Evidence for chemically heterogeneous Arctic mantle beneath the Gakkel Ridge
| Autor: | Jessica M. Warren, Megan E. D’Errico, Marguerite Godard |
|---|---|
| Přispěvatelé: | Stanford University, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Předmět: |
Peridotite
geography Olivine geography.geographical_feature_category 010504 meteorology & atmospheric sciences Geochemistry Crust Mid-ocean ridge engineering.material 010502 geochemistry & geophysics 01 natural sciences Mantle (geology) 13. Climate action Lithosphere Oceanic crust Ridge Geochemistry and Petrology [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry engineering 14. Life underwater Geology 0105 earth and related environmental sciences |
| Zdroj: | Geochimica et Cosmochimica Acta Geochimica et Cosmochimica Acta, Elsevier, 2016, 174, pp.291-312. ⟨10.1016/j.gca.2015.11.017⟩ |
| ISSN: | 0016-7037 |
| DOI: | 10.1016/j.gca.2015.11.017 |
| Popis: | International audience; Ultraslow spreading at mid-ocean ridges limits melting due to on-axis conductive cooling, leading to the prediction that peridotites from these ridges are relatively fertile. To test this, we examined abyssal peridotites from the Gakkel Ridge, the slowest spreading ridge in the global ocean ridge system. Major and trace element concentrations in pyroxene and olivine minerals are reported for 14 dredged abyssal peridotite samples from the Sparsely Magmatic (SMZ) and Eastern Volcanic (EVZ) Zones. We observe large compositional variations among peridotites from the same dredge and among dredges in close proximity to each other. Modeling of lherzolite trace element compositions indicates varying degrees of non-modal fractional mantle melting, whereas most harzburgite samples require open-system melting involving interaction with a percolating melt. All peridotite chemistry suggests significant melting that would generate a thick crust, which is inconsistent with geophysical observations at Gakkel Ridge. The refractory harzburgites and thin overlying oceanic crust are best explained by low present-day melting of a previously melted heterogeneous mantle. Observed peridotite compositional variations and evidence for melt infiltration demonstrates that fertile mantle components are present and co-existing with infertile mantle components. Melt generated in the Gakkel mantle becomes trapped on short length-scales, which produces selective enrichments in very incompatible rare earth elements. Melt migration and extraction may be significantly controlled by the thick lithosphere induced by cooling at such slow spreading rates. We propose the heterogeneous mantle that exists beneath Gakkel Ridge is the consequence of ancient melting, combined with subsequent melt percolation and entrapment. |
| Databáze: | OpenAIRE |
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