Experiment and observation have established the centrality of oxygen fugacity (fO2) to determining the course of igneous differentiation, and so the development and application of oxybarometers have proliferated for more than half a century. The compositions of mineral, melt, and vapor phases determine the fO2 that rocks record, and the activity models that underpin calculation of fO2 from phase compositions have evolved with time. Likewise, analytical method development has made new sample categories available to oxybarometric interrogation. Here we compile published analytical data from lithologies that constrain fO2 (n=860 volcanic rocks - lavas and tephras and n=326 mantle lithologies- the majority peridotites) from ridges, back-arc basins, forearcs, arcs, and plumes. Because calculated fO2 varies with choice of activity model, we re-calculate fO2 for each dataset from compositional data, applying the same set of activity models and methodologies for each data type. Additionally, we compile trace element concentrations (e.g. vanadium) which serve as an additional fO2-proxy. The compiled data show that, on average, volcanic rocks and mantle rocks from the same tectonic setting yield similar fO2s, but mantle lithologies span a much larger range in fO2 than volcanics. Multiple Fe-based oxybarometric methods and vanadium partitioning vary with statistical significance as a function of tectonic setting, with fO2 ridges < back arcs < arcs. Plume lithologies are more nuanced to interpret, but indicate fO2s  ridges. We discuss the processes that may shift fO2 after melts and mantle lithologies physically separate from one another. We show that the effects of crystal fractionation and degassing on the fO2 of volcanics are smaller than the differences in fO2 between tectonic settings and that effects of subsolidus metamorphism on the fO2 values recorded by mantle lithologies remain poorly understood. Finally, we lay out challenges and opportunities for future inquiry.

Garnet-bearing volcanic rocks are extremely rare at convergent margins, with few known occurrences worldwide [ref 1-2]; however, such rocks are common within the late Miocene volcanic rock suite of the Northern Andean block (NAB) along the Central Cordillera, Colombia [ref 3-5]. They have been linked to pre-existing zones of crustal weakness that channeled magmas to the upper crust in a short period of time [ref 5-6]. Here we present new geochronological and petrographic data to constrain the timing and petrogenesis of these unusual rocks. We obtained mineral chemical analyses from 7 porphyritic-andesite samples from the eastern flank of the Central Cordillera and the Cauca-Patia Basin, Colombia. Garnet phenocrysts are almandine in composition, ranging from 23 to 29 wt.% FeO, 6 to 8 wt.% CaO, and 1 to 4 wt.% MnO. In some samples, garnets are homogeneous with no reaction rims and lacking inclusions; however, in other samples, garnets show re-absorption rims and inclusion assemblages similar to the rock matrix (plag, amph, ± bt) as well as rare plagioclase coronas. The high Ca and low Mn contents of the NAB garnet cores are consistent with crystallization at ~1.2GPa, based on phase equilibrium experiments of [ref 7], while garnet rim assemblages are congruent with a second stage of crystallization at ~0.8GPa under water-undersaturated conditions. Finally, a pre-eruption dehydration stage is evidenced by the presence of breakdown rims in amphibole crystals. Our new U-Pb in zircon ages reveal that NAB garnet-bearing volcanic rocks formed between 9 and 8 Ma. Taken together, our data suggest a rapid ascent of the NAB magmas associated with the onset of regional volcanism and extension, and possibly the development of the Caldas Tear, a slab window within the Nazca Plate. [1] Green & Ringwood (1968) CMP. [2] Harangi et al. (2001) Journal of Petrology. [3] Orrego (1975) UNAL Colombia. [4] García (1983) UNAL Colombia. [5] Bissig et al. (2017) EG. [6] Weber et al. (2018) SGC (in press). [7] Alonso-Pérez et al. (2006) CMP.

The Smithsonian – the world’s largest research, education, and museum complex – was established by the U.S. government as a public trust 175 years ago. Many of the geoscientists working for the Smithsonian’s National Museum of Natural History (NMNH) are federal employees. The federal setting offers both challenges and opportunities to actively combat structural racism, diversify our workplace, and to increase the inclusion, representation, and celebration of BIPOC in the geosciences. Our federal affiliation affords many opportunities. Smithsonian’s widely recognized brand and mission to engage diverse audiences allows our scientists to be highly visible to the public, and representation from underrepresented communities within our ranks has the potential to inspire broader participation in the geosciences. With a large and federally supported repatriation office, NMNH is in a position to lead the decolonization of geological collections and incorporate Indigenous knowledge into our collections information. NMNH fosters strong relationships with some tribal communities that provide us with excellent resources to engage Indigenous and local scientists in our research and field work. We enjoy transparency in many federal policies on hiring, promotion, salaries and benefits, and detailed equal employment opportunity (EEO) training is required for all supervisors. Federal status also presents challenges. Progress toward diversity and equity checks are tracked at the institutional level, but do not inform individual hiring decisions. There is no legal scope for targeted hires, and actions that might increase the “yield” on offers of employment, such as making an additional position for a partner, offering perks in the form of housing, child-care, higher salary, additional benefits, etc. are prohibited by federal regulation. Several future strategies emerged as priorities in our URGE pod. We will work to (1) ensure all interns receive equitable compensation and that we advertise internship availability to underrepresented communities; (2) require applicants to provide a Diversity, Equity, and Inclusion (DEI) statement for all geoscience positions; (3) implement EEO and bias training search committee members; and (4) include DEI elements in our annual performance plans.