Formation of the Troodos Ophiolite at a triple junction: Evidence from trace elements in volcanic glass

Journal article
(Original article)


Publication Details

Author(s): Regelous M, Haase K, Freund S, Keith M, Weinzierl C, Beier C, Brandl P, Endres T, Schmidt H
Journal: Chemical Geology
Publisher: Elsevier
Publication year: 2014
Volume: 386
Pages range: 66-79
ISSN: 0009-2541
Language: English


Abstract


Fresh volcanic glasses from the extrusive section of the Troodos Ophiolite in Akaki Canyon are tholeiitic and basaltic to dacitic in composition. Compared to normal MORB they have extremely low fractionation corrected Na8, Fe8 and Ti8 and are enriched in fluid-mobile trace elements, including U, Ba, Rb, Sr and Pb, relative to non-fluid mobile elements of similar incompatibility. Trace element compositions of Akaki lavas define an array extending between ‘back-arc lava’-like compositions, and the field defined by Troodos boninites from the upper part of the lava sequence. Troodos lavas were derived from a mantle source that underwent early melt depletion, and later enrichment by both fluids and small degree melts. These processes can explain the unusual negative correlation of Pb/Ce with Zr/Nb and Ba/Nb in Troodos extrusives. Although some Troodos lavas are similar in composition to lavas from back-arc spreading centres, the boninites from the upper parts of the lava pile do not appear to have exact compositional equivalents among lavas from fore-arcs, back-arcs or other tectonic settings where similar rocktypes have been recovered. We suggest that the geochemical evolution inferred for the mantle source of Troodos lavas, together with geological evidence is most consistent with an origin for the Troodos Ophiolite at a spreading centre close to a ridge–trench–trench, or ridge–trench–transform triple junction, where highly depleted, subduction-modified, fluid-enriched mantle wedge material was able to upwell and decompress to shallow depths in a ‘fore-arc’ location. In such a tectonic setting, arc volcanism is captured by the spreading centre, explaining the lack of evidence for subaerial arc magmatism in Troodos. Rapid lateral migration of the triple junction could account for the similar ages of other Tethyan supra-subduction zone ophiolites.Fresh volcanic glasses from the extrusive section of the Troodos Ophiolite in Akaki Canyon are tholeiitic and basaltic to dacitic in composition. Compared to normal MORB they have extremely low fractionation corrected Na, Fe and Ti and are enriched in fluid-mobile trace elements, including U, Ba, Rb, Sr and Pb, relative to non-fluid mobile elements of similar incompatibility. Trace element compositions of Akaki lavas define an array extending between 'back-arc lava'-like compositions, and the field defined by Troodos boninites from the upper part of the lava sequence. Troodos lavas were derived from a mantle source that underwent early melt depletion, and later enrichment by both fluids and small degree melts. These processes can explain the unusual negative correlation of Pb/Ce with Zr/Nb and Ba/Nb in Troodos extrusives. Although some Troodos lavas are similar in composition to lavas from back-arc spreading centres, the boninites from the upper parts of the lava pile do not appear to have exact compositional equivalents among lavas from fore-arcs, back-arcs or other tectonic settings where similar rocktypes have been recovered. We suggest that the geochemical evolution inferred for the mantle source of Troodos lavas, together with geological evidence is most consistent with an origin for the Troodos Ophiolite at a spreading centre close to a ridge-trench-trench, or ridge-trench-transform triple junction, where highly depleted, subduction-modified, fluid-enriched mantle wedge material was able to upwell and decompress to shallow depths in a 'fore-arc' location. In such a tectonic setting, arc volcanism is captured by the spreading centre, explaining the lack of evidence for subaerial arc magmatism in Troodos. Rapid lateral migration of the triple junction could account for the similar ages of other Tethyan supra-subduction zone ophiolites. © 2014 Elsevier B.V.



FAU Authors / FAU Editors

Beier, Christoph PD Dr.
Lehrstuhl für Endogene Geodynamik
Brandl, Philipp
Lehrstuhl für Endogene Geodynamik
Freund, Sarah
Lehrstuhl für Endogene Geodynamik
Haase, Karsten Prof. Dr.
Lehrstuhl für Endogene Geodynamik
Keith, Manuel
Lehrstuhl für Endogene Geodynamik
Regelous, Marcel PD Dr.
Geozentrum Nordbayern
Weinzierl, Christoph
Lehrstuhl für Endogene Geodynamik


How to cite

APA:
Regelous, M., Haase, K., Freund, S., Keith, M., Weinzierl, C., Beier, C.,... Schmidt, H. (2014). Formation of the Troodos Ophiolite at a triple junction: Evidence from trace elements in volcanic glass. Chemical Geology, 386, 66-79. https://dx.doi.org/10.1016/j.chemgeo.2014.08.006

MLA:
Regelous, Marcel, et al. "Formation of the Troodos Ophiolite at a triple junction: Evidence from trace elements in volcanic glass." Chemical Geology 386 (2014): 66-79.

BibTeX: 

Last updated on 2018-06-08 at 16:08