Constraints on the ore fluids in the Sando Alcalde AuAg epithermal deposit,southwestern Peru: fluid inclusions and stable isotope data

The Sando Alcalde ore deposit (southwestern Peru) has been studied in order to characterize the physicochemical parameters of the ore fluids and to determine the fluid process (mixing or boiling) which involves the precious metal mineralization. Mineralogy, ${\delta }^{18}{\mathrm{O}}_{\mathrm{quartz}}$ isotopic values and fluid inclusion data give arguments in favour of a boiling phenomenon. This conclusion corroborates fluid inclusion studies previously performed in this area on the low-sulphidation epithermal deposits of Arcata, Orcopampa and Apacheta, where boiling has been described as the main factor for ore deposition. To cite this article: A.-S. André-Mayer et al., C. R. Geoscience 337 (2005).     

长江口动水絮凝沉降与拦门沙淤积的关系

根据１９８２年４月－１９８３年３月长江口南槽３个站位全年逐月大湖的水化学成分、悬沙粒度与粘土矿物资料，１９８４－１９９２年在环形水槽中获得的近百个组次的动水絮凝沉降试验研究资料，以及长江口细颗粒泥沙、浮泥与底质研究成果，对拦门沙形成过程及其机理进行综合研究。     

海洋立管综合环境条件设计标准研究

首先用有限单元法推导海洋输液立管在外界环境荷载条件下的侧向振动微分方程。对渤海某海区的15次风暴过程作了抽样分析，得到以波高为主时的波高、流速序列和以流速为主时的波高、流速序列，并对其进行了Weibull、Gumbel、Lognormal等适线分析，以确定各序列的最优分布形式及相应的特征值。用重点抽样法进行随机模拟得到联合概率为百年一遇的波高的流速。针对线海固定式平台铰接的海洋输液立管，以最大应力为控制条件确定其联合设计标准，并与其它方法作了比较，得到一些有益的结论。     

长江口粘性泥沙在流动盐水中的沉降速度

本文报道了粘性泥沙在流动盐水中的沉降试验,计算了衰减系数、沉降速度。试验结果表明,粘性泥沙的动水絮凝沉速与静水絮凝沉速相比,前者要此后者小得多。本文的结论对长江口工程规划、设计及环境评价等均有参考价值。     

冲绳海槽西部陆坡碎屑沉积物的搬运方式:滑塌和重力流

通过对冲绳海槽2000多公里的实测单道地震资料(95和99航次)和沉积物柱状样(92航次)分析,认为滑塌和重力流是冲绳海槽西部陆坡(东海陆坡)碎屑沉积物向海槽搬运的重要方式;分析结果表明,西部陆坡这两种作用是广泛存在的。陆坡沉积物堆积速率、地形坡度和构造活动、地震、海啸等因素造成了陆坡南、北和中段之间的滑塌和重力流发育程度存在差异。海底滑塌和重力流这两种作用可以同时发生,也可以单独发生,但柱状样揭示重力流发生得更频繁。从空间分布上看,海底滑塌主要分布于上陆坡的断裂带附近,平行海槽呈带状延伸;而重力流沉积主要分布于断裂带向下一直到槽底的部位。重力流沉积主要有4种表现形式：1)沉积物重力蠕动;2)浊积平原;3)透镜状浊积体;4)沿斜坡的碎屑流沉积。上述研究表明,滑塌和重力流不仅是陆架向海槽输送物质的重要方式,也对陆坡沉积结构的塑造起了重要的作用。     

Fault on–off versus coseismic fluids reaction

The fault activation （fault on） interrupts the enduring fault locking （fault off） and marks the end of a seismic cycle in which the brittle-ductile transition （BDT） acts as a sort of switch. We suggest that the fluid flow rates differ during the different periods of the seismic cycle （interseismic, pre-seismic, coseismic and post-seismic） and in particular as a function of the tectonic style. Regional examples indicate that tectonic-related fluids anomalies depend on the stage of the tectonic cycle and the tectonic style. Although it is difficult to model an increasing permeability with depth and several BDT transitions plus independent acquicludes may occur in the crust, we devised the simplest numerical model of a fault constantly shearing in the ductile deeper crust while being locked in the brittle shallow layer, with variable homogeneous permeabilities. The results indicate different behaviors in the three main tectonic settings. In tensional tectonics, a stretched band antithetic to the normal fault forms above the BDT during the interseismic period. Fractures close and fluids are expellecl during the coseismic stage. The mechanism reverses in compressional tectonics. During the interseismic stage, an over-compressed band forms above the BDT. The band dilates while rebounding in the coseismic stage and attracts fluids locally. At the tip lines along strike-slip faults, two couples of subvertical bancls show different behavior, one in dilationJcompression and one in compressionJdilation. This deformation pattern inverts during the coseismic stage. Sometimes a pre-seismic stage in which fluids start moving may be observed and could potentially become a precursor.     

