Abstract
The garnet chemical zoning method (GZM) is a reliable thermodynamic approach for forward modeling pressure-temperature (P-T) paths using observed garnet and bulk rock compositions. However, intracrystalline diffusion is known to compromise the integrity of GZM modeled garnet-growth P-T paths. For this reason, extracting reliable metamorphic estimates from garnet-bearing schists in the Central Menderes Massif (CMM), western Turkey, has been difficult. To evaluate the impact of diffusion on GZM, we simulate garnet growth and diffusion for an average metapelite using the program Theria_G. Modeled garnet compositions from four simulations are used to estimate P-T conditions and paths by GZM, which are compared against Theria_G specified P-T-t trajectories. Factors influencing results are heating/cooling rate, grain size, and peak T. At a maximum T of 610 °C, both undiffused and diffused garnet compositions returned estimates comparable to prescribed conditions regardless of heating/cooling rate. Diffused profiles from simulations reaching a maximum T of 670 °C also reproduced prescribed P-T paths if tectonism occurred at high heating/cooling rates (50 °C/my). From these insights and additional Theria_G simulation-derived observations for CMM garnets, we deduce that metamorphism in the region exceeded 650 °C and achieved a maximum burial P between 8–10 kbar prior to Cenozoic exhumation.
Highlights
Original divalent calculations have long been a focus of study (e.g., [80,81,82,83,84,85,86,87,88,89,90,91]), documenting how diffu cation zoning in garnet < 100 μm will be modified if the crystal encounters T > 600 ◦ C for a impacts
We evaluate the validity of metamorphic conditions reported from diffusively zoned garnets exposed in the central Menderes Massif, western Turkey [23]
garnet zoning thermobarometric method (GZM) is a promising technique that can sharpen our understanding of the lithospheric dynamics responsible for metamorphism
Summary
The garnet zoning thermobarometric method (GZM), referencing the approach of [17], can provide a detailed reconstruction of nuanced lithosphere dynamics during the prograde burial of crustal rocks, as is the case in the Menderes Massif, western Turkey [21,23]. There the method was used to reveal that garnets throughout the southern portion of the massif retain a record of metamorphic growth in response to Cenozoic burial, but they capture an intermediate pressure inflection (~1 kbar drop) interpreted as a brief period of local denudation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
