【摘要】：巴丹吉林沙漠許多湖泊分布鈣華,關(guān)于鈣華成因及其氣候環(huán)境意義,尚無定論:針對沙漠湖泊鈣華基礎(chǔ)特征調(diào)查及其成因的研究也不多見。鈣華作為水化學(xué)作用的產(chǎn)物,研究其沉積機制能為其他相關(guān)科研工作提供新的證據(jù),如湖泊演化、氣候演化、地下水補給來源等。本論文依托"巴丹吉林沙漠及其周邊地區(qū)1:25萬水文地質(zhì)調(diào)查"項目(編號:DD20160295),針對沙漠內(nèi)鈣華分布規(guī)模較大的7個湖泊進行湖水、地下水取樣分析,并以車日格勒湖為重點,鉆取了湖岸3.8米深的鈣華巖芯,通過SEM掃描、能譜分析、巖礦測試、鈾系測年等方法,確定了鈣華沉積時期及其地球化學(xué)特征。為研究鈣華沉積機制,開展了室內(nèi)模擬實驗,重點研究沉積過程中溫度效應(yīng)、混合效應(yīng)的影響,同時借助PHREEQC軟件,建立正向與反向模型,研究沉積過程中pH值、PCO_2、溫度、混合比例等因素的影響,最終闡明車日格勒鈣華沉積的物質(zhì)來源及其成因機制。論文主要取得以下成果與認識:1:總結(jié)了鈣華分布與地球化學(xué)特征鈣華主要分布在湖岸泉水出露帶及其附近區(qū)域。樣品CaO含量多高于50%,結(jié)晶形態(tài)主要為六方柱狀、三角錐狀方解石與針狀文石,反映了低溫的沉積環(huán)境。碳氧同位素均值為δ13C=1.31‰,δ180=-3.52‰,兩者相關(guān)性強,反映了鈣華沉積時脫氣作用的影響。測年范圍在597～4216aBP范圍內(nèi),亂序的測年結(jié)果表明了鈣華加積模式包括自下而上與后期充填;距今2000年內(nèi)鈣華沉積速率加快,且現(xiàn)代仍在不斷沉積。2:分析了鈣華沉積的水動力條件湖區(qū)地下水由南東向北西徑流,氘氧同位素、動態(tài)監(jiān)測數(shù)據(jù)顯示,車日格勒全年接受四周地下水補給,依靠蒸發(fā)排泄,為排泄型湖泊,這種地下水-湖水系統(tǒng)的作用關(guān)系為鈣華沉積于湖岸泉水出露帶提供了持續(xù)的動力學(xué)條件。3:闡明了鈣華沉積的水化學(xué)基礎(chǔ)鈣華湖泊湖水類型為Cl-Na型,Ca~(2+)含量低,CO_3~(2-)+HCO_3~-含量高;湖四周地下水類型以Cl-S04-Na型、Cl-CO_3-Na型為主,CO32-+HCO3-含量低,Ca~(2+)含量較高;多數(shù)水樣方解石、文石飽和指數(shù)大于0,為鈣華沉積提供了基本條件。4:揭示了湖岸鈣華沉積機制沉積機制包括地下水與湖水的混合效應(yīng)、泉水脫氣效應(yīng)、蒸發(fā)濃縮效應(yīng),沉積過程受到溫度效應(yīng)、pH值、二氧化碳分壓(PCO_2)等因素的影響。根據(jù)碳酸鈣沉淀量大小,上述效應(yīng)對鈣華沉積的重要性程度為:混合效應(yīng)脫氣效應(yīng)蒸發(fā)濃縮溫度效應(yīng),沉淀能力對比為106.22.41。沉積環(huán)境中PCO_2降低,水體pH值升高,水動力條件的增大,均有利于鈣華形成。沉積時CO_2氣體主要來自大氣以及土壤中生物的呼吸和分解作用;沉積鈣質(zhì)主要來自于地下水對古湖沉積物與風積砂的溶濾。
[Abstract]:There is no conclusion on the origin of calcareous blooms and their climatic and environmental significance. The investigation on the basic characteristics of calcareous blooms in desert lakes and their causes are rare. As a product of hydrochemistry, the study of the deposition mechanism of Caohua can provide new evidence for other related scientific research work, such as lake evolution, climate evolution, groundwater recharge source and so on. Based on the project of "1: 250 000 Hydrogeology Survey of Badain Jilin Desert and its surrounding areas" (number: DD20160295), this paper carries out lake water sampling and groundwater sampling analysis for 7 lakes with large distribution scale of calcareous water in the desert. With the emphasis on Cheigre Lake, the cavertine core, which is 3.8 meters deep along the shore of the lake, is drilled. By means of SEM scanning, energy spectrum analysis, rock and ore testing, uranium dating and so on, the Calciferous sedimentary period and its geochemical characteristics are determined. In order to study the mechanism of travertine deposition, laboratory simulation experiments were carried out, focusing on the influence of temperature effect and mixing effect during deposition process. At the same time, with the help of PHREEQC software, the forward and reverse models were established to study the pH value and PCO_2, temperature in the deposition process. Finally, the material source and genetic mechanism of Cegler travertine deposition are elucidated by the influence of mixed ratio and other factors. The main achievements of this paper are as follows: 1. The distribution and geochemical characteristics of the calcareous blooms are summarized, which are mainly located in the outburst zone of the spring water along the lake bank and its adjacent areas. The CaO content of the samples is more than 50, and the crystalline morphology is mainly hexagonal, triangular-shaped calcite and acicular dolomite, which reflects the low temperature sedimentary environment. The average values of carbon and oxygen isotopes are 未 13C=1.31 鈥，

本文編號：2371614