OLIVINE LIQUID EQUILIBRIA - TEMPERATURE, PRESSURE AND COMPOSITION DEPENDENCE OF THE CRYSTAL LIQUID CATION PARTITION-COEFFICIENTS FOR MG, FE-2+, CA AND MN
OLIVINE LIQUID EQUILIBRIA - TEMPERATURE, PRESSURE AND COMPOSITION DEPENDENCE OF THE CRYSTAL LIQUID CATION PARTITION-COEFFICIENTS FOR MG, FE-2+, CA AND MN
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DOI：
10.1093/petrology/24.3.256
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发表时间：
1983-01-01
影响因子：
3.9
通讯作者：
FISK, MR
中科院分区：
文献类型：
--
作者：
FORD, CE;RUSSELL, DG;FISK, MR
本文根据747个干基性和超基性岩浆实验结果及有关合成体系，导出了橄榄石/液体阳离子分配系数与温度、压力和液体组成的关系式，其相关系数分别为：Mg（r = 0.996）、Fe ~（2+）（r= 0.993）、Ca（r= 0.79）和Mn（r= 0.70）。Mg和Fe 2+的分配系数之比（KD）在0.25到0.38之间变化。对于任何给定的岩浆成分，液相线橄榄石在高压下比在低压下略富铁，Mg和Fe ~（2+）分配系数方程可用作地质温度计，如果压力可通过独立方法估算，其精确度优于± 1%。微量元素分配温度计（Ca和Mn）对分析误差或偏离平衡太敏感，无法证明其可靠性。温度也可以从基于橄榄石饱和度概念的地质温度计获得。这与橄榄石成分无关，并且可以用于橄榄石和宿主液体之间不平衡的证据。在这种情况下，由Mg和Fe 2+分配温度计指示的误差关于真实温度是不对称的，除了当平衡橄榄石组合物是Fo 50时。这些地质温度计具有足够的灵敏度来显示岩浆的混合作用，尽管分配系数和分配系数之比（KD）很小，但分配系数方程可以用来模拟橄榄石的平衡结晶。都在不断变化橄榄石的分步结晶可以通过连续去除少量平衡结晶形成的橄榄石来近似。
From the results of 747 experiments on dry basic and ultrabasic magmas and related synthetic systems equations have been derived which predict the olivine/liquid cation partition coefficients for Mg (correlation coefficientr= 0·996), Fe2+(r= 0·993), Ca (r= 0·79) and Mn (r= 0·70) as a function of temperature, pressure and liquid composition. The ratio of the partition coefficients for Mg and Fe2+(KD) varies from 0·25 to 0·38. For any given magma composition liquidus olivines are slightly more iron-rich at high pressures than they would be at low pressures.The Mg and Fe2+ partition coefficient equations may be used as geothermometers which are accurate to better than ±1 per cent if pressures can be estimated by independent methods. Minor element partition thermometers (Ca and Mn) are too sensitive to analytical errors, or to departures from equilibrium, to prove reliable. Temperatures may also be obtained from a geothermometer based on the concept of olivine saturation. This is independent of olivine composition and can be used where these is evidence of disequilibrium between olivine and host liquid. In such a situation the errors indicated by the Mg and Fe2+partition thermometers are asymmetric about the true temperature except when the equilibrium olivine composition is Fo50. These geothermometers are sufficiently sensitive to demonstrate magma mixing.The partition coefficient equations may be used to model equilibrium crystallization of olivine even though the partition coefficients, and the ratio of the partition coefficients (KD). are continuously changing. Fractional crystallization of olivine may be approximated by sequential removal of small amounts of olivine formed by equilibrium crystallization.