A transmission electron microscopy study of the crystallographic characteristics of magnetite needles in plagioclase

Hwang, S.-L.; Shen, P.; Yui, T.-F.; Chu, H.-T.; Usui, Y.

doi:10.1107/S160057672301004X

Figure 1
Optical micrographs under cross polarizers. (a) Bimodal sizes of plagioclase crystals with significant bending of (010) twin lamellae in a large crystal coupled with closure/orthogonal twin lamellae for the finer-grain aggregate by dynamic recrystallization. (b) The predominant 112*-needles (∼horizontal) and the subordinate $[\bar {\bf 3}]$ 12*-needles (∼vertical) at grain interiors, as well as (c) the very minor, short 150* and $[\bar {\bf 1}]$ 50*-needles crystallized at the (010)_p twin boundary within the small recrystallized crystal. (d) One large primary crystal with multiple thin (010)_p twin lamellae and the almost orthogonal (001)_p Manebach twin boundary which contains rather coarse and long $[\bar {\bf 3}]$ 12*, 150* and $[\bar {\bf 1}]$ 50*-needles that apparently crystallized at either (e) the (010)_p twin boundary or (f) the second phase inclusions. (g) The minor long [ $[\bar 7\bar 1]$ 4]-needle conjugated to the $[\bar {\bf 3}]$ 12*-needle. (h) Another large plagioclase crystal with (i) one specific core domain containing abundant, very coarse [001]-needles in association with fine and coarse 112* and $[\bar {\bf 3}]$ 12*-needles. (j) The Na X-ray mapping showing Na enrichment in the specific core domain.

JOURNAL OF
APPLIED
CRYSTALLOGRAPHY

ISSN: 1600-5767

Volume 57| Part 1| February 2024| Pages 71-87

https://doi.org/10.1107/S160057672301004X

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