Project

Discipline

Plutons; zircon geochronology; cross correlation; Volcanic eruptions; magma reservoirs

Lead
Cosa succede prima di un'eruzione vulcanica
Lay summary
Misure geofisiche e le analisi chimiche dei magmi emessi durante le eruzioni vulcaniche dimostrano che le camere magmatiche contengono magmi fortemente eterogenei. I magmi a più alta temperatura (che possono essere eruttati) sono distribuiti in lenti all’interno di magma fortemente cristallizzati (che non possono essere eruttati) e rappresentano una porzione variabile del contenuto della camera magmatica. Queste differenze nella distribuzione di temperatura e del contenuto di cristalli non ci permettono di ottenere un’immagine nitida dei reservoir magmatici e quindi dei processi fisici che finalmente culminano in un eruzione vulcanica. La composizione dei magmi e dei cristalli che essi contengono varia in funzione della temperatura e quindi se si potesse determinare il numero totale di cristalli di diversa composizione emessi durante un’eruzione, si potrebbe determinare la dimensione relativa delle regioni della camera magmatica che possono essere eruttate. In questo progetto utilizzeremo una combinazione di metodi geochimici classici, matematica applicata e statistica per ottenere e trattare una quantità elevata di dati così da arrivare a comprendere le condizioni presenti in una camera magmatica prima di diverse eruzioni vulcaniche. I nostri dati ci permetteranno anche di ottenere informazioni sulla distribuzione spaziale delle lenti di magma eruttabile e quindi di comprendere meglio quali processi portano un vulcano ad eruttare.

Direct link to Lay Summary

Last update: 31.03.2017

Natural persons

Number	Title	Start	Funding scheme

I seek funding to complete the research of Miss Line Probst (two years; project n. 200021_162503) and Miss Eva Hartung (one year; project n. 200021_150204). The common target of these projects is to understand the thermal, chemical and physical evolution of magma reservoirs in the period preceding volcanic eruptions. Miss Probst uses a mathematical approach to understand the thermal and chemical structure of sub-volcanic reservoirs before volcanic eruptions from the study of volcanic products. The project of Miss Hartung focuses on the characterisation of the chemical and physical processes leading to the extraction of melt-rich magmas, which can precede volcanic eruptions. The common scientific target of these projects allows me to naturally merge them following the new guidelines for research proposals of the Swiss National Science Foundation. These two projects complement each other by combing petrology, geochronology and mathematical approaches and share the common research target of understanding the sequence of events preceding volcanic eruptions. The applied mathematics portion of the project will be further developed thanks to the on-going collaboration with Prof. Martin J. Gander of the Section of Mathematics of the University of Geneva. Project n. 200021_162503 started less than one year ago and Miss Probst has finalised a scientific article that delineates an objective mathematical method to define the genetic relationships between minerals. These study shows that chemical profiles in minerals recovered from products of volcanic eruptions can be used to determine the pre-eruptive thermal and chemical structure of magma reservoirs. Following the comments from the project reviewers, the first two years of Miss Probst project are being focused on the analyses of minerals from the voluminous Kilgore Tuff eruption (USA). In the next two years we intend to fully automate the current method and apply it to the 2004-2006 eruption of Mount St Helens (USA). This eruption was intensively monitored and a set of samples collected during the eruption will be made available thanks to the collaboration with Prof. Jon Blundy of the University of Bristol. We will trace the relative proportion of mineral sharing growth conditions during the eruptive period to identify eventual changes in the thermal and chemical structure of the reservoir over the period of magma extrusion at the surface. The group of Prof. Blundy collected mineral chemistry and melt inclusion data that will be integrated with our results. The Mount St Helens data will be finally compared with those collected for the Kilgore tuff. The results of Project n. 200021_150204 show that the chemical zoning measured along a vertical section of the Takidani pluton was produced by the extraction of residual melt from magma crystallised to about 60 wt.%. This process produced a volume of melt-rich (and potentially eruptible) magma showing that this magma reservoir had the potential to fed volcanic activity (one submitted manuscript, one manuscript in preparation). In 2013 we sampled volcanic products of age similar to Takidani in the area surrounding the pluton. During the additional one year of research of Miss Hartung, we intend to perform a combined geochronology and geochemistry study on zircons from the Takidani pluton and the volcanic products to establish the potential relationships between plutonic and volcanic rocks. Additionally, the model developed by Miss Probst will be applied to catholuminescence images of zircons collected in the Takidani pluton and the hypothetically associated volcanic products. All samples and equipment required to develop this project are already available at the University of Geneva. These projects will increase our understanding of the relationships between plutonic and volcanic rocks and provide insights on the thermal and chemical structure of magma reservoir before volcanic eruptions. If the link between volcanic and plutonic rocks of the Takidani pluton will be established, zircon geochronology will provide insights also on the timescales required to assemble a body of eruptible magma before volcanic eruptions. These data are essential to address if volume of eruptible magma in the Earth’s crust can be identified with geophysical methods and to identify the most relevant monitoring parameters signalling an impending volcanic eruption.