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

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.     

利用碳酸盐岩的Fe/Mn比值恢复海洋的氧化还原状态

碳酸盐岩的Fe/Mn元素比值,作为一项新的地球化学指标,可以用于恢复海洋的氧化还原状态.在氧化条件下,Fe³⁺和Mn⁴⁺均不可溶,因此氧化海水中的溶解Fe和Mn的含量均很低.Fe³⁺和Mn⁴⁺在还原条件下可以被细菌还原为可溶的Fe²⁺和Mn²⁺,而氧化还原电位的计算表明,Mn⁴⁺的还原要早于Fe³⁺的还原,因此细菌的Mn还原过程发生在沉积物的更浅层.可溶的Fe²⁺和Mn²⁺向上扩散到海水中,替代碳酸盐岩晶格里的Ca²⁺,因此碳酸盐岩晶格中的Fe²⁺和Mn²⁺的含量受控于来自沉积物孔隙水的扩散,而后者又与水岩界面的氧化还原状态相关.因此可以预测,随着海水变得逐渐缺氧,碳酸盐岩中的Fe/Mn比值会逐渐增高.为了验证这一假说,我们分析了中元古代高于庄组白云岩的Fe/Mn比值.研究发现,几乎所有的样品的Fe/Mn比值介于20～30之间,显著高于泥盆纪末期深水碳酸盐岩和浅水台地碳酸盐岩的Fe/Mn比值.高于庄组碳酸盐岩高的Fe/Mn比值一方面可能指示了中元古代低的大气氧气浓度和海洋的广泛缺氧,也可能反映了白云岩形成于缺氧的沉积物空隙水里.     

Ar/Ar dating of central European K–Mn oxides — a chronological framework of supergene alteration processes during the Neogene

K-bearing Mn oxides may potentially constitute useful objects for isotopic dating of ore-forming events. A comprehensive ⁴⁰Ar/³⁹Ar study performed on supergene K–Mn oxides sampled from different sub-alpine mountain terrains in Germany and France has been undertaken. The objective of these investigations was to provide new insight into how and when these secondary Mn accumulations may have formed. Developed in supergene environments at the expense of Mn²⁺/Mn³⁺-bearing precursor minerals, the Mn⁴⁺ oxides occur either as pseudomorphic ores or as cavity-fillings and linings.

The isotopic ages range from 25 to 1 Ma, indicating intense chemical weathering, especially during the Miocene and Pliocene. It is yet too early to decide whether the age range represents a more or less continuous process or distinct weathering episodes. Formation of supergene Mn oxides may result from combined climatic and tectonic factors: local uplift, exhumation, and associated fracturing of rocks provided fresh mineral surfaces for percolating meteoric fluids that induced subsequent weathering under warm–temperate to subtropical conditions.     

疏勒河源区水化学特征及其控制因素分析

以疏勒河源区为研究区,自2018年12月至2019年11月分别采集河水、泉水和雪样样品44个、4个和7个,综合运用Piper三线图、Gibbs图、离子比值法定性分析不同水体水化学特征及控制因素,利用质量平衡法（正向地球化学模型）量化不同来源对不同季节河水水化学成分的贡献率。结果表明：疏勒河源区不同水体水化学特征存在差异,TDS含量为泉水>河水>冰川融水>雪水,河水水化学类型冬季为HCO₃^--Mg²⁺?Ca²⁺型,春季为HCO₃^--Ca²⁺?Mg²⁺?Na⁺型,夏、秋季均为HCO₃^--Ca²⁺?Mg²⁺型,泉水和雪水分别为HCO₃^--Ca²⁺?Mg²⁺型、HCO₃^--Ca²⁺型;受多种因素共同影响,不同季节河水主离子时空变化均存在差异;河水和泉水水化学组成受岩石风化作用控制,主离子来源于以白云石为主的碳酸盐岩风化、硅酸盐岩风化和盐岩、石膏、硫酸盐矿物等蒸发岩溶解;正向地球化学模型计算结果表明冬春季河水阳离子主要来源于硅酸盐岩风化溶解,夏秋季碳酸盐岩对河水阳离子贡献率大于硅酸盐岩,总体河水阳离子主要来源于碳酸盐岩和硅酸盐岩风化。     

