共查询到19条相似文献，搜索用时 171 毫秒
1.
地质流体 岩石反应的地球化学动力学方法 总被引：3，自引：1，他引：2
摘 要 提出了一个以矿物生成和溶解的速率确定体系矿物沉淀的量来模拟水 岩反应的新方
法。新固相在体系中沉淀的量只依赖于沉淀速率而不是依赖于水 岩之间的平衡。考察了一
个矿物溶解生成次生矿物最终趋于平衡的溶解沉淀反应演化结果表明在水 岩体系中对于次
生矿物的部分平衡假定在许多情况下都不能成立。在这样的反应演化过程中亚稳矿物与溶液
之间总保持过饱和态矿物的沉淀速率随反应的进展而变化。同时当主要溶解矿物达到平
衡而溶解作用停止时次生矿物沉淀尚未停止直到体系饱和指数全部趋于0时才达到总
体平衡。用动力学方法处理地球化学过程中的水 岩反应比准稳平衡的简单假设更合理因为
动力学方法更符合自然情况同时产生了关于时间过程的时间尺度信息。 相似文献
2.
3.
地下水与玄武财反应趋势分析 总被引：1，自引：0，他引：1
通过建立水化学平衡反应模型,计算地下水组分的各种可能存在形式的浓度和活度,并求得各种矿的饱和指数,再用饱和指数分析水－岩相互作用过程中矿物的溶解与沉淀反应趋势。本文采用该方法对盱眙玄武岩土区水－岩间反应趋势进行了分析。 相似文献
4.
广东雷州半岛玄武岩地下水水文地球化学特征及演化模拟 总被引：2，自引：0，他引：2
应用水化学分析软件和水-岩作用模拟软件对雷州半岛的水文地球化学进行了分析和路径模拟。沿东、西2个地下水径流方向从一级台地补给区至二级台地、三级台地排泄区的模拟计算结果表明,地下水可能经历了一系列复杂的水-岩作用,包括石膏、高岭石、钙蒙脱石、伊利石、绿泥石、斜辉石(或透辉石)、针铁矿、赤铁矿的溶解或沉淀及CO2气体的溶解或逸出等地球化学反应。针铁矿、赤铁矿和透辉石的溶解或沉淀量在沿东面地下水径流方向上远小于沿西面方向;针铁矿和赤铁矿只在少量水点发生溶解进入地下水,在大多数水点处于饱和状态而从地下水中析出;CO2气体在大多数取样点发生溶解进入地下水中,其溶解量较大,且随着CO2在水中浓度的变大,其饱和指数也增大,达到饱和后从水中逸出。可见水-岩作用模拟结果有助于揭示研究区地下水化学环境的演化机制。 相似文献
5.
川滇高原斜坡地带峡谷区岩溶水化学特征及演化规律 总被引：3，自引：0，他引：3
岩溶地下水不仅作为重要的生活和生产用水水源,而且作为一种重要的地质营力,对于岩溶演化史具有重要影响,对其进行水化学特征分析及演化规律研究,能够为岩溶水资源及岩溶生态环境保护提供科学依据。以川滇高原斜坡地带峡谷区岩溶地下水为研究对象,结合研究区水文地质条件,对比分析了龙爪坝河岩溶水系统和洛泽河岩溶水系统内地下水化学特征。通过常规地下水化学组分、氢氧同位素分析和水文地球化学反向模拟,识别了地下水化学类型,确定了岩溶水的主要离子来源和补给特征,判别了发生的水岩相互作用过程。研究表明：岩溶地下水以大气降水为补给来源,离子源于岩石风化作用,物质来源为灰岩、白云岩夹灰岩,水岩相互作用均受方解石、白云石和石膏沉淀及溶解作用控制,且龙爪坝河岩溶水系统内矿物饱和指数趋近饱和,岩溶发育趋于停滞,而洛泽河岩溶水系统内矿物饱和指数处于不饱和或饱和的波动态,岩溶仍然发育。 相似文献
6.
7.
8.
