蒙特卡洛模拟在全国矿产资源潜力评价中的应用

蒙特卡洛模拟是一种通过设定随机过程,反复生成时间序列,计算参数估计量和统计量,进而研究其分布特征的方法.在矿产资源评价中的应用是以已知矿床的资源量分布特征通过抽样模拟来对目标区的资源量进行预测,前提条件是目标区域与已知矿床具有相同的矿床类型.本文讨论了蒙特卡洛模拟的原理,并以全国矿产资源潜力评价中新疆海相火山型铁矿为例进行了说明,并介绍了新疆海相火山型铁矿品位吨位模型的建立方法,对几种不同的预测方法预测的资源量进行了分析比较.蒙特卡洛方法不仅可以对资源量进行模拟和预测,在对一些难以建立精确数学模型的预测参数,比如可信度估计中,可以用蒙特卡洛法进行模拟,具有合理的统计理论效果.     

矿产预测评价中不确定性传播模型

矿产预测与评价是是由多个阶段组成的系统工程,包括数据收集,资料整理,信息提取,信息综合,预测评价、成果表达等.由于地质的复杂性和变化多样性及人类认识的不完备性致使矿产预测与评价的每一个阶段都包含了一定的不确定性,且前一阶段的不确定性会传播给后一阶段,从而导致相当数量的不确定性积累与传播.本文简要分析了矿产预测与评价不确定性的主要来源,给出矿产预测与评价的不确定性表达模型,研究了矿产预测与评价不确定性的合成算法和传播算法.     

辽东地区金矿床成因与资源潜力

华北东部广泛分布着与晚中生代克拉通破坏相关的金矿床,但不同地区金矿床在研究程度、成矿特征、探明储量等方面存在显著差异.华北东部的辽东具有与胶东相似的区域地质特征,并共同经历了晚中生代克拉通破坏作用,但其金成矿的理论研究和探明的黄金资源量却存在巨大差异.本文在分析研究辽东区域地质、中生代岩浆-构造演化和矿床地质基础上,通过深部-浅部综合地球物理探测和大数据AI资源量预测,提出了辽东晚中生代金元素富集主体来自于克拉通破坏诱发的幔源熔流体,金矿床主要受北东-北北东向断裂控制,金矿类型以破碎带蚀变岩型和含硫化物石英脉型为主.明确了鸭绿江主断裂带及相关的次级断裂、已知矿集区外围与深部是未来金矿资源勘查的重要区域,预测鸭绿江成矿带黄金资源潜力巨大,具备新增数千吨级黄金资源的潜力.     

解读青海首例岩浆熔离型铜镍硫化物矿床——访青海省第五地质矿产勘查院院长李世金

正新年伊始,青海找矿进展不断传来喜讯,据了解,青海省地矿局第五地质矿产勘查院经过两年的勘查,在格尔木市乌图美仁乡地区发现一处高富品位的大型铜镍钴矿,这是青海在东昆仑发现的首例岩浆熔离型铜镍硫化物矿床,目前已探获资源量镍55万吨、钴2万吨、铜5.21万吨,潜在经济价值600亿元以上。那么,岩浆熔离型铜镍硫化物矿床的发现过程是怎样的?矿区的找矿     

Hopfield神经网络在矿产资源评价中的应用——以新疆东天山铜镍硫化物矿床为例

矿产资源勘查与评价中的某些地质异常信息常常具有非线性的动力学特性,利用人工神经网络良好的非线性特征可在矿产预测领域发挥一定优势.本文探讨了Hopfield神经网络的原理,利用Lyapunov函数的正交化权值设计,可以保证Hopfield网络能量递减并收敛至稳定平衡点,实现联想记忆和分类的功能.本次研究以新疆东天山地区岩浆型铜镍硫化物矿床为例,建立预测模型,提取预测要素,构造网络的平衡点,利用Hopfield神经网络对该类矿产远景区进行级别分类并输出,根据分类结果并综合区域地质和物化探信息在东天山地区划分出了两个铜镍矿的重点勘查区.对比证据权法的分类结果,两者A级远景区部分接近或者重合,并符合一定地质意义,可为矿产预测人员提供最优决策.将非线性的神经网络方法和传统的线性方法进行结合,对比研究,相互验证,可在一定程度上提高矿产预测的精确度和可信度.     

