http://www.sciencedirect.com/science/article/pii/S1674987114000218

Fluid infiltration into retrograde granulites of the Southern Marginal Zone(Limpopo high grade terrain)is exemplified by hydration reactions.shear zone hosted metasomatism,and lode gold mineralisation.Hydration reactions include the breakdown of cordierite and orthopyroxene to gedrite kyanite,and anthophyllite,respectively.Metamorphic petrology,fluid inclusions,and field data indicate that a low H_2O-activity carbon-saturated CO_2-rich and a saline aqueous fluid infiltrated the Southern Marginal Zone during exhumation.The formation of anthophyllite after orthopyroxene eslablished a regional retrograde anthophyllite-in isograd and occurred at P-T conditions of- 6 kbar and 610 C,which fixes the minimum mole fraction of II.0 in the CO_2-rich fluid phase at- 0.1.The maximum H_2O mole fraction is hxed by the lower temperature limit(~800℃) for partial melting at ~0.3.C-O-H fluid calculations show that the CO_2-rich fluid had an oxygen fugacity that was 0.6 log10 units higher than that of the fayalite-magnetitequartz buffer and that the CO_2/(CO_2+CH_4) mole ratio of this fluid was 1.The presence of dominantly relatively low density CO_2-rich fluid inclusions in the hydrated granulites indicates that the fluid pressure was less than the lithostatic pressure.This can be explained by strike slip faulting and/or an increase of the rock permeability caused by hydration reactions.     

中国大陆科学钻探工程主孔地下流体特征及与地震活动的关系初步研究

收集了中国大陆科学钻探主孔工程(CCSD)主孔中117～2045 m深度地下流体某些组分(He、 Ar、 CO₂、 CH₄)的浓度资料和2001年7月1日至2002年4月30日时间段内钻孔周围500 km范围内震级M_L≥1.0地震目录资料, 对其流体资料进行日均值处理、 差分分析和最大相关系数处理。 由日均值浓度看出地震前后He、 Ar、 CO₂、 CH₄浓度存在明显异常; 最大相关系数分析表明, CH₄和CO₂组分两者相关性好, 最大相关系数平均值为0.95, 均方差为0.08, 说明两者可能具有相同的来源。 CH₄和CO₂浓度日均值最大相关系数在地震前后出现明显的异常波动。 主孔中的地下流体特征及与周围地震活动的对应关系揭示大陆科学钻探主孔中的地下流体异常与区内地震活动可能存在一定关系。     

药剂真空预压排水方法处理废弃泥浆的试验研究

针对温州永嘉世界贸易中心工程钻孔桩的废弃泥浆,通过添加相同的化学药剂结合真空预压采用不同的排水方法进行了模型桶试验,从排水速率、排水总量和含水率等方面对比研究。试验发现：改进排水方法后,废弃泥浆含水率在短时间内（80 h内）从处理前的180%～190%,降低到处理后的60%～80%。研究表明,药剂真空预压改进排水方法后处理废弃泥浆的效果十分显著。     

变质流体地球化学：从静态定性“流”向动态定量

对变质岩的矿物学演化研究使岩石学家和地球化学家认识到,流体流动在变质作用过程中发挥着重要的作用。根据变质矿物共生组合、化学和同位素数据能够鉴别流体在变质体中所流经的区域,确定流体的数量、相对于温度和压力梯度以及岩石接触带的流体流动方向,并确定流体活动的时代。仅在特殊的矿物组合、流体成分、温度和压力条件下,流体可能沿矿物颗粒缝隙的网状交叉的显微通道流动。变质流体流动对于研究地壳的热和质量传输及变形机制和速率有着重要的作用。在各种地壳环境中都存在大量的含水流体,区域和接触变质岩石具有的时间积分流量远远大于紧邻岩石脱水所提供的数量。支持高水流量的证据包括不同学科种类,例如岩石学、矿物学、结构和显微构造以及稳定同位素。渗透率增大可能是促使流体流量变大的主要机制。通过同位素地球化学家与构造地质学家和岩石学家们之间的密切合作,直接对变质岩渗透率增大机制进行实验测定和理论模拟,并在野外检验渗透率增大模型,将有助于理解变质作用的热和流体循环与变形作用之间的关系。     

