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Ganne Jérôme, Bachmann O., Feng X. (2018). Deep into magma plumbing systems : interrogating the crystal cargo of volcanic deposits. Geology, 46 (5), p. 415-418. ISSN 0091-7613.

Titre du document
Deep into magma plumbing systems : interrogating the crystal cargo of volcanic deposits
Année de publication
2018
Type de document
Article référencé dans le Web of Science WOS:000431359800011
Auteurs
Ganne Jérôme, Bachmann O., Feng X.
Source
Geology, 2018, 46 (5), p. 415-418 ISSN 0091-7613
Volcanic units and their crystals carry a memory of hidden magma reservoirs. Here, through a statistical assessment of a worldwide compilation of volcanic bulk-rock and associated mineral data, we can quantify the proportion of crystals that appear in disequilibrium with their bulk-rock composition, over a large range of temperature conditions and magma types. Minerals in these erupted units are frequently in disequilibrium with their bulk-rock chemistries, particularly in crystal-rich material of intermediate composition (similar to dacites, with up to 60%-80% disequilibrium). The disequilibrium crystals can be grouped in two categories: (1) dominantly more evolved than their hosts (in mafic magmas), or (2) dominantly less evolved than their hosts (in intermediate and silicic magmas). We suggest that (1) crystal accumulation, and (2) mineral entrainment from preexisting shallower mush zones, together explain the presence of more evolved crystals in mafic systems, while mingling/mixing between resident intermediate to silicic magmas and more mafic recharges in upper crustal mush zones accounts for dominantly less-evolved character of minerals in intermediate to silicic volcanic rocks. The transition between the two domains occurs in the mid-crust, at intermediate composition and temperature (similar to 1000-1100 degrees C), coincident with the SiO 2 increase and FeO tot/density decrease seen in evolving magmas. This statistical information supports other petrological and geophysical evidence indicating dominantly mafic lower crustal mush zones, producing intermediate magmas that then ascend to shallower levels (building a granodioritic upper crust) and sometimes differentiate further to rhyolite/granite/pegmatite.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020] ; Géologie et formations superficielles [064] ; Géophysique interne [066]
Description Géographique
ETATS UNIS ; COLORADO
Localisation
Fonds IRD [F B010072799]
Identifiant IRD
fdi:010072799
Contact