scholarly journals Gardar mantle xenoliths: Igdlutalik, South Greenland

1991 ◽  
Vol 150 ◽  
pp. 37-43
Author(s):  
B.G.J Upton
Keyword(s):  
Host Rock ◽  
Mantle Xenoliths ◽  
Geochemical Evidence ◽  
Ultramafic Lamprophyre ◽  
Ultramafic Xenoliths ◽  
Mineral Assemblages

A dyke of presumed Gardar age on Igdlutalik island near Narsaq contains an abundance of ultramafic xenoliths. Both host rock and xenoliths have been metamorphosed and the original mineral assemblages largely replaced by tremolite, chlorite and magnetite. Textural and geochemical evidence suggests: (a) that the host rock was a part of the ultramafic lamprophyre suite known throughout the Tugtut6q-Ilimaussaq-nunataq lineament, and (b) that the xenoliths were mantle-derived peridotites (possibly garnetiferous), together with some glimmerites that may be analogues of MARID-suite xenoliths known from kimberlite occurrences.

Mantle xenoliths from Tertiary lavas and dykes on Ubekendt Ejland, West Greenland

1998 ◽  
pp. 152-154
Author(s):  
Stefan Bernstein ◽  
C. Kent Brooks
Keyword(s):  
Field Work ◽  
Mantle Xenoliths ◽  
Alkaline Basalt ◽  
Basalt Flow ◽  
Volcanic Province ◽  
East Greenland ◽  
Original Series ◽  
West Greenland ◽  
Ultramafic Xenoliths ◽  
Extensive Collection

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Bernstein, S., & Brooks, C. K. (1998). Mantle xenoliths from Tertiary lavas and dykes on Ubekendt Ejland, West Greenland. Geology of Greenland Survey Bulletin, 180, 152-154. https://doi.org/10.34194/ggub.v180.5099 _______________ Mantle xenoliths were found in Tertiary alkaline (basanitic) lavas on Ubekendt Ejland in West Greenland in the mid 1970s by J.G. Larsen. Microprobe analyses of olivine, pyroxene and spinel in two mantle xenoliths, suggested that the xenoliths on Ubekendt Ejland are highly depleted and have high modal olivine contents, and low modal orthopyroxene and clinopyroxene (Larsen 1982). In this respect the mantle xenoliths from Ubekendt Ejland are very similar to the spinel harzburgites from Wiedemann Fjord, in the Tertiary volcanic province of East Greenland (Brooks & Rucklidge 1973; Bernstein et al. 1998). Larsen (1981) also reported dykes containing mantle nodules and a varied suite of cumulates and megacrysts, one of which has subsequently been dated to 34.1 ± 0.2 Ma (Storey et al. 1998) The basalt flow that carries the xenoliths is from what is defined as the Erqua Formation which occurs at the top of the lava succession in western Ubekendt Ejland (Fig. 1; Drever & Game 1948; Larsen 1977a, b). The basalts have not been dated, but are younger than 52.5 Ma, which is the date obtained for the underlying formation (Storey et al. 1998). During July 1997, we spent three weeks collecting xenoliths and prospecting for xenolith-bearing dykes in the Uummannaq district of central West Greenland. The field work resulted in an extensive collection of xenoliths from an alkaline basalt flow described by Larsen (1977a, b), as well as the discovery of a dyke carrying a large number of ultramafic xenoliths of various origins. 

Petrology of ultramafic xenoliths from Rayfield River, south-central British Columbia

1987 ◽  
Vol 24 (8) ◽  
pp. 1679-1687 ◽  
Author(s):  
Dante Canil ◽  
Mark Brearley ◽  
Christopher M. Scarfe
Keyword(s):  
British Columbia ◽  
Phase Equilibrium ◽  
Partial Melting ◽  
Upper Mantle ◽  
Mantle Xenoliths ◽  
Spinel Lherzolite ◽  
Equilibrium Constraints ◽  
Host Magma ◽  
South Central ◽  
Ultramafic Xenoliths

One hundred mantle xenoliths were collected from a hawaiite flow of Miocene–Pliocene age near Rayfield River, south-central British Columbia. The massive host hawaiite contains subrounded xenoliths that range in size from 1 to 10 cm and show protogranular textures. Both Cr-diopside-bearing and Al-augite-bearing xenoliths are represented. The Cr-diopside-bearing xenolith suite consists of spinel lherzolite (64%), dunite (12%), websterite (12%), harzburgite (9%), and olivine websterite (3%). Banding and veining on a centimetre scale are present in four xenoliths. Partial melting at the grain boundaries of clinopyroxene is common and may be due to natural partial melting in the upper mantle, heating by the host magma during transport, or decompression during ascent.Microprobe analyses of the constituent minerals show that most of the xenoliths are well equilibrated. Olivine is Fo89 to Fo92, orthopyroxene is En90, and Cr diopside is Wo47En48Fs5. More Fe-rich pyroxene compositions are present in some of the websterite xenoliths. The Mg/(Mg + Fe2+) and Cr/(Cr + Al + Fe3+) ratios in spinel are uniform in individual xenoliths, but they vary from xenolith to xenolith. Equilibration temperatures for the xenoliths are 860–980 °C using the Wells geothermometer. The depth of equilibration estimated for the xenoliths using geophysical and phase equilibrium constraints is 30–40 km.

