Rohstoffe

• Prof. Dr. Hartwig E. Frimmel
• Dr. Alexander Kawohl
• BSc hons., P.Geo. Wesley E. Whymark (Inventus Mining Corp., Toronto)
• BSc, P.Geo. Andrejs Bite (Bite Geological Ltd., Sudbury)

Project duration: 2016 - 2022

Funding (2019 - 2022): German Research Foundation (DFG) Project number 418960271

Funding (2016 - 2018): Canadian Continental Exploration Corp., Toronto

Summary:

This project attempts to explain the ultimate geological cause of one of the largest, hitherto unexplained, magnetic anomalies in North America, the Temagami geophysical anomaly in Ontario, Canada. The anomaly is of outstanding scientific and economic interest because it is directly adjacent to the 1.85 Ga Sudbury Complex - the second largest impact structure on Earth and one of the world’s richest mining districts thanks to widespread Ni-Cu-PGE-sulfide mineralization. The Temagami Anomaly mirrors the magnetic anomaly caused by the Sudbury Complex in terms of shape, size and intensity. Lack of outcrops and, until recently, of bore holes, prevented a proper geological understanding, and whatever genetic link with the Sudbury Complex has remained pure speculation. Preliminary petrological studies by the applicant and the anticipated project scientist (PhD student) on the first deep drill hole sunk into the centre of the Temagami Anomaly revealed the presence of dioritic rocks at 2 km depth, which bear similarities with offset dykes in and around the Sudbury Complex. This raises the possibility of a genetic link with the Sudbury impact event, which if proved correct, would open up an entirely new perspective on our understanding of the Sudbury Complex and its exploration potential. Thus, the principal aim of this project is to test for such a genetic link and to provide a geological explanation for the geophysical anomaly by comparing new data on the petrology, alteration history, geochemistry, isotopic composition and geochronology to be acquired from drill core and surface samples from the area of the Temagami Anomaly with available data on the Sudbury Complex and potentially equivalent rocks in the wider region. This will include layered mafic and ultramafic intrusions, mafic dyke swarms, carbonatite stocks, and sedimentary iron formations, all of which occur in the area, bear significant economic potential, and could be possible candidates for the observed magnetic anomaly. Our preliminary observations revealed also widespread hydrothermal alteration and brecciation, whose origin and bearing on the magnetic anomaly is unclear. Thus, a further goal of the project will be to characterize this alteration and to establish its significance in terms of the cause of the Temagami Anomaly, the genesis of the Sudbury structure and the metallogeny of the area.

Publications:

Kawohl, A., Frimmel, H.E., Whymark, W.E., Millonig, L.J. and Gerdes, A., 2022. Geology, geochemistry, and apatite/titanite U-Pb geochronology of ca. 1.88 Ga alkaline ultrabasic dykes in the Southern Province near Sudbury, Ontario. Canadian Journal of Earth Sciences, in press.

Kawohl, A., Whymark, W.E., Bite, A. and Frimmel, H.E., 2020. High-Grade Magmatic Platinum Group Element-Cu(-Ni) Sulfide Mineralization Associated with the Rathbun Offset Dike of the Sudbury Igneous Complex (Ontario, Canada). Economic Geology, 115, pp.505-525.

Kawohl, A., Frimmel, H.E., Whymark, W. and Bite, A., 2019. Rathbun Lake revisited: a magmatic-hydrothermal Pd-Pt-Cu occurrence possibly related to the Sudbury impact. Proceedings of the 15th biennial SGA meeting, Glasgow,  Volume 2, pp. 605-608.

Kawohl, A., Frimmel, H.E., Bite, A., Whymark, W. and Debaille, V., 2019. Very distant Sudbury impact dykes revealed by drilling the Temagami geophysical anomaly. Precambrian Research, 324, pp.220-235.

Kawohl, A., Frimmel, H.E., Bite, A. and Whymark, W., 2017. What’s inside the Temagami geophysical anomaly, Sudbury district, Ontario?. Proceedings of the 14th biennial SGA meeting, Quebec, Volume 4, pp.1543-1546.

