Mineral systems based on the number of species-defining chemical elements in minerals: their diversity, complexity, distribution, and mineral evolution of Earth's crust
Krivovichev V. G., Charykova M. V., Krivovichev S. V.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2020. V. 149. N 1. P. 1-22
The chemical diversity of minerals can be analyzed in terms of the concept of mineral systems, defined by the set of chemical elements essential for defining a mineral species. Only species-defining elements are considered to be essential. According to this approach, all minerals are classified into ten types of mineral systems with the number of essential components ranging from 1 to 10. For all known minerals, only 70 chemical elements act as essential species-defining constituents. Using this concept of mineral systems, various geological objects may be compared from the viewpoint of their mineral diversity: for example, alkaline massifs (Khibiny, Lovozero, in Russia, and Mont Saint-Hilaire, in Canada), evaporate deposits (Inder, in Kazakhstan, and Searles Lake, in the USA), fumaroles of active volcanoes (Tolbachik, in Kamchatka, and Volcano, in Sicily, Italy) and hydrothermal deposits (Otto Mountain, in the USA, and El Dragon, in Bolivia). Correlations between chemical and structural complexities of minerals were analysed using a total of 5240 datasets on their chemical compositions and 3989 datasets on crystal structures of minerals. Statistical analysis shows that there are strong and positive correlations (R2 > 0.95) between chemical and structural complexities and the number of different chemical elements in a mineral. Analysis of relations between chemical and structural complexities provides strong evidence that there is an overall trend of increasing structural complexity together with increase of the chemical complexity. Following R.Hazen, there were considered four groups of minerals representing four stages of the mineral evolution: (I) “Ur-minerals”, (II) minerals from chondrite meteorites, (III) Hadean minerals, and (IV) contemporary minerals. Obtained data have showed that the number of species-defining elements in minerals and their mean contents are increasing regularly and significantly from the stage I to stage IV. Analyses of mean chemical and structural complexities in these four groups demonstrate that both are gradually increasing in the course of mineral evolution. The increasing complexity follows an overall trend: the more complex minerals were formed with passage of the geological time, without replacing the simpler ones. Observed correlations between chemical and structural complexities understood in terms of the Shannon information suggest that the chemical differentiation is the major force driving the increase of complexity of minerals in the course of geological time.
Keywords: mineral species, species-defining elements, crystal-chemical formula, mineral systems, structural and chemical complexity, mineral evolution, chemical differentiation