John D. Cullen
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M. Sc. Thesis
Metamorphic Petrology and Geochemistry of the Goldenville Formation Metasediments, Yarmouth, Nova Scotia
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Detailed petrological and geochemical studies in the Goldenville Formation of the Lower Paleozoic Meguma Group metasediments near Yarmouth, Nova Scotia, indicate that this sequence was affected by regional metamorphism ( 415 Ma, c.f. Reynolds et al., 1978) under conditions of low pressure ( 3kb) and low grade (400-470oC). Biotite formation occurred by a reaction involving muscovite and ankerite. In the system SiO2-Al2O3 MgO-K2O-CaO-H2O-CO2, the reactant and product components of reaction may be represented as follows:
| KAl3Si3O10(OH)2 | 3SiO2 | + | 8CaMg(CO3)2+ 4H2O | |
| (muscovite) | (quartz) | (dolomite) | ||
| 8CaCO3 | + | KMg3AlSi3O10(OH)2 | + | Ca2Al2Si3O12(OH) + 8CO2 |
| (calcite) | (phlogopite) | (epidote) |
This reaction terminated when the dolomite-component was entirely consumed.
The regionally metamorphosed sediments were subsequently intruded by the Wedgeport pluton ( 310 Ma; Keppie, J. D., pers. comm., 1983). This resulted in the development of a localized contact aureole with mineral assemblages characteristic of the hornblende-hornfels facies (c.f. Turner, 1981). The physical conditions of contact metamorphism were as follows:
PH2O = 1000 - 3000 bars
T = 550 - 700oC
The effects of a hydrothermal event ( 300 Ma (??), Reynolds et al., 1981) associated with the late stages of granite intrusion, are present within the metasediments. Chalcopyrite-pyrite-sphalerite-cassiterite mineralization has been localized within pre-existing, NE-SW trending shear zones within the metamorphosed Goldenville Formation lithologies. These zones display extensive alteration "halos" where chemically and optically distinctive secondary chlorites, biotites and garnets have been recrystallized from the pre-existing biotite zone assemblages. Secondary biotites, enriched in Mn and F, have formed along the margins of chalcopyrite-pyrrhotite-pyrite-arsenopyrite-sphalerite-cassiterite bearing quartz-calcite veinlets within the metasediments.
Late-stage NNE-SSW trending, strike-slip faulting and shearing offset portions of the mineralized Wedgeport pluton. The mica-argon age of 258 Ma (c.f. Reynolds et al., 1981) may, at least in part, record this late deformational event.
Olivine diabase and lamprophyre dykes some of which are Triassic in age, intruded the Wedgeport pluton commonly along northeast southwest trending faults and the Goldenville Formation metasediments along pre-existing shear zones.
Keywords:
Pages: 257
Supervisor: Gunter Muecke