Carbonate-hosted sparry magnesite is the most important raw material for the production of magnesia sinter (MgO), which is essential for the refractory industry. In one of the most significant magnesite mining districts of the Eastern Alps near Hochfilzen (Austria), fine-grained magnesite occurs in two settings: (1) as minable deposits in Silurian to Devonian dolostones and (2) in Permian breccias of red beds in the hanging wall. Despite the far-reaching implications of a possible genetic relationship between these groups on both the timing and the mechanism of sparry magnesite formation in the Eastern Alps, there is no comparative analytical data available. To decipher their relationship, we used electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, micro-X-ray fluorescence mapping and Raman spectroscopy.Paragenetic parallels, comparable rare earth element patterns, similar trace element contents and enrichment patterns point towards a common mineralizing fluid of the two magnesite groups. Based on our results, we suggest that a Mg-rich, seawater-derived brine descended into the subsurface, migrated through the red beds, magnesitized the Permian breccias, entered the underlying pre-Permian footwall along fault planes and formed the magnesite deposits – the magnesite groups are therefore related by a common fluid. We contextualize this formation model with the Permian-Triassic metallogenetic epoch in the Eastern Alps and argue for a Triassic age of the magnesite.

Stream sediments integrate the geochemical and mineralogical signals of entire drainage basins, reflecting both bedrock lithology and anthropogenic inputs. This study applies knowledge-driven Sequential Binary Partitions (SBPs) of isometric log-ratio (ilr)-transformed data to unravel relationships among geochemistry, mineralogy, and mass-specific magnetic susceptibility (chi), with an approach tested on a representative river basin (i.e., Ombrone Grossetano River Basin, Southern Tuscany, Italy), lithologically diverse and impacted by past mining activities. The method aims to improve the understanding of natural and anthropogenic influences on sediment composition. Geochemical data (X-ray fluorescence) were transformed through ilr-balances, whereas mineralogical compositions (X-ray diffraction), lithological information, and chi measurements were used to support the interpretation of sediment sources. Strong correlations between ilr-balances and mineral phases confirm that the geochemical signals reliably reflect sediment mineralogy and the basin's lithological variability. Comparisons between chi and ilr-balances detect localized anthropogenic inputs, notably Fe-enrichments linked to historical mining in a specific sub-basin (Farma-Merse). The combined use of compositional data analysis, mineralogical constraints and magnetic susceptibility provides a transferable framework to investigate sediment provenance and anthropogenic legacy in complex river systems. Beyond the case study, the results highlight the importance of considering whole-composition geochemical relationships to correctly interpret element distributions in fluvial sediments.

Abstract Raman spectroscopy of carbonaceous material (RSCM) estimates peak metamorphic temperatures in structural top units of the Eastern Alps (Steinach nappes, Gurktal nappes, Graz Paleozoic, Carboniferous of Nötsch, Kreuzeck-Goldeck-Gailtal Nappe, Diabase Zone of the North-Karawanken Range) and in their tectonic units below (Schneeberg Complex and Ötztal Nappe below the Steinach nappes, Heiligengeistklamm Nappe below the Gurktal nappes, Waxenegg Nappe below the Graz Paleozoic). The data are based on a standardized temperature calibration and describe the thermal structure of displaced tectonic units which were adjacent segments of the western Tethyan shelf during Permomesozoic times. In a west- to east profile through the Eastern Alps, RSCM data from the Koralpe-Wölz and Ötztal-Bundschuh nappe systems (Brenner area, Gurktal and Nock area, Remschnigg area, Grazer Bergland, Drau Range, North-Karawanken Range) show consistent peak metamorphic temperatures of 570-410 °C. Great similarities are found between the Steinach and Gurktal nappes. A thermal imprint of their post-Variscan (Pennsylvanian) molasse sediments is lower than 300 °C. Similar RSCM temperatures are found in Pennsylvanian sediments of the Graz Paleozoic and in the Saualpe, Remschnigg and Sausal sections of the Gurktal nappes, suggesting a similar burial depth during later times. The thermal structure of the Graz Paleozoic is characterized by an upright temperature trend within the nappe stack, by a thermal anomaly in the southeastern segment, and detachments disturbing the metamorphic pattern at the eastern margin. Permomesozoic burial heating of the Drau Range is constrained by upward decreasing RSCM temperatures. Temperatures <160 °C are estimated in the Carnian Raibl Formation. This pattern is overprinted in the central segment of the Gailtal Alps by a thermal anomaly with temperatures >200 °C in the Carnian stratigraphic level. It is suggested that the temperature gap at the base of the Drauzug-Gurktal Nappe System is related to low-angle detachments formed during post-orogenic collapse. Here, also RSCM temperatures increase locally.

