Dear all,

We are currently working on prograde HP/UHP metamorphism of ultramafic rocks from the eclogite-bearing uppermost Allochthon of the Caledonides. One of the rock types we have found mainly consists of the rather rare assemblage pyrope-rich garnet + pargasite + zoisite. In garnet and pargasite we have found tiny inclusions of Mg-rich staurolite. In one sample staurolite included in Cr-pargasite contains considerable amounts of Cr, which also seems to be unusual.

 

Average compositions of staurolite from these two samples are (normalized to 100%):

 

In grt     In Cr-pargasite

SiO2                27.31                28.11

Al2O3               59.90                53.94

Cr2O3                                        5.68

FeO                   4.38                 3.64

MgO                   8.40                 8.63

 

Does anyone know about Cr-bearing staurolite from other areas?

 

 

Erling