Wednesday, April 17, 2019

Geosonnet 52



Peridotite, without the peridot
A paradox, clinopyroxenite
What metasomatized this mantle plot
Reacting mantle min’rals out of sight?
A garnet, like an elephant, forgets
No detail of its formative hot years
Included in its structure, tiny bits
Of felsic melt, the mantle’s frozen tears
A crustal rock’s subducted ‘till it melts
The rock’s identity is not air tight
Melanosome in metamorphic belts?
Or metasomatized old hartzburgite?
The isotopes of osmium declare
They’d solve this if they weren’t so very rare



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