摘要
勘查地球化学是利用元素在各种介质中的含量变化来进行找矿勘查,因此,地球化学填图是勘查地球化学的最基础性的工作,正如地质图对于地质工作的重要性一样。在利用地球化学进行找矿预测过程中,元素在不同类型岩石中背景值的变化会对预测过程产生很大的影响,在利用中国西南地区76种元素编图的数据进行成矿预测过程中,将元素分成两类:一类是岩性变化对成矿预测影响较小的元素,这类元素的各类岩石最大背景值与预测区的异常下限比值小于1,且岩石中背景值的最大值与最小值比值也较小,一般小于4。这些元素包括Hg、Cd、Sb、Au、Sn、 Mo、Ag、U、Pb、Bi、W,它们都是地球化学方法应用最有效的矿种。另一类是岩性变化对成矿预测影响较大的元素, 这类元素有Pt、Co、Cr、Cu、Ni、V、Ti等,其岩石中的最大背景值与异常下限比值大于1,且岩石中的背景值最大值与最小值的比值大于8。以Sn和Cu两种元素为例,Sn属于岩性变化影响较小的元素,西南地区的Sn矿床与Sn地球化学异常之间的对应关系很好。而Cu属于岩性影响较大的元素,西南地区的Cu矿床分布与西南地区的巨大的 Cu地球化学异常对应关系较差。对于这组元素,应采用多重分形滤波技术,压制不同背景的干扰,从中提取出矿化信息。
Geochemical exploration is mineral exploration carried out by using variations of element contents in various kinds of media. Therefore geochemical mapping is the most fundamental work for geochemists, just as geological mapping for geologists. Variations in element background values in various types of rock have an important influence on the prognostic process during geochemical prognosis of ore deposits. Seven-six elements for geochemical mapping in southwestern China may be divided into two groups：（1） the element group with less influence of lithological variation on metallogenic prognosis, and （2） the element group with more influence of lithological variation on metallogenic prognosis. The first element group consists of Hg, Cd, Sb, Au, Sn, Mo, Ag, U, Pb, Bi and W, which are characterized by the rados of the highest background values in rocks to the anomaly thresholds in the prognostic region of 〈1 and the ratios of the maximum background values to the minimum background values of 〈4. This geochemical method is very effective for searching for minerals of these elements. The second element group consists of Pt, Co, Cr, Cu, Ni, V and Ti, which are characterized by the rados of their highest background values in rocks to the anomaly thresholds in the prognostic region of 〉1 and the ratios of maximum background values to the minimum background values of 〉8. This paper deals with the elements Sn （belonging to the first element group） and Cu （belonging the second element group）. Sn deposits in southwestern China are closely related to Sn geochemical anomalies, whereas Cu deposits in southwestern China are not necessarily bound up with giant Cu geochemical anomalies. For the second element group, the multifractal filter technique should be used to suppress different background interferences and extract mineralization information from the geochemical anomalies of the elements.
出处
《中国地质》
CAS
CSCD
2006年第2期411-417,共7页
Geology in China
基金
中国地质调查局地质大调查项目(F8.1.1)资助。
关键词
岩石背景值
地球化学填图
成矿预测
element background in rocks
geochemical mapping
metallogenic prognosis
