地壳中的成矿地质流体体系

本文论述了地质流体研究的学科前缘性．认为地壳中可划分出六大类不同的成矿地质流体体系：（1）与大陆地壳中─酸性岩浆热事件有关的热液流体体系（2）与海底基性火山活动有关的热浪喷流派体体系（3）与海相沉积盆地演化有关的盆地流体体系（4）与区域变质作用有关的变质流体体系（5）与地幔排气过程有关的深部流体体系（6）与大型剪切带的发生演化有关的流体体系并简要讨论了每个成矿流体体系的发生、演化、特征和成矿作用．     

Electrical Structure of the Crust Beneath the Ordos Block

The Ordos block is a stable tectonic unit since the Cenozoic. Whether low-resistivity layers exist in the middle and lower crust of this kind block is an open question. This work attempts to reveal the entire crustal structure of the block based on interpretation of magnetotelluric data collected along the profile across this region. The result shows that a layered structure characterizes the crust of the Ordos block, with a low-resistivity layer at depth of about 20km, presumably associated with fluids there. In contrast, in the areas of active tectonics on the east and west of the block, there are no such layered electric structures in the crust, and the low-resistivity zones may be related to the decollement zones (or ductile shear zones) in the crust. The difference in electric structure of crust between the Ordos Block and neighboring areas is of significance to analyze the movement and deformation of varied blocks in the continent.     

Research Progress on the Problem of Fluid,Heat and Energy Distribution near the Earthquake Source Area

As the basic problems in seismology, fluid, heat and energy distribution near earthquake sources during earthquake generation have been the leading subjects of concern to seismologists. Currently, more and more research shows fluid around earthquake source areas, which plays an important role in the process of earthquake preparation and generation. However, there is considerable controversy over the source of fluid in the deep crust. As for the problem of heat around earthquake source areas, different models have been proposed to explain the stress heat flow paradox. Among them, the dynamic weakening model has been thought to be the key to solving the heat flow paradox issue. After large earthquakes, energy distribution is directly related to friction heat. It is of timely and important practical significance to immediately implement deep drilling in-site surveying to gain understanding of fluid, friction heat and energy distribution during earthquake generation. The latest international progress in fluid, heat and energy distribution research has been reviewed in this paper which will bring important inspiration for the understanding of earthquake preparation and occurrence.     

关于震源附近流体、热和能量分配问题的研究进展

作为地震学的基本问题,地震发生过程中震源附近流体、热与能量的分配问题一直是地震学家关注的前沿课题.目前,越来越多的研究表明震源附近存在流体,且流体在地震的孕育、发生过程中起重要作用,但对深部流体的来源尚存较大争议.对于震源区的热问题,自应力热流佯谬提出以来,不同的模型被用于解释热流佯谬相关问题,其中动态弱化被认为可能是解决热流佯谬的关键.摩擦产生的热能与能量分配问题直接相关,大地震发生后,立即进行深钻现场测量对认识地震发生过程中震源附近的流体、摩擦热能及能量分配问题具有时效性和重要现实意义.本文回顾了国际上有关震源附近流体、热及能量分配问题的最新研究进展,这些问题的研究将对认识地震的孕育和发生过程带来重要启示.     

暴雨触发局部地震活动的一个典型例子:2010年6月广西凌云—凤山交界3级震群活动

在前期严重干旱的背景下,2010年6月27～30日广西西北部出现大暴雨过程,大范围积水成涝.降雨量最大的凌云、凤山交界于6月28日17时开始出现密集的微震活动,形成显著的震群事件.自6月28日至7月15日共记录地震2739次,其中2～2.9级(ML,下同)41次,3级以上地震3次,最大为7月1日10时27分3.2级地震...     

Observations of fluid‐dependent shear‐wave splitting in synthetic porous rocks with aligned penny‐shaped fractures‡

P‐ and S‐wave velocity and attenuation coefficients (accurate to ±0.3% and ±0.2 dB/cm, respectively) were measured in synthetic porous rocks with aligned, penny‐shaped fractures using the laboratory ultrasonic pulse‐echo method. Shear‐wave splitting was observed by rotating the S‐wave transducer and noting the maximum and minimum velocities relative to the fracture direction. A block of synthetic porous rock of fracture density 0.0201 ± 0.0068 and fracture size 3.6 ± 0.38 mm (measured from image analysis of X‐ray CT scans) was sub‐sampled into three 20–30 mm long, 50 mm diameter core plugs oriented at 0°, 45° and 90° to the fracture normal (transversely isotropic symmetry axis). Full waveform data were collected over the frequency range 500–1000 kHz for both water and glycerin saturated cores to observe the effect of pore fluid viscosity at 1 cP and 100 cP, respectively. The shear‐wave splitting observed in the 90° core was 2.15 ± 0.02% for water saturated and 2.39 ± 0.02% for glycerin saturated, in agreement with the theory that suggests that the percentage splitting should be 100 times the fracture density and independent of the saturating fluid. In the 45° core, by contrast, splitting was 0.00 ± 0.02% for water saturation and ?0.77 ± 0.02% for glycerin saturation. This dependence on fracture orientation and pore fluid viscosity is consistent with the poro‐visco‐elastic theory for aligned, meso‐scale fractures in porous rocks. The results suggest the possible use of shear‐ or converted‐wave data to discriminate between fluids on the basis of viscosity variations.     

