摘要:
羌塘高原是目前区域化探全国扫面工作最大的空白区和地质找矿工作的新区,这里的化探扫面和地质找矿工作正在推进中。水系沉积物测量是该区主要区域化探扫面方法。在羌塘高原上,风成沙广布,其粒级主要集中在–40目,比例高达90%以上,是影响区域化探找矿效果的最大因素。通过四个矿区水系沉积物地球化学特征研究发现:1)水系沉积物不同粒级中,大部分矿化指示元素含量都呈不对称的“反S”型或“U”型分布,富集在+40目粒级和–160目粒级中。以–10~+40目为采样粒级,很大程度上可以消除风成沙的干扰。2)大型矿床形成的指示元素异常沿水系迁移距离为4~8 km,异常面积>25 km2;小型矿床形成的异常迁移距离1 km左右,异常面积1 km2左右。3)确定区域化探扫面最佳技术指标为:采样粒级–10~+40目;采样密度1点/4 km2(勘查目标定位到大型以上矿床时)或1点/km2(勘查目标定位到小型以上矿床时)。
Abstract:
The Qiangtang Plateau is the largest area not covered by the RGNR (Regional Geochemistry-National Reconnaissance Program) and also a new working area of the geological prospecting work, where the geochemical exploration scanning work and geological prospecting work are in advance. Stream sediment survey is the main method of the RGNR. In the Qiangtang Plateau, Aeolian sand deposit is widespread, and more than 90%fragment sizes of this kind of sand are concentrated in–40 meshes, which is the major factor influencing the prospecting effect of the RGNR. Some conclusions have been reached on the basis of the study of the geochemical characteristics of stream sediments in four ore districts:1) Stream sediments have different fraction sizes, and most of the mineralization-indicating elements exhibit asymmetric “inversed S” type or “U” type distribution and are concentrated in the –40 mesh fraction and +160 mesh fraction. With –10 ~ +40 mesh as the sampling fraction, the interference of the eolian sand can be eliminated to a great extent. 2) For the large ore deposit, the migration distance of the indicator element anomaly is 4~8 km along the stream systems, with the anomalous area being>25 km2;for the small ore deposit, the migration distance is about 1 km, and the anomalous area is 1 km2 or so. 3) The best technical criteria for the identification of the RGNR are as follows:the sampling fractions are–10~+40 mesh, the sampling density is 1/4 km2 (exploration targeted at large or superlarge deposits) or 1/km2 (exploration targeted at small deposits).
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