湖南瑶岗仙石英脉型钨矿床成矿系统

湖南瑶岗仙石英脉型钨矿床是南岭成矿带具有代表性的矿床。长期以来,对脉型钨矿床的成矿岩体特征及各种不同类型矿化的空间与演化关系一直存在争论。文章以瑶岗仙石英脉型钨矿床为研究对象,在野外地质调查的基础上,针对成矿岩体、含钨石英脉及与之相关的矿化开展地质地球化学研究工作,探讨了岩浆-热液演化过程中形成的各类矿化现象,从而建立了脉型钨矿床成矿系统。在瑶岗仙钨矿床中,成矿地质体即成矿花岗岩为碱长花岗岩,主要矿化类型包括岩浆岩型、云英岩析离体、云英岩脉、石英脉和毒砂黄玉层等,分布于岩体顶部接触带附近。成矿作用可划分为岩浆晚期阶段、岩浆热液过渡阶段、岩浆期后热液阶段,岩浆岩型矿石形成于岩浆晚期,云英岩析离体和云英岩脉等形成于岩浆-热液过渡阶段,石英脉和毒砂黄玉层主要形成于热液阶段,岩浆阶段→热液阶段的演化是连续的。成矿花岗岩侵位深度约为2~3 km,提供了主要成矿物质与成矿流体。成矿系统相对封闭,外来成矿物质和流体较少,含钨石英脉主要以快速充填的形式形成于岩浆固结之后。瑶岗仙矿床含钨石英脉控制垂深达1300 m,"五层楼"垂向分带不明显,顶部未出现细脉带和线脉带,而在石英大脉的顶部出现横向交代形成的毒砂黄玉层。研究表明,瑶岗仙矿区脉型钨矿床成矿系统保存较完整,代表系统顶部的毒砂黄玉层保存完好,剥蚀水平正好达到岩体顶部。     

“带外脉式”钨矿床成矿模型——以湖南白云仙钨矿田头天门矿床为例

石英脉型钨矿床是南岭钨矿成矿带的主要矿床类型,含钨石英脉产于成矿花岗岩顶部的接触带附近,其中"带外脉式"的石英脉几乎全部产于接触带外侧。湖南白云仙钨矿田头天门钨矿床发育较完整的"带外脉式"钨矿矿化组合和空间分带,主要矿化类型包括花岗岩型和石英脉型,前者分布于岩墙上部,后者发育于上方外侧的砂岩中。笔者研究了头天门钨矿床中花岗岩和各类矿体的地质地球化学特征,探讨了岩浆演化与钨的富集成矿过程。提出头天门钨矿床粗粒斑状黑云母花岗岩→细粒碱长花岗岩岩株→岩墙→云英岩化花岗岩→云英岩→石英脉的岩浆-热液演化-成矿全过程,成矿流体表现出"上液下浆"的分带特点。在岩墙形成前的演化过程中,成矿元素的富集主要受岩浆晚期分异作用的制约,岩墙之后的演化则主要受热液作用的影响。成矿地质体为细粒碱长花岗岩岩株以及上部的岩墙。建立了带外脉式型钨矿床成矿模型,形成机制主要为:在岩浆固结之前,岩浆中的挥发分和H2O在岩体顶部聚集引起围岩破裂,岩浆充填形成岩墙,挥发分和成矿物质在岩墙上部聚集形成花岗岩型(云英岩型)钨矿,并在外侧形成石英脉型钨矿。     

