The titanium-in-quartz (TitaniQ) thermobarometer: A critical examination and re-calibration
The titanium-in-quartz (TitaniQ) thermobarometer: A critical examination and re-calibration
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DOI：
10.1016/j.gca.2012.01.009
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发表时间：
2012-05-01
影响因子：
5
通讯作者：
Audetat, Andreas
中科院分区：
文献类型：
--
作者：
Huang, Ruifang;Audetat, Andreas
合成石英是在600 - 800 ℃和1 - 10 kbar的含金红石的H2O（+/-NaCl）流体中通过石英在小的热梯度中溶解和再沉淀而生长的。在几个实验中，通过在旧石英基底和新石英过度生长之间的接触处形成金红石晶体来证明快速达到金红石饱和。新石英中的钛浓度与Li和Al的浓度呈正相关，并且强烈依赖于石英的生长速率，随着生长速率从类似于4到类似于110 μ m/天的变化，增加高达2.5倍。考虑到最缓慢生长的石英样品的组成作为最具代表性的，我们获得的Ti浓度比TitaniQ温压计早期校准期间获得的Ti浓度低约三倍。我们的数据可以用方程log Ti（ppm）=-0.27943拟合。10（4）/T-660.53。（P-0.35/T）+5.6459其中T以开尔文为单位，P以千巴为单位。通过分析在已知压力（0.8 - 2.7千巴）和温度（675 - 780摄氏度）下结晶的五个侵入岩浆系统和三个火山岩浆系统的火成石英，进行了一项独立测试。TiO2的活性受到限制，从组合物的熔融包裹体托管在分析的石英。虽然结果取决于选择计算aTiO（2）的模型，但它们与我们的校准比以前的TitaniQ校准更吻合。根据我们的校准计算的结晶压力与独立的压力估计值在0.1 - 1.0 kbar范围内一致，而根据以前的校准计算的结晶压力始终高出3 - 9 kbar。我们的校准和自然数据之间的轻微偏差是由于在计算的天然熔体的aTiO（2）的不确定性，或由于未能合成结构完美的石英，即使在我们最慢的增长速度。我们的研究结果意味着TitaniQ不应该应用于从热液流体中生长的石英，因为在这些环境中的生长速率可能非常可变。TitaniQ更有可能在火成石英中起作用，尽管目前石英和硅酸盐熔体中TiO 2溶解度的模型可能仍需要改进。(c)2012爱思唯尔有限公司保留所有权利。
Synthetic quartz was grown in rutile-bearing H2O (+/- NaCl) fluids at 600-800 degrees C and 1-10 kbar by dissolution and reprecipitation of quartz in a small thermal gradient. Rapid attainment of rutile saturation is proved by the formation of rutile crystals at the contact between old quartz substrate and new quartz overgrowth in several experiments. Titanium concentrations in new quartz correlate positively with the concentrations of Li and Al and depend strongly on quartz growth rate, increasing by up to a factor of 2.5 as the growth rate varied from similar to 4 to similar to 110 mu m/day. Considering the composition of the most slowly grown quartz samples as most representative we obtain Ti concentrations that are about three times lower than those obtained during earlier calibrations of the TitaniQ thermobarometer. Our data can be fitted by the equationlog Ti(ppm) = -0.27943 . 10(4)/T - 660.53 . (P-0.35/T) + 5.6459where T is given in Kelvin and P in kbar.An independent test was made by analyzing igneous quartz from five intrusive and three volcanic magma systems that crystallized at known pressures (0.8-2.7 kbar) and temperatures (675-780 degrees C). The activity of TiO2 was constrained from the composition of melt inclusions hosted in the analyzed quartz. Although the results depend on the model chosen to calculate aTiO(2), they agree much better with our calibration than with previous TitaniQ calibrations. Crystallization pressures calculated based on our calibration agree within 0.1-1.0 kbar with independent pressure estimates, whereas those calculated based on previous calibrations are consistently higher by 3-9 kbar. Slight deviations between our calibration and the natural data are either due to uncertainties in the calculation of aTiO(2) of the natural melts or due to failure to synthesize structurally perfect quartz even at our slowest growth rates. Our findings imply that TitaniQ should not be applied to quartz grown from hydrothermal fluids, because growth rates in these environments can be very variable. TitaniQ is more likely to work in igneous quartz, although the present models for TiO2 solubility in quartz and silicate melts may still need to be refined. (c) 2012 Elsevier Ltd. All rights reserved.