『Abstract
The large number of geochemical data gathered on the Gruppo di
Voltri springs confirm that progressive interaction of meteoric
waters with ultramafic rocks variably affected by serpentinization
leads initially to the formation of Mg-HCO3
waters when the system is open to CO2, and
Na-HCO3 and Ca-OH type water upon further
interaction with the rock, under highly reducing closed-system
conditions with respect to CO2. As indicated
by 3H data, these high-pH waters have had long residence
times underground in deep aquifers hosted by serpentinitic rocks.
These waters are the only available evidence of the presence of
such deep aquifers. High-pressure injection of CO2
into these deep aquifers was simulated by reaction path modeling.
Results indicate that this is a feasible methodology to reduce
the inputs of anthropogenic CO2 into the
atmosphere. Serpentinitic rocks have a high capacity for CO2 sequestration, mainly through formation of carbonate
minerals. Dissolution of serpentinitic rocks and precipitation
of magnesite and silica minerals occurs naturally in areas of
high terrestrial CO2 fluxes such as in southern
Tuscany, corroborating the feasibility of this methodology of
CO2 sequestration. However, this process
causes a progressive decrease in the porosity of the aquifer,
at least under closed-system conditions. These side effects must
be carefully evaluated by means of further laboratory tests and
field activities.』
1. Introduction
2. The high-pH waters
2.1. Geological background
2.2. Sampling and analyses
2.3. Isotope geochemistry
2.4. Chemical characteristics of waters interacting with ultramafic
rocks and serpentinites
3. The dissolution kinetics of serpentine
4. Simulation of CO2 sequestration through
high-pressure injection into a deep aquifer hosted in serpentinitic
rocks
4.1. Setting up the water-rock interaction model
4.2. Solid product phases
4.3. The aqueous solution
4.4. CO2 sequestration
4.5. Changes in the porosity of aquifer rocks
5. Discussion
6. Conclusions
Acknowledgements
Appendix. Analytical method for the determination of TDIC
References