Zur Stabilität von Margarit im System CaO-Al2O3-SiO2-H2O

An increasing number of occurrences of margarite have been reported in the last years. However, previous experimental investigations in the system CaO-Al₂O₃-SiO₂-H₂O are limited to the synthesis of margarite and to the upper stability limit according to the reaction (1) 1 margarite?1 anorthite +1 corundum +1 H₂O (Chatterjee, 1971; Velde, 1971). Since margarite often occurs together with quartz, the upper stability limit of margarite in the presence of quartz is of special interest. Therefore, the reactions (5) 1 margarite +1 quartz ?1anorthite +1 kyanite/andalusite +1 H₂O and (6) 4 margarite+3 quartz ? 2 zoisite+5 kyanite+3 H₂O were investigated experimentally using mixtures of natural margarite (from Chester, Mass., USA), quartz, kyanite, andalusite, zoisite, and synthetic anorthite. The indicated equilibrium temperatures at water pressures equal to total pressure are: 515± 25°C at 4 kb, 545 ±15°C at 5 kb, 590±10°C at 7 kb, and 650±10°C at 9 kb for reaction (5), and 651±11°C at 10 kb, 648 ± 8°C at 12.5kb, and 643±13°C at 15kb for reaction (6), respectively. Besides this, additional brackets for equilibrium temperatures were determined for the above cited reaction (1): 520±10°C at 3 kb, 580±10°C at 5 kb, and 640± 20°C at 7 kb. On the basis of these experimentally determined reactions (1), (5), and (6) and of the reactions (3) 2 zoisite +1 kyanite? 4 anorthite +1 corundum +1 H₂O (7) 2 zoisite +1 kyanite +1 quartz ? 4 anorthite +1 H₂O and (10) 1 pyrophyllite ? 1 andalusite/kyanite+3 quartz+1 H₂O for which experimental or, in the case of reaction (3), calculated data were already available, a pressure-temperature diagram with 3 invariant points and 11 univariant reactions was developed using the method of Schreinemakers. This diagram, summarizing both experimental and phase relation studies, allows conclusions about the conditions under which margarite has been formed in nature. Margarite is limited to low grade metamorphism at water pressures up to approximately 3.5 kb; in the presence of quartz, margarite is even limited to low grade metamorphism at water pressures up to 5.5 kb. Only at water pressures higher than the values stated before margarite, and margarite+quartz, respectively, can occur in medium grade metamorphism (as defined by Winkler, 1970 and 1973). For the combined occurrence of margarite+quartz and staurolite as reported by Harder (1956) and Frey (personal communication, 1973) it may be estimated that water pressure has been greater than approximately 5.5 kb, wheras temperature has been in the range from 550 to 650°C. Furthermore, the present study shows that the assemblage zoisite+kyanite (+ H₂O) is an indicator of both pressure [P _{H 2 O}> approximately 9kb]and temperature [T> approximately 640 to 650° Cat water Pressures up to 15 kb].     

Abschätzung von Quasarmassen

The masses of quasi-stellar objects having absorption lines with redshifts larger than the redshifts of the corresponding emission lines are attributed to gas clouds which are moving radially against the quasar. Other forces than the gravitational attraction of the quasars are neglected. The average of the mass of a quasi-stellar object is 5 ⋅ 10¹² 𝔐 ⊙.     

X-ray emission – an ageing effect of galaxy clusters (Mitteilungen der Universitäts-Sternwarte zu Jena Nr. 145)

Die Röntgenleuchtkraft L_X und -temperatur T_X von Galaxienhaufen wurden zu dem dynamischen Entwicklungsparameter W in Beziehung gesetzt, den VON HOERNER (1976) eingeführt hat. Offensichtlich ist Röntgenstrahlung eine Alterserscheinung der Galaxienhaufen.