Magmatic structures and kinematics emplacement of the Variscan granites from Central Portugal (Serra da Estrela and Castro Daire areas)

Sant'Ovaia, Helena; Olivier, Philippe; Ferreira, Narciso; Noronha, Fernando; LeBlanc, Denis R.

doi:10.1016/j.jsg.2010.09.003

Cited by 33 publications

(11 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The three categories of microstructures in this study are: (1) magmatic; (2) slight solid-state overprint; or (3) solid state. This classification follows from other studies in which microstructures have been used qualitatively to document the conditions of deformation (e.g., Paterson et al, 1989;Bouchez et al, 1990;Bouchez and Gleizes, 1995;Mamtani and Greiling, 2005;Benn, 2010;Sant'Ovaia et al, 2010). A detailed list of microstructural observations for all samples in this study is given in Byerly (2014).…”

Section: Microstructural Characterization and Classificationmentioning

confidence: 99%

“…In some cases, solid-state fabrics are used to infer synemplacement deformation, such as the deformation of a marginal facies of an intrusion by an internal facies (e.g., de Saint Blanquat et al, 2001). Solid-state fabrics superimposed on magmatic fabrics represent an overprinting of emplacement-level processes (e.g., Gleizes et al, 1998;Pignotta and Benn, 1999;Zak et al, 2007) or time-transgressive tectonic fabrics in a cooling pluton (e.g., Bouchez et al, 1990;Karlstrom et al, 1993;Aranguren et al, 1996;Mamtani and Greiling, 2005;Baxter et al, 2005;Henry et al, 2009;Majumder and Mamtani, 2009;Sant'Ovaia et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Internal fabrics of the Idaho batholith, USA

et al. 2016

View full text Add to dashboard Cite

The Idaho batholith of the North American Cordillera is a large and long-lived silicic intrusive center. We studied fabrics at the regional scale within the different intrusive suites of the Idaho batholith, using microstructural characterization, anisotropy of magnetic susceptibility measurements, and shape preferred orientation analyses. Each studied outcrop was collocated with existing U-Pb zircon geochronology and ongoing (U-Th)/He zircon thermochronology results. Three new 40 Ar/ 39 Ar biotite ages, collocated with the existing U-Pb zircon ages, constrain the cooling rates within the batholith. The presence of dominantly magmatic microstructures allows us to interpret the results relative to the U-Pb zircon ages and observe spatial and temporal patterns of fabric development. The early (pre-80 Ma) intrusive suites exhibit solid-state microstructures that show a consistent orientation only in the western part of the batholith. Fabrics in the 83-67 Ma Atlanta peraluminous suite are weak and inconsistent in orientation, despite emplacement during regional contraction. We hypothesize that the lack of consistently oriented fabrics in the Atlanta lobe results from either: (1) topographic effects that caused local extensional/neutral strain environments in the upper parts of a crustal plateau; or (2) emplacement in thin, horizontal magmatic sheets. In contrast, fabrics within the 66-53 Ma Bitterroot peraluminous suite are well developed and consistently oriented (NW-striking; NE-dipping), recording localized contraction during magmatism.

show abstract

Section: Microstructural Characterization and Classificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Internal fabrics of the Idaho batholith, USA

et al. 2016

View full text Add to dashboard Cite

show abstract

“…315-310 Ma by the development of 1 km-to 10 km-sized NW-SE to N-S upright F3 folds, with an S3 axialplane schistosity, and followed by dextral faulting (Diez-Fernandez et al, 2017;and references therein). Crustal melting and concomitant mantle-derived heat input were continued throughout D3 to D5, with the pervasive emplacement of syn-to post-kinematic granite plutons, in three pulses roughly coincident with the D3 to D5 events: syn-kinematic porphyritic biotite monzogranites and leucogranites (c. 315-310 Ma); late-kinematic D3 (c. 309-301 Ma) and post-kinematic (c. 295-287 Ma) biotite ± cordierite monzogranites and granodiorites, with ferroan-potassic sub-alkaline granites at c. 295-290 Ma (e.g., Dias et al, 1998;Mateus and Noronha, 2010;Sant'Ovaia et al, 2010;Fernandez-Suarez et al, 2011). Water-absent dehydration melting (biotite incongruent melting) produced cordierite-bearing diatexites in the cores of D2 migmatitic domes (Pereira-Gomez and Rodriguez-Alonso, 2000).…”

