Date(s) - 08/14/2019
GC Room 4429
On Wednesday, August 14, 2019 at 1:30 p.m., Peter Matt will take the Final Examination in Earth & Environmental Sciences in room 4429, at The Graduate Center, 365 Fifth Avenue, New York, N.Y. 10016. The title of the dissertation is, “The Role of Fluids in Ore Remobilization at the Balmat, NY, Zinc Deposit.”
Dr. Wayne Powell, Mentor, Brooklyn College
Dr. Steve Kidder, City College
Dr. Haydee Salmun, Hunter College
Dr. Jeff Chiarenzelli, St. Lawrence College
The Cross-Cutting zone of the Fowler ore body is one of the many ore bodies of the Balmat, NY massive sulfide zinc deposit that underwent remobilization during upper amphibolite metamorphism and associated deformation. The kilometer-scale remobilization is difficult to reconcile with purely solid-state processes. Given that other polymetallic ores of similar metamorphic grade have been shown to have undergone varying degrees of anatexis, SEM-EDS micro-petrographic analysis of ores was undertaken to determine if melts were present in Balmat ores during metamorphism and deformation. Low melting temperature micro-inclusions of sulfosalt and sulfide assemblages occur predominantly in Qtz-Py and Kfs-Py domains that cross-cut peak metamorphic assemblages. These results indicate that localized anatexis occurred on the prograde path, producing low volumes of melts of varying composition. Polymetallic sulfide melts were initiated by the prograde breakdown of minor phases containing low melting temperature chalcophile elements including As, Sb, Pb, and Cu. Alkaline silicate ± carbonate ± sulfide melts were fluxed by halogens, sulfur and other volatile components, released during metamorphism of evaporitic and organic-rich horizons in the marble-dominated host sequence. These low-volume melts and residual fluids would have wetted grain boundaries, affecting the rheology of the bulk ore, and facilitating remobilization of the ores through a combination of solid- and liquid-state processes.