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The fate of magma in the Earth’s crust: Plutons and volcanic eruptions

English title The fate of magma in the Earth’s crust: Plutons and volcanic eruptions
Applicant Caricchi Luca
Number 150204
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geology
Start/End 01.04.2014 - 31.03.2017
Approved amount 216'686.00
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All Disciplines (3)

Discipline
Geology
Material Sciences
Mineralogy

Keywords (6)

Petrology; Geochemistry; Mineral chemistry; Textural analysis; Magma fractionation; Chemical evolution of the Earth's crust

Lay Summary (Italian)

Lead
The fate of magma in the Earth’s crust: Plutons and volcanic eruptions
Lay summary

In sintesi

La costruzione della crosta terrestre sulla quale viviamo, avviene principalmente in prossimità dei limiti delle placche tettoniche grazie al trasporto di magma da profondità di circa 100-40 km. I vulcani sono un’espressione di questo processo. La composizione chimica del magma che risale dalle profondità del nostro pianeta è diversa da quella della crosta terrestre e quindi processi di frazionamento chimico sono stati teorizzati come responsabili di questa trasformazione. Tuttavia, fino ad oggi non si conoscono i processi fisici responsabili del frazionamento chimico dei magmi.

Soggetto e obiettivo

Con questo progetto intendiamo identificare i meccanismi di frazionamento del magma. Siccome i processi in discussione avvengono a profondità elevate (10-30 km), utilizzeremo un sistema vulcanico che era attivo circa 1.5 milioni di anni fa e che oggi è esposto in superficie grazie all’azione della tettonica delle placche. Le rocce oggi esposte in superficie contengono informazioni chimiche che utilizzeremo per decifrare i processi responsabili per l’evoluzione e l’estrazione di magma che fu eruttato in superficie circa 1.5 milioni di anni fa. I minerali contenuti nelle rocce crescono e acquisiscono una composizioni che è funzione delle condizioni di temperatura e pressione e della chimica dei liquidi dai quali crescono. Con un approccio simile a quello utilizzato nello studio degli anelli di crescita delle piante, noi utilizzeremo piccole variazioni composizionali dei minerali per ricostruire la storia del magma e del suo frazionamento in profondità.

Un applicazione industriale del progetto

La separazione di liquidi metallici durante la produzione dell’acciaio è simile alla separazioni di liquidi residuali dai magmi ed è un problema che risulta nello spreco di energia e risorse economiche. In collaborazione con una compagnia di produzione dell’acciaio utilizzeremo i risultati di questo studio per cercare di risolvere questo problema.

 

Direct link to Lay Summary Last update: 02.10.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
The role of H2O on the extraction of melt from crystallising magmas
Hartung Eva, Weber Gregor, Caricchi Luca (2019), The role of H2O on the extraction of melt from crystallising magmas, in Earth and Planetary Science Letters, 508, 85-96.
Evidences for residual melt extraction in the Takidani pluton (Japan)
Hartung Eva, Caricchi Luca, Floess David, Wallis Simon, Harayama Satoru, Kouzmanov Kalin, Chiaradia Massimo, Evidences for residual melt extraction in the Takidani pluton (Japan), in Journal of Petrology, 1.

Collaboration

Group / person Country
Types of collaboration
Shinshu University Japan (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
University of Nagoya Japan (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Earth Observatory of Singapore (EOS) Singapore (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
ETH Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
162503 The architecture of subvolcanic reservoirs 01.12.2015 Project funding
172702 The build-up to volcanic eruptions 01.04.2017 Project funding
163991 A FEG-Electronprobe Microanalyzer for analysis of Earth materials at the sub-micron scale 01.04.2016 R'EQUIP

Abstract

With this project I seek founds for the salary of 2 PhD students and the required financial support to cover the expenses related to fieldwork and usage of analytical laboratories at the University of Geneva and the University of Lausanne. This proposal combines chemistry and rock fabric characterization to give a picture of the physical processes responsible for the construction and chemical evolution of reservoirs of potentially eruptible magma in the Earth’s crust. One of the central unknown to determine how magma evolves in the crust remains the modality of extraction of chemically evolved melts from crystallizing magmas. Solving this issue would provide fundamental information to link the chemistry of intrusive rocks and erupted magmas to the physical processes occurring in crustal reservoirs and also shed light on the dynamics of segregation of large volume of chemically evolved magmas that precedes the largest eruptions on Earth.The project will focus on two main field areas (each PhD student will focus on one area) representing end-member in terms of the geometrical configuration of the magmatic systems and chemical composition. The first target is the youngest exposed pluton on Earth (1Ma; northern Japanese Alps), and the associated products of two large dacitic-rhyolitic, explosive eruptions (total erupted tephra?400 km3). The pluton is well exposed and is vertically zoned, with the top part of the intrusion being the most evolved (granitic). This area provides a unique opportunity to study the processes of segregation and evolution of magma in the crust and the conditions leading to a large eruption. The second areas is the Blumone gabbroic complex (Adamello, northern Italy), which is characterized by a conspicuous alternation of chemically distinct vertical layers that has been interpreted as the expression of a magmatic system where chemical fractionation occurred during transport of magma to shallower depths. The investigation of the two field areas will follow the same approach:a)Oriented samples will be collected across the compositional layering. For the Takidani pluton sampling will be performed along transects from the structural base to the structural top of the intrusion spread regularly over the outcropping area. In the Blumone complex oriented samples will be collected along regularly spaced horizontal transects from the structural base of the outcrop to the top. b)Bulk rock major and trace element analyses of the collected samples will be performed to identify the major chemical differences associated to the layering evident from the field observations. These analyses may also highlight the eventual exchange of residual melt and mingling/mixing between the different portions of the magmatic systems. c)Core-to-rim chemical analyses of major and trace elements in minerals will be collected using EMPA, LA-ICP-MS and eventually FEG-EMPA and SIMS for high spatial resolution. The chemical variations of minerals record the chemical history of magma, which is directly linked to the evolution of crystallinity, gas content, residual melt composition, and also to the evolution of density, volume and rheological properties of magmas in time. Such analyses in our samples will therefore highlight if, in which region of a magmatic reservoir, and at which chemical-physical stage of the evolution of the magmatic system, major events such as the extraction of residual melt from crystallizing magma occurred. d)The geochemical part of the project will be coupled with a study of the fabrics present in the different portions of the Takidani pluton and the Blumone complex. Anisotropy of Magnetic Susceptibility (AMS; laboratory currently under construction at the University of Geneva) will be measured in the oriented samples to identify distinct regions of the magmatic system (e.g. different pulses of magma). These analyses will be complemented by X-Ray tomography to quantify the intensity of fabrics recorded by different minerals. The fabric quantification aims to identify regions of magmatic systems where melt-bearing and rheologically homogeneous magmatic mushes developed and eventually determine the flow direction of residual melt extracted from such mushes (we recently showed that the extraction of residual melt from a crystallizing magmatic mush can produce a lineation recordable with AMS). A clear understanding of the dynamics of extraction of chemically evolved and gas-rich melt from cooling magmas is important to understand how chemical evolution works in magmatic systems, to identify the processes leading to large eruptions, to advance our understanding of the genesis of ore deposits, and also to improve the steel casting process, where segregation of molten components from cooling steel is a common problem.
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