Koděra, P.
1*, Takács, A.
2, Racek, M.
3, Šimko, F.
4, Luptáková, J.
5, Váczi, T.
2,6& Antal, P.
71Comenius University, Faculty of Natural Sciences, Department of Economic Geology, Slovakia; 2Eötvös Loránd University, Department of Mineralogy, Hungary; 3Charles University in Prague, Faculty of Science, Institute of Petrology and Structural Geology, Czech Republic; 4Slovak Academy of Sciences, Institute of Inorganic Chemistry, Slovakia; 5Earth Science Institute, Slovak Academy of Sciences, Slovakia; 6Hungarian Academy of Sciences, Institute of Solid State Physics and Optics, Hungary; 7 Department of Inorganic Chemistry Faculty of Science, Palacký University, Czech Republic; *kodera1@uniba.sk
Javorieite, KFeCl3, is a new mineral, commonly hosted by salt melt inclusions enclosed in vein quartz in the Biely Vrch porphyry gold deposit and several other porphyry gold systems in the Central Slovakia Volcanic Field in the Western Carpathians (Koděra et al., 2015, 2017). Salt melt inclusions represent a rare type of fluid inclusions, which have trapped a hypersaline liquid at high temperature.
The generation of the water-free salt melt with high concentrations of Fe and K is the result of quick expansion and cooling of magmatic fluids during their ascent from associated Fe-rich dioritic magma emplaced at shallow depth (Koděra et al., 2014). At room temperature salt melt inclusions do not contain any visible liquid phase, and the entire volume of the inclusions is occupied by several salt crystals and a distorted vapour bubble. Salt melt inclusions are found in shallow magmatic-hydrothermal systems, typically associated with Cu-Au porphyry mineralisation (e.g. Rottier et al., 2016). The mineral name refers to the Javorie stratovolcano, which hosts most porphyry gold systems in this volcanic field.
Within the inclusions, javorieite occurs in the form of small (up to 15 μm) green anhedral crystals with high relief. It is extremely hygroscopic and readily oxidised if exposed to the air. It is accompanied by several other daughter minerals, especially halite (NaCl), rinneite (NaK3FeCl6), chlorocalcite (KCaCl3), hibbingite, Fe2(OH)3Cl, unknown FeCl2
hydrate, fluorite, molybdenite and scheelite. The javorieite, as well as most of the other daughter minerals, were identified through comparison with the Raman spectra of the synthetic analogue, and through data obtained with the FIB-SEM-EBSD analytical technique. The combination of several independent analytical tools on three different inclusions proved the match in chemistry and crystallography of javorieite with synthetic KFeCl3. Javorieite is orthorhombic, the unit-cell parametres are a = 8.715(6) Å, b = 3.845(8) Å, c = 14.15(3) Å, V = 474.16(3) Å3, Z = 4. Furthermore, the experimental data in the NaCl–KCl–FeCl2 system agree with the microthermometric behaviour of javorieite. KFeCl3 (javorieite) and FeCl2 are the last phases in this system undergoing eutectic crystallisation at 309 °C or 319 °C (Robelin et al.,
2004), which corresponds to typical temperatures of first melting of the studied salt melt inclusions (320-338 °C). The presence of javorieite in three other localities in this volcanic field was confirmed by Raman spectroscopy. The distinctive Raman spectrum of javorieite (main bands at 66-69, 108-109, 119-120, 134-135, 235-237 cm-1) can help in future studies of salt melt inclusions worldwide, including a quick recognition of shallow porphyry systems that can be potentially enriched in gold.
Acknowledgement
This work was supported by the grants APVV-0537-10 VEGA-1/0560/15 and ITMS: 26220120064.
References
Koděra P. et al. (2014) Geology 42:495-498.
Koděra P. et al. (2015) in: ECROFI 2015:86-87.
Koděra P. et al. (2017) Eur. J. Mineral. 29:965-1004.
Robelin C. et al. (2004) Thermodyn. 36:809-828.
Rottier B. et al. (2016) Chem. Geol. 447:93-116.
How warm? An intercalibration of novel geothermometry methods for calcite Koltai, G.
1*, Krüger, Y.
2, Kluge, T.
3, Leél-Őssy, Sz.
4, Spötl, C.
1& Dublyansky, Y.
11Institute of Geology, University of Innsbruck, Austria; 2Department of Earth Science, University of Bergen, Norway; 3Institute of Environmental Physics, University of Heidelberg, Germany; 4Department of Physical and Applied Geology, Eötvös Loránd University; *gabriella.koltai@uibk.ac.at
Temperatures below ~55 oC represent a “blind spot” in classical paleo-geothermometry given the lack of available methods for measuring them. Yet, such temperatures are common in many subsurface environments including thermal groundwaters and shallow basinal fluids. Minerals crystallising from such waters may trap tiny amounts of them as fluid inclusions.