巴里坤小加山钨矿床的成矿流体及矿床成因

小加山钨矿床位于新疆巴里坤地区,属石英脉型钨矿床。矿体赋存于邻近海西晚期花岗岩侵入体附近的中泥盆统大南湖组第一亚组第二段(D2d12)的变晶屑凝灰岩中。黑钨矿石英脉分为灰色含钨石英脉和白色含钨石英脉两种。岩相学观察认为,含矿石英脉中流体包裹体主要为两相水溶液包裹体, EW 走向的灰色石英脉包裹体气液比大, SN 走向的白色石英脉包裹体气液比较小。显微测温结果显示灰色石英脉均一温度(Th)范围为143~354℃,白色石英脉 Th 范围为154~312℃。激光拉曼探针显示小加山钨矿床含黑钨矿石英脉中流体包裹体含有少量 CO2组分。H、O 同位素研究表明：钨矿床成矿流体来源以岩浆水为主。成矿演化过程为：岩浆岩侵入活动→岩浆水运移分离→含钨络合物迁移搬运→冷却富集成矿,成矿晚期流体有大气降水的混合。与赣南钨矿的对比研究表明,小加山钨矿床与赣南钨矿床的成矿流体特征相似;在构造环境上,小加山钨矿床位于东准噶尔造山带和东天山成矿带的交汇复合部位,与位于武夷山和南岭两大成矿带的交汇复合部位的赣南钨矿床成矿环境相似。     

云南红河绿春大马尖山铜砷矿床成矿液体特征

矿体受石英斑岩和断层控制,一般产于石英斑岩与志留系地层接触带附近或断层破碎带中,与燕山晚期构造运动有关。绿春大马尖山铜砷矿床成矿流体从下部到上部的成矿温度逐渐降低,成矿盐度由低到高,均一温度变化不大,暗示流体从下部到上部,由富Na体系向富Ca体系逐级演化;该区铜砷矿床流体特征与钨成矿流体特征不同,暗示二期成矿特征,初步判断该矿床为构造控制的热液脉型矿床。     

河南西峡石板沟金矿成矿流体地球化学及矿床成因讨论

石板沟金矿是近年在豫西南发现的一个剪切带容矿的脉状金矿。根据流体包裹体地球化学研究,分析了矿床成矿流体地球化学特征,讨论了金的沉淀机制和矿床成因。构造蚀变岩型金矿的形成主要与热液蚀变作用有关,石英脉型金矿的形成,则可能主要与岩浆热液与变质热液的混合作用有关。矿质主要源自晋宁期岩浆岩,成矿流体和热能主要来自海西期花岗岩。矿床为剪切带容矿的中低温热液金矿床。     

巴里坤小加山鹤矿床的成矿流体及矿床成因

小加山钨矿床位于新疆巴里坤地区,属石英脉型钨矿床。矿体赋存于邻近海西晚期花岗岩侵入体附近的中泥盆统大南湖组第一亚组第二段(D_2d_1~2)的变晶屑凝灰岩中。黑钨矿石英脉分为灰色含钨石英脉和白色含钨石英脉两种。岩相学观察认为,含矿石英脉中流体包裹体主要为两相水溶液包裹体,EW走向的灰色石英脉包裹体气液比大,SN走向的白色石英脉包裹体气液比较小。显微测温结果显示灰色石英脉均一温度(Th)范围为143~354℃,白色石英脉Th范围为154~312℃。激光拉曼探针显示小加山钨矿床含黑钨矿石英脉中流体包裹体含有少量CO_2组分。H、O同位素研究表明:钨矿床成矿流体来源以岩浆水为主。成矿演化过程为:岩浆岩侵入活动→岩浆水运移分离→含钨络合物迁移搬运→冷却富集成矿,成矿晚期流体有大气降水的混合。与赣南钨矿的对比研究表明,小加山钨矿床与赣南钨矿床的成矿流体特征相似;在构造环境上,小加山钨矿床位于东准噶尔造山带和东天山成矿带的交汇复合部位,与位于武夷山和南岭两大成矿带的交汇复合部位的赣南钨矿床成矿环境相似。     

