Whiteschist

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A whiteschist is an uncommon

intrusions.[2][3][4] Whiteschists form in the MgO–Fe
2O
3–Al
2O
3–SiO
2–H
2O (MFASH) system.[5] Rocks of this primary chemistry are extremely uncommon and they are in most cases thought to be the result of metasomatic alteration, with the removal of various mobile elements.[3]

Occurrence

Whiteschists occur as lenses or tectonic slices on a metre to kilometre scale within nine

metabasalt to granite.[3]

Formation

Whiteschists have a chemistry that only very rarely occurs as the primary composition of rocks. This implies that they can only form under conditions where other chemical components have been removed by large scale metasomatism, strongly altering the original rock composition. The mobile components that may be removed include Na
2O, CaO, K
2O, MnO, P
2O
5, Rb, Ba, Th. Another feature of whiteschists is that iron and manganese only occur in their highest

plagioclase → kyanite + talc + quartz + Fe(hematite) + Na, Ca, K, Mn (fluid) has been described from an altered amphibolite, suggesting that the original reaction may be insufficient to describe the full stability range of the kyanite + talc assemblage under high oxygen fugacity conditions.[3]

References

  1. S2CID 128944616
    .
  2. S2CID 129384880
    .
  3. ^ a b c d e f Johnson, J. "Preliminary investigation of in-situ, high-pressure, high-ƒO2 metasomatism and metamorphism of meta-basalt to whiteschist" (PDF). Frontier Research on Earth Evolution. 1. Retrieved 21 December 2011.
  4. doi:10.1127/0935-1221/2000/0012-0883
    . Retrieved 21 December 2011.
  5. ISBN 978-0-521-42740-1
    . Retrieved 21 December 2011.
  6. doi:10.1016/0040-1951(77)90009-9
    .
  7. S2CID 73549945
    . Retrieved 21 December 2011.
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