Stable Strontium Isotopic Fractionation During Chemical Weathering in Drainage Basins: Mechanisms and Applications

The new non-traditional stable strontium (Sr) isotope has aroused great attention from academic scholars in terms of the continental weathering and marine Sr cycle. The analytical precision of stable Sr isotope using mass spectrometry is better than 0.03‰. The compiled δ⁸⁸/ ⁸⁶Sr values vary from -3.65‰ to 1.68‰ in natural reservoirs. Recent findings indicate that multiple processes can cause stable Sr isotope fractionation in Earth surface, including the incongruent dissolution of primary minerals, the formation and adsorption of secondary minerals, the precipitation of calcium carbonate, and the biological cycling. These processes lead to higher δ⁸⁸/ ⁸⁶Sr in the liquid phase and lower δ⁸⁸/ ⁸⁶Sr in the solid phase, and thus result in different geochemical behavior of stable Sr isotopes in water and sediment during the weathering processes. The δ⁸⁸/ ⁸⁶Sr values of river sediment decrease with the increase of weathering intensity, which has the potential to indicate chemical weathering intensity. Meanwhile, further study on the fractionation mechanisms and constraints of stable Sr isotopes in river water plays an important role in tracing chemical weathering processes within the watershed, which will lead to a better understanding of the global ocean Sr cycle.     

表生环境中镁同位素的地球化学循环

近些年表生环境中镁同位素分馏取得了一系列重要研究进展,这些新认识为深入理解表生环境中镁同位素地球化学循环奠定了基础。表生环境中镁同位素的地球化学循环主要涉及风化、河流搬运、碳酸盐沉淀、水岩反应等重要地质过程。风化过程中镁同位素发生显著分馏,硅酸盐风化产物中富集重的镁同位素,轻的镁同位素易进入水体。河流搬运过程中,镁同位素不发生分馏,但外源输入可能影响水体的镁同位素组成。河水汇入海洋后,碳酸盐沉淀过程可导致轻的镁同位素以碳酸盐的形式从海水中移出。在海底高温水岩反应过程中,海水中绝大多数的镁(80%~87%)都进入岩石,循环后的热液可能富集轻的镁同位素。海底低温水岩反应过程中海水的镁可以进入岩石并形成次生矿物,此过程的镁同位素分馏主要与次生矿物的形成有关。此外,海水中的镁易与黏土矿物发生交换反应,此过程黏土矿物倾向于吸附轻的镁同位素。总之,在表生环境中上地壳的镁(δ26Mg约为-0.22‰)经历风化作用、河流搬运、海洋贮存,最终以碳酸盐岩(δ26Mg一般小于-1‰)或与玄武岩发生反应的形式重新回到岩石圈。     

含油气岩系中含铵矿物研究现状与前景

研究表明,在含油气岩系中,当有机质发生热演变而成熟、并逐渐向烃类转变的整个过程中,氮主要以NH+₄的形式释放出来而进入孔隙流体与周围介质 (成岩矿物 )相互作用,最重要的机制是NH+₄可取代粘土矿物 (如伊利石,I/S混层矿物等 )层间的K+而参与成岩作用,形成含铵矿物,这一过程中氮的地球化学性质发生了重要变化,含铵矿物中固定 -NH4的富集状况与有机质成熟度及烃类运移有关。通过研究成岩和油气生成、运移、聚集过程中氮的岩石地球化学行为及其控制因素,可将固定 -NH₄作为有机质成熟度和油气运移路径的一种新的、有意义的示踪剂。     

