新疆查岗诺尔铁矿上覆盖层地球化学元素垂向分布特征

Vertical distribution of geochemical elements in the overburden of the Chagangnuoer iron deposit,Xinjiang

我国西北部地区被戈壁荒漠广泛覆盖,这一地带在地质上处于我国古亚洲成矿域及其两侧地区,成矿条件优越,进一步找矿勘探尤其是寻找隐伏矿的潜力巨大,是西部大开发的重要金属资源远景区。分析了查岗诺尔铁矿某矿体上方土壤覆盖层中不同深度、不同粒径中元素含量的分布规律,旨在为覆盖区地球化学找矿提供参考。在土壤剖面采集自地表至基岩5、15、30、45、60、75、90、105、120、135、150 cm处的土壤样品,共11件。研究发现,在粒径〉2.00 mm的粗颗粒中,元素可分为2类：As、Cu、Co、Fe、Zn为第一类;Sb、Sn、Ni为第二类。第一类总体表现为自底部至顶部元素含量呈逐渐增加的趋势,可能受后期作用影响较大;第二类表现为由底部至顶部,元素含量逐渐降低。在粒径2.00~0.850、0.850~0.425、0.425~0.250、0.250~0.180、〈0.180 mm较细颗粒中,As、Zn渐变模式与大于2.00 mm的粗颗粒表现一致,亦为从底部至顶部元素含量呈逐渐增加的趋势;而另一些元素Sb、Sn、Ni、Cu、Co、Fe表现为底部元素含量较高、顶部元素含量较低、中间振荡变化的复合型变化模式。这种复合型变化可能说明该地区土壤中主要元素含量受下部隐伏矿的影响显著,继承了下部基岩的特征,元素在成土过程中呈现逐步贫化的趋势,预示该地区在覆盖区隐伏矿找矿过程中,可以参考土壤层中元素含量递减区域的分布特征进行进一步勘探。

The northwest China region is widely covered by gobi deserts, which lies in the Paleo-Asia metallogenic domain and has excellent metallogenic conditions. This region has a good prospecting potential to discover buried orebodies, and is thus an important prospecting area for metal resources during the development of the West Regions. This study analyzed the element concentration distribution at different depths and of different grain sizes of soil covers of an orebody in the Chagangnuoer iron ore deposit, in order to provide references for geochemical prospecting in covered areas. A total of 11 soil samples collected from the surface to the bedrock along one vertical soil profile were analyzed, and the depths of the soil samples were 5, 15, 30, 45, 60, 75, 90, 105, 120, 135 and 150 cm, respectively. It is indicated that among the coarse-grained samples, the elements can be divided into two groups ： （ 1 ） As, Cu, Co, Fe and Zn; and （2） Sb, Sn and Ni. The element concentrations of the first group increase gradually from bottom to top and may be affected by the late process, while those of the second group exhibit a gradually reducd trend. Moreover, among those of grain sizes of 2.00-0.850, 0.850~0.425, 0.425~0.250, 0.250~0.180 and 〈0.180 mm, the variations of the As and Zn concentration show a simi- lar trend with the elements of those with grain sizes larger than 2. 00 mm. The concentrations of another type of elements, i.e., Sb, Sn, Ni, Cu, Co and Fe, show strong fluctuations from bottom, middle to the top of the profile, which are higher at the bottom and lower at the top but fluctuate irregularly among the middle parts. These composite variations suggest that the content of the main elements in the soil is significantly influenced by the lower buried ores, with a similar trend with the bottom bedrock. The elements become depleted during the soil-forming process. It is thus inferred that those areas with decreasing element content in soil should be further explored during the next prospecting of concealed orebodies in covered areas.