A simple model for the viscosity of rhyolites as a function of temperature, pressure and water content
A simple model for the viscosity of rhyolites as a function of temperature, pressure and water content
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流纹岩粘度随温度、压力和含水量变化的简单模型
DOI：
10.1016/j.gca.2015.08.009
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发表时间：
2014
影响因子：
5
通讯作者：
A. Whittington
中科院分区：
文献类型：
--
作者：
W. Romine;A. Whittington
为了更好地限制低至中等含水量 (X) 下高硅流纹岩的粘度 (η)（代表近地表压力-温度 (P-T) 条件下的水饱和度），我们在大气压下使用平行板和同心圆柱体方法，在 796 至 1774 K 之间的温度下，对含有 0.01 至 1.2 wt.% H 2 O 的 Mono Craters 流纹岩进行了 211 次粘度测量。然后，我们开发并校准了流纹岩熔体粘度的新经验模型，其中温度 (T) 和含水量 (X) 引起的非线性变化嵌套在 log η 对压力 (P) 的线性和指数依赖性中。该模型总共拟合了 691 个数据点，包括已发表的流纹岩、花岗岩和单面花岗岩数据。模型参数的显着性在 95% 的置信水平下进行评估。该模型足够简单，可用于管道或熔岩流动力学的数值模型： log η=-4.40+ 11609-1248 ln (w+ 0.17) T-(140.1-62.3 ln (w+ 0.17))-P 0.00082+ 0.000051 w-0.95 T 其中 η 是粘度，单位为 Pa s，w 是水含量wt.%，P 是以 MPa 为单位的压力，T 是以 K 为单位的温度。模型与校准中使用的 691 个数据点之间的均方根误差 (RMSE) 为 0.43 个对数单位，残差分析表明该模型以相似的质量程度拟合 P–T–X (H 2 O) 空间的所有建模区域。在这两方面，新模型的流纹岩粘度均优于以前的模型。多级建模使我们能够证明较高的温度和较高的含水量都独立地有利于粘度对负压的依赖性更大。该模型表明，当无水流纹岩的温度升至 1175 K 以上，以及含有 5 wt.% H 2 O 的熔体温度升至 865 K 以上时，压力对粘度的影响会经历从正面影响到负面影响的转变。我们通过检查少数已发表的粘度数据来验证该模型，其中 P 发生变化，但 T 和 X (H 2 O) 保持大致恒定。实验限制导致粘度数据集中 P、T、X (H 2 O) 和 η 之间存在虚假相关性，因此模型可能难以正确解析 P、T 和 X (H 2 O) 的单独影响，尤其是它们的互相关性。
In order to better constrain the viscosity (η) of high-silica rhyolite at low to moderate water contents (X), which represent water saturation at near-surface pressure–temperature (P–T) conditions, we made 211 viscosity measurements on Mono Craters rhyolites containing between 0.01 and 1.2 wt.% H 2 O, at temperatures between 796 and 1774 K using parallel plate and concentric cylinder methods at atmospheric pressure. We then developed and calibrated a new empirical model for the rhyolitic melt viscosity, where non-linear variations due to temperature (T), and water content (X) are nested within linear and exponential dependencies of log η on pressure (P). The model was fitted to a total of 691 data points including published data on rhyolites, granites and haplogranites. The significance of model parameters was evaluated at the 95% confidence level. The model is simple enough for use in numerical models of conduit or lava flow dynamics: log η=-4.40+ 11609-1248 ln (w+ 0.17) T-(140.1-62.3 ln (w+ 0.17))-P 0.00082+ 0.000051 w-0.95 T where η is viscosity in Pa s, w is water content in wt.%, P is pressure in MPa and T is temperature in K. The root mean square error (RMSE) between the model and the 691 data points used in calibration is 0.43 log units, and analysis of the residuals shows that the model fits all modeled regions of P–T–X (H 2 O) space to a similar degree of quality. In both regards, the new model outperforms previous models for rhyolite viscosity. Multi-level modeling enabled us to show that higher temperatures and higher water contents both independently favor a more negative pressure-dependence of viscosity. The model suggests that the effect of pressure on viscosity undergoes a transition from a positive to a negative effect as temperatures rise above∼ 1175 K for anhydrous rhyolites, and above∼ 865 K for melts containing 5 wt.% H 2 O. We validated the model by examination of the few published viscosity data where P is varied but T and X (H 2 O) remain approximately constant. Experimental constraints have led to spurious correlations between P, T, X (H 2 O) and η in viscosity datasets, so that models may struggle to correctly resolve the individual effects of P, T and X (H 2 O), and especially their cross-correlations.
影响因子：
5.8
作者：
Cordonnier, B.;Caricchi, L.;Burlini, L.
通讯作者：
Burlini, L.