Cambrian-early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France:Continental break-up and rifting of the northern Gondwana margin  

作　　者：Andre Pouclet J.Javier Alvaro Jacques-Marie Bardintzeff Andres Gil Imaz Eric Monceret Daniel Vizcaino 

机构地区：[1]3 rue des Foulques,85560 Longeville-sur-mer,France [2]lnstituto de Geociencias(CSIC--UCM),c/fose Antonio Novais 12,28040 Madrid,Spain [3]Volcanology and Planetology,UMR CNRS 8148 GEOPS,University of Paris-Saclay,91405 Orsay,France [4]Departamento Ciencias de la Tierra,Universidad de Zaragoza,50009 Zaragoza,Spain [5]18 rue des Fins,11570 Cazilhac,France [6]7 Jean-Baptiste Chardin,Maquens,11090 Carcassonne,France

出　　处：《Geoscience Frontiers》2017年第1期25-64,共40页地学前缘（英文版）

基　　金：funded by project CGL2013-48877-P from Spanish MINECO

摘　　要：The Cambrian-lower Ordovician volcanic units of the South Armorican and Occitan domains are ana- lysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Camhrian-Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases： （I） basal Cambrian rhyolites, （2） upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, （3） upper lower-middle Cambrian continental tholeiites, （4） Tremadocian rhyolites, and （5） upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic conti- nental rift is termed the ＂Tremadocian Tectonic Belt＂ underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that fore- casted the South Armorican-Medio-European Ocean as a part of the Palaeotethys Ocean.The Cambrian-lower Ordovician volcanic units of the South Armorican and Occitan domains are ana- lysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Camhrian-Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases： （I） basal Cambrian rhyolites, （2） upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, （3） upper lower-middle Cambrian continental tholeiites, （4） Tremadocian rhyolites, and （5） upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic conti- nental rift is termed the ＂Tremadocian Tectonic Belt＂ underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that fore- casted the South Armorican-Medio-European Ocean as a part of the Palaeotethys Ocean.

关 键 词：Gondwana margin Cambro-Ordovician volcanic activity Continental tholeiite Rheic Ocean Middle-European Ocean Palaeotethys Ocean 

分 类 号：P542[天文地球—构造地质学]