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Até onde irá o Terreno Finisterra? Proposta de correlação com os “Terrenos” variscos europeus
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Advisor(s)
Abstract(s)
Resumo: O Maciço Ibérico foi subdividido num conjunto de terrenos tectono-estratigráficos com características próprias, entre os quais os Terrenos
Finisterra (TF) e Ibérico (TI). O TF contacta com TI, nomeadamente com
a Zonas Centro Ibérica e Ossa-Morena, através de uma zona de cisalhamento, a Zona de Cisalhamento Porto-Tomar-Ferreira do Alentejo. O TF
apresenta características que contrastam com as que especializam o TI,
destacando-se: (1) um evento tectono-metamórfico de alta temperatura
Varisco, acompanhado de magmatismo granítico, de idade ante-mississipiana;
(2) a presença de unidades de baixo grau metamórfico discordantes, sendo
que a Unidade de Albergaria (Devónico superior), apresenta uma natureza
marinha, que contrasta com o gap na sedimentação da mesma idade no TI;
e (3) a existência de zircões detríticos de idade mesoproterozóica em alguns
litótipos, o que não é característico dos terrenos Peri-Gondwânicos. As
características do TF permitem a sua correlação com o Bloco de León e o
Mid-German Crystalline Rise.
Abstract: The Iberian Massif was divided into several tectono-stratigraphic terranes with its own features, among them the Finisterra Terrane. This Terrane connects with the Iberian one, namely with the Central Iberian and Ossa-Morena Zones, through a lithospheric shear zone, the Porto-TomarFerreira do Alentejo Shear Zone. Several Finisterra Terrane features contrast with those that characterize the Iberian Terrane, namely: (1)Apre-Mississipian high-temperature Variscan tectono-metamorphic event, accompanied by granitic magmatism; (2) The presence of an Upper Devonian marine unit (Albergaria Unit) with very low-grade metamorphism and acritarch assemblages similar to those described in Laurussia, which contrasts with the Upper Devonian gap of sedimentation in the Iberian Terrane. This unit is imbricated in theArada Unit, attributed to Neoproterozoic. So, if these ages are considered, a Cambrian-Devonian unconformity seemsto be emphasized; and (3) The existence of Mesoproterozoic detrital zircons in some of the tectonostratigraphic units, which is not characteristic of Peri-Gondwanan terranes where a Mesoproterozoic gap is a distinctive feature. The mentioned features ofthe FinisterraTerrane allow its correlation with some central Europe domains, namely the León Block and the Mid-German Crystalline Rise (MGCR). Although the magmatic and tectono-metamorphic similarities are clear, some particular features are present in each of these blocks (i.e. the presence of high pressure metamorphism in León Block and MGCR, which is not reported, until the present days, in Finisterra). So, it is proposed a new tectono-stratigraphic terrane (Finisterra Terrane-León-MGCR Terrane), which defines an arcuate pattern compatible with the Ibero-Armorican Arc. Since the Mississippian, the Finisterra-León-MGCR Terrane and the other Peri-Gondwana Terranes (that includes the Iberian Terrane) show similar metamorphic and magmatic events, suggesting a common evolution during Carboniferous, which is compatible with the beginning of the collision between the Gondwana and Laurentia blocks.
Abstract: The Iberian Massif was divided into several tectono-stratigraphic terranes with its own features, among them the Finisterra Terrane. This Terrane connects with the Iberian one, namely with the Central Iberian and Ossa-Morena Zones, through a lithospheric shear zone, the Porto-TomarFerreira do Alentejo Shear Zone. Several Finisterra Terrane features contrast with those that characterize the Iberian Terrane, namely: (1)Apre-Mississipian high-temperature Variscan tectono-metamorphic event, accompanied by granitic magmatism; (2) The presence of an Upper Devonian marine unit (Albergaria Unit) with very low-grade metamorphism and acritarch assemblages similar to those described in Laurussia, which contrasts with the Upper Devonian gap of sedimentation in the Iberian Terrane. This unit is imbricated in theArada Unit, attributed to Neoproterozoic. So, if these ages are considered, a Cambrian-Devonian unconformity seemsto be emphasized; and (3) The existence of Mesoproterozoic detrital zircons in some of the tectonostratigraphic units, which is not characteristic of Peri-Gondwanan terranes where a Mesoproterozoic gap is a distinctive feature. The mentioned features ofthe FinisterraTerrane allow its correlation with some central Europe domains, namely the León Block and the Mid-German Crystalline Rise (MGCR). Although the magmatic and tectono-metamorphic similarities are clear, some particular features are present in each of these blocks (i.e. the presence of high pressure metamorphism in León Block and MGCR, which is not reported, until the present days, in Finisterra). So, it is proposed a new tectono-stratigraphic terrane (Finisterra Terrane-León-MGCR Terrane), which defines an arcuate pattern compatible with the Ibero-Armorican Arc. Since the Mississippian, the Finisterra-León-MGCR Terrane and the other Peri-Gondwana Terranes (that includes the Iberian Terrane) show similar metamorphic and magmatic events, suggesting a common evolution during Carboniferous, which is compatible with the beginning of the collision between the Gondwana and Laurentia blocks.
Description
Keywords
Maciço Ibérico Terreno Finisterra Ciclo Varisco Paleogeografia Iberian Massif Finisterra Terrane Variscan Cycle Paleogeography
Citation
Moreira et al. 2020, ‘Até onde irá o terreno Finisterra? Proposta de correlação com os “terrenos” variscos europeus’, Comunicações Geológicas, vol. 107, nº 1 (especial), pp. 11-15.
Publisher
LNEG - Laboratório Nacional de Energia e Geologia