Please consider pre-registering for the following event!:
Understanding oxygen fugacity in Geoscience is a workshop/school running 5-9 September 2022, to highlight the state of the art, major debates and some case studies about redox processes and oxygen fugacity from the Earth’s interior to the surface. It will bring together experts from various disciplines and it is directed to students and scientists with background on chemistry and physics of the Earth and planetary interiors. The School is hosted by the Department of Mathematics and Geosciences, University of Trieste. We also hope to make the School available to online-only participants.
Eleanor Green and Katy Evans are among the speakers and practical leaders at this School, which will address thermodynamic modelling in addition to experimental, analytical and observational themes.
We thank Luca Ziberna for proposing this School, for patiently persisting with the idea throughout the disruption of the pandemic, and for his exceedingly hard work in leading the Organizing Committee!
Simon’s short postdoc has (unfortunately) come to an end.
Time it was, and what a time! I had an amazing experience in this beautiful city – even though I spent more time at home than I would have hoped for.
I am extremely grateful for this dive into the wonderland of model development. Eleanor & Roger showed me a glimpse of how deep the rabbit hole goes – the bottom is not yet in sight! I am honored to be a part of this team and to have learned from these great people. Eleanor and myself will keep close contact and to work on cpxwing and many more exciting projects down the road.
Melbourne, I will miss your chatty lorikeets and amazing coffee. A year really is too short to get to know you.
A quick round-up of news on team members and projects related to the HPx-eos and THERMOCALC:
Simon Schorn recently moved to Austria, where he has been awarded a grant to work at the University of Graz on fluid infiltration during metamorphism. Congratulations Simon! He had a strange year as Eleanor’s post-doc in Melbourne, spending two thirds of it in actual or effective lockdown, but we look forward to continued collaboration and a belated farewell dinner once international travel resumes. While in Melbourne, Simon did excellent work on cpx- and amphibole-bearing equilibria in subsolidus metabasite systems, making key insights that will help us with modelling the blueschist facies. His monstrous new cpx x-eos, cpx-wing, just needs its laser cannons added before it’s ready for take-off.
Corinne Frigo has just completed a marathon experimental programme at ANU, which has highlighted where we could improve the igneous x-eos in dry peridotite systems. We appreciate Corinne’s results all the more because she has persevered with her work through bushfires, a devastating hailstorm that put her lab out of action, and the pandemic. Well done Corinne!
John Mansour has done some magnificent work on TawnyCALC – and the delay in completing and releasing it is entirely my fault, sorry John! More news on this soon.
Katy Evans rightly pointed out that the set of hydrated ultramafic x-eos used in Evans & Powell (2015; J Metam Geol 33 649-670) should be on this site. She has been preparing the input files for this, and they should be ready to go shortly.
RP is focusing on updates to THERMOCALC 3.50. He has implemented a number of changes to the scripting, aimed at making it simpler, more transparent, and better at helping the user when things go wrong. He is currently restoring some functionality related to calculations with fluids that has been lost in recent versions. Once a new version of the program is ready for release, we will also be able to make Simon’s long-awaited pseudosection tutorial available, with up-to-date scripts.
Tim Holland continues to develop the dataset and igneous-set x-eos. In particular: an update for peridotite melting relations; updates for Ti in various phases (ru, ilm, melt); updating spinels with Eleanor; adding CO2 and S to melts, the last two in quite early but promising stages; working with RP on a simple ternary feldspar model that is continuous in composition (without the distinct C1/I1 phases); and on a nepheline model with Owen Weller.
Finally, in between battles with high-Ca opx and cpx-wing, Eleanor Green has been investigating some xenolith data from the Lesser Antilles volcanic arc, collected by Jon Blundy’s team at the University of Bristol. The xenoliths sample the upper part of the magmatic system that created each island, and their whole-rock chemistry and mineral assemblages contain insights into how this magmatic system varies along of the arc. These rocks are very high variance – they have many dimensions of significant compositional variability, but few phases – so forward modelling has proved too challenging for the current generation of x-eos. Fortunately, this is where the (S)COlP barometers come in useful.
Dear friends, colleagues, and all HPx-eos/THERMOCALC users,
There will be a hiatus in news, as, in common with the rest of the global community, we work to handle the effects of the COVID-19 pandemic on our professional and personal lives. I hope to return to website developments in June, after the end of semester.
Wishing all of you the very best at this difficult time,
Corinne Frigo has been visiting Melbourne from ANU. Corinne is working with Hugh O’Neill, Richard Arculus and Eleanor on ARC Discovery Project DP170100982, A new perspective on melting in the Earth and the origin of basalts. She has some very interesting experimental results on peridotite melting in CMAS + Cr2O3 + K2O at 30 kbar, which contrast nicely with the experiments of Liu & O’Neill (2004) at 11 kbar.
The experiments are giving the x-eos a workout! Currently, the model pyroxenes are taking too much Al2O3 in high-Cr2O3 bulk compositions, meaning that we should revise the Al-Cr partitioning here. Experiments in small systems are extremely useful, providing constraints that can’t be extracted from the natural system data available. Eleanor and Corinne will continue to look at this problem over the next few months, and their new insights will ultimately be incorporated into the next generation of igneous x-eos.
New to phase diagram modelling? Always wanted to know how petrogenetic grids were made but didn’t dare to ask? Worry no more! Here’s the first of a series of tutorials, a simple, step-by-step guide to build your own P-T projection with THERMOCALC!
Looking ahead, Eleanor and John have just been discussing TawnyCALC, one of two upcoming extension packs to THERMOCALC.
TawnyCALC will automate various problems that involve driving THERMOCALC along a path, doing dogmin calculations at each step. Fractionation calculations are an obvious example. We currently plan to have it running online via a Jupyter interface.
The second extension pack, TammaCALC, will allow a set of phase diagram calculations to be made simultaneously and repeatedly. It will facilitate various uncertainty calculations.
This is Simon’s blog reporting on the development of a new single-clinopyroxene HPx-EOS.
The new model is designed to replace pre-existing versions that do not currently overlap in P—T—x space.
So far three clinopyroxene EOS exist. Ordered diopside—omphacite—jadeite (Green et al., 2007) is for coexisting sodic—calcic clinopyroxenes. It accounts for order—disorder on the octahedral M1 and M2 sites, but not on the tetrahedral T sites. It is appropriate for high pressure but unsuitable for high temperatures.