作者: David R. Minor , Samuel B. Mukasa
DOI: 10.1016/S0016-7037(97)00098-7
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摘要: Abstract New high-precision zircon UPb 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 ArAr 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.