Comparing linear and non-linear kriging for grade prediction and ore/waste classification in mineral deposits

Ore/waste classification and economic evaluations of mineral deposits rely on the grade of elements of interest, which must be predicted as accurately as possible to minimise misclassifications. Ordinary kriging is commonly used for such a purpose, but non-linear predictors such as disjunctive kriging may improve the results. In this context, this work presents two case studies, in one of which (gold grades with heavy-tailed distribution) disjunctive kriging outperforms ordinary kriging, while in the other case study (copper grades with a moderately skewed distribution), it turns out to be as accurate as ordinary kriging, although with less conditional bias.     

高砷金精矿硫代硫酸盐浸出试验研究

以某高砷金矿经两次粗选—两次精选—四次扫选选别得到的含金24.6g/t的金精矿为原料,采用响应曲面法对该金精矿硫代硫酸盐浸出过程进行优化分析,同时探索了S_2O_3~(2-)、NH_4~+和Cu~(2+)浓度等因素对浸出效果的影响。结果表明,浸出溶液中的S_2O_3~(2-)、NH_4~+和Cu~(2+)浓度对金浸出率的影响程度依次是[S_2O_3~(2-)]>[Cu~(2+)]>[NH_4~+]。在浸出时间4h、浸出温度40℃、矿浆pH值10、搅拌速度300r/min、硫代硫酸钠浓度0.5mol/L、硫酸铵浓度1.0mol/L、铜离子浓度为0.035mol/L条件下可获得最佳的浸出效果,最佳金浸出率为90.28%,可实现该高砷金精矿中金元素的有效回收。研究结果可为解决该类型浮选金精矿浸出方案和高砷金精矿硫代硫酸盐浸金工艺提供参考。     

Giant Mine: Identification of Inflow Water Types and Preliminary Geochemical Monitoring during Reflooding

Abstract:  Between 1948 and 1999, gold ore containing high concentrations of arsenopyrite was mined at the Giant Mine near Yellowknife, Canada. Processing resulted in 215,000 kg of gold and approximately 237,000 tonnes of highly soluble arsenic trioxide, a by-product of the roasting process. The arsenic dust was collected and placed underground in 15 shallow chambers and stopes (within 75m of the surface) with the understanding that the ground would revert to permafrost conditions once mining was completed. Subsequent studies have shown that the ground is unlikely to refreeze naturally; therefore, it has been proposed to actively freeze the arsenic trioxide storage areas to hydraulically isolate them from the post-closure ground water system. However, other arsenic sources (backfilled tailings, etc.) exist deeper in the mine (600 m total depth), so there is a concern that arsenic will leach into the minewater system and ultimately into the environment when the mine is allowed to flood. Therefore, the development and implementation of a remediation plan for the site requires a good understanding of the arsenic distribution and expected release to the mine water. To gain this understanding, a detailed program of surface and underground sampling was carried out to identify or “type” the inflow sources to the mine, and their interaction with arsenic sources both on the surface and within the mine workings. As of July 2005, the mine has been allowed to begin reflooding to reduce pumping costs and remove the need for servicing pumps at the bottom of the mine, thus allowing the main shaft to be taken out of service. Prior to starting reflooding, a multi-level monitoring system was installed in the main shaft and is currently being used to monitor reflooding levels and water chemistry. Samples can be collected from each mine level intersecting the shaft. The system will monitor reflooding rate and test how underground arsenic sources (backfilled tailings, etc.) are affecting water quality in the mine. This geochemical information will be used to assess long-term arsenic loading from sources outside the frozen zone and predict how long mine water treatment will be needed before natural ground water flow can be allowed.     

一种含砷金精矿的生物氧化氰化提金研究

采用两株氧化亚铁硫杆菌对一种含砷金精矿进行了不同充气条件的氧化脱砷和氰化提金试验，结果表明微生物的活性是影响脱砷效果的关键。同时，只有脱砷率超过５０％以后，才能明显改善矿石中金的氰化浸出指标。     

国外某难选金铜矿综合回收选矿试验研究

国外某难选含砷金铜矿采用浮选—氰化联合选别工艺,组合抑制剂抑砷,综合回收了矿石中的铜和金。浮选优先获取了可以直接销售的含砷合格铜金精矿,浮选尾矿氰化浸金补充回收了残留在其中的金,使铜、金综合回收率分别达到了78.73%和94.50%。     

