At 15:45 09/11/01 -0500, vous avez écrit:
>Dugald and all,
> The two type localities of Turner for the amphibolite-granulite
>transition are the NW Adirondacks and Broken Hill. Based on our
>observations in the NW Adirondacks, the amphibolite - granulite transition
>in metamafites appears to be prograde with pyroxenes generally rimming the
>hornblendes. David Jenkins recently had a student reexamining this
the granulitic massif from Madagascar, I speak about in my precedent mail
is similar to the Adirondacks massif (with also large anorthosite massifs).
There is also the amphibolite - granulite transition in metamafites. But I
don't know if it is a prograde or retrograde transition ! Cooling of mafic
magma at different levels of the crust ?.... but, recent chhronology
(Ashval) indicate 100MA between the magmatism and the metamorphism....
Independently of the path, these rocks reached the facies granulite
> At Broken Hill, Neil Phillip's observations are that it is a
>retrograde transition. In both localities the evidence for involvement of
>melting in mafic rocks at the transition is not strong, ....