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标题：Proto-Adamastor ocean crust (920 Ma) described in Brasiliano Orogen from coetaneous zircon and tourmaline
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作者：Léo A. Hartmann ; Mariana Werle ; Cassiana R.L. Michelin 等
期刊名称：Geoscience Frontiers
印刷版ISSN：1674-9871
出版年度：2019
卷号：10
期号：4
页码：1623-1633
DOI：10.1016/j.gsf.2018.09.018
语种：English
出版社：Elsevier
摘要：AbstractProto-Adamastor ocean bathed Rodinia and successor continental fragments from 1.0–0.9 Ga up to 0.75 Ga, and evolved into world Adamastor Ocean at 0.75–0.60 Ga. Mesoproterozoic oceanic crust is poorly preserved on continents, only indirect evidence registered in Brasiliano Orogen. We report first evidence of ophiolite originated in proto-Adamastor. We use multi-technique U-Pb-Hf zircon andδ11B tourmaline isotopic and elemental compositions. The host tourmalinite is enclosed in metaserpentinite, both belonging to the Bossoroca ophiolite. Zircon is 920 Ma-old,ɛHf(920 Ma) = +12, HfTDM = 1.0 Ga and has ‘oceanic’ composition (e.g., U/Yb < 0.1). Tourmaline is dravite withδ11B = +1.8‰ (Tur 1), 0‰ (Tur 2), −8.5‰ (Tur 3). These characteristics are a novel contribution to Rodinia and associated world ocean, because a fragment of proto-Adamastor oceanic crust and mantle evolved at the beginning of the Brasiliano Orogen.Graphical abstractDisplay OmittedHighlights•Initial rifting of Rodinia described in Brasiliano Orogen.•Coetaneous zircon and tourmaline.•U-Pb zircon age is 920.4 ± 9.8 Ma,ɛHf(920) = +12 and elements are ‘oceanic’.•Dravite hasδ11B = +1.8, 0, −8.5 in Tur1, Tur 2, Tur3.
关键词：KeywordsenCoeval zircon and tourmalineBossoroca ophioliteEarly Brasiliano OrogenZircon U-Pb-Hf isotopesZircon trace elementsTourmaline boron isotopes