Title

L. N. Sharpenok, A. E. Kostin, E. A. Kukharenko

TAS-diagram alkali sum – silica for chemical classification and diagnostics of plutonic rocks

The TAS-diagram for the initial identification and classification of plutonic rocks is based on a database containing about 11 000 chemical analyzes of plutonic rocks from different regions of the World. The method applied by the authors during detailing of this diagram for acid volcanic rocks is used. For all groups of rocks histograms of distribution frequency for each of the two parameters (SiO2 and ΣAlk) were charted. The areas of maximum concentration of parameters were outlined on the diagram, and the boundaries of fields plutonites were delineated taking into account these areas. Thus, 20 fields for groups of plutonic rocks of various alkalinity and silica were statistically proved.
Key words: TAS-diagram, plutonic rocks, classification of igneous rocks.