An Extended Calibration of the Olivine-Spinel Aluminum Exchange Thermometer: Application to the Melting Conditions and Mantle Lithologies of Large Igneous Provinces
An Extended Calibration of the Olivine-Spinel Aluminum Exchange Thermometer: Application to the Melting Conditions and Mantle Lithologies of Large Igneous Provinces
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橄榄石-尖晶石铝交换温度计的扩展校准：在大型火成岩省的熔化条件和地幔岩性中的应用
DOI：
10.1093/petrology/egad077
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发表时间：
2023
影响因子：
3.9
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Zhang Y
橄榄石-尖晶石铝交换温度计在天然样品中的应用受到其校准的有限实验数据集的限制。在这里，我们提出了一个新的数据集的46个高温结晶实验和21重新分析发表的实验，我们用来扩展校准到更高和更低的温度。最终的校准数据集涵盖了与地壳和上地幔过程相关的一系列条件：1174-1606°C，0.1-1350 MPa，QFM − 2.5至QFM + 7.2（氧逸度，fO 2，以相对于石英-铁橄榄石-磁铁矿缓冲区，QFM的对数单位报告）和0-7.4重量% H2O熔体。我们提出了三种新的模式。第一种是基于尖晶石Fe、Mg、Al和Cr的组成以及橄榄石和尖晶石之间的Al交换的自洽性。第二个和第三个是经验模型，考虑较少的元素交换：第二个只使用铝交换和尖晶石组合物，而第三个认为橄榄石尖晶石铝和铬交换。所有的模型包括适度的影响的压力对橄榄石尖晶石平衡化学，whereasfO 2和水含量的影响可以忽略不计。一般来说，由于橄榄石-尖晶石交换中考虑的元素较少，因此与实验数据的拟合度较高。相反，模型复杂性的相关降低提高了其对系统误差的鲁棒性，当应用于天然晶体对：由于尖晶石亚固相线再平衡的热力学模型可能会低估天然样品中的结晶温度，而经验模型（独立于尖晶石中的Fe和Mg）对再平衡不太敏感，但产生温度具有较大的不确定性。我们应用统计检验来选择最合适的模型应用于自然样品。当应用于来自大洋中脊、冰岛、斯凯岛、峨眉山、埃滕德卡和托尔图加尔的熔岩时，我们的新温度估计比以前提出的低30-100°C。较低的温度估计导致较低的地幔熔融温度，并对地幔岩性约束产生重大影响。
The application of the olivine–spinel aluminum exchange thermometer to natural samples is limited by the restricted experimental data set on which it was calibrated. Here, we present a new data set of 46 high-temperature crystallization experiments and 21 reanalyzed published experiments, which we used to extend the calibration to higher and lower temperatures. The final calibration data set spans a range of conditions relevant to crustal and upper mantle processes: 1174–1606°C, 0.1–1350 MPa, QFM − 2.5 to QFM + 7.2 (oxygen fugacity,fO2, reported in log units relative to the quartz–fayalite–magnetite buffer, QFM), and 0–7.4 wt % H2Omelt. We propose three new models. The first is thermodynamically self-consistent, based on spinel Fe, Mg, Al, and Cr compositions and Al exchange between olivine and spinel. The second and third are empirical models that consider fewer elemental exchanges: the second uses only Al exchange and spinel compositions, whereas the third considers olivine–spinel Al and Cr exchange. All models include the modest effect of pressure on olivine-spinel equilibrium chemistry, whereasfO2and water content have negligible effects. In general, as fewer elements are considered in the olivine–spinel exchange, the fit to experimental data worsens. Conversely, the associated decrease in model complexity improves their robustness against systematic errors when applied to natural crystal pairs: the thermodynamic model may underestimate crystallization temperatures in natural samples due to spinel subsolidus re-equilibration, whereas the empirical models (independent of Fe and Mg in spinel) are less sensitive to re-equilibration but yield temperatures with larger uncertainties. We applied a statistical test to select the most appropriate model for application to natural samples. When applied to lavas from mid-ocean ridges, Iceland, Skye, Emeishan, Etendeka, and Tortugal, our new temperature estimates are 30–100°C lower than previously proposed. The lower temperature estimates cause a lower mantle melting temperature and significant impacts on the mantle lithology constraints.