Pember Diorite—an Early Jurassic intrusion in the Rakaia Terrane, Puketeraki Range, Canterbury, New Zealand

Abstract

Biotite‐hornblende‐augite microdiorite within the Puketeraki Range and Lees Valley of inland North Canterbury forms small stocks and dikes intruding Rakaia Terrane rocks and is here named the Pember Diorite. Geochemically the Pember Diorite has medium to high‐K tholeiitic characteristics. Ar‐Ar dating of amphibole gives a crystallisation age of 185.6±3.3 Ma (2σ) (Early Jurassic), somec. 25 m.y. younger than the Late Triassic Rakaia Terrane rocks it intrudes. The Pember Diorite has undergone prehnite‐pumpellyite facies metamorphism, indicating that at least some of the regional low‐grade metamorphism in the Rakaia Terrane is younger than c. 186 Ma.

Keywords:

• Jurassic
• Puketeraki Range
• Canterbury
• Rakaia Terrane
• Pember Diorite
• geochemistry
• geochronology
• metamorphism, new stratigraphic name