Effects of fluid production on fluid flow during regional and contact metamorphism

Numerical and analytical models of fluid flow that account for fluid production during prograde regional and contact metamorphism show that expulsion of metamorphic fluids dominates the convective flux when crustal permeabilities are less than 0.1–100 μD, depending primarily on the rate of fluid production. When this is the case, fluid circulation is limited or prevented, fluid pressures are elevated above hydrostatic values, and flow throughout most of the model is up and away from the region of maximum fluid production. Fluid circulation is predicted to occur where permeability is high, in dry rocks, or after rates of fluid production decrease as peak temperatures are reached. Large changes in the pattern of flow and influx of externally derived fluids may thus occur in metamorphic terranes when dehydration wanes or ceases and cooling begins. Inclusion of an impermeable horizon in the models further inhibits fluid circulation. Earlier, shallow hydrothermal models and interpretations based on the Rayleigh number may be inappropriate for characterizing fluid flow during prograde metamorphism at depth because they do not account for fluid production.     

含油气盆地中热流体活动的流体包裹体依据

为寻找含油气盆地中热流体活动的证据,根据国内外含油气盆地中与热流体有关的包裹体的对比研究,阐述了流体包裹体宿主矿物产状、形貌特点及均一温度实测值高异常等特征。研究表明,脉体矿物多数是与热流体活动有关的包裹体的宿主矿物,有些碎屑矿物成岩愈合微裂隙中的包裹体也与热流体活动有关。沸腾包襄体反映了油气成藏与热流体的脉动式活动密切相关。流体包裹体的均一温度高异常是由热流体活动所导致的。因此,流体包裹体研究对识别古热流活动具有重要的指示意义。     

Reconciling fluid inclusion types,fluid processes,and fluid sources in skarns: an example from the Bismark Deposit,Mexico

The Bismark deposit (8.5 Mt at 8% Zn, 0.5% Pb, 0.2% Cu, and 50 g/t Ag) located in northern Mexico is an example of a stock-contact skarn end member of a continuum of deposit types collectively called high-temperature, carbonate-replacement deposits. The deposit is hosted by massive sulfide within altered limestone adjacent to the Bismark quartz monzonite stock (~42 Ma) and the Bismark fault. Alteration concurrently developed in both the intrusion and limestone. The former contains early potassic alteration comprising K-feldspar and biotite, which was overprinted by kaolinite-rich veins and alteration and later quartz, sericite, and pyrite with minor sphalerite and chalcopyrite. Prograde exoskarn alteration in the limestone consists of green andradite and diopside, and transitional skarn comprising red-brown andradite, green hedenbergite and minor vesuvinite, calcite, fluorite, and quartz. The main ore stage post-dates calc-silicate minerals and comprises sphalerite and galena with gangue pyrite, pyrrhotite, calcite, fluorite, and quartz. The entire hydrothermal system developed synchronously with faulting. Fluid inclusion studies reveal several distinct temporal, compositional, and thermal populations in pre-, syn- and post-ore quartz, fluorite, and calcite. The earliest primary fluid inclusions are coexisting vapor-rich (type 2A) and halite-bearing (type 3A; type 3B contain sylvite) brine inclusions (32 to >60 total wt% salts) that occur in pre-ore fluorite. Trapping temperatures are estimated to have been in excess of 400 °C under lithostatic pressures of ~450 bar (~1.5 km depth). Primary fluid inclusions trapped in syn-ore quartz display critical to near critical behavior (type 1C), have moderate salinity (8.4 to 10.9 wt% NaCl equiv.) and homogenization temperatures (Th) ranging from 351 to 438 °C. Liquid-rich type 1A and 1B (calcite-bearing) inclusions occur as primary to secondary inclusions predominantly in fluorite and show a range in Th (104–336 °C) and salinity (2.7–11.8 wt% NaCl equiv.), which at the higher Th and salinity ranges overlap with type 1C inclusions. Oxygen isotope analysis was carried out on garnet, quartz, and calcite (plus carbon isotopes) in pre-, syn-, post-ore, and peripheral veins. Pre-ore skarn related garnets have a δ¹⁸O_mineral range between 3.9 and 8.4‰. Quartz from the main ore stage range between 13.6 and 16.0‰. Calcite from the main ore stage has δ¹³C values of –2.9 to –5.1‰ and δ¹⁸O values of 12.3 to 14.1‰, which are clearly distinct from post-ore veins and peripheral prospects that have much higher δ¹⁸O (16.6–27.3‰) and δ¹³C (1.3–3.1‰) values. Despite the numerous fluid inclusion types, only two fluid sources can be inferred, namely a magmatic fluid and an external fluid that equilibrated with limestone. Furthermore, isotopic data does not indicate any significant mixing between the two fluids, although fluid inclusion data may be interpreted otherwise. Thus, the various fluid types were likely to have formed from varying pressure–temperature conditions through faulting during exsolution of magmatic fluids. Late-stage hydrothermal fluid activity was dominated by the non-magmatic fluids and was post-ore.     

