Towards a Higher Comparability of Geothermometric Data Obtained by Raman Spectroscopy of Carbonaceous Material. Part 2: A Revised Geothermometer

2017 ◽  
Vol 41 (4) ◽  
pp. 593-612 ◽  
Author(s):  
N. Keno Lünsdorf ◽  
István Dunkl ◽  
Burkhard C. Schmidt ◽  
Gerd Rantitsch ◽  
Hilmar von Eynatten
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Material Part

Towards a Higher Comparability of Geothermometric Data obtained by Raman Spectroscopy of Carbonaceous Material. Part I: Evaluation of Biasing Factors

2013 ◽  
Vol 38 (1) ◽  
pp. 73-94 ◽  
Author(s):  
Nils K. Lünsdorf ◽  
Istvan Dunkl ◽  
Burkhard C. Schmidt ◽  
Gerd Rantitsch ◽  
Hilmar von Eynatten
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Material Part

The Potential Applications of Raman Spectroscopy in Unravelling Complex Palaeowildfire Ecosystems

2021 ◽  
Author(s):  
Thomas Theurer ◽  
David Muirhead ◽  
David Jolley ◽  
Dmitri Mauquoy
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Complex Interactions ◽  
Intensity Changes ◽  
Potential Applications ◽  
Ecosystem Studies ◽  
History Of ◽  
The Impact ◽  
Unique Relationship

<p>Raman spectroscopy represents a novel methodology of characterising plant-fire interactions through geological history, with enormous potential. Applications of Raman spectroscopy to charcoal have shown that this is an effective method of understanding intensity changes across palaeofire regimes. Such analyses have relied on the determination of appropriate Raman parameters, given their relationship with temperature of formation and microstructural changes in reference charcoals. Quantitative assessments of charcoal microstructure have also been successfully applied to the assessment of carbonaceous maturation under alternate thermal regimes, such as pyroclastic volcanism. Palaeowildfire systems in association with volcanism may present a complex history of thermal maturation, given interactions between detrital charcoals and volcanogenic deposition. However, whilst palaeofire and volcanic maturation of carbonaceous material are well understood individually, their interaction has yet to be characterised. Here we present the first analysis of palaeofire charcoals derived from volcanic ignition utilising Raman spectroscopy. Our results indicate that complex interactions between volcanism and palaeofire systems may be better understood by the characterisation of charcoal microstructure, alongside palaeobotanical and ecosystem studies. Understanding the unique relationship between wildfires and volcanism, and the impact that this has on the fossil record, may better assist our understanding of wildfire systems in deep history. Further still, this highlights the potential for better understanding the socioecological impacts of modern and future wildfire systems closely associated with volcanic centres. </p>

scholarly journals Pyrite and pyrrhotite in a prograde metamorphic sequence, Hyland River region, SE Yukon: implications for orogenic gold

2021 ◽  
Author(s):  
C D W Padget ◽  
D R M Pattison ◽  
D P Moynihan ◽  
O Beyssac
Keyword(s):  
Raman Spectroscopy ◽  
Phase Equilibrium ◽  
Source Region ◽  
Carbonaceous Material ◽  
Orogenic Gold ◽  
Metamorphic Rocks ◽  
Small Interval ◽  
River Region ◽  
Gradual Release ◽  
Fluid Release

