【作者】 关秀宇；

【导师】 田友萍；

【作者基本信息】 中国地质大学（北京） ， 第四纪地质学， 2010， 硕士

【摘要】 贵州省黄果树地区发育有大规模的地表钙华,研究该地区钙华的成因机制可以了解钙华景观的形成和发展规律,对钙华风景区的维护、管理提供有力的科学依据。此外,利用钙华微层记录的高分辨率气候信息可以重建该地区古气候变化模型,从而有助于我们认识气候演变的趋势。本文从贵州黄果树水文地质条件出发,主要采用水文地球化学方法、稀土元素化学方法、微量元素地球化学方法对该地区的水化学特征、钙华微层稀土元素变化规律及Mg/Ca比值进行综合分析,从而取得以下成果:(1)贵州黄果树地区钙华沉积主要受微地貌条件、水质类型、生物活动、水动力效应的控制。研究区生物量较为丰富,地表水系所含化学元素主要受控于三叠系可溶性岩组,水质类型呈HCO3.SO4-Ca型。9处采样点中,唯有冒水塘表水下潜处因受地形影响,钙华处于溶蚀状态。总体上,黄果树地区在现生条件下,是有利于钙华体生长的。(2)黄果树钙华各微层轻重稀土高度相关(R2=0.988),说明轻重稀土元素之间的化学分离受到抑制,氧化还原条件微弱。从总体上看,当时钙华的沉积环境可能较为干旱。(3)钙华中轻重稀土存在微弱分馏,这种轻重稀土元素的分馏可以用LREE/HREE的比值来表示。在湿润的气候条件下,有利于重稀土元素的迁移,进而导致LREE/HREE的比值相对降低;在干旱的气候环境,轻重稀土元素间的分离会受到一定程度的抑制,并使得LREE/HREE的比值升高。(4)钙华微层中Mg/Ca比值与LREE/HREE比值相关性较好(R2 = 0.60),呈正相关。根据LREE/HREE的比值变化,可以反映各微层代表的沉积时代降水波动的规律,分析认为将Mg/Ca比值作为贵州黄果树地区古气候重建的替代指标是可行的。(5)通过LREE/HREE值、Mg/Ca值波动所指示的该地区降水量变化特征,结合稀土元素总量变化(REE)特点,总结贵州黄果树地区古气候特征为:热干—暖干—冷湿—热干—暖湿—暖干。更多还原

【Abstract】 Large scale of surficial tufa developed in Huangguoshu area of Guizhou province. Studying the contributing mechanism, we can understood tufa’s conformation and evolvement discipline, which provided scientific foundation for tufa landscape in maintenance and management. Furthermore, tufa annual laminations had the character of high resolution in recording climate information, taking advantage of this, we can reconstructed the palaeoenvironment in Huangguoshu area, and also help us for forecasting the trend of climate change.Based on the hydrogeology conditions, hydrochemical methods, rare earth element and trace element geochemical methods were used to analyze the hydrochemical characteristics, the rule of REE in tufa laminations and Mg/Ca ratio, then the results yield as flow:1. The tufa deposit in was affected by tiny physiognomy, water trait, biological action and hydrodynamic conditions. The quantity of living creature in water was rich, and chemical compositions of the surface water were controlled of fusible lithostrome in Triassic period, so the hydrochemical facion in Huangguoshu area was HCO3.SO4-Ca type. In nine sampling points, only the tufa where developed in Maoshuitang was dissolving, because of physiognomy affect. Totally, the environment in Huangguoshu area was still helpful in precipitation and formation for the tufa at present.2. The LREE was positively correlated with HREE(R2=0.988).It showed the chemical separate between LREE and HREE was restrained, and week redoxomorphism. The sedimentary condition may be a little dry at that time in all.3. There is low fractionation between LREE and HREE, and it can be denoted with the ratio of LREE/HREE. It was helpful with HREE migrate in wet climate environment, then resulted in lower LREE/HREE ratio. On the contrary, in dry environment the LREE/HREE ratio will get higher.4. In tufa annual laminations, Mg/Ca ratio was good at correlating with LREE/HREE ratio (R2 = 0.60)in positively. According to LREE/HREE ratio change, we can know about the rule of rainfall variety that reflect in every annual lamination. The result was that Mg/Ca ratio can served as indicator for reconstructing the palaeoenvironment in Huangguoshu area Guizhou province.5.With the LREE/HREE ratio and Mg/Ca ratio change implied the feature of rainfall variety, beside with the REE variety characteristic, the research generalized the feature of palaeoenvironment in Huangguoshu area, that was hot and drought, warm and drought, cold and moist, hot and drought, warm and moist, warm and drought.更多还原