Tracing effects of decalcification on solute sources in a shallow groundwater aquifer, NW Germany     

Bettina A. Wiegand   《Journal of Hydrology》2009,378(1-2):62-71

δ⁸⁷Sr values and Ca/Sr ratios were employed to quantify solute inputs from atmospheric and lithogenic sources to a catchment in NW Germany. The aquifer consists primarily of unconsolidated Pleistocene eolian and fluviatile deposits predominated by >90% quartz sand. Accessory minerals include feldspar, glauconite, and mica, as well as disperse calcium carbonate in deeper levels. Decalcification of near-surface sediment induces groundwater pH values up to 4.4 that lead to enhanced silicate weathering. Consequently, low mineralized Ca–Na–Cl- and Ca–Cl-groundwater types are common in shallow depths, while in deeper located calcareous sediment Ca–HCO₃-type groundwater prevails. δ⁸⁷Sr values and Ca/Sr ratios of the dissolved pool range from 7.3 to −2.6 and 88 to 493, respectively. Positive δ⁸⁷Sr values and low Ca/Sr ratios indicate enhanced feldspar dissolution in shallow depths of less than 20 m below soil surface (BSS), while equilibrium with calcite governs negative δ⁸⁷Sr values and elevated Ca/Sr ratios in deep groundwater (>30 m BSS). Both positive and negative δ⁸⁷Sr values are evolved in intermediate depths (20–30 m BSS). For groundwater that is undersaturated with respect to calcite, atmospheric supplies range from 4% to 20%, while feldspar-weathering accounts for 8–26% and calcium carbonate for 62–90% of dissolved Sr²⁺. In contrast, more than 95% of Sr²⁺ is derived by calcium carbonate and less than 5% by feldspar dissolution in Ca–HCO₃-type groundwater. The surprisingly high content of carbonate-derived Sr²⁺ in groundwater of the decalcified portion of the aquifer may account for considerable contributions from Ca-containing fertilizers. Complementary tritium analyses show that equilibrium with calcite is restricted to old groundwater sources.  相似文献   

Paleotemperature variations at Lake Caohai,southwestern China,during the past 500 years:Evidence from combined δ~(18)O analysis of cellulose and carbonates     

ZHU ZhengJie  CHEN JingAn  ZENG Yan 《中国科学:地球科学(英文版)》2014,57(6):1245-1253

The oxygen isotopic values of aquatic plant cellulose and carbonates in Lake Caohai sediments were measured using a continuous flow isotopic ratio mass spectrometer(CF-IRMS).Because of predictable oxygen isotopic fractionation between cellulose and its source water,the oxygen isotopic composition of paleo-lake water has been established quantitatively.Combined oxygen isotopic values of cellulose and carbonates were used in the‘Craig’equation to determine paleotemperatures and their variation in the lake during the past 500 years.Results show that the paleotemperature trend correlates well with meteorological records from Weining.There are four notable cold intervals at Lake Caohai over the past 500 years,namely 1540–1570AD,1670–1715AD,1780–1870AD and 1900–1930AD,and the former three cold intervals have been observed in the conventional Little Ice Age(LIA).These cold periods at Lake Caohai correspond well with those recorded from tree ring,peat,and ice core data from adjacent regions,particularly temperature those inferred fromδ18O of peat cellulose from Hongyuan Southwestern China.The trend in paleotemperature variations at Lake Caohai are also consistent with both the change of Indian summer monsoon,derived fromδ18O values of a stalagmite in Dongge,and a recorded shift in solar activity.The findings of this study illustrate that coupled analysis ofδ18O values of cellulose and carbonates from lake sediments may be used as a paleotemperature proxy.These results also provide further evidence of the existence of LIA in southwestern China.  相似文献   