Raman microspectrometry of fluid inclusions

For many kinds of fluid inclusions, the coupling of microthermometry and Raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions. A review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation, analytical conditions and methodology of the application of Raman microspectrometry to gaseous, aqueous and hydrocarbon inclusions, and their daughter minerals.     

Ion probe and fluid inclusion evidence for co-seismic fluid infiltration in a crustal detachment

We have investigated the geochemical pattern of fluid infiltration in the extensional detachment of Tinos Island (Cyclades, Greece). Ion microprobe O-isotope analyses and fluid inclusion studies have been conducted in strain fringes developing around pyrite blasts in the mylonite of the shear zone. Micro-scale traverses in quartz and calcite fibres show that δ¹⁸O increases from 17–18 to 20–21‰ in 1 mm towards the blast, drops of 3‰ in ∼200 μm, then rises again in the direction of growth. δ¹⁸O variations are interpreted as transient influxes of exotic fluids into the shear zone between periods of closed system buffering by the host rock. Fluid inclusions trapped in the fibres show fluctuating salinities (0–4 wt% NaCl eq.) and densities that reflect drops of the pore pressure from lithostatic (λ=1) to hydrostatic (λ=0.4) values during fringe growth. Isotopic and microthermometric data are consistent with models of seismic pumping developed for compressive shear zones. We therefore suggest that co-seismic pore pressure variations developed suction forces sufficient to drive large-scale fluid migration in the Tinos detachment, as in convergent tectonic settings.     

Radiogenic isotopes in fluid inclusions

Radiogenic isotopes studied in fluid inclusions are still a limited field, with great potential for expansion as analytical techniques improve. The main limitation for Sr, Ar and He isotope work is the very small number of radiogenic atoms produced in a typical fluid inclusion. The requirements to analysts are correspondingly high. Examples show that isotopic tracing on fluid inclusion fluids can be a decisive tool in solving geological problems.     

海洋钻探钻井液循环技术

在海洋钻探过程中,钻井液循环方式一直备受关注,在海洋环境保护法和HSE的要求下合理选择钻井液循环技术方法是钻探工程师必须要考虑的问题。本文介绍了浅水钻探、深水钻探钻井液循环技术的发展历史和技术现状,其中包括石油套管循环、双层套管循环、隔水导管循环、隔水管循环、无隔水管循环（RMR）、反循环（RDM）、水力反循环（HRC）以及气举反循环技术,分析了钻井液循环技术的装备结构、施工工艺以及工作原理,提出了海岸工程、近海工程以及深水油气、矿产资源的勘查开发对不同钻井液循环技术的市场和技术需求,以及该类技术在大洋科学钻探中应用的可能性。     

