Polymetamorphism in the NE Shackleton Range, Antarctica: Constraints from Petrology and U---Pb, Sm---Nd, Rb---Sr TIMS and in situ U---Pb LA-PIMMS Dating
include garnet with contrasting zonation patterns and two age spectra. Garnet porphyroblasts in K-rich kyanite---sillimanite---staurolite---garnet---muscovite---biotite schists from Lord Nunatak show prograde growth zonation, and give Sm---Nd garnet, U---Pb monazite and Rb---Sr muscovite ages of 518...
Main Authors: | , , , , |
---|---|
Other Authors: | |
Format: | Text |
Language: | English |
Published: |
2003
|
Subjects: | |
Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.523.5657 http://petrology.oxfordjournals.org/content/45/5/949.full.pdf |
Summary: | include garnet with contrasting zonation patterns and two age spectra. Garnet porphyroblasts in K-rich kyanite---sillimanite---staurolite---garnet---muscovite---biotite schists from Lord Nunatak show prograde growth zonation, and give Sm---Nd garnet, U---Pb monazite and Rb---Sr muscovite ages of 518 5, 514 1 and 499 12Ma, respectively. Geothermobarometry and P---T pseudo-section calculations in the model system CaO---Na2O---K2O---TiO2---MnO---FeO---MgO---Al2O3---SiO2---H2O are consistent with garnet growth during prograde heating from 540C/7 kbar to 650C/75 kbar, and partial resorption during a subsequent P---T decrease to 5650C at 56 kbar. All data indicate that rocks from Lord Nunatak were affected by a single orogenic cycle. In contrast, garnet porphyroblasts in K-poor kyanite---sillimanite---staurolite---garnet---cordierite---biotite-schists from Meade Nunatak show two growth stages and diffusion-controlled zonation. Two |
---|