塔里木盆地西克尔露头区鹰山组古岩溶特征及其储层意义   总被引：2，自引：0，他引：2  

高达  林畅松  黄理力  左璠璠  李浩  耿晓洁 《现代地质》2014,28(1):156-162

鹰山组上段因主要发育岩溶型储层而成为塔里木盆地奥陶系的重要含油气层,但因钻井资料的局限储层特征难以精确揭示。塔里木盆地西缘西克尔地区经历了多期构造运动,发育了多期不整合之下的表生岩溶作用,出露的鹰山组发育丰富的古岩溶现象,为研究鹰山组岩溶储层特征和揭示岩溶储层成因规律提供了良好的条件。通过野外剖面和室内薄片观察和描述,识别出了大型溶洞及其充填物、小型溶孔以及构造裂缝和溶蚀缝等。强烈的表生岩溶作用形成的溶洞和角砾岩可直接形成溶洞型储层;小型溶孔广泛发育,常与溶蚀缝伴生形成孔洞型或缝洞型储层;多期构造裂缝叠加在岩溶储层之上,能显著提升储层的渗透性。结合岩相分析表明,颗粒灰岩中溶孔的发育密度要明显高于泥晶灰岩;同时溶蚀缝和构造裂缝也更易发生在颗粒含量高的灰岩中,从而形成裂缝型和孔洞缝复合型有利储层。  相似文献   

海相碳酸盐台地含钾层段旋回地层学响应和识别 ——以川中广安地区三叠系为例   总被引：1，自引：0，他引：1       下载免费PDF全文

龚大兴  周家云  陈科贵  李春梅  李萌 《高校地质学报》2014,20(2):230

识别海相碳酸盐岩台地深部的成盐聚钾层段,主要依靠测井解译和钻井取芯验证。连续沉积的碳酸盐岩台地具有旋 回性,记录着海相碳酸盐岩随古海平面旋回变化的信息。因此,利用测井数据模拟台地高频沉积旋回叠加样式,反演古海 平面旋回,寻找海退地层序列的低水位沉积体系,进而快速锁定成盐聚钾层段的方法值得探索。文中以四川盆地川中广安 地区三叠系为例,以等间距连续测量的自然伽马测井数据为对象,运用数值模拟技术,有效识别了三叠纪沉积时期的高频 沉积旋回,并根据高频沉积旋回的累积厚度偏差变化,反演了古海平面的变化趋势,判断广安地区嘉陵江组 5 段至雷口坡 组 1 段第 1 亚段沉积期,相对海平面长期处于较低水位,是最有利的成盐聚钾期,这与基于钻井岩芯划分的富钾层段极为吻 合,表明这种方法能够有效识别碳酸盐岩台地含钾层段。  相似文献   

从水井岩大型滑坡表面高温降解喷出物特征到汶川地震天然气体溢出爆炸模型   总被引：1，自引：0，他引：1  

尚彦军  刘嘉麒  夏燕青  刘大安  雷天柱  张路青 《吉林大学学报(地球科学版)》2014,44(1):230

汶川大地震中XI级烈度区内水井岩滑坡现场等地爆炸声、特大型滑坡现场巨大环形坑和远距离抛射碎石等记录和现象,需给出科学解释。在地震发生后多次现场地质调查和走访、样品采集和多项分析测试及其结果比较等基础上,对主中央断裂F₂控制的下盘陈家坝水井岩大型滑坡体上环形坑周边不同距离范围内散落烧焦残留的硅酸盐和碳酸岩等采样后,开展了物质成分和微观结构分析。结果发现：与原生溶蚀灰岩、薄层煤岩结构和有机质成分不同,这些抛散在滑体表面的样品中富含经强烈高温作用的块石,一些成分以锰碳酸盐岩等为主的暗棕色样品中稠环芳烃是其经历过强烈热作用过程而使有机质发生环化芳构化反应的结果,即样品经过了强烈热降解作用,显示其形成时出现强烈热作用过程和高温裂解现象。结合本区地质构造特征和煤层气分布情况、地震后实施的汶川地震带深钻在穿越主中央断裂带F₂深度处监测到余震过程中甲烷含量异常增高、东河口地震遗址公园发现温泉及天然气溢出等资料和研究结果,讨论了地震诱发的富含甲烷的天然气爆炸,其加剧或伴生着地震次生地质灾害。由此推测：与碳质岩或煤系共存的喀斯特溶洞中封闭煤层气在地震过程中突溢和爆炸燃烧,叠加或放大了地震作用,结果在滑坡堆积体表面残留了多处环形爆炸坑,引发了一些岩块大规模长距离水平抛撒等。研究结果对监测和认识发震断层带在地震过程中天然气爆炸诱发和加剧滑坡灾害有重要意义。  相似文献   

