The kabr El-Bonaya peridotites, Southeastern Sinai, Egypt: petrology, geochemistry, and metamorphism of Neoproterozoic arc ultramafic cumulates

2021 ◽  
Vol 321 (10) ◽  
pp. 1445-1496
Author(s):  
Ayman E. Maurice ◽  
Mokhles K. Azer ◽  
Paul D. Asimow ◽  
Fawzy F. Basta ◽  
Hassan M. Helmy ◽  
...  
Keyword(s):  
Ultramafic Cumulates

Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds

2003 ◽  
Vol 40 (6) ◽  
pp. 833-852 ◽  
Author(s):  
M Tardy ◽  
H Lapierre ◽  
D Bosch ◽  
A Cadoux ◽  
A Narros ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Island ◽  
Light Rare Earth ◽  
Isotopic Compositions ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
British Colombia ◽  
Ultramafic Cumulates ◽  
Back Arc

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

Vertical igneous layering in the Ewarara layered intrusion, central Australia

1977 ◽  
Vol 114 (5) ◽  
pp. 365-374 ◽  
Author(s):  
A. D. T. Goode
Keyword(s):  
Layered Intrusion ◽  
Multiple Injection ◽  
Crystal Mush ◽  
Flow Differentiation ◽  
Central Australia ◽  
Ultramafic Cumulates ◽  
Inhomogeneous Crystal ◽  
Feeder Zone ◽  
Igneous Layering ◽  
Layered Sequence

SummaryThe Ewarara Intrusion of central Australia contains two vertical fine-banded horizons within a sequence of sub-horizontal ultramafic cumulates. The horizons are arranged in an en échelon pattern adjacent to a steep intrusional contact, and consist of an alternation of two layer types which correspond to the two major lithologies present in the horizontal sequence. The horizons are up to 5 m thick. A number of possible origins, including folding of originally horizontal cumulates, flow differentiation and multiple injection, do not satisfactorily explain the formation of the layering. The most likely origin appears to involve differential viscous flow along the steep contact of an inhomogeneous crystal mush derived from the horizontal layered sequence. This mobilization is related to fresh injections along a feeder zone trending 060µ, the only such zone recognized in the Giles Complex.

scholarly journals An insight into the first stages of the Ferrar magmatism: ultramafic cumulates from Harrow Peaks, northern Victoria Land, Antarctica

2019 ◽  
Vol 174 (5) ◽  
Author(s):  
Beatrice Pelorosso ◽  
Costanza Bonadiman ◽  
Theodoros Ntaflos ◽  
Michel Gregoire ◽  
Silvia Gentili ◽  
...  
Keyword(s):  
Victoria Land ◽  
Ultramafic Cumulates ◽  
Insight Into

Petrogenetic insights from chromite in ultramafic cumulates of the Xiarihamu intrusion, northern Tibet Plateau, China

2020 ◽  
Vol 105 (4) ◽  
pp. 479-497 ◽  
Author(s):  
Xie-Yan Song ◽  
Kai-Yuan Wang ◽  
Stephen J. Barnes ◽  
Jun-Nian Yi ◽  
Lie-Meng Chen ◽  
...  
Keyword(s):  
Trace Elements ◽  
Major And Trace Elements ◽  
Tibet Plateau ◽  
Ultramafic Rocks ◽  
Sulfide Deposit ◽  
Northern Tibet ◽  
Mid Ocean Ridge ◽  
Ultramafic Cumulates ◽  
Positive Correlations ◽  
Ocean Ridge

Abstract Chromite is one of the earliest crystallized minerals from mafic melts and has been used as an important “petrogenetic indicator.” Its composition may be modified by interaction with intercumulate melt and adjacent minerals. Thus, chromite in mafic-ultramafic rocks contains clues to the geochemical affinity, evolution, and mantle source of its parent magmas. The Devonian Xiarihamu intrusion, located in the East Kunlun Orogenic Belt in the northern Tibet Plateau, China, hosts a very large disseminated Ni-Co sulfide deposit. This study focuses on geochemistry of the chromite enclosed in olivine of ultramafic rocks of the intrusion. Enrichments in Mg and Al in the rim of the chromite indicate only minor effects of alteration on the compositions of the chromite. The chromites enclosed in the olivines with forsterite percentage (Fo) lower than 87 are characterized by large variations in major and trace elements, such as large ranges of Cr·100/(Cr+Al) (Cr# = 15–47), Mg·100/(Mg+Fe2+) (Mg# = 41–65), and Al2O3 (= 26–53 wt%) as well as 380–3100 ppm V, 70–380 ppm Ga, and 1100–16300 ppm Zn. The chromites display positive correlations between Cr/(Cr+Al) and Ti, Mn, V, Ga, and Sc, inconsistent with fractional crystallization but indicative of an interaction between the chromites, intercumulate melts and hosting minerals. In contrast, chromites hosted in olivine with Fo > 87 in harzburgite have small variations in Cr# (ranging from 37 to 41), Mg# (48 to 51), and Al2O3 (30 to 35 wt%) as well as restricted variation in trace elements, indicating relatively weak interaction with trapped liquid and adjacent phases; these compositions are close to those of the most primitive, earliest crystallized chromites. The most primitive chromite has similarities with chromite in mid-ocean ridge basalt (MORB) in TiO2 and Al2O3 contents (0.19–0.32 and 27.9–36.3 wt%, respectively) and depletion of Sc and enrichment of Ga and Zn relative to MORB chromite. The geochemistry of the chromite indicates a partial melting of the asthenospheric mantle that was modified by melts derived from the subduction slab at garnet-stable pressures.

