成矿多过程耦合模型数值模拟研究态势

成矿作用是构造变形-热量传递-流体流动-质量转移等四种性质完全不同过程的耦合.数值模拟是通过建立多过程耦合模型来刻画其物理和化学规律.由于这些耦合模型过于复杂而难以得到其解析解,因而数值模拟被用来讨论这些复杂动力学过程.针对成矿预测领域主要的耦合模型:形变-流动模型、形变-热-流动模型、热-流动-质模型、变形-热-流动-质模型,通过这些耦合模型应用实例分析得出,印证了高差和温度变化是流体对流、矿物沉淀发生的重要机制;详释了构造控制流体输运的方式及过程,高渗透率断裂是流体汇聚的有利场所,从而渗透率等控制成矿的关键参数成为成矿预测的主要指标.     

构造-流体-成矿体系的反应-输运-力学耦合模型和动力学模拟

建立了一个综合的构造流体成矿体系的反应输运力学耦合动力学模型。利用有限元方法求解岩石变形、断裂作用和断裂网络统计动力学、流体流动、有机和无机地球化学反应及成岩成矿作用、压力溶液和其它压实力学、热迁移的方程组 ,可以对构造流体成矿体系的动力学演化过程进行 1～ 3维数值模拟。模拟的主要内容是在各种过程耦合作用下描述构造流体成矿体系的主要变量的时空演化 :( 1)与成矿流体的形成和性质有关的变量 ,如地层中矿物 (包括成矿物质 )的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等 ;( 2 )与构造变形和流体运移有关的各变量 ,如应力与变形速率、岩石孔隙度、构造 (断裂 )渗透率等 ;( 3 )与沉淀成矿有关的变量 ,如矿物 (金属矿物和脉石矿物 )的成核速率、各矿物的沉淀量等 ;( 4 )上述各有关变量间的时空耦合关系 ,如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。以湖南沃溪金锑钨矿床为例 ,应用该模型和方法对成矿动力学过程和动力学机制进行了初步的模拟与分析。     

构造成矿非线性动力学:1.递增应力流变学模型

本文提出了构造成矿作用动力学研究的递增应力流变学方法。利用该方法将构造变形、应力、流体流动、地球化学反应及成岩成矿作用等多过程耦合起来，可以从多种地质过程的耦合与反馈作用对构造成矿的动力学演化过程进行１～３维数值模拟。模拟的主要内容是在各种过程耦合作用下，以下描述构造成矿体系的主要变量的时空演化：（１）与成矿流体的形成和性质有关的变量，如地层中矿物（包括成矿物质）的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等；（２）与构造变形和流体运移有关的各变量，如应力与变形速率、岩石孔隙度、构造（断裂）渗透率等；（３）与沉淀成矿有关的变量，如矿物（金瞩矿物和脉石矿物）的成核速率、各矿物的沉淀量等；（４）上述各有关变量间的时空耦合关系，如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。     

构造-流体-成矿体系的耦合动力学:以湘西金矿为例

热液矿床特别是脉状金矿床受构造的控制明显。主要产于断层、剪切带中或其附近。构造变形在增高岩石渗透率、驱动流体流动汇聚和控制金的成矿过程中起了重要作用。同时,流体可以促进岩石构造变形,流体流动与矿物沉淀可堵塞流动通道而影响成矿的寿命。因此,近年来人们开始将构造变形、流体流动和成矿作用作为一个统一的体系,研究它们之间的相互作用和耦合关系。     

构造-流体耦合有限元模拟:以石英脉型钨矿为例

热液矿床成矿作用动力学过程涉及多时空高度耦合的物理和化学过程。数值模拟是研究这一复杂动力学过程的重要而有效的工具之一,也可在找矿预测等方面发挥重要作用。以南岭地区石英脉钨矿床为例,利用计算机求解控制构造-流体的物理和化学方程,定量揭示成矿热液聚焦流动与"五层楼"成矿的对应关系,正演高压成矿流体致使围岩发生水力破裂及其成矿效应。模拟结果与石英脉型钨矿床的构造地球化学特征相符。     