Thermochronology provides powerful tools for reconstructing Earth’s thermal and tectonic history. Among low-temperature thermochronometers, zircon (U–Th)/He (ZHe) dating has gained particular importance due to its sensitivity to deep-time thermal events, enabling tight temperature constraints even for thermal histories that span billions of years.Helium diffusivity in zircon is strongly controlled by radiation-damage accumulation. This causes complex diffusion behaviour and a wide range of effective closure temperatures especially in (meta-)sedimentary rocks, where detrital zircons share their post-depositional thermal history but differ in provenance age and uranium content, leading to variable radiation-damage and annealing histories.The widely used zircon radiation damage accumulation and annealing model (ZRDAAM; Guenthner et al., 2013) predicts complete resetting of ZHe ages for samples heated above ~200 °C during burial. Consequently, highly dispersed ZHe datasets in sedimentary rocks are commonly interpreted as reflecting mixed detrital populations and limited heating below this threshold. However, this interpretation remains largely untested against natural field laboratories.In this study, ZHe closure and annealing is re-investigated based on two field areas with independently constrained thermal histories: (1) the Austroalpine Drau Range and adjacent Southalpine units and (2) the Helvetic Glarus Alps. Peak temperatures in these regions are well defined by vitrinite reflectance, Raman spectroscopy of carbonaceous material, Kübler-Index and fluid inclusion data as well as by metamorphic assemblages. In both areas, ZHe data systematically conflict with model predictions. The Austroalpine and Southalpine (meta-)sedimentary units targeted within this study experienced upper-diagenetic to low-grade metamorphic conditions (T>200 °C), but ZHe ages are largely not reset and show strong dispersion, contrary to ZRDAAM expectations. Combined ZHe–U–Pb double dating confirms substantial differences in pre-depositional provenance ages, but this age variation cannot explain the obvious difference to modelled age predictions.A similar pattern is observed in the Glarus Alps, where peak metamorphic temperatures range from diagenesis to greenschist facies. ZHe ages show a systematic younging trend but retain large single-grain age dispersion and partially inherited ages even under very low-grade metamorphic conditions.Results demonstrate significant helium retention in zircons at temperatures above 200 °C and reveal limitations of our understanding of the ZHe system. Interpreting dispersed ZHe datasets solely in terms of detrital inheritance fails to explain field constraints. Ongoing work combining U-Pb-He double dating with cathodoluminescence imaging, Raman spectroscopy, and spatially resolved U-Pb and isotopic mapping aims to identify the mechanisms responsible for this behavior and to improve the interpretation of ZHe data in sedimentary and remain-grade metamorphic rocks.Reference:Guenthner, W. R., Reiners, P. W., Ketcham, R. A., Nasdala, L., & Giester, G. (2013). Helium diffusion in natural zircon: radiation damage, anisotropy, and the interpretation of zircon (U-Th)/He thermochronology. American Journal of Science, 313(3), 145-198. ://WOS:0003193

