临夏盆地晚中新世沉积物中赤铁矿和针铁矿的含量特征及其意义

Characteristics and implications of hematite and goethite concentration in sediments of the late miocene,Linxia Basin

利用对铁氧化物矿物灵敏的漫反射光谱法,对临夏盆地的黑林顶剖面(古地磁年代为11.8～5.0Ma)赤铁矿和针铁矿含量进行测定.结果表明:赤铁矿含量在8.6 Ma以前相对较高,在8.6 Ma以后骤然降低并稳定在一低值范围;针铁矿则没有明显的变化趋势,赤铁矿/针铁矿的变化则与赤铁矿的变化趋势一致;赤铁矿、针铁矿含量及其比值在该剖面的变化特征主要反映了8.6 Ma以来亚洲内陆干旱化的加剧,可能与青藏高原在该时期的剧烈隆升密切相关.

The miocene sediments in the Linxia basin are important for understanding the Qinghai-Tibetan plateau uplift and the east Asian monsoon developments. Hematite and goethite from the Heilinding section in the southern margin of the Linxia basin （11.8-5.0 Ma） were tested. The content of the hematite was high in 11.8-8.6 Ma, decreasing obviously at 8.6 Ma and kept stable in 8.6-5.0 Ma, whereas goethite was almost stable throughout the periad. The trend of hematite/goethite ration was similar to hematite content. Such hematite, goethite and hematite/goethite contents in the Heilinding section probably indicate a strong aridification process since 8.6 Ma in central Asia, which was linked to the Qinghai-Tibetan plateau uplift during this time.