Combined high-pressure and high-temperature vibrational studies of dolomite: phase diagram and evidence of a new distorted modification

Efthimiopoulos, Ilias; Jahn, Sandro; Kuras, A.; Schade, U.; Koch‐Müller, Monika

doi:10.1007/s00269-017-0874-5

Cited by 30 publications

(50 citation statements)

References 49 publications

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“…The transition pressure determined here is consistent with the results in previous studies [20,21]. As pressure grows to~7 GPa, the [CO 3 ] 2− stretches shift to higher frequencies at a constant slope of 2.12(3) cm −1 •GPa −1 for the symmetrical modes and~3.5 cm −1 •GPa −1 for the asymmetrical (Figure 5b); the pressure slopes of the O-C-O stretches in malachite are comparable to those in carbonates [30][31][32][33]. The rest of the bending bands 829.03, 818.26, and 749.42 cm −1 display negligible pressure dependence.…”

Section: Vibrational Changes Of Malachite Under Pressuresupporting

confidence: 92%

“…Our observation of the marginal pressure shifts for the O-C-O bending in malachite is a characteristic in carbonates (MCO 3 , M = Ca, Cd, Mn, Fe, Zn, Mg, etc.) [30][31][32][33][34]. This bending (and the force constant) involves O 2− deviation at an oblique angle to the M-O bond, thus their frequencies are anticipated to be insensitive to the changes in the M-O bond strength.…”

Section: Vibrational Changes Of Malachite Under Pressurementioning

confidence: 99%

“…A further increase in pressure (above~15 GPa) leads to the appearance of more modes, which implies that at least the number of formula units in the unit cell changed. Considering the vibrations of [CO 3 ] 2− in carbonates under high pressure conditions [30][31][32][33][34], we attribute the development of the [CO 3 ] 2− internal modes to a decreased symmetry of the local geometry. It is also noted that upon compression from~7 to~23 GPa, the separation between the two O-C-O in-plane bands increases from~25 to~50 cm −1 .…”

Section: Structural Transitions Of Malachite Under Pressurementioning

confidence: 99%

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Vibrational Investigation of Pressure-Induced Phase Transitions of Hydroxycarbonate Malachite Cu2(CO3)(OH)2

Gao

Yuan

2020

Minerals

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Malachite Cu2(CO3)(OH)2 is a common hydroxycarbonate that contains about 15.3 wt % H2O. Its structural chemistry sheds light on other hydroxyl minerals that play a role in the water recycling of our planet. Here using Raman and infrared spectroscopy measurements, we studied the vibrational characteristics and structural evolution of malachite in a diamond anvil cell at room temperature (25 °C) up to ~29 GPa. Three types of vibrations were analyzed including Cu–O vibrations (300–600 cm−1), [CO3]2− vibrations (700–1600 cm−1), and O–H stretches (3200–3500 cm−1). We present novel observations of mode discontinuities at pressures of ~7, ~15, and ~23 GPa, suggesting three phase transitions, respectively. First, pressure has a great effect on the degree of deformation of the [CuO6] octahedron, as is manifested by the various shifting slopes of the Cu–O modes. [CuO6] deformation results in a rotation of the structural unit and accordingly a phase transition at ~7 GPa. Upon compression to ~15 GPa, the O–H bands redshift progressively with significant broadness, indicative of an enhancement of the hydrogen bonding, a shortening of the O···O distance, and possibly somewhat of a desymmetrization of the O–H···O bond. O–H mode hardening is identified above ~15 GPa coupled with a growth in the amplitude of the lower-energy bands. These observations can be interpreted as some reorientation or reordering of the hydrogen bonding. A further increment of pressure leads to a change in the overall compression mechanism of the structure at ~23 GPa, which is characterized by the blueshift of the O–H stretches and the softening of the O–C–O in-plane bending bands. The hydrogen bonding weakens due to a substantial enhancement of the Cu–H repulsion effect, and the O···O bond length shows no further shortening. In addition, the change in the local geometry of hydrogen is also induced by the softening of the [CO3]2− units. In this regard we may expect malachite and other analogous hydroxyl minerals as capable of transporting water downward towards the Earth’s transition zone (~23 GPa). Our results furnish our knowledge on the chemistry of hydrogen bonding at mantle conditions and open a new window in understanding the synergistic relations of water and carbon recycling in the deep Earth.