The distribution of pyrite and pyrrhotite is documented within an andalusite-sillimanite type (high-temperature, low-pressure) metasedimentary succession exposed in the Hyland River region of southeastern Yukon, Canada. The following metamorphic zones are recognized: chlorite, biotite, cordierite/staurolite (porphyroblast-in), andalusite, sillimanite, and K-feldspar + sillimanite. Pyrite occurs in the chlorite zone through the biotite zone, while pyrrhotite occurs from the chlorite zone to K-feldspar + sillimanite zone. The pyrite-pyrrhotite transition, therefore, occupies an interval in the chlorite and lower biotite zones that is terminated upgrade by a pyrite-out isograd in the upper part of the biotite zone or lowest grade part of the cordierite/staurolite zone. Pressure and temperature conditions of the rocks were estimated from phase equilibrium modelling and from Raman spectroscopy of carbonaceous material (RSCM) thermometry. Modelling indicates pressures of 3.7-4.1 kbar with temperatures of ~425 °C at the biotite isograd, 560-570 °C for chlorite-out/porphyroblast-in, ~575 °C for andalusite-in, 575-600 °C for the sillimanite isograd, and 645-660 °C at the K-feldspar + sillimanite isograd. RSCM temperatures are greater than or equal to 420 °C in the Chl zone, 500 °C at the Bt isograd, 525-550 °C for porphyroblast-in isograd, ~550 °C at the And isograd, and 580 °C at the Sil isograd. These results suggest the pyrite-pyrrhotite transition occurs from less than or equal to 420°C to ~560 °C. Thermodynamic modelling shows 0.6 wt. % H2O is released during metamorphism over the ~140 °C interval of the pyrite-pyrrhotite transition. The gradual release of fluid in the biotite zone is interpreted to have broadened the pyrite-pyrrhotite transition compared to other studies that predict a small interval of vigorous fluid release associated with volumetric chlorite consumption. Samples from the pyrite-pyrrhotite transition zone contain lower whole rock and pyrite Au values than samples from unmetamorphosed/lower rocks, suggesting that Au was removed from the rock at conditions below the pyrite-pyrrhotite transition (<420 °C). The chlorite zone and higher-grade metamorphic rocks of the Hyland River area do not appear to be a plausible source region for orogenic gold.

Carbon ordering in an aseismic shear zone: implications for crustal weakening and Raman spectroscopy

2020 ◽  
Author(s):  
Lauren Kedar ◽  
Clare Bond ◽  
David Muirhead
Keyword(s):  
Raman Spectroscopy ◽  
Organic Carbon ◽  
Shear Zone ◽  
Experimental Studies ◽  
Carbonaceous Material ◽  
Shear Zones ◽  
Lower Limbs ◽  
Strain Partitioning ◽  
Increasing Temperature ◽  
Two Peaks

<p>Multi-layered stratigraphic sequences present ample opportunity for the study of strain localization and its complexities. By constraining mechanisms of crustal weakening, it is possible to gain a sounder understanding of the dynamic evolution of the Earth’s crust, especially when applied to realistic, field-based scenarios. One such mechanism is that of strain-related carbon ordering. This is the process whereby the amorphous nanostructure of fossilized organic matter contained within the rock is progressively organized towards a more sheet-like structure, similar to that of graphite. One common method of studying this process is through Raman spectroscopy. This is a non-destructive tool which makes use of the relative positions and intensities of two key spectral peaks, where one peak represents graphitic carbon and the other disordered (or amorphous) carbon. The intensity ratio between these two peaks suggests the degree to which the carbon has progressed from its original kerogen-like structure towards that of graphite. This progression can be due to increasing temperature or increasing strain, and until now, these two contributory factors have been difficult to separate, particularly in field examples.</p><p>Previous field-based studies have focused on carbon ordering on fault planes, while experimental studies have monitored the effects of strain-related ordering in organic carbon on both fault surfaces and more distributed shear zones. These studies confirmed the occurrence of strain-related ordering at seismic rates, particularly in the form of graphitization of carbon. However, these experiments showed the effects of strain-related ordering at aseismic rates to be limited when distributed shear zones were considered, in part due to the geological timescales required to emulate true conditions.</p><p>In this study, Raman spectroscopy is used to compare the relative nanostructural order of organic carbon within a recumbent isoclinal fold formed of interbedded limestones and marls. The central, overturned fold limb forms a 170m wide, 1km long aseismic shear zone, with evidence of increased strain recorded in calcite grains relative to the upper and lower limbs. Raman spectroscopy intensity ratios (I[d]/I[g]) are compared across the fold, showing a marked 23% decrease in the overturned limb. Such a decrease in I[d]/I[g] suggests increased carbon ordering within the overturned limb, which in combination with evidence for increased strain in calcite, suggests that the carbon ordering here is derived directly from strain-related ordering. This has important implications. We infer, from previous studies, that strain-related carbon ordering encourages further strain partitioning in carbonaceous material, and may enhance zones of weakness in the rock. This ordering in aseismic shear zones has so far been unreported in nature, and so our field-based results are significant in supporting previous experimental evidence for this phenomenon. Our results also have implications for understanding dynamic crustal evolution, and will play an important role in the development of Raman thermobarometry, especially since current methods do not distinguish between strain-related and temperature-related ordering.</p>

