The influence of pressure on the OH valence vibration of zoisite

The influence of pressure on the OH-stretching vibration of zoiste has been studied by single crystal high pressure infrared spectroscopy. A band related to the OH-stretching vibration displayed a linear shift from 3170 cm^?1 at 1 bar to 2795 cm^?1 at 116 kbar. The half-band width increased linearly with respect to pressure from 60 cm^?1 at 1 bar to 500 cm^?1 at 116 kbar. The strength of the absorption of this band is strongly frequency dependent. The high-energy shift of a band at around 2200 cm^?1 on pressure increase indicates that this band is not due to a second OH-stretching vibration as previously suggested by Langer and Lattard (1980).     

Gedanken über die tektonische und geomorphologische Entwicklungsgeschichte der Ostalpen im Jungtertiär

Ohne Zusammenfassung     

Transport von Feldspäten und Quarz im Temperaturgefälle

In the attempt to study the composition and behaviour of metasomatically active solutions we have examined the kind of gaseous solutions which are formed by water in contact with the minerals of a granite under a pressure of 2000 bars at 600° C, and how these solutions behave within a temperature gradient at the same pressure. The temperature ranged from 620° to 180° C. The following minerals were considered: quartz, K-feldspar (adularia), plagioclase (andesine) and mixtures of quartz with adularia, quartz with andesine, quartz with adularia and andesine, quartz mixed with mierokline-perthite, oligoelase and biotite.All these minerals are completely dissolved by water under these physical conditions. The solutions always contain more silica than the minerals, if quartz is present. The dissolved components are transported within the temperature gradient. In the solutions, Ca derived from the anorthite-component of the plagioclase and Mg from the biotite form associations together with silica, which travel tohigher temperatures. There they crystallize in form of wollastonite and/or diopside. On the other hand, Na and K, AI and the Fe from the biotite and the largest part of the silica, travel from the 600° C-region tolower temperatures. There they crystallize in form of quartz, K-feldspar, albite, some muscovite and Mg-free biotite rich in Fe. In experiments of only short duration, metastable analcime instead of albite has been formed. In long lasting experiments of 10 weeks, a separation of Na and K was evident: Albite was formed in the temperature range 470° to 420° C, whereas K-feldspar (with some albite component) and Mg-free biotite crystallize together with quartz in a larger temperature range below 420° C; see figure 6.The different minerals from a mixture influence each other's solubility in such a way that the amount of both feldspars and quartz dissolved and transported within a unit of time is decreased. Compared with the amount obtained when quartz alone constitutes the solid phase, only 40 % of that amount is dissolved and transported when the quartz had been mixed with adularia; the value amounts to only 30% when it was mixed with andesine. When both feldspars. are present together with quartz, the amount of dissolved and transported quartz is decreased to about 20 % of the original amount; see table 7. However, in all cases the amount of dissolved quartz is larger than the sum of the dissolved feldspar substances. Thus, the solution formed from a mixture of quartz and feldspars which is transported to lower temperatures always contains more silica than the mineral mixture. The amount of adularia dissolved and transported is reduced by the presence of quartz to 1/6 of that amount furnished at 6000 C by adularia alone. Under the same conditions the amount of andesine is reduced to one half. — The amount of adularia transported per unit of time is nearly equal to the amount of plagioclase components if quartz is present. However, if no quartz is present, the proportion of dissolved and transported adularia to plagioclase-components is noticeably shifted in favour of adularia. This would be the case with syenite as the source for the solutions.In the attempt to produce skarns in a way closely related to nature, silica-rich solutions from a granite have been brought into contact with dolomite. The contact was situated at 600°, 570° and 500° C. With equal duration of the experiments, the results were similar. With different durations the following effect was observed: at the beginning, the silica-rich solution reacts with the dolomite under formation of forsterite, calcite and C0₂. When more materialis transported into the contact,region diopside (the mineral containing more silica) is formed from calcite, forsterite and additional silica. When the same metasomatically active solution meets a marble, (contact at 600° C) wollastonite is formed. In these metasomatic processes the partial pressure of C0₂ in the gasphase remained low under our experimental conditions.     

四川北部米仓山地区下三叠统内部不整合面的发现及其意义

前人认为四川北部米仓山地区下三叠统内部各组地层之间是整合接触,然而通过构造和沉积学的研究发现下三叠统内部(奥伦尼阶)存在一个区域不整合面。在沉积上表现为环米仓山地区广泛发育的陆相和海相碎屑岩,与下伏地层呈不整合接触。地震剖面上表现为不整合面上下的变形特征不一致、不整合面下部地层被削截、古构造的存在等等,通过对古褶皱和古断裂的平面投影,发现古构造走向为东-西向,与勉略构造带走向一致。综合区域大地构造历史,笔者认为在早三叠世奥伦尼期(约249.7～245.0Ma)南秦岭造山带和上扬子地块就已经发生碰撞,碰撞引起了米仓山地区强烈的构造变形,形成这一区域不整合面。该碰撞时间不一定是南秦岭造山带和上扬子地块在此处的初始碰撞时间。     