赣南西华山钨矿床成矿流体演化特征

赣南西华山钨矿床是一个闻名中外的大型石英脉型钨矿床。为探讨成矿流体性质以及演化过程,本文对西华山石英脉型钨矿床主成矿阶段含矿石英脉中流体包裹体进行了岩相学、显微测温学研究和激光拉曼光谱分析。结果显示,西华山钨矿床的流体包裹体以H2O-NaCl型为主,局部发育H2O-NaCl-CO2型。流体热焓-盐度图解表明成矿流体以混合作用为主,局部沸腾在热液系统演化中作用不大。通过对沸腾包裹体的测温数据进行计算,得出西华山脉型钨矿成矿压力约为27～87 MPa,矿床形成深度约为1.0～3.3 km。     

新疆哈密市沙东钨矿成矿流体包裹体特征研究

新疆哈密市沙东钨矿是中天山地块首次发现的大型钨矿床,通过对沙东钨矿主成矿阶段形成的含白钨矿石英脉中流体包裹体进行岩相学和显微测温研究。初步确定矿床成矿温度为160℃~350℃,成矿压力为54.039~71.946 MPa,成矿深度1.80~2.40 km,成矿流体为富含多种气态组分的中低盐度流体。综合矿区成矿地质背景、矿床地质特征及流体包裹体显微测温成果认为,沙东钨矿矿床成矿流体为中高温、中低盐度的NaCl-H_2O-CO_2(-CH_4)体系。成矿流体主要来自酸性岩浆热液,主要含矿热液富碱、富硅和富CO_2、富F等挥发份流体。成矿过程中流体发生不混溶,对钨的富集起重要作用。     

赣中徐山钨矿床矿物流体包裹体地球化学特征及其地质意义

赣中徐山钨矿属于典型的"三位一体"的矿床,即集石英脉型、矽卡岩型、花岗岩型钨矿床于一体的矿床类型。其符合赣南-粤北地区的典型的"五层楼+地下室"的成矿模式。通过对该矿床石英脉型钨矿床矿物流体包裹体进行岩相学观察和显微测温分析,探讨成矿流体地球化学特征,结果显示,成矿流体属中高温(170~210℃)中低盐度(7%~13%)、低密度(0.8~0.95 g/cm3)流体类型。并与赣南、赣北典型的钨矿床进行对比分析,对比显示成矿流体性质及成矿地质条件的差异性可能是造成赣南伴生锡为主,而赣北伴生铜为主的原因。     

脉钨矿床液态分离成岩成矿作用研究述评——以赣南左拔钨矿床为例

<正>石英脉型黑钨矿床(简称"脉钨矿床")通常被认为是岩浆期后热液成因的矿床。但越来越多的人认为脉钨矿床成矿流体决不是稀薄的溶液,而是一种以SiO2为主,富H2O和挥发分的粘稠液体(夏卫华,1985、1989;余行祯等,1988;冯志文等;1989)或称"岩浆-热液过渡性流体"(林多新等,1986;张德会,1987;常海亮,2002;黄惠兰,2012),液态分离成矿作用贯穿成岩成矿过程的始终(张德会,1988),主要证据如下:     

渗流-化学溶解耦合作用下岩石单裂隙渗透特性研究

为揭示在渗流-化学溶解耦合作用下单裂隙渗透特性的变化规律,建立了描述二维渗流-化学溶解耦合作用的偏微分方程组,并利用COMSOL Multiphysics软件成功地求解该方程组。首先,模拟了文献[1]中的盐岩渗流-溶解耦合渗流试验结果,数值模拟结果与试验结果较为吻合,验证了数学模型的正确性和有效性。然后,利用分形理论生成了一个粗糙的裂隙面数字模型,着重分析了二维石灰岩粗糙裂隙面在水流、矿物溶解和输运过程中其渗透特性的变化规律。数值分析显示,（1）溶质浓度对裂隙面的溶解具有非常重要的作用,从而水流进口端的溶解厚度比出口端大得多。（2）裂隙的整体渗透性在初始时刻增加较慢,随着裂隙开度的增大和贯通,溶解速度会逐渐增大,是一个加速的过程。     

