【作者】 喻劲松；

【导师】 岑况； 张华；

【作者基本信息】 中国地质大学（北京） ， 地球化学， 2005， 博士

【摘要】 长期以来,高寒干旱荒漠景观区地球化学勘查采用的方法技术各异,解决干扰地球化学异常的应对措施不尽相同,所获区域地球化学异常信息被掩蔽、弱化或地球化学及其异常分布规律难以判明。以土壤、水系沉积物、风成沙为研究对象,研究其元素的表生地球化学特征,目的是查明风成沙对地球化学异常的干扰,研制适宜高寒干旱荒漠景观区的地球化学勘查方法技术。　研究表明,高寒干旱荒漠景观区土壤与水系沉积物大于40 目粗粒级部分主要为岩屑,影响其元素地球化学分布的主要因素为所处地质背景和元素自身地球化学性质,风成沙的干扰很小;小于80 目细粒级部分受到大量掺入的风成沙的严重干扰,对元素表生地球化学分布产生影响,导致异常消失、弱化或抬升背景,根源来自风成沙优势粒级(-80 目)所汇聚的矿物。　水系沉积物在流水作用下,矿物自然分选表现出重矿物向-80 目细粒级聚集的趋势,与之相对应的元素亦呈现出从粗粒向细粒级含量逐渐升高的态势,表明重矿物是元素沿水系迁移的重要载体;其中,Ag、Pb、Bi、Sb 主要赋存在无磁性重矿物中,Zn、Cu主要赋存于电磁性重矿物,Fe、Ni、Co 主要赋存在强磁性重矿物内;具有小型以上规模的矿床,其主要成矿元素在主异常水系中的迁移距离通常可达4~5 km以上,流水搬运形成的矿物分选,使部分主矿化元素异常向下游水系有较大的延伸,一定程度上影响了元素地球化学异常的空间分布。依据上述研究成果和地球化学勘查不同阶段的目的,研究总结提出适合高寒干旱荒漠景观区的地球化学勘查方法技术为:1/20 万区域地球化学普查阶段以水系沉积物为采样介质,基本采样密度1 点/4km2,采样粒级-10~+80 目可有效排除风成沙干扰,获取接近汇水域内基岩地球化学特征的信息;异常追踪阶段适宜开展1/5 万水系沉积物测量,基本采样密度4~8 点/km2,采样粒级-10~+80 目,可迅速缩小找矿靶区;异常查证阶段可采用土壤地球化学测量方法,面积性测量采样密度50~100 点/km2,剖面测量点距50m,至少3 条剖面,采集基岩上部风化层土壤,采样粒级-10~+80 目。更多还原

【Abstract】 For a long time, the methods adopted in the geochemical exploration in the cold and arid deserta areas are different for their measures to discover geochemical anomalies. The regional geochemical anomalies information acquired from these methods is often concealed, weakened or difficult to be ascertained. In the paper, the hypergene geochemical anomalies of elements distributed in the soil, stream sediment and eolian sand are studied to find out the interference of eolian sand with geochemical anomalies and to develop new geochemical prospecting methods that is suitable in the cold and arid deserta areas. The research result shows that, in the soil and stream sediment located in the cold and arid deserta, the coarse particle grade part whose size is bigger than 40 meshes are mainly rock debris. The main factors influencing element geochemical distribution in the debris include the geological setting and geochemical character of element self and the interference of eolian sand is weak. The fine particle grade part whose size is less than 80 meshes is interfered severely by the eolian sand mixed in a great deal. The eolian sand has influence on the distribution of geochemical anomalies, which results in the disappearance and weakness of anomalies or rise of background value. It is attributed from the heavy mineral distributing in the dominant particle size (-80 meshes) of the eolian sand. For the effect of water flow, the minerals in the stream sediment show the trend that heavy minerals is enriched in fine particle grade with a grade size of –80 meshes, and therefore, the content of relevant elements increases from the coarse particle grade to fine particle grade gradually. It indicated that the heavy minerals are important media for the migration of elements along the water system. Among these elements, silver, lead, bismuth and antimony are mainly distributed in the heavy minerals without magnetism; zinc and copper are mainly distributed in the heavy minerals with electromagnetic property; iron, nickel and cobalt are mainly distributed in the heavy minerals with strong magnetism. The main ore-forming elements in the deposit with a small size scale or above could often migrate over 4~5 km in the water system with main anomalies. The minerals separation formed in the transportation of flowing water makes part of main mineralized elements anomalies extending along the lower reaches of water system much and has influences on the spatial distribution of elements geochemical anomalies in some degree. On the basis of the study results above and according to the purposes in the different geochemical prospecting stages, the geochemical prospecting methods and technologies, which are suitable for the cold and arid deserta, are put forward as following: in the 1/200000 scale of regional geochemical general exploration, the stream sediment should serve as sampling medium with a sampling density of 1 sampling site per 4 km2 and sample particle grade of -10~+80 meshes. By the method, the interference of eolian sand could be eliminated effectively and the geochemical information about base rock adjacent to the water catchments regions could also be acquired; in the tracing stage of anomalies, 1/50000 scale of stream sediment survey is suitable to be carried out with a sampling density of 4~8 sampling sites per km2 and sample particle grade of -10~+80 meshes, which could reduce the mine prospecting target area rapidly; in the verification stage of anomalies, soil geochemical methods could be adopted with a sampling density of 50~100 sampling sites per km2 in the case of area survey and a point distance of 50m in section survey. At least, three sections should be sampled and the samples should come from the soil located in aerated layer at the top of base rock with a sampling particle size of -10~+80 meshes.更多还原