Investigating the spatial distribution of antimony geochemical anomalies located in the Yunnan-Guizhou-Guangxi region,China

The Yunnan-Guizhou-Guangxi region is well known for its abundant mineral resources, and low-temperature hydrothermal mineralization represented by the elemental association of gold, arsenic, antimony and mercury is widely developed there. Many studies on the geological-geochemical characteristics of gold have been conducted, but a comprehensive understanding of the antimony geochemical pattern is still lacking. This paper studied the Sb distribution characteristics and the cause of geochemical anomalies based on the geochemical data of stream sediments and rocks in the study area. In addition, the geochemical data of Au, As, Sb and Hg were centered and log-ratio transformed to eliminate the closure effect, and then random forest regression (RFR) with Au, As and Hg as the characteristic variables was used to investigate the ore-related geochemical anomalies of Sb. Seven geochemical provinces were delineated from the original geochemical data, and they are not entirely consistent with the known deposits. Sb moves from the rocks to the stream sediments during weathering. The variation trend in the Sb background values in stream sediments in each tectonic unit is consistent with that in the rocks themselves, implying that Sb in the stream sediments is inherited from the background rocks. The distributions of Sb predicted by RFR are similar to the distribution pattern of Sb in stream sediments. Of the three elements considered, the influence of As on the variations in the Sb geochemical background is the greatest, followed by Au and then Hg. The geochemical anomalies extracted by the residuals produced in this algorithm are consistent with where the known Sb metallogenic district is located, indicating that this method of recognizing geochemical anomalies is feasible and effective and has theoretical and practical significance.     

河北省金的矿源层和地球化学块体

以区域化探岩石和水系沉积物测量成果为依据,讨论河北省范围内Au矿源层的地球化学判别、岩浆热液型金矿成矿过程的地球化学推导、Au的地球化学块体以及水系沉积物区域地球化学异常特征等问题.地层标准剖面和典型侵入体系统的岩石地球化学调查表明,在Au矿源层和非矿源层之间,w(Au)差异很小,以其作为判别标准是不可行的,但H2O ,CO2,S,Cl,F,Hg等组分却存在显著差异,据此提出一个新的矿源层--中新元古界碳酸盐岩.Au的区域地球化学背景研究显示,密云-青龙、怀安-崇礼-赤城、平泉和阜平-赞皇等地区存在着地球化学块体,而水系沉积物地球化学异常分布与这些块体基本一致,相互对应.     

Application of singularity mapping technique to identify local anomalies using stream sediment geochemical data,a case study from Gangdese,Tibet, western China

Identifying geochemical anomalies from background is a fundamental task in exploration geochemistry. The Gangdese mineral district in western China has complex geochemical surface expression due to complex geological background and was chosen as a study area for recognition of the spatial distribution of geochemical elements and separating anomalies from background using stream sediment geochemical data. The results illustrate that weak anomalies are hidden within the strong variance of background and are not well identified by means of inverse distance weighted; neither are they clearly identified by the C–A method if this method is applied to the whole study area. On the other hand, singularity values provide new information that complements use of original concentration values and can quantify the properties of enrichment and depletion caused by mineralization. In general, producing maps of singularities can help to identify relatively weak metal concentration anomalies in complex geological regions. Application of singularity mapping technique in Gangdese district shows local anomalies of Cu are not only directly associated with known deposits in the central part of the study area, but also with E–W and N–E oriented faults in the north of the study area. Both types of anomalies should be further investigated for undiscovered Cu mineral deposits.     

The identification of various types of geochemical stream sediment anomalies in Northern Ireland

A regional geochemical stream sediment survey of part of Northern Ireland led to the recognition of three types of base metal anomaly of exploration interest. These were significant anomalies of both elastic and hydromorphic origin, and non-significant hydromorphic anomalies in several upland areas. The significant anomalies are derived from Pb-Zn-Cu mineralization, whereas the non-significant anomalies are due to the leaching of Zn and other metals from acidic and/or gleyed soils and subsequent concentration in stream channels by coprecipitation with manganese oxides. Significant hydromorphic anomalies can be identified on the basis of abnormal Zn/Mn ratios and significant elastic anomalies on the basis of anomalous Pb contents. It is of the utmost importance to distinguish the dispersion mechanisms. Regional variations in bedrock geochemistry may only be identified when consideration is given to local dispersion mechanisms and account taken of the effects of variations in the surface environment on stream sediment composition. Changes in vegetation and land use may lead to rapid alterations in the nature of the dominant dispersion mechanisms.     

俄罗斯雅库特地区拿垦金伯利岩矿区地球化学特征

通过对俄罗斯雅库特地区拿垦金伯利岩矿区的水系沉积物、土壤、钻孔岩心进行不同规模的地球化学测量,根据区内圆形构造及金伯利岩指示元素Cr、Co、Sr、Zr、Y的分布特征圈出金伯利岩指示元素次生晕异常,证实了地球化学方法寻找深层隐伏金伯利岩管的可行性。     

Enzyme leach anomalies associated with deep Mississippi Valley-type zinc ore bodies at the Elmwood Mine, Tennessee

Deeply buried Mississippi Valley-type deposits that have been or are currently being mined in North America were initially discovered by drilling. Conventional geochemical methods are ineffective for detecting these ‘blind' deposits when they occur deep within sequences of stable-platform carbonates and shales. The ‘enzyme' leach is a selective analytical technique for determining trace elements associated with amorphous Mn oxide coatings in soils. In many areas of the world, the enzyme leach method is useful for detecting low-level geochemical anomalies in soils, which are associated with blind mineral deposits. Enzyme leach analysis of soils, collected at the Elmwood Mine, Tennessee, revealed high-contrast anomalies over ore bodies 370 m below the surface. In areas where the soils are in chemical equilibrium, ‘combination' anomalies occur over Zn ore bodies. These are characterized by asymmetrical halogen halos which occur around a halogen ‘central low'. Commodity metals (Zn and Pb) and trace elements associated with the ore (Cd, Ba, and Mn) form apical anomalies, which occur over the ore bodies and within the halogen halo. Under most circumstances, agricultural practices do not affect enzyme leach results. However, agricultural activity in central Tennessee appears to have altered the proportion of amorphous Mn oxides in the soils in some locations. Where the MnO₂-form equilibrium of the soil has been disturbed, enzyme leach data are erratic. In the one instance where this was encountered, ratioing the data to Mn reveals anomalies which bracket the blind ore bodies.     

The mineralized veins and the impact of old mine workings on the environment at Segura, central Portugal

At Segura, granitic pegmatite veins with cassiterite and lepidolite, hydrothermal Sn–W quartz veins and Ba–Pb–Zn quartz veins intruded the Cambrian schist–metagraywacke complex and Hercynian granites. Cassiterite from Sn–W quartz veins is richer in Ti and poorer in Nb and Nb+Ta than cassiterite from granitic pegmatite. Wolframite from Sn–W quartz veins is enriched in ferberite component. The Sn–W quartz veins contain pyrrhotite, arsenopyrite, sphalerite, chalcopyrite, stannite, matildite and schapbachite and the Ba–Pb–Zn quartz veins have cobaltite, pyrite, sphalerite, chalcopyrite, galena and barite, which were analyzed by electron microprobe. The presently abandoned mining area was exploited for Sn, W, Ba and Pb until 1953. Stream sediments and soils have higher concentrations of metals than parent granites and schists. Sn, W, B, As and Cu anomalies found in stream sediments and soils are associated with Sn–W quartz veins, while Ba, Pb and Zn anomalies in stream sediments and soils are related to Ba–Pb–Zn quartz veins. Sn, W, B, As, Cu, Ba, Pb and Zn anomalies in stream sediments and soils are also related to the respective old mining activities, which increased the mobility of trace metals from mineralized veins to soils, stream sediments and waters. Stream sediments and soils are sinks of trace elements, which depend on their contents in mineralized veins and weathering processes, but Sn, W and B depend mainly on a mechanic process. Soils must not be used for agriculture and human residence due to their Sn, B, As and Ba contents. Waters associated with mineralized veins were analyzed by flame atomic absorption spectroscopy (FAAS) and ICP-AES have high As, Fe and Mn and should not be used for human consumption and agriculture activities. The highest As values in waters were all related to Sn–W quartz veins and the highest Fe and Mn values were associated with the Ba–Pb–Zn quartz veins. No significant acid drainage was found associated with the old mine workings.     

