Curie temperatures of synthetic titanomagnetites in the Fe‐Ti‐O system: Effects of composition, crystal chemistry, and thermomagnetic methods
Curie temperatures of synthetic titanomagnetites in the Fe‐Ti‐O system: Effects of composition, crystal chemistry, and thermomagnetic methods
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DOI：
10.1029/2006jb004591
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发表时间：
2006-12
影响因子：
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通讯作者：
D. Lattard;R. Engelmann;A. Kontny;U. Sauerzapf
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文献类型：
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作者：
D. Lattard;R. Engelmann;A. Kontny;U. Sauerzapf
(1)本研究的目的是改进的居里温度（TC）的钛磁铁矿（Tmt）的组成依赖性的基础上，在Fe-Ti-O系统中的合成Tmt的测量的温度相关的磁化率（c-T）曲线的校准。为了评估高温阳离子空位对TC值的可能影响，我们合成了两种类型的组合在subsolidus条件下，在1巴，1100 ℃和1300 ℃，在受控的氧逸度条件下。与钛铁矿-赤铁矿（Ilmss）平衡合成的TMTS预计具有最高的空位浓度，与浮氏体（Wus）平衡的TMTS具有最低的空位浓度。用扫描电子显微镜（SEM）和电子探针（EMP）仔细检查合成Tmts的组成和均匀性。使用kappabridge从c-T曲线确定TC，为了比较，从使用可变场平移天平测量的Ms-T曲线确定TC。我们的数据集显示，系统更高的TC值TMT与Ilmss共存比TMT与Wus共存。大多数c-T曲线是不可逆的，其中最大的DTC（40 K）涉及在1300 C下合成的中间组合物的Tmt（+Ilmss）。不可逆性被解释为反映阳离子重排TMT在高温c-T测量。从Ms-T曲线获得的TC值高于从c-T曲线获得的TC值，其中差异随着Ti含量的增加而规律性地增加（高达40 K），高达XUsp = 0.6。我们的新的校准曲线是合适的检索TMT组合物的玄武岩，迅速冷却，而不是氧化的氘或热液流体。引文：Lattard，D.，R. Engelmann，A. Kontny和U. Sauerzapf（2006），Fe-Ti-O系统中合成钛磁铁矿的居里温度：成分、晶体化学和热磁方法的影响，J. Geophys.结果：111，B12S28，
(1) The present study is aimed at improving the calibration of the compositional dependence of the Curie temperature (TC) of titanomagnetite (Tmt) on the basis of temperature-dependent magnetic susceptibility (c-T) curves measured on synthetic Tmts in the Fe-Ti-O system. In order to assess the possible influence of high-temperature cation vacancies onto the TC values, we have synthesized two types of assemblages in subsolidus conditions at 1 bar, 1100C and 1300C, under controlled oxygen fugacity conditions. Tmts synthesized in equilibrium with ilmenite-hematitess (Ilmss) are expected to have the highest vacancy concentrations, those in equilibrium with wustite (Wus) the lowest. The composition and homogeneity of the synthetic Tmts were carefully checked with a scanning electron microscope (SEM) and an electron microprobe (EMP). TC was determined from c-T curves using a kappabridge and, for comparison, from Ms-T curves measured with a variable field translation balance. Our data set shows systematically higher TC values for Tmt coexisting with Ilmss than for Tmt coexisting with Wus. Most c-T curves are nonreversible, whereby the largest DTC (40 K) concern Tmt(+Ilmss )o f intermediate compositions synthesized at 1300C. Nonreversibility is interpreted as reflecting cation reordering in Tmt during the high-temperature c-T measurements. TC values obtained from Ms-T curves are higher than those obtained from the c-T curves, whereby the difference regularly increases (up to 40 K) with increasing Ti content, up to XUsp = 0.6. Our new calibration curves are suitable to retrieve Tmt compositions in basalts that were rapidly cooled and not oxidized by deuteric or hydrothermal fluids. Citation: Lattard, D., R. Engelmann, A. Kontny, and U. Sauerzapf (2006), Curie temperatures of synthetic titanomagnetites in the Fe-Ti-O system: Effects of composition, crystal chemistry, and thermomagnetic methods, J. Geophys. Res., 111, B12S28,