戈壁覆盖区景观演化与Au的分散迁移  

Dispersion and Migration of Gold Under Landscape Evolution in Gobi Desert Terrains

作　　者：张必敏[1,2,3] 王学求[1,3] 迟清华[1,3] 吕庆田[2] 

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质科学院应用地球化学重点开放实验室,河北廊坊065000

出　　处：《现代地质》2011年第3期575-580,共6页Geoscience

基　　金：国土资源部公益性行业科研专项(SinoProbe-04-03);国家高技术研究发展计划项目(2006AA06Z135);中国地质调查局国土资源大调查项目(1212010916041)

摘　　要：我国西北部一些戈壁荒漠区经历长期的风化侵蚀作用而形成准平原,景观演化过程改变了元素的分散模式,对地球化学勘查是很大的难题。为了研究戈壁覆盖区元素在准平原化过程中的分散与迁移情况,选择新疆金窝子金矿,并运用空气动力反循环钻开展了采样研究工作。结果表明:金倾向于在矿体上方垂向剖面的顶层和底层土壤中富集;地表或近地表富粘土层中土壤细粒级样品中金的含量普遍高于粗粒级样品中金的含量,并且地表最大的金异常出现在矿体上方细粒级(-100目)样品中;覆盖层底部风化层中金在不同粒级中的分布没有明显的不同,底部异常往往出现在基岩面低洼处。这些结果说明在准平原化过程中,成矿物质受到剥蚀和搬运作用发生侧向迁移而在低洼处沉积下来,元素Au又通过多营力接力发生垂向迁移至地表,并被地表粘土和铁锰氧化物形成的地球化学障所捕获,从而在地表形成直接指示矿体的地球化学异常。Some Gobi desert terrains in northwestern China are peneplains formed by a long period of erosion.Dispersion pattern of elements is changed under this kind of landscape evolution.Jinwozi gold deposit was selected for study of element dispersion and migration in the process of pediplanation by using overburden drilling sampling.The results show that（1） gold tends to concentrate in the top and bottom of the vertical profile over the ore body;（2） gold is enriched in the fine-grained fractions of soils with clay-rich horizons at surface or near surface and the largest gold anomalies occur in fine grained samples（-100 mesh） over the ore body;（3） gold distribution in different size fractions of soils at the bottom of the weathering regolith display no obvious diffe-rence but tend to be anomalously enriched in bedrock troughs.This indicates that gold was concentrated in the lowest places by erosion and lateral transportation during the process of pediplanation.Vertical migration to the soil surface and entrapment by clays and amorphous Fe-Mn oxides leads to the formation of geochemical anomalies directly over the ore body.

关 键 词：戈壁覆盖区 景观演化 准平原化 金窝子金矿 地球化学异常 侧向分散 垂向迁移 

分 类 号：P596[天文地球—地球化学] P595[天文地球—地质学]