The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal... more The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal and an orthorhombic polymorph with disordered/ordered Al-Si distribution on the tetrahedral sites. Most of the natural cordierites are fully ordered. Six-membered rings of (Si,Al)O4 are piled in the direction of the crystallographic c-axis and form channels, laterally and vertically linked by additional (Al, Si) tetrahedrons. Mg and Fe in varying fractions occupy the octahedrally coordinated M-sites. CO2 and H2O (and other volatiles) can be incorporated into the structural channels, thus cordierite can be used for paleofluid reconstruction. The vibration energies of incorporated volatiles, their interaction with the lattice and variations of certain lattice-vibration energies caused by the Mg-Fe exchange can be determined with Raman spectroscopy, allowing chemical quantifications and structural investigations. A method for the semi-quantitative determination of CO2-contents of natural c...
The exploitation of copper deposits in the mountainous areas of the Alps gained enormous economic... more The exploitation of copper deposits in the mountainous areas of the Alps gained enormous economic importance particularly in the 2nd and 1st millennium B.C., as Alpine copper began to play a central role in the metal supply of Europe. This volume summarises the current state of research on prehistoric Alpine copper exploitation from the western and southern Alps to the gates of Vienna in the eastern Alps. The 23 papers were originally presented as contributions to a conference held in September 2016 at the University of Innsbruck, which covered topics such as mountain landscapes, mining, beneficiation, smelting and the metal trade in the Bronze and Early Iron Ages. A particular focus of the present volume is the D-A-CH-funded project on ‘Prehistoric copper production in the Eastern and Central Alps: technical, social and economic dynamics in space and time’, a research collaboration between partners in Germany, Austria and Switzerland. The various contributions provide new perspecti...
The lack of applicable geobarometers in many eclogite facies rocks led to the evaluation of the a... more The lack of applicable geobarometers in many eclogite facies rocks led to the evaluation of the assemblage K-feldspar-jadeite-quartz (KJQ) as a possible geobarometer in Chapter II. Use of appropriate mixing models to K-feldspar and jadeite solid solutions allowed application of the reaction albite = jadeite + quartz to the KJQ assemblage, which was used to constrain pressures and also a(H$\sb2$O) in eclogite facies metagranitic and metapelitic rocks from the Sesia-Lanzo Zone. Based on textural evidence and thermobarometric calculations the P-T conditions of five different stages of mineral growth in eclogites from Ianca Valley in the Sesia-Lanzo Zone were performed in Chapter III. It was possible to reconstruct a P-T-a(H$\sb2$O) path for these eclogites. The data show that the eclogites underwent a nearly isothermal decompressional path from 570-650$\sp\circ$C at 21 kbar to 500-600$\sp\circ$C at 11-13 kbar and finally to 300-500$\sp\circ$C and 3-7 kbar. During these stages, a(H$\sb2$O) remained relatively high (0.7-1.0). Piston-cylinder experiments on sodic amphiboles were undertaken in Chapters IV and V. Synthetic sodic amphiboles are displaced from stoichiometric glaucophane, and the glaucophane component increases with decreasing temperature and increasing pressure. The compositions of these amphiboles are comparable to those from ultra-high pressure rocks. Additional piston-cylinder experiments on the reaction 2 glaucophane = 4 jadeite + 3 enstatite + 2 coesite + 2 H$\sb2$O were undertaken in Chapter V. They yielded a bracket between 37 and 38 kbar at 800$\sp\circ$C which allowed the calculation a $\Delta$G$\sp\circ\sb{\rm f,298}$ for glaucophane. The resulting $\Delta$G$\sp\circ\sb{\rm f,298}$ is -11253 $\pm$ 2 kJ/mol, 5-20 kJ/mol more negative than previous estimates. An experimental investigation on the synthesis of F-Al-sphene (CaAlSiO$\sb4$F), which yielded Al contents of 50 to 98 mol percent, was performed in Chapter VI. No significant pressure or temperature dependency of the (Al + F) substitution could be found. Activity measurements by dilution of the reaction anorthite + rutile = sphene + kyanite with fluorite revealed only a slight non-ideality in the system CaTiSiO$\sb5$ CaAlSiO$\sb4$F at 1000$\sp\circ$C and 1100$\sp\circ$C. These preliminary data strongly support the use of a molecular mixing model for sphene.Ph.D.Earth SciencesGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131559/2/9910011.pd
