Near infrared signature of opaline silica at Mars-relevant pressure and temperature

Chauviré, Boris; Pineau, M.; Quirico, E.; Beck, Pierre

doi:10.1016/j.epsl.2021.117239

Cited by 5 publications

(6 citation statements)

References 70 publications

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“…It is estimated to be in the nanometer range (circa 4 to 10 nm in diameter for opal-CT and 6 to 200 (+) nm for opal-A) [50,58]. The crystallisable water contained in opal is present in both isolated and interconnected closed pores or, in some cases, in open pores exposed to the atmosphere, as demonstrated by measurements of the opal's near-infrared signature at low pressures [62]. In this study, most opals analysed have closed porosity, but some opal-CT specimens have open pores and can reversibly lose water to the atmosphere.…”

Section: Water In Opalsmentioning

confidence: 99%

“…Thus, prior to heating, these samples retained water in the opal's structure. Some of these samples have been exposed to low pressure (1 mbar), and potential dehydration has been monitored by infrared spectroscopy as a function of time and pressure in a previous study [62]. All air-stored samples that showed cracking at elevated temperatures did not lose water as pressure was reduced, suggesting that water in air-stored samples is contained in a system of closed pores.…”

Section: Decrepitationmentioning

confidence: 99%

“…To achieve this, the measurement of the pore size and the permeability of a sample is required. Even if these properties could be measured by non-destructive methods (e.g., differential scanning calorimetry or infrared spectroscopy [52,58,62]), work is required to adapt these techniques for the gem market.…”

Section: Practical Considerationsmentioning

confidence: 99%

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Cracking of Gem Opals

Chauviré¹,

Mollé

Guichard³

et al. 2023

Minerals

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The value of gem opals is compromised by their potential susceptibility to “crazing”, a phenomenon observed either in the form of whitening or cracking. To understand the latter, 26 opal samples were investigated and separated into 2 groups based on handling: “water-stored” opal samples, which are stored in water after extraction, and “air-stored” opal samples, which are stored in air for more than a year. To induce cracking, samples were thermally treated by staged heating and characterized using optical microscopy and Raman spectroscopy before and after cracking. For water-stored opals, cracking was initiated with moderate heating up to 150 °C, while for air-stored opals, higher temperatures, circa 300 °C, were required. In water-stored opals that cracked, polarized light microscopy revealed stress fields remaining around the cracks, and a red shift in the Raman bands suggested tensile stresses. These stresses were not observed in air-stored samples that cracked. Based on these observations, for air-stored samples, cracking was ascribed to super-heated water-induced decrepitation. By contrast, for water-stored samples, cracking was linked to drying shrinkage, which correlates with the anecdotal reports from the gem trade. We thus identify the physical origin of cracking, and by comparing it to current knowledge, we determine the factors leading to cracking.

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Section: Water In Opalsmentioning

confidence: 99%

Section: Decrepitationmentioning

confidence: 99%

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Cracking of Gem Opals

Chauviré¹,

Mollé

Guichard³

et al. 2023

Minerals

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“…Phyllosilicates form a large group of hydrous minerals, which are structured in layers bounded by cation-anion couples that contain OH groups in their crystalline structure. They can contain H 2 O molecules between layers, and dehydration experiments show that serpentinite minerals (one of the most common forms) can hold up to ∼13 wt% of water (Bezacier et al 2010;Chauviré et al 2021;Pettke & Bretscher 2022).…”

Section: Introductionmentioning

confidence: 99%

Formation of the Trappist-1 system in a dry protoplanetary disk

Schneeberger,

Mousis,

Deleuil

et al. 2024

A&A

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A key feature of the Trappist-1 system is its monotonic decrease in bulk density with growing distance from the central star, which indicates an ice mass fraction that is zero in the innermost planets, b and c, and about 10<!PCT!> in planets d through h. Previous studies suggest that the density gradient of this system could be due to the growth of planets from icy planetesimals that progressively lost their volatile content during their inward drift through the protoplanetary disk. Here we investigate the alternative possibility that the planets formed in a dry protoplanetary disk populated with pebbles made of phyllosilicates, a class of hydrated minerals with a water fraction possibly exceeding 10 wt<!PCT!>. We show that the dehydration of these minerals in the inner regions of the disk and the outward diffusion of the released vapor up to the ice-line location allow the condensation of ice onto grains. Pebbles with water mass fractions consistent with those of planets d--h would have formed at the snow-line location. In contrast, planets b and c would have been accreted from drier material in regions closer to the star than the phyllosilicate dehydration line.

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“…Visible/near infrared (VNIR) reflectance spectra provide by far the most reliable and effective data set for identifying chemical and mineralogical features of stratigraphy on the Mars (Chauviré et al, 2021;Cuadros et al, 2016;Fox et al, 2021;Michalski et al, 2015;Pineau et al, 2022;Viviano-Beck et al, 2014). The absorption bands at ~1400, ~1900, ~2200 and ~2290 nm are essentially related to OH (octahedral metal-OH, metal = Al, Fe and Mg) and H2O (interlayer water) of kaolinite and nontronite (Bibring et al, 2005;Ehlmann et al, 2013;Pineau et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Characterization of kaolinized nontronite by visible to near infrared (VNIR) reflectance spectroscopy: implication for the genesis of compositional stratigraphy on Mars

Qin

Liu

Tan

et al. 2022

Preprint

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Compositional stratigraphy, consisting of Al-rich kaolinite overlying Fe/Mg-richnontronite, is sporadically distributed within 40{degree sign}S to 30{degree sign}N on Mars. The compositional stratigraphy was considered a typical product of a warm and wet climate, and a window into understanding the atmospheric conditions of early Mars. However, the question remains as to whether the compositional stratigraphy was formed by chemical weathering or sedimentation. Variations in mineralogical/ geochemical properties along the compositional stratigraphy can provide important clues for interpreting the genesis of the compositional stratigraphy. Visible to near infrared (VNIR) reflectance spectroscopy has been used as an effective tool to quantitatively characterize the abundance of kaolinite, nontronite, and weathering intensity in a basaltic weathering succession, as demonstrated by a terrestrial regolith profile. Nevertheless, the VNIR spectra could be influenced by primary minerals and organics in a basalt succession. To test the effectiveness of spectral parameters, the stepwise transformation of nontronite to kaolinite was experimentally modeled and quantitatively investigated using thermogravimetric (TG) and VNIR. The correlation between BD1400 and the content of OH, BD1900 and the H 2 O content, and BD1400/BD1900 and the OH/H 2 O ratio were quantitatively constrained to demonstrate their effectiveness as spectral proxies. The obtained data set was also compared with the VNIR spectra from the compositional stratigraphy on Mars, and the continuous variations of the spectral proxies suggest the compositional stratigraphy is formed by a surface chemical weathering process. Accordingly, Mars likely had a warm and wet climate that could maintain liquid water on its surface over a geologic time span.

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Near infrared signature of opaline silica at Mars-relevant pressure and temperature

Cited by 5 publications

References 70 publications

Cracking of Gem Opals

Cracking of Gem Opals

Formation of the Trappist-1 system in a dry protoplanetary disk

Characterization of kaolinized nontronite by visible to near infrared (VNIR) reflectance spectroscopy: implication for the genesis of compositional stratigraphy on Mars

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