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1.
Analysis and mapping of geochemical anomalies using logratio-transformed stream sediment data with censored values 总被引：1，自引：0，他引：1
There is lack of research and documentation of actual (as opposed to theoretical) benefits (e.g., mineral deposit discovery) of developments in compositional data analysis and imputation of censored values to mineral exploration geochemistry. In the present study, analyses of logratio- and ln-transformed stream sediment geochemical data containing ca. 30% of samples with censored values of a pathfinder element for the mineral deposit-type of interest yielded the following findings. Exclusion of those samples supports interpretation of multi-element anomalies reflecting the presence of mineralization. However, the multi-element anomaly maps obtained by exclusion of those samples are barely better than the multi-element anomaly maps derived by inclusion of those samples after replacing the censored values with 1/2 of detection limit or with imputed values. Logratio (i.e., alr, clr, or ilr) transformation, compared to ln-transformation, of stream sediment geochemical data does not improve mapping of pathfinder element anomalies reflecting the presence of mineralization. However, stream sediment geochemical data, excluding or including censored values (replaced with 1/2 of detection limit or with imputed values), should be clr- or ilr-transformed to enhance recognition of anomalous multi-element associations reflecting the presence of mineralization. The anomaly maps of multi-element associations derived from ilr-transformed data are better, albeit slightly, than the anomaly maps of multi-element associations derived from clr-transformed data. In the present study, the main benefit of either clr- or ilr-transformation, compared to either ln- or alr-transformation, of stream sediment geochemical data is the enhancement of anomalous multi-element associations reflecting the presence of mineralization. This is an important benefit because variations in trace element concentrations in regional-scale stream sediment geochemical data are mostly due to lithology and other factors (or processes) unrelated to mineralization. Further investigations of various exploration geochemical data are needed to demonstrate and document the actual (as opposed to theoretical) benefits of developments in compositional data analysis and imputation of censored values to mineral exploration. 相似文献
2.
我国铀矿床主要划分为四大类型,包括花岗岩型铀矿床、火山岩型铀矿床、砂岩型铀矿床和碳硅泥岩型铀矿床。花岗岩型铀矿约占我国已探明铀矿总资源储量的三分之一以上,是我国重要的铀矿化类型。地球化学勘探方法对花岗岩型铀矿床勘查具有良好的效果。根据全国铀矿资源潜力评价项目研究成果,在大量研究中国花岗岩型铀矿化水系沉积物地球化学异常特征基础上,总结了一套对花岗岩型铀矿化勘查稳定的、行之有效的指示元素及其组合,确定了花岗岩型铀矿化地球化学异常模式,并以实例说明典型花岗岩型铀矿化异常模式。水柰沉积物地球化学异常是进行铀矿产预测评价的有效手段,对铀矿资源的潜力评价发挥了重要作用。 相似文献
3.
黑龙江省呼玛县西部兴隆-基座山地区为瓦拉里-兴隆金矿带中重要的金矿化集中区。区内水系沉积物测量主要组合异常区地质特征与呼玛矿集区已知浅成低温热液金矿床地质特征具有可比性,在岩性条件、构造环境、矿化蚀变等方面和矿集区矿床地质特征相一致。区内水系沉积物及土壤测量均发现存在Au、Ag、As、Sb、Bi、Cu组合异常,异常分带清晰,具有明显的浓集中心。水系沉积物主要异常元素组合与矿集区已知浅成低温热液金（银）矿床周围异常元素组合相一致,金异常及其伴生元素异常均受次级断裂构造、岩体与地层接触带及破碎带控制。依照类比结果,区内划分了3个异常远景区,对部分远景区进行工程揭露,发现蚀变矿化带金含量明显增高,局部可见金矿化体,表明区内寻找浅成低温热液型金矿床具有广阔前景。 相似文献
4.
