This paper advances a new data processing technique-subregion median contrast filtrering method.It uses subregion to simulate spatial variation of the background, calculates critical values of anomalies with EDA technique, and measures the undulation of field values with the contrast as the datum. This technique fairly satisfactorily solves the problem of recognizing weak anomalies, and the preliminary application proves it to be effective.

化探异常下限计算方法在矿产勘查和资源预测中非常重要。传统的计算方法存在依据不充分的问题。这里在研究地球化学场数据分布的基础上，提出了多重含量一频数分形计算方法。研究表明，多重分形异常下限计算方法较之传统的方法具有理论基础扎实、适用性较广的特点。

地球化学元素的异常下限值确定是地球化学中重要的问题之一,目前还没有一个令人满意的具有科学依据的计算方法。传统的化探异常下限值计算是基于元素的地球化学分布呈正态分布或元素含量在空间上呈连续的变化这一假设为基础的,而事实上地球化学元素含量的空间分布是极其复杂的,研究表明,地球化学景观可能是一个具有低维吸引子的混沌系统,元素的地球化学背景值和异常具有各自独立的幂指数关系,由此导致了一种多重分形分布,因而可以利用元素的分形分布求出其异常下限。利用元素的分形分布求异常下限的几种常用方法均是以求取不同尺度r下,对应的N(r)数。如果用手工统计方法计算,计算过程简单但繁琐,地理信息系统(GIS)可以实现图形单元的动态查询和属性统计,这种特性很适合于统计不同尺度r下对应的N(r) ,因此,可以将分形方法与地理信息系统加以结合,在GIS平台上对地学图形和属性信息进行分析及统计处理,将原来比较繁杂的分形计算操作变得方便简捷,易于实现。本文以武汉中地信息公司开发的MAPGIS地理信息系统为例,对河北某地1∶5万Cu元素化探数据进行了处理,具体说明了以MAPGIS为工具,利用分形方法求取元素化探异常下限的过程,并将计算结果与传统异常下限计算方法所得的结果进行了对比,所得的异常下限值相近?

分形建模广泛地应用于具有自相似性不同尺度测量的地质现象空间分布特征。分形分布的特点要求 大于等于某一尺度的数目，与物体大小之间存在幂函数关系，这种关系具有尺度不变性。这里提出的分形求和法可以确定地球化学数据分组界限。应用澳大利亚新南 威尔士东北地区汇水沉积物地球化学数据，采用分形求和法确定其分组界限，并与传统的概率图模型结果进行比较。铜（Cu）元素数据划分二个部分，一部分是元 素含量少于20ppm的正态分布数据，另一部分是元素含量大于20ppm的多个对数正态分布数据，能识别第三纪玄武岩区域和铜的主要矿化区。这一结论与使 用传统的概率图模型方法得到的结论一致。该方法不仅适用于地球化学铜元素数据，而且还适用于其它元素和地质数据，具有普遍的意义。

The systematic error andbackground differentiation of different geological bodies are concerned in discrimination ofbackground from anomaly, which is an important issue in geochemical prospecting and affectsthe correct extraction of geochemical information and prospecting effectiveness. The methodsof discrimination of anomaly from background are divided into estimating methods and modelrecognition methods. It is necessary to transform the original data to be consistent withgeological regularities.

黑龙江省多宝山地区发育多期以 铜金为主的成矿作用。加里东中期形成了斑岩型铜钼(金)矿床,燕山早期主要形成了矽卡岩型铜铁(金)矿床,燕山晚期形成了浅成热液型金矿床。不同时期矿床 的空间分布受古生代海相火山岩为主的地层的控制,同时,受到NE向和NW向2组断裂交叉形成的环(菱)形构造的控制。各期岩浆作用最晚阶段形成的硅铝质含 量较高且成矿元素明显富集的小型侵入体与成矿关系最为密切。多宝山地区是不同时代构造-岩浆作用的中心地带,富含铜、金等成矿组分的中奥陶统多宝山组海相 火山岩地层是不同时代矿床的统一矿质来源,导致不同时代的成矿作用叠加发生、不同时代矿产种类具有一致性以及矿床集中分布等特点。