豫西南高庄金矿床流体包裹体组合研究及其成矿流体特征

高庄金矿床形成于华北板块和扬子板块造山后的板内伸展环境,矿体是二郎坪群中充填于平行造山带走向的脆韧性剪切带中的石英-金多金属硫化物矿脉。本次运用"流体包裹体组合"(FIA)方法进行流体包裹体特征研究。研究表明,高庄金矿含矿石英中包裹体主要有CO_2-H_2O型三相包裹体、CO_2包裹体和水溶液包裹体3种类型,其中,CO_2-H_2O型三相包裹体为主体类型,完全均一温度变化范围为286~349℃,w(Na Cleq)为0.41%~4.14%,估算流体密度为0.788~0.874 g/cm3,成矿压力为130~160 MPa,成矿深度为4.8~5.9 km,成矿流体具有中温,富CO_2、低盐度的特征。在同一视域内可见CO2-H2O型三相包裹体和水溶液包裹体共存,均一方式各异,且均有相近的均一温度,指示存在流体不混溶作用。成矿流体中水的δDH_2O=-83.4‰~-76.3‰,δ18OH_2O=5.8‰~7.1‰,显示成矿流体来自于岩浆热液。结合区域构造背景,认为高庄金矿床为形成于华北板块与扬子板块碰撞造山作用后,板块内部构造变形过程中形成的中温岩浆热液型金矿。     

贵州太平洞金矿床流体包裹体特征及流体不混溶机制

太平洞金矿床是兴仁-安龙金矿带灰家堡金矿区的重要卡林型金矿之一。流体包裹体研究证明,石英-黄铁矿阶段(Ⅰ)、石英-黄铁矿-毒砂阶段(Ⅱ)、石英-方解石-雄黄阶段(Ⅲ)的包裹体类型丰富,以气液水两相包裹体、CO₂-H₂O包裹体和纯液相水包裹体为主,CO₂两相包裹体、纯气相有机质包裹体和有机质-H₂O包裹体次之,偶见气液有机质包裹体。由Ⅰ→Ⅱ→Ⅲ阶段,气液水包裹体均一温度(200～260℃→180～240℃→100～160℃)呈现逐渐降低的趋势。在Ⅰ阶段的石英中,只在局部偶见到CO₂-H₂O包裹体和气液两相水包裹体共生;在Ⅱ阶段的石英中,纯液相水包裹体、气液两相盐水包裹体、CO₂-H₂O包裹体、CO₂包裹体及纯气相有机质包裹体共存,它们共生在同一平面中且气液两相盐水包裹体和CO₂-H₂O包裹体测温数据相差不大,说明当时捕获的是不均匀成矿流体,它是由含有机质的成矿流体经历了CO₂-低盐度水的不混溶作用形成的。因而认为,太平洞金矿床中成矿早期流体不混溶作用不明显,主成矿阶段流体的不混溶作用是导致金矿质沉淀的重要原因。     

Hydrothermal fluid geochemistry at the Chah-Firuzeh porphyry copper deposit,Iran: Evidence from fluid inclusions

The Chah-Firuzeh porphyry copper deposit is located in 35 km north of Shahre Babak (Kerman province). It is associated with granodioriteic intrusive of Miocene age which intruded Eocene volcanosedimentary rocks. Copper mineralization was accompanied by both potassic and phyllic alteration. Field observations and petrographic studies demonstrate that the emplacement of Chah-Firuzeh pluton took place in several intrusive pulses, each with associated hydrothermal ore fluid formation that was also associated with hydrostatic pressure increasing respect to that of lithostatic pressure (and fracturing development-relative boiling) by circulated fluid. Copper is concentrated as a very early hydrothermal mineralized phase in the evolution of the hydrothermal system. Early hydrothermal alteration produced a potassic assemblage (orthoclase–biotite) in the central deep part of the stock. Alteration ore fluids could be classify into two groups of liquid-reach, containing solid phases, high temperature (390 to 500 °C) high salinity (more than 60 wt.% NaCl equiv.) and gas-rich, high temperature (311 to 570 °C), no solid phase and with low salinities. These magmatic source fluids illustrate sever boiling process and also are the responsible for the both potassic alteration, quartz group I and II veins and chalcopyrite deposition. Propylitic alteration occurred by the liquid-rich, low temperature (241 to 390 °C) and Ca-rich fluid with meteoric origin. Continuous decreasing temperature let the meteoric water diffusion into the system, mixed with magmatic fluids and descending the salinities down to the 1 wt.% NaCl equiv. and leaching the Cu from vein groups II and III by sever thermodynamic anarchies from potassic to the phyllic alteration zones. Phyllic alteration and copper leaching resulted from the inflow of oxidized and acidic meteoric waters with decreasing temperature of the system followed by the incursion of this fluid into and its convection in upper part of the system. A late episode of boiling occurred in the apical the phyllic zone, and was associated with significant copper deposition. Based on the field observation on sharp alteration and related mineralization, it is possible to conclude that all these procedures have been controlled by local faults that could be active even before the pluton injection. These faults and the new form ones (which have been formed after injection), could crash the hosted rocks, and act as physical dams to restrict and limit the mineralization in special strikes and zones within the Cah-Firuzeh ore deposit.     