MapInfo综合信息矿产资源评价系统及应用

矿产资源预测是综合地学信息，进行优选靶区的有效手段之一.本文以MapInfo为平台，VC为二次开发工具，以综合信息矿产预测理论与方法为指导建立了MapInfo综合信息矿产资源评价系统.文中对MapInfo综合信息矿产资源评价系统的流程进行较为详细的论述，并以陕南地区金矿为例进行了综合评价.评价结果与其它系统相似或相近，证明该系统的有效性，为矿产预测提供了又一种技术方法.     

基于Boltzmann机的矿产靶区预测

矿产靶区预测是一种从统计单元集合中识别找矿靶区的非线性模式识别过程,可以利用Boltzmann机能够对外部刺激进行编码和重建的功能,实现基于Boltzmann机的矿产靶区非线性统计预测过程.鉴于此,笔者定义了面向矿产靶区预测的三层Boltzmann机模型,模型输入层神经元数目等于找矿证据数目,输出层只有一个神经元,隐藏层神经元数目由用户根据矿产靶区预测的精度要求确定;模型应用Hebbian编码和模拟退火算法相结合的随机学习算法进行训练,根据学习训练后模型输入层与隐藏层神经元之间的连接权确定找矿证据的权系数;根据证据权系数和统计单元证据组合特征计算单元成矿有利度,圈定找矿靶区.在GDAL数字图像输入输出函数库基础上,用VC++语言开发了面向栅格数据的矿产靶区预测Boltzmann机算法程序并应用于新疆阿勒泰地区的矿产靶区预测研究.结果表明,Boltzmann机模型预测的统计单元成矿有利度能够正确反映研究区已知矿床(点)的空间分布规律,因此,基于Boltzmann机的矿产靶区非线性统计预测模型是有效的.     

前兆异常与地震相关性评价中的不确定性--VAN方法讨论引起的思考

从国际地震界关于VAN方法预测效能引发的大辩论出发,讨论了在前兆异常与地震相关性评价中的不确定性问题.在对前兆与地震相关性进行统计检验时,涉及到对地震孕育、发展和前兆基础的理论研究及认识,以及将预测转换成具体操作程序时遇到的许多不确定性问题.文中对这些不确定性逐一进行了介绍."地震界需要一套评估地震预报方法的基本方案"是在辩论后达成的共识,亦应成为中国学者的一项重要研究内容.     

我国富碱火成岩及有关的大型-超大型金铜矿床成矿作用

我国富碱火成岩呈带状分布,长达数百甚至数千公里,已发现有15条岩带包括了世界上已发现的绝大部分富碱火成岩类型.在我国与该岩类有关形成了东坪、归来庄、玉龙等为代表的大型超大型Au,Cu矿床或矿集区.富碱火成岩对Au、Cu的成矿控制作用主要为两方面,一是矿床直接产于富碱火成岩中,二是富碱火成岩浆活动参与成矿作用.地幔交代富集、强烈的壳幔相互作用、岩石圈结构的剧烈变化和区域性构造格架的挤压向伸展、拉张的重大转折以及低硫、高氧逸度和富挥发分等因素控制了富碱火成岩的形成及相关成矿作用.     

地震灾害损失预测中的不确定性研究回顾

本文概述了对象研究的不确定性类型、研究方法,着重描述了震害预测过程中存在的不确定性及其研究进展,目前应用于震害预测不确定性研究的主要方法,并对当前震害预测中存在的主要问题进行了初步总结与讨论。     

A comparative study of fuzzy weights of evidence and random forests for mapping mineral prospectivity for skarn-type Fe deposits in the southwestern Fujian metallogenic belt,China