Differentiating between syn‐ and post‐orogenic structures is critical for determining the contribution from any one mechanism toward net exhumation. In the Tauern Window of the Eastern Alps, new mapping in its northeastern region reveals significant deformation associated with W–E extension and a component of N–S shortening. Kinematic indicators reveal a clear top‐to‐E shear sense, and deformation is further highlighted by progressively deformed quartz‐calcite‐dolomite veins, whose rotation was used to quantify flow parameters, revealing an equal contribution of simple and pure shear. The ductile deformation is overprinted by E‐dipping shear bands and faults, which transition into brittle‐ductile faults compatible with incremental strain axes indicating vertical shortening during top‐to‐E extension. Raman spectroscopy data show a temperature gradient with higher structural levels exhibiting paleotemperatures <450°C, increasing to >500°C at deeper levels. White mica 40 Ar/ 39 Ar ages (25–34 Ma) in both shear veins and recrystallized fabrics confirm Oligocene deformation. At higher crustal levels, the deformation gradient progressively increases toward the newly discovered top‐to‐E Schuhflicker Detachment, defined by a knife‐sharp fault surface of ultramylonites and cataclasites. The Schuhflicker Detachment developed at mid‐crustal levels during the Oligocene, and during progressive exhumation, W–E extension was transferred to the structurally higher Katschberg Fault and Katschberg Shear Zone System during the Miocene. Collectively, these structures form the East Tauern Detachment System, which accommodated tens of kilometers of exhumation of the Tauern Window, facilitating the incipient stages of its exhumation during the Oligocene and subsequent erosion‐dominated unroofing in the Miocene.

In the NE Tauern Window of the Eastern Alps, new mapping in Nordrahmen Zone and Glockner nappes reveals significant deformation associated with W-E extension and a component of N-S shortening during the transition from high-pressure metamorphism and nappe stacking to extensional deformation. Kinematic indicators, including winged inclusions, tiling, and climbing pinch-and-swell veins, reveal a clear top-to-E shear sense, and deformation is further highlighted by progressively deformed quartz-calcite-dolomite veins, whose rotation was used to quantify flow parameters. The deformed veins used to quantify the flow parameters related to ductile deformation reveal that pure shear and simple shear contributed relatively equally. Moreover, the sub-horizontal axial planes of DIII fold structures is indicative of vertical flattening, which is signifies vertical shortening during ductile deformation. The ductile deformation is overprinted by E-dipping shear bands and faults, which transition into brittle-ductile faults compatible with incremental strain axes also indicating vertical shortening during top-to-E extension. Raman spectroscopy data show a temperature gradient with higher structural levels exhibiting paleotemperatures 500°C at deeper levels. White mica Ar-Ar analyses in both shear veins and recrystallized fabrics yield Oligocene deformation dates (25-34 Ma). Distributed ductile thinning is a characteristic feature in the footwall of detachment systems, and prompted further investigation up section. At higher crustal levels at the upper limit of the Nordrahmen Zone, the deformation gradient progressively increases towards the newly discovered top-to-E Schuhflicker Detachment, defined by a knife-sharp fault surface of ultramylonites and cataclasites. The hanging wall is defined by slightly deformed quartzites and dolomites of the Lower Austroalpine Unit. The Schuhflicker Detachment developed at mid-crustal levels during the Oligocene, and during progressive exhumation, W-E extension was transferred to the structurally higher Katschberg Fault and Katschberg Shear Zone System during the Miocene. Collectively, these structures form the East Tauern Detachment System, which accommodated tens of kilometers of exhumation of the Tauern Window, facilitating the incipient stages of its exhumation during the Oligocene and subsequent erosion-dominated unroofing in the Miocene.

