Statistical estimation of typochemical features of quartz of granite pegmatis

A significant amount of genetic information on the evolution of the granitic-pegmatite system was obtained by studying quartz. Modern ideas about the quartz's typochemysm are determined by the structural features of the mineral, as well as by the chemical elements that make up the solid and gas-liquid inclusions. The object of the research was quartz from pegmatites of different formations: crystalline, rare-metal, rare-earth (amazonite) and miarolic from Pamir, Altai, western Tian Shan. 30 impurity elements (excluding lantanoids) were found in quartz from pegmatites. 90-95 % of overall weight fall on Li, Mn, Ti, Zn, Sr, Ba, Rb, Cs and around 1 % on rare-earth elements. To assess distribution patterns of impurity elements in quartz, a regressive meta-analysis of data and the Box-Cox method of transformation were applied. Calculations of the linear Pearson correlation coefficient have shown that there is a correlation relationship between 27 pairs of elements. Basically, these connections have positive dependencies. Negative correlation is typical for (Ti4+-Ge4+), (Ge4+-Sr2+), (Ti4+-Li+ ), (Ti4+-Al3+). The results of canonical analysis showed that the presence of Li and Ge on 91 % affects the presence of B, Al and Ti in quartz. It is established that the schemes of heterovalent isomorphism in quartz are confirmed by the positive correlation of the elements (for example, ((B3+-Li+ ),(Al3+-Na+ ), etc.) The presence of Ga, Ge, B, Al, Sn, and others in quartz is possible only in the presence of alkali metals, especially Na. The inverse relationship between Ge and Ti, which can enter the quartz structure in place of Si by isovalent substitution scheme, is controlled by Li and Na. These elements in the pegmatite system serve as a geochemical criterion determining the presence of Ti or Ge in the quartz structure The content in quartz of Ti and Ge, their ratio (Ge/Ti) is considered as an indicator of differentiation of the acid melt (0.033 and 0.309 for quartz from biotite granites and aplite) [Jacamon, 2009]. The values of Ge/Ti in quartz of pegmatites, as late differentiates of acid melt, vary in wide aisles (for crystalline quartz 0.266, for quartz of rare-metal pegmatites of the Mandal field up to 1.124). Ge/Ti ratio in quartz of micaceous pegmatites is 0.001. A mineralogical criterion (based on quartz) for determining the formational affiliation of pegmatites was developed. The nature of the distribution of impurity elements in quartz makes it possible to distinguish two fields according to the geochemical criterion: a certain and an uncertain separation of pegmatites of different formations. Individuals from rare-metal pegmatites and miarolic pegmatites (zones with Li-mineralization quartz-elbaite and quartz-albite-lepidolite mineral aggregates) fall into the fields of confident separation. Quartz from rare-metal paragenetic associations has increased contents of rare alkalis (Cs, Rb), as well as Ba, Mn, Sn.

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