Vkothii
07-17-08, 02:32 AM
A Positive Test of East Antarctica–Laurentia Juxtaposition Within the Rodinia Supercontinent
J. W. Goodge,1* J. D. Vervoort,2 C. M. Fanning,3 D. M. Brecke,4 G. L. Farmer,5 I. S. Williams,3 P. M. Myrow,6 D. J. DePaolo7
The positions of Laurentia and other landmasses in the Precambrian supercontinent of Rodinia are controversial. Although geological and isotopic data support an East Antarctic fit with western Laurentia, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China.
New geologic, age, and isotopic data provide a positive test of the juxtaposition with East Antarctica: Neodymium isotopes of Neoproterozoic rift-margin strata are similar; hafnium isotopes of ~1.4-billion-year-old Antarctic-margin detrital zircons match those in Laurentian granites of similar age; and a glacial clast of A-type granite has a uraniun-lead zircon age of ~1440 million years, an epsilon-hafnium initial value of +7, and an epsilon-neodymium initial value of +4. These tracers indicate the presence of granites in East Antarctica having the same age, geochemical properties, and isotopic signatures as the distinctive granites in Laurentia.
1 Department of Geological Sciences, University of Minnesota–Duluth, Duluth, MN 55812, USA.
2 School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99164, USA.
3 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia.
4 Natural Resources Research Institute, University of Minnesota–Duluth, Duluth, MN 55811, USA.
5 Department of Geological Sciences and CIRES, University of Colorado, Boulder, CO 80309, USA.
6 Department of Geology, Colorado College, Colorado Springs, CO 80903, USA.
7 Department of Earth and Planetary Sciences, University of California, Berkeley, CA 94720, USA
--Science 11 July 2008:
Vol. 321. no. 5886, pp. 235 - 240
DOI: 10.1126/science.1159189
J. W. Goodge,1* J. D. Vervoort,2 C. M. Fanning,3 D. M. Brecke,4 G. L. Farmer,5 I. S. Williams,3 P. M. Myrow,6 D. J. DePaolo7
The positions of Laurentia and other landmasses in the Precambrian supercontinent of Rodinia are controversial. Although geological and isotopic data support an East Antarctic fit with western Laurentia, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China.
New geologic, age, and isotopic data provide a positive test of the juxtaposition with East Antarctica: Neodymium isotopes of Neoproterozoic rift-margin strata are similar; hafnium isotopes of ~1.4-billion-year-old Antarctic-margin detrital zircons match those in Laurentian granites of similar age; and a glacial clast of A-type granite has a uraniun-lead zircon age of ~1440 million years, an epsilon-hafnium initial value of +7, and an epsilon-neodymium initial value of +4. These tracers indicate the presence of granites in East Antarctica having the same age, geochemical properties, and isotopic signatures as the distinctive granites in Laurentia.
1 Department of Geological Sciences, University of Minnesota–Duluth, Duluth, MN 55812, USA.
2 School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99164, USA.
3 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia.
4 Natural Resources Research Institute, University of Minnesota–Duluth, Duluth, MN 55811, USA.
5 Department of Geological Sciences and CIRES, University of Colorado, Boulder, CO 80309, USA.
6 Department of Geology, Colorado College, Colorado Springs, CO 80903, USA.
7 Department of Earth and Planetary Sciences, University of California, Berkeley, CA 94720, USA
--Science 11 July 2008:
Vol. 321. no. 5886, pp. 235 - 240
DOI: 10.1126/science.1159189