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The Correction Notice in the Swiss Journal of Geosciences addresses an error in Fig. 9 of an article by Mählmann et al. The corrected figure displays the stability ranges of clay minerals and facies indicative minerals correlating with the Kübler-Index. The authors have made the necessary corrections to the original article, ensuring accuracy in their research. [Extracted from the article]

Hydrothermally altered rhyolite rocks in the Permian Donnersberg Formation of a geothermal borehole in the Northern Upper Rhine Graben (Germany) were investigated to find out answers for the low hydraulic conductivity of the rocks. The composition of clay minerals and the temperature of smectite–illite transformation were carried out using X-ray diffraction, X-ray fluorescence, transmission electron microscopy, Fourier transform infrared spectroscopy, and polarized-light microscopy analyses. Clay mineral (CM) composition includes illite/muscovite (1M and 2M1 polytypes), illite–smectite interstratifications (IS-ml), smectite, and chlorite; and non-clay minerals such as quartz, feldspars, epidote, calcite, dolomite, and hematite were detected. The 2M1-polytype mica might be the only primary sheet silicates from the parent rocks, while the others occur as authigenic neo-formed CMs under heat flow and geothermal gradient. The development of CMs indicates different mechanisms of illitization and smectitization. Based on the texture, morphology, structure/polytype, and chemistry of rocks and minerals, in particular CMs, the study grouped the CM formation into three transformation processes: smectitization during magma cooling and possible contact metamorphisms with decreasing and low temperature, smectite illitization controlled by burial diagenesis and hydrothermal alteration, and illite smectitization followed exhumation and Cenozoic subsidence with decreasing temperature. The rhyolites were altered to all of the orders IS-R0, IS-R1, and IS-R3 by the dissolution-precipitation and layer-to-layer mechanisms. The first one supported small xenomorphic plates and flakes of 1Md, elongated particles of 1M, and pseudo-hexagonal forms of 2M1. The second one could lead to the platy particles of 1Md and 2M1 polytypes. The dominant temperature range for the transformation in the area has been 140–170 °C– ~ 230 °C. [ABSTRACT FROM AUTHOR]

Fluid inclusion composition and homogenization temperatures in fibre and prismatic quartz from 45 Alpine fissures formed synkinematically during orogenic metamorphism in the external part of the Central Alps were compared with organic matter maturation determined by vitrinite reflectance %R r (random)/%R max of the host rocks. Fluid immiscibility led to both, coexisting water bearing higher hydrocarbon- (HHC) or methane-rich fluid inclusions and HHC or methane bearing water-rich fluid inclusions. The homogenization temperatures of the latter reveal inclusion formation temperatures. Earliest fibre and prismatic quartz in diagenetic and low-grade anchimetamorphic rocks crystallized more or less close to maximum temperatures. Thus, the homogenization temperatures of hydrocarbon saturated water-rich fluid inclusions are used as geothermometer between ~ 50 and 270 ± 5 °C. The process of vitrinite maturation is irreversible and the level of organic maturity is basically the product of temperature and time at moderate pressures (~ 1 to ≥ 3 kbar). Based on the close interaction of solid (vitrinite), liquid and volatile organic matter (i.e. HHC, CH 4 ) and water, fluid inclusion homogenisation temperatures are used to calibrate vitrinite reflectance (VR) measurements in the temperature range from ~ 50 to 270 ± 5 °C. The following relationship between fluid inclusion homogenization temperatures, VR and fluid composition for the external part of the Central Alps has been established: 200 ± 5 ° C VR = 2.4 ± 0.2 % R max : Transition of higher hydrocarbons wet gas to methane with ≤ 1 mole % of wet gas 270 ± 5 ° C VR = 5.7 ± 0 . 7 % R max : End of the methane stability due to red ‐ ox reactions . Applying fluid inclusion data and the VR versus illite Kübler-Index (KI) correlation the paleo-geothermal gradient is determined. In different structural units of the external part of the Central Alps the conditions vary between 45 and ≤ 20 °C/km. At these normal to slightly enhanced orogenic geothermal gradients and at a heat flow = 65 ± 10 mW/m 2 the KI 0.42 Δ°2θ of the diagenesis/anchizone boundary is fixed at: 240 ± 15 ° C and VR = 4.0 ± 0.7 % R max It is envisaged that this temperature limit may be indicative for external orogenic settings at normal to slightly hyperthermal heat flow. This will help to a better understanding of correlating organic matter versus clay mineral indices to determine geothermal settings for basic research and exploration. [ABSTRACT FROM AUTHOR]

Clay minerals and organic matter occur frequently in fault zones. Their structural characteristics and their textural evolution are driven by several formation processes: (1) reaction by metasomatism from circulating fluids; (2) in situ evolution by diagenesis; and (3) neoformation due to deformation catalysis. Clay-mineral chemistry and precipitated solid organic matter may be used as indicators of fluid circulation in fault zones and to determine the maximum temperatures in these zones. In the present study, clay-mineral and organic-matter analyses of two major fault zones - the Adams-Tinui and Whakataki faults, Wairarapa, North Island, New Zealand - were investigated. The two faults analysed correspond to the soles of large imbricated thrust sheets formed during the onset of subduction beneath the North Island of New Zealand. The mineralogy of both fault zones is composed mainly of quartz, feldspars, calcite, chabazite and clay minerals such as illite-muscovite, kaolinite, chlorite and mixed-layer minerals such as chlorite-smectite and illite-smectite. The diagenesis and very-low-grade metamorphism of the sedimentary rock is determined by gradual changes of clay mineral 'crystallinity' (illite, chlorite, kaolinite), the use of a chlorite geothermometer and the reflectance of organic matter. It is concluded here that: (1) the established thermal grade is diagenesis; (2) tectonic strains affect the clay mineral 'crystallinity' in the fault zone; (3) there is a strong correlation between temperature determined by chlorite geothermometry and organic-matter reflectance; and (4) the duration and depth of burial as well as the pore-fluid chemistry are important factors affecting clay-mineral formation. [ABSTRACT FROM AUTHOR]

We investigated the chemical and mineralogical characteristics of a weathering profile of the Nui Nua serpentinized ultramafic-mafic massif (Thanh Hoa Province, Vietnam) using TEM-EDX, XRD, and FT-IR methods to understand the effects of monsoon climate conditions on weathering processes and clay minerals, especially transformation and neoformation of clay minerals. Clay minerals of this profile were characterized by a temporariness of serpentine clay minerals though chlorite seemed to be stable and increased from the bottom layer to the top layer. The nature of Fe changed rapidly from ferrous Fe (close to parent rocks) to ferric Fe and additionally it was incorporated into the octahedral sheet of dioctahedral smectite. Consequently, a Fe-rich smectite formed at the beginning of the weathering process and was detected as a dominant phase in the clay fraction of the profile. This phase was later transformed progressively to Al-rich smectite because of Fe-oxidation and corresponding Si-mitigation. Chemically, the contents of Fe and Mg reduced from the bottom layer to the top layer but Al developed vice versa. Magnetite in top layer was formed by bacterial activities. The transformations of clay minerals were controlled strongly by leaching conditions in the weathering system and by the effects of oxidation of Fe (Fe 2 + → Fe 3 + ) on clay minerals paragenesis. [ABSTRACT FROM AUTHOR]

