Fig. 7. Plagioclase textures, Sr diffusion forward modeling approach, and results.

(A) BSE images show common plagioclase textures (ITO-D1-01_Plag-8, F-A2-02_Plag-4, and ITO-D1-02_Plag-12, respectively). Scale bars, 500 μm. (B and C) An example of one forward model shows changes in the Sr profile and Sr versus An from initial conditions (black line) toward equilibrium (blue dashed line). The color scale is shown in (E). (D) Example of observed Sr and An data from ITO-D1-02_Plag-12 (red box in A), colored by distance from the core-most analysis. Blue curves show the plagioclase compositions (±2σ) expected if full diffusive equilibrium were reached with a magma with 80 ppm Sr (average glass Sr) or 180 ppm Sr (average whole-rock Sr). Solid black lines are linear regressions for the core and rim, with slope (m) and correlation (r value) shown. (E) Observed slope and r values of all plagioclase core segments (N = 120). The core and rim in (D) are plotted as black squares labeled with “C” and “R,” respectively. Kernel density plots of the slopes of all core (solid lines) and rim segments (dashed lines), are plotted at the top, as well as the slopes expected if equilibrium were to be reached with a melt with 80 ppm Sr (filled squares) and 180 ppm Sr (open squares), using the three partitioning models [Nielsen et al. (47), Bindeman et al. (45), and Dohmen and Blundy, (46)]. The colored curves on the figure show the modeled progression of the Sr/An slope and r value of four forward diffusion models (color scale on the right). Black diamonds are labeled with the diffusion time (in years) needed to reach that slope and r value. Only models using the partitioning equation from Nielsen et al. (47) are shown here for clarity. See fig. S10 for comparison to all equilibrium slopes using all three partitioning models.