Thomas Grocolas

🚨The most important graph in the world has another year of data, and it doesn't look good!🚨

NASA CERES satellites measure how much sunlight Earth absorbs and how much heat is radiated back to space.

The difference is heat accumulation, which has more than tripled!

New paper from my PhD!
Apatite in plutonic rocks records volatile budgets, crystallisation pressures, and degassing fluxes, with the fluxes compared directly to those of active volcanoes - doi.org/10.1016/j.gc...

Using the most recent diffusion coefficients yields cooling rates consistent with those from Ar-Ar dating and thermal modelling within uncertainty, while crystal residence times (40-110 kyr) agree with high-precision zircon age constraints!

Taking advantage of the government shutdown to finally advertise our paper! We constrained cooling rates and crystal residence times in the Adamello batholith combining Ti-in-quartz and Sr- and Ba-in-plagioclase diffusion - doi.org/10.1007/s004...

The role of oxygen fugacity in hydrous basaltic phase equilibria: experimental constraints at 0.2 and 0.8 GPa - Contributions to Mineralogy and Petrology Crystallisation-differentiation drives arc magma evolution, yet discrepancies remain among field, geochemical and experimental evidence. Whereas other controls are better studied, the effect of fO2, beyond oxide stability, remains less constrained. We investigate fO2-pressure effects on olivine-clinopyroxene-spinel phase relations with implications for arc magmas. We conducted phase equilibria experiments at 200 MPa between 1010 and 1100 °C. We used basaltic compositions with different xMg* [MgO/(MgO + FeOtot)] (0.5 to 0.7) at multiple fO2 conditions (NNO-0.5 to NNO + 2.3), deconvolving the effects of Fe3+/Fe2+ and xMgeff [MgO/(MgO + FeO)] on phase equilibria. Additionally, we ran 800 MPa experiments between NNO-0.4 and NNO + 2.5 to explore the combined effects of fO2 and pressure. At 200 MPa, increasing fO2 (1) stabilises Fe3+-rich spinel, leading to SiO2-richer melts and, therefore, less pronounced ASI (alumina saturation index, ASI = Al2O3/(CaO + Na2O + K2O) molar) increase relative to SiO2, and (2) expands olivine stability relative to clinopyroxene in ol-cpx cotectic melts, resulting in lower ASI melts (for a given SiO2 content) that better match arc rocks. This is only observed under spinel-absent conditions. The 800 MPa experiments reveal decreasing spinel stability with increasing pressure, while fO2 has a negligible effect on the ol-cpx cotectic. This suggests that the previously documented pressure effect on the olivine-clinopyroxene equilibrium is stronger than the effect of fO2. Our results demonstrate that fO2 increasingly influences the olivine-clinopyroxene cotectic equilibrium as pressure decreases. This supports models where decompression-driven polybaric crystallisation under oxidising conditions shapes arc magmatic compositions. The reported pressure-fO2 interplay helps reconcile natural and experimental arc records.

Great to see my new paper finally out! 🌋
We looked into the effects of pressure and fO2 on arc basalt differentiation - it's not just oxide stability!

New paper! The last of Eloïse Bretagne's PhD papers is out! Here we generalize our models for permeability to magma mush at any melt fraction. Take a look if you want to model percolative flow of melt through a magma mush and if you want to account for crystal shape.
OA: dx.doi.org/10.1029/2025...

Check out our new study on the earliest eruptive interval at Clear Lake volcanic field, California.

doi.org/10.1093/petr...

The @durhamearthsci.bsky.social connection is strong with this one ... really interesting looking review.

Plots showing the sulfur isotope compositions of metalavas and granitoid gneisses of the Innuksuaq Complex

⚒️ Article: Combined sulfur and neodymium isotopes suggest volatile cycling at subduction zones began at or prior to 3.8 Ga

@crpg-nancy.bsky.social

www.nature.com/articles/s41...

New here! Just using my first post to promote (again) my last paper, where we find that Sr diffusivity in plagioclase is slower than previously thought and similar to that of Ba. Applying our new diffusivities reveals long, consistent timescales for both elements!

doi.org/10.1016/j.ep...