Low- and very low-grade metamorphic studies investigating the alteration and reaction progress of clay minerals are powerful tools to decipher the thermal evolution of sedimentary and inverted meta-sedimentary basins. Sheet silicates such as illite and chlorite are very common in sedimentary basin sequences. They can be used to determine the grade of diagenesis and low-temperature metamorphism as measured through the XRD: illite Kübler-Index (KI; illite “crystallinity” in older literature) and the chlorite Árkai-Index (ÁI; chlorite “crystallinity” in older literature), respectively. Although the ÁI method is considered to be slightly less sensitive than the KI method, a reliable correlation between both methods is often observed in metamorphic domains with a uniform heat-flow history and minor tectono-structural complexity. Complementary to these methods, the K-white mica b cell dimension provides a robust estimate of pressure facies reached in very low- to low-grade temperature domains. Here, we present a case-study from the Markstein basin located in the Southern Vosges. The lithostratigraphic units in the basin are characterized by deep marine flysch sequences of Upper Devonian to Upper Visean age and volcano-clastic sediments, respectively. The Markstein basin is surrounded by granitoids with intrusion ages between 340 and 326 Ma. A previous study showed orogenic deformation characterized by regional folding, and a contact metamorphism found in an outer halo of the granitoids up to 1500 m away from the contact (delineated by the occurrence of biotite). Here we present a multi-disciplinary study combining mineral assemblages, illite and chlorite “crystallinity indices”, and K-white mica b cell dimension. Our approach allows to (i) map in (great) detail the areal extent of both regional/burial metamorphic and contact metamorphic domains; (ii) reveal the metamorphic zonation within both domains; and (iii) better constrain regional/burial and contact metamorphic history. The contact metamorphic domain is characterized by the occurrence of biotite and/or actinolite and low K-white mica b cell dimensions, whereas the zone of incipient orogenic metamorphism yields KI and ÁI values of the high-grade diagenesis and anchizone with intermediate K-white b cell dimensions. [ABSTRACT FROM AUTHOR]

Bentonites are suitable candidates as buffer and backfill materials in HLW-repositories. A target of this research is to define the mineralogical alteration of bentonite caused by its interaction with iron powder, which simulates the contact of bentonite with a steel container. Compacted MX80 bentonite and Friedland clay (raw density of 1.6 g/cm 3 ) were used as the initial materials for clay/iron interaction experiments (10 wt.% of iron) involving percolation with NaCl or Mg-rich IP21 solution. These experiments were conducted at 25 °C, 60 °C, and 90 °C and a suite of analytical techniques was applied to identify the mineralogical transformations. Smectite was the main phase and was fully expandable in all reaction products, though the octahedral and tetrahedral compositions were altered. “Illitization” was found as a main process of smectite alteration and was caused by the percolation component of these experiments. Smectitization occurred only when Fe-oxidation was considerable. The alteration of smectite was mainly driven by the high alkaline pH-value resulting from Fe-corrosion. Different interstratified phases like kaolinite–smectite–dioctahedral vermiculite, berthierine–saponite, chlorite–saponite–trioctahedral vermiculite, and cronstedtite–saponite–trioctahedral vermiculite interstratifications were identified as neo-formed phases which were formed in minor amounts. Cementation of particles by Fe- or Si-precipitation was assumed to reduce swelling pressure and permeability. [ABSTRACT FROM AUTHOR]

Excavations of Hellenistic necropolises in ancient Issa located on the island of Vis in coastal Croatia revealed significant amounts of pottery, mostly tableware, dated from the second half of the 4th to the 1st c. BCE. Recovered pottery contained different stylistic forms thought to have been produced locally or imported. The goal of this study was to report on technological and compositional aspects of pottery economics embedded in the frame of social development of Issaean society. For this purpose, a set of 42 samples was analysed by X-ray diffractometry, polarization and electron microscopy, X-ray fluorescence, and automated electron microscopy. The results of archeometric inquiry combined with stylistic traits showed most of the vessels were produced locally whereby the procurement of raw material was dependent on the local occurrences of Terra Rossa. This required a high level of manufacture organisation, defining Issa as a presumably wellestablished Hellenistic city already in the second half of the 4th c. BCE. At the time the city maintained a strong exchange with the Italian South as suggested by excavated red figure and Gnathia pottery characterized by the superior production technologically compared to local imitations. A rare example of recovered amphoriskoi and their distinct material characteristics provided a strong indication of the presence of Levantine pottery in Issaean graves which, until now, has not been attested in the Eastern Adriatic. Such a finding speaks of the involvement of Issa in the Late Hellenistic networks of economic and cultural seaborne connectivity between the Adriatic and the Eastern Mediterranean and introduces Issa as a far-flung market of, at the time popular Levantine luxury products. [ABSTRACT FROM AUTHOR]

