This paper proposes an alternative high-order, non-genetic classification of the basement rocks of medial New Zealand. More than 90% of the rocks in the Median Tectonic Zone are plutonic and can be included in part of a newly defined Carboniferous to Early Cretaceous, ca 10,200 km 2 composite regional batholith - the Median Batholith. The plutonic rocks of the batholith intrude the volcanic and sedimentary rocks of the Brook Street and Takaka Terranes (Eastern and Western Provinces, respectively). Emerging matches between the chronology of magmatism in the Median Batholith and batholiths in the Western Province also support probable in situ growth of most of the batholith. The internal and external contacts, and shape, of the batholith have been strongly modified by post-plutonic Cretaceous and Late Cenozoic tectonism, particularly within 50 km of the Alpine Fault. The Median Batholith represents a significant but previously little-recognised 250 Ma record of magmatism along the continental margin of South Gondwana, and invites comparison with other Cordilleran batholiths.
Ce manuscrit propose une classification non-genetique des roches du socle de la Nouvelle Zelande centrale. Plus de 90% des roches de la Zone Tectonique Mediane sont plutoniques et peuvent etre considerees en bonne partie comme composant un batholite regional (10.200 km 2 ) composite Carbonifere a Cretace inferieur nouvellement defini que nous appelons le batholite median. Les roches plutoniques de ce batholite intrudent les roches volcaniques et sedimentaires des terranes de Brook Street et de Takaka (Provinces orientale et occidentale, respectivement). La concordance qui apparait entre la chronologie du magmatisme au sein du batholite median et des batholites de la Province occidentale suggere egalement une genese en place de la plus grande partie du batholite. Les contacts internes et externes, comme la forme du batholite ont ete fortement modifies par les tectoniques post-plutoniques Cretacee et Cenozoique terminal, particulierement a moins de 50 km de la faille alpine. Le batholite median represente un enregistrement magmatique important, quoique peu reconnu, de 250 Ma le long de la marge continentale du Gondwana meridional, ce qui invite a le comparer avec d'autres batholites cordillerains.