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The strong, MARID-type, K-metasomatism, characterized by abundant clinopyroxenite and glimmerite veins and phlogopite stockworks, also indicates that potassic melts have circulated in Kondyor.
The ultramafic rocks are subdivided into three units: Nb, Ta, Zr, Hf show negative anomalies relative to neighbouring elements Fig. Distribution of non-lithostatic pressure component around the intrusion and the SMSR for emplacement stages from 11 to 63 kyr. The role of Tpo 2 O during crystallization of primitive arc magmas under uppermost mantle conditions and genesis of igneous pyroxenites; an experimental study.
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Channel spreading is a rapid event 10—20 kyr. Textures and fabrics of peridotite nodules from kimberlite at Mothae, Thaba Putsoa and Kimberley.
These small intrusions are either derived from later crustal melting or are the most mobile magmas from the magma source region that have taken advantage of domsl zones forming in front of the rising ultramafic body, while space was created by thinning and separation of fault blocks in the crust Fig. The tectonics of the Platinum-Bearing Belt of the Urals: In the cumulate hypothesis, the relatively low Ni content of the dunites would imply domsl their parental melt had previously undergone some degree of olivine fractional crystallization.
Do,al review of their occurrence and chemical characteristics and speculations on their petrogenesis. Origin of the Tulameen ultramafic—gabbro complex, southern British Columbia. Further constraints rop based on the fact that the partially molten rocks that produced the Kondyor peridotites have intruded the lower crust, possibly up to the middle crust, but not the upper crust.
The strong positive buoyancy of the SMSR with respect to the overlying mantle lithosphere governs this pressure distribution.
The flat foliation suggests that the present tp of erosion exposes the domal top of the intrusion, and that the synformal structure could result from internal sagging. Upward-diverging conjugate faults form at shallow depth and cause the slightly curved, widening-up shape of the intrusion top. Mesozoic potassic magmatism of the Central Aldan: Time kyr is given in the figures.
The bulk synformal structure of the dunite foliation seems something of a paradox in the context of the Kondyor dome defined by the surrounding Riphean sediments. Model kofz reproduces the prevalence of ultramafic rocks surrounded by basic rocks and deep crustal wedges dragged up along the intrusion boundaries to the surface.
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We report new structural, microstructural, petrological, and ttb and trace-element data on ultramafic rocks from the Kondyor zoned ultramafic complex in Far-East Russia. This olivine fabric is inherited from the dunite protolith, as the interstitial clinopyroxene is devoid of plastic deformation. Acceptable shortcomings of model topp concern the attitude of the body subvertical in Kondyor and inclined in the modelthe internal rock distribution, the synformal final shape and the rim plutons.
Field relationships between lithologies. Contact metamorphism is recognized in a — m wide aureole of hornfelsed Riphean sediments Orlova, ranging from partial melting Fig.
These numerical conditions limit the parameter space for Kondyor-like models. Distribution of rock layers in the intrusion area during emplacement of the ultramafic body into the crust from below the lithosphere via the magmatic channel.
Preliminary results of a study of magnetic properties in the Foum-Zguid dyke Morocco. View large Download slide. Intraplate ZUCs are associated with alkaline and locally subalkaline magmatic rocks e. These fluids probably assist the rise of the ultramafic body, a lubricating effect that was not implemented in our model. The dunite texture varies from coarse-grained 2—3 cmsometimes tabular, in the core to fine-grained against the rim contact. In this scheme, translithospheric mantle diapirism should be a common mechanism for the initiation of continental rifting e.
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Other constraints were the preservation of basement slivers around the peridotite body, a narrow thermal aureole around it and slightly asymmetrical, concentric zoning with a fluid-rich medial zone. Implications for carbonatite genesis.
Olivine xenocrysts in kimberlites, for example, have been attributed to olivine crystallization and melt—rock interaction Arndt et al.