TY  - JOUR
A1  - Scott, James
A1  - Muhling, Janet
A1  - Fletcher, Ian
A1  - Billia, Marco
A1  - Palin, J. Michael
A1  - Elliot, Tim
A1  - Günter, Christina
T1  - The relationship of Palaeozoic metamorphism and S-type magmatism on the paleo-Pacific Gondwana margin
JF  - Lithos : an international journal of mineralogy, petrology, and geochemistry
N2  - A massive pulse of granitic magma was rapidly emplaced into the once contiguous West Antarctic and New Zealand segments of the palaeo-Pacific margin of the Gondwana supercontinent at similar to 371 Ma. In New Zealand, these Late Devonian S-type granitoids cover an areal extent of > 3400 km(2), but the tectonic setting for crustal partial melting has remained unclear because most of the exposure represents either emplacement-level, or rocks that have been reworked during Cretaceous orogenesis. New petrologic data indicate that aluminous paragneisses and orthogneisses in the Bonar Range represent a rare portion of Devonian middle crust that preserves evidence for the initiation of crustal melting. The investigated rocks outline the tail of a clockwise P-T path that involved partial melting at peak conditions (similar to 670 degrees C, 5.1 kb), deformation during the immediately following near-isothermal decompression, and then partial re-equilibration under static conditions. Syn- to post-kinematic growth of zoned monazite establishes the timing of recrystallisation to a similar to 16 Ma period that began at 373.4 +/- 4.1 Ma. This age overlaps with the initiation of regional Karamea S-type granitic magmatism. Although estimated metamorphic conditions were insufficient for large amounts of melt to have been produced from Bonar Range pelites (calculated melt volumes are <10%), they do provide evidence consistent with widespread heating and partial melting in the deeper crust. This heating episode was contemporaneous with partial melting in Fiordland (New Zealand) and West Antarctica, although Mesozoic thermal and deformational events complicate the Palaeozoic record in both those areas. Nevertheless, the apparent 1000 s km of along-strike crustal partial melting indicates that a continental-scale tectonic plate margin re-organisation took place at this time. The cause in the New Zealand segment was most likely, but not unequivocally, an extensional tectonic regime with an elevated geothermal gradient caused by conductive heating from a shallowed lithospheric mantle.
KW  - Geothermobarometric P-T
KW  - Monazite growth
KW  - Palaeozoic metamorphism New Zealand
KW  - Gondwana
Y1  - 2011
U6  - https://doi.org/10.1016/j.lithos.2011.09.008
SN  - 0024-4937
VL  - 127
IS  - 3-4
SP  - 522
EP  - 534
PB  - Elsevier
CY  - Amsterdam
ER  -