Metamorphic Evolution of the Lower Nappes of the Kalak Nappe Complex in Eastern Finnmark (Norway)

• Main Author: Heldwein, Olivier Karl Anton
• Format: Thesis
• Language: unknown
• Published: 2020
• Subjects: Kalak; Norway; Finnmark
• Online Access: https://curve.carleton.ca/b86dd791-d40c-4b00-a077-eb987a52f3a6; https://doi.org/10.22215/etd/2020-14299; https://ocul-crl.primo.exlibrisgroup.com/permalink/01OCUL_CRL/j2o5om/alma991022809619605153

Garnet grains in metapelites of the lower nappes of the Kalak Nappe Complex in Eastern Finnmark typically show two growth zones: Garnet 1 forms the cores of the grains and grew along a P-T path with a ~20 bar/°C slope. Its growth started at ~515 °C and ~3250-5500 bar and finished at ~570 °C. The maximum pressure experienced during garnet 1 growth increases down the nappe pile. Garnet 2, which forms the rims of the garnet grains, grew during a near-isothermal pressure increase of ~500-1500 bar. Microtextural evidence indicates pre- to syn-kinematic growth of garnet 1 and post-kinematic growth of garnet 2. Lu-Hf garnet/whole-rock age dating points to growth of garnet 1 at 463±17 Ma and a maximum age of ~429 Ma for garnet 2. The hiatus between garnet 1 and garnet 2 growth was of short duration, and garnet growth might have been continuous in the lowest structural levels.