The origin of evolved volcanic rocks in Methana, Greece

Conference contribution
(Abstract of a poster)


Publication Details

Author(s): Schönhofen M, Wölki D, Haase K, Beier C
Publication year: 2017
Language: English


Abstract


The formation of evolved andesite to dacite magmas at

subduction zones is an important process on Earth. The

Aegean arc has one of the highest rates of sediment

subduction globally that impacts on the composition of the

erupted melts. Methana peninsula is located at the western

margin of the Aegean arc and consists of numerous effusive

andesitic to dacitic eruptions. These evolved lavas frequently

contain basaltic to basaltic-andesitic enclaves. An origin of

the Methana andesites as a result of melting of mantle

hybridized by sediment melts can be excluded from the

occurrence of basaltic enclaves. Petrological and geochemical

data suggest shallow crustal processes playing a crucial role

in the formation of these rocks. The major element patterns

(e.g. FeO*, Al2O3 or TiO2 vs. MgO) show evidence for

fractional crystallization. Mineral compositions display

oscillatory zonings, disequilibrium textures, secondary rim

overgrowths and different mineral populations indicating

complex mixing of magmas. Plagioclase generations can

mainly be distinguished by their size and phenocrysts display

anortithe contents from 43 to 88, while amphiboles show

evidence for polybaric fractionation. Thermobarometric

calculations using amphibole-plagioclase assemblages imply

that magma mixing occurs in the shallow crust (9-15km)

feeding the volcanic eruptions. We develop a model of a

deep-reaching magma system reaching to the crust-mantle

boundary. This can explain continuous magma mixing along

a range of depths. Fe-Ti oxide thermometry yields partly

higher temperatures than the plagioclase-amphibole

thermometer and possibly resulting from rapid magma ascent.

Explosive volcanism dominates the central and eastern

Aegean islands, e.g., Santorini or Kos [1], while Methana

displays extensive effusive volcanism with lava domes and

flows. We interpret this to result from pre-eruptive re-heating

[2] by recharge of more primitive and hotter magma from the

crust-mantle boundary. The larger crustal thickness in the

western Aegean may influence the eruptive mechanism by

intensive degassing covering a higher distance during magma

ascent than in other parts of the arc.

[1] Druitt et al. (2016), Journal of Petrology 57(3), 461-

494; [2] Ruprecht & Bachmann (2010), Geology, 38(10),

919-922.



FAU Authors / FAU Editors

Beier, Christoph PD Dr.
Lehrstuhl für Endogene Geodynamik
Haase, Karsten Prof. Dr.
Lehrstuhl für Endogene Geodynamik
Schönhofen, Milena
Lehrstuhl für Endogene Geodynamik
Wölki, Dominic
Lehrstuhl für Endogene Geodynamik


How to cite

APA:
Schönhofen, M., Wölki, D., Haase, K., & Beier, C. (2017). The origin of evolved volcanic rocks in Methana, Greece. Poster presentation at Goldschmidt 2017, Palais des Congrès de Paris 2 Place de la Porte Maillot, 75017 Paris, France, FR.

MLA:
Schönhofen, Milena, et al. "The origin of evolved volcanic rocks in Methana, Greece." Presented at Goldschmidt 2017, Palais des Congrès de Paris 2 Place de la Porte Maillot, 75017 Paris, France 2017.

BibTeX: 

Last updated on 2018-23-11 at 06:06