We investigated rare earth element (REE) minerals in low- to medium-grade metapelites sampled in two nappes of the Austroalpine Unit (Eastern Alps, Austria). Combining microstructural and chemical characterization of the main and REE minerals with thermodynamic forward modeling, Raman spectroscopy on carbonaceous material (RSCM) thermometry and in situ U-Th-Pb dating reveal a polymetamorphic evolution of all samples. In the hanging wall nappe, allanite and REE epidote formed during Permian metamorphism (275-261 Ma, 475-520 degrees C, 0.3-0.4 GPa). In one sample, Cretaceous (ca. 109 Ma) REE epidote formed at similar to 440 degrees C and 0.4-0.8 GPa at the expense of Permian monazite clusters. In the footwall nappe, large, chemically zoned monazite porphyroblasts record both Permian (283-256 Ma, 560 degrees C, 0.4 GPa) and Cretaceous (ca. 87 Ma, 550 degrees C, 1.0-1.1 GPa) metamorphism. Polymetamorphism produced a wide range of complex REE-mineral-phase relationships and microstructures. Despite the complexity, we found that bulk rock Ca, Al and Na contents are the main factor controlling REE mineral stability; variations thereof explain differences in the REE mineral assemblages of samples with identical pressure and temperature (P-T) paths. Therefore, REE minerals are also excellent geochronometers to resolve the metamorphic evolution of low- to medium-grade rocks in complex tectonic settings. The recognition that the main metamorphic signature in the hanging wall is Permian implies a marked P-T difference of similar to 250 degrees C and at least 0.5 GPa, requiring a major normal fault between the two nappes which accommodated the exhumation of the footwall in the Cretaceous. Due to striking similarities in setting and timing, we put this low-angle detachment in context with other Late Cretaceous low-angle detachments from the Austroalpine domain. Together, they form an extensive crustal structure that we tentatively term the "Austroalpine Detachment System".

The Carnic Alps (eastern Southern Alps) provide a classical area to study polyphase very-low- to low-grade metamorphism within the Variscan belt of Europe. Temperature indicators collected during the past three decades map the general metamorphic structure of a mountain chain affected by three major tectonic events (Variscan and Alpine thrusting, Oligocene transpression). Thermometric data obtained by Raman Spectroscopy of carbonaceous material (RSCM) described in this study extend the already published database, provide a map of metamorphic isotherms, and are interpreted in the view of current tectonic concepts. The RSCM temperatures of this study describe a gradient between ca. 460 degrees C in the tectonically deepest segments, bordered by the Periadriatic Fault System, and temperatures of ca. 200 degrees C in Permian- Triassic boundary strata of the Gartnerkofel-1 core. Mapped isotherms indicate three domains with different thermal histories, characterized by Variscan imbrication of an accretionary wedge, Permo-Mesozoic burial, and Oligocene contact metamorphism.

Stratiform sediment-hosted Cu deposits are significant global sources of Cu and other important metals. The Polish Kupferschiefer produces Ag, Au, Pb, Ni, Se, and Re as by-products, whereas Co is one the of most important metals in the stratiform sediment-hosted Cu-Co deposits of the Central African Copperbelt and the Namibian Dolostone Ore Formation deposit. This study combines new and published laser ablation inductively coupled plasma mass spectrometry sulfide trace element data from these stratiform sediment-hosted copper districts. All the investigated districts exhibit sulfides occurring as disseminations and within later veins. Chalcopyrite, sphalerite, and pyrite trace element contents vary significantly between the metallogenic districts as well as between different ore stages. Random Forest discriminates the stratiform sediment-hosted Cu(-Co) districts based on trace element geochemistry. High Ag and Tl in chalcopyrite is attributed to the Polish Kupferschiefer, Ga and Ge to the Katanga Copperbelt, and Zn and In to the Dolostone Ore Formation deposit. Sphalerite from the Polish Kupferschiefer and the Dolostone Ore Formation deposit can be distinguished on the basis of the Fe and Cd contents. Cobalt and As are significantly elevated in pyrite from the Katanga Copperbelt and Mn in pyrite from the Dolostone Ore Formation deposit. The trace element contents also show that the stratiform sediment-hosted Cu(-Co) deposit sulfide data cluster separately from other deposit types. The variation in sulfide trace element contents between the three investigated stratiform sediment-hosted Cu(-Co) districts suggests that sulfide chemistry is related to the geology of the host basin and the nature of the underlying basement, which includes preexisting ore occurrences.