Geostatistics applied to mine waste characterization at Leadville,Colorado, USA

ABSTRACT

This paper will describe the process of identifying lead contaminated soil areas exceeding a certain threshold at a historical mining district using geostatistical tools. For this purpose, lead concentration samples coming from Leadville County, Colorado were chosen as the data sets to be examined. In order to check integrity of data files, posting of the data values at sample locations is performed on each of the four data sets available. Statistical analysis is used for identifying possible different populations within the study area Based on the statistical results, the data sets were subdivided into four different populations as they relate to residential domains. More detail geostatistical analysis of data set representing the City of Leadville domain (CL) is performed Variogram analysis is used to characterize spatial variability on the data sets within CL limits. Generation of variograms for such data sets and identification of their parameters such as sill, nugget, range, and anisotropy ratios is performed. Once these parameters are identified, variogram modeling is accomplished. A significant spatial correlation is found within CL boundaries and two geostatistical estimation techniques named ordinary kriging and indicator kriging are applied to determine level of contamination at unsampled locations exceeding 3500 PPM threshold. Such techniques are tested by cross validation in order to check possible overestimation bias over 3500 PPM threshold. Indicator Kriging was found to be the best estimator which provided the minimum overestimation bias of areas of contamination exceeding 3500 PPM threshold compared with ordinary kriging.     

某富硫高砷尾矿回收金银浮选试验研究

国内某选矿厂的尾矿中含金 0.41g/t,银40.71g/t,同时含有较高的硫和砷。为了探究其中金、银等有价元素回收的可能性,本文进行了较为详细的浮选试验研究。试验考察了金银优先浮选流程、金（银）硫（砷）混和浮选流程以及混浮精矿的硫砷分离,最终获得了含金 1.52g/t,银80.82g/t,硫 41.78%的浮选精矿,金、银、硫回收率分别为66.13%,35.58%和91.29%,实现了综合回收,可为类似矿石的回收利用提供技术参考。     

Environmental occurrence and impacts of arsenic at gold mining sites in the western United States

Arsenic is a common element in the natural environment and is frequently a significant component in gold deposits of the western United States. Such deposits contain various forms of arsenic: arsenides, sulfides, and sulfosalts. Upon weathering such minerals routinely lower the pH of nearby waters, mobilizing arsenic and other metals. Arsenic may also be mobilized in aqueous environments where cyanide has been used to leach gold ores, resulting in high water pH. Incorrect construction of monitoring wells can result in contamination by cement/grout, which may raise pH causing arsenic concentrations to appear inordinately elevated. Concentrations of arsenic toxic to humans and aquatic life have resulted from mining activities in some instances. Hence, regulatory agencies in the U.S. are requiring gold mining companies to comply with very restrictive arsenic standards. The authors of this paper have been involved on many mining projects, mostly in the Western United States, where elevated arsenic content impacted the development of mineral deposits, or created a potential for environmental problems. Several case histories of the pre-mining arsenic content in surface and ground water on gold mining projects throughout western United States and Alaska are presented. The technical aspects of an elevated arsenic content in surface and ground water, mined areas, and waste disposals are discussed. Potential for arsenic contamination of water resources during and after gold mining operations with cyanide heap leach or other gold recovery methods are also presented. Several recommendations for mine operations of how to deal with the problem of elevated arsenic content in pyritic environments are offered.     

国外某难处理高砷金铜矿选冶试验研究

介绍了采用优先选铜—硫砷精矿强化浸金—尾矿氰化工艺方案综合回收了国外某矿石中的金和铜。该矿原矿石含Au3.40g/t、Ag16.9g/t、Cu1.07%、As1.16%、TS5.38%,金、铜矿物嵌布粒度微细,嵌布关系复杂,金分布较为分散,且有很大一部分被硫化物或脉石包裹,砷含量高,属于复杂难处理高砷金铜矿。试验采用石灰+亚硫酸钠组合抑制剂抑砷,优先获得了可以直接销售的合格铜金精矿,采用热压预氧化—氰化法回收硫砷精矿中的金,氰化浸出浮选尾矿中的金,金、铜综合回收率分别达到83.47%和87.20%。     

河南某金矿石金砷浮选分离试验研究

河南某金矿石含金2.00 g/t，含砷1.24%，属高砷难处理金矿石。对该矿石采用石灰控制矿浆pH为抑制砷矿物所需的碱性，同时加入保护剂LA破坏金载体矿物黄铁矿表面因碱性条件而生成的氧化亲水膜，成功实现了金砷浮选分离，闭路试验所得金精矿金品位达68.00 g/t，金回收率达78.43%，砷含量仅为0.37%。机理分析表明，对于金载体矿物是硫矿物的含砷金矿石，由于砷矿物和硫矿物热力学稳定性的差异，在碱性条件下，通过加入保护剂LA破坏硫矿物表面的亲水氧化膜，实现金砷分离在理论是可行的，从而为试验结果提供了理论依据。     

