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Laurence Yeung wins 2016 F. W. Clarke award from the Geochemical Society

Yeung headshotClarke medal

Laurence Yeung, assistant professor of Earth Science, will be awarded the F. W. Clarke medal from the Geochemical Society at this year’s V. M. Goldschmidt meeting in Yokohama, Japan. The award is named after Frank Wigglesworth Clarke, who determined the composition of the Earth’s crust and is considered by many to be the father of Geochemistry. From the Geochemical society’s announcement:

The Clarke Award recognizes an early-career scientist for a single outstanding contribution to geochemistry or cosmochemistry published either as a single paper or a series of papers on a single topic. Prof. Yeung is recognized for developing, both experimentally and theoretically, a new clumped isotopologue system with applications to natural systems.

With Dr. Yeung’s award, the Department of Earth Science now has three F. W. Clarke medalists: Profs. Cin-Ty Lee (2009), Rajdeep Dasgupta (2011), and Laurence Yeung (2016). We are tied (with Caltech) for the most Clarke medalists in any department in the world. Here’s to many more!

Link to story on Rice News

Hydrous basalt–limestone interaction at crustal conditions: Implications for generation of ultracalcic melts and outflux of CO2 at volcanic arcs

New student paper out!  See Laura Carter’s paper on basalt-limestone interactions with implications for arc CO2 fluxes, published in Earth and Planetary Science Letters. [article]

Abstract

High degassing rates for some volcanoes, typically in continental arcs, (e.g., Colli Albani Volcanic District, Etna, Vesuvius, Italy; Merapi, Indonesia; Popocatepetl, Mexico) are thought to be influenced by magma–carbonate interaction in the crust. In order to constrain the nature of reaction and extent of carbonate breakdown, we simulated basalt–limestone wall-rock interactions at 0.5–1.0 GPa, 1100–1200 °C using a piston cylinder and equal mass fractions of calcite (CaCO3) and a hydrous (∼4 wt.% H2O) basalt in a layered geometry contained in AuPd capsules. All experiments produce melt + fluid + calcite ± clinopyroxene ± plagioclase ± calcic-scapolite ± spinel. With increasing T, plagioclase is progressively replaced by scapolite, clinopyroxene becomes CaTs-rich, and fluid proportion, as inferred from vesicle population, increases. At 1.0 GPa, 1200 °C our hydrous basalt is superliquidus, whereas in the presence of calcite, the experiment produces calcite + clinopyroxene + scapolite + melt. With the consumption of calcite with increasing T and decreasing P, melt, on a volatile-free basis, becomes silica-poor (58.1 wt.% at 1.0 GPa, 1100 °C to 34.9 wt.% at 0.5 GPa, 1200 °C) and CaO-rich (6.7 wt.% at 1.0 GPa, 1100 °C to 43.7 wt.% at 0.5 GPa, 1200 °C), whereas Al2O3 drops (e.g., 19.7 at 1100 °C to 12.8 wt.% at 1200 °C at 1.0 GPa) as clinopyroxene becomes more CaTs-rich. High T or low P melt compositions are ‘ultracalcic,’ potentially presenting a new hypothesis for the origin of ultracalcic melt inclusions in arc lava olivines. Wall-rock calcite consumption is observed to increase with increasing T and decreasing P. At 0.5 GPa, our experiments yield carbonate assimilation from 21.6 to 47.6% between 1100 and 1200 °C. Using measured CO2 outflux rates for Mts. Vesuvius, Merapi, Etna and Popocatepetl over a T variation of 1100 to 1200 °C at 0.5 GPa, we calculate 6–92% of magmatic input estimates undergo this extent of assimilation, suggesting that up to ∼3% of the current global arc CO2 flux may be crustally derived. Application of the assimilation extent bracketed in this study to the estimated elevated number of carbonate-assimilating arc magmatic systems active during the late Cretaceous to early Paleogene suggests that magma-induced upper plate decarbonation alone had the potential to contribute up to 2.7×1014–5.6×1015 g/y CO2, assuming no dilution and complete gaseous release of all assimilated carbon. Using an estimated assimilation extent averaged from current systems gives a slightly lower though still significant value of ≤5.5×1014 g/y of excess CO2 being released into the atmosphere.