Skip to Main Content
Book Chapter

A sustained felsic magmatic system: the Hercynian granitic batholith of the Spanish Central System

By
Carlos Villaseca
Carlos Villaseca
Search for other works by this author on:
Victor Herreros
Victor Herreros
Search for other works by this author on:
Published:
January 01, 2000

A batholith of around 10,000 km2 was formed during the Hercynian orogeny in the Spanish Central System (SCS). Geochronological data indicate concentrated magmatic activity during the period 325–284 Ma. This late-orogenic magmatism is essentially granitic with only minor associated basic rocks (< 2% in outcrop). The SCS is a remarkably homogeneous batholith showing a restricted range of geochemical granite types without any evolutionary pattern related to time. These peraluminous granites show a limited variation in Na2O/Ka2O) (0.60–0.95), K/Rb (140–240), (La/Yb)n (6–13), and Eu/Eu* (0.34–0.62) ratios. This constancy in chemical characteristics is also reflected in their isotopic signatures: most monzogranites have initial 87Sr/86Sr ratios in the range of 0.7073–0.71229, initial εNd values vary between −5.4 and −6.6 and δ18O values group in the restricted range of 8.9–9.6‰. The lack of significant differences among SCS granitoids, maintained during a long geological period, suggests constancy in the nature of their source regions and conditions of magma generation. (1) Limited range of crustal sources: an essentially magmatic recycling during Hercynian orogen is suggested. Mantle-derived components are very limited and restricted to a minor role in the origin of the batholith. Geochemical and isotopic features of SCS granitoids are compatible with felsic lower crustal sources. (2) Constraints in melt conditions: uniformity in residual mineral assemblages (feldspars and garnet are always present in the granulitic residua) combined with a lack of attainment of equilibrium conditions during accessory phase dissolution in the crustal melting process is suggested. Granitic melts never reach saturation in some trace elements (REE, Th, Y, Zr), restricting their chemical variability. (3) Homogenisation in magma chambers: long-lived magmatic systems whose successive pulses accumulate into large magma chambers have the opportunity to mingle, thus reducing source differences.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

The Fourth Hutton Symposium on the Origin of Granites and Related Rocks

Bernard Barbarin
Bernard Barbarin
Search for other works by this author on:
William Edryd Stephens
William Edryd Stephens
Search for other works by this author on:
Bernard Bonin
Bernard Bonin
Search for other works by this author on:
Jean-Luc Bouchez
Jean-Luc Bouchez
Search for other works by this author on:
David Barrie Clarke
David Barrie Clarke
Search for other works by this author on:
Michel Cuney
Michel Cuney
Search for other works by this author on:
Hervé Martin
Hervé Martin
Search for other works by this author on:
Geological Society of America
Volume
350
ISBN print:
9780813723501
Publication date:
January 01, 2000

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal