The Uplift of Armorica and the Bretonian Movements of the Variscan Orogeny-New Insights From Detrital Zircons in the Early Carboniferous Terrigenous Rocks of the Laval Basin (Armorican Massif, France)

IF 2.9 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Wei Lin, Michel Faure, Lingtong Meng
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Abstract

In the French Armorican Massif, the Bretonian phase of the Variscan orogeny has been defined by the Late Devonian (Famennian-Frasnian) erosion gap, and the Early Carboniferous (Tournaisian) syntectonic terrigenous deposits of the l’Huisserie formation in the Laval basin in the Central-North Armorican Domain, ascribed to the Armorica microcontinent. This phase is coeval with vertical (epeirogenic) movements. In addition to Neo-, and Paleo-Proterozoic peaks, ascribed to the Cadomian and Icartian events, respectively, the detrital zircon age populations of the l’Huisserie formation reveal the existence of a 388–358 Ma magmatic event previously recognized by the ca 367–360 Ma dolerite dyke swarms exposed in the N. part of the Central-North Armorican Domain. The isotopic (εHf) signature of these grains documents a pre-orogenic Variscan mantle contribution for the mafic magmatism interpreted here as the indication of the south-directed subduction of the Le Conquet-Teplá ocean, that is, a branch of the Rheic ocean, below the Armorica microcontinent during the Bretonian phase. The intraplate opening of the Laval, Ménez-Bélair, and Châteaulin basins was coeval with this subduction. In the Laval area, the final closure of the basin, accommodated by north-directed folds-and-thrusts, took place after the Bashkirian (ca 320 Ma).

Abstract Image

Armorica隆升与Variscan造山带布列塔尼运动——法国拉瓦尔盆地早石炭世陆源岩碎屑锆石的新认识
在法国Armorica地块,Variscan造山运动的布列塔尼期被定义为晚泥盆世(法明世-弗拉斯世)侵蚀缺口,而早石炭世(tournaisserie)同构造陆源沉积在中-北Armorica域中的Laval盆地l 'Huisserie组,被归为Armorica微大陆。这一阶段与垂直(造陆)运动同时发生。l 'Huisserie组的碎屑锆石年龄种群显示,除了新元古代和古元古代的峰值分别归因于卡多米尼亚和伊卡蒂亚事件外,还存在388-358 Ma的岩浆事件,此前暴露在中-北北美洲n部分的367-360 Ma的白云岩岩脉群中。这些颗粒的同位素(εHf)特征证明了造山前瓦里斯坎地幔对基性岩浆活动的贡献,说明在布列塔尼期,Le征服-特普莱洋(Rheic ocean的一个分支)在Armorica微大陆之下向南俯冲。拉瓦尔盆地、msamuez - bsamuair盆地和ch teaulin盆地的板内张开与这次俯冲同时发生。在拉瓦尔地区,盆地的最终关闭是在巴什基良期(约320 Ma)之后,由向北的褶皱和逆冲构造所调节。
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来源期刊
Geochemistry Geophysics Geosystems
Geochemistry Geophysics Geosystems 地学-地球化学与地球物理
CiteScore
5.90
自引率
11.40%
发文量
252
审稿时长
1 months
期刊介绍: Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged. Areas of interest for this peer-reviewed journal include, but are not limited to: The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution Principles and applications of geochemical proxies to studies of Earth history The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.
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