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A second natural occurrence of yoderite
Author(s) -
JOHNSON S. P.,
OLIVER* G. J. H.
Publication year - 1998
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1998.00172.x
Subject(s) - kyanite , geology , chlorite , metamorphic rock , geochemistry , talc , ophiolite , mineralogy , hematite , mineral , quartz , paleontology , chemistry , organic chemistry , tectonics
A second example of yoderite has been discovered in whiteschists from the Southern Chewore Hills of northern Zimbabwe. The mineral is pale green in colour and occurs in an equilibrium assemblage with talc+chlorite+kyanite+dravite+hematite. There is no quartz present. Recalculated microprobe analyses give a structural formula of Mg 2 Al 5.7 Fe 0.3 Si 4 O 18 (OH) 2 , similar to that obtained for the type locality at Mautia Hill, Tanzania, i.e. Mg 2 Al 5.6 Fe 0.4 Si 4 O 18 (OH) 2 . Textural relationships and relative proportions of minerals suggest that the yoderite was formed by reaction between talc, chlorite, kyanite and hematite. Experimental evidence suggests high‐water‐pressure metamorphic conditions at temperatures exceeding a reaction curve that extends between 13 kbar at 590 °C and 21 kbar at 650 °C. The yoderite‐bearing whiteschist is associated with a 1.4 Ga dismembered ophiolite. It is proposed that this yoderite occurrence is associated with a relict subduction/suture zone.