地热回灌是解决地热田开发利用中热储压力下降的一个有效办法．用地球化学方法模拟了在Ｌａｕｇａｌａｎｄ低温（９５℃）地热田回灌过程中可能发生的化学作用．在模拟中考虑了石英等矿物的化学动力学因素．模拟结果表明：在用地热尾水回灌时,虽然混合水对于石英等矿物是饱和的,但由于它们沉淀速度很慢,在实际中不会产生沉淀．至于产生的较少的方解石沉淀,其全部或至少一部分是模型为使混合水达到对于方解石理论上的平衡而产生的．如果用地下水回灌,地下水中的镁将会和地热水中的二氧化硅形成较多的含镁硅酸盐沉淀． 相似文献
9.
人类活动对鄱阳湖赣江流域水质的影响受到广泛关注,厘清流域内污染水体对人类的健康风险状况有利于更好地保护和利用水资源。本研究于赣江下游采集39个地下水和16个地表水样,在分析其水化学特征和影响因素的基础上,对地下水水化学成分演变进行反向模拟,并对地下水水质以及潜在非致癌风险进行评价。结果表明,研究区地下水呈弱酸性-中性(pH=5.47~7.60),以HCO3-Ca-Mg型水为主,部分为Cl-Ca-Mg型水,硅酸岩风化和矿物溶解-沉淀作用是水化学类型形成的主要控制因素;地表水呈中性-弱碱性(pH=6.94~8.19),主要为HCO3-Cl-Ca-Na型水,其形成与硅酸岩风化、大气降水和人类活动有关。PHREEQC模拟计算结果表明,地下水中大部分矿物饱和指数(SI)为负数,其中岩盐的SI为-7.80~-9.53,指示该矿物溶解剧烈;白云石、石膏和方解石的SI分别为-1.72~-6.39、-1.65~-3.96、-0.51~-3.09,表明三种矿物呈溶解趋势。反向模拟结果显示,赣江干流地下水化学特征演变过程经历了Ca-蒙脱石、岩盐、白云石溶解和方解石沉淀,同时消耗CO2;支流中命名为NCGW-3的路径表现为高岭石、方解石、玉髓和白云石溶解,石膏、Ca-蒙脱石、黑云母和斜长石沉淀,同时产生CO2,可能与人为作用的干扰有关。其余支流地下水反向模拟结果与干流结果相似。熵权水质指数(EWQI)计算结果表明,干流地下水水质优于支流地下水,沿赣江受Mn、N 影响水质降低;地下水非致癌潜在风险主要为对婴儿存在严重风险,其次是儿童,对成年男性和成年女性风险相对较小,支流水质存在的潜在风险相较于干流更为显著。 相似文献
10.
大同盆地高氟地下水水化学特征及其成因 总被引：4，自引：0，他引：4
为查明控制大同盆地高氟地下水形成的主要地球化学过程,对大同盆地地下水高氟区31个水样进行了水化学特征及因子分析研究.结果表明,研究区浅层和深层地下水中均检测出氟,且氟含量高,最大ρ(F)达10.37 mg/L.该区高氟地下水以Na-HCO3型水为主,具有典型的富Na特征.PHREEQC饱和指数计算结果表明,地下水中萤石为不饱和状态,地下水中ρ(F)主要受到萤石溶解影响.因子分析研究表明,水一岩相互作用、碳酸盐矿物溶解沉淀及Na- Ca离子交换作用是控制大同盆地地下水氟富集的主要水化学过程. 相似文献
11.
The mineralization of bacterial organic matter in the groundwater of Iceland is discussed. Structural relationships between
secondary minerals in cavities within a Pleistocene basaltic sill and the general sequence of their precipitation allowed
us to recognize five stages of the secondary mineral formation. Two stages of layer silicate formation separated by a stage
of zeolite and apophyllite formation were pointed out. The composition and structure of clay minerals formed at different
stages as a result of the interaction between groundwater and basalt with an active participation of bacteria have been investigated.
Clay minerals of the second stage are similar in composition and microstructure to biomorphic structures previously studied
in Miocene plateau basalts. The last stage of mineralization is related to the fossilization of filamentous microbiota residing
in open cavities and covering all older secondary minerals 相似文献
12.
