5. Mineralogy

5.1. Mineralogy and its applications

ORAL PRESENTATIONS

Occurrence of indium with late-stage intrusions in the Kymi granite stock, Southern Finland

Thair Al-Ani1, Timo Ahtola1 and Janne Kuusela1
1Geological Survey of Finland
The Kymi granite stock contains hydrothermal greisen and quartz vein type F––Sn and Zn–– Pb––Cu sulphide mineralization. These intrusions are enriched in indium and rare earth elements, roquesite (CuInS2) being a major indium-carrier. The accessory minerals are fluorite, zircon, apatite, cassiterite and different sulphides, such as sphalerite, chalcopyrite and galena. The indium and REE-bearing mineral assemblages were studied by a combination of optical and field emission scanning electron microscopy (FE-SEM) and electron probe micro-analyzer (EPMA) techniques. Roquesite occurs as microscopic grains (10–40 micron) in galena. EPMA analyses of these grains yield an average composition of 26.16% S, 0.02% Fe, 25.06% Cu, 0.03% Zn, 1.06% As, 0.31% Sb and 47.14% In. Indium incorporation into the galena structure probably occurred according to the relation Pb2+S2-↔Cu+In3+S2-, whereas zinc present in the galena was probably replaced by indium. Therefore coupled substitution 2(Pb2+ Zn+) = Cu+In3+ may also have occurred.

References

Al Ani, T., Ahtola T., & Kuusela, J. Mineralogical and petrographic characteristics of indium and REE-bearing accessory phases in the Kymi granite stock, southern Finland. Geology of ore deposits ( In press ).

The fumarolic minerals of the Fimmvörduhals 2010 eruption

Tonci Balic-Zunic1, Kristjan Jonasson2 and Anna Katerinopoulou3
1Department of Geosciences and Natural Resource Management, University of Copenhagen, 2Icelandic Institute of Natural History, 3Haldor Topsøe A/S
The eruption at Fimmvörduhals, Iceland, lasted from March to April 2010 followed by the well-known Eyjafjallajökul explosion. It formed two craters, Magni and Móði and expelled a substantial amount of volcanic gasses.

The samples of fumarolic minerals were collected in three campaigns in 2010, followed by two in subsequent years. The locality temperatures ranged from around 50 to almost 800oC.

The mineral parageneses can be divided in five main types:

1) Aluminofluorides and silicofluorides of Na, Mg and Ca, including two recently described new minerals characteristic for Icelandic fumaroles, plus two new minerals under investigation. They are characteristic for sites with lower formation temperature (<200oC) found south from craters, outer rim of Magni and north from Móði crater.

2) Halite-dominated associations. They include both low-temperature associations (<100oC) with hydrous sulfates found south of craters, and occurrences at high-temperature fumaroles (>500oC) in the northern part of Magni crater.

3) Anhydrous and hydrous sulfates characteristic for low to medium-temperature fumaroles (<300oC) occurring south of craters and on Móði. They are represented by various Na-K-Mg-Ca-Al phases, two of them new species.

4) High-temperature Na-K sulfates found at temperatures >600oC on the rim of the Magni crater and in one crevice south from crater.

5) Other high-temperature Na, K, Mg and Ca sulfates forming at similar temperature conditions as 4) and also found on the rim of Magni crater.

Exceptional for Fimmvörduhals fumaroles is that the high-temperature sites contain acidic K and Na hydrogen sulfates mercalite (KHSO4) and a new mineral with composition Na3H(SO4)2.

Element mobility and new paragenses of the Ivigtut cryolite deposit, South Greenland

Henrik Friis1
1Natural History Museum, University of Oslo, P.O. 1172, Blindern, 0318 Oslo, Norway
The Ivittuut, formerly Ivigtut, cryolite deposit has been known since the late 18th century as a source of unique minerals in particular fluorides of which cryolite was mined for almost 100 years. The majority of scientific publications about Ivittuut have focused on the formation of the deposits, the fluorides or the sulphides. However, little is known about the alteration mineralogy and consequently element mobility in this unique fluorine-rich environment.

A fieldtrip to Ivittuut in the summer 2016 specifically targeted various paragenesis showing signs of alteration. Consequently, we have discovered 11 minerals new for Ivittuut including a series of alteration stages of primary sulphides and the first Rare Earth Element (REE) paragenesis.

