Abstract
Abstract. The high-pressure phase transition of strontianite (SrCO3) was investigated at ambient temperature by means of powder and single-crystal X-ray diffraction. The samples were compressed in a diamond anvil cell to a maximum pressure of 49 GPa. Structure refinements confirm the existence of SrCO3 in the low pressure aragonite-type phase Pmcn (62) up to about 26 GPa. Above this pressure, SrCO3 transforms into a high-pressure phase with post-aragonite crystal structure Pmmn (59). Fitting the volume extracted from the compression data to the third-order Birch–Murnaghan equation of state for the low-pressure phase of SrCO3 yields K0=62.7(6) GPa and K0′=3.2(1), and for the high-pressure phase this yields K0=103(10) GPa and K0′=2.3(6). The unit cell parameters change non-uniformly, with the c axis being 4 times more compressible than the a and b axes. Our results unequivocally show the existence of a Pmmn structure in SrCO3 above 26 GPa and provide important structural parameters for this phase.
Highlights
Carbonates play a key role in the chemistry and dynamics of our planet. They are directly connected to the CO2 budget of our atmosphere and have a great impact on the deep carbon cycle (Li et al, 2019; McCammon et al, 2020)
Indirect evidence for the presence of a deep carbon cycle is given by the existence of carbonatite melts causing metasomatism in the upper mantle (Litasov et al, 2013), by CO2 in peridotitic and eclogitic systems with implications for deep melting of subducting slabs (Ghosh et al, 2009; Litasov, 2011; Thomson et al, 2016), by mantle minerals hosting carbon-bearing inclusions (Korsakov and Hermann, 2006; Shcheka et al, 2006), and the formation of diamonds
Findings of carbonate inclusions in diamonds from the upper mantle and transition zone further substantiate the existence of carbonates in the deep Earth (Sobolev et al, 1998; Wirth et al, 2009; Brenker et al, 2007; Kaminsky et al, 2009)
Summary
Carbonates play a key role in the chemistry and dynamics of our planet. They are directly connected to the CO2 budget of our atmosphere and have a great impact on the deep carbon cycle (Li et al, 2019; McCammon et al, 2020). Indirect evidence for the presence of a deep carbon cycle is given by the existence of carbonatite melts causing metasomatism in the upper mantle (Litasov et al, 2013), by CO2 in peridotitic and eclogitic systems with implications for deep melting of subducting slabs (Ghosh et al, 2009; Litasov, 2011; Thomson et al, 2016), by mantle minerals (e.g. clinopyroxene, olivine, garnet) hosting carbon-bearing inclusions (Korsakov and Hermann, 2006; Shcheka et al, 2006), and the formation of diamonds. Findings of carbonate inclusions in diamonds from the upper mantle and transition zone further substantiate the existence of carbonates in the deep Earth (Sobolev et al, 1998; Wirth et al, 2009; Brenker et al, 2007; Kaminsky et al, 2009)
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