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Section: Vibrational Changes Of Malachite Under Pressuresupporting

confidence: 92%

Section: Vibrational Changes Of Malachite Under Pressurementioning

confidence: 99%

Section: Structural Transitions Of Malachite Under Pressurementioning

confidence: 99%

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Vibrational Investigation of Pressure-Induced Phase Transitions of Hydroxycarbonate Malachite Cu2(CO3)(OH)2

Gao

Yuan

2020

Minerals

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“…Upon further pressure increase, the spectroscopic studies conducted with argon as PTM indicated a structurally disordered Dol-IIIc 1 phase above [38][39][40] GPa; on the other hand, a recent high-pressure Raman study with neon as PTM recorded clearly an ordered Dol-IIIc Raman spectrum [26], in agreement with the relevant highpressure XRD experiments [9,27]. Prompted by this discrepancy, we have conducted additional high-pressure Raman spectroscopic investigations with neon as PTM on the same dolomite sample previously probed with argon as PTM [28], in order to understand the PTM effect on the vibrational signature, and consequently the structure of the high-pressure Dol-IIIc modification. Furthermore, we have performed the first high-pressure far-infrared (FIR) absorbance investigations on dolomite, complemented with first-principles calculations, with 1 We remind here that the most recent high-pressure XRD investigation indicated the adoption of a triclinic Dol-IIIc polymorph at 41.5 GPa (neon PTM, RT) for a Fe-free dolomite sample [27], rather than the previously reported (also triclinic) Dol-III structure [9]; since our sample was also a Fe-free dolomite, we will be using the Dol-IIIc nomenclature in the present paper.…”

Section: Introductionmentioning

confidence: 55%

“…Previous high-pressure infrared (IR) and Raman spectroscopic investigations on virtually Fe-free dolomite samples conducted with argon [28] and neon [26] serving as a pressure transmitting media (PTM), recorded the vibrational signature of the Dol-I→Dol-II transition occurring at around 15-17 GPa. Upon further pressure increase, the spectroscopic studies conducted with argon as PTM indicated a structurally disordered Dol-IIIc 1 phase above [38][39][40] GPa; on the other hand, a recent high-pressure Raman study with neon as PTM recorded clearly an ordered Dol-IIIc Raman spectrum [26], in agreement with the relevant highpressure XRD experiments [9,27].…”

Section: Introductionmentioning

confidence: 99%

Effects of hydrostaticity on the structural stability of carbonates at lower mantle pressures: the case study of dolomite

Efthimiopoulos

Germer

Jahn

et al. 2018

High Pressure Research

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We have conducted high pressure far-infrared absorbance and Raman spectroscopic investigations on a natural iron-free dolomite sample up to 40 GPa. Comparison between the present observations and literature results unraveled the effect of hydrostatic conditions on the high pressure dolomite polymorph adopted close to 40 GPa, i.e. the triclinic Dol-IIIc modification. In particular, non-hydrostatic conditions impose structural disorder at these pressures, whereas hydrostatic conditions allow the detection of an ordered Dol-IIIc vibrational response. Hence, hydrostatic conditions appear to be a key ingredient for modeling carbon subduction at lower mantle conditions. Our complementary first-principles calculations verified the far-infrared vibrational response of the ambient-and high-pressure dolomite phases.

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High‐Pressure Carbonaceous Phases as Minerals

Tschauner

2020

Geophysical Monograph Series

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High-pressure carbonaceous minerals establish a link between one of the most abundant chemical elements and processes that occur at high pressures, either in the interior of the Earth or during shock-metamorphosis in space or on Earth. Diamonds from the Earth's mantle carry inclusions of carbides, carbonates, methane, and carbon-dioxide. These inclusions elucidate diamond formation and the carbon recycling in the mantle. This chapter focuses on these inclusion minerals themselves, the means of detection, and the reconstruction of pressure-temperature conditions of their formation in the mantle.

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Combined high-pressure and high-temperature vibrational studies of dolomite: phase diagram and evidence of a new distorted modification

Cited by 30 publications

References 49 publications

Vibrational Investigation of Pressure-Induced Phase Transitions of Hydroxycarbonate Malachite Cu2(CO3)(OH)2

Vibrational Investigation of Pressure-Induced Phase Transitions of Hydroxycarbonate Malachite Cu2(CO3)(OH)2

Effects of hydrostaticity on the structural stability of carbonates at lower mantle pressures: the case study of dolomite

High‐Pressure Carbonaceous Phases as Minerals

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