Mechanisms of carbonate mineral formation – Experimental approaches

Almost 20% of Phanerozoic sedimentary rocks are comprised of carbonate minerals. Most of our knowledge of past climatic conditions stems from the analyses of trace elements and stable isotopes in carbonate minerals. The main focus of the group of Mineralogy and Hydrogeochemistry of TU Graz is to mechanistically describe the physicochemical parameters controlling

  • the chemical distribution of traces/impurities in carbonates and
  • the stable isotope composition of major and trace elements in carbonates.

Specific tasks can be seen in the following sections.

Incorporation of traces (Mg, Sr, Ba) during CaCO3 precipitation

Contact: Martin Dietzel

Stable isotope distribution of major elements during the formation of CaCO3, SrCO3 and BaCO3

Contact: Vassilis Mavromatis

Formation and Transformation of Amorphous calcium carbonate  and environmental proxies (Subproject of CHARON – DFG Forschergruppe 1644)

Calcium carbonate (CaCO3) minerals are very common and widespread in marine and terrestrial surroundings and are used in various industries (e.g. as fillers and pigments). The CaCO3 formation behavior depends on the present physicochemical conditions like temperature, pH, foreign inorganic cations (e.g. Mg2+) and organic additives (e.g. polyaspartic acid). Research focuses on providing quantitative data on carbonate precipitation using carefully designed experimental approaches.

The formation of amorphous calcium carbonate (ACC) and its transformation to crystalline calcium carbonate (e.g. (Mg-)calcite, aragonite) is a key process in the formation of many biominerals. However, there are still some unresolved questions about the mechanisms involved in the formation of the respective CaCO3 polymorph. The aim of this sub-project (CHARON) is to attain advanced knowledge about the distribution behavior of elements (e.g. Mg) and isotopes (e.g. 18O) during the formation and transformation of ACC. Therefore, ACC transformation experiments were carried out under precisely defined physicochemical conditions.

Link: TP1 - Experimental diagenesis (Subproject of CHARON – DFG Forschergruppe 1644)
Contact: Bettina Purgstaller

ACC act as a precursor of Mg-calcite that forms at a later stage in the experimental run. © TU Graz/IAG

ACC formation in the scope of tailored transformation

Amorphous calcium carbonate is an important precursor for biomineralization, but highly metastable with transformation to crystalline polymorphs of CaCO3 between minutes and few days, depending on synthesis and storage conditions. Therefore characterising the amorphous precursor phase and gathering information about parameters governing crystallization is challenging with respect to monitor this highly metastable phase respectively the fast transformation process.

The aim of this study is to find synthesis routes on how to obtain long-time metastable amorphous calcium carbonate and subsequently be able to decipher crystallization pathways leading to the respected calcium carbonate polymorphs.

Contact: Florian Konrad

The role of organics on the trace element uptake during CaCO3 precipitation (Calibration of elemental and isotope proxies by inorganic precipitation experiment)

The main task of this study is to develop proper proxy tools for the reconstruction of paleo-environmental conditions during the formation of biogenically induced carbonates. On that account the study focuses on the element partitioning and isotope fractionation processes in inorganic calcium carbonates precipitated under controlled laboratory conditions with and/or without the presence of selected organic substances.

The carbonate formation will be analyzed by using mineralogical and microstructural methods as well as elemental ratios, traditional and non-traditional stable isotopes, clumped isotopes and redox-sensitive elements. (Brachiopods as sensitive tracers of global marine Environment: Insights from alkaline, alkaline Earth metal, and metalloid trace element ratios and isotope systems)

Link:  BASE-LiNE Earth
Contact: Anja Füger

Oxygen and clumped  isotope fractionation during carbonate mineral formation

Contact: Martin Dietzel

Hydrothermal alteration of carbonate under diagenetic conditions

Vassilis Mavromatis
Isaac Kell Duivestein

Crystallization of carbonates and sulfides from aqueous solutions using CO2 diffusion technique

Contact: Martin Dietzel

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