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The modelling consolidates the structural, petrological and geochemical interpretations, which show that the dunites represent the synformal, flat-lying apex of too asthenospheric mantle diapir, triggered by fluid pressure channelized in the core, which nearly reached the Earth’s surface. This method avoids memory effects caused by the introduction of concentrated Nb—Ta solutions into the instrument.
TRASMITTANZA DOMAL TOP TB 65
It is worth noting that, because of the strong dependence of orthopyroxene stability on pressure Kelemen,the reactivity of peridotite—melt systems is likely to be enhanced by translithospheric mantle upwelling, as long as primary pyroxene is not reacted out and the mantle body is not conductively cooled to subsolidus temperatures. The inclusions are of coarser-grained, darker gabbro, which suggests comagmatism.
The peripheral intrusions of tpp and monzodiorite and subordinate alkaline gabbros and granodiorites dmal xenoliths of Kondyor pyroxenites Fig. In addition, the syenite is virtually devoid of HFSE anomalies. In addition to Fe, the oxide-bearing clinopyroxenites are enriched in Ti but do not otherwise differ markedly from the other rim clinopyroxenites. The late Proterozoic Riphean sedimentary cover—which is flat lying ttop virtually unmetamorphosed elsewhere—hence defines a 10—12 km diameter dome centred on the Kondyor ZUC.
The wehrlites and clinopyroxenites rimming the Kondyor peridotites show a wide range of compositions, with a gradual and irregular variation from the inner, wehrlitic zone, transitional to cpx-bearing dunites toward the outer, oxide-bearing cumulate clinopyroxenites, which are transitional to the peripheral gabbros and syenites Table 3 t Fig.
Grain-size reduction by subgrain rotation marks larger amounts of strain and probably higher stress during flow by dislocation creep than the type 1 texture. Sign In or Create an Account. The ultramafic rocks are subdivided into three units: 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 fracture zones forming in front of the rising ultramafic body, while space was created by thinning and separation of fault blocks in the crust Fig.
A case study from dlmal East African Rift. Subgrain rotation and dynamic recrystallization of olivine, upper mantle diapirism, and extension of the Basin-and-Range Province.
These ages were substantiated by Pushkarev et al. Nepheline-syenite pegmatites occur in all parts of the Kondyor ZUC. Implications for carbonatite genesis.
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The classical relationships close to foliation and  close to lineation imply that the slip system was  Gravimetric and magnetic data emphasize the asymmetric distribution of lithologies, with strong anomalies over the magnetite-rich metasomatic domain in the WSW sector of the dunite core. Evidence of liquid immiscibility in alkaline ultrabasic dikes at Callender Bay, Ontario. Butakova, but are generally not related to large gabbro intrusions. The last textural type characterizes pegmatitic dunites hosting phlogopite veins in the metasomatic zone.
This study indicates that uprise of the Kondyor massif was intrinsically associated with solid—melt reactions involving subcontinental peridotites and lamproitic partial melts as initial reactants. Such interaction is apparent in the high-resolution numerical model of Fig. Clinopyroxenite veins are phlogopite—richterite clinopyroxenites.
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Concentric lineations could indicate vortex flow e. The Ni content of the dunites is notably lower than that of both cumulates from primary mantle melts and residual mantle rocks left after melt extraction. Part I, phase relations, the origin of calc-alkaline magma series, and the formation of discordant dunite.
This last mechanism is inferred from the duality of the most evolved mineralogical assemblages and cpx compositions in clinopyroxenite veins.
Multiple, crescent-shaped and locally strongly deformed intrusions of subalkaline gabbro are occasionally intercalated between the ultramafic body and the metamorphic country rocks. Further increase in the plastic strength of the upper crust may actually block vertical propagation of the body, which then forms sill-shaped intrusions at the boundary between the upper and lower crust kogf, Model 12 in Table 5Fig.
Model kofz fulfils all these requirements.
Thin section and fabric of the K2 wehrlite GPS: Numerical modeling of melting processes and induced diapirism in the lower crust. Same reference frame as in Fig.
An important observation is that lower Mg-number values and Ni contents distinguish the phlogopite-bearing dunites adjacent to clinopyroxenite veins and intrusions in the metasomatic domain from their distal counterparts.
The corresponding LPO is expressed by a gb maximum of  compared with other axes. As a result of thermal contraction of the dunite body upon cooling, these melts were focused in the outer part of the massif, where they migrated up to shallow, crustal levels.
Detailed petro-structural investigations indicate that the Kondyor dunites were deformed by solid-state flow under asthenospheric mantle conditions. Efimov unpublished data obtained by wet methods, Institute of Geology and Geochemistry, Ekaterinburg, Russia. The initiation of the pyroxenite rim thus records early cooling at mantle depths, most probably within the lithospheric mantle. We report new structural, microstructural, petrological, and major- and trace-element data on ultramafic rocks from the Kondyor zoned ultramafic donal in Far-East Russia.
Deep-seated partial melts migrating upward tend to dissolve the pyroxene component of percolated peridotites and crystallize olivine, leading to the formation of olivine-rich rocks Kelemen, Mineral chemistry and geochronology of the potassic alkaline ultramafic Inagli complex, Aldan Shield, eastern Siberia. Although the bulk composition of the SMSR is ultramafic, the melt composition depends on the degree of melting and thus varies between mafic and ultramafic.
Overall, the rim wehrlites and clinopyroxenites are intermediate between the dunites and tg intrusive clinopyroxenites of the metasomatic domain in most of their incompatible-element contents, except for the highly incompatible elements Rb, Ba, Th and U that overlap the dunite composition Fig.
ZUCs have been ascribed to five processes: Interpretation of SKS-wave using samples from the subcontinental lithosphere. At variance with the kimberlite model, fracturing of the country rocks in our model is caused by magma overpressure Fig. They are similar to the Aldan Shield lamproites with respect to REE, but display distinctive features for the other elements; that is, lower HIE abundances Rb—Tamore pronounced negative anomalies of Zr and Hf, and slightly negative anomalies of Sr, instead of positive anomalies.
Whole-rock major- and trace-element compositions dojal Kondyor ultramafic rocks and related intrusive rocks. Olivine-forming reactions associated with magma transport are, therefore, considered to be the predominant dunite-forming mechanism e.