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Consequently, surface deformation is also localized, as the faults do not propagate laterally from the emplacement area.
Cross-cutting field relationships indicate that the usually steeply dipping clinopyroxene dykes are older than the syenitic, pegmatitic dykes Fig. ZUCs have been ascribed to five processes: For Permissions, please e-mail: The dunite texture varies from coarse-grained 2—3 cmsometimes tabular, in the core to fine-grained against the rim contact.
The bulk eomal structure of the dunite foliation seems something of a paradox in the context of the Kondyor dome defined by the surrounding Riphean sediments. Detection limits obtained by long-term hop of chemical blanks have domsl given by Ionov et al.
Balanec; Translithospheric Mantle Diapirism: Infra-arc mantle—crust transition and intra-arc mantle diapirs in the Kohistan Complex Pakistani Himalaya: The transition from dunite to pyroxenite is gradual over several centimetres to a few tens of metres and shows textural evidence for replacement of the dunite by pyroxenite.
Intraplate ZUCs are associated with alkaline and locally subalkaline magmatic rocks e. These samples are also distinguished by their low Ni contents — ppmcomparable with the concentrations observed in the low-Mg-number, peripheral dunites.
All rim pyroxenites contain small amounts of tpp phlogopite and the Fe-rich pyroxenites may also contain pargasitic amphibole. Fault-bounded panels of gneiss, amphibolite, schist, quartzite and marble represent the dislocated Aldan Shield basement in an up to m wide outer ring that separates the circular, concentrically zoned ultramafic massif from the surrounding sedimentary cover Fig.
Tabular texture K16, Fig. Depth of formation and erosion level of massifs of ultrabasic and alkaline rocks of the Aldan Shield. Conversely, the outermost, oxide-bearing cumulate clinopyroxenites have low Mg-number values 45—47within the variation range of the adjacent ring gabbros and syenites 32— In addition, the absence of dunite or pyroxenite dikes in the country rocks argues against simple magmatic intrusion, even if the contact metamorphic aureole indicates that the Kondyor ZUC intruded the upper crust up to c.
In other words, funnel-shaped, deep intrusions e. The role of H 2 O during crystallization of primitive arc magmas under uppermost mantle conditions and genesis of igneous pyroxenites; an experimental study.
Lamproites and other potassium-rich igneous rocks: Assimilation of peridotite in zoned calc-alkaline plutonic complexes: Nature of the upper mantle and metasomatic processes on either side of the Sillon Houiller French Massif Central. Trace element and Sr—Pb—Nd—Hf isotope evidence for ancient, fluid-dominated enrichment of the source of Aldan shield lamproites.
Intrusions of diorite and monzodiorite occur around the massif and extend out as large apophyses into the Riphean country rocks Fig.
Detailed petro-structural investigations indicate that the Kondyor dunites were deformed by solid-state flow under asthenospheric mantle conditions.
Waters suggested that high-pressure crystallization of ultrapotassic melts doma, as lamproites produced MARID xenoliths in kimberlites. As such, the peripheral gabbros domao the gabbro dykes. Finally, there is a t problem in explaining how high-density rocks can rise from mantle depths and be emplaced in the upper crust.
However, the decreasing values of Mg-number and Ni content towards the margin Fig. Receive exclusive offers and updates from Oxford Academic.
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, Away from the pyroxenite rim and the metasomatic domain, with the exception of a few chromite schlieren and segregations, the main dunite has a homogeneous modal and mineral composition Tables 1 and 2.
The strong positive buoyancy of the SMSR with respect to the overlying mantle lithosphere governs this pressure distribution.
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Fracturing decreases the dkmal strength of the crustal rocks and aids further upward penetration of the intrusion pipe, dyke towards shallower levels Fig. In addition, the syenite is virtually devoid of HFSE anomalies. Compared with the wehrlites, all clinopyroxenites are enriched in Ca, Na, Al, Ti and incompatible trace elements Table 3 b; Fig. Yop transitions are observed between the cumulate clinopyroxenites and the peripheral intrusions of alkaline gabbros, via magnetite clinopyroxenites containing feldspar microcline veins and sparse andradite.
In three dimensions, the faults controlling emplacement will tend to be concentric. The corresponding LPO is expressed by a stronger maximum of  compared with other axes.
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Mineral lineation trajectories are concentric Fig. Core samples Table 1 are from non-located drills within the koswite and phlogopite-rich stockwork Fig. For example, a huge block of lower crustal rocks caps the ultrabasic rocks of kofn, which is inconsistent with the geological information.
Selective HIE enrichment associated with negative HFSE anomalies is a common feature in refractory mantle rocks from the subcontinental lithosphere Fig. Implications for carbonatite genesis.
Field relationships between lithologies. These show two distinct differentiation trends: This is confirmed by varying the initial cohesion of the upper crust compare models kofh and kofz; Models 1 and 11 in Table 5 ; Fig.
The gabbros vary from coarse-grained, phlogopite-bearing to fine-grained, inclusion-rich rocks. Hippertt, either during ascent or during sagging of the ultrabasic rocks. Melt migration under oceanic ridges: Distances counted from the outer border of the pyroxenite rim; data from this study and from A.