| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Petrology | Volume 44 | Number 11 | Pages 2053-2080 | 2003
© Oxford University Press 2003; all rights reserved
Phonolitic Diatremes within the Dunedin Volcano, South Island, New Zealand
1 SCHOOL OF SCIENCE AND TECHNOLOGY, THE UNIVERSITY OF WAIKATO, PRIVATE BAG 3105, HAMILTON, NEW ZEALAND
2 DEPARTMENT OF GEOLOGY, THE UNIVERSITY OF OTAGO, PO BOX 56, DUNEDIN, NEW ZEALAND
3 SCHOOL OF EARTH SCIENCES, UNIVERSITY OF MELBOURNE, VIC. 3010, AUSTRALIA
4 SCHOOL OF GEOSCIENCES, MONASH UNIVERSITY, CLAYTON, VIC. 3800, AUSTRALIA
* Corresponding author. E-mail: r.price{at}waikato.ac.nz
The Port Chalmers Breccia is a vent-filling, clastic volcanic unit exposed within the Miocene Dunedin Volcano of South Island, New Zealand. Clasts (up to in excess of 1 m but generally <20 cm) are supported in ash and fine lapilli of phonolitic (ne-benmoreite or tephro-phonolite) composition and the dominant clast type (55 to almost 100%) is also phonolitic. Less abundant lithologies include ne-normative basalt (basanite), hawaiite, mugearite and trachyandesite, syenites and microsyenites, coarse-grained mafic (gabbros) and ultramafic rocks (pyroxenites, hornblendites), schists and sediments. The breccias were emplaced as diatremes associated with localized, but highly explosive, eruptive events in which mantle-derived CO2 was an important component. The syenitic and ultramafic clasts could represent intrusive suites produced by crystal fractionation acting on parental ne-benmoreite magmas that may themselves have been derived by crystal fractionation from basanitic precursors. An alternative variation on this model is that the parental ne-benmoreites were generated through partial melting of an alkalic igneous underplate. Sr, Nd and Pb isotopic compositions are strikingly similar to those of intraplate igneous rocks, ranging in age from 100 to less than 10 Ma, from elsewhere in the South Island, and New Zealand's sub-Antarctic islands, the south Tasman Sea and the Ross Sea region. This regional, HIMU-influenced, isotopic signature is believed to be derived from within the lithospheric mantle.
KEY WORDS: phonolite; diatreme; nepheline syenite; Dunedin Volcano; alkalic rocks; fractional crystallization
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. F. Cooper and L. A. Paterson CARBONATITES FROM A LAMPROPHYRIC DYKE-SWARM, SOUTH WESTLAND, NEW ZEALAND Can Mineral, August 1, 2008; 46(4): 753 - 777. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. S. PANTER, J. BLUSZTAJN, S. R. HART, P. R. KYLE, R. ESSER, and W. C. MCINTOSH The Origin of HIMU in the SW Pacific: Evidence from Intraplate Volcanism in Southern New Zealand and Subantarctic Islands J. Petrology, September 1, 2006; 47(9): 1673 - 1704. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. LEGENDRE, R. C. MAURY, M. CAROFF, H. GUILLOU, J. COTTEN, C. CHAUVEL, C. BOLLINGER, C. HEMOND, G. GUILLE, S. BLAIS, et al. Origin of Exceptionally Abundant Phonolites on Ua Pou Island (Marquesas, French Polynesia): Partial Melting of Basanites Followed by Crustal Contamination J. Petrology, September 1, 2005; 46(9): 1925 - 1962. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. COOK, R. M. BRIGGS, I. E. M. SMITH, and R. MAAS Petrology and Geochemistry of Intraplate Basalts in the South Auckland Volcanic Field, New Zealand: Evidence for Two Coeval Magma Suites from Distinct Sources J. Petrology, March 1, 2005; 46(3): 473 - 503. [Abstract] [Full Text] [PDF]
|
|