Search results for "Fluid Inclusion"
showing 10 items of 40 documents
Recycled crustal carbon in the depleted mantle source of El Hierro volcano, Canary Islands
2021
The Canary Islands, in the eastern Atlantic, are among the most enigmatic Oceanic Island provinces on Earth, as the mantle source feeding its volcanism exhibits wide spatial heterogeneity and a multiplicity of sources. Multi-isotope whole-rock studies have long revealed the presence of a recycled oceanic crust/lithosphere component in the mantle source. However, noble gas systematics have been more challenging to interpret, and the available carbon isotope data is limited and cannot support/dismiss this interpretation. Here, we present the very first isotopic characterisation of CO2 and noble gases (He-Ne-Ar) in fluid inclusions (FI) in minerals hosted in mantle xenoliths from El Hierro, th…
P-T path development derived from shearband boudin microstructure
2016
This work focuses on the development of a regional P-T-path from the Malpica-Lamego Ductile Shear Zone, NW Portugal, based on the microstructures of shearband boudins evolved during progressive simple shear. The combination of microstructural analysis, fluid inclusion studies, crystallographic pre- ffered orientation and fractal geometry analyses, allows to link several stages in the internal evolution of the boudin to regional P-T conditions. The boudinage process is initiated under differential stress after the original layer achieved sufficient viscosity contrast relative to the surrounding matrix. Two main transformations occur simultaneously: i) change in the external shape with contin…
Interpretative model of shearband boudins internal evolution in HT ductile shear zones
2012
The internal structure of a shearband boudin resulting from an original igneous, hydrothermal or metamorphic segregation tabular rigid body is a subject of scientific interest. It allows understanding the deformation mechanisms acting on homogeneous quartz aggregate activated during simple shear progressive deformation. This work is focused on the characterization of the internal evolution of shearband boudins, using microtextural analysis, fluid inclusions studies, fractal and OCP analysis. The proposed interpretative model shows the several structural stages that can be well established during the process of the internal evolution of shearband boudin.
Internal Differentiation of the Archean Continental Crust: Fluid-Controlled Partial Melting of Granulites and TTG-Amphibolite Associations in Central…
2009
Fault bound blocks of granulite and enderbite occur within upper amphibolite-facies migmatitic tonalitic-trondhjemitic-granodioritic (TTG) gneisses of the Iisalmi block of Central Finland. These units record reworking and partial melting of different levels of the Archean crust during a major tectonothermal event at 2·6-2·7 Ga. Anhydrous mineral assemblages and tonalitic melts in the granulites formed as a result of hydrous phase breakdown melting reactions involving amphibole at peak metamorphic conditions of 8-11 kbar and 750-900°C. A nominally fluid-absent melting regime in the granulites is supported by the presence of carbonic fluid inclusions. The geochemical signature of light rare e…
Reaction between Cu-bearing minerals and hydrothermal fluids at 800 °C and 200 MPa: Constraints from synthetic fluid inclusions
2020
Abstract Transport and deposition of copper in the Earth's crust are mainly controlled by the solubility of Cu-bearing phases and the speciation of Cu in magmatic-hydrothermal fluids. To improve our understanding of copper mobilization by hydrothermal fluids, we conducted an experimental study on the interaction between Cu-bearing phases (metallic copper, Cu2O, CuCl) and aqueous chloride solutions (H2O ± NaCl ± HCl; with Cl concentrations of 0 to 4.3 mol kg-1). The experiments were run in rapid heat/rapid quench cold-seal pressure vessels at 800 °C, 200 MPa, and logfO2 ~ NNO+2.3. Either Cu or Au capsules were used as containers. The reaction products were sampled in situ by the entrapment o…
Volatile dilution during magma injections and implications for volcano explosivity
2016
Magma reservoirs underneath volcanoes grow through episodic emplacement of magma batches. These pulsed magma injections can substantially alter the physical state of the resident magma by changing its temperature, pressure, composition, and volatile content. Here we examine plagioclase phenocrysts in pumice from the 2014 Plinian eruption of Kelud (Indonesia) that record the progressive capture of small melt inclusions within concentric growth zones during crystallization inside a magma reservoir. High-spatial-resolution Raman spectroscopic measurements reveal the concentration of dissolved H2O within the melt inclusions, and provide insights into melt-volatile behavior at the single crystal…
The Magmatic to Hydrothermal Evolution of the Intrusive Mont Saint-Hilaire Complex: Insights into the Late-stage Evolution of Peralkaline Rocks
2017
The Cretaceous Mont Saint-Hilaire complex (Quebec, Canada) comprises three major rock units that were emplaced in the following sequence: (I) gabbros; (II) diorites; (III) diverse partly agpaitic foid syenites. The major element compositions of the rock-forming minerals, age-corrected Nd and oxygen isotope data for mineral separates and trace element data of Fe-Mg silicates from the various lithologies imply a common source for all units. The distribution of the rare earth elements in clinopyroxene from the gabbros indicates an ocean island basalt type composition for the parental magma. Gabbros record temperatures of 1200 to 800 degrees C, variable silica activities between 0 center dot 7 …
3 He/4He Signature of Magmatic Fluids from Telica (Nicaragua) and Baru (Panama) Volcanoes, Central American Volcanic Arc
2022
Constraining the magmatic 3He/4He signature of fluids degassed from a magmatic system is crucial for making inferences on its mantle source. This is especially important in arc volcanism, where variations in the composition of the wedge potentially induced by slab sediment fluids must be distinguished from the effects of magma differentiation, degassing, and crustal contamination. The study of fluid inclusions (FIs) trapped in minerals of volcanic rocks is becoming an increasingly used methodology in geochemical studies that integrates the classical study of volcanic and geothermal fluids. Here, we report on the first noble gas (He, Ne, Ar) concentrations and isotopic ratios of FI in olivin…
The composition of fluids stored in the central Mexican lithospheric mantle: Inferences from noble gases and CO2 in mantle xenoliths
2021
We present the first isotopic (noble gases and CO2) characterization of fluid inclusions coupled to Raman microspectroscopy analyses in mantle xenoliths from Central Mexico, a geodynamically complex area where the Basin and Range extension was superimposed on the Farallon subduction (terminated at 28 Ma). To characterize the isotopic signature of the Central Mexican lithospheric mantle, we focus on fluid inclusions entrapped in mantle xenoliths found in deposits of the Joya Honda maar (JH), a Quaternary monogenetic volcano belonging to the Ventura Espiritu Santo Volcanic Field (VESVF) in the state of San Luis Potosí (central Mexico). Thirteen ultramafic plagioclase-free xenoliths were selec…
The geochemical riddle of “low-salinity gypsum” deposits
2022
International audience; Gypsum makes up about one fifth of giant salt deposits formed by evaporation of seawater throughout Earth’s history. Although thermodynamic calculations and precipitation experiments predict that gypsum precipitates when the salinity of evaporating seawater attains about 110 g kg-1, gypsum deposits of the Mediterranean Salt Giant often bear the geochemical signature of precipitation from less saline water masses. Addressing this geochemical riddle is important because marine gypsum deposition and continental gypsum erosion affect the global carbon cycle. We investigated gypsum deposits formed in the marginal basins of the Mediterranean Sea during the Messinian Salini…