The metavolcanic rocks in the Gorzów Wielkopolski area (NW Poland) are andesite-basalts and andesites derived from contaminated within-plate subalkaline basalt melts. K-Ar dating of primary K-feldspar yields an extrusion age of 285±5 Ma. This new date suggests that these rocks may be the youngest dated Permo-Carboniferous volcanic rocks within the eastern margin of the North German Basin.
Petrological and micro-thermometric data indicate that the volcanic rocks were altered by a sub-greenschist facies, metamorphic process that proceeded within temperatures and pressures ranging from 195-290°C and 63-96 MPa, respectively. The major metamorphic phases, corrensite, pumpellyite, laumontite and prehnite, formed due to interaction between the original volcanic rock and low-saline Na2SO4-rich hydrothermal fluids. Numerical modelling indicates fluid flow in fractures as the most probable explanation for the low-grade hydrothermal metamorphism. Model calculations suggest that the process was of short duration,