额尔齐斯河源春季水化学及稳定同位素特征研究

基于2018年4月额尔齐斯河源至富蕴段的河水样品, 综合运用Gibbs图、 Piper三线图、 相关矩阵分析等方法对河水中主要的化学离子、 pH值、 电导率、 TDS和氢、 氧稳定同位素等物理化学指标进行了分析。结果表明： 额尔齐斯河源春季河水呈弱碱性, TDS平均值为72.02 mg·L^-1, 整体属于低矿化度水。河水中主要离子浓度序列为HCO₃^- > SO₄^2- > Ca²⁺ > Na⁺ > Cl^- > NO₃^- > Mg²⁺ > K⁺, 其中HCO₃^-、 SO₄^2-和Ca²⁺是最主要的阴阳离子。水化学类型从库依尔特河的HCO₃^--Ca²⁺型转变为额尔齐斯河富蕴段的（HCO₃^-, SO₄^2-）-Ca²⁺型。从源区至富蕴段各离子含量整体呈增大趋势, 但其增加过程受到复杂因素的影响而出现差异。河水离子主要受水-岩风化作用控制, 且以碳酸盐岩（石灰岩、 白云岩）为主的风化水解是离子的主要来源, 其次是长石类矿物的风化, 还包括下游人类活动的离子输入等。δD和δ¹⁸O沿程逐渐增大, 在下游出现了富集现象。     

Dissolved load of the Loire River: chemical and isotopic characterization

The Loire River, with one of the largest watersheds in France, has been monitored just outside the city of Orleans since 1994. Physico-chemical parameters and major and trace elements were measured between 2-day and 1-week intervals according to the river flow. The sampling site represents 34% of the total Loire watershed with 76% silicate rocks and 24% carbonate rocks.

Elements are transported mainly in the dissolved phase with the ratio of total dissolved salts (TDS) to suspended matter (SM) ranging between 1.6 and 17.4. Chemical weathering of rocks and soils are thus the dominant mechanisms in the Loire waters composition. The highest TDS/SM ratios are due to dissolved anthropogenic inputs. The database shows no link between NO₃⁻ content and river flow. The Na⁺, K⁺, Mg²⁺, SO₄²⁻, and Cl⁻ concentrations are seen to decrease with increasing discharge, in agreement with a mixing process involving at least two components: the first component (during low flow) is concentrated and may be related with input from the groundwater and sewage station water, the second component (during high flow) is more dilute and is in agreement with bedrock weathering and rainwater inputs. A geochemical behaviour pattern is also observed for HCO₃⁻ and Ca²⁺ species, their concentrations increase with increasing discharge up to 300 m³/s, after which, they decrease with increasing discharge. The Sr isotopic composition of the dissolved load is controlled by at least five components — a series of natural components represented by (a) waters draining the silicate and carbonate bedrock, (b) groundwater, and (c) rainwaters, and two kinds of anthropogenic components.

The aim of this study is to describe the mixing model in order to estimate the contribution of each component. Finally, specific export rates in the upper Loire watershed were evaluated close to 12 t year⁻¹ km⁻² for the silicate rate and 47 t year⁻¹ km⁻² for the carbonate rate.     

海洋沉积物早期成岩作用研究进展

海洋沉积物的早期成岩作用是其沉积和埋藏过程中发生的一系列生物、物理和化学变化,其驱动力为有机质的降解,根据反应自由能大小,参与反应的氧化剂顺序为:O₂>NO3->Mn4+>Fe3+>SO42-。随着埋深增加,形成一系列氧化—还原化学带,并推动着海底沉积物中部分自生矿物的生成及C、N、S、Fe、Mn等元素的地球化学循环和同位素分馏。一系列有机质降解反应会改变原生沉积物中保存的地球化学信息,对古环境和古气候的研究具有重要意义。在早期成岩作用过程中,有机质降解产生的碳酸根离子和钙离子、亚铁离子结合会形成方解石、文石、菱铁矿等碳酸盐矿物。硫酸盐还原产生的还原态硫最终与亚铁离子形成黄铁矿。此外,目前常用于氧化还原环境重建的代用指标有:1）Fe组分;2）C_org/P比值;3）氧化还原敏感微量元素;4）Mo、U同位素。围绕海洋沉积物早期成岩作用中的矿物和元素地球化学行为,评述了早期成岩作用过程中有机质降解反应机制,探讨了反应进程中发生的元素地球化学循环和同位素分馏,以及相伴生的碳酸盐矿物和黄铁矿等自生矿物的形成机理。最后,总结了现有研究的不足,并对未来的研究方向进行了展望。     