“构造地质学”发展方向的一些思考

构造地质学是地质学的核心基础学科,其发展方向是目前构造地质学家面临的挑战之一。本文从构造作用的本质出发,试图对构造地质学的发展方向进行思考。构造作用本质上是岩石和矿物对应力作用的响应,包括物理响应和化学响应,进而用数学方法进行表达:(1)物理响应主要表现为变形,包括脆性变形和韧性变形。岩石的力学性能决定了其变形特征。岩石圈力学性能在时间和空间上的不均一性一直是研究岩石圈变形行为的巨大挑战。需要结合野外观测、岩石力学和流变学研究,并借助多尺度模拟方法来建立不同时间尺度和空间尺度下岩石的变形行为和变形准则。(2)化学响应主要指构造应力作用下岩石和矿物发生化学变化的过程,即应力化学作用。变形变质作用、剪切带成矿作用、剪切带石墨化、应力生气和生烃等方面都可能存在应力化学过程,但其详细过程和反应机理还需要进一步探究。(3)运用数值模拟、量子计算对以上这些构造过程进行数学表达,也是构造地质学未来发展值得关注的方向。总之,构造地质学未来的发展方向应是与物理学、化学乃至数学等基础学科的深度融合。     

Study on coupled thermo-hydro-mechanical processes in column bentonite test

An unconventional numerical scheme is developed to simulate coupled thermo-hydro-mechanical (THM) processes in partially saturated medium. The non-isothermal, unsaturated fluid flow and mechanical processes are sequentially coupled by updating all the state variables using cellular automaton technique and finite difference method on spatial and temporal scale, respectively. A new cellular automaton updating scheme is proposed by introducing a fast successive relaxation index, which greatly improves the computational efficiency in the simulation of THM coupling process. This is implemented in a self-developed numerical system, i.e., an elasto-plastic cellular automaton (EPCA^3D), which was used to numerically reproduce the coupled THM behavior of bentonite pellets in a column experiment that was heated up to 140 °C firstly and then was hydrated simulating the resaturation of the backfilling. By using the cellular automaton technique in EPCA^3D, the challenging courses of the changing boundary conditions over time and space during the experiment are conveniently implemented. The EPCA^3D was able to reproduce the main physical processes of the in laboratory column bentonite experiment within the heating and hydration phase. The modeling results for the evolution of temperature, relative humidity, water uptake and axial pressure are consistent with the experimental data in terms of trends and magnitudes, which verifies the realistic simulation with the developed model and contributes to a deeper understanding of the observed phenomena.     

Progress in Numerical Simulation of Long-Term Impact of Thermokarst Lakes on Permafrost Thermal Regime

Thermokarst lakes are a major heat source for the adjacent permafrost and a significant source of atmospheric methane. These lakes have important impacts on the physical, chemical, biological, geomorphological and hydrological processes occurring in the ground under and around thermokarst lakes, and seriously affect the local environment and the stability of the structures constructed in permafrost regions. Numerical simulation methods provide an effective method for quantitative analysis of the long-term impact of thermokarst lakes and their evolution on permafrost surrounding the lakes, and have deepened our knowledge about the impact of thermokarst lakes immensely. Summarizing the research progresses in numerical simulation of long-term impact of thermokarst lakes on thermal regime of surrounding permafrost has an important guiding function to improve mathematical models and develop more effective models. In this study, the components, functions, advantages and defects of several typical mathematical models having developed over the past ten years or so were reviewed, such as the heat conduction model with phase change, thaw slumping model, the coupled lake-permafrost model, thaw lake expansion model combining thermal processes with mass wasting and thaw-driven subsidence, the coupled heat conduction and moisture migration model, and the moving mesh method based thermokarst lake dynamic evolution model. Several issues deserving to be paid further attention in the future researches were proposed, including creating more effective models, determining the more realistic initial condition, lucubrating thermal and physical parameters of the typical soils, consider the impact of lake water replenishment, quantitative analysis of the thermal effect of supra-permafrost water flow around the thermokarst lakes, creating the coupled governing equation of heat conduction with phase change and convective heat transfer, embed ding the effect of climate warming in the model, numerical investigation of the long-term influence of thermokarst lake drainage on the environment change in permafrost regions, analyzing the long-term joint impact of multiple lakes on adjacent permafrost, simulating the near-shore talik development process and feature beneath shallow water in expanding thermokarst lakes, and continuing to do the systemic and comprehensive field measurements.     

