New Zealand Journal of Geology and Geophysics abstracts

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A new garnet-bearing mineral breccia from North Otago, New Zealand

A. Reay
D. Chappell
B. Garden

Department of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand

Abstract   Recent road works have exposed a new outcrop of garnet-bearing breccia at Alma, North Otago. The rocks and minerals within the breccia are similar to those present in the classic mineral breccia at Kakanui. The mineral breccia is a mantle-sourced diatreme with associated marine reworked volcaniclastics. Mantle xenoliths include lherzolite and garnet pyroxenites occurring with megacrysts of garnet, clinopyroxene, kaersutite, and feldspar. However, detailed mineral chemistry and volcanic clast petrography suggest that the Alma deposit could be derived from a separate source.

Keywords   mineral breccia; megacryst; Kakanui; Alma; garnet; pyroxene; kaersutite; garnet pyroxenite

G01028 Received 7 September 2001; accepted 16 August 2002 ; published 6 December 2002
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 461-466
0028-8306/02/4504-0461 $7.00/0 © The Royal Society of New Zealand 2002 

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