Section: Geology and Samplingmentioning

confidence: 97%

High pressure and temperatures during the early stages of tungsten deposition at Panasqueira revealed by fluid inclusions in topaz

Cathelineau

Boiron

Marignac

et al. 2020

Ore Geology Reviews

View full text Add to dashboard Cite

The Variscan vein-type Panasqueira W-Sn(Cu) deposit, one of the main tungsten deposits in Western Europe, has a long and complicated geological history. The first vein infillings, which consist of the quartz-wolframite association as well as the first generation of topaz, underwent significant deformation. As a consequence, most fluid inclusions of the earliest hydrothermal event are deformed and destroyed. Two preserved fluid inclusion assemblages are, however, found in the topaz overgrowth band and are dense aqueous-carbonic inclusions as well as dense CO2 dominated fluid inclusions. The P-T conditions of fluid trapping are constrained by using the intersection between isochores, as well as graphite-water equilibrium data and yield the following trapping conditions: 500 ± 20°C and 250 ± 20 MPa. These P-T conditions are incompatible with fluid unmixing. Fluid chemistry results from water-graphite equilibrium, probably in metapelites, at two distinct temperatures: around 450-500°C for the predominant aqueous-carbonic fluid, and higher temperatures of maximal 550°C for the CO2-rich fluid enriched in N2. These P-T estimates are consistent with deep crustal levels around 8-10 km depth and a high geothermal gradient around c. 60°C/km-1. The ascending non-magmatic fluids, enriched in volatiles, are essential in the ore genesis.The high thermal gradients may be related either to new magma pulse after the formation of the Panasqueira granite intrusion or to anomalous heat flux produced by the hot fluids ascending from migmatitic levels present at greater depth. This hypothesis necessitates to consider the role of a crustal weakness, which is attested both by the successive intrusions of several granitic magmas at the same place, and the presence of inherited quartz filled structures so-called Seixo-Bravo found only in the Panasqueira area.

show abstract

“…The geology of the Serra da Estrela is dominated by the occurrence of hercynitic granitic rocks, which intruded the pre-Cambrian and Cambrian metasediments that constitute the grauvachic schist complex [43]. These rocks have a varied mineralogical composition, from granodiorites to leucogranites [44]. The area under study is essentially made up of schist terrain and, to a lesser extent, fluvial sedimentary deposits.…”

Section: Geologymentioning

confidence: 99%

Fire as a Selection Agent for the Dissemination of Invasive Species: Case Study on the Evolution of Forest Coverage

et al. 2020

View full text Add to dashboard Cite

Climate change has enhanced the occurrence of rural fires, since changes in the hydrological cycle have led to the occurrence of increasingly long and frequent periods of drought. This recurrence of rural fires in Portugal, in turn, has led to the successive elimination of vast areas traditionally occupied by native species or species of economic interest, which are being successively replaced by new species with invasive behavior. Among these, Acacia dealbata stands out for its dispersion capacity and for the area it has already occupied. In the present work, which reviews the evolution of forest cover over the last 18,000 years in the Serra da Estrela Natural Park, we intend to demonstrate that fire acts as a species selection agent and that it enhances the development of heliophile and pyrophyte species. For this purpose, an area of the municipality of Seia was selected, more specifically Casal do Rei, where the development of Acacia dealbata forests is monitored. In the end, it was concluded that, in fact, by analyzing the ages of the specimens present in these populations, fire acts as a selection agent by freeing up the space previously occupied by other species, opening the way for the growth of heliophiles and pyrophytes invasive species while enhancing their germination.

show abstract

Magmatic structures and kinematics emplacement of the Variscan granites from Central Portugal (Serra da Estrela and Castro Daire areas)

Cited by 33 publications

References 24 publications

Internal fabrics of the Idaho batholith, USA

Internal fabrics of the Idaho batholith, USA

High pressure and temperatures during the early stages of tungsten deposition at Panasqueira revealed by fluid inclusions in topaz

Fire as a Selection Agent for the Dissemination of Invasive Species: Case Study on the Evolution of Forest Coverage

Contact Info

Product

Resources

About