Internally consistent geothermometers for garnet peridotites and pyroxenites (Articolo in rivista)

Type
Label
  • Internally consistent geothermometers for garnet peridotites and pyroxenites (Articolo in rivista) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1007/s00410-009-0455-9 (literal)
Alternative label
  • Nimis P.; Grütter H. (2010)
    Internally consistent geothermometers for garnet peridotites and pyroxenites
    in Contributions to mineralogy and petrology
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Nimis P.; Grütter H. (literal)
Pagina inizio
  • 411 (literal)
Pagina fine
  • 427 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 159 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali
  • 17 (literal)
Note
  • ISI Web of Science (WOS) (literal)
  • Scopu (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Dipartimento di Geoscienze, Universita` di Padova, via Giotto 1, 35137 Padua, Italy CNR-IGG, Padua, Italy BHP Billiton World Exploration Inc, #800 Four Bentall, 1055 Dunsmuir Street, Vancouver, BC V7X 1L2, Canada (literal)
Titolo
  • Internally consistent geothermometers for garnet peridotites and pyroxenites (literal)
Abstract
  • Mutual relationships among temperatures estimated with the most widely used geothermometers for garnet peridotites and pyroxenites demonstrate that the methods are not internally consistent and may diverge by over 200°C even in well-equilibrated mantle xenoliths. The Taylor (N Jb Min Abh 172:381-408, 1998) two-pyroxene (TA98) and the Nimis and Taylor (Contrib Mineral Petrol 139:541-554, 2000) single-clinopyroxene thermometers are shown to provide the most reliable estimates, as they reproduce the temperatures of experiments in a variety of simple and natural peridotitic systems. Discrepancies between these two thermometers are negligible in applications to a wide variety of natural samples (<30°C). The Brey and Kohler (J Petrol 31:1353-1378, 1990) Ca-in-Opx thermometer shows good agreement with TA98 in the range 1,000-1,400°C and a positive bias at lower T (up to +90°C, on average, at TTA98 = 700°C). The popular Brey and Kohler (J Petrol 31:1353-1378, 1990) two-pyroxene thermometer performs well on clinopyroxene with Na contents of ca. 0.05 atoms per 6-oxygen formula, but shows a systematic positive bias with increasing NaCpx (+150°C at NaCpx = 0.25). Among Fe-Mg exchange thermometers, the Harley (Contrib Mineral Petrol 86:359-373, 1984) orthopyroxene-garnet and the recent Wu and Zhao (J Metamorphic Geol 25:497-505, 2007) olivine-garnet formulations show the highest precision, but systematically diverge (up to ca. 150°C, on average) from TA98 estimates at T far from 1,100°C and at T<1,200°C, respectively; these systematic errors are also evident by comparison with experimental data for natural peridotite systems. The older O'Neill and Wood (Contrib Mineral Petrol 70:59-70, 1979) version of the olivine-garnet Fe-Mg thermometer and all popular versions of the clinopyroxene-garnet Fe-Mg thermometer show unacceptably low precision, with discrepancies exceeding 200°C when compared to TA98 results for well-equilibrated xenoliths. Empirical correction to the Brey and Ko¨hler (J Petrol 31:1353-1378, 1990) Ca-in-Opx thermometer and recalibration of the orthopyroxene-garnet thermometer, using well-equilibrated mantle xenoliths and TA98 temperatures as calibrants, are provided in this study to ensure consistency with TA98 estimates in the range 700-1,400°C. Observed discrepancies between the new orthopyroxene-garnet thermometer and TA98 for some localities can be interpreted in the light of orthopyroxene-garnet Fe3+ partitioning systematics and suggest localized and lateral variations in mantle redox conditions, in broad agreement with existing oxybarometric data. Kinetic decoupling of Ca-Mg and Fe-Mg exchange equilibria caused by transient heating appears to be common, but not ubiquitous, near the base of the lithosphere. (literal)
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