Impact of wind on the spatial distribution of rain over micro‐scale topography: numerical modelling and experimental verification

The wind‐driven‐rain effect refers to the redistribution of rainfall over micro‐scale topography due to the existence of local perturbed wind‐flow patterns. Rainfall measurements reported in the literature point to the fact that the wind‐driven‐rain distribution can show large variations over micro‐scale topography. These variations should be taken into account in hillslope hydrology, in runoff and erosion studies and in the design of rainfall monitoring networks. In practice, measurements are often not suitable for determining the wind‐driven‐rain distribution. Therefore, a few researchers have employed numerical modelling. In order to provide confidence in using numerical models, experimental verification for a range of different topographic features is imperative. The objective of this study is to investigate the adequacy of a two‐dimensional Computational Fluid Dynamics (CFD) model to predict the wind‐driven‐rain distribution over small‐scale topography. The numerical model is applied to a number of topographic features, including a succession of cliffs, a small isolated hill, a small valley and a field with ridges and furrows. The numerical results are compared with the corresponding measurement results reported in the literature. It is shown that two‐dimensional numerical modelling can provide a good indication of the wind‐driven‐rain distribution over each type of micro‐scale topography that is considered in this study. It is concluded that more detailed verification procedures are currently inhibited due to the lack of available and detailed spatial and temporal rainfall data from field measurements. Copyright © 2005 John Wiley & Sons, Ltd.     

Evolution of pore-fluid pressure during folding and basin contraction in overpressured reservoirs: Insights from the Madison–Phosphoria carbonate formations in the Bighorn Basin (Wyoming,USA)

Reconstructing the evolution of paleofluid (over)pressure in sedimentary basins during deformation is a challenging problem, especially when no hydrocarbon-bearing fluid inclusions are available to provide barometric constraints on the fluid system. This contribution reports the application to a natural case (the Bighorn Basin) of recent methodological advance to access fluid (over)pressure level prevailing in strata during sub-seismic fracture development. The fluid pressure evolution in the Mississippian-Permian Madison–Phosphoria limestone reservoir is tentatively reconstructed from the early Sevier Layer Parallel Shortening to the Laramide folding in two basement-cored folds: the Sheep Mountain Anticline and the Rattlesnake Mountain Anticline. Results point out that supra-hydrostatic pressure values prevail in the limestone reservoir during most of its whole Sevier–Laramide history. The comparison of the reconstructed fluid overpressure values within situ measurements in various overpressure reservoirs in other oil-producing basins highlights that the supra-hydrostatic fluid pressure gradually reaches the lithostatic value during the whole basin contraction and fold development. During most of the LPS history, however, overpressure level can be defined by a mean gradient. Among the factors that control the pressure evolution, the mechanical stratigraphy, the stress regime under which fractures developed and regional fluid flow are likely dominating in the case of the Bighorn Basin, rather than classical factors like disequilibrium compaction or fluid generation during burial. A coeval evolution between fluid overpressure and differential stress build-up is also emphasized. The approach presented in this paper also provides estimates of strata exhumation during folding.     

Removal of sediments from the Alleppey nearshore region during post-mud bank formation

Formation of mud banks along the southwest coast of India is marked by an unusual calmness of the nearshore area with a large amount of suspensates in the water column and mud deposition. After cessation of the monsoon, the removal of mud from the mud bank region is evident. Sediment dynamics worked out from the textural characteristics suggest resuspension of sediments by waves and subsequent transportation of the suspended load by longshore/coastal currents as the main factors responsible for the removal of sediments from the mud bank region during the post-monsoon season.     

