Wide-blocky veins explained by dependency of crystal growth rate on fracture surface type; insights from phase-field modeling

Vein microstructures contain a wealth of information on coupled chemical and mechanical processes of fracturing, fluid transport, and crystal growth. Numerical simulations have been used for exploring the factors controlling the development of vein microstructures; however, they have not been quanti...

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Bibliographic Details
Published in:Geology (Boulder) 2021-02, Vol.49 (6), p.641-646
Main Authors: Spruzeniece, Liene, Späth, Michael, Urai, Janos L, Ukar, Estibalitz, Selzer, Michael, Nestler, Britta
Format: Article
Language:English
Subjects:
Blue Anchor England
Calcite
carbonate rocks
carbonates
Clay minerals
Crack propagation
Crystal growth
Crystals
England
Europe
Fracture surfaces
fractures
Geology
Great Britain
Growth rate
Jurassic
Kilve England
Lilstock England
Limestone
Lower Jurassic
Mathematical models
Mesozoic
microstructure
Minerals
Modelling
Nucleation
numerical models
Numerical simulations
Permeability
petrography
rates
sed rocks, sediments
Sedimentary petrology
sedimentary rocks
Simulation
Somerset England
three-dimensional models
Transgranular fracture
two-layer models
United Kingdom
veins
Veins (geology)
Western Europe
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Summary:Vein microstructures contain a wealth of information on coupled chemical and mechanical processes of fracturing, fluid transport, and crystal growth. Numerical simulations have been used for exploring the factors controlling the development of vein microstructures; however, they have not been quantitatively validated against natural veins. Here we combined phase-field modeling with microtextural analysis of previously unexplained wide-blocky calcite veins in natural limestone and of the fresh fracture surface in this limestone. Results show that the wide-blocky vein textures can only be reproduced if ∼10%-20% of crystals grow faster than the rest. This fraction corresponds to the amount of transgranularly broken grains that were observed on the experimental fracture surfaces, which are dominantly intergranular. We hypothesize that transgranular fractures allow faster growth of vein minerals due to the lack of clay coatings and other nucleation discontinuities that are common along intergranular cracks. Our simulation results show remarkable similarity to the natural veins and reproduce the nonlinear relationship between vein crystal width and vein aperture. This allows accurate simulations of crystal growth processes and related permeability evolution in fractured rocks.
ISSN:0091-7613
1943-2682
DOI:10.1130/G48472.1