麻豆传媒

The structure and petrology of the Port Felix area, Guysborough Co., N.S., was investigated with the aim of establishing a structural-metamorphic sequence of events.

Three episodes of deformation are seen to have deformed the pelitic metasediments of the Meguma Group. The oldest folds (F1) are found in two styles, disharmonic and mullion, and plunge in easterly and westerly directions at angles of 60o and less. A second fold set (F2) is also found in two styles, disharmonic and isoclinal. It plunges in more north-easterly and south-westerly directions at shallower angles, and forms interference patterns with the earlier folds. The third set of folds (F3) consists of both rooted and non-rooted intrafolial folds which usually include a tension gash oriented axial planar to the folds.

The pervasive regional cleavage (S2) is axial planar to the F2 folds. This cleavage is deformed by the intrafolial folds (F3) and a transposition cleavage (S3) is encountered in the cores of these folds. Outside the folds of the same deformation has produced a crenulation of S2 cleavage surfaces.

The area was intruded by granitic plutons and sills in the mid-Devonian. Intrusions occurred between the development of the S1 and S2 foliations in this area. The S1 foliation is found included in the contact metamorphic minerals, and the S2 has intensely sheared the granite bodies.

Two episodes of andalusite growth have been distinguished in the area. Prismatic andalusite formed during contact metamorphism which extended into the initial phases of the second deformation. Blocky andalusites did not crystallize until the initial phases of the third deformation and record the early stages of intrafolial fold formation in their inclusion traces.

The first and third deformations manifest in the area can be correlated directly with deformations in the remainder of the Meguma massif to the west. The second episode which has foliated the granite bodies, appears to be local. The stress field visualized for the second deformation conforms with conditions necessary for transcurrent movement along the Chedabucto Fault 7 km to the north of the map area. Since initiation of the second deformation coincides with the waning stages of contact metamorphism, movement along the Chedabucto fault may have initiated shortly after granite emplacement in the mid-Devonian.

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Pages: 83
Supervisor: Gunter Muecke