Carla Tiraboschi

University of Perugia | UNIPG · Department of Earth Sciences

The quantitative assessment of COH fluids is crucial in modeling geological processes. The composition of fluids, and in particular their H2O/CO2 ratio, can influence the melting temperatures, the location of hydration or carbonation reactions and the solute transport capability in several rock systems. In the scientific literature, COH fluids spec...

Estimates of dissolved CO2 in subduction-zone fluids are based on thermodynamic models, relying on a very sparse experimental data base. Here, we present experimental data at 1–3 GPa, 800 °C, and ∆FMQ ≈ −0.5 for the volatiles and solute contents of graphite-saturated fluids in the systems COH, SiO2–COH ( + quartz/coesite) and MgO–SiO2–COH ( + forst...

We experimentally investigated the dissolution of forsterite, enstatite and magnesite in graphite-saturated COH fluids, synthesized using a rocking piston cylinder apparatus at pressures from 1.0 to 2.1 GPa and temperatures from 700 to 1200 °C. Synthetic forsterite, enstatite, and nearly pure natural magnesite were used as starting materials. Redox...

High-pressure COH fluids have a fundamental role in a variety of geological processes. Their composition in terms of volatile species can control the solidus temperature and carbonation/decarbonation reactions, as well as influence the amount of solutes generated during fluid–rock interaction at depth. Over the last decades, several systems have be...

The role of slab-derived hydrous silicate melts in the transfer of the oxidised signature in subduction zones remains poorly constrained. We have investigated the mobility and redox state of iron in hydrous silicate melts by carrying out solubility measurements of hematite-magnetite assemblages in a piston-cylinder apparatus combined with electron...

Fluids rich in water and carbon (COH) are among the most reactive agents of mantle metasomatism and play a major role in the continuous degassing of the Earth. The addition of small amounts of H2O and CO2 depress the solidus of mantle peridotite by several hundred degrees, resulting in the common occurrence of highly mobile, volatile-rich melts, wh...

Abiotic methane (CH4) generation under subduction zone conditions has been experimentally investigated through aqueous reduction of pure C-bearing materials (e.g. carbonate minerals and organic matter). However, quantitative assessments of CH4 production in these experiments, as well as the potential effects of other components such as silica (Si)...

We present new experimental data on the effect of F on the stability of antigorite and its breakdown products at high pressures (2–6 GPa) and high temperatures (570–850 °C). The experiments show that F does not affect the stability of antigorite, but addition of F to the system affects which minerals are formed when antigorite breaks down. In a F-f...

Ocean sediments consist mainly of calcium carbonate and organic matter (phytoplankton debris). Once subducted, some carbon is removed from the slab and returns to the atmosphere as CO 2 in arc magmas. Its isotopic signature is thought to reflect the bulk fraction of inorganic (carbonate) and organic (graphitic) carbon in the sedimentary source. Her...

Organic matter, showing variable degrees of crystallinity and thus of graphitization, is an important source of carbon in subducted sediments, as demonstrated by the isotopic signatures of deep and ultra-deep diamonds and volcanic emissions in arc settings. In this experimental study, we investigated the dissolution of sp2 hybridized carbon in aque...

At active volcanoes, petrological studies have been proven to be a reliable approach in defining the depth conditions of magma transport and storage in both the mantle and the crust. Based on fluid inclusion and mineral geothermobarometry in mantle xenoliths, we propose a model for the magma plumbing system of the Island of El Hierro (Canary Island...

COH fluids are composed of the volatile species belonging to the C–O–H system, i.e. CO2, CO, CH4, H2, H2O e O2. COH fluids influence different surface and deep geological processes, such as devolatilisation reactions and metasomatic processes due to element transport in solution. The determinant factor in these processes is the composition of the C...

Fluids play a crucial role in many processes in subduction zones, influencing the melting temperatures and promoting mass transfer from the subducting lithosphere to the overlying mantle wedge. Carbon is a relevant component in deep fluids, as suggested by its occurrence in arc magmas and subduction-related rocks. Compared to H2O-only fluids, high-...

The quantitative assessment of species in COH fluids is crucial in modelling mantle processes. For instance, H2O/CO2 ratio in the fluid phase influences the location of the solidus and of carbonation/decarbonation reactions in peridotitic systems (Wyllie, 1978). In the scientific literature, the speciation of COH fluids has been generally assumed o...

COH fluids play a fundamental role in many geological processes, controlling the location of melting in subduction zones and promoting mass transfer from the subducting litosphere to the overlying mantle wedge. The properties of COH fluids are strictly dependent on the composition of the fluid in subduction systems, i.e., the speciation of the vola...

The quantitative assessment of species in COH fluids is crucial in modelling mantle processes. For instance, H2O/CO2 ratio in the fluid phase influences the location of the solidus and of carbonation/decarbonation reactions in peridotitic systems . In the scientific literature, the speciation of COH fluids has been generally assumed on the basis of...

The mass transfer from the subducting lithosphere to the overlying mantle wedge is mediated by complex solutions resulting from dehydration and decarbonation processes. Compared to H2O-only and CO2-only fluid compositions, experiments dealing with mixed H2O-CO2 fluids in equilibrium with high-pressure minerals are limited. In order to investigate t...

We experimentally investigated phlogopite- and C–O–H-bearing lherzolite to model the mantle wedge fluxed by volatiles released from a subducting crustal slab. Experiments have been carried out at 900–1050°C and 1·6–3·2 GPa, at fluid- and carbon-saturated conditions. We used an end-loaded piston cylinder apparatus and a conventional double-capsule t...

Element partitioning between carbonates and coexisting high pressure phases plays a critical role in unravelling petrogenetic processes of eclogitic rocks, peridotites, diamond-bearing rock suites, and carbonatitic magmas. Experiments were carried out on MORB and lherzolitic bulk compositions, from gel starting materials, using piston-cylinder and...

Mixed H2O-CO2 fluids, as H2O-only fluids do, are thought to play an important role in magma genesis, triggering melting processes by lowering solidus temperature of mantle rocks (e.g., Dasgupta et al., 2007). Compared to H2O-olny and CO2-only fluid compositions, experiments concerning high-pressure peridotite and mixed fluids are limited. In partic...

The mass transfer from the subducting lithosphere to the overlying mantle wedge is mediated by complex solutions deriving from dehydration and decarbonation processes. High-pressure relations among fluids/melts, carbonates, hydrous silicates, graphite/diamond and nominally volatile-free phases in COH-bearing ultramafic systems are substantially une...