| dc.description.abstract | Contact metamorphism resulting from intrusion of the South Mountain Batholith
(SMB) at 372 Ma produced textural and mineralogical changes in rocks of the Meguma
Supergroup. A detailed petrographic study of the contact aureole of the Halifax Group
was conducted to determine the relationship between sulphide and silicate mineral
assemblages, and the relationship of these assemblages to metamorphic fabrics.
Field relations indicate that rocks in the contact aureole of the SMB contain
structures formed during regional deformation which were overprinted by contact
metamorphism. The samples collected were grouped according to silicate porphyroblast
assemblage into six groups which show systematic variation with distance from the
contact. Sulphide mineral assemblages show little to no variation with distance from the
contact. Microprobe analyses of both sulphides and silicates show little compositional
variation throughout the study area. Petrographic analyses show· that regional cleavage
(S 1) developed before cordierite growth and was reactivated to form a syn-emplacement
fabric (S2) prior to andalusite growth. Maximum P-T conditions are estimated at 2.5-3.0
kbar and 590-620°C, using Pattison and Tracy's (1991) phase diagram for pelites.
The silicate mineral assemblage of Halifax Group rocks in the contact aureole of
the SMB varies systematically with distance from the contact and is therefore thermally
controlled. The sulphide mineral assemblage, as determined from petrography, mineral
chemistry, and field data is lithologically controlled in the contact aureole and therefore
has no direct relationship to contact metamorphism. In conclusion, the complicated
relationships of porphyroblasts and fabrics in the contact aureole of the SMB result from
deformation and thermal effects superimposed on lithological variations.
KEYWORDS: South Mountain Batholith, Meguma Supergroup, contact metamorphism,
pelites, silicates, sulphides. | en_US |