森林沼泽景观元素次生分散富集特征 总被引：3，自引：1，他引：2
得尔布干森林沼泽区的景观特征是冬季寒冷,夏季降雨集中,中低山沟谷长而平缓,植被发育,土壤A层和水系沉积物中富泥炭,土壤呈弱酸性、弱还原环境.铅锌矿床形成的异常从岩石、土壤C层、土壤A层到水系沉积物元素含量降低,呈逐步分散.水系沉积物中Pb、Zn元素含量随粒度变细而降低,Ag、有机碳含量增高.水系中泥炭沉积物可吸附活动态金属元素,在背景地段可形成次生富集和"假异常".有机质影响水系沉积物异常,为干扰因素,应消除有机质影响.水系沉积物中碎屑沉积物能较好反映矿化异常.确定合理采样介质、密度,采样到位,可提高中大比例尺地球化学勘查效果. 相似文献
5.
利用相态研究可确定异常元素的赋存状态,马架子水系沉积物综合异常强度高,浓集中心明显,经过几次异常检查及查证,未获得良好的找矿效果,引起异常的成因机制不清。对异常样品中元素在氧化物相、结合相及硫化物相中分配的综合研究证实,Ph、Zn元素主要是以均匀分散形式存在于岩石中,为非矿致异常,从而节省了大量的人力、财力及物力,为异常查证及评价提供了一套新的思路。 相似文献
6.
1∶5万水系沉积物测量显示,平然地区矿化异常是一个以Cu、Ni、Co异常为主,伴随有Cr、V、Ti等的多元素组合异常,体现了基性—超基性岩石的成矿专属性。对元素分布特征、单元素异常特征、异常元素组合特征进行了研究,得出该区异常主要受区域性NW向断裂构造和基性—超基性岩石控制。对平然地区水系沉积物测量数据聚类分析表明,15种元素可以分为三类:Ni、Cr、Cu、V、Co、Zn、Ti为一类,反映了与基性—超基性岩有关的元素分布、富集特征和相关矿化信息;As、Sb、Pb为一类,反映了与中低温热液作用有关的矿化信息;剩余元素的相关性差,归为一类。平然地区F1主因子可能代表了与基性—超基性有关的Cu、Ni、Co矿化。对平然地区3806个样品分别计算F1因子得分,得分大于2的607个样品分布特征与Cu、Ni、Co异常分布特征大致吻合。因此,Cu、Ni、Co异常区域及F1因子得分大于2的样品所在区域的重叠处应该是以Cu、Ni、Co为主的重点找矿区域。 相似文献
7.
SHI Changyi ZHANG Jinhua China University of Geosciences Beijing Institute of Geophysical Geochemical Exploration Langfang Hebei 《《地质学报》英文版》2003,77(1):72-80
Regional stream sediment surveys at a 1:200,000 scale reveal positive and negative regional multi-element geochemical anomalies over medium to large copper-polymetallic orefields of different genetic types in China. Regional geochemical anomalies of orefield refer to those geochemical anomalies that are related to metallogenesis of an orefield in a certain area. The anomaly area is typically 10 to 100 km2. The regional multi-element anomalies related to mineralization can be divided into three groups, that is, the ore-element anomaly association, indicator element anomaly association, and metallogenic environmental element anomaly association. Their common spatial distributions over ore deposits or orefields possess unique structures.The model of spatial structure of regional multi-element geochemical anomalies (RAGSS) of an orefield delineates structural feature possessed by orderly spatial distributions of different groups of multi-element anomaly associations related to orefield metallogenesis. It is 相似文献
8.
在高寺台超镁铁杂岩体发现了2种铂族元素异常:一种异常分布在杂岩体纯橄榄岩或橄榄岩带的镁质超基性岩中,与已知的含铂族铬铁矿有关,与已知的铬、钴、镍等矿化主金属的强异常密切共生。在这种异常中,钯呈甚低的背景分布,w(Pt)/w(Pd)大;另一种铂族元素异常呈带状沿杂岩体透辉岩带及其中的剪切带分布,其异常特征是铂、钯异常密切共生,w(Pt)/w(Pd)近于1,并且,在这种异常中,不伴生铬、镍等元素的强异常。这是一种新的铂、钯等元素的地球化学富集和矿化。研究表明,采用岩石、土壤、水系沉积物铂、钯地球化学勘查技术,可以发现难识别的铂族矿化。 相似文献
9.
