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煌斑岩、钾镁煌斑岩、金伯利岩及钾霞石质岩、黄长石质岩和白榴石质岩的命名原则与分类尚未完全确定。国际地科联下属火成岩体系分委会为解决上述问题而建立的３个工作组所提出的建议，在此列出来以供讨论。上述岩类新的定义也各以矿物学和地球化学术语给出，并提供了一个其系统分类的改进程序，它可与ＩＵＧＳ已建立的分类体系相结合。 相似文献
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Bond AR 《Post-Soviet geography》1994,35(5):299-305
Location in Russia's economic space plays a major role in the development paths taken by its diverse regions. For example, certain regions on the former Union's periphery may eventually prosper as a result of evolving transborder economic ties. Other peripheries of Russia may well languish. This paper examines what economic transition could mean for one of these latter regions, Kraynyy Sever, the Far North. Kraynyy Sever was an administrative construct during the Soviet period used to delineate an area in which wage increments and costs of living bonuses were applied as part of a program to recruit workers for tours of northern service. These incentives were paid to attract workers to this extremely cold area. The region stretches from the Kola Peninsula in the northwest, across the Nenets okrug and Komi republic, then broadens in Siberia and the Far East to encompass everything north of the 60th parallel. There is a subregion along its southern margin, known as Regions Equivalent to the Far North, in which slightly lower increments and bonuses were paid. There is now an unjustifiably large population in the region and net out-migration appears likely, definitely from areas failing to boast mineral development of world significance. 相似文献
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尽管知道水在俯冲带火山作用的成因中起着重要作用，但对这种作用还了解甚少。在单一压力下俯冲洋壳中的角闪石脱水作用，被假定产生了熔融所需要的水，但对该反应的实验约束条件有限，且很少有人注意涉及其它含水矿物的反应。对海洋玄武岩在相当于俯冲板块的压力－温度条件下的实验证明，角闪石脱水作用至少延续至２０ｋｍ的深度范围。涉及包括云母、绿帘石、硬绿泥石以及硬柱石在内的其它含水矿物的反应同样也是在一个宽的深度范围 相似文献
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概述过去对砂岩型铀矿床的研究很少涉及到矿体以外铀异常的延伸及性质。然而,在扩大矿区时,运用包括矿体和异常晕圈带在内的较大目标将更为方便。此外,航空放射性异常和水化学异常的范围取决于矿体外部和矿体内部的铀的分布情况。作为对砂岩型铀矿床附近沉积岩中铀的区域异常研究的一部分,我们已经得到明确的证据:为形成怀俄明州的那种卷型铀 相似文献
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Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: relevance for interpretation of biomarker records 总被引：9，自引：0，他引：9
Sakata S Hayes JM McTaggart AR Evans RA Leckrone KJ Togasaki RK 《Geochimica et cosmochimica acta》1997,61(24):5379-5389
For the cyanobacterium Synechocystis UTEX 2470, grown photoautotrophically to a logarithmic stage of growth, the total lipid extract is depleted in 13C by 4.8% relative to average biomass. Depletions observed for acetogenic (straight-chain) lipids range from 7.6 (hexadecanoic acid) to 9.9% (a C16 n-alkyl chain bound in a polar-lipid fraction), with a mass-weighted average of 9.1%. Polyisoprenoid lipids fall into two isotopic groups, with phytol, diplopterol, and diploptene depleted by 6.4-6.9% and bishomohopanol (produced from the extracts by the preparative degradation of bacteriohopanepolyol) depleted by 8.4%. Analysis of the pattern of depletions indicates that two carbon positions in each C5 biomonomer leading to polyisoprenoid products are probably depleted in 13C relative to average biomass. The depletion of bacteriohopanepolyol relative to other polyisoprenoids can be ascribed to changes that occur over the life of each cell: (1) the 13C content of carbon flowing to lipid biosynthesis decreases as the cell size increases and (2) a greater proportion of the bacteriohopanepolyol which, unlike other polyisoprenoids, is present mainly in the cytoplasm rather than in membranes and is synthesized when cells are larger. Chlorophyll a is depleted relative to average biomass by O.7%. Given the observed depletion of 13C in phytol, the heteroaromatic, chlorophyllide portion of chlorophyll must be enriched in 13C by 2.7%. This enrichment is large relative to that in chlorophyllides produced by eukaryotes and may be related to a parallel enrichment of 13C in cyanobacterial glutamic acid. As in many previous investigations of cyanobacterial lipids, long-chain n-alkanes (C22-C29) are found in the extracts. They are, however, enriched in 13C relative to biomass and have isotopic compositions suggesting that they are contaminants of petrochemical origin. Available results indicate that cyanobacterial lipids will be depleted relative to dissolved CO2 that has served as a carbon source by 22-30% and that a wider range of depletions will be characteristic of eukaryotic products. The absence of long-chain n-alkanes in cyanobacteria reduces the possibility that petroleum ever formed from pre-eukaryotic sedimentary debris. 相似文献