Skip to Main Content
GEOREF RECORD

Occurrence, paragenesis and compositional evolution of tourmaline from the Tormes Dome area, central Iberian Zone, Spain

Encarnacion Roda-Robles, Alfonso Pesquera, Pedro Pablo Gil-Crespo and Jose Torres-Ruiz
Occurrence, paragenesis and compositional evolution of tourmaline from the Tormes Dome area, central Iberian Zone, Spain
The Canadian Mineralogist (February 2011) 49 (1): 207-224

Abstract

Tourmaline occurs in a variety of pegmatites, leucogranites, migmatites, metasedimentary rocks and quartz veins in the anatectic Variscan Tormes Dome (TD) in the central Iberian Zone, Spain. In general, these tourmalines belong to the alkali group and to the hydroxy subgroup. The ratios (super X) []/( (super X) []+Na) and Mg/(Fe+Mg) range from 0 to 0.6 and 0 to 0.7, respectively, where (super X) [] represents vacancies at the X site. Metasomatic tourmaline precipitated in the metasedimentary rocks reflects the composition of the host rocks. Elbaite is characteristic of the most evolved pegmatites. Except for the Li-rich tourmalines, where the substitution mechanisms LiAlR (super 2+) (sub -2) and (super X) [] (super Y) Al (sub 0.5) (super X) Na (sub -1) (super Y) Li (sub -0.5) account for most of the Li incorporation, the chemical variations in tourmaline from the TD can be described in terms of a combination of the FeMg (sub -1) , Al (super X) [] (NaR (super 2+) ) (sub -1) and AlO(R (super 2+) ,OH) (sub -1) exchange vectors, where R (super 2+) represents (Fe+Mg+Mn). The substitution AlO(R (super 2+) ,OH) (sub -1) becomes more important from leucogranites, through metasedimentary units, migmatites to metasomatized granite. In tourmaline associated with pegmatites, the influence of the proton-loss substitution increases with the degree of evolution of the pegmatites. Biotite occurring with tourmaline has (super VI) Al in the range of 0.26-0.75 cations apfu and Mg/(Mg+Fe) values of 0.1 to 0.4. These values correlate well with those of the associated tourmaline, the K (sub D) (super tur/bt) depending on the lithology. The F intercept values of biotite decreases in the order leucogranites, BP and IP, which is consistent with a normal evolutionary trend. Low Fe (super 3+) /Sigma Fe values in biotite and tourmaline from migmatites, leucogranites and pegmatites reflect conditions of low oxygen fugacity. In contrast, biotite from metasediments and metasomatized granites, in which zinnwaldite occurs, are presumed to have significant amounts of Fe (super 3+) , suggesting relatively oxidizing conditions.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 49
Serial Issue: 1
Title: Occurrence, paragenesis and compositional evolution of tourmaline from the Tormes Dome area, central Iberian Zone, Spain
Affiliation: Universidad del Pais Vasco, Departamento de Mineralogia y Petrologia, Bilbao, Spain
Pages: 207-224
Published: 201102
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 37
Accession Number: 2011-034963
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N41°00'00" - N41°30'00", W06°34'60" - W06°00'00"
Secondary Affiliation: Universidad de Granada, ESP, Spain
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201120
Close Modal

or Create an Account

Close Modal
Close Modal