Home – Home – Jornals – Russian Geology and Geophysics 2003 number 9

Under consideration is the geology and geochemistry of the granitoid rocks (from gabbro to leucogranite) making up a large Early Paleozoic batholith of the Kuznetsk Alatau. The early (progressive) stage of batholith formation was due to magmatic substitution and partial melting of the metabasite crust under the effect of a subalkaline mantle-derived magma. The rocks formed at this stage are exocontact hornfelses and endocontact hybrid diorites and monzonite of hybrid habit. The transitions between these rocks are illustratively displayed in the pattern of distribution of rare-earth elements. The next (regressive) stage was due to the differentiation of a monzonitoid melt and its crystallization, which proceeded against the background of a considerable decrease in alkalinity of the residual melt and led to the formation of the main facies rock variety - granodiorite-tonalite. It is characterized by higher contents of Ba, Sr, B, and IGE, lower contents of K, Li, Rb, and Cs, and by very low concentrations of Be, Sn, W, Nb, and Ta as compared with palingenic granitoids of other regions.
The granitic magma was generated in a separate chamber and was not produced by differentiation of a granodiorite melt. In composition, the hornblende-biotite granites are close to trondhjemites (Na/K > 1). A small volume of the residual melt formed during the fractionation of the granitic magma appeared in the stocks and dikes of subalkalic leucogranites.
The presence of postbatholith dikes of basic and intermediate compositions and their closeness to the composition of monzonitoid rocks of batholith suggest that a deep-seated source of magma (and heat) had existed for a long time. The postbatholith dikes of quartz porphyries (ongonites) are characterized by higher, as compared with the other rocks of the batholith, contents of rare ore elements (Rb, Be, B, Sn, Nb, Ta, F) and higher temperatures of formation, which reflects the metamagmatic (fluid-magmatic) stage and is typical of the granites of the same kind in regions of