NUMERICAL GEODYNAMIC MODELLING OF COUPLED MECHANO-THERMO-HYDROLOGICAL PROCESSES AND ITS APPLICATION IN PREDICTIVE EXPLORATION IN THE FENGHUANGSHAN ORE FIELD, TONGLING

Mineralisation is the result of the coupled multi-geodynamic processes in the crust. The coupled mechano-thermo-hydrological （MTH） processes are the basic physical processes that govern the location of the hydrothermal mineralization, which can be simulated in the computer by using of the numerical codes, such as FLAC. The numerical modeling results can be used not only to explain the features of existing ore deposits, but also to predict the fhvorable mineralization locations. This paper has summarized the basic equations describing coupled MHT processes in the water-saturated porous rocks, the principles of FLAC, and its application to the MHT processes related to copper mineralization in the Fenghuangshan ore field. We used the FLAC to simulate the syn-deformation cooling and fluid flowing evolution after the intrusion was emplaced and solidified. The modeling results suggest a most prospective exploration area where the subsequent exploration supported the prediction and the test bore hole disclosed the high quality copper ore bodies in the target, demonstrating a positive role of the numerical MTH modeling in facilitating predictive ore discovery.     

计算流体地球化学研究的进展

成矿作用的化学机理可以通过实验和计算机模拟进行研究。随着计算机运算能力的不断增强 ,在地球化学中正在形成一门新兴学科———计算地球化学。其中热质输运模拟、化学质量迁移数值模拟和流体输运化学反应耦合动力学研究取得了显著进展。建立在Darcy定律和守恒方程基础上的多孔介质热质输运模拟通过流函数图、等温线图及速率矢量图等 ,从古水文学和流体地球化学方面高度动态研究成矿作用。根据化学和热力学原理进行的化学质量迁移数值模拟则通过矿物和流体中化学物种的热力学数据 ,预测多组分体系中发生的流体岩石相互作用 ,定量揭示经历了复杂化学反应进程的成矿作用的化学行为。将上述两方面结合的流体输运化学反应耦合动力学 ,可以从时间和空间上模拟真实成矿流体系统复杂的动力学行为 ,是计算流体地球化学的发展方向。     

矽卡岩型钨矿床成矿作用研究进展

钨具有极高的熔点和硬度,是现代生活、工业、国防和高科技领域中不可或缺的基础材料。研究显示,矽卡岩型钨矿是世界钨矿床中最主要的类型,广泛分布于受俯冲影响的环太平洋大陆边缘和与碰撞有关的欧亚大陆内部古大陆边缘,形成时代集中在中生代和古生代。钨在岩浆演化过程中呈现不相容的特征,因此与钨矿化相关的岩浆岩演化程度较高,包括S型、A型以及高分异I型花岗岩。钨具有较高的流体亲和性,使其在熔-流体分异过程中倾向于富集在共存的流体相。钨在热液流体中以氯化物、氟化物和碳酸盐络合物,以及同多钨酸盐和杂多钨酸盐等形式迁移,主要受源岩、围岩成分和流体物化条件等因素影响。矽卡岩型钨矿的成矿作用存在多期次、多阶段演化特征,不同阶段的成矿流体的温度和盐度存在差异。白钨矿是矽卡岩型钨矿中主要的矿石矿物,其沉淀可能受到多种机制的影响,如降温、流体混合、流体沸腾及流体-围岩反应等。文章简要综述了世界矽卡岩型钨矿的时空分布、地质特征和相关成因矿物学研究,并重点总结了钨的成矿岩浆-热液体系特征,钨在岩浆-热液演化过程中的地球化学行为及其迁移和沉淀机制等方面的研究成果。文章指出,为了完善矽卡岩型钨矿的成矿和找矿勘查模型,应当加强矽卡岩型钨矿的成矿时代、成矿物质和流体来源以及成矿环境的精细研究。     