• Prof. Dr. Hartwig E. Frimmel
• Dr. Stefan Höhn
• Dr. Vinciane Debaille (Free University of Brussels) 

Project duration: since 2017

Supported by the Faculty of Philosophy, University of Wuerzburg 

Summary: 

The determination of the so called “no-traditional” stable isotopes ⁶³Cu and ⁶⁵Cu became a useful and widely used tool in the field of ore geology in the last years. Nevertheless, the influence of metamorphism on the Cu-isotope ratio is still unclear. In this study, we compare the ⁶⁵Cu/⁶³Cu isotope ratios of several sedimentary-exhalative deposits from all over the world to their respective metamorphic grade to determine the effects of this overprint. To eliminate interference with other factors controlling the Cu-isotope ratios we concentrate our research on deposits, which reveal a maximum of (primary) similarity except from their metamorphic grade. 

Publications:

Höhn, S., Frimmel, H.E., Debaille, V., 2019. Pre-metamorphic oxidation of the Broken Hill deposit at Aggeneys (South Africa) revealed by Cu isotopes. Proceedings of the 15th Biennial SGA meeting, Glasgow, Volume 3, pp. 1212-1215.

Höhn, S., Frimmel, H.E., Debaille, V., Pasava, J., Kuulmann, L., Debouge, W., 2017. The case for metamorphic base metal mineralization: pyrite chemical, Cu and S isotope data from the Cu-Zn deposit at Kupferberg in Bavaria, Germany. Mineralium Deposita 52:1145–1156.

• Prof. Dr. Hartwig E. Frimmel
• BSc hons., P.Geo. Wesley Whymark (Inventus Mining Corp., Toronto)

Project duration: since 2015

Funded by Inventus Mining Corp.

Summary:

The 2.45 to 2.2 Ga Huronian Basin in Ontario, Canada, has been thought to contain many similarities with the famous Witwatersrand goldfields in South Africa. Recent discoveries suggest the Huronian Basin may contain Witwatersrand-type gold deposits. The gold mineralization has been discovered within separate conglomeratic stratigraphy of both the Mississagi and Matinenda formations. These discoveries have developed into what is now known as the Pardo project in Pardo Township 65 km northeast of the famous Sudbury mining camp. The basal Mississagi cobble to boulder conglomerates can contain values up to 542 g/t Au. The Pardo project is located in the eastern portion of the Huronian Basin known as the Southern Cobalt Embayment. The western portion of the basin, which is most analogous to the Witwatersrand, is historically known for its uraniferous quartz- pebble conglomerates of the Matinenda Formation at Elliot Lake. This investigation plans to examine and compare the mineralogy, chemistry and distribution of gold in both the Mississagi and Matinenda Formations. This will provide insight as to the reasons for gold occurring in the Matinenda Formation at Pardo, which is not seen elsewhere in the basin. The study will also examine the Mississagi sedimentary environment and study its provenance, by examining a comprehensive selection of clasts to determine their source(s) and whether they contributed gold to the Mississagi Formation. Detailed lithofacies analysis of both diamond drill core and outcrop exposures will provide valuable information regarding the channelized nature of the conglomerates as well as to provide a framework for gold resource analysis.

Publications:

Whymark, W.E., Frimmel, H.E., 2018. Regional gold-enrichment of conglomerates in Paleoproterozoic supergroups formed during the 2.45 Ga rifting of Kenorland. Ore Geology Reviews, 101, 985-996.

• Prof. Dr. Hartwig E. Frimmel
• Enzio Garayp
• PD Dr. Nikola Koglin (Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover)

Project duration: since 2012

Partly funded by the German Research Foundation (DFG), partly by mining companies

Summary:

The Moeda and Jacobina deposits in northeastern Brazil are the economically most important known conglomerate-hosted gold deposits in South America. Their genesis has often been compared with that of the world’s largest known gold anomaly in the Mesoarchaean Witwatersrand Basin in South Africa. In contrast to the latter, very few studies have been carried out to date on the South American examples with partly conflicting results. Uncertainties existed with regard to metallogenesis and age as well as on the significance of post-depositional alteration. This project aims at overcoming these obstacles in our understanding.  Detailed field mapping of underground exposures of the auriferous Moeda Formation conglomerate and statistical analysis of the gold distribution therein revealed a strong sedimentological control on ore grade, with most of the gold being concentrated on top of an old erosion surface. Combined U-Pb and Lu-Hf isotope data obtained on detrital zircon grains from these deposits constrained the sedimentation age to 2.68 Ga and gave important information about possible source areas, indicating major reworking of older crust in the hinterland of the Moeda Formation’s depositional basin. Rutile grain analysis yielded atypically high REE and Th concentrations. In combination with U-Pb isotopic data, these data revealed a major metamorphic overprint combined with different stages/intensities of fluid-rock interactions at 2.25 Ga. Gold morphological studies revealed the presence of both hydrothermal gold and detrital gold micronuggets, which corroborate the notion of a modified palaeoplacer genesis. Mineralogical evidence from gold–tourmaline intergrowths on authigenic pyrite indicates that the transporting fluid was boron-rich but poor in aqueous sulfide species, at least at Moeda. In contrast to Moeda, the Jacobina deposits experienced a higher degree of metamorphism and hydrothermal overprint, being located near a major thrust plane. Nevertheless, primary mineralogical and mineral chemical features remained preserved in places. Systematic difference in gold composition between different conglomerate units (reefs) and undoubtedly hydrothermal gold in cross-cutting veins, shear zones and intrusive bodies, attest to original placer deposits with variable provenance and subsequent syn-orogenic reworking of the ore.

