柴达木盆地碱山深钻的硼同位素地球化学特征
Boron Isotope Geochemistry of the Deep Borehole in Jianshan Mountains of Qaidam Basin
投稿时间:2019-01-20  修订日期:2019-03-04
DOI:
中文关键词:  柴达木盆地,硼同位素,气候干旱化,盐度,晚中新世
英文关键词:Qaidam Basin  Boron isotope  Climate drought  Salinity  Late Miocene
基金项目:
作者单位邮编
卢胜城 中国科学院青海盐湖研究所 810008
韩文霞 中国科学院青海盐湖研究所 
韩凤清 中国科学院青海盐湖研究所 810008
马云麒 中国科学院青海盐湖研究所 
吕爽 中国科学院青海盐湖研究所 
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中文摘要:
      硼(B)同位素组成可以反映其地质成因环境及其经历的地质过程,因此在许多领域的研究中都有较为广泛的应用。本文通过对位于柴达木盆地碱山背斜顶部的SG-1b钻孔沉积物(7.3~1.6 Ma)水溶组分的B同位素研究,发现钻孔沉积物B含量在38.55~172.3 μg/g之间,平均含量为87.6 μg/g;δ11B值的变化范围在3.61‰~16.26‰之间,平均值为10.65‰,B含量与δ11B值具有一定的正相关关系。进一步分析表明,在碱山地区古湖演化的过程中,影响B同位素分馏的自然因素主要是粘土矿物的吸附作用以及碳酸盐矿物以及石膏等的离子共沉淀作用。B含量和δ11B值自钻孔底部向上的逐步增加以及后期的急剧增加,与水溶离子含量以及矿物和粒度等的变化一致,表明柴达木盆地晚中新世以来的湖泊沉积物B含量和δ11B值可以很好地反映研究区气候和湖水的演化过程,共同指示了研究区自7.3 Ma以来气候的持续干旱化和湖水盐度的逐步增加,以及3.3Ma以来干旱化和湖水浓缩过程的加剧。
英文摘要:
      Boron (B) isotopic composition can reflect its geological genetic environment and geological process, so it has been widely used in many fields. In this paper, we studied the B isotopes of the water-soluble components from the SG-1b borehole sediments located at the top of the Jianshan Anticline in the West Qaidam Basin. The results show that the B content ranges from 38.55 to 172.3 ug/g, with an average content of 87.6 ug/g; and the variation range of the δ11B value ranges from 3.61 to 16.26, with an average value of 10.65. There is a positive correlation between the B content and the δ11B value. It is found that the main natural factors affecting B isotope fractionation during the evolution of the paleolake are the adsorption of clay minerals and ion coprecipitation of carbonate minerals and gypsum. From the bottom of the borehole to the top, the gradual increase of B content and δ11B value as well as the sharp increase of B content and δ11B value in the later period are consistent with the results of water-soluble ion content, mineral and particle size. It shows that the B content and δ11B value of lake sediments in Qaidam Basin since the Late Miocene can well reflect the evolution process of climate and lake water in the study area, and together indicate the continuous drought of climate and the gradual increase of salinity of Lake water in the study area since 7.3 Ma, and the intensification of the process of drought and lake water concentration since 3.3 Ma.
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