CODES – Centre for Ore Deposit and Earth Sciences
PEGMATITES AND PEGMATITE-RELATED ORES
LEADER: | |||
Paul Davidson | |||
COLLABORATORS: | |||
Adolf Rericha Karen Appel Rainer Thomas Olaf Tietz | Consultant European XFEL, Germany Geoforschungszentrum Potsdam, Germany Senckenberg Research Institute, Germany |
PROJECT SUMMARY
2019
This initiative examines melt-melt immiscibility in felsic silicate melts, in the formation of pegmatites and pegmatite-related ore deposits. Pegmatites are noted for the presence of giant crystals, sometimes including rare minerals and gems, and are prime sources of several rare elements, even though their major element chemistry differs little from the standard haplogranitic melts, which are generally accepted to be their parental magmas. Therefore, it can be inferred that something in their origin favours extremely efficient partitioning, which would explain the high rare element concentrations (up to ore grade). Moreover, such processes need not be restricted to pegmatites, or even terrestrial processes.
We published two papers in 2019. ‘The enhanced element enrichment in the supercritical states of granite–pegmatite systems’ was published in Acta Geochimica, by Rainer Thomas, Paul Davidson and Karen Appel. In that paper we demonstrated that supercritical fluids have a greater significance in the generation of pegmatites, and for ore-forming processes related to granites, than is usually assumed.
During the year we also published a paper in the journal Berichte Der Naturforschenden Gesellschaft Der Oberlausitz, titled ‘Eine außergewöhnliche Einschlussparagenese im Quarz von Steinigtwolmsdorf/Oberlausitz’ by Rainer Thomas, Paul Davidson, Adolf Rericha and Olaf Tietz. The paper addresses the genesis of quartz veins in the Lausitz Block. Based on fluid and melt inclusions in the quartz of Steinigtwolmsdorf, the formation of this vein is attributed to magmatic, high-temperature hydrothermal fluids. During this process, two silicate melts with different water content are formed. A third paper, titled ‘Emerald from the Habachtal: New observations’, by Rainer Thomas, Paul Davidson, and Adolf Rericha, has been accepted for publication by Mineralogy and Petrology.
2018
This initiative examines melt-melt immiscibility in felsic silicate melts, in the formation of pegmatites and pegmatite-related ore deposits. Pegmatites are noted for the presence of giant crystals, sometimes including rare minerals and gems, and are prime sources of several rare elements, even though their major element chemistry differs little from the standard haplogranitic melts, which are generally accepted to be their parental magmas. Therefore, it can be inferred that something in their origin favours extremely efficient partitioning, which would explain the high rare element concentrations (up to ore grade). Moreover, such processes need not be restricted to pegmatites, or even terrestrial processes.
This year two papers – ‘Genetic significance of the 867 cm−1 out-of-plane Raman mode in graphite associated with V-bearing green grossular’ by Rainer Thomas, Adolf Rericha, Walter L. Pohl and Paul Davidson, and ‘Shaw meteorite: waterpoor and water-rich melt inclusions in olivine and enstatite’ by Rainer Thomas and Paul Davidson – have been published in Mineralogy and Petrology.
2017
This initiative examines melt-melt immiscibility in felsic silicate melts, in the formation of pegmatites and pegmatite-related ore deposits. Pegmatites are noted for the presence of giant crystals, sometimes including rare minerals and gems, and are prime sources of several rare elements, even though their major element chemistry differs little from the standard haplogranitic melts, which are generally accepted to be their parental magmas. Therefore, it can be inferred that something in their origin favours extremely efficient partitioning, which would explain the high rare element concentrations (up to ore grade). Moreover, such processes need not be restricted to pegmatites, or even terrestrial processes.
During the year, a paper was published in Mineralogy and Petrology entitled ‘Hingganite-(Y) from a small aplite vein in granodiorite from Oppach, Lusatian Mts., E-Germany’ by Rainer Thomas and Paul Davidson. Two more papers – ‘Genetic significance of the 867 cm−1 out-of-plane Raman mode in graphite associated with V-bearing green grossular’ by Rainer Thomas, Adolf Rericha, Walter L. Pohl and Paul Davidson, and ‘Shaw meteorite: water-poor and water-rich melt inclusions in olivine and enstatite’ by Rainer Thomas and Paul Davidson – have been accepted for publication in Mineralogy and Petrology.
2016
This new initiative is examining melt-melt immiscibility in felsic silicate melts, in the formation of pegmatites and pegmatite-related ore deposits. The work builds on the research conducted under the Melt-Melt Immiscibility and the Origin of Magnetite-Apatite Deposits project, which has now come to a conclusion.
Pegmatites are noted for the presence of giant crystals, sometimes including rare minerals and gems, even though their major element chemistry differs little from the standard haplogranitic melts, which are generally accepted as their parental magmas.
Therefore, it can be inferred that something in their origin favours extremely efficient partitioning, which would explain the high rare element concentrations (up to ore-grade). However, even in locations hosting pegmatite ore bodies, most pegmatites are barren. This leads to the conclusion that there are still many additional complexities to be unravelled through this research.
During the year, a paper was published in Ore Geology Reviews entitled ‘Revisiting complete miscibility between silicate melts and hydrous fluids, and the extreme enrichment of some elements in the supercritical state’. A second paper, entitled ‘Origin of miarolitic pegmatites in the Konigshain granite; Lusatia’, was published in Lithos. Both publications were authored by Rainer Thomas and Paul Davidson.