Petrographic and mineralogical evidence of felsic and mafic magmas interaction in the potudan pluton, Voronezh crystalline massif

Abstract

Potudan pluton was discovered within the Khokhol-Repyevka batholith of Pavlovsk granithoid complex in the Don belt of Voronezh crystalline massif. Here we present a first detailed petrographic, mineralogical and geochemical study of the Potudan rock suite and comparison with the other coeval magmatic rocks in the region. Separate stocks of the pluton with a total area of 15 km2 are composed mainly of massive equigranular dark rocks differentiated from quartz monzogabbro to granodiorites. Porphyritic foliation rock varieties with hybridism signatures of the mafic rocks and host granitoid are sporadically observed. The Potudan pluton rocks are ferroan, metaluminous, high-K calc-alkaline and span a wide range in SiO2 contents from 49,1 to 63,9 wt.%, showing a distinct composition from the regional complexes. The crystallization condition of the Potudan pluton are P = 2,7–3,2 kbar, T (°С) from 1047–1154 °С to 713–851 °С. The obtained parameters (high initial temperatures and pressure) are comparable with the PT-conditions of Pavlovsk complex granitoids. Mineralogical and petrographic features of the Potudan pluton, such as the normally and reversely zoned plagioclase with a sharp change in composition from the crystal core to rim, sieved plagioclase, quartz and/or feldspar oikocrysts, acicular apatite, together with the indications of gabbroid and host granitoid hybridism suggest that the mafic and felsic magmas were mixed in different proportions within the upper crustal conditions.