More than 500 occurrences of carbonate-hosted Pb-Zn ores are documented in the Eastern and Southern Alps. They are invariably hosted by shallow lagoonal and reef carbonates of Middle and more frequently Upper Triassic (Anisian and Carnian) age and are collectively termed “Alpine-type” deposits. The local palaeogeography and synsedimentary structures influenced ore mineralization. Although they occur in a wide region, they share common features such as a simple mineralogical composition, complex ore textures, light sulphur isotopic compositions, Late Palaeozoic Pb model ages, and similar trace element compositions in sphalerite, galena and pyrite. Sphalerite records a low-temperature (60-140°C) precipitation. It is low in Fe, Mn, Co, Ag and In, but commonly contains elevated Cd, Ge, As, Tl and Pb. Galena is Ag-poor, although both sphalerite and galena tend to higher Ag concentrations towards the northern Districts. Minor Fe sulphides are low in Co and Ni but carry considerable As and Tl. Rb-Sr dating of sphalerite from the type locality Bleiberg reveals an age of ≈229 Ma for ores of the Raibl Group, and ages of ≈207 and ≈201 Ma for trace element-rich breccia ore in the western part of the Bleiberg deposit. The older age corresponds to U-Pb ages obtained on calcite associated with the Pb-Zn mineralization at the Gorno deposit (Southalpine). The younger age suggests fluid flow within the carbonate sequence in an extensional tectonic regime due to fracturing of the carbonate platform during initial rifting of the Penninic Ocean.

Conventional (anthracite, calcined petroleum coke, and coke) and non-conventional (biochar, and biocokes (3 wt.% torrefied wood, and 3 wt.% petroleum coke + 3 wt.% charcoal)) carbon-bearing sources have been studied for their use in electric arc furnace (EAF)-based steel production. Commonly, for the use of carbon sources in EAFs, one of the important properties is the content of fixed carbon, the release of volatiles as well as the elemental composition of inorganics. The properties of six carbon sources were analyzed by determining the proximate analysis, X-ray fluorescence analysis (XRF), coke reactivity index (CRI), and strength after reaction with CO2 (CSR), Brunauer–Emmett–Teller (BET) specific surface area and Barrett–Joyner–Halenda (BJH) pore size and volume analysis, ash chemical analysis, optical and scanning microscopy, Raman spectroscopy and X-ray diffraction (XRD) analysis. The results indicate biocoke as a promising option to replace conventional carbon-bearing sources. In the sample set, the fixed carbon, volatiles, and ash content of the biocokes were similar despite the total difference in additives. Additionally, the use of additives did not significantly affect the biocoke reactivity indices, but slightly decreased the strength after the reaction with CO2. Carbon-bearing sources have been characterized in terms of their structural properties. XRD analysis revealed that the amount of disordered carbon increased in the order: coke < calcined petroleum coke ~ biocoke (3 wt.% torrefied wood) < biocoke (3 wt.% petroleum coke + 3 wt.% charcoal) < biochar. The results obtained on the physical, chemical, and structural properties of carbon sources are the basis for further research on the behavior of slag foaming.