Improvement of cyanidation practice at Goldcorp Red Lake Mine

Goldcorp Red Lake Mine processes a mildly refractory high grade gold ore with 77.8 g/t Au and 1.9% arsenopyrite, 1.7% pyrite and 0.2% pyrrhotite at a grind of 77% −37 microns. A cyanidation study was conducted to determine the necessary retention time of the leach circuit and the optimal gold extraction and cyanide consumption. Results have shown that the gold leaching kinetics could be significantly improved by the addition 100–200 g/t lead nitrate directly in the grinding circuit, followed by a 6 h cyanidation. A 1 month trial indicated a throughput of 810 tpd can be sustained without detrimental effect on gold extraction. However, the mill is currently limited by the underground operation to a throughput ranging from 650 to 700 tpd for a 55 h retention time. In the event of future throughput increase over 810 tpd value, lead nitrate could become an essential part of the leaching efficiency. The experimental work indicated a gold extraction at 87.1–87.4% (tailings ∼9.8 g/t Au) which is similar to plant performance. The associated cyanide consumption was 0.7 kg/t. Gold dissolution can efficiently be conducted at an average cyanide concentration of 400 ppm. Previous control of cyanide concentration in the plant was 700 ppm in the first leach tank to 350 ppm NaCN at the end. Testwork realised in the mill allowed a 32% cyanide reduction predicted by the on-site cyanidation study. The new cyanide concentration is ranging between 500 ppm in the first leach tank and 300 ppm NaCN at the end of the leaching circuit. The cyanide consumption of the plant was reduced from 1.0 to 0.68 kg/t with reduction of effluent treatment costs. Grinding finer (91% −37 microns) slightly increased the gold extraction (tailings lower by 0.4 g/t) but lowers the leaching kinetics, increases cyanide consumption (35%) and the arsenic dissolution.     

菌种活化条件对含砷金矿石生物预氧化的影响

为提高含砷金矿生物预氧化所用细菌的活性,采用经含砷金矿长期驯化的嗜中温混合菌群进行了活化试验,并用活化菌种对山东某含砷金矿石进行了生物预氧化试验。结果表明：以10 g/L的FeSO₄·7H₂O和质量分数为5%的金矿作为混合能源对菌种进行1次活化后,金矿石生物预氧化的脱砷率可达到75.0%;以质量分数为5%的金矿为能源对1次活化菌种进行2次活化后,金矿石生物预氧化的脱砷率可进一步提高到89.0%。     

铜电解精炼液净化脱砷新工艺

电解精炼铜过程中,粗铜中的砷不可避免地溶解到电解液中,进而影响精炼铜效率.由于铜精炼电解液是酸性体系,常用的萃取法和化学沉淀法很难在该环境中取得理想效果.现有电解精炼厂大多选用电沉积法,以牺牲电耗的方式降低电解液中的砷浓度,然而这种方式能耗大、沉积效率低.通过模拟现有电沉积脱砷工艺,发现当铜电解精炼液中铜浓度降至10 ...     

青海某金矿浮选尾矿工艺矿物学研究

青海某金矿石平均含金2.62 g/t、含砷0.28%,为典型的含砷难处理金矿。选矿厂采用"一次粗选、两次精选、两次扫选"浮选工艺,但金的回收率仅为77%左右,损失严重。为了查明金损失原因,提高选矿厂浮选回收率,利用化学多元素分析、光学显微镜、扫描电镜等工艺矿物学研究手段,对青海某金矿选矿厂浮选尾矿进行工艺矿物学研究。结果表明,浮选尾矿含金0.81 g/t,但金的赋存状态较为复杂,主要以极微细粒(粒度0.3~3μm)形式包裹于石英、方解石、钠长石等脉石矿物中,其次是以微细粒(粒度2~6μm)形式包裹于毒砂和斜方砷铁矿中,还可见部分金粒(粒度小于10μm)嵌布于脉石裂隙中。金嵌布粒度极细和包裹金所占比例较高,是选矿回收率不高的主要原因。     

