Clumped isotope thermometry of calcite and dolomite in a contact metamorphic environment

摘要: Clumped isotope compositions of slowly-cooled calcite and dolomite marbles record apparent equilibrium temperatures roughly 150-200 °C 300-350 °C, respectively. Because clumped are sensitive to the details T-t path within these intervals, measurements Δ_(47) values coexisting can place new constraints on thermal history low-grade metamorphic rocks over a large portion upper crust (from ∼5 ∼15 km depth). We studied geochemistry in from Notch Peak contact aureole, Utah. Here, flat-lying limestones were intruded by pluton, producing regular, zoned aureole. Calcite uniform, 156 ± 12 ˚C (2σ s.e.), across varying high-grade that exceeded 500 nominally unmetamorphosed >5 intrusion. This result appears require temperature far pluton was close this value; an ambient just 20 lower would not have permitted substantial re-equilibration, should preserved depositional or early diagenetic several pluton. Combining with depth overlying strata suggests country rock here had average regional geotherm 22.3–27.4 ˚C/km late Jurassic Period until at least middle Paleogene Period. Dolomite all samples above talc+tremolite-in isograd 328^(+13)_(-12) (1σ consistent blocking we expect for cooling peak conditions. At greater distances, records (anchi)metamorphism pre-metamorphic The interface between domains is location 330 isotherm associated Multiple-phase complemented bulk δ^(13)C δ^(18)O dolomite-calcite thermometry. These isotopic exchange thermometers largely 4 contact, indicating recrystallization occur even too produce growth conventional index minerals (i.e., talc tremolite). Altogether, work demonstrates potential methods quantify conditions metamorphism sub-greenschist facies.