Journal of Zhejiang University SCIENCE A
(Monthly)

2006   Vol. 7   Suppl. II   p. 315-319

First report of zircon SHRIMP U-Pb dating from the Dufek granite in the Sør Rondane Mountains, East Antarctica

Li Zi-Long^†1, Du Zheng-Min², Yang Shu-Feng¹, Chen Han-Lin¹, Song Biao³, Liu Dun-Yi³

(¹Department of Earth Science, College of Science, Zhejiang University, Hangzhou 310027, China)
(²First Geological Party of Zhejiang Province, Hangzhou 310012, China)
(³Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China)
^†E-mail: zilongli@zju.edu.cn
Received Feb. 20, 2006 revision accepted May 30, 2006

Abstract: We report here the first zircon SHRIMP U-Pb chronological result yielding age of (619±7) Ma (11 spots) for the Dufek granite, the largest one of the Early Paleozoic granitoids in the Sør Rondane Mountains, East Antarctica. The analyzed zircon crystals are euhedral, have zonal patterns and Th/U ratios of 0.22~1.04, indicating magmatic genesis. The single zircon crystal has the ²⁰⁶Pb/²³⁸U age of 664 Ma to 600 Ma with the analyzed spots being from the core parts and mantle-rim part of the zircon grains. The result of 619 Ma analysis shows beyond doubt that the Dufek granite formed during 620 Ma is much older by at least 70 Ma than that of the previously widely believed (500~550 Ma) obtained by Rb-Sr, Sm-Nd and K-Ar isotopic analyses of the Sør Rondane Mountains Pan-African granitoids. Previous chemical characteristics and isotopic data supported that the Dufek granite has chemical affinity with A-type granites under within-plate setting. The U-Pb age of 620 Ma for magmatic zircons in the Dufek granite therefore may represent the age of earlier melt crystallization that occurred at the Late Neo-Proterozoic during the extensional tectonic setting during/after Gondwanaland formation.

Key words: Zircon SHRIMP U-Pb age dating, Pan-African granite, Tectonothermal event, Sør Rondane Mountains, Antarctica
doi:10.1631/jzus.2006.AS0315             CLC number: P58; P59

References:

[1] Arakawa, Y., Takahashi, Y., Tainosho, Y., 1994. Nd and Sr isotopic characteristics of the plutonic rocks in the Sør Rondane Mountains, East Antarctica. Proc. NIPR Sym. Antarct. Geosci., 7:49-59.

[2] Asami, M., Suzuki, K., Grew, E.S., 2005. Monazite and zircon dating by the chemical Th-U-Total Pb Isochron method (CHIME) from Alasheyev bight to the Sør Rondane Mountains, East Antarctica: A reconnaissance study of the Mozambique suture in Eastern Queen Maud Land. The Journal of Geology, 113(1):59-82.

[3] Black, L.P., Kamo, S.L., Allen, C.M., Aleinikoff, J.N., Davisb, D.W., Korscha, R.J., Foudoulis, C., 2003. TEMORA 1: A new zircon standard for Phanerozoic U-Pb geochronology. Chemical Geology, 200(1-2):155-170.

[4] Brown, M., Raith, M., 1996. First evidence of ultrahigh-temperature decompression from the granulite province of southern India. Journal Geological Society of London, 153:819-822.

[5] Claoué-Long, J.C., Compston, W., Roberts, J., Fanning, C.M., 1995. Two Carboniferous Ages: A Comparison of SHRIMP Zircon Dating with Conventional Zircon Ages and ⁴⁰Ar/³⁹Ar Analysis. In: Berggren, W.A., Kent, D.V., Aubrey, M.P., Hardenbol, J. (Eds.), Geochronology Time Scales and Global Stratigraphic Correlation: SEPM (Society for Sedimentary Geology). Special Publication, 54:3-21.

[6] Li, Z.L., Tainosho, Y., Shiraishi, K., Owada, M., 2003a. Chemical characteristics of fluorine-bearing biotite of early Paleozoic plutonic rocks from the Sør Rondane Mountains, East Antarctica. Geochemical Journal, 37:145-161.

[7] Li, Z.L., Tainosho, Y., Kimura, J.I., Shiraishi, K., Owada, M., 2003b. Pan-African alkali granitoids from the Sør Rondane Mountains, East Antarctica. Gondwana Research, 6(4):595-605.

[8] Li, Z.L., Tainosho, Y., Kimura, J.I., Shiraishi, K., 2005. Characterization of the Mefjell plutonic complex from the Sør Rondane Mountains, East Antarctica: Implications for the petrogenesis of Pan-African plutonic rocks of East Gondwanaland. The Island Arc, 14(4):636-652.

[9] Ludwig, K.R., 2002. SQUID 1.02, a User’s Manual. Berkeley Geochronology Center Special Publication, Berkeley, CA, USA.

[10] Osanai, Y., Shiraishi, K., Takahashi, Y., Ishizuka, H., Moriwaki, K., Tainosho, Y., Tsuchiya, N., Sakiyama, T., Toyoshima, T., Owada, M., Kojima, H., 1996. Explanatory Text of Geological Map of Brattnipene, Sør Rondane Mountains, Antarctica. Antarctic Geological Map Series (Sheet 34, Brattnipene). National Institute of Polar Research, Japan, p.29.

[11] Shiraishi, K., Kagami, H., 1992. Sm-Nd and Rb-Sr Ages of Metamorphic Rocks from the Sør Rondane Mountains, East Antarctica. In: Yoshida, Y., Kaminuma, K., Shiraishi, K. (Eds.), Recent Progress in Antarctic Earth Science. TERRAPUB, Tokyo, p.29-35.

[12] Shiraishi, K., Osanai, Y., Ishizuka, H., Asami, M., 1997. Antarctic Geological Map Series (Sheet 35, Sør Rondane Mountains). NIPR, Japan.

[13] Shiraishi, K., Fanning, C.M., Armstrong, R., Motoyoshi, Y., 1999. New Evidence for Polymetamorphic Events in the Sør Rondane Mountains, East Antarctica. VIII International Symposium Antarctic Earth Sciences, July 5~9, 1999. Victoria University of Wellington, Wellington, p.280.

[14] Song, B., Zhang, Y., Wan, Y., Jian, P., 2004. Mount making and procedure of the SHRIMP dating. Geological Review, 48(supp.):26-30 (in Chinese with English abstract).

[15] Tainosho, Y., Takahashi, Y., Arakawa, Y., Osanai, Y., Tsuchiya, N., Sakiyama, T., Owada, M., 1992. Petrochemical Character and Rb-Sr Isotopic Investigation of the Granitic Rocks from the Sør Rondane Mountains, East Antarctica. In: Yoshida, Y., Kaminuma, K., Shiraishi, K. (Eds.), Recent Progress in Antarctic Earth Science. TERRAPUB, Tokyo, p.45-54.

[16] Takahashi, Y., Arakawa, Y., Sakiyama, T., Osanai, Y., Makimoto, H., 1990. Rb-Sr and K-Ar whole rock ages of the plutonic bodies from the Sør Rondane Mountains, East Antarctica. Proc. NIPR Sym. Antarct. Geosci., 4:1-8.