内蒙干旱荒漠区域化探工作方法初步研究

内蒙和我国其它干旱荒漠区一样,由于:(1)风成沙干扰,使通常所选用的采样介质(土壤、水系沉积物)元素含量遭到稀释、歪曲,乃至样品间几乎没有差异；(2)缺乏一套针对干旱环境特点和该区地貌组合的特殊工作方法,致使区域性化探工作长期处于不利局面。

A PRELIMIARY STUDY ON THE UTILIZATION OFREGIONAL GEOCHEMICAL PROSPECTING METHOD INTHE ARID AND DESERT AREA OF INNER MONGOLIA

This paper presents some valuable results obtained in experimental geoc-bemical exploration work in tbe arid area of Inner Mongolia. Surface soil and drainage sediments in tbe arid area of Inner Mongolia and western Gansu are commonly mixed with aeolian (wind-borne) sand, whose interference reduces element contents of geocbemical samples nearly to background values. Aimed at eliminating the effect of this aeolian sand, we have graded the geochemical samples according to grain size, calculated tbe proportion possessed by eachsize fraction, made microscopic identification for genesis and determined contents of various elements. The resulting data suggest that aeolian sand is predominantly of -0.9-+0.2 mm in size and the optimum sampling size seems to be -5-+2 mm-samples in this size range show high anomalous values with small variation coeJficients and fine recurrence. Investigation has also been made on such problems as optimum sampling site, sampling horizon and sampling density, combined with a comparison of effectiveness between soil survey, rock survey, hydrochemical survey and some other geochemical methods. Ail this has led to the conclusion that, in arid and desert areas, the most economical and efficient regional geochemical prospecting methods are drainage sediment survey of coarse-sized fraction and underground hydroche mical survey, whereas in peneplane or denuded gobi areas the optimum sampling media are rocks and underground water, with soil being secondary in importance.