&lt;p&gt;Precise thermobarometric and geochronologic data are crucial to correctly interpret the timing of metamorphism and identify complex polymetamorphic histories. We present new P-T-t-D data from samples collected in two Austroalpine nappes exposed in the Eastern Alps, Austria: the structurally upper greenschist-facies Sch&amp;#246;ckel Nappe (&amp;#8220;Graz Paleozoic,&amp;#8221; Drauzug-Gurktal Nappe System) and the structurally lower amphibolite-facies Waxenegg Nappe (Koralpe-W&amp;#246;lz Nappe System). In the latter, polymetamorphism was previously inferred. However, the timing of metamorphism is poorly resolved and only limited geochronology exists in the Sch&amp;#246;ckel Nappe.&lt;/p&gt; &lt;p&gt;Detailed petrographic investigations of chloritoid-bearing phyllite and micaschist samples collected at two localities at the base and in a higher structural level of the Sch&amp;#246;ckel Nappe revealed complex phase relations of REE-minerals, involving multiple REE-epidote generations that may be associated with monazite, xenotime, apatite and zircon. In garnet-bearing micaschist of the Waxenegg Nappe, we observed large (up to 500 &amp;#181;m) monazite exhibiting distinct core-rim chemical zoning. From careful documentation of the microstructural phase relations, thermodynamic modeling, Raman spectroscopy of carbonaceous matter and in-situ LA-ICPMS U-(Th)-Pb dating of REE-epidote and monazite we show that rocks in all three localities were affected by LP metamorphism (0.3 &amp;#8211; 0.4 GPa) during the Permian event (250 &amp;#8211; 282 Ma) with peak temperatures decreasing from 560&amp;#176;C in the lower to 475&amp;#176;C in the upper nappe. During the Eo-Alpine event, overprinting at c. 90 Ma occurred under conditions of ~550&amp;#176;C and 1.0 &amp;#8211; 1.1 GPa in the Waxenegg Nappe. At the base of the Sch&amp;#246;ckel Nappe, peak metamorphism at ~450 &amp;#8211; 470&amp;#176;C and 0.4 &amp;#8211; 0.7 GPa and cooling below 300&amp;#176;C likely took place before 110 Ma. Towards higher structural levels, only limited Eo-Alpine overprinting at low P-T conditions (&lt;400&amp;#176;C, 0.3 &amp;#8211; 0.5 GPa) is evident, thus the observed mineral assemblage reflects mostly Permian metamorphism.&lt;/p&gt; &lt;p&gt;Our results demonstrate that the main metamorphic signature in the Sch&amp;#246;ckel Nappe can be resolved as the Permian event and that the Eo-Alpine overprint is relatively lower grade than previously proposed. We observe a marked increase in Eo-Alpine peak conditions (~80 &amp;#8211; 100&amp;#176;C, 0.3 &amp;#8211; 0.5 GPa) across the nappe contact with higher grade rocks in the footwall compared to the hanging wall. The metamorphic pattern is consistent with the existence of a major normal fault between the Drauzug-Gurktal Nappe and Koralpe-W&amp;#246;lz Nappe systems in the easternmost part of the Austroalpine Unit, as already identified in its central and western parts. Finally, our study highlights that coupling modern thermobarometric analytical approaches with high spatial resolution geochronology on accessory minerals is critical to improve our understanding of the fundamentally important low-grade units of orogens.&lt;/p&gt;

The growth conditions of natural graphite crystals are conventionally estimated by the application of petrological methods on the host rocks. As Raman Spectroscopy records detailed information on the microstructure of a carbon-material, this method is applied empirically to graphite from the southern margin of the Bohemian Massif to investigate the correlation between microstructure and metamorphic peak conditions directly, characterizing an economically important geomaterial. Automated fitting of the second-order Raman-spectrum of graphite assesses the strongly asymmetrical S2-band at ca. 2700 cm-1 by a shape parameter, characterizing the microstructural state of graphite. Applying this concept, a confident parameter (S2-shape) estimates the peak metamorphic temperature of natural graphite crystals between 600 degrees C and 800 degrees C. The application in the southern Bohemian Massif maps metamorphic peak temperatures related to Variscan tectonics. Comparing the microstructure of large crystals from graphite seams with tiny crystals dispersed in the rock matrix, there is evidence that small graphite particles are not influenced by a late-stage overprint.

