从平衡-封闭-静态转向非平衡-开放-动力学研究-热液矿床成因的若干新概念概述     

张荣华  胡书敏  张雪彤 《地质学报》2016,90(9):2437-2453

热液金属矿床成因研究过程中,观测与实验始终是密切结合的。上世纪70年代,平衡热力学的实验数据的快速积累,使人们用热力学理论计算可以预测和反演矿石和岩石的成因。但是,没有矿物-水溶液的反应速率数据,又没有与流体力学的结合,搞清楚矿石成因是困难的。七、八十年代,开始研究矿物与水溶液的反应动力学实验。科学家们开始瞄准了从平衡-封闭-静态转向非平衡-开放-动力学研究的这个大方向。1992年我们建立地球化学动力学开放研究实验室。研究高温高压矿物与水反应速率,发现固液的开放体系的自组织现象。实验发现温度影响矿物的各个元素反应速率改变,发现在跨越水临界态时矿物与水反应速率涨落、在近临界的气-液两相不混溶区一些金属进入气相、超临界流体的氧化作用及特别的溶剂性能影响矿物溶解性质。实验证实:临界态区流体与矿石成因有关。水岩相互作用的反应动力学实验温度从低温到550度,揭示矿石的金属来源、迁移、金属与蚀变分带机制。一大批大于300度的矿物与水反应动力学实验在国际界是少有报道的。九十年代,超高压的科学发展,与同步辐射光源的技术进步的结合,使固体地球科学又迈向了地球深内部。我们发展了高温高压流体性质的原位直测(测量850℃水溶液)红外谱,发现深部流体的新性质:气液两相流体的新结构,在临界温度区(300~400℃),水分子氢键网络的破坏受压力影响不大(23MPa~3GPa),同时,出现水的高电导率。研发新仪器为开放-流动-非平衡的反应动力学实验与极端条件下物质性质的直接观测结合,在科学前沿领域开辟了创新道路。  相似文献   

Reactivity of micas and cap-rock in wet supercritical CO2 with SO2 and O2 at CO2 storage conditions     

《Applied Geochemistry》2016

Seal or cap-rock integrity is a safety issue during geological carbon dioxide capture and storage (CCS). Industrial impurities such as SO₂, O₂, and NOx, may be present in CO₂ streams from coal combustion sources. SO₂ and O₂ have been shown recently to influence rock reactivity when dissolved in formation water. Buoyant water-saturated supercritical CO₂ fluid may also come into contact with the base of cap-rock after CO₂ injection. Supercritical fluid-rock reactions have the potential to result in corrosion of reactive minerals in rock, with impurity gases additionally present there is the potential for enhanced reactivity but also favourable mineral precipitation.The first observation of mineral dissolution and precipitation on phyllosilicates and CO₂ storage cap-rock (siliciclastic reservoir) core during water-saturated supercritical CO₂ reactions with industrial impurities SO₂ and O₂ at simulated reservoir conditions is presented. Phyllosilicates (biotite, phlogopite and muscovite) were reacted in contact with a water-saturated supercritical CO₂ containing SO₂, or SO₂ and O₂, and were also immersed in the gas-saturated bulk water. Secondary precipitated sulfate minerals were formed on mineral surfaces concentrated at sheet edges. SO₂ dissolution and oxidation resulted in solution pH decreasing to 0.74 through sulfuric acid formation. Phyllosilicate dissolution released elements to solution with ∼50% Fe mobilized. Geochemical modelling was in good agreement with experimental water chemistry. New minerals nontronite (smectite), hematite, jarosite and goethite were saturated in models. A cap-rock core siltstone sample from the Surat Basin, Australia, was also reacted in water-saturated supercritical CO₂ containing SO₂ or in pure supercritical CO₂. In the presence of SO₂, siderite and ankerite were corroded, and Fe-chlorite altered by the leaching of mainly Fe and Al. Corrosion of micas in the cap-rock was however not observed as the pH was buffered by carbonate dissolution. Ca-sulfate, and Fe-bearing precipitates were observed post SO₂-CO₂ reaction, mainly centered on surface cracks and an illite rich illite-smectite precipitate quantified. Water saturated impure supercritical CO₂ was observed to have reactivity to rock-forming biotite, muscovite and phlogopite mineral separates. In the cap-rock core however carbonates and chlorite were the main reacting minerals showing the importance of assessing actual whole core.  相似文献   