南海北部甲烷渗漏的沉积地球化学指标(Sr/Ca和Mg/Ca)识别     

杨克红  初凤友  叶黎明  章伟艳  许冬  朱继浩  杨海丽  葛倩 《吉林大学学报(地球科学版)》2014,44(2):469-479

自生碳酸盐矿物是揭示甲烷渗漏过程及其周期性变化的重要指标。为了方便、快速地识别出自生碳酸盐矿物,在探讨了前人建立的端元组分模型(文石、高镁方解石、生物成因方解石和碎屑)在我国南海北部适用性的基础上,利用沉积物全样中Sr/Ca和Mg/Ca值计算了南海北部神狐海域两支沉积物柱状样中自生碳酸盐矿物的质量分数,计算结果表明,在不同沉积深度均有含量不等的自生碳酸盐矿物。这一结果被X射线衍射结果和沉积物中存在晶形完好的自生高镁方解石和文石矿物所验证,表明利用前人建立的端元组分模型计算的结果具有可靠性。自生碳酸盐矿物的出现显示该海域深受甲烷渗漏作用影响。利用地球化学指标(Sr/Ca和Mg/Ca)获得的自生碳酸盐矿物含量垂向变化显示该区域甲烷渗漏具有强弱交替的周期变化。运用端元组分模型来获取沉积物柱状样中自生碳酸盐矿物的高分辨率剖面,从而识别甲烷渗漏信息非常方便,在大范围寻找甲烷渗漏和天然气水合物方面具有较大潜力。  相似文献   

顺北1井区奥陶系断溶体油藏岩溶发育特征     

伍齐乔  李景瑞  曹飞  梁彬  朱现胜  张庆玉  淡永 《中国岩溶》2019,38(3):444-449

随着塔里木盆地超深层碳酸盐油气藏勘探工作的深入,在塔河外围斜坡区发现了断溶体油藏岩溶储层新类型。顺北1井区是中石化顺北油田主力产区,为典型断溶体油藏。该区先后经历一间房组顶面准同生岩溶作用、良里塔格组顺层-断裂控储岩溶作用、前志留系桑塔木组覆盖埋藏岩溶作用和海西晚期二叠系热液岩溶改造4个期次。其中对本区一间房组顶面以下80~120 m放空漏失段起控制作用的为良里塔格组顺层-断裂控储岩溶期。同时研究认为顺北1井区断溶体油藏发育的必要条件是发育区域大型走滑-拉分断裂,拉分段的杂乱反射体横向规模大,纵向发育深度深,是优质高产储集体;强挤压逆冲段杂乱反射呈夹板状,横向延展范围较窄,储集空间次之。   相似文献   

Sedimentary Organic Carbon Mineralization and Its Contribution to the Marine Carbon Cycle in the Marginal Seas     