青海某难处理含砷金矿石工艺矿物学研究

青海某难处理含砷金矿矿石性质较为复杂,产出的金精矿金品位及回收率均较低。为充分掌握矿石性质、提高金品位及回收率,利用偏光显微镜、场发射扫描电子显微镜（SEM）等手段对矿石进行了系统 的工艺矿物学研究。结果表明：①不同矿区金品位分布极不均匀,平均Au品位3.0 g/t;矿石中主要金属矿物为黄铁矿,少量闪锌矿和方铅矿以及微量黄铜矿,并且含有少量毒砂,主要非金属矿物为石英和长石,以及 部分绿帘石、透辉石、绢云母、方解石。②矿石中金矿物主要为含量81.58%的银金矿,其余为含量14.80%的自然金与含量3.62%的金银矿;矿石中金矿物颗粒细小,细粒金占93.39%,微粒金占6.64%,最大粒径为31 μ m,最小粒径为2 μm,平均粒径为10 μm;金矿物的赋存状态有包裹金、晶隙金和裂隙金3种,包裹金占79.30%,晶隙金占12.76%,裂隙金占7.94%;金矿物的形态以圆粒状为主,其余为长条状与不规则状。③矿石中 主要载金矿物为黄铁矿和少量毒砂,相比理想黄铁矿中铁含量,矿石中普通黄铁矿与载金黄铁矿中Fe含量分别低2.06个百分点和2.66个百分点,表现出低铁高硫的特征;普通毒砂与载金毒砂中的Fe、As含量相较于理 想含量低,其中普通毒砂Fe、As含量分别低1.65个百分点、3.30个百分点;载金毒砂Fe、As含量分别低0.50个百分点、6.15个百分点,普通毒砂与载金毒砂中S含量分别比理想含量高4.28个百分点和6.65个百分点。④ 矿石中主要载金矿物为黄铁矿,且金的粒度为微细粒,建议通过细磨提高黄铁矿的单体解离度,同时强化黄铁矿的捕收,以进一步增加金的回收率。     

难处理含砷金精矿的生物预氧化—硫脲浸金工艺研究

本文用氧化亚铁硫杆菌（Ｔｈｉｏｂａｃｉｌｕｓｆｅｒｒｏｏｘｉｄａｎｓ）对含砷金精矿进行了氧化预处理脱砷实验，脱砷率达９８％。生物浸渣用ＳＯ２－硫脲浸取体系浸出金，不仅降低了硫脲用量，而且缩短了浸出时间，金的浸出率达９５％以上。该工艺具有广阔的应用前景。     

某高硫含砷碳低品位难处理金矿选矿试验研究

某低品位金矿石原矿含金1.68 g/t,砷0.43%、碳0.40%、硫3.20%,金以显微或次显微形式浸染于毒砂、黄铁矿、褐铁矿中,具有载金矿物粒度细、砷和碳含量高等特点,是典型的低品位含砷碳极难处理 金矿石,严重影响金的浮选指标。为回收利用矿石中的金,分别进行了直接全泥氰化浸出、重选、浮选三种方案对比试验研究。结果表明,直接全泥氰化浸出率仅5%,重选金精矿回收率不足10%,浮选可获得金品位 15.04 g/t、回收率77.13%的金精矿。由于浮选金精矿含砷、碳、硫有害元素均较高,浮选尾矿含金0.42 g/t,损失较高,因此试验采用焙烧预处理以脱除金精矿和尾矿中的有害元素,然后焙砂氰化浸出回收金。最终 试验采用浮选—金精矿焙烧氰化浸出—尾矿焙烧氰化浸出联合工艺,得到金总回收率70.66%的较好指标,有效地回收了矿石中的金。     

青海某金矿矿集区土壤重金属污染评价及综合利用讨论

为研究青海某金矿矿集区土壤重金属污染情况,采集了土壤样品442件,分析了重金属元素(As、Cd、Hg、Pb、Cn、Zn、Cr、Ni)含量,采用内梅罗污染指数法、地累积污染指数法进行评价。结果表明,重金属元素污染轻微,仅As元素产生一定程度的污染,其中内梅罗指数法评价出有69.43%的样品受到As污染,地累积指数法评价出59.24%的样品受砷污染,两种评价结果较为接近。矿集区金矿石中的金属矿物主要为黄铁矿和毒砂,选矿试验发现样品中As含量达到0.38％,超过了伴生组分的评价标准,在后续矿业开发中,加强As元素的综合回收利用,是减少对环境污染的有效方法之一。      

高砷金矿中金的浸出研究

本文比较了不同预处理条件下砷金矿中金的浸出行为，探讨了高砷金矿中砷的脱除效果和影响金的浸出率的原因。研究证实，氨性硫代硫酸钠溶液对高砷金矿中的金具有优异的浸出性能，该方法省去了各种复杂的预处理过程，金的浸出率从常规氰化法的15％提高到约90%。     

中国煤中砷的分布特征

基于中国26个省(直辖市、自治区)、126个矿区、504个煤矿、1119个煤层煤样和商品煤样的系统测试资料,对中国不同成煤时代、不同煤类、不同聚煤区煤中砷含量分布特征进行了研究,并分析了煤中砷分布与灰分、硫分的关系.结果表明,中国煤中砷的加权平均含量为4.09μg/g,算术平均含量为4.61μg/g,低于世界平均水平,也低于美国煤平均水平;中国不同时代、不同煤类、不同聚煤区煤中砷含量分布特征与灰分、硫分分布特征不完全一致,表明除矿物外,成煤期物质供给、煤阶等因素对煤中砷含量富集影响也较大.