For several decades, the only available method to constrain the paleo-fluid´s temperature has been measurements of the liquid-vapour homogenisation temperature of primary fluid inclusions. Since two-phase inclusions mostly form when the entrapment temperature is ~55 oC or higher, assessing formation temperatures for minerals formed from cooler fluids has remained a challenge until recently, when a technological break-through has made it possible to measure homogenisation temperatures also in originally monophase fluid inclusions by laser-induced bubble nucleation (Krüger et al., 2007; Krüger et al., 2011).
During the last decade another novel method, clumped isotope thermometry of calcite, has been developed which offers high potential as a palaeo-thermometre over a wide temperature range (Affek et al., 2008; Kluge et al., 2015). As most of the current knowledge on clumped isotope systematics is based on theoretical and experimental studies of synthetic calcite, the intercalibration with other methods on natural samples is important (Came et al., 2017; Mangenot et al., 2017).
The aim of this study is to compare these two state-of-the-art analytical methods and investigate how well they compare for low-temperature environments. To this end, we collected hypogene calcite samples from different thermal karst areas of the Pannonian basin, where an earlier study demonstrated that the temperature of speleogenetic hydrothermal fluids varied between 35 and 95 oC (Dublyansky, 1995).
Optical microscopy shows that two-phase inclusions are present in the calcite samples from the Buda thermal karst area, while monophase liquid inclusions prevail in samples from Bükk Mts.
and Aggtelek Mts. The first results of clumped isotope thermometry indicate paleo-water temperatures of 10 to 100 oC for these calcite crystals. At this point, the results are preliminary and the analytical uncertainty may be as high as 10
oC.
So far, homogenisation temperatures have been measured on six monophase fluid inclusion assemblages after bubbles had been created by
femtosecond laser pulses. These results indicate that mineral crystallisation happened in the range of 10 to 34 oC. Clumped isotope analyses of the same calcite crystals yielded similar paleo-temperatures between 10 (±10) and 35 (±10) oC.
These initial results yielded by the two novel methods are comparable for all but one sample.
Acknowledgement
This project has been funded by the University of Innsbruck.
References
Affek H.P. et al. (2008) Geochim. Cosmochim. Ac.
72:5351-5360.
Came R.E. et al. (2017) Geochim. Cosmochim. Ac.
199:31-47.
Dublyansky Y.V. et. al. (1995) Environ. Geol. 25:24-35.
Kluge T. et. al. (2015) Geochim. Cosmochim. Ac.
157:213-227.
Krüger Y. et. al (2007) Eur. J. Mineral. 19:693-706.
Krüger Y. et. al (2011) Chem. Geol. 289:39-47.
Mangenot X. et al. (2017) Chem. Geol. 472:44-57.
Formation conditions of U-Ti-Metagel mineralisation in the Elkon Deposit (Yakut region, Russia)
Komarova, M.M.
1*, Aleshin, A.P.
1, Komarov, V.l.B.
1& Krylova, T.L.
11Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Russia;*ivanchenko.marija@gmail.com
The Elkon Au-U deposits are the most important reserve source of natural uranium in Russia. The Elkon Horst, hosting all uranium deposits of this region, extends to 60 km in the northeast direction with a width of 30 km.
The most productive for uranium is the Southern zone of the Proterozoic origination, was rejuvenated by the Mesozoic tectonic-magmatic activation (TMA). It controls five large-scale deposits (from NW to SE: Elkon, Elkon Plateau, Kurung, Neprohodimoe, Druzhnoe). The deposits are traced for 25 km along the Southern zone; the lower boundary of the mineralisation is not outlined down to the depth of 2 km. The mineralisation is complex with Au and Mo in some parts.
As it was reported before (Miguta, 2001) the ores are mainly composed of brannerite (UTi2O6).
However, fulfilled by authors study of uranium mineralisation under optical and scanning electron microscope showed that the bulk of the ore located in the Southern zone is composed an unknown amorphous polyphase U-Ti-metagel (UTM).
Consistent formation of phases with different U/Ti ratio indicates the primary nature of U-Ti-metagel, rather than the result of the metamict decomposition of brannerite. Crystalline brannerite was revealed in insignificant quantities formed simultaneously with UTM. It was suggested that the reason for the deposition of U minerals in both amorphous and crystalline forms is a wide temperature range of the hydrothermal process.
The fluid inclusions (FI) of pre-ore and post-ore stages have been studied. The pre-ore stage is represented by quartz, the post-ore – quartz and zonal veinlets of quartz, carbonate and fluorite.
Four types of the primary inclusions (5-20 μm) have been recognised at room temperature (21 C).
Type I is two-phase liquid-vapour aqueous inclusions. Type II is two-phase FI with vapour CO2. Type III is 3-phase FIs with liquid H2O, liquid CO2 and gas CO2 phases. Type IV contains phases from type III and solid phase.
A wide range of homogenisation temperatures (Th) of hydrothermal fluid (430-103 °C) has been revealed in the result of microthermometric study of FIs in minerals of pre-ore and post-ore stages.
