The rocks of the Chupa paragneiss formation are intruded by bodies of gabbroids (gabbro-norites and gabbro-anorthosites), and all of the rocks are metamorphosed. The estimated P–T metamorphic parameters are T = 650–750°C and higher and P = 8–11 kbar. The U–Pb monazite and titanite dates indicate that the early Proterozoic metamorphism and migmatization of the Chupa aluminous gneisses and gabbro-anorthosites occurred 1845 ± 4 Ma (titanite age) and 1855 ± 4 Ma (monazite age). Despite the 10-Ma age difference obtained from the two minerals, they could form during a single event that affected the gabbroids and their host gneisses, and the age difference between the titanite and monazite is a consequence of the lower closure temperature of the U–Pb system of titanite compared to that of monazite. The P–T parameters of metamorphism and migmatization, corresponding to the conditions of the high-temperature amphibolite and low-temperature high-pressure granulite facies, likely pertain to the formation of the Belomorian complex as a foreland structure in the Paleoproterozoic.
Yurchenko et al. (Mon,) studied this question.