caa a22 4500 465790984 CHVBK 20180323112024.0 cr unu---uuuuu 170327e19900701xx s 000 0 eng 10.1007/BF01575624 doi (NATIONALLICENCE)springer-10.1007/BF01575624 Calibration of Al/Si order variations in anorthite [Elektronische Daten] [M. Carpenter, R. Angel, L. Finger] New single crystal diffraction data for natural and heat-treated anorthite crystals (Angel et al. 1990) allow the determination of their states of Al/Si order in terms of a macroscopic order parameter,Q OD , for the transition. Numerical values ofQ OD obtained from estimates of site occupancies are shown to vary with the scalar spontaneous strain, ε s , as ε s ∝Q OD 2 , and with the ratio of the sums of typeb (superlattice) reflections and typea (sublattice) reflections asΣI b/ΣI a ∝Q OD 2 . An empirical calibration for pure anorthite is obtained giving $$Q_{OD} = 10.1\left( 5 \right)\sqrt {\varepsilon _s } $$ varies between ∼ 0.92 and ∼ 0.87 in samples equilibrated at T≤1300° C, but then falls off relatively rapidly with increasing temperature, reaching ∼ 0.7 near the melting point (∼ 1557° C). The observed temperature dependence does not conform to the predictions of the simplest single order parameter models; coupling ofQ OD withQ of the transition is suspeeted. Springer-Verlag, 1990 Carpenter M. Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ, Cambridge, England aut Angel R. Department of Geological Sciences, University College London, Gower Street, WC1E 6BT, London, England aut Finger L. Department of Crystallography, Birkbeck College, Malet Street, WC1E 7HX, London, England aut Contributions to Mineralogy and Petrology Springer-Verlag 104/4(1990-07-01), 471-480 0010-7999 104:4<471 1990 104 410 https://doi.org/10.1007/BF01575624 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01575624 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Carpenter M. Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ, Cambridge, England aut NATIONALLICENCE 700 1- Angel R. Department of Geological Sciences, University College London, Gower Street, WC1E 6BT, London, England aut NATIONALLICENCE 700 1- Finger L. Department of Crystallography, Birkbeck College, Malet Street, WC1E 7HX, London, England aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 104/4(1990-07-01), 471-480 0010-7999 104:4<471 1990 104 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer