The history of the United States cent revealed through copper isotope fractionation

Copper isotope fractionation in United States cents traces changes in the source of copper and identifies historical events. Application of copper isotopes as a geochemical tracer requires consistent isotopic signatures of the ores and refined metals. Overlapping isotopic signatures of crushed ores, chalcocite and refined metal extracted from Morenci, Arizona indicate modern mining processes that produce distinguishable single ore deposit geochemical signatures. The coincidence of copper isotope ratios in metals and ore deposits also exists within the United States cents analyzed here. Specifically, historical records confirm two different sources for copper in cents from 1800 through 1867. The copper isotope composition of the 1828, 1830, 1836, 1838 and 1843 cents coincides with the Cornwall ores of England, and cents post 1850 (1859, 1862) correspond with the Michigan ores of the United States. Three of the thirty-six post 1867 cents measured possess fractionated copper isotope ratios and indicate the change in source of copper for the United States cent.     

科学发展观的形成背景与历史地位--兼与赵凌云、张连辉先生商榷

科学发展观是当代中国富有创造性的发展理论,是新中国成立以来的第四代发展观.马克思主义发展观、苏联发展观和当代国外发展观,是新中国成立以来的发展观演变特别是科学发展观提出的理论背景.科学发展观在发展目标上具有全面性,在发展方式上具有统筹性,在发展目的上具有人本性.     

三峡地区次生堆积剖析的考古学实践

一、前言 在田野考古发掘过程中,经常遇到的地层学现象是“早期堆积在下面,晚期堆积在上面;晚期的堆积叠压或打破早期的堆积。”①但是,考古实践中也有与此相反的情况,即上文化层及遗物早于下文化层及遗物,呈现出一种与常规地层学相悖的现象。这就不能不引起我们的思考。     

Salinity structure of the central North Slope foreland basin, Alaska, USA: implications for pathways of past and present topographically driven regional fluid flow

Previous studies of the areal variation in heat flow in the National Petroleum Reserve Alaska (NPRA) support the existence of an active topographically driven regional fluid flow regime in this central part of the North Slope foreland basin. Drilling records and wireline logs for over 30 wells drilled in the NPRA provide additional field information, which can be used to further constrain interpretation of the pattern of regional flow of basinal waters within the NPRA. Hydraulic heads estimated from drilling mud weights show that ground water flow occurs generally from south to north, but with divergence to the north‐east and north‐west away from the central part of the NPRA towards coastal areas of elevated shallow heat flow. Salinities calculated from SP logs range from less than 1 g L^?1, to marine values of 35 g L^?1, to hypersaline values of over 150 g L^?1. The entire upper sedimentary section to a depth of 2 km or more in the eastern part of the NPRA has been preferentially flushed with meteoric water through an area corresponding to the sandiest portion of the Nanushuk group. Deeper areas of low salinity occur within the Sadlerochit and Lisburne sections. The pattern of regional flow in the east is complicated, however, by the presence of a large mass of hypersaline water at depth. It is not known whether these brines are being displaced laterally and upward towards the discharge end of the basin or whether fresher waters are simply riding up over the top. Deep, hypersaline waters also occur in fault slices in the Brooks Range and have survived meteoric flushing. The brines were probably formed at the time of deposition of the Lisburne carbonates. The fluid flow regime to the west is different. Low‐salinity waters may be flowing northward underneath this section through the Ellesmerian section and discharging upward nearer the coast. However, sparse well log control severely limits what can be deduced about the details of flow paths in the central and western parts of the NPRA.     

Factors controlling free thermal convection in faults in sedimentary basins: implications for the formation of zinc–lead mineral deposits

Stratiform sediment‐hosted Zn–Pb–Ag mineral deposits constitute about 40% of the Earth's zinc resources ( Allen 2001 ), and in most cases their genesis involves the discharge of basinal brines near or on the seafloor through syndepositional faults ( Sangster 2002 ). From the point of view of base metal exploration, it is therefore essential to identify all possible faults that formerly carried the upwelling ore‐forming solutions during mineralising events. This paper presents a numerical investigation of the relative importance of various physical parameters in controlling fluid discharge, recharge and heat transport in faults. A two‐dimensional, free convection of pure water, hydrogeological model is developed for the McArthur basin in northern Australia based on the surface geology, known stratigraphic and structural relationships and regional geophysical interpretations. Numerical experiments and sensitivity analyses reveal that faults with strong initial heat input, due to depth of penetration or magmatic activity, are the most likely candidates to carry discharge fluids to the sites of metal precipitation. Deeper, wider and more permeable faults are more likely to behave as the fluid discharge pathways, whereas shallow, narrow or less permeable faults act as marine water recharge pathways. Compared with these fault‐related factors, aquifer physical properties are less important in determining fluid flow patterns and the geothermal regime. These results are an important step in understanding hydrothermal fluid flow in sedimentary basins in order to develop effective exploration criteria for the location of stratiform Zn–Pb–Ag deposits.     

