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@ARTICLE{KochMueller:622847,
      author       = {Koch-Mueller, Monika and Lathe, Christian and Wunder, Bernd
                      and Appelt, Oona and Bhat, Shrikant and Ebert, Andreas and
                      Farla, Robert and Roddatis, Vladimir and Schreiber, Anja and
                      Wirth, Richard},
      title        = {{T}he coesite–stishovite transition of hydrous,
                      {A}l-bearing {S}i{O}$_2$ : an in situ synchrotron {X}-ray
                      study},
      journal      = {European journal of mineralogy},
      volume       = {36},
      number       = {6},
      issn         = {1617-4011},
      address      = {Göttingen},
      publisher    = {Copernicus Publications},
      reportid     = {PUBDB-2025-00527},
      pages        = {1023-1036},
      year         = {2024},
      abstract     = {We examined the influence of Al$_2$O$_3$ and H$_2$O on the
                      position of the coesite–stishovite transition by means of
                      in situ X-ray diffraction measurements with the large-volume
                      press at the PETRA III synchrotron in Hamburg. The position
                      of the transition was determined by several reversal
                      experiments and was found to be shifted almost in parallel
                      by about 1.5 GPa to lower pressures compared to results
                      for the pure SiO$_2$ system reported by Ono et al. (2017).
                      Two further reversal experiments with either additional
                      Al$_2$O$_3$ or additional H$_2$O added to SiO$_2$ showed
                      smaller changes compared to the results of Ono et al.
                      (2017), indicating the effect of the coupled Al and H
                      incorporation in coesite and stishovite on their transition.
                      Further investigations of the solid quenched products and of
                      products from additional multi-anvil experiments performed
                      at the GFZ Helmholtz-Zentrum für Geoforschung in Potsdam
                      were done by powder X-ray diffraction (XRD), transmission
                      electron microscopy (TEM), electron probe micro-analysis
                      (EPMA), and Fourier transform infrared (FTIR) and Raman
                      spectroscopy. Generally, the recovered samples of the in
                      situ experiments contained less stishovite than expected
                      from the last in situ XRD pattern before quenching. Thus,
                      these investigations clearly show that hydrous, Al-rich
                      stishovite that formed at high pressure (P) and temperature
                      (T) could, at least partly, not be quenched to room
                      conditions and transformed to coesite with unusually high
                      (Al, H) contents. As result of this, conventional quench
                      experiments would lead to erroneous results of the
                      transition in the (Al, H)-bearing SiO2 system. We observed
                      two kinds of coesite in the experiments: one relatively
                      Al-poor coesite transformed under equilibrium conditions at
                      P and T from stishovite over a certain time frame and an
                      Al-richer one, sometimes pseudomorphically replacing former
                      stishovite during the decompression process to room
                      conditions. Within both types of coesite, nanometre-sized
                      kyanite inclusions and relicts or remnants of stishovite
                      were observed by TEM. These observations resemble those of
                      Yang et al. (2007) on ophiolites with identical textures and
                      phases and were interpreted as result of a stishovite
                      transition back to coesite during retrograde metamorphism.
                      Our results clearly indicate that the coesite–stishovite
                      transition is sharp but can considerably vary in depth by
                      the addition of Al and H to the SiO$_2$ system. This has
                      consequences for the assignment and interpretation of the
                      depth variation of the seismic X discontinuity.},
      cin          = {DOOR ; HAS-User / FS-PET-D},
      ddc          = {550},
      cid          = {I:(DE-H253)HAS-User-20120731 /
                      I:(DE-H253)FS-PET-D-20190712},
      pnm          = {631 - Matter – Dynamics, Mechanisms and Control
                      (POF4-631) / 6G3 - PETRA III (DESY) (POF4-6G3) /
                      FS-Proposal: I-20220780 (I-20220780)},
      pid          = {G:(DE-HGF)POF4-631 / G:(DE-HGF)POF4-6G3 /
                      G:(DE-H253)I-20220780},
      experiment   = {EXP:(DE-H253)P-P61.2-20150101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001379934000001},
      doi          = {10.5194/ejm-36-1023-2024},
      url          = {https://bib-pubdb1.desy.de/record/622847},
}