Papers by Alfons Van den Kerkhof
The Bougrine Zn-Pb deposit, the largest salt diapir-related Mississippi Valley-type deposit in the Eastern Maghreb salt diapir province, Tunisia
Ore Geology Reviews, Dec 31, 2023
Nature Communications, Feb 17, 2021
It is widely hypothesised that primeval life utilised small organic molecules as sources of carbo... more It is widely hypothesised that primeval life utilised small organic molecules as sources of carbon and energy. However, the presence of such primordial ingredients in early Earth habitats has not yet been demonstrated. Here we report the existence of indigenous organic molecules and gases in primary fluid inclusions in c. 3.5-billion-year-old barites (Dresser Formation, Pilbara Craton, Western Australia). The compounds identified (e.g., H 2 S, COS, CS 2 , CH 4 , acetic acid, organic (poly-)sulfanes, thiols) may have formed important substrates for purported ancestral sulfur and methanogenic metabolisms. They also include stable building blocks of methyl thioacetate (methanethiol, acetic acid)a putative key agent in primordial energy metabolism and thus the emergence of life. Delivered by hydrothermal fluids, some of these compounds may have fuelled microbial communities associated with the barite deposits. Our findings demonstrate that early Archaean hydrothermal fluids contained essential primordial ingredients that provided fertile substrates for earliest life on our planet.
Journal of South American Earth Sciences, Jul 1, 2017
In the Barker-Villa Cacique area (Tandilia belt), remarkable megabreccias, limestone breccias and... more In the Barker-Villa Cacique area (Tandilia belt), remarkable megabreccias, limestone breccias and phosphate-bearing breccias hosted in black limestone and along the contact with the upper section of the sedimentary succession are exposed. These rocks are the result of extensive hydrothermal alteration of the original micritic limestone and other fine-grained clastic sediments. Typical alteration minerals are sericite, chlorite, interstratified chlorite/Kwhite mica, kaolinite, dickite, pyrite, chalcopyrite, goethite, quartz, calcite, Fe-calcite, dolomite, ankerite, fluor-apatite, barite and aluminium-phosphate-sulfate (APS) minerals. Quartz and calcite cements from hydraulic breccias in the limestone contain low-salinity aqueous fluid inclusions. Corresponding homogenization temperatures display 200-220ºC and 110-140 °C in hydrothermal quartz, and 130-150ºC in late calcite cement. Carbon and oxygen stable isotope analyses of carbonates from the Loma Negra quarry (LNQ) support the major role of hydrothermal activity. A significant difference was found between δ 18 O car values from unaltered micritic limestone (ca. 23.8 ‰ SMOW) and secondary calcite (ca. 18.5 ‰ SMOW). The lower δ 18 O car values are interpreted as a result of calcite precipitation from hot hydrothermal fluids. At a late stage, the hydrothermal fluid containing H 2 S mixed with descending and oxidizing meteoric waters. Circulation of the ensuing acid fluids resulted in the partly dissolution and collapse brecciation of the Loma Negra Formation. The hydrothermal stage can be tentatively dated ca. 590-620 Ma corresponding to the Brasiliano orogeny.
