Solubility of TiO 2 in garnet and orthopyroxene: Ti thermometer for ultrahigh-temperature granulites
Solubility of TiO 2 in garnet and orthopyroxene: Ti thermometer for ultrahigh-temperature granulites
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DOI：
10.3133/ofr20071047srp038
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Toshisuke Kawasaki;Y. Motoyoshi
中科院分区：
文献类型：
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作者：
Toshisuke Kawasaki;Y. Motoyoshi
本文报道了在南极两个麻粒岩系中，在压力7-20kbar，温度850-1300°C下测量的二氧化钛在石榴石和与金红石共存的斜方辉石中的溶解度。超高温变质条件下，在石榴石的三角-十二面体位置上，未发现M-Ti(M为Mg或Fe)对Al-Al的偶合取代，以及-Ti(空位)对M-M的间隙取代的证据。石榴石中的二氧化钛含量随温度升高而升高，随压力升高而降低。在斜方辉石中，钛取代了四面体和八面体位置的原子。斜方辉石的钛含量随着温度的升高而增加，随着压力的增加而增加。钛在石榴石和斜方辉石中的溶解度对压力变化不那么敏感，与下列经验公式给出的温度关系相比：
We report the TiO2 solubility in garnet and orthopyroxene coexisting with rutile calibrated from ex- perimental data at pressures 7-20 kbar and temperatures 850-1300°C in two Antarctic granulite systems. The Ti would substitute for the tetrahedral Si, whereas we could not find positive evidence of the coupled substitution of M-Ti (M is Mg or Fe) for Al-Al in octahedral sites as well as the interstitial substitution of-Ti ( is a vacancy) for M-M in triangular-dodecahedral sites of garnet at ultrahigh-temperature (UHT) metamorphic conditions. The TiO2 content of garnet increases with temperature and decreases with pressure. In orthopyroxene Ti substitutes for atoms in the tetrahedral and octahedral sites. The Ti content of orthopyroxene increases with temperature and increases with pressure. Titanium solubility in garnet and orthopyroxene is not so sensitive to pressure change as compared with temperature dependence given by following empirical equations: