This paper reports testing of seven geobarometers (pyroxene and polymineralic) from five studies (Nimis, 1995; Putirka, 2008; Fumagalli et al., 2017; Ziberna et al., 2017; Wang et al., 2021) on a test set of experimental data (TSED), including results from 64 subliquidus and 31 subsolidus experiments in high-Mg systems (Mg# > 0.63, olivine Fo > 85%) at pressures no higher than 10 kbar. The most consistent pressure estimates were obtained using the temperature-independent Cpx-only geobarometer of Nimis (1995). The use of temperature-dependent geobarometers yielded highly scattered pressure values, even at given experimental temperatures. The same seven geobarometric models were applied to estimate the crystallization conditions of 18 samples of mafic–ultramafic rocks from the Monchegorsk Intrusive Complex in Murmansk region (Russia). The compositions of minerals from plagioclase harzburgite, orthopyroxenite, and melanorite from three locations were used for these calculations: (1) a deep ultramafic body from borehole M-1 cutting the middle and lower zones of the Monchetundra intrusion near its contact with the Monchegorsk pluton; (2) drill cores from borehole M-20 within the Dunite block of the Monchegorsk pluton; and (3) dump piles of Mine No. 5 on Mt. Travyanaya. The barometric calculations gave a wide pressure range from ~1 to 5–6 kbar. The models by Nimis (1995) and Wang et al. (2021) yielded the most consistent values: 1.2 ± 0.5 and 0.6 ± 1.4 kbar for borehole M-1, 1.0 ± 0.4 and 0.8 ± 0.6 kbar for borehole M-20, and 2.3–2.4 kbar for the Mt. Travyanaya peridotites. Additional verification was carried out using a semiempirical Cpx-only geobarometer calibrated by us using the TSED. This geobarometer showed the following values for the same array of natural pyroxene compositions: 0.6 ± 0.6 kbar for borehole M-1, 0.8 ± 0.5 kbar for borehole M-20, and 3.2 ± 1.5 kbar for the Mt. Travyanaya peridotites. Thus, the rocks of the latter location bear evidence for the deepest origin among all rocks of the Monchegorsk pluton, which should be considered during reconstructions of the original position and generalized stratigraphic section of this intrusion.
Eremin et al. (Mon,) studied this question.