Standardisation, calibration and correlation of the Kübler-index and the vitrinite/bituminite reflectance: an inter-laboratory and field related study

A multiple inter-laboratory calibration with illite Kübler-Frey-Kisch "crystallinity” index and related standards is presented and compared with CIS standards used in the last two decades in very low-grade metamorphic studies. Comparing CIS values with KI standards the CIS values show a higher full width at half-high maximum peak intensity. In all cases due to broadening effects on the Kübler-index, zone-limits, specifically the diagenetic zone/anchizone boundary, a shift is produced in geographical dimensions in a metamorphic map-view. Combining standardised Kübler-index and vitrinite-bituminite reflectance measurements a coherent data set for compilation studies can be generated from the data of different research groups. This attempt to establish a unified database of independent measures to determine diagenetic/metamorphic zones with different analytical instrumental methods are indispensable to present metamorphic maps at very low-grade conditions. Given that the Kübler-Frey-Kisch standards are difficult to preserve for the future and presumably they will be replaced with ongoing time by the CIS standards, a rescue of the laboratory settings from Frey, Kübler and others is done. After having compiled the Kübler-index—vitrinite reflectance zones in the Alps for the "New Metamorphic Map of the Alps”, the presented calibration and inter-laboratory correlation gives a chance to save the KI values obtained by very different preparation procedures applied. This is an important step for further studies in an area like the Central Alps with a very high data grid. This correlation study will also make it possible that nearly 90% of Kübler-index data from Switzerland can be compared in future work. Using the same calibration and preparation technique no fundamental problem in data comparison is achieved for the vitrinite/bituminite reflectance data operation. The main problem arises when rock maturity is compared with CIS calibrated Kübler-index values. Kübler-index values obtained by the so-called CIS calibration are not compatible with Kübler-Frey-Kisch (Árkai, Aprahamian, Brime, Ferreiro Mählmann, H. Krumm, Leoni, Petschick) calibrated Kübler-Indices. Applying both standardisation approaches for field studies, partially different results are obtaine

The Arosa zone in Eastern Switzerland: oceanic, sedimentary burial, accretional and orogenic very low- to low grade patterns in a tectono-metamorphic mélange

In the area of Arosa-Davos-Klosters (Eastern Switzerland) the different tectonic elements of the Arosa zone mélange e.g. the Austroalpine fragments, the sedimentary cover of South Penninic ophiolite fragments, as well as the matrix (oceanic sediments and flysch rocks) show distinctively different metamorphic histories and also different climaxes ("peaks”) of Alpine metamorphism. This is shown by a wealth of Kübler-Index, vitrinite and bituminite reflectance measurements, and K-white mica b cell dimension data. At least six main metamorphic events can be recognized in the area of Arosa-Davos-Klosters: (1) A pre-orogenic event, typical for the Upper Austroalpine and for instance found in the sediments at the base of the Silvretta nappe but also in some tectonic fragments of the Arosa zone (Arosa zone mélange). (2) An epizonal oceanic metamorphism observed in the close vicinity of oceanic basement rocks units of the Arosa zone (South Penninic) is another pre-orogenic process. (3) A metamorphic overprint of the adjacent Lower Austroalpine nappes and structural fragments of the Lower Austroalpine in the Arosa zone. This metamorphic overprint is attributed to the orogenic metamorphic processes during the Late Cretaceous. (4) A thermal climax observed in the South Penninic sediments of the Arosa zone can be bracketed by the Austroalpine Late Cretaceous event (3) and the middle Tertiary event (5) in the Middle Penninic units and predates Oligocene extension of the "Turba phase”. (6) North of Klosters, in the northern part of our study area, the entire tectonic pile from the North Penninic flysches to the Upper Austroalpine is strongly influenced by a late Tertiary high-grade diagenetic to low-anchizone event. In the Arosa zone mélange an individual orogenic metamorphic event is evidenced and gives a chance to resolve diagenetic-metamorphic relations versus deformation. Six heating episodes in sedimentary rocks and seven deformation cycles can be distinguished. This is well explained by the propagation of the Alpine deformation front onto the foreland units. Flysches at the hanging wall of the mélange zone in the north of the study area (Walsertal zone) show data typical for low-grade diagenetic thermal conditions and are therefore sandwiched between higher metamorphic rock units and separated from theses units by a disconformity. The Arosa zone s.s., as defined in this paper, is characterised by metamorphic inversions in the hanging wall and at the footwall thrust, thus shows differences to the Walsertal zone in the north and to the Platta nappe in the sout

The pioneer work of Bernard Kübler and Martin Frey in very low-grade metamorphic terranes: paleo-geothermal potential of variation in Kübler-Index/organic matter reflectance correlations. A review