甘肃小柳沟铜钨多金属矿床地球化学异常特征及找矿标志

阐述了小柳沟铜钨多金属矿床的区域地质和区域地球化学概况，并分析了该区的成矿地质条件及地球化学演化特征。在研究了1：10万分散流普查结果的基础上，采用1：2．5万沟系次生晕普查方法，获得了Cu、Mo、Ag、Pb、Zn等元素综合异常，通过验证表明，Cu、Mo异常的浓集中心与铜钼矿体位置一致。又通过原生晕普查，分析了各元素的岩石地球化学分布特征。同时证实了沟系次生晕与原生晕具有同样的找矿效果。因而，提出相关的地质、地球化学找矿(分散流、沟系次生晕、原生晕)标志。     

Incorporation of principal component analysis,geostatistical interpolation approaches and frequency-space-based models for portraying the Cu-Au geochemical prospects in the Feizabad district,NW Iran

Delineation of mineralization-related geochemical anomalies of stream sediment data is an essential stage in regional geochemical exploration. In this study, principal component analysis (PCA) was applied to 12 selected elements to acquire a multi-element geochemical signature associated with Cu-Au mineralization in Feizabad district, NE Iran. The spatial distribution of enhanced multi-element geochemical signature of the second component (PC2) was modeled by different geostatistical procedures including variogram calculation, ordinary kriging (OK) and inverse distance weighting (IDW) interpolation techniques. Concentration-area (C-A) fractal and U-spatial statistics models were then applied to the continuous-value interpolated models for delineation of geochemical anomalies. Quantitative comparison of results based on the known mineral occurrences in the study area was carried out using normalized density index and success-rate curves. All generated models represent a high positive relation with known Cu (±Au) deposits in the study area, although, comparison of the results revealed that the OK-based U-spatial statistics model was superior to the rest of models. Besides, the low, moderate and high-intensity anomalies are spatially associated with geological-structural features in the study area.     

Fractionation characteristics of rare earth elements (REEs) linked with secondary Fe,Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements (REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs (La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs (LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs (HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs. The substantial fractions of REEs in soils extracted by oxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile (10 %–30 %), which were similar to the mass fraction of Fe (10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.     

贵州西部红岩地区水系沉积物中Pt、Pd地球化学异常的识别及推断解释

与基性-超基性岩相比,我国的峨 眉山玄武岩具有高含量的Pt、Pd地球化学背景。从峨眉山玄武岩分布区分辨出与基性、超基性侵入岩有关的Pt、Pd地球化学异常,是我国Pt、Pd找矿获得重大突破的关键技术。在贵州西部开展的1∶5万 水系沉积物测量显示,采用岩石背景衬值法可有效区分岩性和矿致Pt、Pd异常。在红岩村附近茅口组灰岩与玄武岩接触带及北东向断层的复合部位圈出了浓度分度清晰的As、Sb、Hg、Pb、Cr、Ni、Pt、 Pd组合异常,推测在该组合异常下方可能存在一个赋存有Pt、Pd矿的隐伏基性-超基性含矿岩体(脉)。     

四川杨柳坪Cu-Ni-PGE矿田区域地球化学异常特征

在杨柳坪Cu-Ni-PGE矿田进行的1:20万水系沉积物测量表明,该矿床区域地球化学异常的指示元素有:Pt、Pd、Cr、Ni、Cu、Co、Ag、Cd、Sb、Pb和Zn,异常具有空间分带特征,即:从矿床向外的异常元素依次为Pd、Pt-Cr、Ni-Co、Cu-Cd、Ag-Zn-Pb、Sb.因此在筛选1:20万区域化探异常时,不但要考虑成矿元素的异常强度和规模,而且还要考虑其它指示元素的异常强度和规模.同时也说明1:20万水系沉积物测量可作为铂矿区域普查的有效方法.     

