Dolomitization, brecciation and zinc mineralization and their paragenetic, stratigraphic and structural relationships in the Upper St.George Group (Ordovician) at Daniel's Harbour, western Newfoundland
The sphalerite deposit at Newfoundland Zinc Mines near Daniels Harbour, western Newfoundland is situated in the upper part of the Lower Ordovician St. George Group, a complex of dolostones, limestones and breccias in the middle of a Lower Paleozoic shallow-water, carbonate platform sequence. It is a...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
1990
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| Online Access: | https://research.library.mun.ca/6614/ https://research.library.mun.ca/6614/1/ThomasEdwardLane.pdf https://research.library.mun.ca/6614/3/ThomasEdwardLane.pdf |
| Summary: | The sphalerite deposit at Newfoundland Zinc Mines near Daniels Harbour, western Newfoundland is situated in the upper part of the Lower Ordovician St. George Group, a complex of dolostones, limestones and breccias in the middle of a Lower Paleozoic shallow-water, carbonate platform sequence. It is a zinc-dominated Mississippi Valley Type (MVT) deposit, a subtype of MVTs that is characteristic of the Appalachians. This study shows that zinc mineralization occurred during one phase of a complex history of repeated dolomitization and fracturing of the host carbonates along northeast-trending lineaments. This history is interpreted through an integrated analysis of the sedimentologic, stratigraphic and structural framework, petrography, cathodoluminescence and geochemistry. -- The upper St. George Group carbonates were deposited along the edge of the tropical Iapetus Ocean during Early to early Middle Ordovician time when the passive continental margin began to experience the initial effects of plate convergence. Shallow subtidal muddy carbonates (Catoche Formation) shallowed upwards into restricted-water, rhythmically interbedded peloidal grainstones and mudstones (Peloidal or Costa Bay Member) and peritidal laminites and burrow-mottled mudstones (Aguathuna Formation). Deformation and fragmentation of the platform and marine regression during early Middle Ordovician time resulted in the regional St. George Unconformity and the formation of rock-matrix breccias from subsurface karst. The mine stratigraphy records a minimum of 5 stages of faulting, subsurface dissolution and erosion of the platform at this time. The platform was gradually flooded during Middle Ordovician time as the upper member of the Aguathuna Formation and limestones of the Table Point Formation were deposited over the St. George Unconformity. Continued convergence of the continental margin caused collapse of the platform and generation of a foreland basin in which a thick sequence of siliciclastic flysch was deposited and eventually overridden by ... |
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