Determining P–T paths from garnet zoning using a brute-force computational method

Reconstructing metamorphic pressure–temperature ( P – T ) paths through petrographic textures, mineral assemblages, and compositions is fundamental to the understanding of orogenesis. We present a new method to derive the P – T path of a rock from mineral zoning. Using Perple_X (Connolly in Earth Planet Sci Lett 236(1–2):524–541, 2005 ) and a M atlab script, we forward model garnet zoning, parageneses, and mineral modes for an arbitrary set of possible P – T paths, and then compare the calculated results to mineral modes, textures, and zoning preserved in rocks. The best-fit P – T path is determined by comparing the calculated zoning to the measured zoning using the sum of squares. The results indicate that combining Mg#, Ca, and Mn zoning in garnet with mineral modes can yield precise constraints on the P – T path of a rock.