Robert H. Carpenter Timothy A. Pope Robert L. Smith 《Journal of Geochemical Exploration》1975,4(3):349-363
Downstream dispersion curves for certain trace metals were obtained from two mineralized areas in the southeastern United States. Fe-Mn oxide coating on lithic fragments and quartz pebbles, as well as the minus 80-mesh fraction of the coexisting stream sediment were analyzed for a variety of metals. In Lincoln County, Georgia, 8 sample sets were collected along a stream draining the Magruder mine, a polymetallic sulfide deposit (Zn-Cu-Pb-Ag-Au) in metavolcanic rocks. Five sample sets were collected along Joe Mill Creek in Grainger County, Tennessee, downstream from a zone of zinc mineralization in carbonate rocks (Mississippi Valley-type). In addition, 5 sample sets were collected from an unmineralized area near Athens, Georgia.The results indicate the following: (1) the anomaly/background ratio for zinc and copper is markedly higher in the Fe-Mn oxide coatings in the mineralized drainages; (2) in drainages containing lead mineralization, the anomaly/background ratio is markedly higher in the minus 80-mesh fraction for lead which is not concentrated in the coatings; and (3) the ratios Zn/Mn and Cu/Mn, as well as Zn/Co and Cu/Co, in the Fe-Mn oxide coatings enhance downstream detectability of mineralization.There are several potential advantages of using coatings versus the conventional minus 80-mesh fraction in stream sediment geochemical surveys. Because soluble metal is brought into the stream mainly in groundwater, deeper anomaly sources may be detectable from the oxide coatings than from clastic fractions of alluvium where much of the metal is derived from surficial erosion. Variability due to sampling may also be reduced, providing better discrimination of anomalies. In areas of glacial or alluvial cover, coating surveys may be particularly applicable. 相似文献
10.
钦-杭结合带南段庞西垌地区Ag-Au致矿地球化学异常信息识别与提取 总被引：2，自引：1，他引：1
基于分形与多重分形理论的非线性化探数据处理方法及以空间加权主成分分析模型为代表的地学多源信息融合技术,为致矿地球化学异常信息的识别和提取提供了有力的工具。本文以钦-杭结合带南段庞西垌地区1∶5万水系沉积物地球化学数据为例,研究如何综合运用多重分形局部奇异性与空间加权主成分分析这两种地学信息处理方法来识别和提取致矿地球化学异常信息。首先,采用滑动窗口的方法绘制了研究区与银金矿化关系密切的五种地球化学元素Au、Ag、Cu、Pb和Zn的局部奇异性指数图以增强局部弱缓异常信息。然后,在控矿条件分析的基础上,运用北东向断裂构造这一重要控矿要素对Ag-Au成矿作用的影响范围,即距离北东向断裂的距离,作为应变量来构建用于空间加权主成分分析的空间权重系数的计算模型,以此来突显化探样品在控矿地质条件约束下的空间相关性。进而,采用空间加权主成分分析方法来得到Au、Ag、Cu、Pb和Zn多元素奇异性指数值的组合异常(第一主成分因子得分)。结果表明:综合运用多重分形局部奇异性与空间加权主成分分析方法可以有效的识别和提取Ag-Au致矿地球化学异常信息,圈定具有示矿意义的多元素组合异常区。 相似文献
11.
