LE3 .A278 2010

2010

Barr, Sandra

Acadia University

Bachelor of Science

Honours

Geology

Earth & Environmental Sciences

A gneissic inlier approximately 5 km by 1.75 km is located around Hemlock Hill in the Meguma terrane approximately 13 km south of Windsor, Nova Scotia. Two smaller ( 1 km by 0.2 km) gneissic inliers occur approximately 6 km southeast of the main unit. Ambiguity as to the petrology, age, and provenance of the Hemlock Hill gneiss had led to previous speculation that it may be older than other units in the Meguma terrane and might represent the basement that underlies the terrane. To investigate this possibility, geological mapping was conducted in the gneiss and surrounding units, which resulted in a better understanding of extent and contact relationships of the gneiss, and its internal structure. Petrographic studies of samples collected from the gneiss revealed contact metamorphic mineral assemblages that fall within hornblende hornfels and pyroxene hornfels facies. Metamorphic mineral assemblages and compositions indicate that contact metamorphism at maximum P- T conditions of 645° C and ca. 0.2 GPa produced cordierite, andalusite, and sillimanite and overprinted regional low- grade metamorphism. Relict bedding and foliation in the gneiss are generally parallel. The geologic structural features of the Hemlock Hill gneiss are concordant with those in the Cambrian- Ordovician Goldenville and Halifax groups, and lithological characteristics of the gneiss indicate its stratigraphic position is in the Government Point Formation of the Goldenville Group, ruling out speculation that it is Meguma terrane basement. The Hemlock Hill gneiss is likely to be a roof pendant of the Goldenville Group in the South Mountain Batholith, whereas the smaller gneissic outliers are large rafts.

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https://scholar.acadiau.ca/islandora/object/theses:661