Evaluation of terrestrial carbonaceous matter aromatization by Raman spectroscopy and its application to C chondrites

Abstract

A Raman method to estimate the aromatization degree of carbonaceous matter (CM) was established, and calibrated by literature data respecting differences in acquisition procedures. The generated equations allowed a comparison of the G-band width to vitrinite reflectance, and to additional structural organization parameter extracted from X-ray powder diffraction. The relations between aromatization degree and peak temperatures from literature were then propagated to G-band width parameter. The applicability of these geothermometers is demonstrated by the consistency of data obtained for carbonaceous chondrites with previous estimations. Since the CM aromatization is controlled by peak temperature and time span, it is possible to estimate the duration of chondrite's heating events. The G-band width relation to elemental ratio trends of organic matter in chondrites, interplanetary dust particles, glucose, and saccharose-based semi-coke favors synthesis by formose route. These findings provide new approaches for the future development of chemical kinetic models for organic matter of chondrites. A reliable chemical model may allow the external calibration of numerical models for accurately evaluating the peak temperatures and cooling durations of chondrites.

Thermal metamorphism of CM chondrites: A dehydroxylation‐based peak‐temperature thermometer and implications for sample return from asteroids Ryugu and Bennu

“…Multiple studies of some mineral-water reactions and organic maturation phenomena in a variety of chondrite classes have quantitatively estimated "short" durations of some heating-cooling episodes and specific associated chemical reactions. Insoluble macromolecular organic matter in some chondrites regarded as more strongly metamorphosed than the usual meteorites of the same group (including CM-like, CR) exhibits spectroscopic signatures consistent with those produced by experimental heating episodes of seconds or minutes to weeks durations (Yabuta et al 2010;Briani et al 2013;Schmidt and Hinrichs 2020). Several studies of secondary mineral production by aqueous alteration in both ordinary and carbonaceous chondrites have quantitatively estimated reaction durations to be in the range of approximately 10 0 -10 1 yr (Dyl et al 2012;Velbel et al 2012).…”

“…For example, for Y-86720 (metamorphism stage IV of Nakamura [2005], >750°C), Raman spectroscopy yielded estimates of <230°C (Busemann et al 2007), 70°C using an equation for long-duration geological maturation of OM and 245°C using an equation for rapid carbonization of OM (Schmidt and Hinrichs 2020), 496 AE 55°C using an equation for longduration geological maturation of OM (Kiryu et al 2020), and carbon-XANES measurements yielded 265 AE 42°C (Cody et al 2008). Similarly, for WIS 91600 (metamorphism stage II of Nakamura [2005], 300-500°C), Raman spectroscopy yielded estimates of 362.2 AE 49.8°C for matrix IOM (Chan et al 2017), 67°C using an equation for long-duration geological maturation of OM, and 277°C using an equation for rapid carbonization of OM (Schmidt and Hinrichs 2020). Such differences are attributed to differences between the kinetics of IOM and mineral responses to the temperatures and durations of heating events, with mineral-textural indicators responding much more rapidly to short, rapid heating events such as impacts (e.g., Cody et al [2008]; Quirico et al [2014] and references therein; Schmidt and Hinrichs 2020).…”

“…n From Ebert et al (2019). o From Buchanan et al (1993 (Chan et al 2017), 77°C using an equation for long-duration geological maturation of OM, and 260°C using an equation for rapid carbonization of OM (Schmidt and Hinrichs 2020).…”

“…Many workers observe that T estimated from Raman spectroscopy of IOM in chondrites in general (e.g., Cody et al 2008;Schmidt and Hinrichs 2020) and ATCC chondrites in particular (e.g., Quirico et al 2014;Schmidt and Hinrichs 2020) are significantly (up to~600°C) lower than those estimated from mineralogical and textural parameters. For example, for Y-86720 (metamorphism stage IV of Nakamura [2005], >750°C), Raman spectroscopy yielded estimates of <230°C (Busemann et al 2007), 70°C using an equation for long-duration geological maturation of OM and 245°C using an equation for rapid carbonization of OM (Schmidt and Hinrichs 2020), 496 AE 55°C using an equation for longduration geological maturation of OM (Kiryu et al 2020), and carbon-XANES measurements yielded 265 AE 42°C (Cody et al 2008).…”

“…Temperatures estimated from various spectroscopies of IOM in CM chondrites that experienced only aqueous alteration vary among laboratories by more than 300°C. For example, for Murchison, Raman spectroscopy yielded estimates of <220°C(Busemann et al 2007), 309.2 AE 6.3°C for matrix IOM(Chan et al 2017), 60°C using an equation for long-duration geological maturation of OM and 222°C using an equation for rapid carbonization of OM(Schmidt and Hinrichs 2020), four values using an equation for long-duration geological maturation of OM ranging from 396 AE 47 to 443 AE 51°C(Kiryu et al 2020), and carbon-XANES measurements yielded 96 AE 65°C(Cody et al 2008). Similarly, for Nogoya, AE 15.2°C for matrix IOM…”