Skip to Main Content
Book Chapter

Recent volcanic history of Irazú volcano, Costa Rica: Alternation and mixing of two magma batches, and pervasive mixing

By
Guillermo E. Alvarado
Guillermo E. Alvarado
1
Área de Amenazas y Auscultación Sísmica y Volcánica, Instituto Costarricense de Electricidad, Apdo. 10032-1000, Costa Rica
Search for other works by this author on:
Michael J. Carr
Michael J. Carr
2
Department of Geological Sciences, Rutgers University, New Brunswick, New Jersey 08903, USA
Search for other works by this author on:
Brent D. Turrin
Brent D. Turrin
2
Department of Geological Sciences, Rutgers University, New Brunswick, New Jersey 08903, USA
Search for other works by this author on:
Carl C. Swisher, III
Carl C. Swisher, III
2
Department of Geological Sciences, Rutgers University, New Brunswick, New Jersey 08903, USA
Search for other works by this author on:
Hans-Ulrich Schmincke
Hans-Ulrich Schmincke
3
Leibniz Institute for Marine Science, IfM-GEOMAR (Leibniz Institute for Marine Sciences), Wischhofstr. 1-3, D-24148 Kiel, Germany
Search for other works by this author on:
Kenneth W. Hudnut
Kenneth W. Hudnut
4
U.S. Geological Survey, 525 South Wilson Ave., Pasadena, California 91106-3212, USA
Search for other works by this author on:
Published:
January 01, 2006

40Ar/39Ar dates, field observations, and geochemical data are reported for Irazú volcano, Costa Rica. Volcanism dates back to at least 854 ka, but has been episodic with lava shield construction peaks at ca. 570 ka and 136–0 ka. The recent volcanic record on Irazú volcano comprises lava flows and a variety of Strombolian and phreatomagmatic deposits, with a long-term trend toward more hydrovolcanic deposits. Banded scorias and hybridized rocks reflect ubiquitous magma mixing and commingling. Two distinct magma batches have been identified. One magma type or batch, Haya, includes basalt with higher high field strength (HFS) and rare-earth element contents, suggesting a lower degree melt of a subduction modified mantle source. The second batch, Sapper, has greater enrichment of large ion lithophile elements (LILE) relative to HFS elements and rare-earth elements, suggesting a higher subduction signature. The recent volcanic history at Irazú records two and one half sequences of the following pattern: eruptions of the Haya batch; eruptions of the Sapper batch; and finally, an unusually clear unconformity, indicating a pause in eruptions. In the last two sequences, strongly hybridized magma erupted after the eruption of the Haya batch. The continuing presence of two distinct magma batches requires two active magma chambers. The common occurrence of hybrids is evidence for a small, nearer to the surface chamber for mixing the two batches. Estimated pre-eruptive temperatures based on two-pyroxene geothermometry range from ∼1000–1176 °C in basalts to 922 °C in hornblende andesites. Crystallization occurred mainly between 4.6 and 3 kb as measured by different geobarometers. Hybridized rocks show intermediate pressures and temperatures. High silica magma occurs in very small volumes as banded scorias but not as lava flows. Although eruptions at Irazú are not often very explosive, the pervasiveness of magma mixing presents the danger of larger, more explosive hybrid eruptions.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Volcanic Hazards in Central America

William I. Rose
William I. Rose
Search for other works by this author on:
Gregg J.S. Bluth
Gregg J.S. Bluth
Search for other works by this author on:
Michael J. Carr
Michael J. Carr
Search for other works by this author on:
John W. Ewert
John W. Ewert
Search for other works by this author on:
Lina C. Patino
Lina C. Patino
Search for other works by this author on:
James W. Vallance
James W. Vallance
Search for other works by this author on:
Geological Society of America
Volume
412
ISBN print:
9780813724126
Publication date:
January 01, 2006

References

Related

Citing Books via

Related Articles
Related Book Content
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal