Zircon UPb and hornblende 40Ar39Ar ages for the Dufek layered mafic intrusion, Antarctica: Implications for the age of the Ferrar large igneous province

作者: David R. Minor , Samuel B. Mukasa

DOI: 10.1016/S0016-7037(97)00098-7

关键词:

摘要: Abstract New high-precision zircon UPb ages for the Dufek intrusion establish crystallization age only layered mafic (sensu stricto) known in Ferrar igneous province, Antarctica, one of largest provinces world. Three concordant fractions from capping Lexington Granophyre yield an 183.9 ± 0.3 Ma (2σ), which we interpret as intrusion. Concordant a silicic dike crosscutting upper gabbroic sequence slightly younger 182.7 0.4 (2σ) . For both samples, agreement within errors between two and 207 pb∗/ 206 Pb∗ three each with unique set physical chemical characteristics demonstrates that inheritance older components country rocks was imperceptible. It also suggests assimilation or anatexis lower Paleozoic not dominant mechanism formation granophyre. These new dates agree, analytical errors, recent baddeleyite dolerite sills Karoo provinces, vastness rift axis along simultaneous magmatic activity occurred. Contemporaneity other Group supports possibility this pluton acted conduit magmas widely distributed flows. Hornblende 40 Ar 39 Ar (175 2 Ma) barely overlap those (179 gabbro section just below The hornblende may be explained by degassing inclusions protracted hydrothermal alteration preventing ArAr geochronometer form becoming closed-system higher level granophyre until after it had done so more deeply positioned dike. 179 is interpreted to represent cooling through retention temperature about 500°C. Combining yields rate approximately 100°C/m.y. Inasmuch rapid, can inferred bulk still fairly hot when dated emplaced.

参考文章(32)
J. A. Crame, M. R. A. Thomson, Janet W. Thomson, Geological Evolution of Antarctica ,(2011)
Paul R Renne, Alan L Deino, Robert C Walter, Brent D Turrin, Carl C Swisher III, Tim A Becker, Garniss H Curtis, Warren D Sharp, Abdur-Rahim Jaouni, None, Intercalibration of astronomical and radioisotopic time Geology. ,vol. 22, pp. 783- 786 ,(1994) , 10.1130/0091-7613(1994)022<0783:IOAART>2.3.CO;2
A.N. LeCheminant, L.M. Heaman, Mackenzie igneous events, Canada: Middle Proterozoic hotspot magmatism associated with ocean opening Earth and Planetary Science Letters. ,vol. 96, pp. 38- 48 ,(1989) , 10.1016/0012-821X(89)90122-2
Scott D. Samson, E.Calvin Alexander, Calibration of the interlaboratory 40Ar39Ar dating standard, MMhb-1 Chemical Geology: Isotope Geoscience Section. ,vol. 66, pp. 27- 34 ,(1987) , 10.1016/0168-9622(87)90025-X
Philip R. Kyle, Development of heterogeneities in the subcontinental Mantle: Evidence from the Ferrar Group, Antarctica Contributions to Mineralogy and Petrology. ,vol. 73, pp. 89- 104 ,(1980) , 10.1007/BF00376262
T.S. Brewer, Mesozoic dolerites from Whichaway Nunataks Antarctic Science. ,vol. 1, pp. 151- 155 ,(1989) , 10.1017/S0954102089000222