Kaveh Pazand Ardeshir Hezarkhani Mohammad Ataei Yousef Ghanbari 《Chemie der Erde / Geochemistry》2011,71(4):397-402
This research is based on the application of stream sediments to mineral exploration. Identifying the geochemical anomalies from background is a fundamental task in exploration geochemistry. This paper applied the element concentration–area (C–A) model, to separating the geochemical anomalies from background based on a fractal approach and for the compilation of geochemical mapping from stream sediment samples (n = 620) of the Ahar region (Iran), where some Cu mineralization occurs. Comparisons of the known copper occurrences against the anomalous area created using thresholds from C–A method illustrate these hits. All of known Cu mineralizations and moreover defines two extra Cu anomaly districts. Additional sampling (n = 186) around new Cu anomaly confirms this anomaly within the district. 相似文献
12.
云南勐翁地区位于临沧—勐海稀有稀土多金属成矿亚带南端,花岗岩风化壳发育,稀土矿成矿条件优越。为配合区内矿产地质调查工作,缩小找矿范围,在该区开展了针对稀土矿产的1:5万水系沉积物测量,总结了La、Y、Zr等29种元素的地球化学分布规律、富集特征、元素组合特征及异常特征,并圈定了综合异常。分析认为La、Y、Zr、W、Sn、Au是区内主成矿元素,且La、Y与F、P等相关元素异常套合较好,其异常特征明显。在水系沉积物测量基础上开展异常查证和矿产检查工作,圈定找矿靶区3处,其中1处转化为新发现矿产地,取得了较好的找矿效果。 相似文献
13.
《Chemie der Erde / Geochemistry》2021,81(4):125830
Increasing the prediction rate in the identification of mineralization zones using the stream sediment geochemical data is an essential issue in the regional exploration stage. The various univariate (such as fractal and probability plot (PP) methods) and multivariate methods (such as principal component analysis (PCA)) have been performed for interpreting the geochemical data and detecting the mineralization areas. In this study, a new geochemical criterion named geochemical anomaly intensity index (GAII) was proposed for geochemical anomaly mapping. This approach was developed based on the PCA method and the catchment basin coefficient (CBC). The GAII as a weighted geochemical index is calculated using the mineralization principal component (MPC) scores and CBC. GAII can be mapped and utilized for geochemical anomaly mapping and detecting the mineralization areas. Besides, GAII can identify paragenesis elements better than the current methods. In this research, GAII was successfully used to generate geochemical anomaly maps on shear zone gold mineralization in the southwest of Saqqez, NW Iran. The geochemical data have been divided into three groups based on catchment basins and the host rock type. Then the MPCs and paragenesis elements of Au mineralization have been obtained individually using PCA. Three mineralization paragenesis groups consisting of (Au, Sn), (Au, W), and (Au, As, Sb and Ba) have been recognized for different catchment basins of the southwest of Saqqez district using PCA. GAII was calculated and mapped based on the CBC(Au, Sn), CBC(Au, W), CBC(Au, As, Sb, Ba), and their MPC scores. GAII accurately detected the Au mineralization zones and improved the geochemical anomaly map in this area compared to the PP method, concentration-area fractal model, and U-spatial statistics method. The results demonstrated that GAII was successfully used for (a) identifying the mineralization paragenesis elements, (b) intensifying the geochemical anomaly, and (c) increasing the prediction rate of mineralization zones. The shear zone gold mineralization areas in the southwest of Saqqez district were effectively detected using this new data analysis approach. GAII has provided better results than the current PP method, concentration-area fractal model, and U-spatial statistics method. 相似文献
14.
通过龙沟河-鲜花山地区1：5万水系沉积物测量工作,获得了较丰富的区域地球化学测量成果.利用变异系数、浓幅分位值、相关性和异常特征研究对11种元素进行了数理分析,分析元素的地球化学特征,发现Au、Ag、Mo、As、Sb为主成矿元素.结合异常分布和元素成矿特征优选出了2处成矿远景区,经槽探验证,双目咀金锑成矿远景区发现2条金矿化体. 相似文献
15.
