The effect of oxo-component on the high-pressure behavior of amphiboles. (Articolo in rivista)

Type
Label
  • The effect of oxo-component on the high-pressure behavior of amphiboles. (Articolo in rivista) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.2138/am.2010.3429 (literal)
Alternative label
  • Comodi P.; Boffa Ballaran T.; Zanazzi P.; Capalbo C.; Zanetti A.; Nazzareni S. (2010)
    The effect of oxo-component on the high-pressure behavior of amphiboles.
    in The American mineralogist
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Comodi P.; Boffa Ballaran T.; Zanazzi P.; Capalbo C.; Zanetti A.; Nazzareni S. (literal)
Pagina inizio
  • 1042 (literal)
Pagina fine
  • 1051 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 95 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#note
  • In: American Mineralogist, vol. 95 (7) pp. 1042 - 1051. Mineralogical Society of America, 2010. (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Comodi P. a; Boffa Ballaran T. b; Zanazzi P. a; Capalbo C. a; Zanetti A. c; Nazzareni S. a: a Dipartimento di Scienze della Terra, Università di Perugia, 06100 Perugia, Italy; b Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany; c CNR--Istituto di Geoscienze e Georisorse, 27100 Pavia, Italy (literal)
Titolo
  • The effect of oxo-component on the high-pressure behavior of amphiboles. (literal)
Abstract
  • The role of the oxo-component on the compressibility of amphibole was studied by means of high-pressure in situ single-crystal X-ray diffraction on two natural kaersutite megacrysts (samples DL5 and FR12) from alkaline basalts. The oxo-component varies significantly (1.1 and 1.9 apfu in DL5 and FR12, respectively), whereas the cation composition is very similar, apart from the Fe3+/(Fe2++Fe3+), which is 0.33 in DL5 and ~1 in FR12. The larger oxo-component of FR12 is attributed to the Fe2+ + OH- = Fe3+ + O2- + ½H2 substitution. Unit-cell parameters were collected at different pressures up to about 8 GPa. Structural refinements of both samples were performed with data collected at different P up to 6 GPa. Fitting the P-V data to a third-order Birch Murnaghan EoS yielded the following parameters: K0 = 94(1) GPa, K? = 6.3(4), and V0 = 903.6(2) Å3 for FR12 and K0 = 91(2) GPa, K? = 6.2(4), and V0 = 914.1(2) Å3 for DL5. The axial moduli of the two amphibole samples were: K0a = 86(3) GPa, K?a = 7(1), and a0 = 9.815(2) Å; K0b = 115(3) GPa, K?b = 4.8(8), and b0 = 18.012(2) Å; K0c = 112(5) GPa, K?c = 7(1), and c0 = 5.300(1) Å for sample FR12 and K0a = 85(3) GPa, K?a = 5(1), and a0 = 9.8660(9) Å; K0b = 113(2), K?b = 4.4(6), and b0 = 18.0548(6) Å; K0c = 107(3) GPa, K?c = 7(1), and c0 = 5.3185(5) Å for sample DL5. This suggests that the compressibility of kaersutite decreases with increasing oxo-component. Structural refinements show that the polyhedral compressibility follows the order A = M4 > M2 > M3 > M1 for DL5 and A = M4 > M2 > M1 > M3 for FR12. The most evident geometrical effect induced by P is the decrease in the bending of the double tetrahedral chain, when adjacent I-beams are pushed against each other. This effect is largest for DL5, which has a larger concavity of the A site, (O7-O7? changes from 3.03 to 2.82 Å) compared to the one of FR12, (O7-O7? changes from 2.92 to 2.79 Å). This mechanism is confirmed by the evolution of T1-O7-T1 angle (from 135.4° to 132.5° in FR12 and from 136.6° to 132.2° in DL5). (literal)
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