scholarly journals Progressive Low-Grade Metamorphism Reconstructed from the Raman Spectroscopy of Carbonaceous Material and an EBSD Analysis of Quartz in the Sanbagawa Metamorphic Event, Central Japan

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 854
Author(s):  
Hidetoshi Hara ◽  
Hiroshi Mori ◽  
Kohei Tominaga ◽  
Yuki Nobe
Keyword(s):  
Raman Spectroscopy ◽  
Carbonaceous Material ◽  
Metamorphic Event ◽  
Ebsd Analysis ◽  
Low Grade ◽  
Accretionary Complex ◽  
Metamorphic Complex ◽  
Central Japan ◽  
Grade Metamorphism ◽  
Quartz Grains

Low-grade metamorphic temperature conditions associated with the Sanbagawa metamorphic event were estimated by the Raman spectroscopy of carbonaceous material (RSCM) in pelitic rocks and an electron backscatter diffraction (EBSD) analysis of the quartz in siliceous rocks. Analytical samples were collected from the Sanbagawa metamorphic complex, the Mikabu greenstones, and the Chichibu accretionary complex in the eastern Kanto Mountains, central Japan. Previously, low-grade Sanbagawa metamorphism was only broadly recognized as pumpellyite–actinolite facies assigned to the chlorite zone. The RSCM results indicate metamorphic temperatures of 358 °C and 368 °C for the chlorite zone and 387 °C for the garnet zone of the Sanbagawa metamorphic complex, 315 °C for the Mikabu greenstones, and 234–266 °C for the Chichibu accretionary complex. From the EBSD analyses, the diameter of the quartz grains calculated by the root mean square (RMS) approximation ranges from 55.9 to 69.0 μm for the Sanbagawa metamorphic complex, 9.5 to 23.5 μm for the Mikabu greenstones, and 2.9 to 7.3 μm for the Chichibu accretionary complex. The opening angles of the c-axis fabric approximate 40–50°, presenting temperatures of 324–393 °C for the Sanbagawa metamorphic complex and the Mikabu greenstones. The temperature conditions show a continuous increase with no apparent gaps from these low-grade metamorphosed rocks. In addition, there exists an empirical exponential relationship between the estimated metamorphic temperatures and the RMS values of the quartz grains. In this study, integrated analyses of multiple rock types provided valuable information on progressive low-grade metamorphism and a similar approach may be applied to study other metamorphic complexes.

scholarly journals Raman Spectroscopy of Carbonaceous Material record in pseudotachylytes: heating or deformation?