元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定   总被引：2，自引：2，他引：0  

徐丽  邢蓝田  王鑫  李中平  毛俊丽 《岩矿测试》2018,37(1):15-20

沉积有机质的碳氮稳定同位素值是进行古气候、古环境及生态系统研究不可或缺的主要研究手段,目前碳氮同位素主要利用元素分析仪-同位素比值质谱(EA-IRMS)系统来测定。EA-IRMS测定过程中的反应温度及样品进样量直接影响反应物在测试中的燃烧程度,从而影响测试数据的精度。本文利用EA-IRMS技术,以标准样品为参考,在不同转化温度下测试碳氮同位素值,研究保证测试精度的最佳反应温度条件;同时,通过分析不同含氮量样品的检测限,明确了样品含氮量与最低检测限之间的关系,确定了精确测定氮同位素值的最低进样量。结果表明:反应温度对测试精度有显著影响,在碳同位素测定时,将反应温度设定为900℃或以上时测试精度均能达到±0.2‰;氮同位素测定时,反应温度须设定为950℃时测试精度才能达到±0.3‰。实验得出样品含氮量与检测限之间的线性相关性为R2=0.873,开展氮同位素测定时可根据此关系来判断和控制进样量。  相似文献   

压力对辉长岩矿物反应和部分熔融影响的实验研究     

沙茜  周永胜 《岩石学报》2018,34(3):851-865

本文在高温高压条件下,开展了辉长岩矿物反应与部分熔融实验,利用偏光显微镜与扫描电镜对实验样品微观结构观察,研究实验中的新生矿物与熔体的分布;通过电子探针分析熔体成分特征。实验结果表明,在低压(300MPa)条件下,静压和塑性变形实验样品中,单斜辉石以固体反应方式生成橄榄石,在高压(1300MPa)塑性实验中所有实验样品都没有发现新生矿物颗粒,这与相图中低压条件下斜长石与橄榄石稳定共存,而高压下斜长石-辉石稳定共存相吻合。高压塑性变形条件下,单斜辉石和黑云母首先发生部分熔融,随着温度增高,斜长石逐渐参与熔融,熔体呈薄膜状分布在矿物颗粒边界,熔体成分依赖于参与熔融的矿物成分,表明出现的熔体为非平衡熔融结果。  相似文献   

鄂尔多斯盆地南部马莲河流域地下水中锶富集特征及成因分析     

李海学  程旭学  马岳昆  刘伟坡  周斌 《现代地质》2021,35(3):682-692

马莲河流域地处鄂尔多斯盆地南部黄土高原区,按储水介质和埋藏条件可将地下水分为黄土潜水、基岩潜水和基岩承压水三类,利用2015—2018年流域的295组地下水水化学数据,分析了地下水中锶(Sr²⁺)的质量浓度水平、垂向分布及沿流向分布的特征,并采用因子相关性研究地下水中Sr²⁺的来源和富集成因。结果表明:马莲河流域地下水富锶现象显著,黄土潜水、基岩潜水和基岩承压水中锶的平均质量浓度分别为1.14 mg/l、1.39 mg/l和5.24 mg/l;地下水中锶富集成因主要是含锶矿物天然状态下的水-岩作用,黄土潜水、基岩潜水和基岩承压水三类地下水中Sr²⁺的主要来源分别为碳酸盐岩与铝硅酸盐岩、碳酸盐岩与硫酸盐和碳酸盐矿物的溶滤作用;地下水中Sr²⁺的质量浓度沿流向呈逐渐增大的趋势,在不同区域中随深度变化的趋势不一致。  相似文献   

方解石与含硅流体的水-岩反应实验及其对“硅化碳酸盐岩”储层成因的启示     

杨源显  陈强路  丘靥  尤东华  王小林 《高校地质学报》2021,27(2):218-228

近年来的油气勘探表明, 含硅热液是碳酸盐岩层系中一种重要的溶蚀性流体, 查明其与碳酸盐岩的水-岩反应机理是揭示“硅化碳酸盐岩”储层发育机制并实现储层分布预测的基础和关键问题之一。文章采用熔融毛细硅管和水热反应釜为反应腔,开展了200~375℃范围内方解石和含硅流体的水岩反应实验。利用原位拉曼光谱技术在线描述反应过程中体系组成的变化,对于淬火后的固相样品,则采用扫描电镜—能谱分析进行形貌观测和成分鉴定。首先,查明了含硅流体与方解石脱碳反应发生的温度条件。方解石和含硅流体在275℃以上反应形成CO₂,固相为非硅灰石的钙硅酸盐,其结构有待进一步揭示。该结果表明单纯的硅质组分难以在储层温度条件下与灰岩发生反应;其次,提出高盐度、富CO2流体作用是造成灰岩溶蚀的重要因素;最后, CO₂的存在能够促进硅质（含石英）沉淀。在上述实验认识的基础上,结合前人研究结果探讨了塔里木盆地顺托果勒地区“硅化碳酸盐岩”储层的发育机制。含硅热液沿深大断裂上移,途径震旦系—下奥陶统白云岩层系,其中的硅质组分将与白云石反应形成富镁硅酸盐和CO₂。CO₂是重要的酸性组分,有利于鹰山组碳酸盐的溶蚀和孔隙的保存。流体温度和压力的降低以及CO₂的存在促进了石英沉淀,并形成了大量的石英晶间孔隙。  相似文献   

