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Galena
impregnating fine-grained turbidite sandstone
wallrock from Leri Valley mine, Talybont (L). The effect only goes in a
few mm from the vein margin. This texture is quite rare in Central
Wales, and appears to be limited to the early, complex polymetallic
mineralisation.
Later
mineralising events have generally
started with the deposition of a thin (just visible in this case!)
layer of quartz on wallrock clasts (R), thus forming a barrier to
subsequent fluids. In general, ore petrologists will find later Central
Wales galenas relatively disappointing - hardly any inclusions or much
else of note (as a very general rule!!).
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