New Zealand Journal of Geology and Geophysics abstracts

---

Granitoids of the Dry Valleys area, southern Victoria Land, Antarctica: plutons, field relationships, and isotopic dating

ANDREW H. ALLIBONE

Department of Geology
James Cook University of North Queensland
Townsville, Q4811, Australia*

SIMON C. COX

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

IAN J. GRAHAM

Institute of Geological and Nuclear Sciences Ltd
P.O. Box 30 368
Lower Hutt, New Zealand

ROBERT W.SMELLIE

Exploration Department
Western Mining Corporation Ltd
Kambalda, Western Australia 6442

ROY D. JOHNSTONE
SIMON G. ELLERY

Department of Geology
University of Otago

KEN PALMER

Analytical Facility
Research School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand

*Present address: Etheridge and Henley Geoscience Consultants, P.O. Box 3778, Manuka, A.C.T. 2603, Australia.

Abstract Detailed mapping throughout much of the Dry Valleys area indicates the region is underlain by 15 major granitoid plutons and numerous smaller plugs and dikes. Intrusive relationships of these plutons and dikes indicate repeated intrusion of superficially similar granitoids at different times. Sufficient internal lithologjc variation occurs within individual plutons, to allow correlation with several of the previously defined granitoid units based on lithologic character. Consequently, previous subdivision schemes based on lithology are no longer tenable and are here replaced with a subdivision scheme based on the identification of individual plutons.
The elongate, concordant Bonney, Denton, Cavendish, and Wheeler Plutons, which range in composition between monzodiorite and granodiorite, are the oldest relatively undeformed plutons in the Dry Valleys area. Each pluton is characterised by flow alignment of K-feldspar megacrysts, hornblende, biotite, and mafic enclaves. Field relationships and radiometric dating indicate these are deep-level plutons, emplaced synchronous with upper amphibolite facies meta-morphism of the adjacent Koettlitz Group between 589 and 490 Ma ago. Elongate, discordant plutons of equigranular homogeneous biotite granodiorite and granite (Hedley, Valhalla, St Johns, Suess) were subsequently emplaced by stoping at a relatively high crustal level at 490 Ma.
These eight plutons are cut by numerous swarms of Vanda mafic and felsic porphyry dikes. The ovoid, discordant, high level Pearse, Nibelungen, Orestes, Brownworth, Swinford, and Harker Plutons, emplaced between c. 486 and 477 Ma, display mutually crosscutting relationships with the youngest of die Vanda dikes. These younger plutons range in composition between monzonite and granite. Some are characterised by K-feldspar megacrystic textures superficially similar to some of the oldest concordant plutons.

Keywords granitoids; Bonney; Cavendish; Nibelungen; Denton; Wheeler; Catspaw; Valhalla; Hedley; Suess; St Johns; Orestes; Pearse; Brownworth; Harker; Swinford; plutons; radiometric dating; Dry Valleys; Vanda; southern Victoria Land; Antarctica

Received 2 June 1992; published 14 September 1993
New Zealand Journal of Geology & Geophysics, 1991, Vol. 36: 281—297
0028Ð8306/06/3603—0281 ©The Royal Society of New Zealand 1991

PDF file of entire paper: medium quality (1893K); (scanned from paper original: notes about this process). Digitisation of this article from the printed journal was kindly facilitated by the Geological Society of New Zealand

---

This year's abstracts | Journal home page | All abstracts | Publishing home page