Ice-avalanche scenario elaboration and uncertainty propagation in numerical simulation of rock-/ice-avalanche-induced impact waves at Mount Hualcán and Lake 513, Peru

The interest in numerical simulation of cascading processes involving mass movements and lakes has recently risen strongly, especially as the formation of new lakes in high-mountain areas as a consequence of glacier recession can be observed all over the world. These lakes are often located close to potentially unstable slopes and therewith prone to impacts from mass movements, which may cause the lake to burst out and endanger settlements further downvalley. The need for hazard assessment of such cascading processes is continuously rising, which demands methodological development of coupled numerical simulations. Our study takes up on the need for systematic analysis of the effect of assumptions taken in the simulation of the process chain and the propagation of the corresponding uncertainties on the simulation results. We complemented the research of Adv Geosci 35:145-155, 2014 carried out at Lake 513 in the Cordillera Blanca, Peru, by focusing on the aspects of (a) ice-avalanche scenario development and of (b) analysis of uncertainty propagation in the coupled numerical simulation of the process chain of an impact wave triggered by a rock/ice avalanche. The analysis of variance of the dimension of the overtopping wave was based on 54 coupled simulation runs, applying RAMMS and IBER for simulation of the ice avalanche and the impact wave, respectively. The results indicate (a) location and magnitude of potential ice-avalanche events, and further showed (b) that the momentum transfer between an avalanche and the impact wave seems to be reliably representable in coupled numerical simulations. The assessed parameters—initial avalanche volume, friction calibration, mass entrainment and transformation of the data between the models—was decisive of whether the wave overtopped or not. The overtopping time and height directly characterize the overtopping wave, while the overtopping volume and the discharge describe the overtopping hydrograph as a consequence of the run-up rather than the wave. The largest uncertainties inherent in the simulation of the impact wave emerge from avalanche-scenario definition rather than from coupling of the models. These findings are of relevance also to subsequent outburst flow simulation and contribute to advance numerical simulation of the entire process chain, which might also be applied to mass movements other than rock/ice avalanches.     

A global approach to reactive transport: application to the MoMas benchmark

Water resource management involves numerical simulations in order to study contamination of groundwater by chemical species. Not only do the aqueous components move due to physical advection and dispersion processes, but they also react together and with fixed components. Therefore, the mass balance couples transport and chemistry, and reactive transport models are partial differential equations coupled with nonlinear algebraic equations. In this paper, we present a global method based on the method of lines and differential algebraic system (DAE) solvers. At each time step, nonlinear systems are solved by a Newton-LU method. We use this method to carry out numerical simulations for the reactive transport benchmark proposed by the MoMas research group. Although we study only 1D computations with a specific geochemical system, several difficulties arise. Numerical experiments show that our method can solve quite difficult problems, get accurate results and capture sharp fronts.     

核废物地质处置模型试验近场热-水-应力耦合数值模拟

笔者描述了所建立的饱和-非饱和介质中热-水-应力耦合现象的控制方程。针对国际合作项目DECOVALEX II 中Task-2的核废物地质处置轴对称模型试验及计算参数,使用所研制的有限元程序进行了热-水-应力耦合过程模拟。对缓冲层及岩体中若干部位的温度、含水量及接触应力的分布、变化进行了分析, 并将其与量测值和使用THAMES程序的计算结果作了比较,看到了三者的异、同之处,并指出了可能的影响原因。通过与量测值和THAMES程序的计算结果的对比,显示了笔者所研制的有限元程序在热-水-应力耦合数值分析中是可靠和实用的。