Project Details
Projekt
The fate of light and mobile elements in magmatic-hydrothermal greisen systems – a combined study of minerals, fluids and gases
Subject Area
Mineralogy, Petrology and Geochemistry
Term
from 2020 to 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 441189074
The Variscan European Belt comprises numerous magmatic-hydrothermal greisen systems, which host significant Li, Sn, W and/or Mo resources. The Central Iberian zone (Portugal/Spain), Cornwall (UK), the Massif Central (France) and the Erzgebirge/Krušné Hory (Germany/Czech Republic) can be considered as Europe’s major Li-Sn-W provinces, of which the Erzgebirge system is exceptionally rich in Li. Although greisen deposits are known and mined for many centuries, many fundamental aspects such as the nature of greisen fluids (trace elements and gas components) and precise ore-forming mechanism that result in metal enrichment are not sufficiently understood. During the magmatic stage, fractional crystallization is a primary process which may result in strong enrichment of e.g. Li, Sn, B and F in the residual melt and the exsolved greisen fluid. Subsequently, water-rock interaction of these exsolved fluids along their flow path may alter their composition significantly - Elements may either be added or removed from the solution as a consequence of water-rock interaction (here: greisenization). Particularly dissolution of primary minerals (e.g. biotite) of the igneous and/or metamorphic host rock during early greisenization may increase Li, F, B and Sn concentrations of the fluid significantly, before these elements become ultimately removed from the fluid by precipitation of typical greisen minerals such as zinnwaldite, cassiterite, topaz, tourmaline and fluorite. The hydrothermal stage is thus of particular importance to decipher the fate of light and mobile elements in greisen systems.For a better understanding of element mobility during the hydrothermal stage of greisenization, we aim to combine in-situ geochemical analyses of greisen-related minerals (major, trace and isotope compositions with LA-ICPMS) with fluid inclusions (microthermometry, crush-leach analyses and LA-ICPMS) and gases (crush fast scan mass spectrometry). The understanding of a) trace and light element systematics of greisen minerals, b) the nature and evolution of greisen fluids and c) the role of gaseous components associated with these greisen fluids is vital to constrain the geochemical evolution of greisen systems in time and space. Furthermore, this combined and holistical approach will facilitate the identification of critical ore-forming processes and chemical mechanisms that cause major element enrichment (i.e. Li and Sn).
DFG Programme
Priority Programmes
Subproject of
SPP 2238:
Dynamics of Ore-Metals Enrichment - DOME
