青海北祁连中南沟水系沉积物地球化学特征

GEOCHEMICAL CHARACTERISTICS OF STREAM SEDIMENTS IN ZHONGNANGOU OF NORTH QILIAN MOUNTAINS,QINGHAI PROVINCE

青海北祁连中南沟高山切割明显，坡下植被发育，属高寒草甸景观，不利于颗粒物质的机械迁移。该地区不同粒级水系沉积物中成矿元素变化趋势一致，含量衰减迅速且在细粒级富集，并主要为硫化物相。研究结果说明，在该地区常规水系碎屑沉积物测量方法存在一定问题。由于草甸发育，颗粒物质迁移受到抑止，水系碎屑沉积物仅出现在2～3级水系。因此，在普查阶段可能会漏掉许多矿化信息；由于受其分布所限，详查阶段无法保证采集到真正的水系沉积物，只能用坡积物代替，导致采样介质不统一。

Located in North Qilian Mountains, Qinghai Province, Zhongnangou belongs to alpine meadow landscape. It has evident alpine-gorge incision and well-developed vegetation below slope, which are obviously unfavorable for granule mechanic motion. Studies indicate that transformation trends of the metallogenic elements in stream sediments of diverse granule grades are identical. The metallogenic elements decrease rapidly in quantity, and are concentrated in the fine size fraction, mainly in the form of sulfide facies. Researches also indicate that the conventional measuring methods for stream detrital sediments have the following defects： granule motion is restrained due to well-developed meadow; stream detrital sediments appear only in Grade 2～3 drainage, and hence much mineraliza- tion information might be lost at the reconnaissance stage; at the detailed investigation stage, it is very difficult to collect samples in the real stream sediments due to their limited distribution; where slope sediment samples are collected to replace stream sediment samples, the problem of non-unification of sampling media will occur.