http://www.sciencedirect.com/science/article/pii/S1674987114000449

We review petrologic observations of reaction textures from high-grade rocks that suggest the passage of fluids with variable alkali activities. Development of these reaction textures is accompanied by regular compositional variations in plagioclase, pyroxenes, biotite, amphibole and garnet. The textures are interpreted in terms of exchange and net-transfer reactions controlled by the K and Na activities in the fluids. On the regional scale, these reactions operate in granitized, charnockitized, syenitized etc. shear zones within high-grade complexes. Thermodynamic calculations in simple chemical systems show that changes in mineral assemblages, including the transition from the hydrous to the anhydrous ones, may occur at constant pressure and temperature due only to variations in the H2O and the alkali activities. A simple procedure for estimating the activity of the two major alkali oxides, K2O and Na2O, is imple- mented in the TWQ software. Examples of calculations are presented for well-documented dehydration zones from South Africa, southern India, and Sri Lanka. The calculations have revealed two end-member regimes of alkalis during specific metamorphic processes： rock buffered, which is characteristic for the precursor rocks containing two feldspars, and fluid-buffered for the precursor rocks without K-feldspar. The observed reaction textures and the results of thermodynamic modeling are compared with the results of available experimental studies on the interaction of the alkali chloride and carbonate-bearing fluids with metamorphic rocks at mid-crustal conditions. The experiments show the complex effect of alkali activities in the fluid phase on the mineral assemblages. Both thermodynamic calculations and experiments closely reproduce paragenetic relations theoretically predicted by D.S. Korzhinskii in the 1940s.     

Height prediction of water flowing fractured zones based on BP artificial neural network

Factures caused by deformation and destruction of bedrocks over coal seams can easily lead to water flooding (inrush) in mines, a threat to safety production. Fractures with high hydraulic conductivity are good watercourses as well as passages for inrush in mines and tunnels. An accurate height prediction of water flowing fractured zones is a key issue in today's mine water prevention and control. The theory of leveraging BP artificial neural network in height prediction of water flowing fractured zones is analysed and app-lied in Qianjiaying Mine as an example in this paper. Per the comparison with traditional calculation results, the BP artificial neural network better reflects the geological condi-tions of the research mine areas and produces more objective, accurate and reasonable results, which can be applied to predict the height of water flowing fractured zones.     

太子河本溪城区段河流水生态系统健康评价

太子河作为本溪的主要河流,是本溪工业、农业、生活的主要水源,为了更好的了解太子河本溪城区段的水体情况,以太子河本溪城区段流域为研究对象,基于2017年的平水期（4月）、丰水期（8月）、枯水期（11月）18个监测断面的监测数据,结合太子河本溪城区段的实际情况和特点,利用层次分析法的评价指标体系,对太子河本溪城区段进行水生态系统健康评价。通过比较分析,最终以平水期的评价结果为主,丰水期和枯水期的评价结果为辅。结果表明：仅有22%的监测断面处于健康状态、56%的监测断面处于亚健康状态、22%的监测断面处于一般状态,说明太子河本溪城区段大部分流域处于亚健康状态,水生态系统退化,需要加强管理和治理保护。     

Prediction of Flowing Bottomhole Pressures for Two-Phase Coalbed Methane Wells

A method is proposed to predict the flowing bottomhole pressures(FBHPs)for two-phase coalbed methane(CBM)wells.The mathematical models for both gas column pressure and two-phase fluid column pressure were developed based on the well liquid flow equation.FBHPs during the production were predicted by considering the effect of entrained liquid on gravitational gradients.Comparison of calculated BHPs by Cullender-Smith and proposed method was also studied.The results show that the proposed algorithm gives the desired accuracy of calculating BHPs in the lowproductivity and low-pressure CBM wells.FBHP is resulted from the combined action of wellhead pressure,gas column pressure and fluid column pressure.Variation of kinetic energy term,compressibility and friction factors with depth increments and liquid holdup with velocity should be considered to simulate the real BHPs adequately.BHP is a function of depth of each column segment.The small errors of less than 1.5%between the calculated and measured values are obtained with each segment within 25 m.Adjusting BHPs can effectively increase production pressure drop,which is beneficial to CBM desorption and enhances reservoir productivity.The increment of pressure drop from 5.37 MPa2 to 8.66 MPa2 leads to an increase of CBM production from 3270 m3/d to 6700 m3/d and is attributed to a decrease in BHP from 2.25 MPa to 1.33 MPa.