Shawinigan nickel-copper property — A case history of a reconnaissance geochemical discovery in the Grenville Province of Quebec,Canada

Study of an area in the southern Grenville of Quebec, by a stream sediment reconnaissance survey, outlined a previously unknown nickel-copper occurrence. Both reconnaissance and detail soil surveys were employed to define the sources of the stream sediment anomalies. A rock geochemical survey was carried out along with the detail soil survey. Some of the soil and rock geochemical anomalies were drilled and in all cases low-grade nickel-copper mineralization was encountered.     

地球化学勘查快速圈定找矿靶区——以黑龙江省黑河市大新屯锑-金矿床的发现为例

黑河市大新屯锑-金矿床位于大兴安岭成矿带东北部,区内构造、岩浆活动频繁.1∶5万水系沉积物Sb、Au、Hg异常强度较高,规模较大,是金及多金属成矿有利部位.为了对区内1∶5万水系沉积物异常进行评价,选定了规模最大的新07Hs-35异常,利用土壤地球化学测量工作方法对异常进一步查证.经土壤地球化学测量工作后圈定Sb、Au、Hg、Ag、As、W土壤地球化学异常多处,以Sb、Hg、Au异常为主,各元素异常浓集中心吻合较好.因此利用槽探工程对圈定的土壤地球化学异常进行了验证,发现了锑-金矿体,从而确定了大新屯锑-金矿找矿靶区,说明地球化学勘查快速确定找矿靶区是成功的.     

吉林省敦化尔站矿区地球化学异常与钼矿体的相关性分析北大核心CSCD

吉林省敦化尔站矿区位于吉黑东部多金属成矿带中南部,以往资料表明有Mo、Cu等元素地球化学异常和斑岩体存在。为查明该区成矿条件,明确勘探思路,开展了水系沉积物、土壤元素地球化学和地物化综合剖面测量工作。通过对各元素分布、相关性和异常特征研究,发现水系和土壤地球化学异常具有较好重现性,R型聚类分析表明Mo与As、W元素相关性较好,主成矿元素为Mo元素,在地球化学高异常和低阻高极化率区域进行异常查证,发现钼矿体6条。钼矿体产于晚二叠世蚀变似斑状二长花岗岩体及其与围岩接触带,主要受北东向构造带控制,Mo和As等元素地球化学异常与矿体和蚀变带的辉钼矿、黄铁矿等关系密切。综合分析尔站矿区成矿地质条件,在已发现矿体北东和南东圈定靶区2个,区域上含前寒武系残片呈北东向展布的晚古生代花岗岩区是重点找矿地段。     

青海省玛沁县友后青地区钴铜矿化带成矿地质特征及找矿前景

青海玛沁县友后青地区大地构造位置处于阿尼玛卿缝合带内,在友后清地区发现了与基性-超基性岩体关系密切的钴铜矿化带。本文主要分析了友后青地区钴铜矿化带的成矿地质特征,认为华力西-印支期NW-NWW向的深大断裂控制着钴铜成矿作用。高精度磁测显示,区内有一条近NWW走向的磁异常带,异常强度中等偏高,呈串珠状分布。水系沉积物测量表明,以镍钴铬为主的多金属综合异常规模大,元素组合齐全,镍钴铬元素异常套合好。水系沉积物地球化学异常与高精度磁测异常可以很好的叠合在一起,在空间上与基性-超基性岩关系密切。沿NW-NWW向断裂带,与基性-超基性岩叠合较好的物化探异常区是该地区寻找钴铜矿的有利地段。     

Separation of a geochemical anomaly from background by fractal and U-statistic methods,a case study: Khooni district,Central Iran