地球化学异常下限值是区分背景 区与异常区的基本指标,而计算异常下限值的准确性也直接关系到下一步探矿工作开展的关键。本文选取新疆西天山成矿带托逊地区1:50000土壤X荧光化探 样品中Mn、Fe、Zn、As四种元素为例,使用传统统计方法、多重分形方法、85%累计频率法分别对化探数据进行处理后得出结论:传统统计方法计算出的 异常范围小,且较为分散;多重分形方法对弱小异常的圈定效果明显,但范围过大;85%累计频率法与传统方法所得异常下限值比较接近,但对弱小异常的识别效 果相对于传统方法显著。

The orebodies at Cobar (central N.S.W., Australia) are steeply plunging lenses of considerable vertical extent, transgressive to bedding. They lie roughly parallel to the cleavage of turbidites in the Cobar Supergroup, within the confines of the Cobar Trough. Broadly there are Cu-Au and Pb-Zn mineralizations varying from aggregations of veins to submassive and massive types. A study was initiated to determine the nature and extent of any alteration haloes that might enlarge the drilling target in exploration for blind orebodies in the Cobar region. Results show that the mineralization is surrounded by unusually extensive depletions in Li and less extensive depletions in Na, K, Rb, Sr and Ba in the host metasediments. Apart from Li, these are co-extensive with zones marked by the virtual absence of feldspar and sericite and, proximal to ore, an increase in chlorite. The shapes and extent of the haloes suggest formation in vertical zones of high permeability by a process of fluid flow rather than diffusion. The mineralization, which is not accompanied by significant enhancement haloes of chalcophile elements, appears to have formed later, in discrete zones within the depletion haloes. A hypothesis for the formation of these haloes is proposed. Maturation of kerogens produced water-soluble carboxylic acids and/or phenols which in turn caused a secondary porosity in narrow, vertical zones overlying basement faults. Dewatering into a primitive cleavage took place during early diagenesis, leading to feldspar and mica dissolution by organic acids, transport of variable amounts of aluminium as an organic chelate and alkali and alkaline earth elements as soluble organic salts. Ore deposition probably took place later, just before the onset of greenschist metamorphism. It is speculated that deposition followed the release, upward movement and mixing of highly evolved and concentrated connate brines in the zone of earlier-formed dewatering cleavage, now focused into a tectonic cleavage.

Singular physical or chemical processes may result in anomalous amounts of energy release or mass accumulation that, generally, are confined to narrow intervals in space or time. Singularity is a property of different types of non-linear natural processes including cloud formation, rainfall, hurricanes, flooding, landslides, earthquakes, wildfires, and mineralization. The end products of these non-linear processes can be modeled as fractals or multifractals. Hydrothermal processes in the Earth crust can result in ore deposits characterized by high concentrations of metals with fractal or multifractal properties. Here we show that the non-linear properties of the end products of singular mineralization processes can be applied for prediction of undiscovered mineral deposits and for quantitative mineral resource assessment, whether for mineral exploration or for regional, national and global planning for mineral resource utilization. In addition to the general theory and framework for the non-linear mineral resources assessment, this paper focuses on several power-law models proposed for characterizing non-linear properties of mineralization and for geoinformation extraction and integration. The theories, methods, and computer system discussed in this paper were validated using a case study dealing with hydrothermal Au mineral potential in southern Nova Scotia, Canada.

The Ben Nevis area of Ontario, Canada contains a zone of gold, silver, copper, zinc, lead mineralization that is surrounded by a larger zone of carbonatized volcanic rocks. A study of the lithogeochemistry of the volcanic rocks has shown that spatial presentation of lithogeochemical data combined with correspondence analysis and dynamic cluster analysis can delineate the geology of the area, zones of carbonate alteration, sulphur enrichment and other lithogeochemically anomalous zones. Correspondence analysis calculates factors which explain the distribution of the lithogeochemical data with respect to the chemical components. The most significant factor is interpreted as rock-composition variation (basalts, rhyolites), the second factor indicates the presence of alteration in the form of carbonatization, and the third factor, the presence of sulphur enrichment associated with mineralization. Dynamic cluster analysis separates the sample population into a number of lithogeochemically distinct groups. Groups related to compositional variation can be clearly distinguished from groups that represent alteration in the form of carbonatization or sulphur enrichment. These statistical techniques provide assistance in mineral exploration by identifying samples that have been affected by mineralization processes.