Low-temperature metamorphic petrology occupies the P-T field between sedimentary and metamorphic petrology. Two important pillars of low-temperature metamorphism are coal petrology and clay mineralogy. When low temperature petrology was established bridging a hiatus between the two classical geological disciplines of sedimentary geology and metamorphic petrology, geologists faced a need for the usage of different terminology tenets. Martin Frey and Bernard Kübler were two pioneers in low-grade metamorphic petrology. They focused their research on clarifying the relationships of clay mineralogy and organic petrology to metamorphic pressure (P) and temperature (T) conditions. The ultimate aim of M. Frey and B. Kübler was to establish a correlation between clay indices and organic parameters for different geodynamic setting and therefore for various pressure-temperature (P-T) conditions occurring in low grade metamorphic terranes. For this purpose, a special attention was addressed to the correlation between the Kübler-Index (KI) and vitrinite reflectance (VR). All these efforts are dedicated to estimate the P-T conditions and thus to gain insight into the geodynamic evolution of low-grade metamorphic terranes. B. Kübler and M. Frey honored here concentrated their studies to the Helvetic Central Alps area. The very low-grade Helvetic domain is therefore of basic interest of this paper. Ensuing the extensive compilation of data from the Helvetic domain, a reinterpretation of Kübler and Frey's research is presented in the light of last decade's scientific progress. A comprehensive dataset available enables to discriminate many factors influencing the Kübler-Index and organic-matter reflectance alongside to time, temperature and pressure. The correlation is restricted to the KI and organic matter reflectance (mostly VR) because most of the studies used both methods. Organic matter reflectance (OMR) includes data from vitrinite reflectance and bituminite reflectance measurements. Geodynamics has important control on the KI/VR (OMR) correlation. Tectonic units having a similar geodynamic evolution are featured by the comparable KI/OMR trends, related to the particular paleo-geothermal conditions. Obviously the KI/OMR correlations provide a mean to characterise geothermal gradients and metamorphic very-low-grade pressure-temperature conditions. In terranes where high deformations rates are reported, exceeding the high anchizone conditions, strain promotes the kinetic effects of temperature and pressure on the KI versus OMR rati

Standardisation, calibration and correlation of the Kübler-index and the vitrinite/bituminite reflectance: an inter-laboratory and field related study

A multiple inter-laboratory calibration with illite Kübler-Frey-Kisch "crystallinity” index and related standards is presented and compared with CIS standards used in the last two decades in very low-grade metamorphic studies. Comparing CIS values with KI standards the CIS values show a higher full width at half-high maximum peak intensity. In all cases due to broadening effects on the Kübler-index, zone-limits, specifically the diagenetic zone/anchizone boundary, a shift is produced in geographical dimensions in a metamorphic map-view. Combining standardised Kübler-index and vitrinite-bituminite reflectance measurements a coherent data set for compilation studies can be generated from the data of different research groups. This attempt to establish a unified database of independent measures to determine diagenetic/metamorphic zones with different analytical instrumental methods are indispensable to present metamorphic maps at very low-grade conditions. Given that the Kübler-Frey-Kisch standards are difficult to preserve for the future and presumably they will be replaced with ongoing time by the CIS standards, a rescue of the laboratory settings from Frey, Kübler and others is done. After having compiled the Kübler-index—vitrinite reflectance zones in the Alps for the "New Metamorphic Map of the Alps”, the presented calibration and inter-laboratory correlation gives a chance to save the KI values obtained by very different preparation procedures applied. This is an important step for further studies in an area like the Central Alps with a very high data grid. This correlation study will also make it possible that nearly 90% of Kübler-index data from Switzerland can be compared in future work. Using the same calibration and preparation technique no fundamental problem in data comparison is achieved for the vitrinite/bituminite reflectance data operation. The main problem arises when rock maturity is compared with CIS calibrated Kübler-index values. Kübler-index values obtained by the so-called CIS calibration are not compatible with Kübler-Frey-Kisch (Árkai, Aprahamian, Brime, Ferreiro Mählmann, H. Krumm, Leoni, Petschick) calibrated Kübler-Indices. Applying both standardisation approaches for field studies, partially different results are obtaine

K-white mica b cell dimension: a complementary clay mineral tool to decipher a polyphasic basin evolution

Since the pioneer work of Sassi (1972) on the K-white mica b cell dimension BCD), the method has been used to characterize the factor pressure in meta-pelitic rocks. This method is used as an estimate of different pressure facies. Studies in the last two decades reached in low-grade metapelitic rocks. Studies in the last two decades have been carried out in different basins and meta-sedimentary rocks with poly-phase evolutions

LOW GRADE METAMORPHIC studY to PRECISE the geodynamic history and hydrocarbon migration system of THE HIKURANGI PRISM (north island, new zealand)

International audienceThe Hikurangi subduction wedge has undergone several deformation episodes periods mainly related to subduction processes, and leading to complex stratigraphic and structural patterns: i) Initial formation of an accretionary complex on the eastern Australian margin during Triassic, Jurassic, and Early Cretaceous times; ii) a stage of tectonic quiescence during Late Cretaceous to Oligocene times; iii) and the renewal of westward subduction beneath North Island since the Early Miocene to present day. The onland exposure of Neogene trench slope basins together with their Jurassic to late Paleogene pre-subduction series permits to provide a high-resolution sampling grid including all lithostratigraphic units

Fossil thermogenic hydrocarbon migration within the plumbing system of paleo-cold seeps in the Hikurangi subduction wedge (North Island, New Zealand)

International audienc