Thom of FIs in the pre-ore quartz veins ranges 380-150 °C, and salinitiy matches 10-11 wt% eq. NaCl without CO2 and other gas admixture.
Parametres of the post-ore stage are more variable. Quarts Thom ranges 430-103 °C, high-temperature carbonate I Thom is 380-107 °C, late carbonate II Thom is <180 °C.
Microthermometric study of zonal quartz-carbonate-fluorite vein exhibits local temperature variations. The casing of vein is represented by quartz with Thomavg 233 °C (240-170 °C); the middle part with Thomavg 291 °C (380-197 °C) is made of carbonate; violet fluorite overlap carbonate in the central part and shows Thomavg 228 °C (424-140
°C).
FIs of the type III, IV are characterised by presence of crystalline hydrates up to 8.8 – 5.6 °C.
It is also possible to preserve the presence of a small amount of other gases, possibly CH4, which amount does not exceed 1-2 mol%.
Average temperatures, as well as temperature variation are similar for both pre-ore and post-ore stages. It allows to determine surely temperatures of uranium ore formation as 400-120 °C. Fluids possessed Na-chloride, rarely Na-chloride-carbonate composition and moderate salinity (6-16 wt% eq. NaCl). The wide range of temperatures confirms an assumption made before that various temperatures were the reason of formation of uranium mineralisation both in the form of predominantly amorphous phase (U-Ti-metagel), as well as in rarely crystalline form (brannerite).
Abrupt temperature decrease was apparently the main factor of ore deposition.
Acknowledgement
This study was supported by program no.0136-2018-0017.
References
Miguta A.K. (2001). Geol. Ore Deposit 43:117-135.
The ‘pargasosphere’ concept: the fluid-solid ‘ping-pong’ along major discontinuities of the shallow upper mantle and its bearing on global plate tectonics
Kovács, I.
1,2*, Berkesi, M.
1,3, Liptai, N.
1, Pálos, Zs.
1,3, Lange, T.P.
1,3, Szabó, Cs.
3, Szanyi, Gy.
1, Gráczer, Z.
1, Wéber, Z.
1, Novák, A.
1, Süle, B.
1, Timkó, M.
1, Czifra, T
1, Molnár, Cs.
1,
Patkó, L.
3, Aradi, L.E.
3, Szűcs, E.
1& Wesztergom, V.
11MTA CSFK Lendület Pannon LitH2Oscope Research Group, Hungary; 2MTA CSFK Geodetic and Geophysical Institute, Hungary; 3Lithosphere Fluid Research Lab, Eötvös Loránd University, Hungary;
*kovacs.istvan.janos@csfk.mta.hu
Water’ is an essential component of life, but also a vital one for making Earth a geologically ‘living’
planet. The principle of plate tectonics is that the Earth’s rigid outer shell, the lithosphere, ‘floats’ on the underlying less viscous asthenosphere. The reasons for their distinct physical properties are still unclear, therefore, the refined understanding of the lithosphere-asthenosphere boundary (LAB) and mid lithosphere discontinuities (MLDs) remains an important endeavor for the whole Earth Science community. The new ‘pargasosphere’ concept may offer an alternative model why minute amount of
‘water’ and its constitution in the Earth’s shallow upper mantle accounts for the changes in physical and geochemical properties at the LAB under young extensional basins and oceanic plates and at MLDs under older continental plates in ~100 km depth (Green et al., 2010; Kovács et al., 2017). The postulate of the idea is that the ‘water’ is stored in hydrous phases such as amphibole (pargasite) and nominally anhydrous minerals (NAMs) where pargasite is stable at temperatures less than ~1100
°C and at pressures less than ~ 3 GPa (~100 km).
In contrast, at temperatures and pressures exceeding these thresholds ‘water’ is usually present in NAMs and/or free fluid/melt phases.
Consequently ‘water’ changes its constitution in the upper mantle either being present in solid or fluid components of the upper mantle depending on the T conditions. This ‘ping-pong’ of ‘water’ in the P-T space of the upper mantle has a dramatic rheological impact. This is because ‘water’ in the stability field of pargasite is locked only in solid phases making the upper mantle rheologically stronger (i.e. Berkesi et al., 2019). In contrast where pargasitic amphibole is not stable ‘water’ is either present in the fluid phase or higher concentration in NAMs as structurally bound hydroxyl. This means that the upper mantle beyond the stability field of amphibole (pargasite) is less viscous and can be more easily deformable. We present micro- and nanoscale results how the
‘water’ hops in and off between solid and fluid states and how it may offer an alternative way to look at global plate tectonics.
Acknowledgement
This presentation was supported by the MTA CSFK Lendület Pannon LitH2Oscope project.
References
Berkesi et al. (2019) Chem. Geol. 508:182-196.
Green D.H. et al. (2010) Nature 467:448-451.
Kovács I. et al. (2017) Acta Geod. Geophys. 52:183-204.