In order to evaluate the extent of CO2–water–rock interactions in geological formations for C sequestration, three batch experiments were conducted on alkali feldspars–CO2–brine interactions at 150–200 °C and 300 bars. The elevated temperatures were necessary to accelerate the reactions to facilitate attainable laboratory measurements. Temporal evolution of fluid chemistry was monitored by major element analysis of in situ fluid samples. SEM, TEM and XRD analysis of reaction products showed extensive dissolution features (etch pits, channels, kinks and steps) on feldspars and precipitation of secondary minerals (boehmite, kaolinite, muscovite and paragonite) on feldspar surfaces. Therefore, these experiments have generated both solution chemistry and secondary mineral identity. The experimental results show that partial equilibrium was not attained between secondary minerals and aqueous solutions for the feldspar hydrolysis batch systems. Evidence came from both solution chemistry (supersaturation of the secondary minerals during the entire experimental duration) and metastable co-existence of secondary minerals. The slow precipitation of secondary minerals results in a negative feedback in the dissolution–precipitation loop, reducing the overall feldspar dissolution rates by orders of magnitude. Furthermore, the experimental data indicate the form of rate laws greatly influence the steady state rates under which feldspar dissolution took place. Negligence of both the mitigating effects of secondary mineral precipitation and the sigmoidal shape of rate–ΔGr relationship can overestimate the extent of feldspar dissolution during CO2 storage. Finally, the literature on feldspar dissolution in CO2-charged systems has been reviewed. The data available are insufficient and new experiments are urgently needed to establish a database on feldspar dissolution mechanism, rates and rate laws, as well as secondary mineral information at CO2 storage conditions. 相似文献
13.
川北下侏罗统自流井组大安寨段灰岩非常规储层包裹体研究 总被引：5，自引：0，他引：5
通过对川北大安寨段灰岩非常规储层流体包裹体的系统研究，表明该储层的成因与多期次的深部溶蚀作用有关，可划分为成岩期，构造期和构造期３个溶蚀期及５个次生矿物沉淀阶段，各阶段流体包裹体类型丰度，形态，均一温度，盐度、密度和成分特征各相相同，显示溶蚀流体来自油源岩区于不同演化阶段排出的无机和有机流体，因而包裹体的各项牲和演化规律可作为评价和预测大安寨段非常规储层的标志。 相似文献
14.
地下孔隙率和渗透率在空间和时间上的变化及影响因素 总被引：18，自引：5，他引：18
地下岩石孔隙率和渗透率在空间和时间上的变化受众多因素控制,总的说来,包括沉积与成岩两个最为主要的因素。沉积盆地的性质和沉积环境控制了沉积物的组成、岩石的结构和原生孔隙。沉积作用所经历的时间相对较短而进程较快;成岩作用所经历的时间相对较长而进程较慢。从对孔隙率和渗透率的控制作用来说,成岩作用的研究难度相对较大。近年来,一些传统的形成地下岩石次生孔隙的机制受到挑战,这些传统机制中最为主要的是有机酸对铝硅酸溶解形成次生孔隙,但这会造成介质pH值的升高,碳酸盐矿物和高岭石的沉淀。地下岩石中碳酸水溶解产生的次生孔隙也是有限的。新的机制如大气淡水的溶解作用,深部冷却地下水的溶解作用,硅酸盐的水解都得到了人们的普遍接受,这对于次生孔隙成因的解释及地下岩石孔隙率和渗透率的预测十分重要。对于碳酸盐岩来说,与不整合面附近的古喀斯特有关的油气藏得到了更多的关注。深埋藏过程中碳酸盐岩成岩作用的研究中,温度和压力的影响对不同碳酸盐矿物溶解及沉淀作用的差异性控制了地下碳酸盐岩孔隙率和渗透率分布. 相似文献
15.
A numerical model of coupled saturated/unsaturated water flow, heat transfer and multi-component reactive solute transport
is presented to evaluate the long-term geochemical evolution in bentonite, concrete and clay formation for a potential geological
radioactive waste repository. Changes in formation porosity caused by mineral dissolution/precipitation reactions are taken
into account. Simulations were carried out with a general-purpose multicomponent reactive transport code, CORE2D V4. Numerical results show that pH in the bentonite porewater can vary from neutral to up to 13 over a time scale of 1 Ma
although dissolution of silica minerals and precipitation of secondary calcium silicate hydrate (CSH) minerals in bentonite
buffer the effect of the hyperalkaline plume. Mineral precipitation reduces the volume of pore space in bentonite close to
the bentonite–concrete interface due to the precipitation of CSH minerals. Model results indicate that bentonite porosity
decreases less than 25%. The hyperalkaline plume from the concrete only extends to a distance of 0.7 m in the clay formation
over the time range of 1 Ma. 相似文献
16.
