Compositional variation and 226Ra-230Th model ages of axial lavas from the southern Mid-Atlantic Ridge, 8°48′S

Haase K, Brandl P, Devey C, Hauff F, Melcher B, Garbe-Schönberg D, Kokfelt T, Paulick H (2016)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Geochemistry Geophysics Geosystems American Geophysical Union (AGU)

Publisher: American Geophysical Union (AGU)

Book Volume: 17

Pages Range: 199-218

Journal Issue: 1

DOI: 10.1002/2015GC006016

Abstract

We present geological observations and geochemical data for the youngest volcanic features on the slow spreading Mid-Atlantic Ridge at 8°48′S that shows seismic evidence for a thickened crust and excess magma formation. Young lava flows with high sonar reflectivity cover about 14 km in the axial rift and were probably erupted from two axial volcanic ridges each of about 3 km in length. Three different lava units occur along an about 11 km long portion of the ridge, and lavas from the northern axial volcanic ridge differ from those of the southern axial volcanic ridge and surrounding lava flows. Basalts from the axial rift flanks and from a pillow mound within the young flows are more incompatible element depleted than those from the young volcanic field. Lavas from this volcanic area have Ra-Th disequilibria model ages of 1000 and 4000 years whereas the older lavas from the rift flank and the pillow mound, but also some of the lava field, are older than 8000 years. Glasses from the northern and southern ends of the southern lava unit indicate up to 100°C cooler magma temperatures than in the center and increased assimilation of hydrothermally altered material. The compositional heterogeneity on a scale of 3 km suggests small magma batches rising vertically from the mantle to the surface without significant lateral flow and mixing. The observations on the 8°48′S lava field support the model of low-frequency eruptions from single ascending magma batches that has been developed for slow spreading ridges.

Authors with CRIS profile

Karsten Haase Lehrstuhl für Endogene Geodynamik Philipp Brandl Lehrstuhl für Endogene Geodynamik

Involved external institutions

GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel DE Germany (DE) Christian-Albrechts-Universität zu Kiel DE Germany (DE) Rheinische Friedrich-Wilhelms-Universität Bonn DE Germany (DE)

How to cite

APA:

Haase, K., Brandl, P., Devey, C., Hauff, F., Melcher, B., Garbe-Schönberg, D.,... Paulick, H. (2016). Compositional variation and 226Ra-230Th model ages of axial lavas from the southern Mid-Atlantic Ridge, 8°48′S. Geochemistry Geophysics Geosystems, 17(1), 199-218. https://dx.doi.org/10.1002/2015GC006016

MLA:

Haase, Karsten, et al. "Compositional variation and 226Ra-230Th model ages of axial lavas from the southern Mid-Atlantic Ridge, 8°48′S." Geochemistry Geophysics Geosystems 17.1 (2016): 199-218.

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