title: Thermodynamic analysis of primary and secondary mineral stability in melilite-nephelinite tuff with Australopithecus Afarensis footprints (Laetoli, Tanzania)
metadata.name: dc.contributor.author
metadata.value: Perova, Elena N.
metadata.lang: -
metadata.name: dc.contributor.author
metadata.value: Zaitsev, Anatoly N.
metadata.lang: -
metadata.name: dc.contributor.author
metadata.value: Spratt, John
metadata.lang: -
metadata.name: dc.contributor.author
metadata.value: Vlasenko, Nataliya S.
metadata.lang: -
metadata.name: dc.contributor.author
metadata.value: Platonova, Nataliya V.
metadata.lang: -
metadata.name: dc.contributor.author
metadata.value: Bubnova, Olga G.
metadata.lang: -
metadata.name: dc.date.accessioned
metadata.value: 2022-10-03T13:47:52Z
metadata.lang: -
metadata.name: dc.date.available
metadata.value: 2022-10-03T13:47:52Z
metadata.lang: -
metadata.name: dc.date.issued
metadata.value: 2022-06
metadata.lang: -
metadata.name: dc.identifier.citation
metadata.value: Perova, E. N., Zaitsev, A. N., Spratt, J., Vlasenko, N. S., Platonova, N. V., Bubnova, O. G. (2022). Thermodynamic analysis of primary and secondary mineral stability in melilite-nephelinite tuff with Australopithecus Afarensis footprints (Laetoli, Tanzania). Vestnik of Saint Petersburg University. Earth Sciences, 67 (2), 227–242. https://doi.org/10.21638/spbu07.2022.202 (In Russian)
metadata.lang: en_GB
metadata.name: dc.identifier.other
metadata.value: https://doi.org/10.21638/spbu07.2022.202
metadata.lang: -
metadata.name: dc.identifier.uri
metadata.value: http://hdl.handle.net/11701/38059
metadata.lang: -
metadata.name: dc.description.abstract
metadata.value: The Laetoli area in northern Tanzania is an important palaeo-anthropological site, where the
  oldest footprints of Australopithecus afarensis reside. Aeolian tuffs are the major rock type at Laetoli and they are divided into Lower and Upper Laetolil Beds that were deposited at an
  interval of 4.36 and 3.63 million years. The Upper Laetolil Beds contain eight layers of air-fall
  tuffs known as marker tuffs. The Australopithecus afarensis footprints are observed on the
  surface of the white tuff, which is a part of the Upper Laetolil marker tuff 7, also known as the
  “Footprint Tuff.” The interpolated age of the marker tuff 7 is 3.66 million years. Two mineral
  assemblages are distinguished in the Upper Laetolil marker tuffs. The first assemblage consists
  of primary tuff minerals and includes clinopyroxene (diopside, augite, aegirine-augite),
  nepheline, melilite (åkermanite and alumoåkermanite), garnet (andradite and schorlomite),
  magnetite, and others. The second mineral assemblage consists of secondary minerals, montmorillonite,
  calcite, and phillipsite. They were formed during replacement of the primary minerals,
  volcanic glass, and ash cementation. Thermodynamic calculations show that the major
  primary tuff minerals (melilite and nepheline) are stable at variable sodium activity and pH
  values. Replacement of melilite and nepheline by montmorillonite is caused by a decrease of
  sodium activity in slightly alkaline, neutral and acidic conditions (рН < 10). Montmorillonite
  is not present in the altered nephelinitic tuff of the Sadiman volcano (which is considered as a
  source of the Laetolil Beds) where kaolinite is the major secondary mineral. This is explained
  by the difference in H2O fugacity with higher lgfH2O values in Sadiman and lower values in
  Laetoli. Relationships between primary and secondary tuffs minerals on the lgaHCO3 vs pH
  plot suggest mineral transformation within the Laetolil Beds in slightly acid and neutral conditions
  (рН = 5–7) compared with more alkaline conditions at Sadiman (рН > 10).
metadata.lang: en_GB
metadata.name: dc.description.sponsorship
metadata.value: This study was supported by the Ngorongoro Conservation Area Authorities (Tanzania), Russian
  Foundation for Basic Research (grant 18-05-00835) and The Natural History Museum (London). Scientific
  research was performed at the Centers for X-ray Diffraction Methods and Geomodel of the Research Park
  of St Petersburg State University.
metadata.lang: en_GB
metadata.name: dc.language.iso
metadata.value: ru
metadata.lang: en_GB
metadata.name: dc.publisher
metadata.value: St Petersburg State University
metadata.lang: en_GB
metadata.name: dc.relation.ispartofseries
metadata.value: Vestnik of St Petersburg University. Earth Sciences;Volume 67; Issue 2
metadata.lang: -
metadata.name: dc.subject
metadata.value: melilite
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: nepheline
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: montmorillonite
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: calcite
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: tuff
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: Laetoli
metadata.lang: en_GB
metadata.name: dc.subject
metadata.value: Tanzania
metadata.lang: en_GB
metadata.name: dc.title
metadata.value: Thermodynamic analysis of primary and secondary mineral stability in melilite-nephelinite tuff with Australopithecus Afarensis footprints (Laetoli, Tanzania)
metadata.lang: en_GB
metadata.name: dc.type
metadata.value: Article
metadata.lang: en_GB
resources.filename: 02.pdf
resources.url: https://dspace.spbu.ru/bitstream/11701/38059/1/02.pdf
resources.format: Adobe PDF
resources.size: 6,12 MB