Article
 

The petrogenesis of plagioclase-phyric basalts at mid-ocean ridges

Öffentlich Deposited

Herunterladbarer Inhalt

PDF Herunterladen
https://ir.library.oregonstate.edu/concern/articles/h415pc41j

Descriptions

Attribute NameValues
Creator
Abstract
  • Plagioclase ultraphyric basalts (PUBs) have been sampled along most mid-ocean ridges with ultraslow to intermediate spreading rates. Over the past 40 years, the prevalent models for their origin assume positive buoyancy of plagioclase in basaltic liquids resulting in selective concentration of plagioclase phenocrysts by floatation. However, when the global population of PUB lavas is examined, this hypothesis becomes less compelling. PUB host lavas demonstrate a large range of compositions and densities, similar to aphyric glasses from the same ridge segments. Most importantly, the majority of PUB host liquids are less dense than their phenocryst cargo, meaning that plagioclase floatation within a magma chamber cannot be the driving force for phenocryst enrichment. Furthermore, PUB lavas have never been sampled on axis at fast-spreading centers or from locations with noted contemporaneous axial magma chambers, where PUBs should be abundant if plagioclase is buoyant in mid-ocean ridge basalt (MORB). Instead, we argue that the high modal abundance of plagioclase results from interaction between magma and preexisting zones of crystal cumulates within the lower crust, possibly followed by loss of olivine during magma ascent. PUBs erupt when the magma maintains an ascent velocity greater than the settling rate of the plagioclase phenocrysts, which precludes long crustal residence times for these magmas. In addition to being a proxy for lower spreading rates, our findings also suggest that PUB eruption can also be used as a proxy for the absence of a magma chamber or transport through a conduit system that bypassed an axial chamber.
  • Keywords: Mid-ocean ridges, Plagioclase, Magma transport, PUB
Resource Type
DOI
Date Available
Date Issued
Citation
  • Lange, A. E., R. L. Nielsen, F. J. Tepley III, and A. J. R. Kent (2013), Petrogenesis of plagioclase-phyric basalts at mid-ocean ridges, Geochemistry Geophysics Geosystems, 14, 3282–3296. doi:10.1002/ggge.20207
Journal Title
Journal Volume
  • 14
Journal Issue/Number
  • 8
Urheberrechts-Erklärung
Funding Statement (additional comments about funding)
  • This work was funded by NSF grant COCE0927773.
Publisher
Peer Reviewed
Language
Replaces

Beziehungen

Parents:

This work has no parents.

Artikel

Miniaturansicht Titel Hochladedatum Sichtbarkeit Aktionen
file details LangeAmyCEOASPetrogenesisPlagioclase-Phyric_SupportingInformation.zip 07/25/2017 Öffentlich
file details LangeAmyCEOASPetrogenesisPlagioclase-Phyric.pdf 07/25/2017 Öffentlich