稀有金属矿物溶解度对花岗伟晶岩成矿作用的制约

花岗伟晶岩型矿床是稀有金属矿床重要的类型之一。在花岗伟晶岩中,稀有金属元素Li、Be、Nb和Ta主要以独立矿物的形式存在,前人对稀有金属独立矿物在硅酸盐熔体中的溶解度及其影响因素展开了系统研究。本文综合分析了已有的实验数据,其结果表明,影响稀有金属独立矿物溶解度最为重要的2个参数是温度(T)和铝饱和指数(ASI)。因此本文建立了稀有金属独立矿物,尤其是铌锰矿和钽锰矿溶解度,与温度(T)和铝饱和指数(ASI)之间的定量关系: lg [w(Li)/10^-6]=-0.37×[1 000/(T/K)]+4.56,R²=0.44 lg [w(BeO)/10^-6]=-4.21×[1 000/(T/K)]+6.86,R²=0.91 lg [K_sp(Nb)/(mg²·kg^-2)]=-(2.86±0.14)×ASI_(Mn+Li)-(4.95±0.31)×[1 000/(T/K)]+(4.20+0.28),R²=0.86 lg [K_sp(Ta)/(mg²·kg^-2)]=-(2.46±0.11)×ASI_(Mn+Li)-(4.86±0.30)×[1 000/(T/K)]+(4.00+0.30),R²=0.80 式中,温度T为热力学温度,ASI_(Mn+Li)(ASI=Al₂O₃/(CaO+Na₂O+K₂O+Li₂O+MnO),摩尔分数比)和T的适用范围分别为0.6~1.2和1 073~1 373 K的范围内。上述公式为估算硅酸盐熔体中稀有金属含量提供了便利,为量化花岗伟晶岩成矿模型提供了基础。 稀有金属独立矿物溶解度随温度降低和铝饱和指数的增加而急剧降低,因此,在岩浆演化过程中,由岩浆侵位、分离结晶以及流体作用等因素引起的岩浆温度降低和铝饱和指数的增加,是导致稀有金属独立矿物结晶的主要机制。     

祁连山黑河源区八一冰川-黄藏寺段河水水文地球化学特征

黑河源区河水水文地球化学特征的研究有助于了解黑河源区河水沿流域水质变化概况,对黑河源区生态环境的保护具有积极意义。以黑河源区干流为研究对象,对河水进行取样检测,结果显示：河水化学组成以K⁺、Na⁺、Ca²⁺、Mg²⁺和Cl^-、NO₃^-、HCO₃^-、SO₄^2-为主。通过聚类分析、舒卡列夫分类和Piper三线图分析发现主要离子中,阳离子主要来源于石灰岩风化产物,SO₄^2-主要来源于蒸发岩矿物风化产物和人类活动,HCO₃^-主要来源于纯碳酸盐风化产物。通过对重金属污染调查发现,V、Co、Cu、Pb、Cr、Mn和Zn含量较高,矿山开采是重金属污染的主要来源。     

原生硅酸盐矿物风化产物的研究进展——以云母和长石为例

研究云母和长石等原生硅酸盐矿物的风化速率和风化产物对于深入理解土壤发生过程、营养元素循环以及全球气候变化具有重要的理论意义。本文从自然风化、人工化学风化和生物风化3方面总结了原生硅酸盐矿物风化作用及其产物的特点，重点阐述了微生物参与下的生物风化作用和生物矿化作用及其意义。野外观察和室内实验研究结果表明，微生物可以加速矿物的分解，而且其细胞表面及其产生的胞外多聚糖可以作为次生矿物成核的模板。     

