Kagalabar Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation. 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. The vertical attitude is prominent in less preferred models kofm and kofn Models 6 and 7 in Table 5 ; Fig. What olivine, the neglected mineral, tells us about kimberlite petrogenesis. Oxford University Press is a department of the University of Oxford. Contemporaneous derivatives of silicate melt—harzburgite reaction.

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Yokazahn Numerical modelling was therefore carried out to explore the mechanical and thermal conditions under which translithospheric diapirism is plausible. This variation is coupled with a textural change from fine-grained textures reminiscent of mantle tectonites cpx-bearing dunites and wehrlites with dimal flames to coarse-grained cumulate textures clinopyroxenitesthrough poikiloblastic, replacive textures wehrlites. Nature of the upper mantle and metasomatic processes on either side of the Sillon Houiller French Massif Central.

Comparison with other refractory mantle peridotite xenoliths from the Massif Central, France Alard et al. The distinctive feature of Kondyor is its nearly perfect circular columnar shape, which may ttop reflect the absence of far-field stresses in the crust.

Oxford University Press is a department of the University of Oxford. The Kondyor ZUC is composed of a chromite-bearing dunite core, c. 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.

The offset from the dunite array is subtle for wehrlites but more significant for pyroxenites and related gabbros or syenites see below that define a positive correlation markedly distinct from that shown by the dunites.

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. The Mg-number is strongly buffered by olivine in peridotite—melt systems Bodinier et al.

Regularities of the location of ore mineralizaion at the Kondyor Massif. The 2D models over-emphasize the size of the deformed area, compared with what it would be in three dimensions. 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.

This clearly indicates that the Mg-number—Ni covariation in ttop is governed by melt—rock interaction rather than by fractional crystallization. The LPO could not be measured because of the large grain size 5—10 mm. Origin of the Tulameen ultramafic—gabbro complex, southern British Columbia.

The vertical attitude is prominent in less preferred models kofm and kofn Models 6 and 7 in Table 5 ; Fig. It is also accompanied by a gradual decrease of the Fo content of olivine and of the Mg-number of clinopyroxene Table 2. Basic gabbro igneous rocks are concentrated in a medullar channel, at the core of the column, in a position equivalent to the koswite-rich metasomatic zone of Kondyor.

Lallemant, and subsequent lithospheric break-up above mantle plumes. The dunite texture varies from coarse-grained 2—3 cmsometimes tabular, in the core to fine-grained against the rim contact. Instabilities xomal by the accumulation of volatile-rich melt forced the dunite into the crust as a translithospheric diapir. The dunite core was first individualized in a porous 56 reservoir at the base of the lithospheric mantle, possibly eroded by a mantle plume.

However, they are distinguished by a much finer-grained, fluidal texture and the lack of patent metasomatism in their wall-rocks, suggesting that they represent hypovolcanic dykes intruded after substantial cooling of the ultramafic host. This duality indicates that two contrasted liquids—nepheline-syenitic and carbonatitic—were generated upon differentiation of the primary lamproite melt.

The high field strength elements HFSE: Olivine-forming reactions associated with magma transport are, therefore, considered to be the predominant dunite-forming mechanism e. The dunites are brecciated and strongly metasomatized in the wall-rocks of the pyroxenite veins Emelynenko et al. Contemporaneous derivatives of silicate melt—harzburgite reaction.

Second, although showing strong similarities in their trace-element signature, all rim pyroxenites and wehrlites are distinguished from intrusive and vein pyroxenites by much lower abundance of incompatible trace elements Fig. V, funnel-shaped; S, sickle-shaped; I, finger-shaped; T, sill-shaped. The lower and especially the upper continental crust should be sufficiently dry and cold to have a high initial plastic strength and to focus strongly intrusion between subvertical faults.

Two important features characterize the pressure distribution: Deep-seated partial melts migrating upward tend to dissolve the pyroxene component of percolated rop and crystallize olivine, leading to the formation of olivine-rich rocks Kelemen, These samples are also distinguished by their low Ni contents — ppmcomparable with the concentrations observed in the low-Mg-number, peripheral dunites. Assimilation of peridotite in zoned calc-alkaline plutonic complexes: Interestingly, the millimetre-sized crystals of Pt—Fe alloy found in Kondyor contain as inclusions the same secondary phases fb, titanite, phlogopite, magnetite, ilmenite and iron—copper sulphides; Shcheka et domak.

The other distinct and economically valuable feature of Kondyor is the high concentration of platinum-group elements PGE in the eroded tip, and lower concentrations in the remaining metasomatic zone. Structures and petrotextures of toop ultrabasic cores of ring massifs in the Russian Far East. Acceptable shortcomings of model kofz concern the attitude of the body subvertical in Kondyor and inclined in the modelthe internal dokal distribution, the synformal final shape and the rim plutons.

Nepheline-syenite pegmatites occur in all parts of the Kondyor ZUC. Only after substantial cooling of the Kondyor body were lamproite melts focused into vein conduits where they evolved by several mechanisms including wall-rock reaction, fractional crystallization and liquids unmixing. As such, the peripheral gabbros resemble the gabbro dykes. The simultaneous evolution of these two types of melts from volatile-rich alkaline magmas is commonly ascribed to the separation of immiscible liquids e.

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Kigazshura Assimilation of peridotite in zoned calc-alkaline plutonic complexes: Time kyr is given in the figures. However, the slip system is the common []with [] close to lineation and close to foliation; the [] maximum probably results from large subgrain rotations, with [] as external rotation axis. Dykes of fine-grained, sphene- and titanomagnetite-rich hornblendite cut all rock types of the ZUC Orlova, Hippertt, either during ascent or during sagging of the ultrabasic rocks. The Artel Amur mining company provided us with open access to drill core samples from — m depth into the metasomatic domain, which allowed detailed observations of the mineralogy of the glimmerite and clinopyroxenite veins and their wall-rocks Fig. A case study doal the East African Rift.


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