In the Hikurangi subduction wedge (New Zealand), a strong relationship exists between tectonic structures and fluid migrations. In the study area, outcropping tubular carbonate concretions, corresponding to the shallow subsurface plumbing systems of paleo-cold seeps, are hosted by Miocene syn-subduction mudstones. New observations demonstrate the presence of migrated solid bitumen within the tubular concretions and in the fault gouge of a major fault zone. A multi-proxy approach was performed to determine the organic matter thermal maturity in the study area (organic matter petrography and solid bitumen reflectance (BR) R r % (R r : random reflectance)). We also used Rock-Eval pyrolysis, vitrinite reflectance (VR) R r %, and clay mineral reaction progress (illite Kübler-Index and clay mineral paragenesis) to determine the diagenesis grade of the rocks. Low T max values and clay minerals indicate a thermally immature sedimentary cover. The main source rock of the region, the Waipawa Formation is locally thermally mature (VR = 0.86 R r %) suggesting that tectonic thrust-sheet stacking isresponsible for a structural thickening causing local organic maturation. The seaward propagation of out-of-sequence thrusts at base of intra-slope basins could be responsible for the inititation of biogenic fluid flows sourced in the shallow sedimentary cover that is subjected to deformation above the blind thrusts, leading to the earlier generation of the first carbonate tubular concretions. With the continuation of blind thrusting, deep thermogenic fluids then migrated laterally through fault planes (primary migration) and finally vertically through the intrabasinal pre-existing tubular concretions (secondary migration). In this paper, solid bitumen is used for the identification of a fossil thermogenic fluid migration from the source rock, along faults and through tubular carbonate conduits within a subduction thrust-wedge. The study evidences a multi-genetic tubular concretion formation, related with the timing and style of the deformation, being therefore a potential reliable indicator for the evolution of tectonic activity. • Integrated analysis of a plumbing system of paleo-cold seeps on an active margin. • Samples from SR, faults and tubular concretions to determine thermal maturity, bitumen migration, clay mineral reactions. • Circulation of thermogenic fluids in cold seep systems, which correspond initially to migration of shallow biogenic gas. • Role of the shallow plumbing system of biogenic cold seeps as vertical paths for subsequent thermogenic fluid circulations. • Structural thickening due to thrust sheet stacking favor maturation, thrust faults then acting as lateral migration pathway. [ABSTRACT FROM AUTHOR]

Abstract: We carried out a laboratory rate study to elucidate and quantify the effects of time and pressure on vitrinite reflectance (VR). A series of confined system maturation experiments was conducted at 400°C and at pressures of 2, 10 and 20kbar. Experiments were performed on dry (no water added) xylite of swamp cypress and involved run lengths from 0s to 25days. At 400°C, our experimental results demonstrate pressure and heating time to be important variables that promote VR increase and therefore the maturation of Type III organic material. VR increases with time at each investigated pressure. Despite rapid initial kinetics, the increase in VR decelerates with time at each pressure. When VR <1.44%, increasing pressure reduces the rate of VR increase and hence retards the initial VR enhancement with time. The retarding effect of pressure on VR increase diminishes with enhancing VR. The retardation of VR increase is insignificant for geological maturation at 400°C because a VR of 1.44% is attained in only a few hours. When VR >1.44%, increasing pressure counteracts the deceleration of VR increase with time and thus greatly enhances the increase in VR with time. Evidently, vitrinite maturation takes place rapidly in a dry confined system and does not require addition of water to occur. The strong effect of the experimental heat-up on VR is obvious even for very short experiments and must be corrected in kinetic analysis. The evolution of VR with heating time (t) and pressure (P) at 400°C from an initial VR of 0% is well described by our new power law rate equation where the exponent n(P, 400°C) and the rate constant k(P, 400 °C) increase with pressure. We regard this kinetic formulation as a step toward a general equation describing VR evolution as a function of time, pressure and temperature for Type III organic matter. The potential of the power law formalism to model VR from any starting VR and for complex metamorphic and heating time histories is shown by making explicit directions on how to use such a kinetic equation. [Copyright &y& Elsevier]