Dating low-grade metamorphism is challenging since such rocks commonly lack suitable target minerals for acquiring pressure-temperature-time-deformation (P-T-t-d) data. Herein a new geochronological method termed 'bulk inclusion dating' is applied to a chloritoid-bearing schist from the Staufen-Hollengebirge Nappe (SHN, Austroalpine Unit, Eastern Alps, Austria) for which Cretaceous metamorphism is imprecisely constrained. Thermodynamic modelling of the phase relations and mineral chemistry predicts the stability of the equilibrium assemblage in a P-T field between 450-490celcius and 0.5-0.7 GPa, which agrees with peak temperature constraints similar to 490celcius derived from Raman spectroscopy of carbonaceous material. Chemical zoning of, and the zonation of inclusions within, chloritoid confirm porphyroblast growth at these conditions. High-resolution imaging reveals thousands of minute (length: 0.1-3 mu m), euhedral micro-zircon crystals included in chloritoid porphyroblasts and in the matrix. The morphological and microstructural characteristics of micro-zircon as well as the crystal size distributions indicate that it nucleated and grew at greenschist facies conditions most likely from a Zr-saturated fluid. In situ laser ablation inductively coupled plasma mass spectroscopy bulk inclusion dating of metamorphic zircon in the chloritoid rim using a laser spot diameter of 120 mu m yields a U-Pb age of 116.7 +/- 9.1 Ma (MSWD: 1.5, n: 79). We interpret zircon precipitation and progressive coarsening coeval with chloritoid growth during prograde metamorphism and thus link the age to the late prograde part of the P-T evolution. The contribution of other U-bearing phases (apatite, epidote, rutile) does not significantly disturb the U-Pb age. The data provide clear evidence for Early Cretaceous metamorphism in the SHN and indicates that metamorphism started at least 20 m.y. before the formation of eclogites in the Austroalpine Unit. The method introduced here allows integration between metamorphic conditions and age constraints in low-grade metamorphic rocks and opens up new potential applications in petrochronology.

Raman spectroscopy on carbonaceous matter reconstructs the progressive path of graphitization during granulite facies metamorphism in the Variscan collisional belt of the southern Bohemian Massif. In this area, heating to 650-750 degrees C gradually altered the graphite microstructure, attributed to a metamorphic field gradient. Late lowpressure and high-temperature metamorphism at temperatures above 800 degrees C as well as advective heat transport due to rising granulite diapirs improved the graphite lattice ordering significantly. Numerical parameters derived from the Raman spectra of carbonaceous matter, in particular the G-band width and the S2-band dispersion map metamorphic field gradients in high-grade metamorphic terrains.

Adding 5 mass% wood pellets in a coal blend affects the reactivity with CO2 and microstructural properties of the coke at different final coking temperatures of 950 and 1100 degrees C. A correlation between coke reactivity index (CRI) and BET specific surface area was found. The reactivity of coke and biocoke decreases with a decrease in the specific surface area, as well as with an increase in the carbonization temperature. Raman spectroscopy results indicate that the higher carbonization temperature of biocoke mitigates the effect of 5 mass% of biomass addition. The X-ray diffraction-based interlayer spacing of carbon crystallite (d(002)) decreases slightly with increasing carbonization temperature, and crystallite height (L-c) increases with rising coking temperature for both coke and biocoke. Additionally, the lower the d(002) value, the lower the CRI of the cokes and biocokes. A good correlation between CRI and d(002) is observed. Carbon crystallite width (L-a) values increased with a rising carbonization temperature, indicating the intensive growth of carbon crystallites in all directions. However, these values for biocokes are lower due to the presence of charcoal particles.

Raman spectroscopy traces the microstructural evolution of carbonaceous matter (CM) during artificial heating. Thermo-chemical reactivity and strength of blast furnace coke at 1100 degrees C is dependent on the graphitization state of the feed coke. A standard coke reactivity index (CRI) sample is composed of lumps, showing a high microstructural variability. The frequency distribution of the D-STA parameter estimated by the "Interactive Fitting of Raman Spectra" (IFORS) software suggests a positive correlation between degree of CM organization and CRI. Samples from the tuyere region of an operating blast furnace evidence graphitization of CM at temperatures higher than 1900 degrees C. IFORS parameters, calibrated by x-ray diffraction-based lattice dimensions and transmission electron microscopy data constrain a temperature gradient decreasing from the raceway to the deadman zone. The gradient controls a continuous variation of the petrographic coke texture. As an application, the IFORS method is able to map the graphitization zones in the hearth of a working blast furnace.