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DOI	10.1130/B35142.1
	U-Pb monazite ages of the Kabanga mafic-ultramafic intrusions and contact aureoles, central Africa: Geochronological and tectonic implications
	Zi J.-W.; Rasmussen B.; Muhling J.R.; Maier W.D.; Fletcher I.R.
发表日期	2019
ISSN	167606
起始页码	1857
结束页码	1870
卷号	131 期号:2021-11-12
英文摘要	Mafic-ultramafic rocks of the Kabanga-Musongati alignment in the East African nickel belt occur as Bushveld-type layered intrusions emplaced in metasedimentary sequences. The age of the mafic-ultramafic intrusions remains poorly constrained, though they are regarded to be part of ca. 1375 Ma bimodal magmatism dominated by voluminous S-type granites. In this study, we investigated igneous monazite and zircon from a differentiated layered intrusion and metamorphic monazite from the contact aureole. The monazite shows contrasting crystal morphology, chemical composition, and U-Pb ages. Monazite that formed by contact metamorphism in response to emplacement of mafic-ultramafic melts is characterized by extremely high Th and U and yielded a weighted mean 207Pb/206Pb age of 1402 ± 9 Ma, which is in agreement with dates from the igneous monazite and zircon. The ages indicate that the intrusion of ultramafic melts was substantially earlier (by ~25 m.y., 95% confidence) than the prevailing S-type granites, calling for a reappraisal of the previously suggested model of coeval, bimodal magmatism. Monazite in the metapelitic rocks also records two younger growth events at ca. 1375 Ma and ca. 990 Ma, coeval with metamorphism during emplacement of S-type granites and tin-bearing granites, respectively. In conjunction with available geologic evidence, we propose that the Kabanga-Musongati mafic-ultramafic intrusions likely heralded a structurally controlled thermal anomaly related to Nuna breakup, which culminated during the ca. 1375 Ma Kibaran event, manifested as extensive intracrustal melting in the adjoining Karagwe-Ankole belt, producing voluminous S-type granites. The Grenvillian-aged (ca. 990 Ma) tin-bearing granite and related Sn mineralization appear to be the far-field record of tectonothermal events associated with collision along the Irumide belt during Rodinia assembly. Since monazite is a ubiquitous trace phase in pelitic sedimentary rocks, in contact aureoles of mafic-ultramafic intrusions, and in regional metamorphic belts, our study highlights the potential of using metamorphic monazite to determine ages of mafic-ultramafic intrusions, and to reconstruct postemplacement metamorphic history of the host terranes. © 2019 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184929
作者单位	State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China; John de Laeter Centre, Curtin University, Kent Street, Bentley, WA 6102, Australia; School of Earth Sciences, The University of Western Australia, Stirling Highway, Perth, WA 6009, Australia; School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff, CF10 3AT, United Kingdom
推荐引用方式 GB/T 7714	Zi J.-W.,Rasmussen B.,Muhling J.R.,et al. U-Pb monazite ages of the Kabanga mafic-ultramafic intrusions and contact aureoles, central Africa: Geochronological and tectonic implications[J],2019,131(2021-11-12).
APA	Zi J.-W.,Rasmussen B.,Muhling J.R.,Maier W.D.,&Fletcher I.R..(2019).U-Pb monazite ages of the Kabanga mafic-ultramafic intrusions and contact aureoles, central Africa: Geochronological and tectonic implications.Bulletin of the Geological Society of America,131(2021-11-12).
MLA	Zi J.-W.,et al."U-Pb monazite ages of the Kabanga mafic-ultramafic intrusions and contact aureoles, central Africa: Geochronological and tectonic implications".Bulletin of the Geological Society of America 131.2021-11-12(2019).