Geochemistry of Middle Triassic gabbros from northern Liaoning, North China: origin and tectonic implications

2008 ◽  
Vol 146 (4) ◽  
pp. 540-551 ◽  
Author(s):  
XIAOHUI ZHANG ◽  
HONGFU ZHANG ◽  
MINGGUO ZHAI ◽  
SIMON A. WILDE ◽  
LIEWEN XIE
Keyword(s):  
North China ◽  
Orogenic Belt ◽  
Shrimp Dating ◽  
The North ◽  
Magmatic Underplating ◽  
Granitic Intrusions ◽  
Ultramafic Cumulates ◽  
Geochronological Dating ◽  
T Values ◽  
Continental Interior

AbstractThe Xiaofangshen mafic stock is a hornblende gabbroic body emplaced in the Faku dome of northern Liaoning within the continental interior of the North China–Mongolian plate. Zircon U–Pb SHRIMP dating yields an emplacement age of 241 ± 6 Ma. These gabbroic rocks exhibit strong enrichment in large ion lithophile elements (e.g. Th, U) and light REE, slightly negative Eu anomalies, and pronounced depletion in high field strength elements (e.g. Nb, Ta, Zr, Ti). They show a relatively narrow range of isotopic compositions with initial 87Sr/86Sr ratios of 0.7053 to 0.7055, ϵNd(t) values of +0.40 to +0.68 and zircon ϵHf(T) values from +5.0 to +7.4. These geochemical features suggest that they might have been derived from partial melting of a subduction-related metasomatized lithospheric mantle source, which is tectonically affiliated to the Xing-Meng orogenic belt. Combined with our previous geochronological dating on the predominantly granitic intrusions from the Faku dome, it is inferred that the northern Liaoning block has a tectonic affinity with the Phanerozoic accretionary orogenic belt. This revelation further leads to the proposition that the Chifeng–Kaiyuan fault likely represents the Mesozoic lithospheric boundary between the North China craton and the Xing-Meng orogenic belt in northern Liaoning. The Xiaofangshen gabbros, together with the Triassic mafic–ultramafic cumulates and granulite xenoliths and the Triassic alkaline intrusions within the continental interior of the newly amalgamated North China–Mongolian Plate, constitute an important post-orogenic to within-plate anorogenic magmatic province, in response to the continued magmatic underplating caused by lithospheric delamination and hot asthenosphere upwelling.

scholarly journals Corona structure from arc mafic-ultramafic cumulates: The role and chemical characteristics of late-magmatic hydrous liquids

2008 ◽  
Vol 103 (5) ◽  
pp. 333-344 ◽  
Author(s):  
Hassan M. HELMY ◽  
Masako YOSHIKAWA ◽  
Tomoyuki SHIBATA ◽  
Shoji ARAI ◽  
Akihiro TAMURA
Keyword(s):  
Chemical Characteristics ◽  
Corona Structure ◽  
Ultramafic Cumulates

The Early Cretaceous San Juan Plutonic Suite, Ecuador: a magma chamber in an oceanic plateau?

2004 ◽  
Vol 41 (10) ◽  
pp. 1237-1258 ◽  
Author(s):  
Marc Mamberti ◽  
Henriette Lapierre ◽  
Delphine Bosch ◽  
Etienne Jaillard ◽  
Jean Hernandez ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Minor Component ◽  
San Juan ◽  
Type I ◽  
Oceanic Plateau ◽  
Depleted Mantle ◽  
Plutonic Rocks ◽  
Ultramafic Cumulates ◽  
A Minor ◽  
End Members

Sections through an oceanic plateau are preserved in tectonic slices in the Western Cordillera of Ecuador (South America). The San Juan section is a sequence of mafic–ultramafic cumulates. To establish that these plutonic rocks formed in an oceanic plateau setting, we have developed criteria that discriminate intrusions of oceanic plateaus from those of other tectonic settings. The mineralogy and crystallization sequence of the cumulates are similar to those of intra-plate magmas. Clinopyroxene predominates throughout, and orthopyroxene is only a minor component. Rocks of intermediate composition are absent, and hornblende is restricted to the uppermost massive gabbros within the sequence. The ultramafic cumulates are very depleted in light rare-earth elements (LREE), whereas the gabbros have flat or slightly enriched LREE patterns. The composition of the basaltic liquid in equilibrium with the peridotite, calculated using olivine compositions and REE contents of clinopyroxene, contains between 16% and 8% MgO and has a flat REE pattern. This melt is geochemically similar to other accreted oceanic plateau basalts, isotropic gabbros, and differentiated sills in western Ecuador. The Ecuadorian intrusive and extrusive rocks have a narrow range of εNdi (+8 to +5) and have a rather large range of Pb isotopic ratios. Pb isotope systematics of the San Juan plutonic rocks and mineral separates lie along a mixing line between the depleted mantle (DMM) and the enriched-plume end members. This suggests that the Ecuadorian plutonic rocks generated from the mixing of two mantle sources, a depleted mid-oceanic ridge basalt (MORB) source and an enriched one. The latter is characterized by high (207Pb/204Pb)i ratios and could reflect a contamination by recycled either lower continental crust or oceanic pelagic sediments and (or) altered oceanic crust (enriched mantle type I, EMI). These data suggest that the San Juan sequence represents the plutonic components of an Early Cretaceous oceanic plateau, which accreted in the Late Cretaceous to the Ecuadorian margin.

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