Precise U-Pb zircon ages and geochemistry of Jurassic granites, Ellsworth-Whitmore terrane, central Antarctica
2016; Geological Society of America; Volume: 129; Issue: 1-2 Linguagem: Inglês
10.1130/b31485.1
ISSN1943-2674
AutoresJohn P. Craddock, Mark D. Schmitz, James L. Crowley, Jeremiah Larocque, R. J. Pankhurst, N. Juda, Alexandros Konstantinou, Bryan Storey,
Tópico(s)High-pressure geophysics and materials
ResumoResearch Article| January 01, 2017 Precise U-Pb zircon ages and geochemistry of Jurassic granites, Ellsworth-Whitmore terrane, central Antarctica John P. Craddock; John P. Craddock † 1Geology Department, Macalester College, St. Paul, Minnesota 55105, USA †craddock@macalester.edu Search for other works by this author on: GSW Google Scholar Mark D. Schmitz; Mark D. Schmitz 2Department of Geosciences, Boise State University, Boise, Idaho 83725, USA Search for other works by this author on: GSW Google Scholar James L. Crowley; James L. Crowley 2Department of Geosciences, Boise State University, Boise, Idaho 83725, USA Search for other works by this author on: GSW Google Scholar Jeremiah Larocque; Jeremiah Larocque 2Department of Geosciences, Boise State University, Boise, Idaho 83725, USA Search for other works by this author on: GSW Google Scholar Robert J. Pankhurst; Robert J. Pankhurst 3Visiting Research Associate, British Geological Survey, Nottingham NG12 5GG, UK Search for other works by this author on: GSW Google Scholar Natalie Juda; Natalie Juda 4Geology Department, Macalester College, St. Paul, Minnesota 55105, USA §Present address: U.S. Geological Survey, Reston, Virginia 20192, USA. Search for other works by this author on: GSW Google Scholar Alexandros Konstantinou; Alexandros Konstantinou 4Geology Department, Macalester College, St. Paul, Minnesota 55105, USA #Present address: Cyprus Hydrocarbons Company, CY-1066 Nicosia, Cyprus. Search for other works by this author on: GSW Google Scholar Bryan Storey Bryan Storey 5International Antarctic Institute, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand Search for other works by this author on: GSW Google Scholar GSA Bulletin (2017) 129 (1-2): 118–136. https://doi.org/10.1130/B31485.1 Article history received: 12 Jan 2016 rev-recd: 09 Jun 2016 accepted: 12 Jul 2016 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John P. Craddock, Mark D. Schmitz, James L. Crowley, Jeremiah Larocque, Robert J. Pankhurst, Natalie Juda, Alexandros Konstantinou, Bryan Storey; Precise U-Pb zircon ages and geochemistry of Jurassic granites, Ellsworth-Whitmore terrane, central Antarctica. GSA Bulletin 2017;; 129 (1-2): 118–136. doi: https://doi.org/10.1130/B31485.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Ellsworth-Whitmore Mountain terrane of central Antarctica was part of the early Paleozoic amalgamation of Gondwana, including a 13,000 m section of Cambrian–Permian sediments in the Ellsworth Mountains deposited on Grenville-age crust. The Jurassic breakup of Gondwana involved a regional, bimodal magmatic event during which the Ellsworth-Whitmore terrane was intruded by intraplate granites before translation of the terrane to its present location in central Antarctica. Five widely separated granitic plutons in the Ellsworth-Whitmore terrane were analyzed for their whole-rock geochemistry (X-ray fluorescence), Sr, Nd, and Pb isotopic compositions, and U-Pb zircon ages to investigate the origins of the terrane magmas and their relationships to mafic magmatism of the 183 Ma Karoo-Ferrar large igneous province (LIP). We report high-precision (±0.1 m.y.) isotope dilution–thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon ages from granitic rocks from the Whitmore Mountains (208.0 Ma), Nash Hills (177.4–177.3 Ma), Linck Nunatak (175.3 Ma), Pagano Nunatak (174.8 Ma), and the Pirrit Hills (174.3–173.9 Ma), and U-Pb sensitive high-resolution ion microprobe (SHRIMP) ages from the Whitmore Mountains (200 ± 5 Ma), Linck Nunatak (180 ± 4 Ma), Pagano Nunatak (174 ± 4 Ma), and the Pirrit Hills (168 ± 4 Ma). We then compared these results with existing K-Ar ages and Nd model ages, and used initial Sr, Nd, and Pb isotope ratios, combined with xenocrystic zircon U-Pb inheritance, to infer characteristics of the source(s) of the parent magmas. We conclude that the Jurassic plutons were not derived exclusively from crustal melts, but rather they are hybridized magmas composed of convecting mantle, subcontinental lithospheric mantle, and lower continental crustal contributions. The mantle contributions to the granites share isotopic similarities to the sources of other Jurassic LIP mafic magmas, including radiogenic 87Sr/86Sr (0.706–0.708), unradiogenic 143Nd/144Nd (εNd < –5), and Pb isotopes consistent with a low-µ source (where μ = 238U/204Pb). Isotopes and zircon xenocrysts point toward a crustal end member of predominantly Proterozoic provenance (0.5–1.0 Ga; Grenville crust), extending the trends illustrated by Ferrar mafic intrusive rocks, but contrasting with the inferred Archean crustal and/or lithospheric mantle contributions to some basalts of the Karoo sector of the LIP. The Ellsworth-Whitmore terrane granites are the result of mafic rocks underplating the hydrous crust, causing crustal melting, hybridization, and fractionation to produce granitic magmas that were eventually emplaced as post-Ferrar, within-plate melts at higher crustal levels as the Ellsworth-Whitmore terrane rifted off Gondwana (47°S) before migrating to its current position (82°S) in central Antarctica. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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