Separation of geochemical anomalies from background are one of the important steps in mineral exploration. The Khooni mineral district (Central Iran) has complex geochemical surface expression due to a complex geological background. This region was chosen as a study area for recognition of the spatial distribution of geochemical elements and separating anomalies from background using stream sediment geochemical data. In the past decades, geochemical anomalies have been identified by means of various methods. Some of these separation methods include: statistical analysis methods, spatial statistical methods and fractal and multi-fractal methods. In this article, two efficient methods, i.e. U-statistics and the fractal concentration-area for separation and detection of anomalous areas of the background were used. The U spatial statistic method is a weighted mean, which considers sampling point positions and their spatial relation in the estimation of anomaly location. Also, fractal and multi-fractal models have also been applied to separate anomalies from background values. In this paper, the concentration–area model (C–A) was suggested to separate the anomaly of background. For this purpose, about 256 stream sediment samples were collected and analyzed. Then anomaly maps of elements were generated based on U spatial statistics and the C-A fractal methods for Au, As and Sb elements. According to obtained results, the U-statistics method performed better than C-A method. Because the comparisons of the known deposits and occurrences against the anomalous area created using thresholds from U-statistics and C-A method show that the spatial U-statistics method hits all of 3 known deposits and occurrences, the C-A fractal method hits 1 and fails 2. In addition, the results showed that these methods with regard to spatial distribution and variability within neighboring samples, in addition to concentration value frequency distributions and correlation coefficients, have more accurate results than the traditional approaches.     

地球化学异常识别的两种机器学习算法之比较

在Sklearn的Python语言代码基础上,开发了基于孤独森林和一类支持向量机的多元地球化学异常识别方法程序。选择吉林省和龙地区为实验区,从1∶5万水系沉积物资料中提取地球化学异常。把实验区已知矿点的空间分布位置作为"地真"数据,绘制两种机器学习算法的ROC曲线并计算AUC值,用来对比两种方法的多元地球化学异常识别效果。研究结果表明:两种机器学习算法都能够有效识别多元地球化学异常,所提取的多元地球化学异常与已知矿点具有显著的空间关联性;孤独森林算法在数据处理耗时和多元地球化学异常识别效果方面略优于一类支持向量机。     

铂矿化探:取子样误差与控制方法

通过对颗粒铂分布与取子样误差关系的讨论 ,发现在铂矿地球化学勘查中 ,铂分析的取子样误差主要出现在铂异常的查证和异常源追踪阶段 ,导致误差的主要因素是随着与矿床或矿体的不断接近 ,样品中铂含量迅速增高 ,可能出现铂的颗粒效应。为了使铂分析的误差控制在 5 0 %之内 ,建议在铂矿地球化学勘查的不同阶段 ,采取不同的子样量分析铂。在区域化探阶段 ,大多数样品仍可采用取 1 0 g子样分析铂 ;而在异常追踪和查证阶段 ,由于样品中的铂含量往往大于 1 0ng/ g ,土壤、水系沉积物样品中颗粒铂粒径通常为 5～ 2 0 μm ,故建议取 2 0 g子样分析可保证大多数样品的分析误差控制在 5 0 %之内。文献中报道的取 5g、1 g样品获得的铂分析数据 ,使用时应慎重     

区域化探扫面资料在农业及环境中的应用

本文采用了分析对比的方法将河北省1:20万青龙幅和山海关幅的区域地球化学资料应用于农业及环境问题的研究。通过对研究区岩石、土壤、水系沉积物中元素分布特征的比较,表明该区水系沉积物中元素含量能够在区域上反映土壤中元素含量的变化趋势。将历年来农作物产量及疾病死亡率分布与地球化学元素分布进行对比,发现有一定的关系。并发现该区大面积缺锌、钼、铜元素,影响了某些农作物产量的增长。还发现了环境中钼元素的分布对食道癌的影响,铬元素的分布对高血压、糖尿病的影响。文中还提出了潘家口水库上游的铬、砷、铅异常的潜在威胁。根据上述结果,初步确定了各元素在该区的正常、过量及缺乏限,并尝试性地编制了标有“缺乏区”“潜在缺乏区”“潜在过剩区”的锌、铜、钴、钼、铬元素的环境地球化学图。