A model of boiling for fluid inclusion studies: Application to the Bolaños Ag–Au–Pb–Zn epithermal deposit,Western Mexico

Boiling can be inferred from fluid inclusion microthermometry studies when a progressive increase in apparent salinity is observed along with a decrease of homogenization temperature (T_H) and depth, thus reflecting the partitioning of non-volatile solutes into the liquid phase during steam loss. We propose a model for fluid evolution during boiling based on mass and heat balance equations, which establishes paths in the T_H-salinity space that can be compared with fluid inclusion data to confirm or discard boiling. Additionally, the model allows calculating paleo-depths, for which the effect of steam bubbles lowering the hydrostatic pressure is taken into account.     

福建马坑矽卡岩型铁(钼)矿床流体包裹体特征及成矿机制研究

福建马坑矿床是一个大型层控矽卡岩型铁(钼)矿床,赋存于早白垩世莒舟-大洋花岗岩外接触带黄龙组灰岩和林地组碎屑岩层间构造破碎带中.对不同成矿阶段的石榴子石、透辉石、角闪石、石英、方解石和萤石中流体包裹体所进行的岩相学和显微测温研究表明,与成矿有关的包裹体类型主要有富气相水溶液包裹体、富液相水溶液包裹体、含子矿物多相包裹体和少量富CO2包裹体,其中以富液相水溶液包裹体为主.气相组成均以CO2、H2O、N2、O2为主,其次为CH4、C2H4、C2H6和少量C2H2,液相成分中阳离子以Na+、K+和Mg2+为主,其次为Ca2+和少量Li+,阴离子以SO42-、F-、Cl-为主,还含有少量Br-、NO3-,成矿流体应为H2O-NaCl(NaF)±CaCl2(KCl)体系.矽卡岩、退化蚀变、石英硫化物阶段均一温度分别为460～600℃、260～540℃、160～400℃;盐度w(NaCleq)分别为(6％～24％、32％～44％),(4％～16％、36％～44％)和0～4％.H、O、C、S同位素研究表明,矽卡岩期成矿流体主要是岩浆水,晚期石英硫化物阶段混有不同程度的大气降水,流体中碳和硫来自深部或地幔,但也受到围岩等因素的影响.岩浆热液的相分离及其与大气降水的混合作用可能是马坑铁(钼)矿床形成的主要原因.     

哈达特陶勒盖铅锌矿床成矿物理化学条件研究

哈达特陶勒盖铅锌矿床处于华北板块与西伯利亚板块交汇部位,是二连浩特-东乌旗多金属成矿带中新发现的一个中型铅锌矿床.本文在野外地质工作基础上,通过流体包裹体,氢、氧、硫和铅同位素的研究,深入探讨哈达特陶勒盖铅锌矿床形成机制.流体包裹体研究显示,均一温度介于195～408℃之间,均值为332.5℃;盐度介于1.40％～11.93％ NaCleq.之间,均值为4.87％NaCleq.;流体密度介于0.609～0.890 g/cm3之间,均值为0.720 g/cm3;温度直方图显示,流体呈350～370℃和230～250℃两个峰值,其中230～250℃与成矿密切相关,350～370℃则代表成矿早期流体温度.流体形成压力约13.0MPa,推测深度约1.3 km.激光拉曼测试结果显示,成矿流体属H2O-NaCl体系,含有少量的CO2.H、O同位素研究显示,流体演化成矿主要为岩浆水和大气水混合作用;矿石硫、铅同位素组成具有变化范围窄、相对均一的特点(δ34S=4.0‰～6.1‰,206 Pb/204 Pb=18.311～18.467,207 Pb/254 Pb=15.590～15.636,208Pb/204 Pb=38.253～38.393),反映了成矿物质主要来源于岩浆.上述研究表明哈达特陶勒盖铅锌矿属于浅成中温热液矿床.     

新疆东天山东戈壁钼矿矿床地质和地球化学特征

新疆东天山东戈壁钼矿床是迄今为止在我国东天山找到的最大规模的钼矿床,钼矿资源量超过5×10⁵ t。该矿床赋存于花岗斑岩外接触带中,矿石矿物以辉钼矿、黄铁矿为主,围岩蚀变以硅化、钾化、黄铁矿化、电气石化、碳酸盐化和萤石化为特征。其成矿作用可以划分为成矿期和成矿期后两个阶段,成矿温度为140℃～380℃,盐度为0.88～21.33 wt%NaCl,成矿深度为1.76～2.87 km,指示东戈壁钼矿为中低温、中低盐度的浅成矿床。对主要钼矿体8件辉钼矿样品进行Re-Os同位素分析获得的等时线年龄为234.3±1.6 Ma,表明该矿床的成矿时代为印支期。东戈壁钼矿床形成时代的厘定对于提高该矿床的理论研究水平和指导该区隐伏金属矿床的找矿勘查工作均具有重要意义。