Transmantle fluid flows and plume genesis

A mantle plume formation model based on possible migration of fluid in the plastic mantle as subvertical isolated cavities-fractures is offered. Excessive pressure (EP) proportional to the vertical size of the cavity and the difference in fluid and rock densities appears in such cavities under plasticity conditions. The excess of the EP value over rock hardness results in ??fluid fracturing?? (by analogy with hydrofracturing) in the ??head?? and, due to the cavity volume stability, in collapse of the fracture tail providing its movement upwards. Gas emission from the Earth??s core is accompanied by its accumulation at the boundary between the core and the mantle as fluid lenses, which having attained a critical size break through the mantle and migrate to the surface. In fact, a relatively stable fluid flow is created in the mantle heating it up and interacting with it. The flow stops down in the hard lithosphere base and spreads laterally initiating mantle metamorphism and melting accompanied by the formation of magmatic reservoirs massively intruding and flowing out when the critical height is attained.     

绿帘石记录俯冲带变质流体活动

俯冲带是连接地球表生圈层和深部圈层的关键纽带,深刻影响着地球内部的运行方式和人类宜居环境。俯冲板片脱水释放的高压-超高压变质流体控制着俯冲带诸多重要地质过程,如地幔楔交代和部分熔融、岛弧岩浆活动、中/深源地震以及地球内部的元素迁移和分异等等。深入了解这些流体的源区、运移、成分和物理化学条件是理解这些流体性质和行为的前提和关键。绿帘石是俯冲带变质岩中一个常见的含水造岩矿物,具有较宽广的稳定温压范围(绿片岩相-榴辉岩相)、较高的微量元素含量和缓慢的体扩散行为(如Sr、Pb、Th、U、Cr、V和LREE),能够指示俯冲带(多期)变质流体活动和地球化学效应。本文总结了近年来俯冲带变质绿帘石研究的主要进展及其在揭示俯冲带流体活动方面的重要应用,包括探究俯冲带流体的起源、成分特征、运移方式、氧逸度条件、交代效应和多期次结晶行为。这些研究表明绿帘石是一个极好的变质流体活动记录器,能够为理解俯冲带流体活动和深部元素迁移提供关键信息。     

流体不混溶性和流体包裹体

大多数流体包裹体是捕获于均匀体系,但有一部分包裹体捕获自非均匀体系(不混溶体系)。在自然界存在着许多不混溶的过程,这包括基性岩浆和酸性岩浆之间,岩浆与热液,岩浆与CO₂,盐水溶液与CO₂等。液体的不混溶性对于成矿作用十分重要,这方面有3个典型的例子,第一个是金矿的成矿作用与NaCl-H₂O-CO₂体系流体的不混溶有着重大的关系;第二个例子是斑岩铜矿;第三个例子是伟晶岩,发现在伟晶岩演化和成矿作用中存在着岩浆和热液的不混溶作用。实际上不混溶的大部分证据是从流体包裹体的研究中获得的。现在的问题是如何来确定哪些包裹体是从不混溶过程中捕获的。这种捕获于不混溶过程中的流体包裹体怎么来确定他的T_h和成分。这种捕获于不混溶过程中的流体包裹体怎么与"卡脖子"拉伸作用"中捕获的包裹体和捕获自均匀体系的流体包裹体相区分。     

