Thermodynamics of the natural assemblages of Ni-Co-Mn-Cu-Fe-Zn arsenates

• Applicant: Professor Juraj Majzlan, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 511078261

The first goal of the proposed work is the determination of thermodynamic properties of synthetic analogs of selected secondary minerals from Jáchymov. These are i) minerals of the krautite group [M(AsO3OH)·H2O minerals with M = Mn, Zn, Co, Mg, Ca, or Ca/Mn], ii) arsenates of the vivianite group [M3(AsO4)2·8H2O, where M = Ni, Co, Zn, Mg, Mn, Fe, and Cu], and iii) acidic ferric arsenate-sulfates kaatialaite [Fe(AsO2(OH)2)·5H2O] and sarmientite [Fe2(AsO4)(SO4)(OH)·5H2O]. Selected minerals from these groups will be synthesized and their thermodynamic properties determined by a combination of calorimetric techniques. The selection is based on the field work in the underground spaces in a historical Ag-Ni-Co-U(-As-Bi) ore deposit Jáchymov (Joachimsthal). The underground spaces of the historical Ag-Ni-Co-U(-As-Bi) deposit Jáchymov offer a natural laboratory with many local environments which we investigated in our previous work. The data obtained within the proposed work will be used to understand and numerically model the formation of the secondary minerals.The second goal of the project is the extension of applicability of a large thermodynamic data set for secondary minerals for temperatures between 0-200 oC. This work will be achieved by fitting the already existing data sets by a combination of Debye-Einstein functions, calculating the solubility constants at various temperatures using the appropriate software (SUPCRT) and tabulating the results. This work will allow the entire geochemical community to use the data to model any process involving many secondary arsenates, sulfates, or oxides.

• DFG Programme: Research Grants