Recent studies have pointed out that the widespread iron deposits in southwestern Fujian metallogenic belt (SFMB) (China) are skarn-type deposits associated with the Yanshanian granites. There is still excellent potential for mineral exploration because large areas in this belt are covered by forest. A new predictive model for mapping skarn-type Fe deposit prospectivity in this belt was developed and focused on in this study, using five criteria as evidence: (1) the contact zones of Yanshanian granites (GRANITE); (2) the contact zones within the late Paleozoic marine sedimentary rocks and the carbonate formations (FORMATION); (3) the NE-NNE-trending faults (FAULT); (4) the zones of skarn alterations (SKARN); and (5) the aeromagnetic anomaly (AEROMAGNETIC). The fuzzy weights of evidence (FWofE) method, developed from the classical weights of evidence (WofE) and based on fuzzy sets and fuzzy probabilities, could provide smaller variances and more accurate posterior probabilities and could effectively minimize the uncertainty caused by omitted or wrongly assigned data and be more flexible than the WofE. It is an efficient and widely used method for mineral potential mapping. Random forests (RF) is a new and useful method for data-driven predictive mapping of mineral prospectivity method, and needs further scrutiny. Both prospectivity results respectively using the FWofE and RF methods reveal that the prediction model for the skarn-type Fe deposits in the SFMB is successful and efficient. Both methods suggested that the GRANITE and FORMATION are the most valuable evidence maps, followed by SKARN, AEROMAGNETIC, and FAULT. This is coincident with the skarn-type Fe deposit mineral model in the SFMB. The unstable performance experienced when FORMATION was omitted might indicate that the highest uncertainty and risk in follow-up exploration is related to the sequences. In addition, the performance of the RF method for the skarn-type Fe deposits prospectivity in the SFMB is better than the FWofE; therefore, it could be used to guide further exploration of skarn-type Fe prospects in the SFMB.     

Ridge subduction and porphyry copper-gold mineralization:An overview

Many large porphyry Cu-Au deposits are connected to adakitic rocks known to be closely associated with ridge subduction. For example, there are several subducting ridges along the east Pacific margin, e.g., in Chile, Peru, and South America, most of which are associated with large porphyry Cu-Au deposits. In contrast, there are much fewer ridge subductions on the west Pacific margin and porphyry Cu-Au deposits are much less there, both in terms of tonnage and the number of deposits. Given that Cu and Au are...     

遥感技术在我国矿产资源预测评价中的应用

遥感技术作为有效的辅助手段应用于矿产资源预测已有多年历史.随着遥感技术的发展,遥感技术的作用将会变得越来越重要.本文综合叙述了遥感技术在资源预测评价中的应用现状以及应用方法,并对将来遥感技术在资源预测中的应用前景进行了展望.     

金属矿产勘查技术发展现状与思考

近年来，以寻找金属矿产为目的发愤卢业的勘查新技术可概括为：（1）以寻找隐伏矿为目标的覆盖区地球物理勘查技术，其中包括“三维地震”和“高光谱遥感”技术；（2）地球化学勘查新技术，其中包括“深穿透地球化学技术”、“地球化学信息的综合解释和地球化学填图技术”；（3）“找矿信息提取和综合”技术等。限于篇幅，本文仅对地球化学勘查新技术的研究现状进行了分析，同时对下列问题进行了思考：（1）在一个地区开展地球化学找矿工作首先要确立合适的取样介质，取样介质的立应以查明成矿成晕元素的形成机制和赋存状态为基础；（2）加强不同景观条件下不同矿种和不同矿床类型的异常特征和异常模式研究，建立区分矿异常和非矿异常的模式识别模型；（3）加强不同景观地质条件下，不同勘查尺度的地球化学填图技术研究，以实现迅速掌握全局，逐步缩小靶区的找矿战略；（4）加强地球化学信息与地质、地球物理和遥感信息相结合的信息综合技术的研究，应用综合信息定量圈定和评价找矿靶区，减少矿产勘查的不确定性。     

Geological and geophysical data integration for delimitation of mineralized areas in a supergene manganese deposits

Geophysical methods are widely used in mineral exploration. This paper discusses the results of geological and geophysical studies in supergene manganese deposits of southern Brazil. Mineralized zones as described in geological surveys were characterized as of low resistivity (20Ω.m) and high chargeability (30ms), pattern found also in oxides and sulfite mineral deposits. Pseudo-3D modeling of geophysical data allowed mapping at several depths. A relationship between high chargeability and low resistivity may define a pattern for high grade gonditic manganese ore. Large areas of high chargeability and high resistivity may result in accumulation of manganese and iron hydroxides, due to weathering of the gonditic ore, dissolution, percolation and precipitation.     

