A new model for zircon saturation in silicate melts

Abstract

A new model describing zircon saturation in silicate melts is presented that combines the results of 196 data from new experiments with data from previous experimental studies. In the new experiments, the concentration of Zr in melts coexisting with zircon was determined at temperatures between 800 and 1500 °C for 21 compositions (with alumina saturation index, ASI, from 0.20 to 1.15), containing ~ 1 to 16 wt % FeOT and, for a subset of these conditions, at variable pressure (0.0001 to 4.0 GPa) and water content (0 to 15 wt %). The collated dataset contains 626 data, with 430 from 26 literature studies, and covers conditions from 750 to 1620 °C, (including 45 new data and 106 literature data for temperatures < 1000 °C), ASI 0.20 to 2.00, 0.0001 to 4.0 GPa and 0 to 17 wt % H2O. A limitation of previous models of zircon saturation is the choice of parameter used to describe the silicate melt, which may not be appropriate for all compositions and can result in differences in predicted temperatures of over 200 °C for granitic systems. Here we use optical basicity (Λ), which can be easily calculated from the major oxide components of a melt, to parameterise the composition. Using a non-linear least-squares multiple regression, the new zircon saturation model is:$$\log{\mathrm{Zr}} = 0.96(5) - 5790(95)/T - 1.28(8)P + 12.39(35){\varLambda} + 0.83(9)x.\text{H}{_2}\text{O} + 2.06(16)P{\varLambda} $$ log Zr = 0.96 ( 5 ) - 5790 ( 95 ) / T - 1.28 ( 8 ) P + 12.39 ( 35 ) Λ + 0.83 ( 9 ) x . H 2 O + 2.06 ( 16 ) P Λ where Zr is in ppm, T is temperature in K, P is pressure in GPa, Λ is the optical basicity of the melt, x.H2O is the mole fraction of water in the melt, and the errors are 1σ. This model confirms that temperature and melt composition are the dominant controls on zircon solubility. In addition, pressure and melt water content exert small but resolvable effects on the solubility and are included, for the first time, in a model. Using this new calibration, 92% of the predicted temperatures are within 10% of the experimental temperatures for the collated dataset (with an average temperature difference of 57 °C), while predicted temperatures for only 78 and 62% of the collated dataset are within 10% of the experimental temperature (with average temperature differences > 80 °C) using the widely cited Watson and Harrison (Earth Planet Sci Lett 64:295–304, 1983) and Boehnke et al. (Chem Geol 351:324–334, 2013) models, respectively. This new model can be extrapolated to temperatures below those included in the calibration with greater accuracy and when applied to melt inclusions from the Bishop Tuff, gives temperatures that are in excellent agreement with independent estimates.

The role of continental subduction in mantle metasomatism and carbon recycling revealed by melt inclusions in UHP eclogites

“…The successful rehomogenization of the inclusions, the compositional match between the preserved glassy inclusions and the rehomogenized ones, and the general agreement on the peak T of the unit suggest that 1000°C rather than 725°C is more likely to represent the minimum T of entrapment. Moreover, using a different solubility model [i.e., Zr calibrated for high pressures; (35)], we obtain temperatures of 1040°C that overall support our hypothesis for melt entrapment at minimum 1000°C, indicating that the discrepancy observed for LREE-solubility thermometry may result from complexities in the accessory mineral saturation processes upon the production and evolution of the Saidenbach melts. The H 2 O content of the inclusions ranges between 3.14 and 5.23 wt % (Fig.…”

Structural changes in silicate melt: A record from high-field strength elements in the Himalayan Cenozoic leucogranites

“…There is a similar relationship between geochemical parameters and Nb/Ta ratio (Figures 4, 5). Based on the Zr and LREE concentrations, granites with Zr/Hf and Nb/Ta ratio greater than 20 and 5, respectively, they yield lower temperatures inferred by zircon saturation thermometry (T Zr , Watson and Harrison, 1983;Crisp and Berry, 2022) than those as by monazite saturation thermometry (T LREE , Montel, 1993). However, they yield similar temperatures in the granites with Zr/Hf ratio less than 20 and Nb/Ta ratio less than 5, respectively (Figure 6).…”

AgeSpectraAnalyst: A MATLAB based package to model zircon age distributions in silicic magmatic systems

“…This method focuses on calc-alkaline, evolved magma compositions (e.g. granites, rhyolites) as they source most catastrophic, caldera-forming eruptions [ 17 ] and their near-ubiquitous zircon saturation [ [18] , [19] , [20] ] makes them preferential targets of high-precision zircon geochronology studies (e.g. [ [21] , [22] , [23] , [24] ]).…”

“…Trivial differences in crystallized zircon mass distributions are observed when tying dependence of zircon saturation on melt temperature and composition ( Eq. (2 )) with the most recent Crisp and Berry [ 20 ] experimental calibration.…”