Publications:

Koglin, N., Zeh, A., Cabral, A.R., Seabra Gomes Jr., A.A., Corrêa Neto, A.V., Brunetto, W.J., Galbiatti, H. (2014): Depositional age and sediment source of the auriferous Moeda Formation, Quadrilátero 
Ferrífero of Minas Gerais, Brazil: New constraints from U–Pb–Hf isotopes in zircon and xenotime. Precambrian Research 255, 96-108.

Cabral, A.R., Koglin, N. (2012): Hydrothermal fluid source constrained by Co/Ni ratios in coexisting arsenopyrite and tourmaline: the auriferous lode of Passagem, Quadrilátero Ferrífero of Minas Gerais, Brazil. Mineralogy and Petrology 104, 137-145.

Cabral, A.R., Zeh, A., Koglin, N., Seabra Gomes Jr., A.A., Viana, D.J., Lehmann, B. (2012): Dating the Itabira iron formation, Quadrilátero Ferrífero of Minas Gerais, Brazil, at 2.65 Ga: Depositional U–Pb age of zircon from a metavolcanic layer. Precambrian Research 204-205, 40-45.

Koglin, N., Cabral, A.R., Brunetto, W.J., Vymazalová, A. (2012a): Gold–tourmaline assemblage in a Witwatersrand-like gold deposit, Ouro Fino, Quadrilátero Ferrífero of Minas Gerais, Brazil: the composition of gold and metallogenic implications. Neues Jahrbuch für Mineralogie, Abhandlungen 189/3, 263-273.

Koglin, N., Cabral, A.R., Brunetto, W.J., Brätz, H. (2012b): Gold and uranium contents in gypsum formed from percolating ground water in a Witwatersrand-like gold deposit, Ouro Fino, Minas Gerais, Brazil: LA– ICPMS data. Neues Jahrbuch für Mineralogie, Abhandlungen 189/2, 189-195. 

• Prof. Dr. Hartwig E. Frimmel
• Dr. Glen T. Nwaila (University of the Witwatersrand, Johannesburg, South Africa) 

Project duration: since 2012

Supported by the South African National Research Foundation (NRF) and mining companies 

Summary:

Gold is concentrated in the Earth’s crust in a multitude of different deposit types. These include orthomagmatic deposits, a great variety of hydrothermal deposits with and without magmatic affiliation, as well as syn-sedimentary deposits, such as placers. This wide range in deposit types reflects the multitude of physical and chemical processes that can lead to enrichment in gold from typical crustal background values of a few ppb to economic ore grade values of several ppm.

The temporal variation in gold endowment with regard to different deposit types throughout Earth’s history reveals that certain time periods were more suitable for specific styles of gold mineralization than others. From an economic point of view, there are only four deposit types that play a superordinate role. Of all the gold that has been mined so far and that is known to exist as reserves and suspected as resources, about 30 % occurs (occurred) as orogenic-type gold, further 30 % as conglomerate-hosted Witwatersrand-type, 16 % was (is) in porphyry (Cu-)Au and 12 % in epithermal deposits. All other deposit types together account for not more than 12 %, with the Carlin-type being most noteworthy. Focusing on the most important deposit types, a good correlation between the secular distribution of gold in mesothermal, typically shear zone-hosted quartz veins and intensity of orogenic activity has long been recognized [1], hence the term “orogenic-type”. Similarly, the strong temporal bias of porphyry-hosted and epithermal gold towards Cenozoic ages has long been explained by low preservation potential of such shallow crustal phenomena in older units. The dominance of orogenic and porphyry/epithermal gold highlights the significance of gold recycling by means of subduction, collision and orogenic crustal growth. Notwithstanding the fact that for some deposits, e.g. the Palaeozoic Muruntau deposit, a juvenile, mantle-derived addition of gold to the crust seems indicated [2], most of the post-2.8 Ga gold is suggested to have been recycled gold that had entered the crust in the course of a singular gold mega-event at around 2.9 Ga [3]. 

