周口店花岗闪长岩风化过程元素地球化学行为研究

发布时间：2018-09-03 06:23

【摘要】：水系沉积物是我国区域化探、化探普查等工作的主要采样介质,且土壤是水系沉积物的主要来源,从土壤到水系沉积物风化过程中微量元素含量的变化行为对化探异常的圈定和解释具有重要参考价值。本文以北京西南周口店花岗闪长岩风化剖面为研究对象,研究其微量元素在风化过程中的变化行为。因此选取部分花岗闪长岩体发育的土壤,根据粒度大小将土壤样品筛分为7个粒级,分别通过盐水及盐酸溶液提去土壤中的活动态微量元素以模拟含盐水系及酸性水系对土壤中微量元素的提取行为,实验查明从土壤到水系沉积物风化过程中微量元素含量的变化行为。经研究分析得出,风化指数WIG不仅适用于花岗岩风化过程中的定量描述,也适用于花岗闪长岩风化土壤及其水系沉积物的定量描述,而且较其它风化指标更为灵敏,适用范围更广。花岗闪长岩土壤样品及其水系沉积物样品随粒度的变细(即样品粒级的增大),其风化指数WIG数值逐渐降低,表明花岗闪长岩土壤及其水系沉积物样品具有随粒度变细其风化程度增强的特征。在我国不同的自然景观区,气候条件不同,物理化学条件不同,岩石风化机制存在很大差异,所以在不同地区开展水系沉积物测量和土壤测量的最佳采样粒度也不尽相同。依据微量元素含量从粗粒级到细粒级的变化规律,本文建议选择80~100目作为北京周口店地区土壤和水系沉积物测量的采样介质。相对于不同粒级样品而言,同一粒级样品中微量元素在土壤、盐水不溶物、酸不溶物中的含量变化并不明显,为化探普查工作中采集土壤或水系沉积物介质进行统一异常圈定提供了实证。根据风化剖面中样品和模拟实验中不同粒度样品中元素行为,分析可知经验方程适用于从岩石到土壤再到水系沉积物这一系列过程中对27项微量元素的行为定量研究,这对化探工作中确定微量元素的地球化学背景值具有重要意义。
[Abstract]:Water system sediment is the main sampling medium for regional geochemical exploration and geochemical survey in China, and soil is the main source of water system sediment. The change of trace element content in the weathering process from soil to river sediment has important reference value for the delineation and interpretation of geochemical anomalies. In this paper, the weathering profile of Zhoukoudian granodiorite in southwest Beijing is studied to study the changing behavior of trace elements during weathering. Therefore, selected part of the granodiorite developed soil, according to the size of the soil samples were sifted into 7 grain size, In order to simulate the extraction behavior of trace elements in saline and acid water systems, the active trace elements in soil were removed by saline and hydrochloric acid solution, respectively. The change behavior of trace element content in weathering process from soil to river sediment was investigated. The results show that the weathering index (WIG) is not only suitable for the quantitative description of granite weathering process, but also applicable to the quantitative description of granodiorite weathering soil and sediments, and is more sensitive than other weathering indexes. The scope of application is wider. The weathering index (WIG) of granodiorite soil samples and their sediment samples gradually decrease with the grain size increasing. The results show that the weathering degree of granodiorite soil and its sediment is enhanced with granularity. In different natural landscape areas of China, the climatic conditions, physical and chemical conditions are different, and the weathering mechanism of rock is very different, so the optimal sampling granularity for river sediment survey and soil survey is different in different areas. Based on the change of trace element content from coarse grain to fine grain, it is suggested that 80 ~ 100 mesh should be selected as the sampling medium for the measurement of soil and water system sediment in Zhoukoudian area, Beijing. The contents of trace elements in soil, salt water insoluble and acid insoluble in the same grain size sample are not obvious, compared with the different grain size samples, the content of trace elements in the same grain size sample is not obvious. It provides an empirical example for collecting soil or sediment media in geochemical survey to delineate the unified anomaly. According to the behavior of elements in weathering profile and in different particle size samples in simulation experiment, the empirical equation can be used to quantitatively study the behavior of 27 trace elements in a series of processes from rock to soil to river sediment. It is of great significance to determine the geochemical background value of trace elements in geochemical exploration.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.122;P595

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