河口三角洲元素含量与矿产资源--以湘资沅澧为例

基于在研究前人洞庭湖冲积平原区土壤测量资料时发现湘江、资水、沅江、澧水河口三角洲土壤中有明显的成矿元素聚集,且成矿元素的种类、含量与流域内的矿产种类、储量大小密切相关等的资料,以及6年来已经在湘江流域发现了一处巨型锡矿,铜、金矿勘查取得了重大进展的成果,对湘江、资水、沅江、澧水的三角洲及洞庭湖平原长江沉积物中的元素含量做进一步的预测研究。研究结果表明:1)用河口三角洲沉积物中的元素含量减去背景值后的值与汇水盆地面积、厚度及岩石密度相乘的乘积可以大致预测数万平方公里流域内的矿产储量;2)将沉积物厚度分别规定为1.5m,2m,3m和5m,可大致体现不同地质工作程度所取得的储量;3)6年来锡储量的增加完全证实了预测的一定可靠性;4)利用湘江、资水、沅江、澧水河口三角洲元素含量预测上游流域内矿产储量的可行性,大胆探索了利用洞庭湖沉积物中成矿元素含量预测长江上游100余万平方公里汇水流域内的矿产储量。2004年谢学锦院士与挪威的J.Bogen和R.Ottesen开始酝酿一个全球大科学计划“沿世界主要河流的全球地球化学填图”。计划在世界主要大江大河及其支流的河口共采集2000～2500个组合样,分析其中71～76种元素及一些有机物的含量,用以迅速评估全球矿产资源潜力与环境现状。文章认为,

ELEMENT CONCENTRATIONS IN RIVER DELTA SEDIMENTS AND MINERAL RESOURCES POTENTIAL IN THE DRAINAGE BASIN: A CASE STUDY IN THE XIANGJIANG, ZISHUI, YUANJIANG, AND LISHUI RIVERS BASINS

Widely-spaced global geochemical mapping has attracted international interests since the 1990s'. In 1998 the author conducted geochemical soil survey in the Dongting Lake alluvium plain and found that the average concentration of delta sediments at the mouths of the Xiangjiang, Zishui, Yuanjiang, and Lishui rivers draining to the Dongting Lake bears close relation with the mineral resources potential within the drainage basin. An attempt was also made to use the average anomalous contents of ore elements in the Dongting Lake alluvium plain to predict the mineral resources potential in the upstream Changjiang River basin (approx. 1 million km2). The discoveries of large Sn deposits in the Xiangjiang River basin in recent years have verified the feasibility of this approach and analysis of delta sediments samples to predict the mineral resources potential within large drainage basins (10 000 to million km2 in dimension). This will provide strong evidences in supporting the feasibility of the global geochemical mapping project along major rivers in the world.