Tectonic-controlled sediment-hosted fluorite-barite deposits of the central Alpine-Himalayan segment, Komsheche, NE Isfahan, Central Iran

Timing of fluorite mineralization and exhumation events in the east Central Alborz Mountains, northern Iran: constraints from fluorite (U–Th)/He thermochronometry

“…research report, Golestan University, Gorgan, Iran, 2016). Similar hydrothermal fluid conditions have been reported from the Illinois–Kentucky fluorspar district in the USA and the South Pennine Orefield in England (Chesley et al 1994; Bau et al 2003; Barker et al 2009) as well as fluorite-barite Komsheche deposit in Central Iran (Alaminia et al 2021).…”

“…The Late Cretaceous FHe ages of c. 85–72 Ma can be considered as mineralization ages for the MFMD, and could be explained by a genetic scenario proposed for similar fluorite mining districts around the world (the Illinois–Kentucky fluorspar district in the USA and the South Pennine ore field in England), where mineralization was formed by basinal brine fluid flow a few million years after the formation of the carbonate host rocks (Chesley et al 1994; Bau et al 2003). The migration of the ore-forming basinal fluids at shallow crustal levels could have been driven by magmatic or orogenic events that can generate thermally and tectonically driven fluid flow, respectively (Garven et al 1993; Garven & Raffensperger, 1997; Leach et al 2005; Pollyea et al 2015; Bahnan et al 2020; Alaminia et al 2021). In the absence of orogenic process around the time of fluorite mineralization in the Alborz Mountains, burial heating plus magmatic heat flow (Nazari & Shahidi, 2012; Shekarifard et al 2012) could have resulted in basinal brine circulation and the formation of hydrothermal ore solution.…”

“…M.Sc. thesis, Tehran University, Tehran, Iran, 1997) and also fluorite-rich MVT deposits around the world (mostly 90–150°C; Leach et al 1997, 2005; Wilkinson, 2014; Alaminia et al 2021).…”

“…The epigenetic origin for fluorite mineralization by hydrothermal ore fluids originated from basinal brine during the Late Cretaceous Epoch in the MFMD, similar to the Illinois–Kentucky fluorspar district in the USA and South Pennine Orefield in England (Chesley et al 1994; Bau et al 2003) as well as in the fluorite-barite Komsheche deposit in Central Iran (Alaminia et al 2021), is also supported by: (1) highly variable ∑REE+Y concentrations; the hydrothermal signature of Y/Ho ratios and the positive Y anomalies of dated fluorite samples in this study indicate prolonged circulation and long migration pathway for the ore-forming solution (Jiang et al 2005; Jian et al 2015); (2) the heterogeneous Sr–Nd–Pb isotopic composition of fluorite, indicating the origin of the ore-forming elements as source rocks with different isotopic compositions; and (3) the moderate temperature and low salinity of fluorite-hosted fluid inclusions.…”

“…This method has been developed and validated by Wolff (2015) and Wolff et al (2015, 2016) as a new geo- and thermochronometer for dating hydrothermal mineralization, as well as subsequent low-temperature thermal events that may reset the FHe system. Recently, Alaminia et al (2021) used fluorite thermochronometry in a Triassic carbonate-hosted fluorite-rich Mississippi-Valley-type (MVT) deposit in Central Iran. The very scattered FHe ages were interpreted without their uncertainty (437.6–4.6 Ma) as formation ages of fluorite during multiple mineralization events.…”