澳大利亚南部俯冲岩石中保存的劳伦西亚西部变质足迹

IF 3.5 2区 地球科学 Q1 GEOLOGY
Dillon A. Brown, Laura J. Morrissey, Martin Hand, Jacob A. Mulder, Benjamin Wade, Vitor Barrote
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引用次数: 0

摘要

澳大利亚南部塔斯马尼亚岛中西部的多变质玄武岩含有在寒武纪俯冲过程中形成的高压矿物组合,以及已公布卢-铪年龄约为1285-1240Ma的孑遗石榴石。这些石榴石年龄与塔斯马尼亚西部和北美西部已公布的碎屑锆石数据一起,被用来推测塔斯马尼亚西部存在中新生代劳伦地壳。在这项研究中,我们将锆石岩石年代学与来自孑遗石榴石中包涵体组合的成分信息相结合,从俯冲叠压岩中提取了中新生代压力-温度数据,这些岩石有效地构成了目前居住在塔斯马尼亚中西部的劳伦地壳残余。新数据表明,中新生代变质作用分为两个阶段。第一个阶段由约 1480-1235 Ma 的锆石记录,该锆石形成于无石榴石、有斜长石的高热梯度环境中,压力不超过 ~5-5.5 kbar。由约 1285-1240 Ma孑遗石榴石记录的第二个事件的特征是,在 ~8.5 kbar 和 ~590-680°C 的温度下,形成了中等压力的褐铁矿-斜长石-含生物的矿物组合。这些压力-温度制约因素归因于与北美隐秘的东库特内造山作用相关的深盆地系统内的延伸,该造山作用与约 1450-1370 Ma 上带-普塞尔盆地沉积作用的最后阶段相吻合。考虑到本研究中来自塔斯马尼亚中西部的新的碎屑锆石 U-Pb-Hf 同位素数据以及来自整个塔斯马尼亚西部和贝尔特-普塞尔盆地的现有锆石出处数据,我们的研究结果加强了劳伦伦足迹的假设,该足迹可能包括塔斯马尼亚西部的大部分地区,并与努纳构造和罗迪尼亚构造有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

The metamorphic footprint of western Laurentia preserved in subducted rocks from southern Australia

The metamorphic footprint of western Laurentia preserved in subducted rocks from southern Australia

Polymetamorphic metapelitic rocks in central-west Tasmania, southern Australia, contain high-pressure mineral assemblages that formed during Cambrian-aged subduction and relict garnet with published Lu–Hf ages of c. 1285–1240 Ma. These garnet ages, along with published detrital zircon data from throughout western Tasmania and western North America, have been used to propose the presence of Mesoproterozoic Laurentian crust in western Tasmania. In this study, we combine zircon petrochronology with compositional information from the inclusion assemblages in relict garnet to extract Mesoproterozoic pressure–temperature data from subduction-overprinted rocks, which effectively constitute an interpreted remnant of Laurentian crust now residing in central-west Tasmania. The new data suggest Mesoproterozoic metamorphism involved two stages. The first event is recorded by c. 1480–1235 Ma zircon that formed in a garnet-absent, plagioclase-present, high-thermal gradient environment at pressures no greater than ~5–5.5 kbar. The second event recorded by c. 1285–1240 Ma relict garnet was characterized by the development of a moderate-pressure kyanite–plagioclase–biotite-bearing mineral assemblage, which formed at ~8.5 kbar and ~590–680°C. These pressure–temperature constraints are attributed to extension within a deep basin system associated with the cryptic East Kootenay Orogeny in North America, which coincides with the final stages of c. 1450–1370 Ma upper Belt-Purcell Basin sedimentation. Taking into account new detrital zircon U–Pb–Hf isotopic data from central-west Tasmania in this study and existing zircon provenance data from throughout western Tasmania and the Belt-Purcell Basin, our results strengthen the hypothesis of a Laurentian footprint that potentially encompasses much of western Tasmania and relates to both Nuna and Rodinian tectonism.

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来源期刊
CiteScore
6.60
自引率
11.80%
发文量
57
审稿时长
6-12 weeks
期刊介绍: The journal, which is published nine times a year, encompasses the entire range of metamorphic studies, from the scale of the individual crystal to that of lithospheric plates, including regional studies of metamorphic terranes, modelling of metamorphic processes, microstructural and deformation studies in relation to metamorphism, geochronology and geochemistry in metamorphic systems, the experimental study of metamorphic reactions, properties of metamorphic minerals and rocks and the economic aspects of metamorphic terranes.
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