Evolution of the transport properties of fractures subject to thermally and mechanically activated mineral alteration and redistribution

Strong feedbacks link temperature (T), hydrologic flow (H), mechanical deformation (M), and chemical alteration (C) in fractured rock. These processes are interconnected as one process affects the initiation and progress of another. Dissolution and precipitation of minerals are affected by temperature and stress, and can result in significant changes in permeability and solute transport characteristics. Understanding these couplings is important for oil, gas, and geothermal reservoir engineering, for CO2 sequestration, and for waste disposal in underground repositories and reservoirs. To experimentally investigate the interactions between THMC processes in a naturally stressed fracture, we report on heated (25°C up to 150°C) flow‐through experiments on fractured core samples of Westerly granite. These experiments examine the influence of thermally and mechanically activated dissolution of minerals on the mechanical (stress/strain) and transport (permeability) responses of fractures. The evolutions of the permeability and relative hydraulic aperture of the fracture are recorded as thermal and stress conditions' change during the experiments. Furthermore, the efflux of dissolved mineral mass is measured periodically and provides a record of the net mass removal, which is correlated with observed changes in relative hydraulic fracture aperture. During the experiments, a significant variation of the effluent fluid chemistry is observed and the fracture shows large changes in permeability to the changing conditions both in stress and in temperature. We argue that at low temperature and high stresses, mechanical crushing of the asperities and the production of gouge explain the permeability decrease although most of the permeability is recoverable as the stress is released. While at high temperature, the permeability changes are governed by mechanical deformation as well as chemical processes, in particular, we infer dissolution of minerals adjacent to the fracture and precipitation of kaolinite.     

中国城市航空运输职能等级及航空联系特征的实证研究

本文依据城市航空运输资料,分析了中国城市航空运输职能等级层次,并揭示了城市航空运输联系所反映出的中国城市体系的宏观特征。     

瓷器热释光高温峰测年的初步研究

对陕西耀州窑4个古瓷器碎片的热释光高温峰测量的结果表明,瓷器样品具有天然热释光信号,而且,其信号增长呈良好的线性,高温峰可以用于瓷器的年龄测定和真假鉴定之中,瓷器热释光高温峰技术有望成为热释光测定瓷器年龄的一个方法。     

Reconstruction of smelting conditions during 16th- to 18th-century copper ore processing in the Kielce region (Old Polish Industrial District) based on slags from Miedziana Góra,Poland

This study presents the first reconstruction of the smelting conditions in 16th- to 18th-century smelters from Miedziana Góra (Holy Cross Mountains, Poland). Based on geochemical (inductively coupled plasma mass spectrometry/emission spectrometry, X-ray fluorescence) and mineralogical analysis (X-ray diffractometry, scanning electron microscopy, electron probe micro-analysis) of historical slags, their chemical/phase composition and the basic smelting parameters (temperature, melt viscosity, and oxygen fugacity) were determined. Due to the differences in chemical and phase composition, slags from different smelting stages have been distinguished: hypocrystalline slags (MG6) from speiss/matte production and glassy (MG1–MG5) from matte conversion. In glassy slags, pyroxenes, quartz/cristobalite grains, and aggregates composed of metallic Cu and PbO are dispersed in the glass. Hypocrystalline slags are composed of wollastonites, anorthites, and metallic Cu. The temperature range at which the slags were formed was from ~1100°C (solidus temperature) to 1150–1200°C (liquidus temperature). The silicate melt's viscosity was from log η = 1.19 to 4.42 Pa s (at 1100–1200°C). The higher viscosity of MG1–MG5 slags indicates that, unlike MG6 slags, they were not formed during gravity separation. Information about the phase composition made it possible to determine the oxygen fugacity in the range of log fO₂ = −4 to −12 atm. High oxygen fugacity indicates the oxidizing nature of the smelting process.     

浅谈书画展室的文物保护

本文就书画展室的文物保护问题进行了探讨,着重分析了影响书画寿命的几项因素,包括温度、湿度、光照、虫霉害等,并据此提出了多方面的保护措施。     

Obsidian hydration dating on the South Coast of Peru

We compare over 230 obsidian hydration readings from 30 individual site components from the Southern Nasca Region (SNR) with independent age estimates based on radiocarbon dates and temporally diagnostic artifacts. Although there are problems with small sample sizes, and readings must be adjusted for elevation, a very strong relationship accounting for nearly 90% of the total variation in the data set is found. This suggests that obsidian hydration dating (OHD) works in the SNR and is a viable means of independently estimating age. Residual values from our regression suggest that hydration age estimates are usually within 15% of the radiocarbon estimates. Finally, we present an equation other scholars can use to estimate age for Quispisisa obsidian in the SNR.     