深层碎屑岩自生矿物成因机理及其对储层物性的影响——以渤海歧南断阶带侏罗系为例

自生矿物特征和成因机理对深层碎屑岩储层物性具有重要影响。以渤海海域歧南断阶带侏罗系为例,通过岩心、薄片、扫描电镜、电子探针、同位素、包裹体、X衍射分析等技术手段,对研究区侏罗系深层碎屑岩储层自生矿物的类型、特征、成因机理及对优质储层发育的控制作用进行研究。结果表明：研究区侏罗系碎屑岩属于中孔-低渗储层,非均质性强;主要自生矿物类型为硅质矿物、碳酸盐矿物、黏土矿物3类;早期形成的硅质石英衬垫和碳酸盐胶结物控制了孔隙的发育和演化,沿颗粒表面分布的早期硅质石英衬垫有效抑制了后期石英加大生长,并增强了岩石的抗压能力,有利于原生孔隙保存;早期碳酸盐胶结物增强了储层抗压实能力,并为后期储层遭受溶蚀形成溶蚀孔提供了物质基础,有利于高孔隙储层形成;黏土矿物控制了储层渗透率差异,储层渗透率与自生高岭石体积分数呈正相关性,较高渗透率储层分布于侏罗系中段高岭石富集带内。研究区侏罗系碎屑岩发育原生孔隙体积分数高、微晶石英衬垫发育的Ⅰ类有利储层和粒间溶蚀孔隙较发育、具显著表生成岩作用特点的Ⅱ类有利储层,二者孔隙演化存在明显差异。Ⅰ类有利储层主要受早—中成岩期微晶石英衬垫抗压实作用控制,浅层和深层均可发育高孔隙储层;Ⅱ类有利储层主要受表生期风化淋滤作用控制,可在风化壳附近形成优质储层,整体上Ⅰ类储层物性优于Ⅱ类。     

碳酸盐岩红色风化壳中的氧化铁矿物

氧化铁矿物是碳酸盐岩红色风化壳的主要矿物成分和重要结构单元。运用X射线衍射、透射电镜、扫描电镜、穆斯堡尔谱和电子探针等方法对碳酸盐岩红色风化壳中的氧化铁矿物进行了系统研究。碳酸盐岩红色风化壳中的氧化铁矿物主要有针铁矿、赤铁矿和磁赤铁矿。氧化铁矿物组合、含量和化学成分随成土环境和风化强度在剖面中呈明显的规律性变化,这为碳酸盐岩风化成土作用、红色风化壳成因与环境问题的深入研究提供了重要的矿物学依据。     

The Influence of Allogenic Water and Sulfuric Acid to Karst Carbon Sink in Karst Subterranean River in Southern Hu’nan