Compaction-driven fluid flow in viscoelastic rock

Abstract

Compaction driven fluid flow is inherently unstable such that an obstruction to upward fluid flow (i.e. a shock) may induce fluid-filled waves of porosity, propagated by dilational deformation due to an effective pressure gradient within the wave. Viscous porosity waves have attracted attention as a mechanism for melt transport, but are also a mechanism for both the transport and trapping of fluids released by diagenetic and metamorphic reactions. We introduce a mathematical formulation applicable to compaction driven flow for the entire range of rheological behaviors realized in the lithosphere. We then examine three first-order factors that influence the character of fluid flow: (1) thermally activated creep, (2) dependence of bulk viscosity on porosity, and (3) fluid flow in the limit of zero initial connected porosity. For normal geothermal gradients, thermally activated creep stabilizes horizontal waves, a geometry that was thought to be unstable on the basis of constant viscosity models. Implications of this stabilization are that: (1) the vertical length scale for compaction driven flow is generally constrained by the activation energy for viscous deformation rather than the viscous compaction length, and (2) lateral fluid flow in viscous regimes may occur on greater length scales than anticipated from earlier estimates of compaction length scales. In viscous rock, inverted geothermal gradients stabilize vertically elongated waves or vertical channels. Decreasing temperature toward the earth’s surface can induce an abrupt transition from viscous to elastic deformation-propagated fluid flow. Below the transition, fluid flow is accomplished by short wavelength, large amplitude waves; above the transition flow is by high velocity, low amplitude surges. The resulting transient flow patterns vary strongly in space and time. Solitary porosity waves may nucleate in viscous, viscoplastic, and viscoelastic rheologies. The amplitude of these waves is effectively unlimited for physically realistic models with dependence of bulk viscosity on porosity. In the limit of zero initial connected porosity, arguably the only model relevant for melt extraction, travelling waves are only possible in a viscoelastic matrix. Such waves are truly self-propagating in that the fluid and the wave phase velocities are identical; thus, if no chemical processes occur during propagation, the waves have the capacity to transmit geochemical signatures indefinitely. In addition to solitary waves, we find that periodic solutions to the compaction equations are common though previously unrecognized. The transition between the solutions depends on the pore volume carried by the wave and the Darcyian velocity of the background fluid flux. Periodic solutions are possible for all velocities, whereas solitary solutions require large volumes and low velocities. © Elsevier, Paris     

Energy parameters of deep fluid systems

Doklady Earth Sciences -     

地热流体成矿作用分析

依据地热流体成矿作用基本要素的特殊性、成矿控制因素及其控矿特点,对地壳演化运动的成矿控制及其规律性等方面进行了较系统的分析。研究结果表明,地热流体是特殊的热液成矿作用类型,与其它成矿作用类型有明显的区别     

Nitrogen-rich fluid in the upper mantle: fluid inclusions in spinel dunite from Lanzarote,Canary Islands

Fluid inclusions, ranging from pure N₂ to pure CO₂, occur in olivine porphyroclasts in spinel dunite xenoliths (chrome-diopside suite) from two localities within the Quaternary to Historic alkaline lavas of Lanzarote, Canary Islands. This is the first report of fluid inclusions containing major amounts of N₂ in mantle xenoliths. The nitrogen-rich fluid inclusions predate at least one generation of nitrogen-free carbon dioxide inclusions; textural evidence indicates that the inclusions were trapped within the upper mantle. Some of the nitrogen-rich fluid inclusions are intimately associated with solid inclusions of spinel. The nitrogen-rich fluid was most likely produced in-situ, by oxidation-dehydration reactions destabilizing ammonium-bearing silicate minerals (phlogopite, amphibole), increasing oxygen fugacity or, possibly, increasing temperature of the mantle. This process could be related to an event of CO₂ and silicate melt injection at 6–8 kbar (Neumann et al., in press), or to some earlier event in the evolution of the mantle beneath Lanzarote. The existence of a N₂-rich fluid phase in at least some mantle lithology(ies) at certain conditions is demonstrated by these data. This discovery has consequences for the understanding of the evolution of the mantle below the Canary Islands, as well as for the global nitrogen budget.     

