Chemical, Physical and Temporal Evolution of Magmatic Systems
Our understanding of the physical and chemical processes that regulate the evolution of magmatic systems has improved tremendously since the foundations were laid down 100 years ago by Bowen. The concept of crustal magma chambers has progressively evolved from molten-rock vats to thermally, chemically and physically heterogeneous reservoirs that are kept active by the periodic injection of magma. This new model, while more complex, provides a better framework to interpret volcanic activity and decipher the information contained in intrusive and extrusive rocks.
Igneous/metamorphic petrology, geochemistry, geochronology and numerical modelling all contributed towards this new picture of crustal magmatic systems. This book provides an overview of the wide range of approaches that can nowadays be used to understand the chemical, physical and temporal evolution of magmatic and volcanic systems.
Constraining magmatic fluxes through thermal modelling of contact metamorphism
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Published:January 01, 2015
Abstract
The thermal evolution of a contact aureole is strongly dependent on the emplacement mode of the intrusion that is causing the thermal anomaly. Inferences on the emplacement mode can be made if solid temperature estimates are available. The contact aureole of the Western Adamello Tonalite provides a unique combination of magma ascent close to the host rock and suitable rock chemistry. We use three mineral reactions at different distances in the aureole in combination with phase petrology to estimate temperatures. These temperatures are not reproducible by thermal models considering the emplacement of the intrusion as a single batch. The external zone of the intrusion represents a feeder conduit in which magma was transported. We investigated the thermal effect of the conduit on the host rocks using thermal models. Different thermal profiles for the aureole are obtained by varying flow/no-flow times, conduit thickness and magma temperature. We show that only a few combinations match the temperature constraints in the aureole, and that the amount of magma transported through the conduit can be calculated. A comparison with time-averaged fluxes of recent volcanoes and the presence of reworked volcanic sediments in the surroundings of the Adamello batholith indicate that the calculated rates and volumes are plausible.
Tables comparing sample compositions with literature experimental data are available at http://www.geolsoc.org.uk/SUP18847
- Alps
- andalusite
- aureoles
- Central Alps
- chemical composition
- contact metamorphism
- country rocks
- crystallization
- diorites
- emplacement
- Europe
- field studies
- flows
- geometry
- host rocks
- igneous rocks
- intrusions
- isograds
- Italy
- magma transport
- magmas
- magmatism
- mathematical methods
- metamorphism
- mineral assemblages
- models
- nesosilicates
- orthosilicates
- P-T-t paths
- paragenesis
- partial melting
- pelitic texture
- petrography
- petrology
- phase equilibria
- plutonic rocks
- polymetamorphism
- rates
- Rhaetian Alps
- silicates
- Southern Europe
- spectra
- temperature
- textures
- thermal history
- time factor
- tonalite
- transport
- viscosity
- volcanism
- volume
- X-ray fluorescence spectra
- zoning
- Adamello Batholith
- magma conduits
- Western Adamello Tonalite
- Lozio Shales