Red abalone collecting and marine water temperature during the Middle Holocene occupation of Santa Cruz Island,California

Oxygen isotope values derived from prehistoric mussel (Mytilus californianus) shell calcite are used to determine whether sea-surface temperatures in the vicinity of the Punta Arena site (CA-SCRI-109) on Santa Cruz Island, California, were cooler than present between 6300 and 5300 cal BP. This site and others in the western sector of the island dating to this period are distinctive because of the presence of large red abalone (Haliotis rufescens) shells, a species that historically has been subtidal around Santa Cruz and the other northern Channel Islands. Comparison of temperature values derived from archaeological shells with those from modern mussel shells, along with water temperatures derived from satellites, indicates that waters were cooler during the 6300 to 5300 cal BP period. These results are consistent with a previous study and support the interpretation that collection of red abalone during the 6300–5300 cal BP period was partly the result of cooler water temperatures that made this large mollusk more available to foragers in the intertidal or shallow subtidal zone.     

《燕行录》资料反映的16-19世纪东北南部地区冬半年气温变化

朝鲜古汉籍《燕行录》,是历史上朝鲜使臣出使中国的见闻记录,保留有很多历史气候资料,十分宝贵。本文收集了19种《燕行录》中记载的16-19世纪东北南部地区河流封冻情况,并利用中国其它文献为补充,使用现代河流封冻资料为对照,逐年考订了当时河流封冻与现代河流封冻的距平情况,并得出封冻期的50年平均距平值。由于冬半年气温变化是影响河流冰情的关键因素,河流封冻情况的变化可很好地反映该区域冬半年温度变化情况。分析发现,在1500-1900年间,存在3个较冷的时期,其中16世纪上半期是400年中最冷的时期;存在2个较暖的时期,分别为18世纪下半叶和19世纪下半叶。而和20世纪的温度变化衔接分析,则500年间区域气温基本是上升的趋势。同时和中国其它区域以及欧洲的小冰期温度变化序列比较,在大的趋势变化和波动方面有一致性,但在时间上并不完全一致。表明区域间气候变化的复杂性。     

首都博物馆空气中细菌的分离鉴定及 在文物保护中的意义

首都博物馆是北京市的窗口单位,应该营造一个舒适健康的环境, 不仅保护公众健康, 而且有利于文物保存,因此对博物馆内空气中微生物进行分离和鉴定具有重要意义。对首都博物馆内空气中微生物进行采样,分离鉴定优势细菌28株,由形态、生理生化及分子生物学结合鉴定。前两项确定细菌的基本形貌和特征,分子生物学方法得到28株细菌的16S rDNA 序列与 Genbank 中标准序列对比进一步确定种属,鉴定出所有菌与已知菌的同源性均在99%以上,且均为条件致病菌。在正常条件下不能够导致传染类疾病的发生,对观众和工作人员安全。在鉴定细菌种类的同时,根据其固体培养特征和生理生化特点,从现象到机理本质分析了细菌可能对文物造成的危害。以上工作为博物馆空气质量监测、文物保护保存环境提供参考     

Pottery firing temperatures: a new method for determining the firing temperature of ceramics and burnt clay

A new method for determining the maximum firing temperature of ceramics and burnt clay is presented. The technique relies on measuring the magnetic susceptibility on a step-wise re-fired sample. The validity of the method has been tested by determining firing temperatures of two sets of clay samples fired at temperatures ranging from 400 to 1000 °C. Aliquots of the same samples have been studied petrographically by optical microscopy on thin sections and analyzed by powder X-ray diffraction in order to monitor structural and mineralogical changes as a function of temperature. The method is demonstrated on samples from four geographically widely different sites and it is applied to a larger set of ceramics of Late (ca. AD 900–AD 1450) and Inca (ca. AD 1480–AD 1532) periods from the Northwestern Argentine region, dating to a limited period of time prior to the fall of the Inca Empire. The method is shown to be a powerful tool in revealing archaeological information about the change in firing technologies in the pre-Hispanic societies in the Andean area through time.