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
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
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DOI：
10.1134/s0016702916040078
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发表时间：
2016-05
影响因子：
0.8
通讯作者：
G. S. Nikolaev;A. Ariskin;G. Barmina;M. Nazarov;R. Almeev
中科院分区：
文献类型：
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作者：
G. S. Nikolaev;A. Ariskin;G. Barmina;M. Nazarov;R. Almeev
在独立实验数据上对Ballhaus-Berry-GreenOl-OPX-Spoxy气压计(BBG)进行的测试表明，它在温和还原条件下(靠近C-CO缓冲器)高估氧逸度0.6-1.3个对数单位，在还原条件下(在IW缓冲器及其以下)高估2-3个对数单位。建议开发一种新的氧化压力计，以最大限度地减少这种影响，并增强低压矿物组合的氧化还原能力，包括相对于斜方辉石(OPX)不饱和的岩浆熔体。氧气压计的新经验方程适用于大范围的正常碱度的镁铁质-超镁铁质岩浆，包括0.001-25kbar压力和氧逸度IW-3到NNO+1的陆地、月球和陨石系统。所得到的回归与定标数据集的ΔQFM值(15 4个实验)精确到~0.5个对数单位。新的氧压计消除了在评估还原区域(从IW-3到C-CO)和岩浆结晶时的系统误差，而不需要在液相线上进行。(1)低钛月玄武岩，(2)沙茨基隆起拉斑玄武岩，(3)西伯利亚泛滥玄武岩，(4)横科-多维伦侵入体层状系列岩石，(5)采集于西伯利亚南部、蒙古、中国和俄罗斯远东南部的地幔包体。对于经过长期冷却和积云后重新平衡的侵入岩，这种氧气压计所产生的值应该持保留态度。
Testing the Ballhaus–Berry–GreenOl–Opx–Spoxybarometer (BBG) on independent experimental data indicates that it overestimates the oxygen fugacity by 0.6–1.3 log units under mildly reduced conditions (near the C–CO buffer) and by as much as 2–3 log units under reduced conditions (at the IW buffer and below it). A newly developed oxibarometer is suggested to minimize this effect and enhance the capabilities of redoxometry of low-pressure mineral associations, including magmatic melts undersaturated with respect to orthopyroxene (Opx). The new empirical equation of the oxybarometer is applicable to a wide range of mafic–ultramafic magmas of normal alkalinity, including terrestrial, lunar, and meteoritic systems under pressures of 0.001–25 kbar and oxygen fugacity ranging from IW–3 to NNO + 1. The derived regression fits the ΔQFM values of the calibration dataset (154 experiments) accurate to ~0.5 log units. The new oxybarometer eliminates systematic errors when redox parameters are evaluated for the reduced region (from IW–3 to C–CO) and for crystallization of magmas withoutOpxon the liquidus. The efficiency of the suggested model is demonstrated by its application to natural rocks: (1) low-Ti lunar basalts, (2) tholeiites from the Shatsky Rise, (3) Siberian flood basalts, (4) rocks of the layered series of the Yoko-Dovyren intrusion, and (5) mantle xenoliths collected in southern Siberia, Mongolia, China, and the southern Russian Far East. The values yielded by such oxybarometers for intrusive rocks, which underwent long-lasting cooling and postcumulus reequilibration, should be regarded with reserve.