2020 ◽  
Author(s):  
Benjamin Moris-Muttoni ◽  
Romain Augier ◽  
Hugues Raimbourg ◽  
Abdeltif Lahfid
Keyword(s):  
Raman Spectroscopy ◽  
Cross Sections ◽  
Intensity Ratio ◽  
Frictional Heating ◽  
Carbonaceous Material ◽  
Degree Of Crystallinity ◽  
Maximum Temperature ◽  
Filling Material ◽  
Carbonaceous Materials ◽  
Wide Range

<p>The Raman Spectroscopy of Carbonaceous Materials (RSCM) permits to quantify the degree of crystallinity of carbonaceous materials (CM), which increases upon geological heating. First believed to be a reliable indicator of metamorphic grade (Pasteris and Wopenka, 1991 ; Wada et al., 1996), the quantitative evolution of crystallinity of CM has been proposed as new geothermometers for a wide range of temperature between 200 and 650°C (Beyssac et al., 2002 ; Rahl et al., 2005 ; Lahfid et al., 2010 ; Kouketsu et al., 2014).</p><p>According to recent studies, RSCM approach has been used to detect evidence of frictional heating during seismic events from pseudotachylites (Ito et al., 2017) or on fault gouges and breccia (Furuichi et al., 2015 ; Kuo et al., 2018). This new application assumes that CM spectra reflect only the thermal record irrespectively of the potential impact of geological strain on CM crystallinity (Tagiri and Tsuboi, 1979 ; Bonijoly et al., 1982 ; Ross et al., 1991 ; Bustin et al., 1995).</p><p>The aim of this study is to reconsider this postulate by using RSCM method in order to understand the effects of seismic deformation on the structure of the carbonaceous material. For this purpose, we analyzed three pseuydotachylyte veins from the Shimanto Belt (Southwest Japan), one from a drilling in the Nobeoka Tectonic Line, another from Okitsu area and a last one from the Mugi area, with RSCM method through high-resolution cross-sections perpendicular to the structure. Samples are composed of weakly foliated tectonic melanges troncated by a millimetric shear plane filled by fine black vitreous material accompanied by injection veins. Filling material presents an important grain-size reduction and embayment structures of sandstones clasts, scattered iron sulfides while element maps show flow textures. These microstructure features are described as characteristics of melt-origin pseudotachylytes (Hasegawa et al., 2019) but could also be produced by an intense comminution along with fluids circulation. Area ratio show a large evolution of CM spectra inside the pseudotachylyte compare to the host rock. In addition, intensity ratio (i.e. R1 in Beyssac et al., 2002) drastically increases inside the pseudotachylyte as expected. However, intensity ratio values are higher than expected values at this temperature, from your own calibration on undeformed samples, and highest values are observed on each rim of the pseudotachylyte. This result suggest that structural evolution of CM is not only controlled by temperature, but also by deformation, in a broad sense. More importantly, these parameters shows a very sharp evolution in few microns along cross-sections, which is at variance with thermal diffusivity models applicable for others intrusive bodies (Aoya et al., 2010 ; Hilchie and Jamieson, 2014).</p><p>These observations of step-wise evolution of CM raman parameters suggest that deformation is the principal influencing factor of the evolution of CM crystallinity in fault cores. It therefore questions the maximum temperature reached fault zones, possibly much lower than previously estimated.</p>

Raman Spectral Trends in ‘low-temperature’ Carbonaceous Materials.

2021 ◽  
Author(s):  
David Muirhead
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Amorphous Carbon ◽  
Carbonaceous Material ◽  
Carbonaceous Materials ◽  
Chemical Mechanisms ◽  
Thrust Belts ◽  
Temperature Ranges ◽  
Host Rocks ◽  
Raman Spectral

<p>Amorphous carbonaceous materials are typically those that would be considered immature, at temperatures below 300°C, in a typical sedimentary basin burial setting. Only recently has there been much discussion on the efficacy of Raman spectroscopy on amorphous carbon at temperatures below 300°C. Here we present data from a variety of published sources alongside our own data reviewing the apparent trends in amorphous carbon with some discussion related to thermal regime (intensity, duration), with case studies including intruded host rocks, fold and thrust belts and wildfires. We conclude that Raman spectroscopy can be applied successfully to ‘low-temperature’ carbonaceous material whilst noting the challenges faced to fully understand the physio-chemical mechanisms at these temperature ranges.</p>

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