Galena is one of the main sulphide minerals and to date only cerussite (PbCO3) and wulfenite (PbMoO4) are known secondary Pb-minerals at ivigtut. However, new types of galena alteration have been observed consisting of Pb-chlorides and carbonates (cotunnite, PbCl2, and phosgenite, Pb2CO3Cl2) and sulphates (anglesite, PbSO4, and linarite, PbCu(SO4)(OH)2) and at places native sulphur. The source of chlorine is likely to be the Arsuk fjord, bordering the deposit. The presence of S in three oxidations states reveals a progressive oxidation event at places, but also subtle variations in secondary mineralogy within the same sample. A similar oxidation situation has been observed for S and As in arsenopyrite (FeAsS), which is being replaced by kaňkite (FeAsO4·3.5H2O) and native sulphur.

Nanoscale observations of ‘invisible gold’ from the Olympias mine, Greece

Takeshi Kasama1, Platon N. Gamaletsos1, Stephane Escrig2, Berit Wenzell1, Louise H.S. Jensen2, Anders Meibom2, Dimosthenis Sokaras3, Tsu-Chien Weng3, Dimitrios Dimitriadis4 and Athanasios Godelitsas5
1Technical University of Denmark, Kongens Lyngby, Denmark, 2École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3SLAC National Accelerator Laboratory, CA, USA, 4Hellas GOLD S.A., Athens & Chalkidiki, Greece, 5National & Kapodistrian University of Athens, Athens, Greece
In some gold deposits, gold exists as invisible form in pyrite or arsenopyrite. Such gold is not recovered readily from ore materials. The identification of the gold form and distribution may provide some insight into the recovery of gold. Here, we use electron microscopy, NanoSIMS and high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) to investigate ‘invisible gold’ from the Olympias Au-Ag-Pb-Zn polymetallic carbonate replacement deposit, northern Greece.

Bulk analyses show that given ore samples contain gold up to ~30 ppmw and gold has positive relationships with arsenopyrite and probably As-containing pyrite. The arsenopyrite and pyrite make up 15% and 19% of the samples, respectively. Assuming that all the gold is accumulated in arsenopyrite, each arsenopyrite grain would contain ~200 ppmw. NanoSIMS suggests that gold is present primarily in arsenopyrite and is distributed with large variations along the growth direction. Pyrite also contains some gold but the concentration is even lower than that in arsenopyrite. TEM was used to examine the near-surface of arsenopyrite, where gold is usually concentrated. However, no gold precipitates were observed, which might suggest that gold is present in the form of ions in either the crystal lattice or interstitial position. This result is also supported from the HERFD-XAS study, in which gold is likely present as a higher oxidation state (e.g., Au3+) occurring as a chemically bound form in the structure. Thus, gold may have been incorporated into arsenopyrite and pyrite during relatively rapid growth of them.

Plasticite, (Plas-TI-Kite) an ore mineralization from the late Anthropocine

Erik Nilsson1
1Luleå Technical University/Oulu University
The Late Anthropocine has caused a noticeable shift in the ability for new minerals to form via human mechanisms. One such mineral, plasticite, is a relatively abundant mineral at Earth’s surface

deriving from plastic. The general chemical formula for plasticite and all plasticite like minerals (with a plastic provinance) are: (Contact author for better formatting)

\centerline{$(C_{2}H_{4})_{n}\pm(F^{-},Cl^{-},Br^{-},I^{-})\pm(Pb,Sn)$}

The discussions in the last chapter details a proposal for mineralis, a new mineral category taking into account the prospect of anthropogenic minerals having a class of their own to accommodate for the potentials of the rapidly increasing carbon mineral category.

POSTER PRESENTATIONS

Prediction of swelling potential using the Atterberg limits

Aikaterini Biotaki1, Irene Rocchi1, Jeppe Bendix Regel2 and Helle Foged Christensen2
1Technical University of Denmark (DTU), 2GEO
Expansive soils are known to cause numerous problems on surface and underground constructions. In the oil and gas industry, they may cause operational problems during drilling and completion, workover, production, and stimulation procedures. The use of water-based mud during drilling operations can cause clay swelling and consequently wellbore instabilities that, in extreme cases, could lead to complete well abandonment. Moreover, swelling clays can affect the quality of the reservoir and lead to problems during the conventional hydrocarbon production, or Enhanced Oil Recovery (EOR). Therefore, to avoid serious complications and excessive operational costs in the case of hydrocarbon operations, it is of high importance to fully understand the behaviour of swelling clay and quantify the volume change, linking it to the mineralogy.