ABSTRACT Monomineralic Fe-Zn tetrahedrite-tennantite (fahlore) veins from the historic silver min... more ABSTRACT Monomineralic Fe-Zn tetrahedrite-tennantite (fahlore) veins from the historic silver mines of Brixlegg in the Inn Valley (North Tyrol, Austria) show replacement textures containing a newly formed mineral assemblage (enargite/luzonite-famatinite + chalcostibite + pyrite + sphalerite ± stibnite), resulting from fahlore breakdown. In order to deduce the T-logf S2 conditions of this reaction, appropriate mineral equilibria in the Cu-Fe-Sb-S and Cu-Zn-Sb-S systems were calculated using available thermochemical data.The lack of thermochemical properties of famatinite (Cu3SbS4) made it necessary to perform a theoretical approximation, which yielded ΔG298 f of −402.25 kJ mol−1. This estimate was combined with thermochemical data of all other phases from the available literature. In the T-logf S2 space, phase equilibria indicate that risingf S2 and/or dropping T lead to the breakdown of Fe-Zn tetrahedritetennantite. However, uncertainties stemming from the theoretically estimated thermochemical properties of famatinite place the calculated reactions near or above the S2 condensation curve. Adjusting ΔG298 f of famatinite to 3–5 % more negative ΔG298 f values shifts the reactions towards reasonable conditions, and places the stability fields of the observed mineral assemblages within the T-logf S2 window estimated by independent methods.This study therefore indicates that combination of existing thermochemical data and detailed mineralogical and petrological investigations on natural enargite/luzonite-famatinite-bearing assemblages may lead to meaningful T-logf S2 estimates. However, more experimental data on the thermochemical properties of famatinite are clearly needed.
The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal... more The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal and an orthorhombic polymorph with disordered/ordered Al-Si distribution on the tetrahedral sites. Most of the natural cordierites are fully ordered. Six-membered rings of (Si,Al)O4 are piled in the direction of the crystallographic c-axis and form channels, laterally and vertically linked by additional (Al, Si) tetrahedrons. Mg and Fe in varying fractions occupy the octahedrally coordinated M-sites. CO2 and H2O (and other volatiles) can be incorporated into the structural channels, thus cordierite can be used for paleofluid reconstruction. The vibration energies of incorporated volatiles, their interaction with the lattice and variations of certain lattice-vibration energies caused by the Mg-Fe exchange can be determined with Raman spectroscopy, allowing chemical quantifications and structural investigations. A method for the semi-quantitative determination of CO2-contents of natural c...
The exploitation of copper deposits in the mountainous areas of the Alps gained enormous economic... more The exploitation of copper deposits in the mountainous areas of the Alps gained enormous economic importance particularly in the 2nd and 1st millennium B.C., as Alpine copper began to play a central role in the metal supply of Europe. This volume summarises the current state of research on prehistoric Alpine copper exploitation from the western and southern Alps to the gates of Vienna in the eastern Alps. The 23 papers were originally presented as contributions to a conference held in September 2016 at the University of Innsbruck, which covered topics such as mountain landscapes, mining, beneficiation, smelting and the metal trade in the Bronze and Early Iron Ages. A particular focus of the present volume is the D-A-CH-funded project on ‘Prehistoric copper production in the Eastern and Central Alps: technical, social and economic dynamics in space and time’, a research collaboration between partners in Germany, Austria and Switzerland. The various contributions provide new perspecti...
