Research
Tectonic History of the Nashoba Terrane in Central MA
The metamorphic bedrock exposed in the Nashoba terrane of East-Central Massachusetts records a complex history of deformation and metamorphism associated with the subduction of the Iapetus Ocean and collision of Avalonia with the composite Laurentian margin during the Acadian orogeny. Although the structural history of the terrane has been well studied, its pressure-temperature (P-T) history is less constrained. Accurately determining P–T histories provides key constraints on orogenic processes, such as the depth of rock burial, the evolution of the geothermal gradient, and rates of exhumation. In our lab, we apply a range of field, lab, and modeling based petrologic techniques to try and unravel this missing bit of New England tectonic history!
The image on the right is a photo of Emlynn Merrill ‘25 (L) and Katherine Morin ‘24 (R) investigating an outcrop of folded migmatite in the Nashoba Terrane. They conducted preliminary petrographic analysis and phase equilibria modeling as part of their summer reseach projects. Photo credit to Jannitta Yao ‘21.
Related Publications and Abstracts
Yao, J. T., Castro, A. E., Roberts, N. M., Wolfe, O. M., Brunet, I. M., & Vasey, D. A. (2023). Phase Equilibria Evidence for Intermediate P/T Metamorphism in the Nashoba Terrane and Implications for Acadian Tectonics in Ganderia. Lithosphere, 2023(1).
Jannitta T. Yao, Adrian E. Castro, Nicolas M. Roberts, Oliver M. Wolfe, Isabella M. Brunet, Dylan A. Vasey; Phase Equilibria Evidence for Intermediate P/T Metamorphism in the Nashoba Terrane and Implications for Acadian Tectonics in Ganderia. Lithosphere 2023;; 2023 (1): lithosphere_2023_105. doi: https://doi.org/10.2113/2023/lithosphere_2023_105
*Yao, J., *Brunet, I., Castro, A.E., Wolfe, O.M., Kuiper, Y., Hepburn, & C.J., 2022 , Synthesizing petrographic analysis and modern thermodynamic modeling to determine the P–T conditions of metamorphism in the Nashoba Terrane, East-Central MA, Geological Society of America, Abstracts with Programs., Vol 54, No. 3, https://doi.org/10.1130/abs/2022NE-374827
Castro, A.E., *Yao, J., Wolfe, O.M., 2022 Some like it hot: Reevaluating the extent of anatexis in the Nashoba Terrane, East-Central Massachusetts , Geological Society of America, Abstracts with Programs, Vol 54, No. 3, https://doi.org/10.1130/abs/2022NE-375400
Castro, A.C., *Yao, J., Wolfe, O.M., George, F.R., Vasey, D.A., Cryptic Early “Barrovian” Metamorphism in the Trailing Edge of Ganderia: Evidence from Aluminosilicate Reaction Textures, Garnet Trace Element Zoning and Phase Equilibria Modeling, 2022 Goldschmidt Meeting
Yao, J., Castro, A., Castro, A., Brunet, I., Brunet, I., Roberts, N., Roberts, N., Wolfe, O. M., Wolfe, O. M., Kuiper, Y. D., Kuiper, Y. D., Hepburn, J. C., & Hepburn, J. C., 2022, “Barrovian” metamorphism in the Nashoba terrane: evidence from combined phase equilibria modeling, geothermobarometry, and petrographic analysis. Geological Society of America Abstracts with Programs. Vol 54, No. 5, https://doi.org/10.1130/abs/2022AM-381261
Metamorphic and Tectonic History of NYC
I was born and raised in the Bronx, and The City will always have a special place in my heart. I’m currently working with my friend and collaborator at the NYC Museum of Natural History Dr. Nick Tailby to constrain the metamorphic and tectonic history of the NYC basement units. We are particularly focused on the contact between the Manhattan and Hartland schists known as "Cameron’s Line.” Cameron’s Line is thought to be the suture between the ancient North American continent and a crustal fragment that collided during the Taconic orogeny. We hope to test this theory by better characterizing the largely unconstrained metamorphic history of the greatest city in the world!
The photo on the left is an example of the high-grade gneisses you can find in the Bronx!
Related Publications and Abstracts
*Zizka, E.L., *Van Scoy, E., *Brunet., I., *Erwin, M.C., Yao., J., Castro, A.E., Tailby, N.D., 2022, Searching for the suture: Applying geochemical techniques to unravel the nature of Cameron’s line in Central Park, NYC, Geological Society of America Abstracts with Programs. Vol 54, No. 3, https://doi.org/10.1130/abs/2022NE-375404
Castro, A.E., Tailby, N.T., Yao, J., Brunet, I.M., *Zizka, E.L.,*Van Scoy, E., 2022, Made in Manhattan: Insights into the Orogenic Evolution of the Manhattan Prong from Phase Equilibria and Geochronologic Constraints, AGU 2022 Fall Meeting.
Constraining the P–T Conditions of Devolatilization During Cycladic Subduction
The nucleation and growth of garnet are important fluid fluxes during the subduction of oceanic crust and sediment. I use Raman inclusion barometry, trace element thermometry, thermodynamic modeling, and kinetic modeling to accurately constrain the pressure-temperature conditions of garnet nucleation and growth.
The image on the right is a concentration map showing the relative concentration of Mn in a garnet from Syros, Greece. Hotter colors indicate high concentration while cooler colors indicate lower concentration. The map was taken on the SX-50 at the Rensselaer Polytechnic Institute.
Related Publications and Abstracts
Castro, A.E, and Spear, F., 2016, Reaction Overstepping and Reevaluation of the Peak P-T Conditions of the Blueschist unit Sifnos, Greece: Implications for the Cyclades Subduction Zone. International Geology Review.
Kohn, M.J., Castro, A.E., Karswell, B.S., Ranero, C., Spear, F.S., 2018, Shear heating reconciles thermal models with the metamorphic rock record of subduction. Proceedings of the National Academy of the Sciences.
Castro, A. E., Frank S. Spear, and J.T. Cheney, 2016 Application of epidote and quartz inclusion Raman barometry: reevaluation of the PT conditions of garnet bearing blueschists from Sifnos, Greece. Geological Society of America Annual Meeting
Castro, A.E., and Frank S. Spear, 2017, Lawsonite revisited: insights from integrated QuiG Raman barometry, trace element thermometry, and OS thermodynamic modelling of garnet inclusions in lawsonite pseudomorphs from Syros, Greece. Geological Society of America Annual Meeting
Castro, A.E., Frank S. Spear, and M.J. Kohn., 2017, Shear heating and metamorphism in subduction zones, 2. The seismic-aseismic transition at c. 50 km depth. American Geophysical Union Fall Meeting
P–T Conditions of Garnet Nucleation and Deformation in the Picuris Mtns
My postdoctoral work is focused on determining the P–T conditions of garnet formation and deformation in stretched pebble conglomerates from the Picuris Mtns, NM. This work allows me to combine more traditional petrologic techniques (e.g. geothermobarometry) with non-traditional tools (e.g. Raman inclusion barometry, trace element thermometry) and lets me spend a lot of time on the wonderful Cameca SX-100 microprobe at the UW Madison!
The image on the right is a concentration map showing the relative concentration of Ca in a garnet from a stretched pebble conglomerate in the Picuris Mountains. Hotter colors indicate high concentration while cooler colors indicate lower concentration. The map was captured on the SX-100 at the UW Madison.