Mineralogical Magazine, Apr 12, 2018
The historic Waterberg platinum deposit, ∼15 km WNW of Mookgophong (formerly Naboomspruit), Limpo... more The historic Waterberg platinum deposit, ∼15 km WNW of Mookgophong (formerly Naboomspruit), Limpopo Province, South Africa, is a rare fault-bound hydrothermal vein-type quartz-hematite-platinumgroup mineralization. As a continuation of the geochemistry and ore mineralogy studies (Part I, Oberthür et al., 2018), this paper concentrates on the ore-bearing quartz and on the age constraints of ore formation. The state-of-the-art methods used include cathodoluminescence microscopy, electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) of trace elements, stable isotope (δ 18 O) analysis and fluid-inclusion studies. U-Pb and (U-Th)/He radiometric age determination gave ages of 900-1075 Ma suggesting platinum-group element (PGE) mineralization as a result of upwelling fluids with connection to the Bushveld complex during Kibaran tectonic movements along the Thabazimbi-Murchison Lineament. Felsic fragments containing Qtz-1 were cemented by different quartz generations (Qtz-2 to Qtz-4) and enable the characterization of the changing physicochemical parameters during multistage mineralization and cooling. The PGE minerals are associated with the earliest hydrothermal stage represented by botryoidal radial-fibrous quartz aggregates (Qtz-2a) which formed on brecciated felsite. The other quartz types are essentially barren. Cathodoluminescence studies of quartz indicate very high Al, Fe and K concentrations as confirmed by EPMA and LA-ICP-MS, whereas Ti is always very low. The varying Al concentrations in the quartz mainly indicate pH fluctuations, the high Fe 3+ points at high oxygen fugacity. Micro-inclusions of iron oxide are associated with Pt ore (Fe, Pt, Pd, Au, W, Sb, As), rutile, kaolinite and muscovite. The hydrothermal activity must have been characterized by low saline (<10 wt%) H 2 O-NaCl solutions. These fluids mixed with original high-saline NaCl ± CaCl 2 ± CO 2 brines in the brecciated felsite (Qtz-1). According to the quartzhematite geothermometer the ore depositional temperatures were ∼370-330°C (Qtz-2a), whereas the successive quartz veins formed during cooling towards ∼295°C. The transport of PGE must have been facilitated by strongly oxidizing chloride complexes of relatively low salinity and moderate acidity.
Fuelling Earliest Life — Volatile Organic Compounds in 3.5 GA Old Fluid Inclusions
30th International Meeting on Organic Geochemistry (IMOG 2021), 2021
Summary It is widely accepted that small organic molecules played a central role in the emergence... more Summary It is widely accepted that small organic molecules played a central role in the emergence of life on Earth. As yet, however, there has been no conclusive evidence for the existence of the discussed relevant candidate molecules on early Earth. Here we report on indigenous, biologically-relevant organic molecules in 3.5 Ga old barite-hosted fluid inclusions from the Dresser Formation in Western Australia. We characterized the organic inventories by combining fluid inclusion petrography, stable isotope analysis and different GC-MS techniques. Our study establishes a primary origin of the fluid inclusions. They contain CO2, H2S and H2O, minor amounts of COS, CS2, N2, and CH4 as well as various oxygen and/or sulfur containing organic molecules. Notably, most of the identified compounds could have served as substrate for purported ancestral sulphur and methanogenic metabolisms. Perhaps most remarkably, the fluid inclusions also contain the stable building blocks of methyl thioacetate which is a potential key-agent in the emergence of life. Thus, our study provides the first robust evidence for the existence of such organic compounds on the early Earth and strongly supports the idea that microbial life in the 3.5 Ga old Dresser Formation was linked to hydrothermal seepage.
Ore Geology Reviews, 2018
Clausthalite and tiemannite from the type locality, Clausthal, in the Harz Mountains, Germany, ha... more Clausthalite and tiemannite from the type locality, Clausthal, in the Harz Mountains, Germany, have virtually gone undocumented since their discovery in the nineteenth century. The minerals and their selenide assemblages are here documented in historical samples from the Königin Charlotte mine in the former Clausthal Pb-Zn-Ag mining district. Clausthalite and tiemannite are the main selenide components; naumannite is generally subordinate, whereas klockmannite and eskebornite are accessory minerals. The absence of inversion lamellae in naumannite constrains the formation temperature to less than 130 °C, a temperature that is compatible with salbands of tiemannite and clausthalite that occur in the wall rock of bleached and reddened greywacke along a calcite-quartz veinlet. The veinlet calcite and quartz trapped highly saline, Ca-rich brines (26-33 weight percent NaCl equivalent), at temperatures between 96 and 212 °C. Tiemannite and clausthalite also form massive to semi-massive pockets. Tiemannite hosts inclusions of celestine, anhydrite and carrollite. This inclusion assemblage indicates that tiemannite precipitated from sulfate-bearing brines that likely originated from the overlying Zechstein evaporitic sediments. Such an origin is reflected in the less radiogenic 87 Sr/ 86 Sr values of 0.70914 and 0.71133 for two samples of tiemannite aggregates containing celestineanhydrite inclusions. The Clausthal selenide assemblages postdated the main sulfide-bearing, polymetallic vein-style mineralisation of the Harz Mountains.
