Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Source composition and melting temperatures of orogenic granitoids; constraints from CaO/Na (sub 2) O, Al (sub 2) O (sub 3) /TiO (sub 2) and accessory mineral saturation thermometry

Stefan Jung and Joerg Albert Pfaender
Source composition and melting temperatures of orogenic granitoids; constraints from CaO/Na (sub 2) O, Al (sub 2) O (sub 3) /TiO (sub 2) and accessory mineral saturation thermometry
European Journal of Mineralogy (December 2007) 19 (6): 859-870

Abstract

Granitoid melts, generated experimentally from various materials by fluid-absent melting, show characteristic major-element compositions that can be used to infer source characteristics and melting temperatures. CaO/Na (sub 2) O ratios distinguish between pelite-derived melts (CaO/Na (sub 2) O<0.5) and melts derived from greywackes or igneous sources (CaO/Na (sub 2) O: 0.3-1.5). Distinctly more mafic melts (granodiorites and quartz diorites) generated by fluid-absent melting of amphibolite can show even higher CaO/Na (sub 2) O ratios, up to 10, although the majority of the melts have CaO/Na (sub 2) O ratios between 0.1 and 3. Al (sub 2) O (sub 3) /TiO (sub 2) ratios reflect the melting temperature, and mathematical formulations are presented that allow using this ratio as a geothermometer for given source compositions. A comparison of temperatures from melting experiments with corresponding Al (sub 2) O (sub 3) /TiO (sub 2) values indicate a reasonably good correlation (r (super 2) : 0.70-0.91), demonstrating the usefulness of temperature estimates in granitoid rocks based on Al (sub 2) O (sub 3) /TiO (sub 2) systematics. Application to well investigated S-type and A-type granites and quartz diorites from the Damara Belt (Namibia) shows different CaO/Na (sub 2) O and Al (sub 2) O (sub 3) /TiO (sub 2) ratios for all rock types, supporting their origin from different sources at different temperatures. For the quartz diorites, temperature estimates derived from Al (sub 2) O (sub 3) /TiO (sub 2) ratios, and those derived from apatite solubility in mafic rocks, agree within + or -20 degrees C. On the other hand, temperature estimates for A-type and S-type granites derived from Al (sub 2) O (sub 3) /TiO (sub 2) ratios are systematically higher by 50-150 degrees C compared with those from accessory mineral saturation, suggesting disequilibrium during partial melting of the lower crust.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 19
Serial Issue: 6
Title: Source composition and melting temperatures of orogenic granitoids; constraints from CaO/Na (sub 2) O, Al (sub 2) O (sub 3) /TiO (sub 2) and accessory mineral saturation thermometry
Affiliation: Philipps-Universitaet Marburg, Fachbereich Geowissenschaften, Marburg, Federal Republic of Germany
Pages: 859-870
Published: 200712
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 63
Accession Number: 2008-028872
Categories: Igneous and metamorphic petrologyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: Technische Universitat Bergakademie Freiberg, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200809
Close Modal

or Create an Account

Close Modal
Close Modal