The understanding of the geochemical and petrophysical evolution of magmas forming intermediate c... more The understanding of the geochemical and petrophysical evolution of magmas forming intermediate calc-alkaline batholiths at shallow crustal levels critically depends on knowledge of the phase equilibria relations along the liquid line of descent. Here, we present experimental results for a tonalitic system at a pressure of 200 MPa and under water-saturated conditions. Melting experiments were performed at temperatures between 700 and 1000 °C in externally heated HCM pressure vessels, with oxygen fugacity controlled close to the Ni–NiO buffer equilibrium (NNO) employing an argon–methane mixture as pressure medium and Co–Pd redox sensors to verify fO2 conditions. Natural rock powder of a medium-K tonalite from the Adamello Batholith in Northern Italy served as experimental starting material. Based on compositional data of stable phases in the run products and images of entire run charges, mass balance calculations as well as image processing were performed to investigate the evolution...
Crustal-scale magmatic systems act as filters between the mantle and the atmosphere, and can gene... more Crustal-scale magmatic systems act as filters between the mantle and the atmosphere, and can generate large volcanic eruptions that pose significant hazards while altering Earth’s climate. Quantifying the growth rates, magma fluxes, and duration of storage at different crustal levels is crucial for understanding such systems, but these parameters are poorly constrained due to the scarcity of exposed crustal sections. Here we present the first detailed reconstruction of magma emplacement and differentiation time scales of a complete crustal-scale igneous system exposed in the southern Alps (Ivrea-Sesia region, northern Italy) to quantify the magma fluxes and duration of transcrustal magmatism. Integrated zircon U-Pb petrochronology and numerical modeling provides unprecedented evidence that the volcanic and plutonic bodies are directly related to each other both chemically and temporally, suggesting that the entire magmatic system grew rapidly from its deepest roots to the erupted pr...
To reflect magmatic conditions, volcanic rocks must retain their compositions through eruption an... more To reflect magmatic conditions, volcanic rocks must retain their compositions through eruption and post-eruptive cooling. Mostly, this is the case. However, welded ignimbrites from the Yellowstone–Snake River Plain magmatic province reveal systematic modification of the lithium (Li) inventory by post-eruptive processes. Here we show that phenocrysts from slowly cooled microcrystalline ignimbrite interiors consistently have significantly more Li than their rapidly quenched, glassy, counterparts. The strong association with host lithology and the invariance of other trace elements indicate that Li remains mobile long after eruption and readily passes into phenocrysts via diffusion as groundmass crystallisation increases the Li contents of the last remaining melts. Li isotopic measurements reveal that this diffusion during cooling combined with efficient degassing on the surface may significantly affect the Li inventory and isotopic compositions of volcanic rocks. Utilisation of Li for...
Journal of Geophysical Research: Solid Earth, 1995
In order to understand the role of mica‐rich rocks as a source of granite magmas, a series of mel... more In order to understand the role of mica‐rich rocks as a source of granite magmas, a series of melting experiments was performed on two different starting materials. The first composition is a model biotite gneiss consisting of 30 wt % biotite, 30 wt % plagioclase, and 40 wt % quartz. The second composition is a model two‐mica pelites consisting of 15 wt % biotite, 15 wt % muscovite, 30 wt % plagioclase, and 40 wt % quartz. Experiments were performed under vapor‐absent conditions at 1.0 GPa and between 750° and 950°C. With only biotite in the starting material the volume of melt is always less than 15 vol % below 900°C and reaches 25 vol % at 950°C. In experiments that involve both biotite and muscovite in the starting material, the melt proportion increases up to 28 vol % at 825°C and reaches 60 vol % at 950°C. For the biotite‐plagioclase‐quartz (BPQ) assemblage, the solidus is located at 800°C at 1.0 GPa. The melting reaction produces a metaluminous granitic liquid and leaves a res...
... Some completely transparent gemmy crystals with brilliant sub-adamantine luster are present a... more ... Some completely transparent gemmy crystals with brilliant sub-adamantine luster are present as well (Fig. ... Jaques, AL, Hall, AE, Sheraton, JW, Smith, JB, Sun, SS, Drew, RM, Foudoulis, C., and ... Geochimica et Cosmochimica Acta, 59, 781791.[CrossRef][Web of Science][GeoRef ...
The understanding of the geochemical and petrophysical evolution of magmas forming intermediate c... more The understanding of the geochemical and petrophysical evolution of magmas forming intermediate calc-alkaline batholiths at shallow crustal levels critically depends on knowledge of the phase equilibria relations along the liquid line of descent. Here, we present experimental results for a tonalitic system at a pressure of 200 MPa and under water-saturated conditions. Melting experiments were performed at temperatures between 700 and 1000 °C in externally heated HCM pressure vessels, with oxygen fugacity controlled close to the Ni–NiO buffer equilibrium (NNO) employing an argon–methane mixture as pressure medium and Co–Pd redox sensors to verify fO2 conditions. Natural rock powder of a medium-K tonalite from the Adamello Batholith in Northern Italy served as experimental starting material. Based on compositional data of stable phases in the run products and images of entire run charges, mass balance calculations as well as image processing were performed to investigate the evolution...
Crustal-scale magmatic systems act as filters between the mantle and the atmosphere, and can gene... more Crustal-scale magmatic systems act as filters between the mantle and the atmosphere, and can generate large volcanic eruptions that pose significant hazards while altering Earth’s climate. Quantifying the growth rates, magma fluxes, and duration of storage at different crustal levels is crucial for understanding such systems, but these parameters are poorly constrained due to the scarcity of exposed crustal sections. Here we present the first detailed reconstruction of magma emplacement and differentiation time scales of a complete crustal-scale igneous system exposed in the southern Alps (Ivrea-Sesia region, northern Italy) to quantify the magma fluxes and duration of transcrustal magmatism. Integrated zircon U-Pb petrochronology and numerical modeling provides unprecedented evidence that the volcanic and plutonic bodies are directly related to each other both chemically and temporally, suggesting that the entire magmatic system grew rapidly from its deepest roots to the erupted pr...
To reflect magmatic conditions, volcanic rocks must retain their compositions through eruption an... more To reflect magmatic conditions, volcanic rocks must retain their compositions through eruption and post-eruptive cooling. Mostly, this is the case. However, welded ignimbrites from the Yellowstone–Snake River Plain magmatic province reveal systematic modification of the lithium (Li) inventory by post-eruptive processes. Here we show that phenocrysts from slowly cooled microcrystalline ignimbrite interiors consistently have significantly more Li than their rapidly quenched, glassy, counterparts. The strong association with host lithology and the invariance of other trace elements indicate that Li remains mobile long after eruption and readily passes into phenocrysts via diffusion as groundmass crystallisation increases the Li contents of the last remaining melts. Li isotopic measurements reveal that this diffusion during cooling combined with efficient degassing on the surface may significantly affect the Li inventory and isotopic compositions of volcanic rocks. Utilisation of Li for...
Journal of Geophysical Research: Solid Earth, 1995
In order to understand the role of mica‐rich rocks as a source of granite magmas, a series of mel... more In order to understand the role of mica‐rich rocks as a source of granite magmas, a series of melting experiments was performed on two different starting materials. The first composition is a model biotite gneiss consisting of 30 wt % biotite, 30 wt % plagioclase, and 40 wt % quartz. The second composition is a model two‐mica pelites consisting of 15 wt % biotite, 15 wt % muscovite, 30 wt % plagioclase, and 40 wt % quartz. Experiments were performed under vapor‐absent conditions at 1.0 GPa and between 750° and 950°C. With only biotite in the starting material the volume of melt is always less than 15 vol % below 900°C and reaches 25 vol % at 950°C. In experiments that involve both biotite and muscovite in the starting material, the melt proportion increases up to 28 vol % at 825°C and reaches 60 vol % at 950°C. For the biotite‐plagioclase‐quartz (BPQ) assemblage, the solidus is located at 800°C at 1.0 GPa. The melting reaction produces a metaluminous granitic liquid and leaves a res...
... Some completely transparent gemmy crystals with brilliant sub-adamantine luster are present a... more ... Some completely transparent gemmy crystals with brilliant sub-adamantine luster are present as well (Fig. ... Jaques, AL, Hall, AE, Sheraton, JW, Smith, JB, Sun, SS, Drew, RM, Foudoulis, C., and ... Geochimica et Cosmochimica Acta, 59, 781791.[CrossRef][Web of Science][GeoRef ...
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