Papers by Alfons van den Kerkhof
Nature Communications, 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., H2S, COS, CS2, CH4, 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 essen...
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.
Journal of South American Earth Sciences, 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.
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 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.
Geologica Carpathica
The Weinsberg granite, a coarse-grained biotite granite with abundant K-feldspar megacrystals, is... more The Weinsberg granite, a coarse-grained biotite granite with abundant K-feldspar megacrystals, is the volumetrically dominant and most characteristic granite type of the late-Variscan Moldanubian Batholith in the Moldanubian zone of the Bohemian Massif. In the western batholith area, a local orthopyroxene-bearing variant (charnockite) of the Weinsberg granite has been identified and given the name of the Sarleinsbach quartz-monzodiorite in previous studies. Whole rock analysis of the charnockite and the relatively mafic Weinsberg granite in the immediate neighborhood show no significant geochemical differences with respect to either the major or trace elements. The mineralogy and petrology of the charnockite and surrounding granite are the same except for the presence of orthopyroxene ± clinopyroxene in the charnockite. In addition, the charnockite is characterized by the presence of dark grey, glassy orthoclase megacrysts with only some partial conversion to microcline, whereas in the granite the K-feldspar megacrysts consist of white microcline. The Fe-Mg silicates in the charnockite (orthopyroxene, clinopyroxene, amphibole, and biotite) are relatively Fe-rich (X Fe = 0.6-0.7) whereas the plagioclase is more albitic (X Ab = 0.6) than anorthitic. Fluid inclusions from the granite and associated charnockite are investigated and the results compared. The basic conclusion is that the magma responsible for the granite was dominated by an H 2 O-rich fluid with a CaCl 2 component. The magma responsible for the charnockite was dominated by a CO 2-rich fluid with a minor NaCl component, which lowered the H 2 O activity sufficiently below 1 such that orthopyroxene ± clinopyroxene was the stable Fe-Mg silicate phase during crystallization as opposed to the biotite in the granite. Taking into account that CO 2-rich and H 2 O-rich fluids are immiscible in the presence of NaCl and CaCl 2 over the P-T range of the overall crust, the implication is that in granitoid melts, if CO 2 is present, there will be regions dominated by CO 2 and regions dominated by H 2 O. The extent of either region will be determined by the overall CO 2 /H 2 O ratio in the melt. In the CO 2-dominated regions, the H 2 O activity could be sufficiently lowered such that orthopyroxene is the stable Fe-Mg silicate phase during crystallization, though this will also be dependent on the Fe/Mg ratio of these phases and the overall whole rock chemistry of the melt. In addition to incipient solid state charnockitization, commonly seen in the Archean terranes of southern India and elsewhere, this suggests that a certain subset of granites and granitoids worldwide should have patches and/or limited areas of charnockite if the amount of CO 2 present in the original magma goes above a certain fraction.
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 ) + ...
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...
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.
Journal of Metamorphic Geology, 1994
The enderbites from Tromay in the central, granulite facies part of the Proterozoic Bamble sector... more The enderbites from Tromay in the central, granulite facies part of the Proterozoic Bamble sector of southern Norway contain dominantly CO, and N, fluid inclusions. CO, from fluid inclusions in quartz segregations in enderbites was extracted by mechanical (crushing) and thermal decrepitation and the 6I3C measured. Measurement was also made on samples washed in 10% HCI, oxidized with CuO at high temperatures, and step-wise extracted with progressive heating. Results between the different techniques are systematic. The main results show 6°C of-4.5 f 1.5'%0 for crushing and-7 f 2'h for thermal decrepitation. 613C is about constant for CO, extracted at different temperatures and points to a homogeneous isotopic composition. Due to the presence of carbonate particles and/or induced contaminations for the extraction by thermal decrepitation, the results for the crushing experiments are assumed the most reliable for fluid-inclusion CO,. Very low values of 6I3C have not been found in enderbite samples and 6I3C combined with 6'*0 of the host quartzes (8-11%) indicates juvenile values. In addition, the fluid inclusions were examined by microthermometry and Raman analysis and host quartz by acoustic emission and cathodoluminescence. CO, fluid inclusions have varying densities with a frequency maximum of 0.92 g C I I-~ and generally do not concur with trapping densities at granulite conditions. Textures show that CO, must have been trapped in fluid inclusions in one early event, but transformed to different extents during late isothermal uplift without important fractionation of isotope compositions. The present data support a model of intrusion and crystallization of a C0,-rich enderbitic magma at granulite conditions.
