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Details van artikel 10 van 17 gevonden artikelen
| Titel: |
Platinum-group element mineralization in the Suhanko-Konttijarvi intrusion, Finland |
| Auteur: |
Iljina, M. J. Alapieti, T. T. McElduff, B. M. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 39 (1992) nr. 3 pagina's 303-313 |
| Jaar: |
1992-07 |
| Inhoud: |
Igneous activity of ca 2440 Ma in the Suhanko-Konttijarvi area began with the formation of pre-intrusion dykes followed by the intrusion of the Suhanko-Konttijarvi intrusion proper. The two magma pulses differed from each other in their chemical composition, the former being clearly richer in chromium and magnesium and interpreted as a boninitic-type magma. Three principal types of platinum-group element (PGE) mineralization are present in the Suhanko-Konttijarvi intrusion: (1) disseminated PGE-bearing Cu-Ni-Fe sulphide mineralization in the marginal series, pre-intrusion dykes and adjacent granitoids; (2) PGE-bearing massive pyrrhotite deposits close to the basal contact of the Suhanko body; and (3) the Rytikangas Reef in the Suhanko layered series. The presence of high PGE contents in a pre-intrusion dyke shows that it was mineralized before the main magma intrusion. The marginal series of the main intrusion is also more highly mineralized in the areas where the pre-intrusion dykes are encountered. This has led to the interpretation that the fractionation product of the pre-intrusion magma and the new primitive magma were able to mix in those areas. Simultaneously, wall rock contamination led to sulphur saturation and formation of an immiscible sulphide melt. Scavenging by this sulphide melt was responsible for some PGE concentration, especially within the massive pyrrhotite deposits. The Rytikangas Reef consists of platinum-group minerals (PGM) with or without disseminated sulphides in poikilitic gabbros and pegmatoids about 170 m above the base of the intrusion. Platinum-group element ratios and normalized metal patterns of the pre-intrusion dyke, the high-grade disseminated Konttijarvi marginal series and the Rytikangas Reef resemble each other and their whole-rock Se/S ratios are high ((Se/S) x 106 = 290-1740), differing markedly from the low PGE-grade marginal series mineralization ((Se/S) x 106 < 130). This leads to the conclusion that the Rytikangas Reef may also be related to upward migration of the PGE-enriched fluid phase brought into the system by the early boninitic-type magma. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 10 van 17 gevonden artikelen
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