The lack of applicable geobarometers in many eclogite facies rocks led to the evaluation of the a... more The lack of applicable geobarometers in many eclogite facies rocks led to the evaluation of the assemblage K-feldspar-jadeite-quartz (KJQ) as a possible geobarometer in Chapter II. Use of appropriate mixing models to K-feldspar and jadeite solid solutions allowed application of the reaction albite = jadeite + quartz to the KJQ assemblage, which was used to constrain pressures and also a(H$\sb2$O) in eclogite facies metagranitic and metapelitic rocks from the Sesia-Lanzo Zone. Based on textural evidence and thermobarometric calculations the P-T conditions of five different stages of mineral growth in eclogites from Ianca Valley in the Sesia-Lanzo Zone were performed in Chapter III. It was possible to reconstruct a P-T-a(H$\sb2$O) path for these eclogites. The data show that the eclogites underwent a nearly isothermal decompressional path from 570-650$\sp\circ$C at 21 kbar to 500-600$\sp\circ$C at 11-13 kbar and finally to 300-500$\sp\circ$C and 3-7 kbar. During these stages, a(H$\sb2$O) remained relatively high (0.7-1.0). Piston-cylinder experiments on sodic amphiboles were undertaken in Chapters IV and V. Synthetic sodic amphiboles are displaced from stoichiometric glaucophane, and the glaucophane component increases with decreasing temperature and increasing pressure. The compositions of these amphiboles are comparable to those from ultra-high pressure rocks. Additional piston-cylinder experiments on the reaction 2 glaucophane = 4 jadeite + 3 enstatite + 2 coesite + 2 H$\sb2$O were undertaken in Chapter V. They yielded a bracket between 37 and 38 kbar at 800$\sp\circ$C which allowed the calculation a $\Delta$G$\sp\circ\sb{\rm f,298}$ for glaucophane. The resulting $\Delta$G$\sp\circ\sb{\rm f,298}$ is -11253 $\pm$ 2 kJ/mol, 5-20 kJ/mol more negative than previous estimates. An experimental investigation on the synthesis of F-Al-sphene (CaAlSiO$\sb4$F), which yielded Al contents of 50 to 98 mol percent, was performed in Chapter VI. No significant pressure or temperature dependency of the (Al + F) substitution could be found. Activity measurements by dilution of the reaction anorthite + rutile = sphene + kyanite with fluorite revealed only a slight non-ideality in the system CaTiSiO$\sb5$ CaAlSiO$\sb4$F at 1000$\sp\circ$C and 1100$\sp\circ$C. These preliminary data strongly support the use of a molecular mixing model for sphene.Ph.D.Earth SciencesGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131559/2/9910011.pd
ABSTRACT Monomineralic Fe-Zn tetrahedrite-tennantite (fahlore) veins from the historic silver min... more ABSTRACT Monomineralic Fe-Zn tetrahedrite-tennantite (fahlore) veins from the historic silver mines of Brixlegg in the Inn Valley (North Tyrol, Austria) show replacement textures containing a newly formed mineral assemblage (enargite/luzonite-famatinite + chalcostibite + pyrite + sphalerite ± stibnite), resulting from fahlore breakdown. In order to deduce the T-logf S2 conditions of this reaction, appropriate mineral equilibria in the Cu-Fe-Sb-S and Cu-Zn-Sb-S systems were calculated using available thermochemical data.The lack of thermochemical properties of famatinite (Cu3SbS4) made it necessary to perform a theoretical approximation, which yielded ΔG298 f of −402.25 kJ mol−1. This estimate was combined with thermochemical data of all other phases from the available literature. In the T-logf S2 space, phase equilibria indicate that risingf S2 and/or dropping T lead to the breakdown of Fe-Zn tetrahedritetennantite. However, uncertainties stemming from the theoretically estimated thermochemical properties of famatinite place the calculated reactions near or above the S2 condensation curve. Adjusting ΔG298 f of famatinite to 3–5 % more negative ΔG298 f values shifts the reactions towards reasonable conditions, and places the stability fields of the observed mineral assemblages within the T-logf S2 window estimated by independent methods.This study therefore indicates that combination of existing thermochemical data and detailed mineralogical and petrological investigations on natural enargite/luzonite-famatinite-bearing assemblages may lead to meaningful T-logf S2 estimates. However, more experimental data on the thermochemical properties of famatinite are clearly needed.
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