《Chemie der Erde / Geochemistry》2021,81(4):125811
Geochemical exploration by stream sediment sampling using bulk leach extractable gold (BLEG) technique and applying concentration-number (C-N) fractal model, factor analysis (FA), and geochemical mineralization probability index (GMPI) resulted in the recognition of new Au occurrences around the Sukari gold mine in the central Eastern Desert of Egypt. The geochemical data of 128 stream sediment samples collected from the study area was used for delineating the geochemical anomalies and characterizing the dispersion trains of ore and associated elements (Au, Ag, As, Sb, Cu, Pb, Zn, Mo). Statistical analysis of the geochemical data applying the C-N fractal modeling enabled us to identify significant anomaly and background populations of the investigated elements and to construct reliable geochemical anomaly maps. Factor analysis using centered log-ratios (CLR), to address the problem of closed compositional data, revealed significant element associations for mineralization (Au, As, Mo, Zn, Ba), country rock compositions (Rb, Li, Be, Sn, Bi for granite, and Co, Cr, Ni for mafic rocks), and element mobility (e.g. Sb, Zr, and Ag). Weak and moderate Au anomalies that cannot be detected by factor score maps can be delineated clearly by using the C-N fractal method and GMPI distribution map. Our study revealed that Ag, As, and Sb are the main pathfinder elements for gold mineralization in arid to semiarid regions exemplified by the Sukari gold district. Silver can be used as a “direct” pathfinder, whereas As and Sb are “indirect” pathfinders for Au in such regions. The spatial distribution of Au and Ag anomalies indicate that gold mineralization in the Sukari district is structurally controlled. However, the spatial distribution of Cu, Pb, Zn, and Mo is controlled by mineralogical and lithological factors and is not related to any significant base metal deposits. 相似文献
16.
The Wilga and Currawong copper-zinc massive sulphide deposits in northeastern Victoria occur within a sequence of Silurian volcanics and sediments. The Wilga deposit which was discovered in mid 1978 consists of a single lens while the Currawong deposit, discovered in early 1979, consists of at least two lenses.The first indication of the presence of base metal mineralization in the area was provided by an assessment of stream sediment geochemical data contained in open-file Exploration Licence reports at the Victorian Department of Minerals and Energy.The massive sulphide mineralization does not outcrop, but the ore horizons are weakly mineralized and give rise to stringer gossans as far as 150 m up dip from ore grade mineralization. These can be identified by their trace element chemistry (anomalous values of Bi, Fe, As, Au, Pb, Hg, Se, Co, Ag and Mn) corresponding to the trace element signature of both stringer and massive sulphides.Soils in the area are essentially skeletal and residual with some colluvial movement on the steeper slopes. The soils are highly anomalous in Cu, Pb, and Zn over the projected horizon of the Wilga mineralization and the No. 2 lens at Currawong.The stream sediment responses at both Wilga and Currawong result from a combination of chemical and elastic dispersion. Downslope from the surface expression of the Wilga mineralization a spring discharges directly into the Tambo River. The spring has a very low pH and is rich in base metals resulting in enhanced metal values in both stream water and stream sediments.Analyses of selected samples of the more prominent vegetation species have failed to show a clear relationship to the mineralization. 相似文献
17.
荣那铜矿是中铝矿产资源有限公司近年在斑岩型铜矿找矿方面取得的一项重大突破。矿床产于班公湖—怒江缝合带北侧岛弧带中。公司在找矿初期重视基础地质研究,加强对地调和矿调成果的二次解剖,借鉴国内外斑岩铜矿区域分布规律,结合1∶5万磁法异常,明确多龙矿集区重点找矿方向;根据前期勘查成果,结合1∶5万水系沉积物测量成果,确定荣那、拿若为重点验证区。通过总结国外斑岩铜矿蚀变模式、矿化模式和勘查模式,选择有效的激电勘查方法圈定重点验证地段。结合隐伏斑岩体系矿化中心为中低阻、负磁异常、中等极化率,外围发育黄铁矿化壳形成近似环状中高阻、正磁异常、中高极化率异常,最终确定外围正磁、中高极化环形异常系荣那矿床与青磐岩化带有关的黄铁矿化壳引起,负磁、中等极化率异常为矿化中心部位,通过选择合理网度进行钻探验证实现找矿突破。荣那矿床勘查过程中的理论思考,区域-矿田物化探异常的综合分析、有效方法的投入和验证工程的部署充分体现了科学研究与生产的有机结合。 相似文献
18.
