Multiple gabbro-granite intrusive series of the Syrostan pluton, southern Urals: Geochemistry and petrology

The Syrostan gabbro-granite pluton is situated immediately to the west of t he Main Uralian Fault and exemplifies a multiple series of five intrusive r hythms. Each rhythm characterizes a separate episode of emplacement of basi c and acid magmas, which ascended from mantle and crustal sources contempor aneously, partly mixed with each other, and solidified in a sequence from b asic to acid rocks according to decreasing solidus temperature. This model is confirmed by geochemical data demonstrating the specific fractionation t rends for basic and acid magmas and the field of intermediate compositions typical of hybrid rocks. Experimental data on late-magmatic epidote stabili ty and the plagioclase-amphibole thermobarometer were used to estimate the PT conditions of magma crystallization. The results obtained indicate the d ecrease in depth of magma solidification from early to late intrusive rhyth ms due to the rise of the magmatic column and the rapid denudation of the o verlying rocks.