【摘要】：水系沉積物是我國(guó)區(qū)域化探、化探普查等工作的主要采樣介質(zhì),且土壤是水系沉積物的主要來(lái)源,從土壤到水系沉積物風(fēng)化過(guò)程中微量元素含量的變化行為對(duì)化探異常的圈定和解釋具有重要參考價(jià)值。本文以北京西南周口店花崗閃長(zhǎng)巖風(fēng)化剖面為研究對(duì)象,研究其微量元素在風(fēng)化過(guò)程中的變化行為。因此選取部分花崗閃長(zhǎng)巖體發(fā)育的土壤,根據(jù)粒度大小將土壤樣品篩分為7個(gè)粒級(jí),分別通過(guò)鹽水及鹽酸溶液提去土壤中的活動(dòng)態(tài)微量元素以模擬含鹽水系及酸性水系對(duì)土壤中微量元素的提取行為,實(shí)驗(yàn)查明從土壤到水系沉積物風(fēng)化過(guò)程中微量元素含量的變化行為。經(jīng)研究分析得出,風(fēng)化指數(shù)WIG不僅適用于花崗巖風(fēng)化過(guò)程中的定量描述,也適用于花崗閃長(zhǎng)巖風(fēng)化土壤及其水系沉積物的定量描述,而且較其它風(fēng)化指標(biāo)更為靈敏,適用范圍更廣。花崗閃長(zhǎng)巖土壤樣品及其水系沉積物樣品隨粒度的變細(xì)(即樣品粒級(jí)的增大),其風(fēng)化指數(shù)WIG數(shù)值逐漸降低,表明花崗閃長(zhǎng)巖土壤及其水系沉積物樣品具有隨粒度變細(xì)其風(fēng)化程度增強(qiáng)的特征。在我國(guó)不同的自然景觀區(qū),氣候條件不同,物理化學(xué)條件不同,巖石風(fēng)化機(jī)制存在很大差異,所以在不同地區(qū)開(kāi)展水系沉積物測(cè)量和土壤測(cè)量的最佳采樣粒度也不盡相同。依據(jù)微量元素含量從粗粒級(jí)到細(xì)粒級(jí)的變化規(guī)律,本文建議選擇80~100目作為北京周口店地區(qū)土壤和水系沉積物測(cè)量的采樣介質(zhì)。相對(duì)于不同粒級(jí)樣品而言,同一粒級(jí)樣品中微量元素在土壤、鹽水不溶物、酸不溶物中的含量變化并不明顯,為化探普查工作中采集土壤或水系沉積物介質(zhì)進(jìn)行統(tǒng)一異常圈定提供了實(shí)證。根據(jù)風(fēng)化剖面中樣品和模擬實(shí)驗(yàn)中不同粒度樣品中元素行為,分析可知經(jīng)驗(yàn)方程適用于從巖石到土壤再到水系沉積物這一系列過(guò)程中對(duì)27項(xiàng)微量元素的行為定量研究,這對(duì)化探工作中確定微量元素的地球化學(xué)背景值具有重要意義。
[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.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.122;P595

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