原生硅酸盐矿物风化产物的研究进展——以云母和长石为例 总被引：6，自引：0，他引：6
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。 相似文献
17.
This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fourth paper in our series of “Coupled Alkali Feldspar Dissolution and Secondary Mineral Precipitation in Batch Systems”. In our third paper, we demonstrated via speciation-solubility modeling that partial equilibrium between secondary minerals and aqueous solutions was not attained in feldspar hydrolysis batch reactors at 90-300 °C and that a strong coupling between dissolution and precipitation reactions follows as a consequence of the slower precipitation of secondary minerals (Zhu and Lu, 2009). Here, we develop this concept further by using numerical reaction path models to elucidate how the dissolution and precipitation reactions are coupled. Modeling results show that a quasi-steady state was reached. At the quasi-steady state, dissolution reactions proceeded at rates that are orders of magnitude slower than the rates measured at far from equilibrium. The quasi-steady state is determined by the relative rate constants, and strongly influenced by the function of Gibbs free energy of reaction (ΔGr) in the rate laws.To explore the potential effects of fluid flow rates on the coupling of reactions, we extrapolate a batch system (Ganor et al., 2007) to open systems and simulated one-dimensional reactive mass transport for oligoclase dissolution and kaolinite precipitation in homogeneous porous media. Different steady states were achieved at different locations along the one-dimensional domain. The time-space distribution and saturation indices (SI) at the steady states were a function of flow rates for a given kinetic model. Regardless of the differences in SI, the ratio between oligoclase dissolution rates and kaolinite precipitation rates remained 1.626, as in the batch system case (Ganor et al., 2007). Therefore, our simulation results demonstrated coupling among dissolution, precipitation, and flow rates.Results reported in this communication lend support to our hypothesis that slow secondary mineral precipitation explains part of the well-known apparent discrepancy between lab measured and field estimated feldspar dissolution rates (Zhu et al., 2004). Here we show how the slow secondary mineral precipitation provides a regulator to explain why the systems are held close to equilibrium and show how the most often-quoted “near equilibrium” explanation for an apparent field-lab discrepancy can work quantitatively. The substantiated hypothesis now offers the promise of reconciling part of the apparent field-lab discrepancy. 相似文献
18.
19.
Alkali feldspar dissolution and secondary mineral precipitation in batch systems: 3. Saturation states of product minerals and reaction paths 总被引：1，自引：0，他引：1
In order to evaluate the complex interplay between dissolution and precipitation reaction kinetics, we examined the hypothesis of partial equilibria between secondary mineral products and aqueous solutions in feldspar-water systems. Speciation and solubility geochemical modeling was used to compute the saturation indices (SI) for product minerals in batch feldspar dissolution experiments at elevated temperatures and pressures and to trace the reaction paths on activity-activity diagrams. The modeling results demonstrated: (1) the experimental aqueous solutions were supersaturated with respect to product minerals for almost the entire duration of the experiments; (2) the aqueous solution chemistry did not evolve along the phase boundaries but crossed the phase boundaries at oblique angles; and (3) the earlier precipitated product minerals did not dissolve but continued to precipitate even after the solution chemistry had evolved into the stability fields of minerals lower in the paragenesis sequence. These three lines of evidence signify that product mineral precipitation is a slow kinetic process and partial equilibria between aqueous solution and product minerals were not held. In contrast, the experimental evidences are consistent with the hypothesis of strong coupling of mineral dissolution/precipitation kinetics [e.g., Zhu C., Blum A. E. and Veblen D. R. (2004a) Feldspar dissolution rates and clay precipitation in the Navajo aquifer at Black Mesa, Arizona, USA. In Water-Rock Interaction (eds. R. B. Wanty and R. R. I. Seal). A.A. Balkema, Saratoga Springs, New York. pp. 895-899]. In all batch experiments examined, the time of congruent feldspar dissolution was short and supersaturation with respect to the product minerals was reached within a short period of time. The experimental system progressed from a dissolution driven regime to a precipitation limited regime in a short order. The results of this study suggest a complex feedback between dissolution and precipitation reaction kinetics, which needs to be considered in the interpretation of field based dissolution rates. 相似文献