The system CO2-CH4-N2 in fluid inclusions: theoretical modelling and geological applications van ... more The system CO2-CH4-N2 in fluid inclusions: theoretical modelling and geological applications van den Kerkhof, A.M. 1988 document version Publisher's PDF, also known as Version of record Link to publication in VU Research Portal citation for published version (APA) van den Kerkhof, A. M. (1988). The system CO2-CH4-N2 in fluid inclusions: theoretical modelling and geological applications. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Free University Press is an imprint of: VU Boekhandel/Uitgeverij b.v. De Boelelaan 1105 1081 HV Amsterdam The Netherlands ISBN 90-6256-694-4 cip NUGI816 © A.M. van den Kerkhof, 1988. Aile rechten voorbehouden. Niets uit deze uitgave mag worden verveelvoudigd, opgeslagen in een geautomatiseerd gegevensbestand, of openbaar gemaakt, in enige vorm of op enige wijze, hetzij electronisch, mechanisch, door fotokopieen, opnamen, of enig andere manier, zonder voorafgaande schrifte-Iijke toestemming van de auteur.
Physica B+C, 1986
In vited paper The deepest fluids contained in rocks (fluid inclusions) are essentially pure CO2 ... more In vited paper The deepest fluids contained in rocks (fluid inclusions) are essentially pure CO2 with a maximum density of 1.178 g/cm 3. Higher densities (up to 1.26g/cm 3) have been reported, but there is a distinct possibility that they are in fact N2-CO2-mixtures of much lower density.
South African Journal of Geology, 2013
The Paleoproterozoic Mako Belt in eastern Senegal is characterised by gold-bearing quartz veins. ... more The Paleoproterozoic Mako Belt in eastern Senegal is characterised by gold-bearing quartz veins. These are superimposed on the regional Birimian structural complex consisting of volcano-sedimentary and intrusive rocks in an Early Proterozoic greenstone belt. In the Mako Belt the multi-stage deformed quartz veins and hydrothermally altered protoliths are characterised by distinctive microstructures and CL properties. The high-grade Au-bearing quartz veins contain one or more generations of hydrothermal quartz. Brecciation of the veins is indicated by cemented fragments of zoned quartz. Gold in the mineralised zones occurs either as inclusions in pyrite or as native gold. Mineralisation typically occurs in vein systems which are brecciated, laminated, and/or show crack-seal textures. Microstructures indicate syn-to late-tectonic mineralisation. Au-mineralised veins contain quartz, carbonate, muscovite, fuchsite, tourmaline, and chlorite. Fluid inclusion studies reveal early, highly saline aqueous inclusions followed by main-stage aqueous-carbonic inclusions of low salinity and finally aqueous low-salinity inclusions. Petrographic observation and microthermometric data suggest that fluid inclusions in main stage quartz were trapped after phase separation from a heterogeneous H 2 O-CO 2 fluid. Gold deposition occurs over a temperature range of 220 to 320°C and pressures of 1.4 to 2.75 kbar (~5 to 10 km depth). The late-stage quartz carbonate vein corresponds to pressures of 0.75 to 1.25 kbar and depths of 3.0 to 4.5 km. A fluid pressure drop due to fracture failure is likely to have triggered Au precipitation. The Mako Belt Au deposits are comparable to a large number of orogenic lode gold deposits in the West African Craton.