Lake sediment composition as an indicator of mineralization within the catchment area has found widespread application in recent years, particularly in Canada. Results have indicated, however, the existence of varying relationships between lake sediment composition and mineralization resulting from local features of the limnological environment. Accordingly it was considered appropriate to examine the nature of metal transport in the lake and stream environment, the partitioning of metal between the stream waters and stream sediments and between lake waters and lake sediments to obtain some understanding of the factors that affect the lake sediment-mineralization relationship. This investigation was carried out over an area containing Pb-Zn occurrences of supposed “Mississippi-Valley type” in Grenville and Paleozoic bedrock in southeastern Ontario.The headwater drainage systems comprise active streams, swamps, beaver ponds and small lake-bog systems giving way downstream to open lakes. The beaver swamps and seasonal swamps act as drainage sinks for metals, restricting the extent of geochemical dispersion in drainage systems adjacent to mineralization. Selective extraction analysis of bog, stream and lake sediments indicates that metals are preferentially concentrated with amorphous iron oxides, which readily adsorb and complex lead and zinc and are stable in the alkaline environment common in swamps adjacent to carbonate-hosted lead-zinc mineralization. The accumulation of lead and zinc with amorphous iron oxides combined with the adsorbing and chelating action of organic matter on lead and zinc makes organic-rich sediments from these small swampy areas an excellent sample medium for reflecting local mineralization. Down drainage anomalies of these elements can be accentuated by selective analysis for the amorphous iron oxide-held metal, involving selective extraction techniques.In contrast, within larger lake systems, the analysis of water samples indicates that geochemical dispersion in surface waters in the high pH environment (pH = 8.0) associated with the carbonate-hosted lead-zinc deposits is extremely restricted. In this environment, anomalous metal contents in lake water were not evident in lakes adjacent to mineralization, while anomalous lake sediment compositions exist only in lakes immediately adjacent to Pb-Zn mineralization and do not extend down the drainage system. The restricted dispersion necessitates basing geochemical reconnaissance surveys on collection and analysis of samples from the headwater organic-rich swamps at a higher sample density and resulting higher cost than in areas where a lower sample density is acceptable due to a wider dispersion. 相似文献
19.
The water system in a rural area of Lanmuchang in Southwest Guizhou is facing a risk of thallium (Tl) contamination due to Tl mineralization around the area. The major trace elements and Tl in the water system are studied to understand the hydrogeochemical processes of Tl constrained by Tl mineralization. The results showed that the dispersion pattern of Tl follows a descending order in concentration from mine groundwater (deep groundwater) →stream water→shallow groundwater→background water, reflecting the impact of Tl mineralization on the hydrogeochemical composition. Tl concentrations in stream water in both regimes are remarkably higher (2-30 fold) downstream than up- and mid-streams, probably caused by the unidentified discharge of deep groundwater. Low Tl levels are detected in the current drinking water, however, the highly elevated Tl in stream water and ground water may pose a potential environmental risk through daily washing and agricultural irrigation. This study suggests that human activities, such as agricultural irrigation, could intensify the environmental risk of Tl. 相似文献
20.
河南卢氏县杜关地区地球化学异常及找矿效果 总被引：3，自引：4，他引：3
在河南卢氏县杜关地区 1:5万水系沉积物测量的基础上,对测区内元素分布规律进行了系统阐述,指明了区内的主要成矿元素及其富集层位,指出了后瑶峪异常是以铅银锌金为主的矿致异常,应加大查证力度,寻找铅银矿(化)体。 相似文献