Throughout the years, several researchers studied the correlation between the Atterberg limits and the swelling potential or swelling pressure of soils providing numerous empirical correlations. During this study, data acquired from 12 different publications were examined to determine whether there is a correlation between the Plasticity Index (PI) and the Swelling potential (SP) for varying samples and methodologies. A linear correlation between the SI and PI was found, with a coefficient of determination (R2) = 0.731, which is rather satisfactory given the different methodologies and soil conditions used. The influence of the mineralogy was assessed using the Casagrande chart and it was found that the montmorillonitic samples resulted in a significantly higher coefficient of determination.

References

Anderson R.L., Ratcliffe I., Greenwell H.C., Williams P.A., Cliffe S., and Coveney P.V. (2010). Clay swelling — A challenge in the oilfield. Earth Science Reviews, Vol. 98, Issue 3, 201-216.

Bowles J. E. (1996). Foundation Analysis and Design, 5th Ed., McGraw-Hill, New York, pp. 1175.

Cheshomi A., Eshaghi A., and Hassanpour J. (2017). Effect of lime and fly ash on swelling percentage and Atterberg limits of sulfate-bearing clay. Applied Clay Science, Vol.135, 190–198.

Çimen Ö., Keskin S.N., and Yıldırım H (2012). Prediction of swelling potential and pressure in compacted clay. Arabian Journal for Science and Engineering, Vol. 37, Issue 6, 1535–1546.

Elarabi H. (2005).Evaluation of the predicted equations for swelling potential. Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka, Japan.

Erguler Z.A., and Ulusay R. (2003). A simple test and predictive models for assessing swell potential of Ankara (Turkey) Clay. Engineering Geology, Vol. 67, Issues 3–4, 331–352.

Holtz R.D., and Kovacs W.D. (1981). An Introduction to Geotechnical Engineering. Englewood Cliffs, N.J., Prentice-Hall, pp. 723.

Krueger R.F. (1986). An overview of formation damage and well productivity in oilfield operations. Journal of Petroleum Technology, Vol. 38, Issue 2, 131-152.

Mitchell J.K, and Soga K. (2005). Fundamentals of Soil Behavior. 3rd Ed., John Wiley & Sons, Hoboken, New Jersey, pp. 529.

Mohamed A.E.M.K. (2013). Improvement of swelling clay properties using hay fibers. Construction and Building Materials, Vol. 38, 242-247.

Selmer-Olsen R., and Palmstrom A. (1989). Tunnel collapses in swelling clay zones. Tunnels & Tunnelling, Vol. 21, Issue 11, 49-51.

Sivapullaiah P.V., Sridharan Α., Stalin V.K. (1996). Swelling behaviour of soil-bentonite mixtures. Canadian Geotechnical Journal, Vol. 33, Issue 5, 808-814.

Wilson M.J. and Wilson L. (2014). Clay mineralogy and shale instability: an alternative conceptual analysis. Clay Minerals, Vol. 49, Issue 2, 127-145.

Zhou Z., Gunter W.D., Kadatz B., and Cameron S. (1996). Effect of clay swelling on reservoir quality. Journal of Canadian Petroleum Technology, Vol. 35, Issue 7, 18-23.

A new single-crystal XRD for mineral sciences in Scandinavia

Henrik Friis1
1Natural History Museum, University of Oslo, P.O. 1172, Blindern, 0318 Oslo, Norway
The natural history museum in Oslo has purchased a state of the art single-crystal XRD, which is dedicated to mineral sciences. The instrument is a Rigaku Synergy-S dual-beam instrument equipped with Mo and Cu μ-sources and a HyPix-6000HE hybrid photon counting area detector. The instrument comes with various options for Gandolfi movement making it ideal for mineral identification of minute grains and aggregates as well as powders. The Gandolfi data can be exported in various file-formats making it importable into a range of other software used for traditional powder XRD search and match functions.

The high-intensity μ-sources combined with the fast detector read-out time makes it possible to collect data rapidly. The Cu-source is more intense than the Mo-source, which is particularly beneficial for data collection of low absorbent materials and the Gandolfi methodology. The software controlling the instrument (CrysAlis Pro) is combined with on-site license of AutoChem, which makes it possible to solve structures while data is collecting. This function combined with the high-intensity sources and fast detector enables rapid screening of crystals to identify the best suitable for full data collection. The software handles up to eight twins or intergrowth domains for full structure determination. The software for data reduction and face indexing can be downloaded for free and consequently all data processing can be carried out off-site.

The instrument should be installed in spring 2018 and we invite users from the mineralogy community in Scandinavia to come to Oslo for their single-crystal diffraction work.

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