Variable water pressure metamorphic assemblages in the Meguma Group, Nova Scotia

Amphibolite grade pelites from the Buchan type metamorphism of the Meguma Group in southwestern Nova Scotia contain the assemblage And+Grt+Bt+Q+Pl+Ms+Ilm+Mgt±St±Crd±Sil±Po±Py. Grt-Bt geothermometry and Pl-Grt-And-Q geobarometry on samples from three widely separated 3-8 km traverses yield temperatures and pressures that cluster in two groups; (1) two traverses near Shelburne with T=500-510°C and P=3.5 kbar; and (2) one traverse on the West Pubnico peninsula, 40 km to the southwest, with T=530-560°C and P=1.5-2. 5 kbar. P_H₂O estimates based on Ms-and-Pl-V assemblages indicate that P_H₂O = .4-.9 P_Total for rocks from the Shelburne area and P_H₂O=P_Total for the rocks south of West Pubnico. Whole rock chemical analyses on samples from the three traverses show no systematic variations over the region. In the Pubnico traverse, the presence or absence of staurolite is dependent both on slight variations in the Fe/Mg ratios of the rocks and on temperature differences. In the staurolite-bearing rocks the assemblages and mineral chemistries indicate that the systems represent divariant continuous reactions and contain cordierite only where P_H₂O < P_Total. Thus the large number of phases is neither the result of disequilibrium nor representative of a low variance assemblage, but can be described as a divariant assemblage involving 8 to 9 major components.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Geology

Department dc:contributor.department

Geology

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1984

Author dc:creator

• Sage, Janet D.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/76028

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/76028