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Crystal structure, high-pressure, and high-temperature behavior of carbonates in the K2Mg(CO3)2–Na2Mg(CO3)2 join

  • Anastasia Golubkova EMAIL logo , Marco Merlini and Max W. Schmidt
Published/Copyright: November 24, 2015
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American Mineralogist
From the journal American Mineralogist Volume 100 Issue 11-12

Abstract

Although alkali-alkali earth carbonates have not been reported from mantle-derived xenoliths, these carbonates may have a substantial role in mantle metasomatic processes through lowering melting temperatures. On the Na2Mg(CO3)2-K2Mg(CO3)2 join only the Na-end-member eitelite (R3̅ space group), was reported in nature. The K-end-member (R3̅m) readily hydrates even at low temperatures, therefore, only baylissite, K2Mg(CO3)2·4H2O, has been observed. Because of the role of (K,Na)Mgdouble carbonates in mantle metasomatism, we performed high P-T experiments on K2Mg(CO3)2, (K1.1Na0.9)2Mg(CO3)2, and Na2Mg(CO3)2. Structure refinements were done upon compression of single crystals from 0 to 9 GPa at ambient temperature employing synchrotron radiation. Fitting the compression data to the second-order Birch-Murnaghan EoS resulted in V0 = 396.2(4), 381.2(5), and 347.1(3) Å3 and K0 = 57.0(10), 54.9(13), and 68.6(13) GPa for K2Mg(CO3)2, (K1.1Na0.9)2Mg(CO3)2, and Na2Mg(CO3)2, respectively. These compressibilities are lower than those of magnesite and dolomite. The KMg-double carbonate transforms into a monoclinic polymorph at 8.05 GPa; the high-P phase is 1% denser than the low-P polymorph. The NaMg-double carbonate has a phase transition at ~14 GPa, but poor recrystallization has prevented structure refinement. The parameters for a V-T EoS were collected at 25-600 °C and ambient pressure and are ɑ0 = 14.31(5) × 10-5 K-1 and 16.73(11) × 10-5 K-1 for K2Mg(CO3)2 and Na2Mg(CO3)2, respectively. Moreover, fitting revealed an anisotropy of thermal expansion along the a- and c-axis: ɑ0(a) = 2.84(6) × 10-5 and 4.78(5) × 10-5 K-1 and ɑ0(c) = 10.47(11) × 10-5 and 8.72(5) × 10-5 K-1 for K2Mg(CO3)2 and Na2Mg(CO3)2, respectively.

Keywords: Alkali-alkali earth double carbonates; synchrotron; high pressure; phase transition
Received: 2014-10-9
Accepted: 2015-4-25
Published Online: 2015-11-24
Published in Print: 2015-11-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am-2015-5219
Keywords for this article
Alkali-alkali earth double carbonates; synchrotron; high pressure; phase transition

Articles in the same Issue

  1. On understanding the structure and composition of crystals
  2. Stable and metastable silicate liquid immiscibility in ferrobasalts
  3. When was the Earth’s conveyor belt set in motion?
  4. Trace element partitioning into sulfide: How lithophile elements become chalcophile and vice versa
  5. Petrology on Mars
  6. Hf and Nd isotope systematics of early Archean komatiites from surface sampling and ICDP drilling in the Barberton Greenstone Belt, South Africa
  7. Quasicrystals at extreme conditions: The role of pressure in stabilizing icosahedral Al63Cu24Fe13 at high temperature
  8. Tracking the thermal decomposition of plasma-sprayed hydroxylapatite
  9. Experimental constraints on bubble formation and growth during magma ascent: A review
  10. Ankerite grains with dolomite cores: A diffusion chronometer for low- to medium-grade regionally metamorphosed clastic sediments
  11. Crystal structure, high-pressure, and high-temperature behavior of carbonates in the K2Mg(CO3)2–Na2Mg(CO3)2 join
  12. Temperature micro-mapping in oscillatory-zoned chlorite: Application to study of a green-schist facies fault zone in the Pyrenean Axial Zone (Spain)
  13. Micro- and nano-characterization of Zn-clays in nonsulfide supergene ores of southern Peru
  14. Mineralogical characterization of individual growth structures of Mn-nodules with different Ni+Cu content from the central Pacific Ocean
  15. The magma plumbing system of the Emeishan large igneous province and its role in basaltic magma differentiation in a continental setting
  16. Weathering of the Ethiopian volcanic province: A new weathering index to characterize and compare soils
  17. Recommended mineral-melt partition coefficients for FRTEs (Cu), Ga, and Ge during mantle melting
  18. Tetrahedral plot diagram: A geometrical solution for quaternary systems
  19. Investigations on alunogen under Mars-relevant temperature conditions: An example for a single-crystal-to-single-crystal phase transition
  20. Crystallization of calcium oxalate hydrates by interaction of calcite marble with fungus Aspergillus niger
  21. Direct and indirect evidence for free oxygen (O2–) in MO-silicate glasses and melts (M = Mg, Ca, Pb)
  22. Effect of fluid composition on growth rate of monazite in quartzite at 1.0 GPa and 1000 °C
  23. Determination of the full elastic tensor of single crystals using shear wave velocities by Brillouin spectroscopy
  24. Temperature dependence of the velocity-density relation for liquid metals under high pressure: Implications for the Earth’s outer core
  25. Thermal, compositional, and compressional demagnetization of cementite
  26. The MnCO3-II high-pressure polymorph of rhodocrosite
  27. Lanthanide tetrads in normalized rare element patterns of zircon from the Koktokay No. 3 granitic pegmatite, Altay, NW China
  28. Hydrogrossular, Ca3Al2(SiO4)3–x(H4O4)x: An ab initio investigation of its structural and energetic properties
  29. High-pressure synthesis of skiagite-majorite garnet and investigation of its crystal structure
  30. Mineralogical evolution of Fe–Si-rich layers at the olivine-water interface during carbonation reactions
  31. High-pressure spectroscopic study of siderite (FeCO3) with a focus on spin crossover
  32. Exploring the potential of Raman spectroscopy for crystallochemical analyses of complex hydrous silicates: I. Amphiboles
  33. Apexite, NaMg(PO4)·9H2O, a new struvite-type phase with a heteropolyhedral cluster
  34. The mechanism of infiltration of metamorphic fluids recorded by hydration and carbonation of epidote-amphibolite facies metabasaltic sills in the SW Scottish Highlands
  35. The axial ratio of hcp Fe and Fe–Ni–Si alloys to the conditions of Earth’s inner core
  36. Shock-induced mobilization of metal and sulfide in planetesimals: Evidence from the Buck Mountains 005 (L6 S4) dike-bearing chondrite
  37. The accretion and differentiation of Earth under oxidizing conditions
  38. Dislocation microstructures in simple-shear-deformed wadsleyite at transition-zone conditions: Weak-beam dark-field TEM characterization of dislocations on the (010) plane
  39. Chemical composition and crystal structure of merrillite from the Suizhou meteorite
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