Experimental quantification of plagioclase crystal size distribution during cooling of a basaltic liquid

An experimental study has been conducted to constrain how thermal history controls crystal size distribution (CSD) of plagioclase in cooling basalts. Data from all experiments are dominated by a log-linear segment of decreasing number density with increasing crystal size, consistent with observations in many natural rocks. The slope of the CSD is found to be a function of cooling rate, faster cooling leading to greater slopes. At constant cooling rate the CSDs flatten as temperature decreases, and are sometimes kinked, characteristics consistent with independent textural observations that crystal agglomeration contributes significantly to crystal “growth”. A downturn is observed toward small size, which suggests Ostwald ripening. Furthermore, we find that thermal history above the liquidus has a major influence on CSDs and on the temperatures of phase appearance. We conclude that near the liquidus heterogeneous nucleation typically dominates. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Determination of Selenium Concentrations in NIST SRM 610, 612, 614 and Geological Glass Reference Materials Using the Electron Probe, LA-ICP-MS and SHRIMP II

A combination of EMPA, sensitive high resolution ion microprobe (SHRIMP II) and/or LA-ICP-MS techniques was used to measure the concentration of selenium (Se) in NIST SRM 610, 612, 614 and a range of reference materials. Our new compiled value for the concentration of Se in NIST SRM 610 is 112 ± 2 μg g⁻¹. The concentration of Se in NIST SRM 612, using NIST SRM 610 for calibration, determined using LA-ICP-MS (confirmed using SHRIMP II) was 15.2 ± 0.2 μg g⁻¹. The concentration of Se in NIST SRM 614, using LA-ICP-MS was 0.394 ± 0.012 μg g⁻¹. LA-ICP-MS determination of Se in synthetic geological glasses BCR-2G, BIR-1G, TB-1G and the MPI-DING glasses showed a range in concentrations from 0.062 to 0.168 μg g⁻¹. Selenium in the natural glass, VG2, was 0.204 ± 0.028 μg g⁻¹.