A petrographic and geochemical characterization and the evaluation of the exploration potential for nickel sulfides in several mafic-ultramafic intrusive complexes in Newfoundland
On the island of Newfoundland a number of mafic- to ultramafic intrusions are exposed; most commonly in the Dunnage Zone. These intrusive suites occur in a variety of tectonic environments, and have variable relationships with their host rocks. Nickel is extracted from intrusive rocks of similar com...
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
Memorial University of Newfoundland
2007
|
| Subjects: | |
| Online Access: | https://research.library.mun.ca/6648/ https://research.library.mun.ca/6648/1/PatrickGCollins.pdf https://research.library.mun.ca/6648/3/PatrickGCollins.pdf |
| Summary: | On the island of Newfoundland a number of mafic- to ultramafic intrusions are exposed; most commonly in the Dunnage Zone. These intrusive suites occur in a variety of tectonic environments, and have variable relationships with their host rocks. Nickel is extracted from intrusive rocks of similar compositions throughout the world. This thesis evaluates the potential of three intrusive complexes in Newfoundland to host economic Ni-Cu sulphide and/or platinum group element (PGE) mineralization. -- The Red Cross Lake Intrusive Suite (RCLIS), located in central Newfoundland, is a ca. 431 Ma layered, mafic- to ultramafic intrusion. The Steel Mountain Anorthosite (SMA), located east of Stephenville, in the Southern Long Range Mountains, is a ca. 1275 Ma massive-type anorthosite that hosts abundant Fe-Ti oxides and variable mafic zones. The Taylor Brook Gabbro Suite (TBGS), located southeast of western White Bay, is a ca. 430 Ma gabbroic suite. -- The RCLIS is divided into an Upper and Lower Series (US and LS respectively). The LS is comprised of predominantly gabbro and troctolite layers with minor dunite, olivine gabbro and serpentinite. The US had a gabbroic- to leucogabbroic protolith that is variably altered to pyroxene amphibole gabbro. Geochemical data indicate the RCLIS exhibits an intermediate to alkaline and sub-alkaline composition and is tholeiitic. The RCLIS evolved through fractional crystallization; it exhibits a progressive decrease in MgO and an increase in FeO+Ti0₂ from the LS to the US. Sulfides comprise at most only a few weight percent; the maximum values are from country rock samples. Magmatic sulfides in the LS locally exhibit a high Ni tenor. Plagioclase composition averages An 69 in the LS and An 54 in the US, whereas paragneiss xenolith samples average An 47. Olivine composition averages Fo 83 in the LS and Fo 56 for the US; xenoliths average Fo 36. LS olivine is locally Ni-depleted with respect to its Fo content. δ³⁴S ratios exhibit a range of 5.64‰, from -1.79‰ to +3.85‰. The heaviest ratio ... |
|---|