Chemical variations and significance of phosphates from the Fregeneda-Almendra pegmatite field, Central Iberian Zone (Spain and Portugal) |
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| Authors: | Encarnación Roda-Robles Romeu Vieira Alfonso Pesquera Alexandre Lima |
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| Institution: | 1. Dpto. Mineralogia y Petrologia, Universidad del Pais Vasco/EHU, Apdo. 644, 48080, Bilbao, Spain
2. Geology Center, Porto University, Rua do Campo Alegre, 687, 4169-007, Porto, Portugal
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| Abstract: | Granitic pegmatites are widespread within a schist-metagreywacke complex in the Fregeneda-Almendra area (Central Iberian Zone). They intrude pre-Ordovician metasedimentary rocks and show a zonal distribution relative to the Meda-Penedono-Lumbrales granitic complex, from barren bodies to those enriched in Li, F, Sn, Nb>Ta, P and Be. Based on mineralogical criteria, these pegmatites are classified into three main categories: barren, intermediate and rare-element pegmatites, with each type including various subtypes. Phosphates are present in many pegmatites that usually occur as fine-grained accessory minerals. The most complex association of such minerals includes numerous Fe–Mn phosphates that occur in intermediate pegmatites. Al-phosphates are characteristic of Li-rich pegmatites. Electron microprobe analyses of representative phosphates reflect compositional differences depending on the pegmatite type. The Fe/(Fe+Mn) ratio of phosphates tends to decrease as the evolution degree of the pegmatites increases. |
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