资源定量评价发展方向展望

SOME SUGGESTED FUTURE DIRECTIONS OF QUANTITATIVE RESOURCE ASSESSMENTS

未来的资源定量评价希望能够评估未发现矿产资源的量、价值并对其进行定位预测 ,以能够表达矿产资源的经济潜力和不确定性 .近年来金属价格的长期下跌提出了对更大型的矿床的需求 .敏感度分析表明了减少评价中不确定性和风险的最有效途径是降低有关吨位估计因素的不确定性 .到目前为止 ,在评价中所有可能造成误差的因素中 ,那些与吨位估计误差有关的因素是最重要的 .鉴于吨位模型的绝对重要地位以及矿床模型是吨位最有效的预测手段 ,正确地选择矿床模型是控制误差最重要的途径 .地表大部分地区被大面积裸露的岩石和沉积物所覆盖 .由于很多出露地表的矿床已经被发现 ,人们开始把注意力转向盖层下面岩石可能显露的矿化信息上 .这些区域的资源评价必需依靠对其周边地区的外推、地下覆盖岩石新的地质填图或者通过在其他成功勘探区获得的经验进行类推 .盖层对评价的不确定性以及评价的方法与程序都具有深远的影响 ,因为地下地质现象的不可见性和地球物理方法所获得的是一种被削弱了的信息 .许多早期的评价方法都是基于从那些出露地表的矿床中总结出的地球化学和地球物理变量之间的关系而进行的 ,而现在我们同样需要研究基于地下隐伏矿床的勘探经验 .矿床模型在资源定量评价中的重要地位基于以下两个原因 :(1)

Future quantitative assessments will be expected to estimate quantities, values, and locations of undiscovered mineral resources in a form that conveys both economic viability and uncertainty associated with the resources. Historically, declining metal prices point to the need for larger deposits over time. Sensitivity analysis demonstrates that the greatest opportunity for reducing uncertainty in assessments lies in lowering uncertainty associated with tonnage estimates. Of all errors possible in assessments, those affecting tonnage estimates are by far the most important. Selecting the correct deposit model is the most important way of controlling errors because the dominance of tonnage-deposit models are the best known predictor of tonnage. Much of the surface is covered with apparently barren rocks and sediments in many large regions. Because many exposed mineral deposits are believed to have been found, a prime concern is the presence of possible mineralized rock under cover. Assessments of areas with resources under cover must rely on extrapolation from surrounding areas, new geologic maps of rocks under cover, or analogy with other well-explored areas that can be considered training tracts. Cover has a profound effect on uncertainty and on methods and procedures of assessments because geology is seldom known and geophysical methods typically have attenuated responses. Many earlier assessment methods were based on relationships of geochemical and geophysical variables to deposits learned from deposits exposed on the surface-these will need to be relearned based on covered deposits. Mineral-deposit models are important in quantitative resource assessments for two reasons: (1) grades and tonnages of most deposit types are significantly different, and (2) deposit types are present in different geologic settings that can be identified from geologic maps. Mineral-deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Grade and tonnage models and development of quantitative descriptive, economic, and deposit density models will help reduce the uncertainty of these new assessments.