Geology and mineralogy of Li mineralization in the Central Iberian Zone (Spain and Portugal)

E Roda-Robles,J Torres-Ruiz,P P Gil-Crespo,A Lima,I Garate-Olave,R Vieira,A Pesquera,T Martins

doi:10.1180/minmag.2016.080.049

Abstract

AbstractLithium mineralization is common in the Central Iberian Zone and, to a lesser extent, in the Galizia-Trás-OsMontes Zone of Spain and Portugal, occurring along a ∼500 km-long NNW-SSE striking belt. There are different styles of Li mineralization along this belt; they are mainly associated with aplite-pegmatite bodies and, to a much lesser extent, with veins of quartz and phosphate. Lithium mineralization in the Central Iberian Zone may be classified into four types: aplite-pegmatite dykes occurring in pegmatitic fields, Li mineralization associated with leucogranitic cupolas, beryl-phosphate pegmatites and quartz-montebrasite veins. The main Li minerals of these bodies include Li-mica, spodumene and/or petalite in the pegmatitic fields and leucogranitic cupolas; triphylite–lithiophilite in the beryl-phosphate pegmatites, and amblygonite–montebrasite in the quartz-montebrasite veins. The origin of these different styles of mineralization is considered to be related to differentiation of peraluminous melts, which were generated by partial melting of metasedimentary rocks during the Variscan orogeny. On the basis of paragenesis and chemical composition, the pegmatitic fields and Li mineralization associated with granitic cupolas record the highest fractionation levels, whereas the beryl-phosphate pegmatites and quartz-montebrasite veins show lower degrees of fractionation. There are a number of textural and mineralogical indicators for Li exploration in the Central Iberian Zone and in the Galizia-Trás-Os-Montes Zone, with the highest economic potential for Li being in the pegmatite fields.

Highlights

LITHIUM is a relatively rare element in the Earths crust
In the Li mineralization associated with leucogranitic cupolas and in pegmatite fields, F/OH ratios are rather higher and the F content of amblygonite–montebrasite ranges from 0.43 to 5.33 wt.% and from 0.55 to 7.33 wt.%, respectively (Fig. 5a, Table 5)
The F median values are quite similar for the pegmatite fields, quartz veins and Li mineralization associated with leucogranitic cupolas (1.84, 1.69 and 1.77 wt.% respectively), whereas those of the samples from beryl-phosphate pegmatites are clearly lower (0.68 wt.%)

Summary

Introduction

LITHIUM is a relatively rare element in the Earths crust. Its uses and, its price, have increased considerably during the last decade. In addition to pegmatites sensu stricto, other Li-enriched dyke-like bodies related to granitic rocks, are observed in the Central Iberian Zone, both in Spain and Portugal. These are very rich in quartz and amblygonite–montebrasite, and are considered as hydrothermal veins. Lithium-rich mineralization in the Iberian Massif is located mainly in the Central Iberian Zone and, in a lesser extent, in the Galizia-Trás-Os-Montes Zone to the north-west (Fig. 1).

12 Puentemocha

25 El Trasquilón

Eucr-L

Findings

Discussion