New Zealand Journal of Geology and Geophysics abstracts
SHRIMP ion probe zircon geochronology and Sr and Nd isotope
geochemistry for southern Longwood Range and Bluff Peninsula intrusive
rocks of Southland, New Zealand
Richard C. Price
School of Science and Engineering
University of Waikato
Private Bag 3105
Hamilton, New Zealand
Trevor R. Ireland
Research School of Earth Sciences
Australian National University
Canberra, ACT 0200, Australia
Roland Maas
School of Earth Sciences
University of Melbourne
Parkville, Vic. 3010, Australia
Richard J. Arculus
Department of Earth & Marine Sciences
Australian National University
Canberra, ACT 0200, Australia
Abstract Permian–Jurassic ultramafic to
felsic intrusive complexes at Bluff Peninsula and in the southern
Longwood Range along the Southland coast represent a series of
intra-oceanic magmatic arcs with ages spanning a time interval of
110 m.y. New SHRIMP U-Pb zircon data for a quartz diorite from the
Flat Hill complex, Bluff Peninsula, yield an age of 259 ±
4 Ma, consistent with other geochronological and paleontological
evidence confirming a Late Permian age. The new data are consistent
with an age of c. 260 Ma for the intrusive rocks of the Brook
Street Terrane. SHRIMP U-Pb zircon ages for the southern
Longwood Range confirm that intrusions become progressively younger
from east to west across the complex. A gabbro at Oraka Point (eastern
end of coastal section) has an age of 245 ± 4 Ma and shows
virtually no evidence of zircon inheritance. The age is significantly
different from that of the Brook Street Terrane intrusives. Zircon ages
from the western parts of the section are younger and more varied
(203–227 Ma), indicating more complex magmatic histories. A
leucogabbro dike from Pahia Point gives the youngest emplacement age of
142 Ma, which is similar to published U-Pb zircon ages for the
Anglem Complex and Paterson Group on Stewart Island.
Keywords U-Pb geochronology; zircon; SHRIMP; granites; Brook Street Terrane
G05057; Received 8 December 2005; accepted 19 May 2006; Online publication date 24 July 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49: 291–303
0028–8306/06/4903–0291 © The Royal Society of New Zealand 2006
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