Evaluating the impact of allogenic water and sulfuric acid on karst carbon sink not only helps to improve the accurate calculation of soil CO₂ uptake by rock weathering, but also obtains a complete understanding of the global carbon cycle. Groundwater samples were collected from four karst subterranean rivers watershed within different lithology strata in Wushui Basin, upstream of Beijiang Basin, Hunan Province, for revealing the important impact of silicate weathering on hydrochemistry of groundwater. To estimate the contribution of soil CO₂ uptake by silicate weathering to CO₂ uptake by rock weathering, the Galy model was employed in this article. The important impact of sulfuric acid on CO₂ uptake by carbonate weathering resulting from the substitution of carbonic acid by protons from sulfuric acid was investigated. Our results showed that the concentration of Na⁺, K⁺ and SiO₂ in L01,L02 subterranean river with silicate strata in watershed were higher than that in L03,L04 subterranean river without silicate strata in watershed, which implied that the contribution of silicate weathering to Na⁺,K⁺ and SiO₂ was very important in watershed within silicate strata . The changeable equivalent ratio between (Ca²⁺+Mg²⁺) and HCO₃^- was 1.05 to 1.15, and the value of [Ca²⁺+Mg²⁺]/[HCO₃^-+SO₄^2-] was 0.99 to 1.08. The concentrations of Ca²⁺ and Mg²⁺ exceeded the equivalent concentrations of HC₃^-, and the excess of Ca²⁺ and Mg²⁺cations were compensated by SO₄^2-, which suggested that sulfuric acid has an important influence on carbonate dissolution. The contribution of soil CO₂uptake by silicate weathering to CO₂ consumption in L01 and L02 subterranean river were 3.36% and 2.22%, respectively, whereas the contribution in L03, L04 subterranean river were less than 0.50%, indicating that the contribution of soil CO₂ uptake by silicate weathering was important in the subterranean river basin within silicate strata. Due to the contributions made by sulfuric acid, the CO₂ consumption in four subterranean rivers decreased by 4.84%, 4.52%, 6.20%, 9.36%, respectively.     

An Overview of Dissolved and Suspended Matter Fluxes in the Loire River Basin: Natural and Anthropogenic Inputs

The spatial and temporal distributions of major elements were investigated in the surface waters and in associated suspended matter at two sites of the upper Loire basin (Orleans and Brehemont) between 1995 and 1998.According to geochemical and isotopic patterns, the dissolved load appears to result from a process of mixing rainwater inputs, weathering processes of carbonate and silicate bedrock, and agricultural and urban inputs. Natural inputs influence 60% of water chemical composition at both sites. Annual dissolved fluxes were estimated to be 1300 10³ t/y at Orleans and 1620 10³ t/y at Brehemont. Major elements are transported mainly in the dissolved fraction. After correcting for atmospheric and anthropogenic inputs, the silicate specific export rate was calculated to be 11 t/y/km² throughout the basin and the carbonate specific export rate to be from 47 t/y/km² at Orleans to 23 t/y/km² at Brehemont.The suspended load appears to result from at least two particle reservoirs: a silicate reservoir and a carbonate reservoir. The silicate reservoir has a detrital origin, mainly during periods of high flow, while the carbonate reservoir has a detrital origin during periods of high flow and an authigenic origin during periods of low flow. Of the total annual flow of suspended matter, this authigenic material represents 16% at Orleans, 25% at Brehemont and 37% in the fluvial part of the estuary. After correcting authigenic inputs, the specific export rate due to mechanical weathering was estimated to be 8 t/y/km² throughout the Loire basin.     

方解石-白云石-菱镁矿的中远红外光谱学特征研究

利用拉曼光谱和红外光谱研究了方解石、白云石和菱镁矿的光谱学特征,探究了影响三种矿物红外辐射性能的因素。三种矿物的拉曼光谱(Raman)、中红外吸收光谱(MIR)、远红外吸收光谱(FIR)显示随着矿物中镁含量的增大将会影响CO₃^2-的面外弯曲振动(ν₂)、反对称伸缩振动(ν₃)和平面内弯曲振动(ν₄),使各光谱特征峰均向高频端迁移。基于黑体辐射定律以及在80 ℃、400~2 000 cm^-1矿物的辐射能量谱,结果显示方解石、白云石、菱镁矿的发射率依次减少(0.951,0.938,0.895)。三种矿物的红外吸收光谱和发射光谱中的振动位置均受CO₃^2-基频的显著影响,在1 300~1 650 cm^-1均产生宽的低吸收带,该吸收带与CO₃^2-的反对称伸缩振动相关,且吸收带范围(202,236,272 cm^-1)与发射率之间呈负相关关系。因此,当最强化学键的振动出现在发射光谱窄的吸收带范围内会产生相对较高的辐射能和发射率。此外,矿物的晶体结构也会影响发射率,大的离子半径、键长和晶胞体积将降低辐射过程中能量的吸收,增强辐射特性。综上研究结果,方解石、白云石和菱镁矿的拉曼光谱和红外光谱揭示了金属原子的相对质量对光谱学特征的显著影响,其发射率可能受到C—O键的反伸缩振动范围、最强吸收带控制的最低发射率以及矿物晶体结构的共同影响。这项研究呈现了必要的光谱信息和热发射率数据以识别特定的碳酸盐矿物,为类似矿物的光谱特征研究奠定了基础;同时为进一步认识地壳中大量的碳酸盐矿物提供了研究方法,也为地外勘探的深入研究给予相关的理论基础。     

