Investigating the connection between superhydrous melts, magma reservoir nucleation and the scarcity of mafic eruptions in post-collisional settings
OPEN ACCESS
Loading...
Author / Producer
Date
2026-04
Publication Type
Journal Article
ETH Bibliography
yes
OPEN ACCESS
Data
Rights / License
Abstract
Magma reservoir emplacement in the brittle upper-crust typically requires prolonged heating to modify host-rock rheology, allowing magma to accumulate rather than erupt. In thermally immature crust, early eruptions are expected to be mafic, yet many volcanic provinces, particularly those with water-rich melts, lack significant initial mafic volcanism, suggesting an alternative trapping mechanism. We investigate this using Caraci volcano (Romania's Apuseni Mountains), a water-rich system that started with relatively differentiated, andesitic eruptions. The first eruptions at Caraci extruded water-rich (5–6 ± 0.35 wt% dissolved H2O) amphibole-plagioclase andesites (890–920 ± 22 °C) stored at water-saturated conditions in the upper-crust (∼2 ± 0.5 kbar). These magmas were associated with superhydrous primitive melts (>6 wt% H₂O), which evolved in a polybaric system (crystallization pressure varying from 2 to 8 ± 0.5 kbar), evidenced by high-Mg amphibole and delayed plagioclase crystallization. These deeper storage melts likely reached water saturation during ascent towards the upper crust, inducing degassing and crystallization, which increased viscosity and enabled stalling in the cold crust, explaining the lack of initial mafic eruptions and providing the efficient trapping mechanism in a thermally immature crust. Progressive drying of the source and generation of less hydrous magmas initiated the eruptions and construction of the stratovolcano, and ultimately terminated the system. As a result, the final eruption extruded somewhat drier (4–4.5 ± 0.35 wt% H2O), hotter (930–960 ± 45 °C) pyroxene-bearing andesites erupted from water-undersaturated storage. This trapping mechanism of water-rich magmas may explain the typical scarcity of mafic volcanism in arc and post-collisional settings.
Permanent link
Publication status
published
Editor
Book title
Journal / series
Volume
472
Pages / Article No.
108542
Publisher
Elsevier
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Magma reservoir emplacement; Superhydrous melts; Magma storage environment; Volcano lifecycle; Post-collisional volcanism