Although most of the continental crust must have formed prior to 3.0 Ga [4], no major orogenic gold deposits are known from pre-Neoarchaean times, suggesting a lack of crustal gold available for tectonic recycling at those early times. This changed with the postulated 2.9 Ga gold mega-event, which led to the formation of Witwatersrand-type deposits, preferentially in Mesoarchaean fluvial conglomerates, first possibly by microbial fixation of gold that had been dissolved in Mesoarchaean rivers and seawater, followed by the sedimentary reworking of the thus formed gold-rich microbial mats into placers [3]. In spite of the very low preservation potential of these surface deposits, the largest proportion of known gold was, or still is, bound to these Mesoarchaean conglomerates. Much of the younger gold deposits, irrespective of their genesis, is likely to be derived from gold originally concentrated into the crusts by the 2.9 Ga mega-event. This is supported by the extraordinary chemistry of the 2.9 Ga gold, which contains orders of magnitude more Os than younger gold. 

Publications:

Nwaila, G.T., Frimmel, H.E., 2019. Highly siderophile elements in Archaean and Palaeoproterozoic marine shales of the Kaapvaal Craton, South Africa. Mineralogy and Petrology, 113(3), 307-327.

Frimmel, H.E., 2019. The Witwatersrand Basin and Its Gold Deposits. In The Archaean Geology of the Kaapvaal Craton, Southern Africa (pp. 255-275). Springer, Cham.

Frimmel, H.E., 2018. Episodic concentration of gold to ore grade through Earth's history. Earth-Science Reviews, 180, 148-158.

Frimmel, H.E., Hennigh, Q., 2015, First whiffs of atmospheric oxygen triggered onset of crustal gold cycle. Mineralium Deposita, 50, 5-23.

Frimmel, H.E., 2017, Gold through time and space. In Mercier-Langevin, P., Dube, B., Bardoux, M., Ross, P.-S., Dion, C. (eds.), Mineral Resources to Discover, Proc. 14th SGA Biennial Meeting, 20-23 August 2017, Quebec City, Society for Geology Applied to Mineral Deposits, vol. 1, 3-6.

Nwaila, G., Frimmel, H.E., 2017, Geochemistry of marine shales in the West Rand and Central Rand groups of the Mesoarchaean Witwatersrand Basin: implications for sedimentary gold endowment. In Mercier-Langevin, P., Dube, B., Bardoux, M., Ross, P.-S., Dion, C. (eds.), Mineral Resources to Discover, Proc. 14th SGA Biennial Meeting, 20-23 August 2017, Quebec City, Society for Geology Applied to Mineral Deposits, vol. 1, 75-78.

Frimmel, H.E., 2015, Onset of crustal gold cycle triggered by first oxygenic photosynthesis. In AndréMayer , A.-S., Cathelineau, M., Muchez, P., Pirard, E., Sindern, S. (eds.) Mineral Resources in a Sustainable World, Proc. 13th Biennial SGA Meeting, 24-27 August 2015, Nancy, Université de Lorraine, v. 1, 25-28.

Hölzing, A., Frimmel, H.E., Voland, V., Dremel, K., Zabler, S., Minter, W.E.L., 2015, The cover of Mineralium Deposita’s anniversary volume uncovered. In André-Mayer , A.-S., Cathelineau, M., Muchez, P., Pirard, E., Sindern, S. (eds.) Mineral Resources in a Sustainable World, Proc. 13th Biennial SGA Meeting, 24-27 August 2015, Nancy, Université de Lorraine, v.4, 1407-1410.

Nwaila, T.G., Frimmel, H.E., Minter, W.E.L., Beukes, N., 2015, Provenance and geochemical variations in shales of the Mesoarchaean Witwatersrand Supergroup. In André-Mayer , A.-S., Cathelineau, M., Muchez, P., Pirard, E., Sindern, S. (eds.) Mineral Resources in a Sustainable World, Proc. 13th Biennial SGA Meeting, 24-27 August 2015, Nancy, Université de Lorraine, v. 1, 169-172.

Frimmel, H. E., 2014, A giant Mesoarchean crustal gold-enrichment episode: Possible causes and consequences for exploration: Society of Economic Geologists, Special Publication, 18, 209-234.