Experimental Investigation of the Melting of Minerals and Rocks

Autor: E. A. Volkova, V. V. Maltsev, R. N. Sobolev
Rok vydání: 2021
Předmět:
Zdroj: Russian Metallurgy (Metally). 2021:102-108
ISSN: 1555-6255
0036-0295
DOI: 10.1134/s0036029521020269
Popis: The melting of a mineral grain and a polymineral rock sample are analyzed. The melting is shown to be a long-term multistage process, which occurs in a certain temperature range and starts in the surface layer of grains. The melting of monomineral fractions (powder, grains), namely, oligoclase, alkali feldspar, and quartz, is studied experimentally. The granitoids and gneisses, from which they are extracted, are also investigated. Heating the rock is shown to melt the minerals that form it at different temperatures. Alkali feldspar in rock samples melts in the temperature range 1000–1160°С. In the range 1160–1350°С, the melt of alkali feldspar interacts with plagioclase grains to form a macrohomogeneous feldspar melt. As the temperature rises above 1350°С the melt starts to react with quartz grains. Thus, the mineral melts at the same temperature exhibit various degrees of disordering. The polymineral rock melts completely at the temperature that is much higher than the melting temperature of a highly-dispersed charge of the same composition. Two mechanisms of melt formation are considered. The melt formation in the case of a single grain can be described as the first-order transition: surface melting → volume melting. In the case of heating the polymineral rock, the lowest-temperature phase melts first. As temperature increases, the melt of the lowest-temperature phase reacts with the surface of high-temperature phases. As a result, melts of intermediate chemical composition form. The melt structure becomes zonal. The following three trends in the melt formation during heating the rock sample are distinguished: (1) trend in a mineral grain, outer → intermediate → inner parts of a grain; (2) trend for gradual mineral transition into the melt, alkali feldspar → plagioclase → quartz; and (3) trend in the rock sample volume, outer → intermediate → inner parts of the sample.
Databáze: OpenAIRE
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