MAGNETITE AND ILMENITE GRANITES IN THE LAMAS DE OLO PLUTON (NORTH PORTUGAL): PETROPHYSIC AND METALLOGENIC IMPLICATIONS

• Type: Article in International Conference Proceedings Book
• Date: 2016

Authors

Cruz, C (Author) Other; Sant'Ovaia, H (Author) FCUP; Noronha, F (Author) FCUP

Conference proceedings International

Title: 16TH INTERNATIONAL MULTIDISCIPLINARY SCIENTIFIC GEOCONFERENCE, SGEM 2016: SCIENCE AND TECHNOLOGIES IN GEOLOGY, EXPLORATION AND MINING, VOL I

Pages: 345-352

16th International Multidisciplinary Scientific Geoconference (SGEM 2016)

Albena, BULGARIA, JUN 30-JUL 06, 2016

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ISI Web of Knowledge - 0 Citations

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Authenticus ID: P-00M-FXN

Abstract (EN): In the studied area, situated in Northern Portugal, outcrops, an intrusion of post-tectonic Variscan granites constituting the Lamas de Olo Pluton (LOP) whose emplacement was controlled by NNE-SSW regional Variscan fault, the Verin-Regua-Penacova fault (VRPF). The LOP has distinct biotite granite facies: 1) Lamas de Olo (LO) - a porphyritic, medium to coarse-grained; 2) Barragem (BA) - a leucocratic slightly porphyritic, fine-grained; 3) Alto dos Cabecos (AC) - a porphyritic, medium to fine-grained. The LOP granites intrudes the Douro Group metasediments (Precambrian to Cambrian in age) and syntectonic two-mica granites from Vila Real Massif. The LOP occurs in the "Iberian Sn-W metallogenic province" and in the area exist W (Mo) occurrences. The LOP granites present as primary accessory minerals biotite, apatite, zircon, sphene, allanite, magnetite and/or hematite, ilmenite, fluorite and tourmaline. As secondary minerals, contains muscovite, chlorite, epidote and rutile. The magnetic susceptibility (Kin) measurements were taken on 151 oriented cores (26 sampling sites) roughly distributed in the LOP. The Km values range between 11 and 92100 x 10(-6) SI in LO facies, pointing out a manly ferromagnetic behavior, due to magnetite, between 22 and 51 x 10(-6) SI in BA facies and 135 and 905 x 10(-6) SI in AC facies, indicating a paramagnetic behavior, due to ilmenite and biotite. Our results show the presence of ilmenite and magnetite granites in the same pluton. The association between granites with different magnetic behavior in the same pluton is not present in other similar post-tectonic plutons such as Vila Pouca de Aguiar and Aguas Frias-Chaves, also emplaced along VRPF, which are ilmenite granites. The presence of magnetite in LOP reflects melt oxidized conditions, which usually played and important role on the genesis of W (Mo) mineralizations. This relationship between magnetite-type granites and W (Mo) mineralizations was also found in the post-tectonic Geres pluton.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8