构造成矿非线性动力学:2.湘西金矿研究实例

应用递增应力流变学方法对湘西沃溪金矿成矿过程中构造变形、应力、流体流动、地球化学反应及成岩成矿作用等多过程间的耦合作用和非线性特征进行了模拟和分析。构造压溶作用对矿源层中成矿物质的溶解与迁移起了重要作用。断裂作用可以产生比原岩渗透率高近4个数量级的断裂渗透率,从而促进流体的流动、组分扩散和在断裂中的汇聚成矿。不同岩性对断裂作用和断裂渗透率的演化有重要影响,并且构造、流体、岩石之间存在强烈的非线性耦合作用,马底驿组中段是最有利的构造成矿层位。     

构造体制转换与流体多层循环成矿动力学

基于成矿系统动力学研究进展的综合分析, 认为构造体制转换与流体多层循环成矿动力学研究是地球科学跨世纪的重要前沿领域之一, 进而提出这一领域的研究主题和关键问题、研究思路及方法, 阐释其重要意义, 指出构造体制转换与流体多层循环成矿动力学研究以构造演化、流体活动及区域地球化学和地球物理不均一性为基础, 通过变形-流动高温高压实验及计算机数值模拟再现成矿作用过程和机理, 解析构造体制转换与流体多层循环成矿动力学特征, 揭示成矿界面时-空演化规律, 建立成矿系统物质和能量交换-反馈耦合成矿的定量模型.这是深化矿床成因认识的重要基础和实现科学找矿的有效途径, 对地球系统科学和大陆动力学的研究也具有重要意义.      

德兴斑岩铜矿床断裂与侵入体产状对成矿的控制作用:从力-热-流三场耦合数值模拟结果分析

斑岩矿床的成矿机制是一种典型的力-热-流多物理场耦合的岩浆-热液过程,因而从成矿动力学数值计算模拟的角度研究斑岩矿床成矿作用过程,对揭示斑岩岩浆-热液系统动力学演化机制及其成矿响应情况具有十分重要的意义。德兴铜矿(包括朱砂红、铜厂和富家坞)作为目前中国华南已发现的最大斑岩型铜矿床,是研究(大型/超大型)斑岩矿床成矿作用过程的一个典型的重要窗口。前人已在矿床地质、地球化学、年代学、同位素以及成矿流体等诸多方面开展了大量的研究工作,但从成矿动力学数值模拟的角度对德兴铜矿成矿作用过程进行的研究目前相对较少。为此,本文以德兴斑岩铜矿床为主要研究对象,首先通过总结分析其成矿过程的地质概念模型,进而将侵入体形态(包括长轴及短轴长度)和倾伏角、控矿断裂倾角与宽度作为几何模型中的变量,构建由这些变量组合控制的几何实体模型。在此基础上,进一步分析斑岩矿床成矿过程数值模拟中应力场、流体场以及热力场三者的耦合关系及其数学-物理方程,构建德兴斑岩铜矿床的成矿动力学模型,建立相应的有限元数值模拟模型。最终,设置不同的岩石物理参数、边界条件与初始条件,进行力-热-流三场耦合的数值模拟实验,并根据不同侵入体产状及断裂构造条件下的模拟结果探究德兴铜矿床断裂和侵入体产状对成矿的控制作用。主要结论如下:(1)较小的断裂构造宽度更易造成岩矿石局部破裂,便于流体弥散而形成浸染状或微-细脉状的斑岩矿化;(2)较大体积的岩体以及较小的岩体倾伏角度对斑岩铜矿床的形成相对有利;(3)朱砂红矿床较铜厂和富家坞矿床岩体体积小,而倾伏角相对较大,导致岩体冷却速度快,表面及附近扩容空间小,因而成矿深度大,而金属储量小。揭示了德兴铜矿床斑岩侵入体与断裂构造产状的控矿机制,增进了对德兴铜矿矿床成因和控矿要素的认识。     

基于FLAC3D的成矿过程模拟研究现状

20世纪90年代以来,数值模拟技术在地学领域得到了广泛应用,该技术是进行成矿过程模拟研究的重要方法。在数值模拟研究中,FLAC3D软件具有解决非线性、大变形问题的显著优势。介绍了数值模拟技术的研究进程,详细论述了基于FLAC3D的成矿过程模拟技术的研究现状。目前,国内对成矿过程模拟的研究相对较少,要实现构造变形、孔隙流体流动、热量传递和化学反应4个过程的完全耦合仍是一项艰巨的工作。     

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。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)