Magmatic fluids immiscible with silicate melts: examples from inclusions in phenocrysts and glasses, and implications for magma evolution and metal transport

The first occurrence of immiscibility in magmas appears to be most important in the magmatic–hydrothermal transition, and thus studies of magmatic immiscibility should be primarily directed towards recognition of coexisting silicate melt and essentially non-silicate liquids and fluids (aqueous, carbonic and sulphide). However, immiscible phase separation during decompression, cooling and crystallization of magmas is an inherently fugitive phenomenon. The only remaining evidence of this process and the closest approximation of natural immiscible magmatic liquids and vapours can be provided by melt and fluid inclusions trapped in silicate glasses and magmatic phenocrysts. Such inclusions are often used as a natural experimental laboratory to model the process of exsolution and the compositions of volatile-rich phases from a wide range of terrestrial magmas. In this paper several examples from recent research on melt and fluid inclusions are used to demonstrate the significance of naturally occurring immiscibility in understanding some large-scale magma chamber processes, such as degassing and partitioning of metals.     

袁枚的“诗”“学”观

袁枚针对清诗目益学问化所露出的弊端,抗声提出诗主性灵,非关学问,于是有人误认为以袁枚为代表的“性灵”诗派轻学浅薄,游学无根。事实上袁枚很重视诗歌与学问的关系,他对“诗”与“学”的关系有三个基本主张：一是诗须有学,二是反对在诗中填书塞典,三是主张化学入诗。他的诗歌没有脱离清诗质厚重学的时代特征,不是清诗的变异,而恰好是这个茂盛园圃里敢于争春怒放的花朵。     

Application of tin to ancient pottery

It has earlier been assumed that the tin cover found on certain antique vases has been attached as a thin foil. In this paper it is shown that the metal may simply have been applied by an immersion technique. Before dipping into the tin melt the pottery must be treated with an adhesion promotor. Animal glue which was known as a binder in ancient times has been found to be useful for the surface treatment.     

Melt formation in lime-rich proto-porcelain glazes

Early Chinese lime-rich glazes form an important step in the development of high-fired ceramics. This experimental study, based on the analysis of archaeological samples of proto-porcelain and replicated samples, explores the role of ash and glaze mixture preparation, firing temperature and duration, and cooling protocol for the quality and composition of the resulting glaze. It is demonstrated that the application of raw wood ash rich in potash produces low-potash glazes, that the melt formation follows a cotectic mechanism which needs extended firing times to reach equilibrium, and that the formation of a crystalline interaction layer depends more on the kiln cooling history and high-temperature soaking than on the glaze application method.     

Iron-57 Mössbauer spectral studies of medieval stained glass

⁵⁷Fe Mössbauer spectral data for six excavated and two simulated medieval stained glass samples are reported. Iron-containing precipitates are observed in the two simulated medieval glasses and are responsible for the amber colour of these samples. The ferrous/ferric ratio of the other samples is dependent on the glass composition and glass making conditions. The green glasses are associated with the presence of both ferrous and ferric iron, the ratio being very similar in three of the glasses studied, while in the purple and emerald green glasses the iron which is constitutionally incorporated in the glass is solely in the ferric oxidation state. The UVvisible spectra of some of the glasses are used to assist in interpretation of the colourant action of iron, and the role of Mössbauer spectroscopy in linking separate glass fragments with a common source is also indicated.