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Details van artikel 7 van 17 gevonden artikelen
| Titel: |
PGE in the upper Proterozoic Dovirensky layered complex, North Baikal area, Siberia |
| Auteur: |
Papunen, H. Distler, V. Sokolov, A. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 39 (1992) nr. 3 pagina's 327-334 |
| Jaar: |
1992-07 |
| Inhoud: |
The upper Proterozoic Dovirensky layered complex has a strike length of 26 km and a stratigraphic thickness of about 3.2 km. The intrusion was emplaced 739 ± 55 Ma in the Proterozoic Baikal-Vitim volcano-sedimentary belt which is located between the Archaean Aldan Shield and the Siberian Platform. The supracrustal sequence was deformed and metamorphosed in a low amphibolite facies before the intrusion. The complex, with northwest strike and subvertical dip, is composed of a 1100 m thick ultramafic basal part of dunite overlain by a 300 m thick sequence of troctolite which grades upwards to a 1.3 km thick layered sequence of troctolite and olivine gabbro. Diopside oikocrysts characterize the transition zone from dunite to troctolite, and plagioclase and diopside oikocrysts characterize the zone from troctolite to olivine gabbro. A massive gabbronorite intruded the uppermost part, and gabbronoritic veins and sills are encountered in the lower part of the complex. Thin layers of anorthosite occur in troctolite. The major part of the complex is fresh and unaltered, only the lower marginal portion being hydrated and serpentinized, possibly in association with the dehydration reactions noted in the wall rocks of the contact zone. Sills of plagioclase-bearing peridotite, representing the first magma intrusion pulse, are abundant in the wall rock and in the lower marginal portion of the complex. Disseminated sulphides in plagioclase-bearing peridotites are interpreted as a result of wall rock contamination; weak sulphide dissemination also exists throughout the dunitic lower portion of the complex. Sulphides are abundant in the upper part of the dunite, where altered zenoliths of calcareous wall rock occur as discontinuous layers. Heavy dissemination of nickeliferous sulphides occurs in the plagioperidotite of the lower marginal portion, close to the northeastern end, where sulphidic metasediments form the wall rocks of the complex. Thin zones of remobilized massive and brecciated sulphides intersect the primary layering. Contents of platinum-group elements (PGE) are low throughout the disseminated sulphides, but remobilized Cu-rich sulphide breccias have accumulated Pd, highest tenors being up to 1.4 p.p.m. Pd. The primary silicate melt was considered to be sulphide unsaturated, but it became saturated by wall rock contamination. The model of contamination is supported by low Se/S, high REE and incompatible element contents of the plagioperidotite sills. The existence of cryptic PGE-rich layers has been considered unlikely in the layered troctolite-olivine gabbro sequence. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 7 van 17 gevonden artikelen
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