Atomistic model of diopside-K-jadeite (CaMgSi<Subscript>2</Subscript>O<Subscript>6</Subscript>-KAlSi<Subscript>2</Subscript>O<Subscript>6</Subscript>) solid solution

Atomistic model was proposed to describe the thermodynamics of mixing in the diopside-K-jadeite solid solution (CaMgSi₂O6-KAlSi₂O₆). The simulations were based on minimization of the lattice energies of 800 structures within a 2 × 2 × 4 supercell of C2/c diopside with the compositions between CaMgSi₂O₆ and KAlSi₂O₆ and with variable degrees of order/disorder in the arrangement of Ca/K cations in M2 site and Mg/Al in Ml site. The energy minimization was performed with the help of a force-field model. The results of the calculations were used to define a generalized Ising model, which included 37 pair interaction parameters. Isotherms of the enthalpy of mixing within the range of 273–2023 K were calculated with a Monte Carlo algorithm, while the Gibbs free energies of mixing were obtained by thermodynamic integration of the enthalpies of mixing. The calculated T-X diagram for the system CaMgSi₂O₆-KAlSi₂O₆ at temperatures below 1000 K shows several miscibility gaps, which are separated by intervals of stability of intermediate ordered compounds. At temperatures above 1000 K a homogeneous solid solution is formed. The standard thermodynamic properties of K-jadeite (KAlSi₂O₆) evaluated from quantum mechanical calculations were used to determine location of several mineral reactions with the participation of the diopside-K-jadeite solid solution. The results of the simulations suggest that the low content of KalSi₂O₆ in natural clinopyroxenes is not related to crystal chemical factors preventing isomorphism, but is determined by relatively high standard enthalpy of this end member.     

Determination of radionuclides in water at uranium mining remediation – a comparison of analytical methods

The corporate purpose of Wismut GmbH is to decommission its former mining holdings and to rehabilitate the landscape and the environment. Sample taking and analysing the value of contaminants are necessary steps for the remediation of waste rock piles, the recycling of contaminated areas, controlled flooding of uranium mines. Main emphasis lies on the determination of heavy metals and radionuclides of natural decay chains of U‐238 and U‐235. Yearly about 60 000…70 000 determinations of radionuclides in waters were done. Facing this high output of determinations it is a permanent task for laboratory and quality management to ask: Are the results of different methods comparable to each other? Is there a preferred analytical technology? Which matrix influences exist? and What about the analytical costs? Answers to these important questions are given in this report. Summarizing our investigations done in the last few years it is possible to say that – by using different analytical methods the results of radionuclides in water samples (surface or groundwater) are comparable, – a not negligible influence of Ra‐223, Ra‐224 and Ra‐228 may exist by using the DIN 38404 C18 method to determine Ra‐226, – a preferred method cannot be defined, – the choice of the analytical method should include analytical questions (the sample matrix, the occurrence of other disturbing radionuclides, the necessary detection limit) and economical questions (costs, other parameters to be determined).     

Reconstruction of erythemal UV irradiance and dose at Hohenpeissenberg (1968–2001) considering trends of total ozone, cloudiness and turbidity

Summary Erythemal ultraviolet (UV) doses reaching the earths surface depend in a complex manner on the amount of total ozone, cloud cover, cloud type and the structure of the cloud field. A statistical model was developed allowing the reconstruction of UV from measured total ozone and a cloud modification factor (CMF) for the GAW site Hohenpeissenberg, Germany (48°N, 11°E). CMF is derived from solar global radiation G, normalized against a Rayleigh scattering atmosphere. By this way the complex influence of the cloud field is accounted for by introduction of a measured parameter, exposed also to this complex field. The statistical relations are derived from the period 1990–1998 where UV measurements and relevant meteorological parameters are available. With these relations daily UV doses could be reconstructed back to 1968. Tests show that the model works remarkably well even for time scales of a minute except for situations with high albedo. The comparison of measured and calculated UV irradiances shows that the model explains 97% of the variance for solar elevations above 18° on average over the period 1968–2001. The reconstruction back to 1968 indicates that maximum UV irradiances (clear days) have increased due to long-term ozone decline. Clouds show seasonally depending long-term changes, especially an increase of cirrus. Consequently the UV doses have increased less or even decreased in some months in comparison to the changes expected from the ozone decline alone. In May to August total cloud frequency and cloud cover have decreased. Therefore, the average UV doses have increased much more than can be explained by the ozone decline alone. It is also shown that the optical thickness of cirrus clouds has increased since 1953. The higher frequency of cirrus is caused in part by more frequent contrails. Besides that an observed long-term rise and cooling of the tropopause favors an easier cirrus formation. However, whether climate change and an intensification of the water cycle is responsible for the cirrus trends has not been investigated in detail.