新疆博斯腾湖全新世沉积磁性矿物组成与沉积环境探讨

发布时间：2018-03-24 07:09

本文选题：干旱区　切入点：博斯腾湖　出处：《干旱区地理》2017年03期

【摘要】：中国西北干旱区湖泊沉积物存在磁性矿物种类复杂和磁化率普遍偏低等问题,使得利用环境磁学手段重建古环境、古气候的方法受到了限制。选择新疆博斯腾湖BST12B钻孔顶部岩芯(深度0~2.5 m)不同沉积相的代表性样品,进行载磁性矿物富集,并将原样品和富集获得的样品分别做XRD(X荧光衍射)岩石矿物检测。结果显示,所有湖相样品中均有黄铁矿和磁铁矿检出,而没有磁黄铁矿和针铁矿检出,说明博斯腾湖全新世湖相沉积物的主要磁性矿物是磁铁矿,并含有少量黄铁矿;富集获得的样品中粘土矿物(如绿泥石等)含量明显增加,石英、长石和方解石含量降低,富集后的残留样品的磁化率大幅度降低,说明粘土矿物对干旱区湖泊沉积物的磁学贡献不容忽视。结合沉积物粒度、色度、硫元素含量以及沉积物磁性矿物的组合特征推断,黄铁矿可以作为湖泊高水位的指示矿物种类,因而具有重建湖泊古水位变化的潜力,并应用到博斯腾湖的全新世湖泊环境重建,发现博斯腾湖BST12B钻孔位置早全新世为接近氧化环境的浅湖相环境,而中晚全新世为深湖相沉积环境并存在一个浅水的湖滨相沉积环境。研究结果说明,利用载磁性矿物富集的方法对干旱区湖泊沉积物中所含磁性矿物进行富集后检测是开展干旱区湖泊环境磁学研究的可行手段,对研究湖泊环境变化具有重要意义。
[Abstract]:The sediments of lakes in arid area of Northwest China China problems of magnetic mineral species complex and magnetic susceptibility is generally low, making the reconstruction of ancient environment by means of environmental magnetism, ancient climate is limited. Xinjiang Bosten Lake BST12B (0~2.5 m top core drilling depth) with different sedimentary facies of representative samples were loaded magnetic minerals. And the original sample and the enrichment obtained samples were XRD (X fluorescence diffraction). The results showed that the detection of rock and mineral, pyrite and magnetite were detected in all samples in the lake, and no pyrrhotite and needle iron ore detected, indicating that the main magnetic minerals of Bosten Lake Holocene lacustrine deposits are magnetite, and contains a small amount of pyrite clay minerals; enrichment in the sample obtained (such as chlorite) content increased, quartz, feldspar and calcite content decreased, the residual magnetization of sample enrichment rate Decrease that magnetism of clay minerals in arid area of lake sediment contribution can not be ignored. Combined with the sediment granularity, chroma, sulfur content and sediment magnetic mineral assemblages that pyrite can be used as indicator minerals in lake level, thus has the reconstruction of lake level change of ancient potential, and applied to the Holocene Lake Environment reconstruction Bosten Lake, Bosten Lake found BST12B drilling position in early Holocene to oxidizing environment shallow lacustrine environment, while the middle and late Holocene sedimentary environment for the existence of a deep lake and shallow lake sedimentary environment. The study results show that using the method of loading magnetic minerals for enrichment of magnetic containing sediments in arid area after detection is carried out in Lake mineral feasible means of lakes in arid land of environmental magnetism, it is important to study on the changes in lake environment.

【作者单位】：兰州大学西部环境教育部重点实验室兰州大学资源环境学院;
【基金】：国家自然基金重点项目(41130102) 中央高校基本科研业务费专项资金(lzujbky-2013-121)联合资助
【分类号】：P512.2;P534.632

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