苏北平原龙冈LG孔晚第四纪地层与环境演化记录

通过研究已经获得的苏北平原龙冈LG孔岩芯野外描述、照片、粒度、¹⁴C测年、有孔虫、孢粉、重矿物等原始测试分析数据,并参考邻区发表成果和该区新近补充的资料数据,再分析和讨论了LG孔的地层层序、年代框架和环境演化记录等内容。结果表明：① LG孔34.8 m岩芯保存了MIS 4以来沉积环境演化记录,先后经历了河漫滩、河湖相洪泛平原（第二硬黏土层）、较开放潮滩的潮间带和潮下带、较开放潮滩的潮下带、较开放潮滩的潮间带和潮上带下部、河湖相洪泛平原（第一硬黏土层）、潮上带滨海沼泽和海岸沙堤等一系列环境演化过程,其中潮滩环境的MIS 3海侵层发育;② 西冈贝壳沙堤龙冈段的全新统厚度很薄,一般在10 m以内,由于LG孔可见两个硬黏土层,应位于古河间地而非下切古河谷区,且以其第一硬黏土层顶面作为全新统底界更为合理,故原报道该孔全新统厚达25 m难以成立;③ 老于末次冰盛期的常规和加速器¹⁴C测年数据皆存在着不同程度的误差和不确定性,加之淤泥和钙质结核等测年材料易受污染等,故LG孔第二硬黏土层中的2个¹⁴C测年数据明显偏年轻,皆不宜用于解释地层年代。     

Experimental Investigation into the Scale Dependence of Fluid Transport in Heterogeneous Rocks

We investigated the dependence of hydraulic properties on the spatial scale of intrinsic and artificial heterogeneity, applying harmonic pore pressure testing to two varieties of Fontainebleau sandstone at various periods and effective pressures. Blocks with porosities of about 5 and 8% were chosen exhibiting a permeability of about 2·10⁻¹⁹ and 1·10⁻¹³ m², respectively. The permeability of the less permeable variety strongly depends on sample size. Artificial heterogeneous rock samples were prepared by stacking pieces of the two sandstone varieties perpendicular and parallel to the main flow direction. The perturbation of the fluid flow owing to the interfaces between pieces of the same variety is controlled by the orientation of and subordinately by the effective stress on the interfaces. Constraints on conduit geometry derived from the effect of interfaces indicate that interconnectivity is more important than pore radius at the lower porosity. The effective permeability of alternating stacks of the two varieties differs tremendously for the two interface orientations; arithmetic and harmonic averages coincide with the effective properties parallel and perpendicular to the main flow, respectively. When the oscillation period is varied two regimes are observed, one with constant permeability at long periods and a second with decreasing permeability for decreasing period at short periods. Order of magnitude considerations of penetration depth suggest that this period dependence may be related to heterogeneity.     

Fluid–rock interaction at a carbonatite-gneiss contact, Alnö, Sweden

We evaluate balanced metasomatic reactions and model coupled reactive and isotopic transport at a carbonatite-gneiss contact at Alnö, Sweden. We interpret structurally channelled fluid flow along the carbonatite-gneiss contact at ～640°C. This caused (1) metasomatism of the gneiss, by the reaction: ${\hbox{biotite} + \hbox{quartz} + \hbox{oligoclase} + \hbox{K}_{2} \hbox{O} +\,\hbox{Na}_{2}\hbox{O} \pm \hbox{CaO} \pm \hbox{MgO} \pm \hbox{FeO} = \hbox{albite} + \hbox{K-feldspar} + \hbox{arfvedsonite} + \hbox{aegirene-}\hbox{augite} + \hbox{H}_{2} \hbox{O} + \hbox{SiO}_{2}}We evaluate balanced metasomatic reactions and model coupled reactive and isotopic transport at a carbonatite-gneiss contact at Aln?, Sweden. We interpret structurally channelled fluid flow along the carbonatite-gneiss contact at ∼640°C. This caused (1) metasomatism of the gneiss, by the reaction: , (2) metasomatism of carbonatite by the reaction: calcite + SiO₂ = wollastonite + CO₂, and (3) isotopic homogenization of the metasomatised region. We suggest that reactive weakening caused the metasomatised region to widen and that the metasomatic reactions are chemically (and possibly mechanically) coupled. Spatial separation of reaction and isotope fronts in the carbonatite conforms to a chromatographic model which assumes local calcite–fluid equilibrium, yields a timescale of 10²–10⁴ years for fluid–rock interaction and confirms that chemical transport towards the carbonatite interior was mainly by diffusion. We conclude that most silicate phases present in the studied carbonatite were acquired by corrosion and assimilation of ijolite, as a reactive by-product of this process and by metasomatism. The carbonatite was thus a relatively pure calcite–H₂O−CO₂–salt melt or fluid.