Unraveling the emplacement history of a Portuguese post-tectonic Variscan pluton using magnetic fabrics and gravimetry

• Type: Article in International Scientific Journal
• Date: 2021

Authors

Cruz, C (Author) Other; Sant'Ovaia, H (Author) FCUP; Raposo, MIB (Author) Other; Lourenco, JM (Author) Other; Almeida, F (Author) Other; Noronha, F (Author) FCUP

Journal

Title: Journal of Structural Geology

Vol. 153

ISSN: 0191-8141

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 6 Citations

Scopus - 6 Citations

Other information

Authenticus ID: P-00V-NYW

DOI: 10.1016/j.jsg.2021.104470

Abstract (EN): The Lamas de Olo pluton is a post-tectonic Variscan pluton located in northern Portugal. It is a composite pluton comprising three outcropping biotite granites, similar in mineralogical composition but with different textures and different biotite and magnetite contents: Lamas de Olo, Alto dos Cabecos, and Barragem. Two magnetic fabric techniques, anisotropy of magnetic susceptibility and anisotropy of anhysteretic remanent magnetization, were used to test the coaxiality of magnetite and biotite fabrics. Comparing both magnetic tensors, the fabric of magnetite and paramagnetic minerals was found to be coaxial. The magmas ascended passively through opening fractures and were controlled by the intersection of ENE-WSW, NNW-SSE and NNE-SSW fault systems. The gravimetric study shows that the Lamas de Olo is an asymmetric, wedge-shaped pluton with a thickness of ca. 2.5-3.5 km. The kinematic model points to the presence of a feeder zone following an ENE-WSW direction, with two roots for Lamas de Olo and Alto dos Cabecos granites. Regarding Barragem granite, several conduits were identified along an NNE-SSW fault system, subparallel to the Verin-Re ' gua-Penacova fault. Comparing the shape of three post-tectonic biotite plutons with same age and located along the same regional structure, the VerinRe ' gua-Penacova fault, we observed that the geometry is mainly conditioned by the nature of the host rocks and characteristics of the crustal structure. Wedge-shaped plutons are intruded into granites, and flat-shaped plutons are hosted in metasediments.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 22