Test of the Ballhaus–Berry–Green Ol–Opx–Sp oxybarometer and calibration of a new equation for estimating the redox state of melts saturated with olivine and spinel

摘要: Testing the Ballhaus–Berry–Green Ol–Opx–Sp oxybarometer (BBG) on independent experimental data indicates that it overestimates oxygen fugacity by 0.6–1.3 log units under mildly reduced conditions (near C–CO buffer) and as much 2–3 (at IW buffer below it). A newly developed oxibarometer is suggested to minimize this effect enhance capabilities of redoxometry low-pressure mineral associations, including magmatic melts undersaturated with respect orthopyroxene (Opx). The new empirical equation applicable a wide range mafic–ultramafic magmas normal alkalinity, terrestrial, lunar, meteoritic systems pressures 0.001–25 kbar ranging from IW–3 NNO + 1. derived regression fits ΔQFM values calibration dataset (154 experiments) accurate ~0.5 units. eliminates systematic errors when redox parameters are evaluated for region (from C–CO) crystallization without Opx liquidus. efficiency model demonstrated its application natural rocks: (1) low-Ti lunar basalts, (2) tholeiites Shatsky Rise, (3) Siberian flood (4) rocks layered series Yoko-Dovyren intrusion, (5) mantle xenoliths collected in southern Siberia, Mongolia, China, Russian Far East. yielded such oxybarometers intrusive rocks, which underwent long-lasting cooling postcumulus reequilibration, should be regarded reserve.