Study On Hypergene Geochemistry And Exploration Methods And Technologies In The Cold And Arid Deserta Landscape Area

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.