particle size distribution analysis represent the different mesotextures with different transport distances and suggest gradually changing hydrodynamic conditions. The statistical data of quartz surface textures exhibit the transformation process of quartz sands by outburst flood. The variation from abundant sub-angular shapes (> 75%); to common V-shaped percussion cracks, solution crevasse, medium relief, and chatter marks (50% to 75%); to rare meandering ridge, underwater polished surface, large conchoidal fracture (> 100 μm), directional etch pits, and crystalline overgrowths (< 5%), present the features in different combinations to other sedimentary environments. The microtexture characteristics of landslide-dam outburst deposits are also consistent with those of the mesotextures. As the distance from the residual dam increased, the quartz grain microtextures showed gradual or abrupt changes, such as increased frequencies of V-shaped percussion cracks, decreased frequencies of the adhering particles, and growth of the solution crevasses. These findings could potentially be used as a discriminant mark to distinguish outburst sediment from other types of sediments, e.g., subaqueous, eolian, glacial, etc.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41616292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new numerical method for the analysis of monolithic seepage problems with complex drainage systems in a groundwater recharge area for a hydropower station in China","authors":"Y. Jun, Liu Si-hong, Wei Ying-qi, Jin Song-Li, Cai Hong, Xiao Jian-zhang","doi":"10.4154/gc.2019.24","DOIUrl":"https://doi.org/10.4154/gc.2019.24","url":null,"abstract":"After construction of a dam impounding water in a reservoir, a monolithic seepage field develops in the surrounding rock mass. Here, a new finite element method is proposed for determining the shape and characteristics of the 3D monolithic seepage field including the free surface, considering complex drainage systems consisting of densely-spaced drainage holes and drainage galleries. To this end, the previously proposed virtual flux method is improved by a refined numerical integration scheme and a regularized Heaviside function for distinguishing the subregions below and above the free surface within a particular finite element. Leakage and overflow drainage holes are modeled as internal boundaries. The proposed numerical method is verified by an academic example, for which the analytical solution is available. Finally, the numerical simulation of the seepage field developing in the vicinity of a high dam and underground power house, constructed in the context of a hydropower plant project in China is used to show its application to a problem in engineering practice.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44597898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dispersed plant mesofossils from the Permian of Wuda, Inner Mongolia, Taiyuan Formation, China","authors":"Z. Šimůnek, J. Bureš","doi":"10.4154/gc.2019.17","DOIUrl":"https://doi.org/10.4154/gc.2019.17","url":null,"abstract":"A coal sample from the Lower Permian Taiyuan Formation (Wuda locality, Inner Mongolia, China) was macerated. It yielded two cuticle fragments and many fragments of conducting tissue. One cuticle fragment shows strongly corroded polygonal cells belonging either to a pteridosperm or a cycad. The second fragment is an abaxial cordaitalean cuticle with papillate tetragonal cells and can be compared to Cordaites neimengensis LIU et al. 1998. The conducting tissue are represented by biseriate to quadriseriate tracheid pitting that is typical for cordaitaleans.","PeriodicalId":55108,"journal":{"name":"Geologia Croatica","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2019-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.4154/gc.2019.17","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44764247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}