广汉市平原区浅层地下水化学演化及其控制因素

为在广汉市城乡规划过程中提供地下水资源开发利用的基础信息,采用矿物风化系统分析、相关性分析、主成分分析和PhreeQC反向水文地球化学模拟等方法对广汉市平原区的浅层地下水的地下水水化学组分进行分析,确定了浅层地下水的水化学演化及控制因素,完成了地下水资源的质量及时空分布特征分析。分析表明：Gibbs图显示岩石风化主导该区地下水水化学特征,风化过程产生离子和次生矿物又经历水解作用,在矿物风化系统稳定场图中显示水样中铝硅酸盐矿物逐渐趋于溶解,碳酸盐矿物处于饱和状态;PhreeQC反向水文地球化学模拟结果显示在水流模拟路径上主要发生了钙蒙脱石、钾长石溶解和高岭石、石英、钠长石的沉淀,以及Ca-Na₂之间的阳离子交换吸附作用;离子相关性和主成分分析进一步的验证了溶滤作用、蒸发浓缩作用和阳离子交换吸附作用是引起浅层地下水水化学过程和矿物组成改变的主要原因。研究区地下水水质总体不会对人体健康造成不良影响。     

内蒙古二连盆地白音查干凹陷下白垩统腾格尔组热水沉积过程中矿物沉淀顺序及其控制因素*

基于岩心、岩石薄片及元素分析等资料,通过偏光显微镜、定量矿物扫描(QemScan)、电子探针、能谱和流体包裹体分析等技术手段,探讨了二连盆地白音查干凹陷下白垩统腾格尔组热水沉积岩中热水沉积矿物的沉淀顺序。研究区热水沉积矿物主要为铝硅酸盐和碳酸盐,含少量黄铁矿、重晶石、萤石等矿物。这些矿物在空间上具有特定的先后关系或位置关系: (1)在纹层状岩层中,由下到上从铝硅酸盐过渡为碳酸盐。在铝硅酸盐矿物组合中,首先出现的是方沸石,其次是钠沸石,再次为钠长石;在碳酸盐矿物中,首先出现的是菱镁矿,其次是菱铁矿,再次为铁白云石,有时还可见到方解石,但其含量很低。(2)在凝絮状团块中,团块中心为黄铁矿,从中心向外依次过渡为方沸石、钠沸石、菱镁矿、菱铁矿,最外层为铁白云石。在纹层状岩层和凝絮状团块中,有时还能见到上述顺序的逆顺序。(3)在后期充填的裂缝中,边部为沸石或绿泥石等铝硅酸盐矿物,向中心逐渐过渡为铁白云石碳酸盐。综合研究区所有的矿物序列来看,最完整的序列应为黄铁矿—钾长石—方沸石—钠沸石—钠长石—菱镁矿—菱铁矿—白云石—方解石,但是这种完整的序列是不常见的,通常仅为其中某几种矿物的组合,然而不管是哪些矿物进行组合,其出现的顺序都不变。推测该矿物序列的类型受热液喷流和溢流阶段、时间、温度和热水化学性质控制,早期高温、高盐度条件下出现的铝硅酸盐矿物序列较多,而晚期主要形成碳酸盐矿物序列。