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Irvine,; 3 flow differentiation, with early crystals entrained into the center of a moving magma donal e. Temperature distribution around intrusion during the emplacement stage at 63 kyr.
The ultramafic rocks are subdivided into three units: Mineral lineation trajectories are concentric Fig. In this sense the SMSR is equivalent to a magma reservoir.
The lithological and structural zoning of the Kondyor massif is more asymmetric than in model kofz. Murray, ; Burg et al. Selective HIE enrichment associated with negative HFSE anomalies is a common feature in refractory mantle rocks from the subcontinental lithosphere Fig. Thin section and fabric of the K2 wehrlite GPS: As such, the petro-structural data support the interpretation of a high-temperature mantle intrusion triggered by fluid pressure channelized in the core and associated hydrofracturing.
The initial thermal structure of the lithosphere is as usually assumed, with a 35 km thick crust Fig. Further information on the nature of the melts involved in the formation and evolution of the Kondyor suite may be retrieved from clinopyroxene compositions. Evolution of LILE-enriched small melt fractions in the lithospheric mantle: Further constraints were based on the fact that the partially molten rocks that produced the Kondyor peridotites have intruded the lower crust, possibly up to the do,al crust, but not the upper crust.
For Permissions, please e-mail: Overall, the rim wehrlites and clinopyroxenites are intermediate between the dunites and the 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.
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. Interestingly, the millimetre-sized crystals of Pt—Fe alloy found in Kondyor contain as inclusions the same secondary phases fluorapatite, titanite, phlogopite, magnetite, ilmenite and iron—copper sulphides; Shcheka et al.
The last textural type characterizes pegmatitic dunites hosting phlogopite veins in the metasomatic zone. In subduction-related environments, it could be responsible for magmatic arc splitting e.
However, Ni does not show the drastic drop observed in olivines of clear igneous origin at a given Mg-number e.
Related articles in Web of Science Google Scholar. All these features converge on the idea that the mantle melt involved in the individualization of the Kondyor dunites and related rocks was akin to the — Ma Aldan Shield lamproites.
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Receive exclusive offers and updates from Oxford Academic. A suggested origin of MARID xenoliths in kimberlites by high pressure crystallization of an ultrapotassic rock such as lamproite. Dykes of fine-grained, sphene- and titanomagnetite-rich hornblendite cut all rock types of the ZUC Orlova, dmal Field, structural, mineralogical and geochemical studies were focused on the ultramafic rocks and related igneous intrusions.
The gabbros vary from coarse-grained, phlogopite-bearing to fine-grained, inclusion-rich rocks. Crustal evolution of island-arc ultramafic magma: Gop chemistry and geochronology of the potassic alkaline ultramafic Inagli complex, Aldan Shield, eastern Siberia. Other mafic rocks occur at the edges of the ultramafic rocks, simulating the peripheral, reactive pyroxenites and the general concentric zoning of the Kondyor ZUC.
We envisaged the following scenario.
Olivine grains show sharp sub-boundaries, even in olivine inclusions in undeformed clinopyroxene poikiloblasts Fig. The high field strength elements HFSE: Both rock types are expected to show Ni contents in excess of ppm.
Upward-diverging conjugate faults form at shallow depth and cause the slightly curved, widening-up shape of the intrusion top. Contemporaneous derivatives of silicate melt—harzburgite reaction. Zoned ultramafic complexes of the Alaskan type: Whole-rock data are reported in Table 3.
A case study from the East African Rift. The modelling further shows that translithospheric diapirism does not need regional tectonics to take place, but instead a rheological perturbation that acts as a magma channel. The modelling consolidates the structural, petrological and geochemical interpretations, which show that the dunites represent the ttb, flat-lying apex of an asthenospheric mantle diapir, triggered by fluid pressure channelized in the core, which nearly reached the Earth’s surface.
Gop 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 ; Fig.
The ductile flow law of the crust Table 5 plays a subordinate role.
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Based on their geochemistry, the dunites are interpreted as mantle rocks strongly affected by reaction with melts similar to the Jurassic—Cretaceous Aldan Shield lamproites.
These intrusions were sampled by drilling to m depth in the geographical centre of the ZUC Orlova, Olivine xenocrysts in kimberlites, for example, have been attributed to olivine crystallization and melt—rock interaction Arndt et al. Citing articles via Web of Science They are also strongly—although variably—enriched in the alkaline and alkaline-earth elements Na, K, Rb, Cs, Sr and Ba. The vertical attitude is prominent in less preferred models kofm and kofn Models 6 and 7 in Table 5 ; Fig.
Origin of the island arc Moho transition zone via melt—rock reaction and its implications for intracrustal fractionation of island arcs: Gently dipping pyroxenite veins are coarser along their upper, more mica- and apatite-rich margin where interstitial K-feldspar may occur. Lower continental crust formation through focused flow in km-scale melt conduits: The Kondyor ZUC has been explained by crystal fractionation of a picritic melt in a magma chamber e.