Structural system identification using recursive methods has been a research direction of increas... more Structural system identification using recursive methods has been a research direction of increasing interest in recent decades. The two prominent methods, including the Extended Kalman Filter (EKF) and the Particle Filter (PF), also known as the Sequential Monte Carlo (SMC), are advantageous in this field. In this study, the system identification of a shake table test of a 4-story steel structure subjected to the base excitation has been implemented using these methods by considering the modeling and material model uncertainties. Implementing the 2D and 3D modelings, using the "parallelogram" and "scissors" methods for the modeling of panel zones and that of the wall panels by two methods (using beam-column elements and equivalent diagonal strut elements), are the assumptions of this study. Using the parallelogram method has resulted in fewer errors in the 2D modeling while implementing different methods for simulation of wall panels has had no specific achievements. As illustrated in the results, more significant uncertainties were expected in systems with highly nonlinear behavior, since the equivalent linearization was used to estimate the system states in the EKF method. However, this method is less time-consuming and gives more accurate results in comparison with the PF method, in which a lrge number of samples are required for the system identification.
American Mineralogist
The temperatures and pressures of diagenesis and very low-grade metamorphism of the Palaeozoic fo... more The temperatures and pressures of diagenesis and very low-grade metamorphism of the Palaeozoic formations of the Valley-and-Ridge province in the central Appalachians are revealed by analyzing their fluid inclusions. Samples from two areas were studied and compared: (l) the Silurian and Devonian Delaware Water Gap area and (2) the anthracite region of eastern Pennsylvania. Gaseous CH.-CO2 and aqueous (+CHr) inclusions were studied by microthermometry; gas compositions were measured by Raman analysis. The two fluids are thought to have been immiscible, saturated fluids. The isochores calculated for both types ofinclusions indicate fluid trapping P-Zconditions ofabout 195-245 "C, 0.8-1.3 kbar for the anthracite region, but higher pressures (1.3-1.9 kbar at 180-230'C, and possibly as much as 2.2-2.5 kbar) for the Delaware Water Gap area. The pressure difference reflects the relative stratigraphic position of the rock formations, and a higher thermal gradient for the anthracite region. The fluid trapping temperatures and pressures are consistent with conodont alteration indices (CAI), illite crystallinities, the anthracite rank, slaty cleavage development, and the stability of pyrophyllite.
Journal of Structural Geology
Abstract A combined fluid inclusion and microstructural study was carried out in beryl crystals f... more Abstract A combined fluid inclusion and microstructural study was carried out in beryl crystals from the San Cayetano Nb-Ta-bearing pegmatite (San Luis, Argentina). Primary aqueous-carbonic fluids (T0) were subsequently re-trapped during shearing, resulting in en-echelon microfractures. The more brittle behaviour of beryl compared to quartz makes this mineral more suitable for the preservation of fluid inclusions and microstructures. The primary inclusions T0 are preserved in strain-free domains, whereas the pseudo-secondary T1-to T3-type inclusions occur in domains showing intracrystalline deformation. CO2 was relatively immobile or reacted to form carbonate in early T1-type inclusions, whereas H2O preferentially migrated along microfractures and was trapped as T2-and T3-type inclusions. Short intragranular trails of fluid inclusions, representing en-echelon healed microfractures, resulted from progressive strain localization. Contrary to previous proposals, this new model implies the progressive thickness reduction of intracrystalline micro-shear zones. Besides, hydrolytic weakening linked to dislocation glide is the most likely mechanism to explain the evolution of fluid inclusions, with intracrystalline deformation enhancing anisotropic diffusion. This study highlights the potential of combined fluid inclusion and microstructural studies in order to understand the interaction between fluid activity and deformation. In this way, valuable insights can be provided into the progressive development of overprinted fabrics and low-to medium-temperature deformation mechanisms of minerals.
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Papers by Alfons van den Kerkhof