Original paper

Trace element content and partitioning between biotite and muscovite of granitic rocks: a study in the Viseu region (Central Portugal)

Neves, Luis J.P.F.

European Journal of Mineralogy Volume 9 Number 4 (1997), p. 849 - 858

27 references

published: Jul 23, 1997
manuscript accepted: Feb 4, 1997
manuscript received: Mar 20, 1996

DOI: 10.1127/ejm/9/4/0849

BibTeX file

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Abstract

Abstract Trace element content has been estimated for biotite and muscovite of hercynian porphyritic biotite granites and two-mica granites of Central Portugal. In the two-mica granites, biotite and muscovite together account for more than 80 % of Li, V, Cr, Zn, Nb, Sn and W, as well as significant proportions (30-75 %) of F, Cl, Co, Ga, Rb, Y, Cs and Ta. Sn and W are highly concentrated in the white mica (83 %), providing an important source for ore genesis when muscovite undergoes breakdown reactions. In the porphyritic biotite granites, biotite alone accounts for more than 75 % of Li, V, Zn, Nb and W, and between 30 to 75 % of F, Cl, Cr, Ga, Rb, Y, Sn, Cs and Nd. As expected, muscovite and biotite usually host small proportions (< 30 %) of Cu, Sr, Zr, Ba, La, Ce, Nd, Hf, Pb, Th and U, which confirms the preference of these elements for feldspars and accessory minerals in granitoid rocks. Trace element partitioning between biotite and muscovite of the two-mica granites has been evaluated, and average partition ratios (DBt/Ms ± 1σ) are as follows: Zn (8.6 ± 2.5), Ni (8.4 ± 4.4), Co (5.2 ± 2.0), Cs (4.3 ± 1.3), Li (4.0 ± 2.1), Cr (3.6 ± 1.3), Nb (2.8 ±0.6), Ta (2.5 ± 1.2), V (2.2 ±0.4), F(1.8 ± 0.5), Rb (1.6 ± 0.3), Cl (1.4 ± 1.5), Pb (1.2 ± 0.5), Sr (0.7 ± 0.4), Sc (0.6 ± 0.6), Ba (0.6 ± 0.2), Ga (0.6 ±0.1), Sn (0.4 ± 0.1) and W (0.4 ±0.1).

Keywords

trace elementpartitioningbiotitemuscoviteHercynian granites