Precise U–Pb dating of Paleoproterozoic mafic dyke swarms of the Dharwar craton, India: Implications for the existence of the Neoarchean supercraton Sclavia

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• 作者：Jason E. French ; Larry M. Heaman
• 关键词：Mafic dyke swarm ; Dharwar craton ; U– ; Pb geochronology ; Continental reconstructions ; Paleoproterozoic
• 刊名：Precambrian Research
• 出版年：2010
• 出版时间：1 December 2010
• 年：2010
• 卷：183
• 期：3
• 页码：416-441
• 全文大小：4091 K

文摘

We report seven high precision U–Pb age determinations for mafic dykes from a number of major Precambrian swarms located in the Dharwar craton, south India. These new age results define two previously unrecognized widespread Paleoproterozoic dyking events at 2221–2209 and 2181–2177 Ma, and confirm a third at 2369–2365 Ma. Three parallel E–W trending mafic dykes from the petrographically and geochemically variable Bangalore dyke swarm, the most prominent swarm in the Dharwar craton, yield indistinguishable U–Pb baddeleyite ages of 2365.4 ± 1.0, 2365.9 ± 1.5 and 2368.6 ± 1.3 Ma, indicating rapid emplacement in less than five million years. A compilation of Paleoproterozoic U–Pb ages for mafic magmatic events worldwide indicates that the 2369–2365 Ma Bangalore dyke swarm represents a previously unrecognized pulse of mafic magmatism on Earth.

A protracted episode of Pan-Dharwar mafic dyke swarm emplacement at 2.2 Ga is the most geographically widespread Paleoproterozoic mafic magmatic event currently recognized in the Dharwar craton. U–Pb baddeleyite dating of two dykes located south of the Cuddapah basin yield ages of 2220.5 ± 4.9 Ma (N–S trending Kandlamadugu dyke) and 2209.3 ± 2.8 Ma (NW–SE trending Somala dyke), indicating emplacement of two distinct subswarms in the region. Two dykes from the northern Dharwar craton (the E–W Bandepalem and NW–SE Dandeli dykes) separated by 550 km yield indistinguishable U–Pb ages of 2176.5 ± 3.7 (baddeleyite and zircon) and 2180.8 ± 0.9 Ma (baddeleyite), respectively. Collectively, these age data hint at the presence of a giant 2.18 Ga radiating mafic dyke swarm that spans >100,000 km² of the Dharwar craton, which has a focal point west of the present day Deccan Flood basalt province.

The identification of Pan-Dharwar mafic dyke swarm emplacement at 2.2 Ga allows for new global correlations with contemporaneous mafic magmatic events previously recognized in many other Archean cratons worldwide (e.g., within Antarctica, Australia, Finland, Greenland, and North America). Increasing evidence suggests that this global mafic magmatism at 2.2 Ga was linked with intracontinental rifting, enhanced mantle plume activity, and the breakup of one or more Archean continents. We highlight the similarity in timing of Paleoproterozoic (2.23–2.17 Ga) mafic dyke swarm emplacement recorded in the Dharwar and Slave cratons and use the correlation of high precision U–Pb ages, geometry and regional patterns of mafic dyke swarm emplacement, and matching Archean geology in these cratons as reconstruction pins to constrain the configuration of the 2.2 Ga supercraton Sclavia.