超低密度河漫滩沉积物地球化学采样的代表性

为了响应国际地球化学旗图计划(ICCP259)中的全球地球化学采样子计划的实施,研制超低密度地球化学采样的最佳方法,1989～1990年在江西省开展了一项试点研究.在约15.7万平方公里的可采面积内采集了121件河漫滩沉积物样品.平均采样密度约为五个点/1300km².采样覆盖度为24%.采样点主要布置在100-500km²的汇水盆地口上,其中有33个采样点控制的汇水盆地面积在400～2000km²之间.河漫滩沉积物样品来自深度在0.5m以下到1.2m的柱状剖面.样品定量分析了38种元素.文章从多方面讨论了超低密度河漫滩沉积物地球化学术样的代表性,并得出以下主要结论:1.在400-2000km²的汇水盆地口上采集河漫滩沉积物样品能较好地反映上游汇水盆地中的主要矿化.2.超低密度采样和以2个点/km²采集水系沉积物样品所获得的W、Sn、Cu、Pb和Zn五个元素的地球化学趋势相似.3.超低密度样品中W、Ph、Be、Rb等元素的分布特征与省内花岗岩的分布相吻合.4.超低密来样品中“3Ni+Cr+V”的分布能较好地反映扬子准地台与华南加里东精皱系在省内的分界线.

THE REPRESENTATIVENESS OF WIDE-SPACED OVERBANK SEDIMENT GEOCHEMICAL SAMPLING

In response to the performance of the Global Goochomical Sampling (a subproject of the IGCP Project 259, International Geochemical Mapping), an orientation study was conducted in 1989-1990 to develop an optimum wide-spaced geoehemical sampling approach in Jiangxi Province, Southsart China. 121 overbank sediment samples were collected in an area of about 157,000 km2, with the average sampling density being 1 sample/1,300 km2, and the sampling coverage being 24%. Most of the samples were collected at outflow sites of the drainage basins with an area of 100-500 km2, including 33 samples that control basins of 400-2,000 km2.Overbank sediment samples were taken at a dspth of 50-120 cm, and the samples were analyzed quantitatively for 38 elements. The representativeness of wide-spaced overbot sediment sampling is discussed from vinous angles in the paper, with tho following conclusions reached:-Sampling at the outflow areas of 400-2,000 km2 drainage basins can reveal the major minoralizations in the basins;-W, Sn, Cu. Pb and Zn in both wide-spaced samples and drainage sediment samples collected at a density of a samples/km2 manifest similar regional geochemical trends;-Distribution of W, Pb, Be and Rb coincides with the Yanshanian graftes closely related to the major ore-forming plocesses in Jiangxi;-Distribution of "3Ni Cr V" in wide-spaced samples can distinctly reveal the boundary between the Yangtze paraplatform and the Caledonian fold symbol in Jiangxi.