论发震构造特性在潜在震源区参数确定中的应用

发震构造特性是潜在震源区划分及其地震年发生率确定的重要依据。潜在震源区除了反映“未来具有发生破坏性地震的地区”的内涵外,还应反映高震级档地震具有相似复发特征的涵义。由于在地震活动性参数统计单元内,有一些具有不同本底地震的活动构造块体,为更好地反映地震活动的空间不均匀性,考虑潜在震源区的三级划分是有必要的。通过分析潜在震源区内高震级档地震的复发特征,计算预测时段内潜在震源区的高震级档地震的发震概率,采用预测时段内概率等效转换获得地震年平均发生率的方法,有助于在中国地震危险性分析框架内考虑潜在震源区的强震复发特性。另外,文中还对潜在震源区内特征地震次级震级档频度不足的特性和发震构造上强震非均匀性在地震危险性分析中的应用问题进行了探讨     

Insights From a Multi-Method Recharge Estimation Comparison Study

Although most recharge estimation studies apply multiple methods to identify the possible range in recharge values, many do not distinguish clearly enough between inherent uncertainty of the methods and other factors affecting the results. We investigated the additional value that can be gained from multi-method recharge studies through insights into hydrogeological understanding, in addition to characterizing uncertainty. Nine separate groundwater recharge estimation methods, with a total of 17 variations, were applied at a shallow aquifer in northwest Ethiopia in the context of the potential for shallow groundwater resource development. These gave a wide range of recharge values from 45 to 814 mm/a. Critical assessment indicated that the results depended on what the recharge represents (actual, potential, minimum recharge or change in aquifer storage), and spatial and temporal scales, as well as uncertainties from application of each method. Important insights into the hydrogeological system were gained from this detailed analysis, which also confirmed that the range of values for actual recharge was reduced to around 280-430 mm/a. This study demonstrates that even when assumptions behind methods are violated, as they often are to some degree especially when data are limited, valuable insights into the hydrogeological system can be gained from application of multiple methods.     

Assessing leakage detectability at geologic CO2 sequestration sites using the probabilistic collocation method

We present an efficient methodology for assessing leakage detectability at geologic carbon sequestration sites under parameter uncertainty. Uncertainty quantification (UQ) and risk assessment are integral and, in many countries, mandatory components of geologic carbon sequestration projects. A primary goal of risk assessment is to evaluate leakage potential from anthropogenic and natural features, which constitute one of the greatest threats to the integrity of carbon sequestration repositories. The backbone of our detectability assessment framework is the probability collocation method (PCM), an efficient, nonintrusive, uncertainty-quantification technique that can enable large-scale stochastic simulations that are based on results from only a small number of forward-model runs. The metric for detectability is expressed through an extended signal-to-noise ratio (SNR), which incorporates epistemic uncertainty associated with both reservoir and aquifer parameters. The spatially heterogeneous aquifer hydraulic conductivity is parameterized using Karhunen–Loève (KL) expansion. Our methodology is demonstrated numerically for generating probability maps of pressure anomalies and for calculating SNRs. Results indicate that the likelihood of detecting anomalies depends on the level of uncertainty and location of monitoring wells. A monitoring well located close to leaky locations may not always yield the strongest signal of leakage when the level of uncertainty is high. Therefore, our results highlight the need for closed-loop site characterization, monitoring network design, and leakage source detection.     

ON THE ORIGIN AND INTERPRETATION OF SELF-POTENTIAL ANOMALIES*

The renewed interest in the self-potential method of exploration for mineral deposits gives an understanding of the self-potential mechanism new importance. The cause of SP anomalies in general lies in the interference between simultaneously occurring nonequilibrium phenomena. However, theories of the mechanism of mineral SP anomalies generally relate the SP anomaly to the equilibrium potential of the chemical reaction supposed to occur on the ore body surface. In this paper, I reformulate these equilibrium mechanisms in terms of nonequilibrium thermodynamics. The result is that the SP anomaly depends not on the equilibrium potential alone, but also on the potential resulting from current transferred across the ore body—electrolyte interface. It is not possible to calculate the overpotential theoretically because of the number of complicating factors, and experimental data are not available. This does not imply that SP data are uninterpretable quantitatively. SP data may be interpreted similarly to other potential field data.