Nonlinear analysis of laterally loaded rigid piles in cohesive soil     

Lianyang Zhang  Saeed Ahmari 《国际地质力学数值与分析法杂志》2013,37(2):201-220

This article presents a method for the nonlinear analysis of laterally loaded rigid piles in cohesive soil. The method considers the force and the moment equilibrium to derive the system equations for a rigid pile under a lateral eccentric load. The system equations are then solved using an iteration scheme to obtain the response of the pile. The method considers the nonlinear variation of the ultimate lateral soil resistance with depth and uses a new closed‐form expression proposed in this article to determine the lateral bearing factor. The method also considers the horizontal shear resistance at the pile base, and a bilinear relationship between the shear resistance and the displacement is used. For simplicity, the modulus of horizontal subgrade reaction is assumed to be constant with depth, which is applicable to piles in overconsolidated clay. The nonlinearity of the modulus of horizontal subgrade reaction with pile displacement at ground surface is also considered. The validity of the developed method is demonstrated by comparing its results with those of 3D finite element analysis. The applications of the developed method to analyze five field test piles also show good agreement between the predictions and the experimental results. The developed method offers an alternative approach for simple and effective analysis of laterally loaded rigid piles in cohesive soil. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

季冻区桥梁基桩抗冻拔验算几个问题的探讨     

盛洪飞 《冰川冻土》1989,11(1):44-52

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A garnet population in Yellowknife schist, Canada   总被引：6，自引：0，他引：6  

R. KRETZ 《Journal of Metamorphic Geology》1993,11(1):101-120

Abstract Data are presented on a garnet population in a specimen of garnet-biotite-plagioclase-quartz schist from the cordierite zone of an Archaean thermal dome in the Southern Slave Province of the Canadian Shield. Garnet crystals are bounded by planar dodecahedral faces and by trapezohedral faces which on the 10-μm scale are corrugated. Crystal distribution, as revealed by dissection of a small cubic volume of rock, is random. The size distribution is normal, with a mean diameter of 0.81 mm and a standard deviation of 0.32 mm. In the largest crystal of the population (mean radius 0.83 mm), [Mn] = 100 Mn/(Fe + Mg + Mn + Ca) decreases from 14.5 at the centre to 7.5 and then increases in the outer margin to 8.5; [Fe] increases continuously from 67 at the centre to 77 at the surface; [Mg] increases from 12.5 to 13.5 and then falls sharply to 11; [Ca] remains unchanged at 4.0 and then drops to 3.3. Progressively smaller crystals have progressively lower [Mn] and higher [Fe] concentrations at their centres, while all crystals have the same margin composition. Growth vectors extending from given concentration contours to crystal surfaces are of equal length regardless of the size of the crystal in which the vector is located. A garnet-forming model is presented in which reaction was initiated by a rise in temperature. Nucleation sites were randomly selected. The nucleation rate increased with time and then declined. Crystal faces advanced at a constant linear rate, which implies an increase in volume proportional to surface area. Initially, the composition of garnet deposited on crystal surfaces was determined by van Laar equations of equilibrium, which demanded the withdrawal of Mn and Fe from within chlorite crystals. This transfer reaction was then accompanied by an ion exchange reaction which moved Mn and Fe to garnet surfaces from biotite, in exchange for Mg. The exchange reaction provides an explanation for the high overall concentration of Mn and Fe in garnet and for the observed Mn and Mg reversals in the margins of crystals. The increase of garnet volume in the garnet population is found to be parabolic, i.e. Vαα⁵.  相似文献   

豫西东秦岭造山带核部杂岩中钙质变质岩的变质作用演化   总被引：3，自引：0，他引：3  

陈能松  张兴辽 《岩石学报》1993,9(3):240-254

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