老挝南部安东花岗闪长岩砖红土型风化壳分带及微量元素地球化学特征

在热带雨林特殊生态景观中和湿热气候条件下,老挝南部阿速波省(Attapeu)安东地区(Antoum)二叠纪花岗闪长岩形成了发育完整的砖红土型风化壳,该风化壳剖面分带明显,最下部为蚀变花岗闪长岩(基岩),往上依次为半风化蚀变花岗闪长岩→高岭石残积层带→砖红土带→森林表土带.测试了采集于红土型风化壳剖面不同分带样品的20种微量元素含量,微量元素可划分出6种变化模式,其中最明显的为Cu、Mo、As、Bi、Au等在高岭土风化带上部显著富集.认为在今后土壤地球化学普查和详查中,经过加大采样深度,采用固定相态提取法或部分提取法可能是强化地球化学异常、探测深部找矿信息的有效途径.

GEOCHEMICAL CHARACTERISTICS OF TRACE ELEMENTS IN LATERITIC REGOLITH PROFILE OF GRANODIORITE IN ANTOUM AREA, LAO PDR

A perfect profile of lateritic regolith of the Permian granodiorite has been well developed in Antoum area of Attapeu Province, Lao PDR, owing to typically tropical monsoon in the rainforest ecosystem. The profile has obvious zoning characteristics which, from the bottom to the top, have altered granodiorite in the lowest profile, partly weathered alfred granodiorite, kaolinitic residual zone, lateritic soil zone, and finally forest topsoil zone.Based on samples collected from the profile and analysis of 20 trace elements, six regular patterns of trace element distributions can be recognized, of which Cu, Mo, As, Bi and Au are observably enriched in the upper part of kaolinitic residual zone. It was suggested that fixed phase - extracted or partly phase - extracted methods and deep sampling may be employed for soil geochemical survey in the future so as to enlarge geochemical anomaly and find exploration information in the depth.