新西兰韦斯特兰省南阿尔卑斯山铜金热液体系

新西兰的南阿尔卑斯山是一个现在还在上升的山脉,在阿尔比尼断层附近显示出地热异常,阿尔比尼断层是澳大利亚板块和太平洋板块的分界线。在这个上升带中出现了强烈的热液运动,这种热液运动导致了石英脉中的金属矿化。金的矿化限于绿片岩相的岩石中,而阿尔比尼断层附近的角闪岩相岩石中年轻的石英脉中则富含铜。地下上升的热液和下渗的大气降水溶液之间的相互作用控制着这个复杂的热液体系中金属的搬运活动和沉淀过程。变质热液已与石墨片岩围岩相平衡,并且相对被还原,大气水的渗入和混合增加了氧的活动性而降低了硫的活动性。大气水在下渗过程中被氧化,但温度上升,溶解了一些铜。当这种液体变成还原状态时,溶解的铜便沉淀出来。因此,这个热液体系的中间部分,铜的含量是逐渐增加的,特别是在阿尔比尼断层附近的强烈破碎渗透性较好的岩石中。     

新西兰奥塔戈东部马可罗斯地区石墨片岩中变质金钨矿床的沉积及其物质来源

马可罗斯(Macraes)地区金钨矿床位于奥塔戈(Otago)黑云母片岩中倾角较小的断层体系中。在石英脉和透镜体岩脉的硅化剪切带中及其附近发现有自然金、白钨矿、黄铁矿和毒砂。矿体分布于剪切带中,剪切带与区域性片理的方向接近平行。化学蚀变主要为硅化,另外还有Cr及少量的Sr和Ba。蚀变从主要岩脉向外延伸大约只有5m左右。当热液向温度低的(250℃?)岩石渗透时,由于温度降低,所以离开岩脉,氧的分布比较均匀。剪切带岩石中的石墨的反射率为6％～7％(在油中),与奥塔戈中一高级变质片岩中石墨类似,据推测这种石墨来源于变质作用。这种石墨当金在逆断层体系中沉淀的过程中起着还厚剂的作用,而逆断层体系穿切了石墨片岩成了输送变质热液的通道。这些金属来自下部的片岩,可能也来自逆断层上部的富含金属的洋壳岩石的集合体。     

布什维尔德杂岩UG—2铬铁岩层中亲铜元素和铂族元素的分布

绪言 Hiemstra(1985)曾在有关UG—2层的研究中指出,铂族元素浓度的对数值随高度(从铬铁岩底部升高某一距离后的高度)直线下降。铂族元素的这一关系早已由有关元素分馏的瑞利定律所预言。然而,亲铜元素镍和铜的行为并不与此相似,尽管它们与UG—2层和梅林斯基层中的铂族元素通常有着很好的相关关系。这种区分即使存在的话大概也被随后     

Hydrogenated polycyclic aromatic hydrocarbons and the 2940 and 2850 wavenumber (3.40 and 3.51 micron) infrared emission features

The 3150-2700 cm-1 (3.17-3.70 microns) range of the spectra of a number of Ar-matrix-isolated PAHs containing excess H atoms (Hn-PAHs) are presented. This region covers features produced by aromatic and aliphatic C-H stretching vibrations as well as overtone and combination bands involving lower lying fundamentals. The aliphatic C-H stretches in molecules of this type having low to modest excess H coverage provide excellent fits to a number of the weak emission features superposed on the plateau between 3080 and 2700 cm-1 (3.25 and 3.7 microns) in the spectra of many planetary nebulae, reflection nebulae, and H II regions. Higher H coverage is implied for a few objects. We compare these results in context with the other suggested identifications of the emission features in the 2950-2700 cm-1 (3.39-3.70 microns) region and briefly discuss their astrophysical implications.     

Calculations of ion-molecule deuterium fractionation reactions involving HD

Gas-phase chemical models of deuterium fractionation in dense interstellar clouds utilize a small number of exothermic reactions to achieve fractionation. Although HD is a major repository of deuterium, it appears not to exchange deuterium with many molecular ions. Useful semiquantitative reasons have been given for the unusual lack of reactivity of exothermic ion-HD deuterium exchange systems, but quantum chemical studies are needed to understand these ideas in more detail and to determine if the lack of reactivity pertains at very low temperatures not studied in the laboratory, or whether tunneling can drive the reactions. Accordingly, the potential energy surfaces of three representative ion-molecule exchange reactions involving protonated ions (H3+, CH3+, HCO+) and HD have been investigated with ab initio quantum chemical techniques. Our results generally confirm the semiquantitative picture as to which reactions are likely to occur and show that tunneling at low temperatures is unlikely to alter this picture.     

