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Interaction magma – sédiments dans les grandes provinces volcaniques : implications pour la formation de gisements et impact sur l'environnement

Abstract : The objective of my thesis was to investigate the interaction between mafic magmas and their sedimentary wall-rock.
Chapter 1 is a short review of the effects of wall-rock assimilation on magma compositions and of the intrusion of magma on the texture and composition of the wall rocks (contact metamorphism). It is recalled that the interaction of magmas with sedimentary wallrocks is often associated with ore formation and possible effects on the environment are also discussed.
Chapter 2, a paper in English now accepted for publication in Mineralium Deposita, provides a description of the contact aureoles around the Panzhihua intrusion in China and a new explanation for the formation of its iitanomagnetite deposits.
Chapter 3 focuses on the formation of marbles and skarns in the Panzhihua contact aureole. Trace element and isotopic data provide explanations for this process: most of the lithologies formed in a “closed-system” for the major and trace elements. However the aureole was largely decarbonated and hydrated, which implies large fluid flow. A brucite marble adjacent to the Panzhihua intrusion shows evidence of partial melting (~20%) and a skarn (zebra-rock) shows evidence of complex diffusive interaction between dolerite and dolostone.
Chapter 4 is related to our work on a second contact aureole, around the Aguablanca magmatic sulfide deposits in Spain. The intrusion was emplaced in limestone and fine-grained clastic sediments. The chemical composition of the rocks from the intrusion shows evidence of assimilation of carbonates. This could have changed the fO2 of the magma and may be linked to the formation of the sulfide deposit. I performed a simple modeling and calculated the chemical composition of the protolith from the composition of the skarns. I then showed that the formation of calcsilicates from impure limestones releases more CO2 than the simple heating of pure limestone.
Chapter 5, a manuscript in English to be submitted for publication in the journal Geology, provides a review of the consequences on the environment of the formation of a large igneous province (LIP). We show that there is no clear link between the volume of emitted basalts and the intensity of mass extinctions and propose that contact metamorphism of sedimentary rocks in the magmatic plumbing of the LIP is the main source of gas. The impact of a LIP on the environment and the intensity of associated mass extinctions may be related to the types of intruded rocks rather than to the volume of the lava.
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https://tel.archives-ouvertes.fr/tel-00324119
Contributor : Clément Ganino <>
Submitted on : Wednesday, September 24, 2008 - 10:17:42 AM
Last modification on : Tuesday, September 7, 2021 - 3:54:23 PM
Long-term archiving on: : Thursday, June 3, 2010 - 8:36:55 PM

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Clément Ganino. Interaction magma – sédiments dans les grandes provinces volcaniques : implications pour la formation de gisements et impact sur l'environnement. Sciences de la Terre. Université Joseph-Fourier - Grenoble I, 2008. Français. ⟨tel-00324119⟩

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