Yonghua Zhang  Zijun Wu 《地球科学进展》2019,34(2):202-209

Continental margin sediments are important ocean carbon repository, and the internal carbon cycle is mainly driven by the mineralization processes of sedimentary organic matter. Most organic carbon is transformed to Dissolved Inorganic Carbon (DIC) by mineralization processes after being delivered to continental margin sediments, and DIC from pore water diffuses into the upper water column and participates in the ocean carbon cycle. At the same time, some DIC combines ions such as Ca²⁺ and Mg²⁺ and precipitates as authigenic carbonate minerals so that carbon is stored in the deposits. Based on the biogeochemical study of the mechanism and efficiency of organic matter burial, we discussed the interaction among sulfate reduction, methanogenesis and anaerobic oxidation of methane, and the effect of organic mineralization on the formation of authigenic carbonate. By reviewing the above-mentioned aspects, we can obtain a better understanding of the role of continental margin sediments in the global carbon cycling budgets as well as its climate and environmental effects.  相似文献   

大别山北麓白石坡银矿区花岗斑岩锆石U-Pb年龄、地球化学和Sr-Nd-Hf同位素组成及其地质意义     

朱江  陕亮  吴越  唐相伟  彭三国  彭练红 《地学前缘》2019,26(5):317-329

白石坡银矿床是大别山地区具代表性的中型银矿床,已探明银储量219.8 t。银矿体与矿区花岗斑岩空间关系密切。为深化理解其成矿地质背景,对白石坡花岗斑岩进行了详细的岩相学观察、锆石U-Pb同位素测年、岩石地球化学和Sr-Nd-Hf同位素研究。通过激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)分析,获得花岗斑岩锆石U-Pb同位素年龄为(142±2) Ma(MSDW=1.9),表明其形成于早白垩世。岩石具较高的SiO2含量(73.94%~76.14%)和富K2O(7.46%~9.55%)等特点,总体属于强过铝质(A/CNK=1.07~1.45)、高钾钙碱性系列,具高分异花岗岩特征;岩石富集轻稀土((LREE/HREE)N=10.88~12.89),具中等Eu负异常,并具有较低的Sr、Y、Yb含量。岩石锶同位素初始比值ISr为0.714 762~0.715 890,钕同位素εNd(t)值约为-13.8,两阶段Nd模式年龄TDM2=2.06~2.05 Ga。锆石εHf(t)值集中于-16.6~-13.5,两阶段Hf模式年龄TDM2=1.98~1.81 Ga。岩石地球化学和Sr-Nd-Hf同位素特征共同揭示,该花岗斑岩可能是扬子陆壳北缘古老地壳物质重熔演化的产物。白石坡花岗斑岩及相关银矿床形成于白垩纪加厚下地壳拆沉之前地壳持续挤压加厚环境,与陈棚组火山活动不存在直接联系。  相似文献   

塔里木盆地巴楚凸起H气田奥陶系裂缝 主控因素及演化序列研究     

李树博  姜伟  张效恭  王爱霞 《地质力学学报》2019,25(4):518-526

塔里木盆地巴楚凸起H气田奥陶系储层是低孔低渗裂缝型碳酸盐岩储层,裂缝系统作为储层渗流通道,其空间分布和主要控制因素复杂,具有多期次叠加和演化的特征。文章采用岩心描述、镜下观察、成像解释等手段分析H气田奥陶系碳酸盐岩裂缝发育特征,明确裂缝主要控制因素,建立了裂缝演化序列。结果表明:巴楚凸起H气田奥陶系以剪切缝为主,张性缝次之,张剪缝最少,裂缝发育的主要控制因素为断层、褶皱及岩性等,与断层相关的裂缝主要发育在距断层460 m的范围内;地层变形程度越强,裂缝越发育;裂缝发育程度还受岩性的控制,灰岩的粒径或晶粒越大,构造裂缝越发育。根据已有碳氧同位素测试研究成果,并结合岩心观察发现:H气田奥陶系构造裂缝至少经历了三期演化活动,分别为加里东运动中期少量低角度北东东向和北北西向剪切缝发育期,海西运动晚期中-高角度北西西向张性缝和北东东向、北西向张剪缝以及南北向、北东向中-高角度剪切缝发育期,喜马拉雅运动早期大量高角度北东东向、北北东向剪切缝发育期,主要造缝期为喜马拉雅运动早期。   相似文献