Robert James Ryan
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Ph. D. Thesis
Metallogenetic and Thermal Evolution of the Upper Paleozoic Maritimes Basin: Evidence from the Cumberland Basin of Nova Scotia
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The Cumberland Basin is the largest onland segment of the Late Paleozoic Maritimes Basin. The Maritimes Basin is made up of up to 7 km of primarily continental clastic strata that presently cover a large area of onshore and offshroe Atlantic Canada. The basin is host to signficant resoures of metallic minerals, industrial minerals and coal. In addition to these resources the basin has recently been the focus of exploration for coal- bed methane. A better assessment of the mineral potential is made possible by the clearer understanding of the thermal and metallogenetic evolution of the basin derived from this study. This thesis integrates four separate, but interdependent components: 1) geological constraints from the stratigraphy, sedimentology, and structure, 2) a detailed thermochronological study including apatite fission track analysis, 3) a study of the metallic mineral occurrences of the Cumberland basin, and 4) an evaluation of time-temperature constraints which were applied to the metallogenetic models.
Quantitative thermochronological evidence presented here suggests that an additional 1 to 4 km of strata were deposited throughout the Maritimes Basin and subsequently eroded. These sediments accumulated to a maximum thickness in the Permian (ca. 280 Ma), and were eroded during an exhumation that preceded the Triassic/Jurassic rifting of the Atlantic margin (ca. 200 Ma).
Redbed hosted Cu-Ag (+ U-Pb-Zn) deposits of the Cumberland Basin are genetically related to the process of diagenetic reddening (hematitization) that affected the strata. This reddening developed during the Permo-Triassic exhumation of the basin, when gravity driven oxygenated groundwaters leached metals from the sandstones and conglomerates, and concentrated them in areas rich in reductants.
The time-temperature history reconstructed for the basin poses strict constraints to the time of maximum coalification of peat in Carboniferous strata (280 Ma), and to models of fluid-expulsion and Zn-Pb-barite mineralization in Carboniferous carbonates (pre maximum burial: pre-280 Ma). The peak temperatures in the basin were attained in the Permian, consequently any syn-sedimentary or early diagenetic mineralization that might exist has been thermally modified, and may be difficult to recognize or date accurately.
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Supervisor: Marcos Zentilli