Physics
Scientific paper
Jul 1968
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1968gecoa..32..669a&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 32, Issue 7, pp.669-697
Physics
11
Scientific paper
Almost all of the acidic plutonic rocks in New Zealand occur in western South Island where they are of batholithic dimensions. Rb-Sr and U-Pb geochronology of regionally selected samples of these and associated metamorphic rocks indicate two main periods of plutonic and metamorphic activity. The older occurred in the mid-Paleozoic probably about 350-370 m.y. ago and the younger during the late Mesozoic with a strong pulse about 100-120 m.y. ago. The late Mesozoic results associate plutonic and metamorphic activity in southwestern New Zealand with the Rangitata Orogeny which uplifted and regionally metamorphosed sediments of the New Zealand Geosyncline of eastern and northern New Zealand. Plutonic rocks, dominantly ultrabasic or basic, occur in the marginal area of the New Zealand Geosyncline and at least some of these were emplaeed early in the history of the geosyncline during Permian times. No crystalline in situ rocks of primary Precambrian age have been found; metaplutonic parts of the Charleston Gneiss, previously mapped as Precambrian, are probably middle or lower Paleozoic plutonic rocks metamorphosed during the Rangitata Orogeny. However, Pb 207 / Pb 206 ages ranging from 1170 to 1480 m.y. have been determined for several fractions of rounded detrital zircon from three widespread samples of the Greenland Series, an extensive pre-Devonian sedimentary unit of western South Island. The U-Pb ages for these zircons are highly discordant and indicate the Pb 207 / Pb 208 ages are minimum ages for the oldest source rocks which supplied the zircons. These results are fundamental for the tectonic picture of the southwest Pacific continental margin and show the presence of an acidic Precambrian terrane near western New Zealand.
No associations
LandOfFree
Regional geochronology of New Zealand does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Regional geochronology of New Zealand, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Regional geochronology of New Zealand will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-757261