Preferential water loss from synthetic fluid inclusions

A fundamental question in most fluid inclusion studies is whether inclusions behave as compositionally closed systems after trapping, and, thus, represent samples of the fluid phase(s) present in the system at the time of their formation. This question was addressed in high-temperature laboratory experiments with synthetic fluid inclusions in quartz and it was found that at 825°C the inclusions exhibited open-system behavior with respect to water. Synthetic salt-water fluid inclusions in quartz were reequilibrated for 12 hours to 35 days at 825° C in a dry argon atmosphere under 1.5 kbar confining pressure. These conditions created initial internal overpressures (P _int> P _conf) of 1.5–4 kbar in the inclusions and differential water fugacities in the same sense i.e., fH₂OfH₂O. After 108 hours of reequilibration, preferential water loss had resulted in salinity increases as large as 22 wt% salt (e.g., from 57 to 79 wt% NaCl, as determined from measured temperatures of salt dissolution). Also, following reequilibration, a strong inverse correlation between salinity and inclusion volume was observed, and this trend became more pronounced with increasing reequilibration time. These observations, together with a lack of evidence for selective H₂O removal via hydration reactions, suggest that water loss occurred by a diffusion-related mechanism. Fluxes of 4x10^-11 g/cm²-s and diffusion coefficients on the order of 10^-9 cm²/s are calculated for water loss from the inclusions. The calculated H₂O diffusion coefficient is consistent with the determination of Blacic (1981) derived from hydrolytic weakening experiments, but is much larger than the value obtained by Giletti and Yund (1984) for volume diffusion of oxygen in isotope exchange experiments. These observations suggest that the mechanism of water loss from our synthetic fluid inclusions may have been pipe diffusion along dislocations, subgrain boundaries or other structural defects rather than bulk volume diffusion.The results of this study are relevant to the interpretation of fluid inclusions in quartz from several natural high-temperature environments where water fugacities of included and ambient fluids are known to have evolved along separate paths over geologic time.     

Is natrocarbonatite a cognate fluid condensate?

Natrocarbonatite flows in the crater of the volcano Oldoinyo Lengai (Tanzania) are the only carbonatite magmas observed to erupt and have provided strong arguments in favor of a magmatic origin for carbonatite. The currently favored explanation for the genesis of these carbonatites by liquid immiscibility between a silicate and a carbonatite melt is questioned based on the extremely low eruption temperatures of 544-593 °C and compositional and mineralogical characteristics not in agreement with experimental constraints. Experimental investigations of the relationship between Oldoinyo Lengai natrocarbonatite and related silicate rock compositions do indicate that alkali-bearing peralkaline carbonatite with liquidus calcite can form by liquid immiscibility. At the same time, these experiments result in evidence which speaks against a liquid immiscibility origin for the highly alkaline and peralkaline Oldoinyo Lengai natrocarbonatite. On the carbonatite side of the miscibility gap, fractional crystallization cannot account for a liquid evolution from alkali-bearing peralkaline carbonatite to highly alkaline natrocarbonatite. Such an evolution does not seem to be compatible with the liquidus mineral assemblages and the chemistry of Oldoinyo Lengai natrocarbonatite. No natural silicate magma is known to produce natrocarbonatite compositions by liquid immiscibility. The best interpretation of the Oldoinyo Lengai natrocarbonatite flows involves expulsion of a cognate, mobile, alkaline, and CO₂-rich fluid condensate. This conclusion is supported by recent studies of silicate and carbonatite melt inclusions in minerals of ultramafic alkaline complexes, trace element partitioning, isotopic constraints, and by experimental data on major element partitioning between coexisting H₂O-CO₂-rich fluid and carbonatitic melt. In contrast to all other suggested modes of formation, an origin of Oldoinyo Lengai natrocarbonatite from cognate fluid appears best to be in agreement with the field observations, the petrography, mineralogy, and geochemistry of Oldoinyo Lengai natrocarbonatite and the dynamics of the Oldoinyo Lengai natrocarbonatite extrusion.     

论含油气盆地流体系统

我国含油气盆地地下水系统可分为油田水系统和溶滤水系统,二者之间按电性、富水性和矿化度大致以上、下第三系为界。含油气系统按成藏过程及其地质特征分为生成系统、运移系统和聚集系统。地下水系统是流体系统的主体部分,它包含了含油气系统。油田水系统与含油气系统关系十分密切,油气的生成、运移和聚集过程都是在油田水参与下进行的。溶滤水系统影响并改造着含油气系统,油气藏会在溶滤水作用下遭到破坏。异常高压由排水固结的不均衡所形成,它的存在阻止了油田水向上运移。含油气盆地流体系统研究是现代水文地质学的一个新的研究领域,是油气成藏研究的一种有效途径。