4.2 Article

Magnetic susceptibility of Variscan granite-types of the Spanish Central System and the redox state of magma

Journal

GEOLOGICA ACTA
Volume 15, Issue 4, Pages 379-+

Publisher

UNIV BARCELONA
DOI: 10.1344/GeologicaActa2017.15.4.8

Keywords

Magnetic susceptibility; Granite type; Biotite chemistry; Oxygen fugacity

Categories

Funding

  1. Spanish MICINN [CGL2016-78796]
  2. [Santander-UCM PR26/16-20294]

Ask authors/readers for more resources

Magnetic susceptibility (MS) has been measured in Variscan granites from central Spain. They yield values in the order of 15 to 180 mu SI units for S-and I-type granites, indicating that both types belong to the ilmenite series. Only samples from magnetite-bearing leucogranites from the I-type La Pedriza massif show high MS values, in the order of 500-1400 mu SI, reflecting the presence of this ferromagnetic mineral. Mineral chemistry of magmatic Fe-rich minerals (mainly biotite) suggests similar oxidation values for both granite types. MS values change in highly fractionated granites accordingly either with the presence of rare new Fe-oxide phases (some I-type leucogranites) or with the marked modal amount decrease of Fe-rich minerals (I-and S-type leucogranites). The redox state in highly fractionated granite melts is mostly controlled by magmatic processes that modify redox conditions inherited from the source region. Thus, the occurrence of magnetite or ilmenite in granites is primarily controlled by the oxidation state of the source material but also by the differentiation degree of the granite melt. The presence of magnetite in some Variscan I-type leucogranites might be a consequence of crystal fractionation processes in a more limited mafic mineral assemblage than in S-type granite melts.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.2
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available