Roman Builders Facing the Risk of Disaster: Coupling Archaeological and Geochemical Analyses on a Section of the ‘Aqua Augusta’ (the Roman Serino Aqueduct,Southern Italy)

Four samples of carbonate sinters from two sites of the Roman Serino aqueduct were studied in order to better constrain the history of the aqueduct and to estimate to what extent natural hazards can be recorded in such deposits. Micromorphological observations, trace element, stable oxygen and carbon isotope analyses were performed on the samples. Together with new quantitative observations on the construction techniques of the aqueduct, our results highlight the imprint left by geological hazards on the Serino aqueduct. Damage, disruption, ground movement and a debris‐flow are evidenced.     

元大都孔庙、国子学的建筑模式与基址规模探析

本文依据文献史料,对元大都孔庙、国子学的建设过程进行梳理,对建筑平面进行复原,确定其用地范围与基址规模,并通过分析探寻其设计规律与手法,发现设计中采用两套平格网．孔庙、国子学的基址规模与大都城市平格网的基准长度存在倍数关系,基址边界均在11步×12．5步的平格网线上;建筑群内部的平面布置受8步×10步的平格控制,总平面中重要控制线大多与网格线对应。根据这一规律,本文进一步对明清北京孔庙、国子监进行分析,发现明太祖、英宗两朝对元代孔庙、国子学展拓时,基址规模仍受元大都城市平格网控制,而永乐朝重建孔庙时沿用元代8步×10步的平格网,将东西廊庑分别向内收进一格,从而揭示元、明建筑模式与基址规模的内在一致性。     

殷墟小屯宫殿宗庙区甲组夯土基址的处理与加固保护

田野考古发掘的夯土建筑基址是文化遗产的重要组成部分,也是近年来文物保护领域的重点研究对象之一。殷墟宫殿区内发掘的夯土建筑,作为一种特殊历史文物,是见证人类社会发展的重要实物。保护和利用好现有的遗址,有着十分重要的历史意义和现实意义。根据保护土质文物的原则和要求,经过针对相关样品的分析测试,在取得一定经验的基础上,使用土质文物加固剂对建筑基址进行了全面的处理和保护。     

郑州商城始建年代研究

二里冈下层地层普遍叠压郑州商城内城墙,内城存在大量洛达庙文化遗存及其宫殿基址,郑州商城内城应建于洛达庙类型的晚段,郑州商城郭城建立于二里冈下层一期。     

New insights from reactive transport modelling: the formation of the sericitic vein envelopes during early hydrothermal alteration at Butte, Montana

A reactive transport computer code has been employed to model hydrothermal alteration of a granitoid rock bordering a discrete vein channel. The model suggests that the grey sericitic and sericitic with remnant biotite alteration envelopes at the porphyry copper deposit at Butte, Montana, can be formed by a reducing, low pH, and low salinity fluid under constant temperature and pressure conditions of approximately 400 °C and less than 100 MPa during a time span of approximately 100 years or less. Hydrothermal alteration has little effect on the porosity of the host rock (Butte Quartz Monzonite), and the diffusivity of the aqueous species also changes little. A sequence of mineral reaction fronts characterizes the alteration envelopes. The biotite dissolution front occurs closest to the vein channel and marks the transition from the grey sericitic to sericitic with remnant biotite envelope. The plagioclase dissolution front occurs farthest into the matrix and marks the edge of relatively fresh Butte Quartz Monzonite. From the properties of the quasi‐stationary state approximation ( Lichtner 1988 ; Lichtner 1991 ), it follows that once the sequence of reaction fronts is fully established, their relative locations remain constant and the widths of the reaction zones increase with the square root of time.