Mineralogical Magazine, 2018
ABSTRACTThe Waterberg platinum deposit is an extraordinary example of a vein-type hydrothermal qu... more ABSTRACTThe Waterberg platinum deposit is an extraordinary example of a vein-type hydrothermal quartz-hematite-PGE (platinum-group element) mineralization. This study concentrates on the geochemical character of the ores and the platinum-group mineral (PGM) assemblage by application of reflected-light and scanning electron microscopy followed by electron probe microanalysis.The PGM-bearing quartz veins show multiple banding indicating numerous pulses of fluid infiltration. Mineralization was introduced contemporaneously with the earliest generation of vein quartz and hematite. High oxygen and low sulfur fugacities of the mineralizing fluids are indicated by hematite as the predominant opaque mineral and the lack of sulfides.The ‘Waterberg type’ mineralization is characterized by unique metal proportions, namely Pt>Pd>Au, interpreted as a fingerprint to the cradle of the metals, namely rocks and ores of the Bushveld Complex, or reflecting metal fractionation during ascent of an...
The petrologic and petrochronologic record of progressive vs polyphase deformation: Opening the analytical toolbox
Earth-Science Reviews
American Mineralogist
Quartz segregations in paragneisses from the Paleozoic basement of the North Patagonian Andes con... more Quartz segregations in paragneisses from the Paleozoic basement of the North Patagonian Andes contain highly saline multiphase fluid inclusions with the rare daughter mineral ferropyrosmalite detected by Raman analysis, besides halite, sylvite, hematite, and/or magnetite. During heating experiments, L-V homogenization occurs (256–515 °C), followed by halite dissolution (287–556 °C) and the dissolution of ferropyrosmalite at 550–581 °C. The latter phase transition triggers the growth of clinoamphibole crystals according to the following idealized reactions, written for potential end-members:4 F e 8 S i 6 O 15 [ ( O H ) 6 C l 4 ] + 6 C a 2 + ( a q ) Ferropyrosmalite ↔ 3 C a 2 F e 5 S i 8 ↔ O 22 ( O H ) 2 + 17 F e 2 + ( a q ) + 16 C l − ( a q ) + 12 O H − + 3 H 2 Ferro-actinolite F e 8 S i 6 O 15 [ ( O H ) 6 C l 4 ] + 2 C a 2 + ( a q ) Ferropyrosmalite + Fe 3 + ( aq ) + 2Al 3 + ( aq ) + Na + ( aq ) + H 2 O ↔ Na C a 2 ( Fe 4 2 + F e 3 + ) ( Al 2 Si 6 ) ↔ O 22 Cl 2 + 4 F e 2 + ( a q ) + ...
Multistage evolution of the Neoproterozoic “El Tarumán” gold vein-type mineralization, Dom Feliciano orogenic belt, Uruguay
Vein-type gold occurrences are found along the western margin of the Neoproterozoic Dom Feliciano... more Vein-type gold occurrences are found along the western margin of the Neoproterozoic Dom Feliciano Belt (Uruguay) and its Archean to Proterozoic basement. The “El Taruman” gold prospect is related to quartz veins hosted in dolomitic marble, which is part of the Cebollati Complex, metamorphosed in amphibolite facies. The quartz veins formed in fold hinges and sheared marble bands in a transpressive regime. Their orientation coincides with the Brasiliano structural grain, striking mostly NNE-SSW. Pyrite is the most important ore mineral, besides minor galena, chalcopyrite, and sphalerite, and accessory enargite, chalcocite and tennantite. The oxidation of sulfides produced free gold besides malachite. In our study, we combined fluid inclusion data with microstructures, which represent successive alteration stages after hydrothermal quartz mineralization and are made visible by cathodoluminescence (CL)-microscopy. In this way, the fluid evolution during the main mineralization and subse...
Magmatism and metamorphism in the middle-lower crust, SW Sweden
Journal of Petrology, 2009
Fault bound blocks of granulite and enderbite occur within upper amphibolite-facies migmatitic to... more Fault bound blocks of granulite and enderbite occur within upper amphibolite-facies migmatitic tonalitic^trondhjemitic^granodioritic (TTG) gneisses of the Iisalmi block of Central Finland. These units record reworking and partial melting of different levels of the Archean crust during a major tectonothermal event at 2Á6^2Á7 Ga. Anhydrous mineral assemblages and tonalitic melts in the granulites formed as a result of hydrous phase breakdown melting reactions involving amphibole at peak metamorphic conditions of 8^11 kbar and 750^9008C. A nominally fluid-absent melting regime in the granulites is supported by the presence of carbonic fluid inclusions. The geochemical signature of light rare earth element (LREE)depleted mafic granulites can be modelled by 10^30 wt % partial melting of an amphibolite source rock leaving a garnet-bearing residue.The degree of melting in intermediate granulites is inferred to be less than 10 wt % and was restricted by the availability of quartz. Pressure^temperature estimates for the TTG gneisses are significantly lower than for the granulites at 660^7708C and 5^6 kbar. Based on the P^Tconditions, melting of theTTG gneisses is inferred to have occurred at the wet solidus in the presence of an H 2 O-rich fluid. A hydrous mineralogy, abundant aqueous fluid inclusions and the absence of carbonic inclusions in the gneisses are in accordance with a water-fluxed melting regime. Low REE contents and strong positive Eu anomalies in most leucosomes irrespective of the host rock composition suggest that the leucosomes are not melt compositions, but represent plagioclase^quartz assemblages that crystallized early from felsic melts. Furthermore, similar plagioclase compositions in leucosomes and adjacent mesosomes are not a 'migmatite paradox' , as both record equilibration with the same melt phase percolating along grain boundaries.
The Asachinskoe epithermal gold deposit in South Kamchatka, Russia, is a low-sulfidation type dep... more The Asachinskoe epithermal gold deposit in South Kamchatka, Russia, is a low-sulfidation type deposit which consists of Au-Ag bearing quartz-adularia-illite veins. Cathodoluminescence (CL) analysis using optical microscope and scanning electron microscope and trace element analysis of quartz using electron probe micro-analyzer (EPMA) were performed to elucidate the relationships between CL structures, trace element concentrations of different quartz generations, and metal pre- cipitation mechanism of the Asachinskoe deposit. Five sequences of quartz crystallization can be distinguished within the mineralized vein of the bonanza zone. Most distinctive trace elements in quartz are Al (av. 1463 ppm) and K (av. 350 ppm). Colloform and microcrystalline quartz with moderate to dull red-brown CL coexists with electrum (Au-Ag alloy), naumannite-aguilarite (ss) and polybasite-pearceite (ss). The Au-Ag-Se precipitation is related to fluid boiling, and the Se en - richment is attributed to rel...
CH4-rich inclusions from quartz veins in the Valley- and Ridge Province and the anthracite fields of Pennsylvania Appalachians
American Mineralogist
ABSTRACT
Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 2009
ABSTRACTThe potential of igneous quartz for providing a better understanding of magmatic processe... more ABSTRACTThe potential of igneous quartz for providing a better understanding of magmatic processes is demonstrated by studying late-Hercynian rhyolites and granites from central and western Europe. Cathodoluminescence (CL) reveals growth patterns and alteration structures within igneous quartz reflecting the magma crystallisation history. The relatively stable and blue-dominant CL of zoned phenocrysts is principally related to variations in the Ti concentration, which is a function of the crystallisation temperature. The Al/Ti ratio of igneous quartz increases with progressive magma differentiation, as Ti is more compatible, compared to Al, Li, K, Ge, B, Fe, P during magma evolution. The red-dominant CL of the anhedral groundmass quartz in granite is unstable during electron bombardment and associated with OH- and H2O-bearing lattice defects. Thus, CL properties of quartz are different for rocks formed from H2O-poor and H2O-rich melts. Both groundmass and phenocrysts in granites are...
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Papers by Alfons Van den Kerkhof