Morphological instabilities in pattern formation by precipitation and crystallization processes

Krug, H.-J.; Brandtstädter, H.; Jacob, Karl-Heinz

doi:10.1007/s005310050047

Cited by 25 publications

(26 citation statements)

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“…However, the grain boundary migration only begins in the considered grain if the adjacent grains are also dolomitized as we assume grain growth to appear along dolomite/dolomite boundaries (Figure 2). The initial scatter of impurities is alternated by the advancing reaction front similar to the crystal zoning model [3]. The reaction front in our model is capable of collecting second-phase particles whereas the collected amount is inversely proportional to the size of the impurities and proportional to the concentration change between two time steps (Equation 3).…”

Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%

“…The originating dolomite crystals will prefer a low internal energy state and therefore tend to build in fewer impurities in their lattices. This cleansing process of the crystals can be compared to the generation of impurity free crystals from melt during industrial zone melting [3] even though the transition in our model is between two mineral phases and not a change of the state of matter. The Equation ( 3) outlines how we calculated the amount of particles collected by the advancing front, if the threshold for collection is not exceeded.…”

Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%

“…Once the loading-threshold of the reaction front is reached the collecting force of the front breaks down and the process switches to releasing particles [acc. [3]]. …”

Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%

“…Zebra banding occurs in claystones [1], siderite ores [2,3], and sphalerite mineralization [4]. The process of the zebra pattern formation varies depending on the rock hosting this structure.…”

Section: Introductionmentioning

confidence: 99%

“…This stress field, which arises from the crystallization stress, is thought to prevent the growth of new material in the direct vicinity [11]. A more general model for the development of banded structures in rocks is the crystal zoning model [3]. In this model a phase transition front collects impurities during its propagation.…”

Section: Introductionmentioning

confidence: 99%

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Zebra pattern in rocks as a function of grain growth affected by second-phase particles

2015

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Alternating fine grained dark and coarse grained light layers in rocks are often termed zebra patterns and are found worldwide. The crystals in the different bands have an almost identical chemical composition, however second-phase particles (e.g., fluid filled pores or a second mineral phase) are concentrated in the dark layers. Even though this pattern is very common and has been studied widely, the initial stage of the pattern formation remains controversial. In this communication we present a simple microdynamic model which can explain the beginning of the zebra pattern formation. The two dimensional model consists of two main processes, mineral replacement along a reaction front, and grain boundary migration affected by impurities. In the numerical model we assume that an initial distribution of second-phase particles is present due to sedimentary layering. The reaction front percolates the model and redistributes second-phase particles by shifting them until the front is saturated and drops the particles again. This produces and enhances initial layering. Grain growth is hindered in layers with high second-phase particle concentrations whereas layers with low concentrations coarsen. Due to the grain growth activity in layers with low second-phase particle concentrations these impurities are collected at grain boundaries and the crystals become very clean. Therefore, the white layers in the pattern contain large grains with low concentration of second-phase particles, whereas the dark layers contain small grains with a large second-phase particle concentration. The presence of the zebra pattern is characteristic for regions containing Pb-Zn mineralization. Therefore, the origin of the structure is presumably related to the mineralization process and might be used as a marker for ore exploration. A complete understanding of the formation of this pattern will contribute to a more accurate understanding of hydrothermal systems that build up economic mineralization.

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Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%

Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%

“…Once the loading-threshold of the reaction front is reached the collecting force of the front breaks down and the process switches to releasing particles [acc. [3]]. …”

Section: Dolomitization and Second-phase Redistributionmentioning

confidence: 99%