New emission features in the 11-13 micron region and their relationship to polycyclic aromatic hydrocarbons

If the "11.3 microns" emission feature seen in the spectra of many planetary nebulae, H II regions, and reflection nebulae is due to polycyclic aromatic hydrocarbons (PAHs), then additional features should be present between 11.3 and 13.0 microns (885 and 770 cm-1). Moderate-resolution spectra of NGC 7027, HD 44179, IRAS 21282+5050, and BD + 30 degrees 3639 are presented which show that the "11.3 microns" feature actually peaks at 11.22 microns (891 cm-1). The spectra also show evidence of new emission features near 11.9 and 12.7 microns (840 and 787 cm-1). These are consistent with an origin from PAHs and can be used to constrain the molecular structure of the family of PAHs responsible for the infrared features. The observed asymmetry of the "11.3 microns" band is consistent with the slight anharmonicity expected in the C--H out-of-plane bending mode in PAHs. Laboratory experiments show that the intensity of this mode relative to the higher frequency modes depends on the extent of molecular "clustering." The observed strengths of the "11.3 microns" interstellar bands relative to the higher frequency bands are most consistent with the features originating from free molecular PAHs. The intensity and profile of the underlying broad structure, however, may well arise from PAH clusters and amorphous carbon particles. Analysis of the 11-13 microns (910-770 cm-1) emission suggests that the molecular structures of the most intensity emitting free PAHs vary somewhat between the high-excitation environment in NGC 7027 and the low-excitation but high-flux environment close to HD 44179. Finally, a previously undetected series of regularly spaced features between 10 and 11 microns (1000 and 910 cm-1) in the spectrum of HD 44179 suggests that a simple polyatomic hydride is present in the gas phase in this object.     

Infrared emission from comets

A brief discussion of the infrared observations from 4 to 20 micrometers of seven comets is presented. The observed infrared emission from comets depends primarily on their heliocentric distance. A model based on grain populations composed of a mixture of silicate and amorphous carbon particles in the mass ratio of about 40 to 1, with a power-law size distribution similar to that inferred for comet Halley, is applied to the observations. The model provides a good match to the observed heliocentric variation of both the 10 micrometers feature and the overall thermal emission from comets West and Halley. Matches to the observations of comet IRAS-Araki-Alcock and the antitail of comet Kohoutek require slightly larger grains. While the model does not match the exact profile and position of the 3.4 micrometers feature discovered in comet Halley, it does produce a qualitative fit to the observed variation of the feature's strength as a function of heliocentric distance. The calculations predict that the continuum under the 3.4 micrometers feature is due primarily to thermal emission from the comet dust when the comet is close to the Sun and to scattered solar radiation at large heliocentric distances, as is observed. A brief discussion of the determination of cometary grain temperatures from the observed infrared emission is presented. It is found that the observed shape of the emission curve from about 4 to 8 micrometers provides the best spectral region for estimating the cometary grain temperature distribution.     

Distinguishing between natural and aquaculture-derived sediment concentrations of heavy metals in the Broughton Archipelago, British Columbia

Marine sediment samples were collected in the Broughton Archipelago, British Columbia, to assess the use of a geochemical normalization technique in the identification of a chemical tracer of aquaculture waste material. Zinc and copper were suggested as tracers of feed pellets, while copper was considered an indicator of anti-foulant agents used on netpen systems. The sediment samples were analyzed for carbon, nitrogen, organic matter, water, trace-element, and free sulfide concentrations, and sediment grain-size distribution. Sediment texture analysis revealed a wide range of substrate types from sand to silty loam categories. Strong relationships between sediment texture, sediment porosity, and organic content were observed across both near-field and far-field stations. Excess zinc and copper sediment concentrations, identified using a lithium-normalization technique, were restricted to near-field sampling stations (0 and 30m from netpen systems). The relationships between these metal tracers and organic content and sulfur concentrations were explored to account for variations in sediment concentrations of zinc and copper.     

Assessment of the historical trace metal contamination of sediments in the Elizabeth River, Virginia

Two sediment cores (Southern Branch, PC-1, and Western Branch, WB-2) were taken from the highly industrialized Elizabeth River, Virginia. The concentrations of trace metals cadmium, cobalt, chromium, copper, nickel, lead and zinc, major elements iron, manganese and aluminum, organic carbon content and the specific surface area of the sediments were determined in each of the cores. Down-core variations in metals varied significantly in each core with maximum contamination events occurring at different times in different portions of the river. In PC-1, maximum metal concentrations were seen after the appearance of (137)Cs. In contrast, the highest levels in WB-2 occurred well before the appearance of (137)Cs. Although stricter environmental regulations have caused a decrease in metal concentrations since the 1980s, the concentrations in the surface sediments of many trace metals were elevated to levels 2-5 times higher than the levels at the bottom of the cores in both the Southern and Western Branches of the river.