Next Article in Journal
High-Efficiency Catalysis of Peroxymonosulfate by MgO for the Degradation of Organic Pollutants
Previous Article in Journal
Synthesis of Geopolymers from Mechanically Activated Coal Fly Ash and Improvement of Their Mechanical Properties
Previous Article in Special Issue
Mineralogical Transformations of Heated Serpentine and Their Impact on Dissolution during Aqueous-Phase Mineral Carbonation Reaction in Flue Gas Conditions
Open AccessFeature PaperArticle

Spontaneous Serpentine Carbonation Controlled by Underground Dynamic Microclimate at the Montecastelli Copper Mine, Italy

1
Istitute of Geoscience and Earth Resources, National Research Council of Italy (CNR), 56100 Pisa, Italy
2
Institute of Earth Sciences, University of Lausanne, Geopolis Building, CH-1015 Lausanne, Switzerland
3
Earth Sciences Department, Pisa University, Via S. Maria 53, I-56126 Pisa, Italy
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(1), 1; https://doi.org/10.3390/min10010001
Received: 15 October 2019 / Revised: 3 December 2019 / Accepted: 5 December 2019 / Published: 18 December 2019
(This article belongs to the Special Issue Geological and Mineralogical Sequestration of CO2)
Understanding low temperature carbon sequestration through serpentinite–H2O–CO2 interaction is becoming increasingly important as it is considered a potential approach for carbon storage required to offset anthropogenic CO2 emissions. In this study, we present new insights into spontaneous CO2 mineral sequestration through the formation of hydromagnesite + kerolite with minor aragonite incrustations on serpentinite walls of the Montecastelli copper mine located in Southern Tuscany, Italy. On the basis of field, petrological, and geochemical observations coupled with geochemical modeling, we show that precipitation of the wall coating paragenesis is driven by a sequential evaporation and condensation process starting from meteoric waters which emerge from fractures into the mine walls and ceiling. A direct precipitation of the coating paragenesis is not compatible with the chemical composition of the mine water. Instead, geochemical modeling shows that its formation can be explained through evaporation of mine water and its progressive condensation onto the mine walls, where a layer of serpentinite powder was accumulated during the excavation of the mine adits. Condensed water produces a homogeneous film on the mine walls where it can interact with the serpentinite powder and become enriched in Mg, Si, and minor Ca, which are necessary for the precipitation of the observed coating paragenesis. The evaporation and condensation processes are driven by changes in the air flow inside the mine, which in turns are driven by seasonal changes of the outside temperature. The presence of “kerolite”, a Mg-silicate, is indicative of the dissolution of Si-rich minerals, such as serpentine, through the water–powder interaction on the mine walls at low temperature (~17.0 to 18.1 °C). The spontaneous carbonation of serpentine at low temperature is a peculiar feature of this occurrence, which has only rarely been observed in ultramafic outcrops exposed on the Earth’s surface, where instead hydromagnesite predominantly forms through the dissolution of brucite. The high reactivity of serpentine observed, in this study, is most likely due to the presence of fine-grained serpentine fines in the mine walls. Further study of the peculiar conditions of underground environments hosted in Mg-rich lithologies, such as that of the Montecastelli Copper mine, can lead to a better understanding of the physical and chemical conditions necessary to enhance serpentine carbonation at ambient temperature. View Full-Text
Keywords: CO2 mineral sequestration; hydromagnesite; kerolite; serpentinite; Cu mine; Montecastelli; underground microclimate CO2 mineral sequestration; hydromagnesite; kerolite; serpentinite; Cu mine; Montecastelli; underground microclimate
Show Figures

Figure 1

MDPI and ACS Style

Boschi, C.; Bedini, F.; Baneschi, I.; Rielli, A.; Baumgartner, L.; Perchiazzi, N.; Ulyanov, A.; Zanchetta, G.; Dini, A. Spontaneous Serpentine Carbonation Controlled by Underground Dynamic Microclimate at the Montecastelli Copper Mine, Italy. Minerals 2020, 10, 1.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop