Peak-temperature patterns of polyphase metamorphism resulting from accretion, subduction and collision (eastern Tauern Window, European Alps) - a study with Raman microspectroscopy on carbonaceous material (RSCM)

Raman microspectroscopy and thermo-optical-transmittance (TOT) method were used to study airborne ambient soot collected at the suburban air monitoring station in southern Poland during the residential heating (January-February) and non-heating (June–July) seasons of 2017. Carbonaceous material constituted on average 47.2 wt.% of PM2.5 during the heating season and 26.9 wt.% in the non-heating season. Average concentrations of OC (37.5 ± 11.0 μg/m3) and EC (5.3 ± 1.1 μg/m3) during the heating season were significantly higher than those in the non-heating season (OC = 2.65 ± 0.78 μg/m3, and EC = 0.39 ± 0.18 μg/m3). OC was a chief contributor to the TC mass concentration regardless of the season. All Raman parameters indicated coal combustion and biomass burning were the predominant sources of soot in the heating season. Diesel soot, which is structurally less ordered than soot from other sources, was dominant during the non-heating season. The D1 and G bands area ratio (D1A/GA) was the most sensitive Raman parameter that discriminated between various soot sources, with D1A/GA > 1 for diesel soot, and less than 1 for soot from coal and wood burning. Due to high daily variability of both TOT and Raman spectroscopy data, single-day measurements can be inconclusive regarding the soot source apportionment. Long-time measurement campaigns are recommended.

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New constraints on the exhumation history of the western Tauern Window (European Alps) from thermochronology, thermokinematic modeling, and topographic analysis

International Journal of Earth Sciences ◽

10.1007/s00531-021-02094-w ◽

2021 ◽

Author(s):

Reinhard Wolff ◽

Ralf Hetzel ◽

István Dunkl ◽

Aneta A. Anczkiewicz

Keyword(s):

Hanging Wall ◽

Thermal Relaxation ◽

Slip Rate ◽

Normal Fault ◽

European Alps ◽

Valley Bottom ◽

Topographic Analysis ◽

Tauern Window ◽

History Of ◽

Exhumation History

AbstractThe Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

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Neogene Exhumation History along TRANSALP: Insights from Low Temperature Thermochronology and Thermo-Kinematic Models

10.5194/egusphere-egu2020-9714 ◽

2020 ◽

Author(s):

Paul R. Eizenhöfer ◽

Christoph Glotzbach ◽

Lukas Büttner ◽

Jonas Kley ◽

Todd A. Ehlers

Keyword(s):

Low Temperature ◽

Kinematic Model ◽

Eastern Alps ◽

European Alps ◽

Eastern European ◽

Tauern Window ◽

The North ◽

Late Neogene ◽

Kinematic Models ◽

Exhumation Rates

Many convergent orogens such as the eastern European Alps display an asymmetric doubly-vergent wedge geometry. Loci of deepest exhumation are located above the overriding retro-wedge, whereas increased fault activity occurs in the pro-wedge on the subducting plate. The main drainage divide separates steeper from more gently sloping topography on the two wedges of different critical taper. We performed apatite and zircon (U-Th)/He analyses densely spaced along the TRANSALP geophysical transect in combination with thermo-kinematic models based on cross-section balancing. Our new low temperature thermochronology data and thermo-kinematic model results underline (i) deepest levels of exhumation across the Tauern Window until the Pliocene and (ii) higher Late Neogene exhumation rates south of the Periadriatic Fault relative to the north, while seismic activity is focussed across the Southern Alps. Our proposed mantle-to-surface link positions the retro-wedge north of the Periadriatic Fault subsequent to subduction polarity reversal during continental collision. Present-day drainage divide migration trends and imaged locations of mantle-lithospheric slabs beneath TRANSALP suggest ongoing, slow slab reversal since Adriatic indentation in the Eastern Alps.&#160;

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Thermal history of the 3.5–3.2 Ga Onverwacht and Fig Tree Groups, Barberton greenstone belt, South Africa, inferred by Raman microspectroscopy of carbonaceous material

Geology ◽

10.1130/g19915.1 ◽

2004 ◽

Vol 32 (1) ◽

pp. 37 ◽

Cited By ~ 84

Author(s):

Michael M. Tice ◽

Benjamin C. Bostick ◽

Donald R. Lowe

Keyword(s):

South Africa ◽

Thermal History ◽

Greenstone Belt ◽

Carbonaceous Material ◽

Raman Microspectroscopy ◽

Barberton Greenstone Belt ◽

History Of ◽

Fig Tree

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Moho topography beneath the Eastern European Alps by global phase seismic interferometry

10.5194/se-2020-179 ◽

2020 ◽

Author(s):

Irene Bianchi ◽

Elmer Ruigrok ◽

Anne Obermann ◽

Edi Kissling

Keyword(s):

Bohemian Massif ◽

Eastern Alps ◽

Seismic Interferometry ◽

European Alps ◽

Eastern European ◽

Data Set ◽

Tauern Window ◽

The Core ◽

The Waves ◽

Teleseismic Events

Abstract. In this work we present the application of the Global-Phase Seismic Interferometry (GloPSI) technique to a data-set recorded across the Eastern Alps with the EASI temporary seismic network (Eastern Alpine Seismic Investigation). GloPSI aims at rendering an image of the lithosphere from the waves that travel across the core before reaching the seismic stations (i.e. PKP, PKiKP, PKIKP). The technique is based on the principle that a stack of autocorrelations of transmission responses mimics the reflection response of a medium, and is used here to retrieve information about the crust-mantle boundary, such as its depth and topography. We produce images of the upper lithosphere using 64 teleseismic events. We notice that with GloPSI, we can well image the topography of the Moho in regions, where it shows a nearly planar behaviour (i.e. in the northern part of the profile, from the Bohemian massif to beneath the Northern Calcareous Alps). Below the higher crests of the Alpine chain, and the Tauern Window in particular, we cannot find evidence for a typical boundary between crust and mantle. The GloPSI results indicate the absence of an Adriatic crust made of laterally continuous layers smoothly descending southwards. On the contrary, our results confirm the observations of previous studies suggesting a structurally complex Moho topography and faulted internal Alpine crustal structure.

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Three-dimensional temperature variations in a fossil subduction zone resolved by RSCM thermometry (Tauern Window, Eastern Alps)

10.5194/egusphere-egu2020-8054 ◽

2020 ◽

Author(s):

Philip Groß ◽

Jan Pleuger ◽

Mark R. Handy ◽

Timm John

Keyword(s):

Temperature Field ◽

Subduction Zone ◽

Cross Section ◽

Subduction Zones ◽

Thermal State ◽

Three Dimensional ◽

Eastern Alps ◽

Peak Temperature ◽

Temperature Variations ◽

Tauern Window

Knowledge on the thermal state of orogens and subduction zones is crucial in trying to understand the processes that take place in these zones, since temperature controls, e.g., rock strength, metamorphic reactions and fluid flow. These are all critical parameters for the dynamics of orogens and subduction zones and conversely, these parameters feed back on the thermal state in various ways. We investigated an example of a former subduction zone, exposed in the central Tauern Window (Eastern Alps), with the aim of reconstructing its three-dimensional temperature variations.Structural and petrological observations in the central Tauern Window reveal a tens-of-kilometre-scale sheath fold that formed under high-pressure (HP) conditions (ca. 2 GPa). The fold is a composite structure that isoclinally folded the thrust of an oceanic nappe derived from Alpine Tethys onto a unit of the distal European continental margin, also affected by HP conditions. This structural assemblage is preserved between two younger domes at either end of the Tauern Window. The domes are associated with temperature-dominated Barrow-type metamorphism that overprints the HP-metamorphism partly preserved in the sheath fold.Using Raman spectroscopy on carbonaceous material (RSCM) on 100 samples from this area, we were able to distinguish domains with the original, subduction-related peak temperature conditions from domains that were overprinted during later temperature-dominated (Barrovian) metamorphism. The distribution of RSCM-temperatures in the Barrovian domains indicates a decrease of peak temperature with increasing distance from the centres of the thermal domes, both in map view and cross section. This represents a geotherm where paleo-temperature increases downward, in line with previous studies using, e.g., oxygen isotope fractionation and calcite-dolomite equilibria. However, we observe the opposite temperature trend in the lower limb of the sheath fold, viz., tendentially an upward increase in paleo-temperature. We interpret this inverted temperature domain as the relic of a subduction-related temperature field. Towards the central part of the sheath fold&#8217;s upper limb, measured temperatures increase to a maximum of ca. 520&#176;C. Further upsection in the hanging wall of the sheath fold, temperatures decrease to where they are indistinguishable from the peak temperatures of the overprinting Barrovian metamorphism. Isograds (i.e. contours of equal peak-temperature) are oriented roughly parallel to the nappe contacts and lithological layering, which results in an eye-shaped concentric isograd pattern in cross-section. This reflects a sheath-like three-dimensional geometry of the isograds. We propose the following hypothesis to explain the subduction-related peak-temperature pattern: The pattern reflects sheath folding of a subduction-related temperature field. Possibly, sheath folding occurred during exhumation, after the equilibration at peak pressure and temperature conditions. The preservation of the pattern implies fast exhumation and cooling of the rocks.

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Fast cooling of normal-fault footwalls: Rapid fault slip or thermal relaxation?

Geology ◽

10.1130/g46940.1 ◽

2020 ◽

Vol 48 (4) ◽

pp. 333-337

Author(s):

Reinhard Wolff ◽

Ralf Hetzel ◽

István Dunkl ◽

Aneta A. Anczkiewicz ◽

Hannah Pomella

Keyword(s):

Thermal Relaxation ◽

Normal Fault ◽

Geothermal Gradient ◽

European Alps ◽

Normal Faulting ◽

Heat Advection ◽

Tauern Window ◽

The North ◽

Cooling Pattern ◽

Mountain Belts

Abstract Rapid rock exhumation in mountain belts is commonly associated with crustal-scale normal faulting during late-orogenic extension. The process of normal faulting advects hot footwall rocks toward Earth’s surface, which shifts isotherms upwards and increases the geothermal gradient. When faulting stops, this process is reversed and isotherms move downwards during thermal relaxation. Owing to these temporal changes of the geothermal gradient, it is not straightforward to derive the history of faulting from mineral cooling ages. Here, we combine thermochronological data with thermokinematic modeling to illustrate the importance of syntectonic heat advection and posttectonic thermal relaxation for a crustal-scale normal fault in the European Alps. The north-south–trending Brenner fault defines the western margin of the Tauern window (Austria) and caused the exhumation of medium-grade metamorphic rocks during Miocene orogen-parallel extension of the Alps. We analyzed samples from a 2-km-thick crustal section, including a 1000-m-long drill core. Zircon and apatite (U-Th)/He ages along this transect increase with elevation from ca. 8 to ca. 10 Ma and from ca. 7 to ca. 9 Ma, respectively, but differ by only ∼1 m.y. in individual samples. Thermokinematic modeling of the ages indicates that the Brenner fault became active at 19 ± 2 Ma and caused 35 ± 10 km of crustal extension, which is consistent with independent geological constraints. The model results further suggest that the fault slipped at a total rate of 4.2 ± 0.9 km/m.y. and became inactive at 8.8 ± 0.4 Ma. Our findings demonstrate that both syntectonic heat advection and posttectonic thermal relaxation are responsible for the cooling pattern observed in the footwall of the Brenner normal fault.

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Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078377 ◽

1977 ◽

Vol 35 ◽

pp. 162-163

Author(s):

Thomas R. McKee ◽

Peter R. Buseck

Keyword(s):

Crystallite Size ◽

Sedimentary Rocks ◽

Carbonaceous Material ◽

Low Grade ◽

X Ray ◽

Graphitized Carbon ◽

Transmission Electron ◽

Heat Treated ◽

Commercial Carbon ◽

Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

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A high-performance oil-free backing pump for electron microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107691 ◽

1978 ◽

Vol 36 (1) ◽

pp. 110-111

Author(s):

G.K.W. Balkau ◽

E. Bez ◽

J.L. Farrant

Keyword(s):

Molecular Weight ◽

Electron Microscope ◽

Hot Spots ◽

High Performance ◽

Carbonaceous Material ◽

Contamination Rate ◽

Low Molecular Weight ◽

Principal Source ◽

Rotary Pumps ◽

Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

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Structural phenomena in the growth of carbon nanotubes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149581 ◽

1993 ◽

Vol 51 ◽

pp. 750-751

Author(s):

Jun Jiao

Keyword(s):

Carbon Nanotubes ◽

Growth Mechanism ◽

Carbonaceous Material ◽

Cluster Growth ◽

Structural Elements ◽

Rich Variety ◽

Different Shapes ◽

Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

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