The Lusinde late-post-tectonic Variscan granite (Central Iberian Zone): pluton emplacement at the termination of the Juzbado-Penalva do Castelo shear zone

被引:0
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作者
Portela, Luis [1 ]
Azevedo, Maria Rosario [1 ]
Medina, Jorge [1 ]
Aguado, Beatriz Valle [1 ]
机构
[1] Univ Aveiro, Dept Geociencias, GeoBioTec UID GEO 2020 04035, Campus Santiago, P-3810193 Aveiro, Portugal
关键词
Late-post-collisional Variscan granites; Anisotropy of magnetic susceptibility; Central Iberian Zone; LA-ICP-MS U-Pb zircon ages; Pluton emplacement; Shear zones; Granitos Variscos tardi-tect & oacute; nicos; Anisotrop & iacute; a de susceptibilidad magn & eacute; tica; Zona Centroib & eacute; rica; Geocronolog & iacute; a U-Pb en circon por LA-ICP-MS; Emplazamiento del plut & oacute; n; Zonas de Cizalla; U-PB GEOCHRONOLOGY; ICP-MS ZIRCON; MAGNETIC-SUSCEPTIBILITY; MONAZITE GEOCHRONOLOGY; HERCYNIAN GRANITOIDS; CRUSTAL SOURCES; MASSIF; CONSTRAINTS; COMPLEX; BELT;
D O I
10.1007/s41513-024-00259-5
中图分类号
P5 [地质学];
学科分类号
0709 ; 081803 ;
摘要
The Lusinde biotite granite occurs in central-northern Portugal as a small Variscan intrusion with an elongated NE-SW shape. The main objective of this work is to explore the relationships between the Lusinde granite and the large late-post-tectonic Viseu batholith and constrain the mechanisms responsible for pluton emplacement. New LA-ICP-MS U-Pb zircon geochronological data for this intrusion yielded an emplacement age of 295 +/- 1 Ma, concordant within error with the ages reported for the different intrusive units of the Viseu batholith (299-296 Ma). The Lusinde granite shows relatively low values of magnetic susceptibility (Km = 152 x 10-6 to 271 x 10-6 SI), typical of granites of the ilmenite series in which biotite is the main carrier of magnetic signal. A pyroxene- and amphibole-bearing mafic microgranular enclave exhibits higher Km magnitudes (536 x 10-6 SI). Magnetic foliations are steep and strike subparallel to the pluton margins. Magnetic lineations show rather variable directions and steep plunges, suggesting that the whole massif may correspond to a feeder zone. The studied pluton seems to belong to an E-W band of steep lineations traced along the northern border of the main mass of the Cota-Viseu late-post-tectonic granite and associated mafic and intermediate rocks, which has been interpreted as an alignment of feeder zones related to the extensional termination of the Juzbado-Penalva do Castelo Shear Zone (JPCSZ). As a result, it is concluded here that the emplacement of the Lusinde granite was tectonically controlled by the JPCSZ. El granito biot & iacute;tico de Lusinde es una peque & ntilde;a intrusi & oacute;n con forma alargada NE-SW y edad Varisca que aflora en el centro-norte de Portugal. El principal objetivo de este trabajo es analizar las relaciones entre el granito de Lusinde y el gran batolito tardi-tect & oacute;nico de Viseu, as & iacute; como establecer los mecanismos de emplazamiento del plut & oacute;n. Los nuevos datos geocronol & oacute;gicos en circones (U-Pb LA-ICP-MS) para esta intrusi & oacute;n proporcionaron una edad de emplazamiento de 295 +/- 1 Ma, coherente, dentro del margen de error, con las edades reportadas para las diferentes unidades intrusivas del batolito de Viseu (299-296 Ma). El granito de Lusinde muestra valores relativamente bajos de susceptibilidad magn & eacute;tica (Km = 152 x 10-6 a 271 x 10-6 SI), t & iacute;picos de los granitos de la serie de la ilmenita en los cuales la biotita es la principal portadora de la se & ntilde;al magn & eacute;tica. Un enclave microgranular m & aacute;fico, portador de piroxeno y anf & iacute;bol, exhibe magnitudes de Km m & aacute;s elevadas (536 x 10-6 SI). Las foliaciones magn & eacute;ticas tienen buzamientos elevados con un rumbo sub-paralelo a los m & aacute;rgenes del plut & oacute;n. Las lineaciones magn & eacute;ticas muestran direcciones bastante variables y inclinaciones pronunciadas, lo que sugiere que la zona de alimentaci & oacute;n ocupa la totalidad del macizo. El plut & oacute;n estudiado se localiza en una banda E-W donde las lineaciones magn & eacute;ticas sub-verticales del borde norte del batolito de Viseu han sido interpretadas como debidas al control tect & oacute;nico ejercido por la Zona de Cizalla Juzbado-Penalva do Castelo (JPCSZ) durante el emplazamiento del magma gran & iacute;tico. De este modo, se concluye aqu & iacute; que la JPCSZ tambi & eacute;n ejerci & oacute; un fuerte control tect & oacute;nico en la instalaci & oacute;n del granito de Lusinde.
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页数:18
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