Nature and evolution of the northern Victoria Land lithospheric mantle (Antarctica) as revealed by ultramafic xenoliths

2021 ◽  
pp. M56-2020-11
Author(s):  
Massimo Coltorti ◽  
Costanza Bonadiman ◽  
Federico Casetta ◽  
Barbara Faccini ◽  
Pier Paolo Giacomoni ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Evolutionary History ◽  
Major Elements ◽  
Mantle Xenoliths ◽  
Victoria Land ◽  
Ultramafic Xenoliths ◽  
Large Sector ◽  
Subcontinental Lithosphere ◽  
Comparative Manner

AbstractA review of northern Victoria Land ultramafic xenoliths, collected and studied over more than 30 years, was carried out. More than 200 samples were gathered and characterized in a coherent and comparative manner, both for mantle-derived and cumulate xenoliths. Almost 2000 analyses of major elements and more than 300 analyses of trace elements of in situ and separated olivine, pyroxenes, amphibole, spinel and glass were taken into consideration. Particular attention was devoted to mantle lithologies in order to emphasize the composition and the evolution of this portion of the subcontinental lithosphere. The three main localities in northern Victoria Land where mantle xenoliths were found (i.e. Mount Melbourne (Baker Rocks), Greene Point and Handler Ridge), over a >200 km distance, were described and compared with ultramafic xenoliths in three other localities (Harrow Peaks, Browning Pass and Mount Overlord) that are mainly cumulate in nature. Altogether, these data enabled us to reconstruct a long evolutionary history, from old depletion to most recent refertilization and metasomatic events, for this large sector of the northern Victoria Land subcontinental lithospheric mantle.

scholarly journals Mathiasite-loveringite and priderite in mantle xenoliths from the Alto Paranaíba Igneous Province, Brazil: genesis and constraints on mantle metasomatism

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Vidyã Almeida ◽  
Valdecir Janasi ◽  
Darcy Svisero ◽  
Felix Nannini
Keyword(s):  
Mantle Metasomatism ◽  
Mantle Xenoliths ◽  
Southeastern Brazil ◽  
Chemical Zoning ◽  
Ti Oxides ◽  
Peridotite Xenoliths ◽  
Mantle Enrichment ◽  
Alkaline Intrusion ◽  
Igneous Province ◽  
Mineral Assemblages

AbstractAlkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55–60 wt.% TiO2; 5.2–6.7 wt.% ZrO2) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr2O3) and subordinate ilmenite (12–13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0.05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4–9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events.

scholarly journals Ultramafic xenoliths from the Veneto Volcanic Province (Italy): Petrological and geochemical evidence for multiple metasomatism of the SE Alps mantle lithosphere

2006 ◽  
Vol 40 (4) ◽  
pp. 377-404 ◽  
Author(s):  
DANIELA GASPERINI ◽  
DELPHINE BOSCH ◽  
ROBERTO BRAGA ◽  
MIRELLA BONDI ◽  
PATRIZIA MACERA ◽  
...  
Keyword(s):  
Mantle Lithosphere ◽  
Volcanic Province ◽  
Geochemical Evidence ◽  
Ultramafic Xenoliths

scholarly journals Archetypal kimberlite from the Maniitsoq region, southern West Greenland and analogy to South Africa

2006 ◽  
Vol 10 ◽  
pp. 45-48 ◽  
Author(s):  
Troels F.D. Nielsen ◽  
Martin Jebens ◽  
Sven M. Jensen ◽  
Karsten Secher
Keyword(s):  
South Africa ◽  
South African ◽  
The West ◽  
West Greenland ◽  
Ultramafic Lamprophyre ◽  
Mineral Assemblages ◽  
Bona Fide ◽  
Indicator Mineral

Ultramafic dyke rocks with kimberlitic megacrysts and mantle nodules have been known for decades from the northern part of the Archaean block and adjacent Proterozoic terranes in southern West Greenland (Fig. 1; Escher & Watterson 1973; Goff 1973; Scott 1981; Larsen & Rex 1992; Mitchell et al. 1999). Some of the dykes have proved to be diamondiferous (see Jensen et al. 2004a, b, for exploration results, diamond contents, and references). The c. 600 Ma old dykes werecalled ‘kimberlitic’ by Larsen & Rex (1992), but Mitchell et al. (1999) concluded that they were best referred to a ‘carbonatiteultramafic lamprophyre’ suite (aillikites or melnoites). Mitchell et al. (1999) further suggested that the West Greenland province represents “one of the few bona fide examples of ultramafic lamprophyre which contain diamonds”. Reports on indicator mineral assemblages (Jensen et al. 2004b) and diamond contents (e.g. Hudson Resources Inc. 2005) have re-opened the discussion on the classification of the dykes. The results of an investigation of the Majuagaa dyke (Nielsen & Jensen 2005) are summarised below, together with the preliminary results of a regional investigation of the groundmass minerals of the dykes. It is concluded that dykes in the Maniitsoq region are similar to archetypal, South African, on-craton, Type 1 kimberlites, and that all regions of the West Greenland province of ultramafic magmatism are favourable for diamond exploration.

Petrography and mineral chemistry of mantle xenoliths in a carbonate-rich melilititic tuff from Mt. Vulture volcano, southern Italy

2000 ◽  
Vol 64 (4) ◽  
pp. 593-613 ◽  
Author(s):  
A. P. Jones ◽  
T. Kostoula ◽  
F. Stoppa ◽  
A. R. Woolley
Keyword(s):  
High Pressure ◽  
Heat Flow ◽  
Southern Italy ◽  
Mineral Chemistry ◽  
Continental Rift ◽  
Mantle Xenoliths ◽  
Chrome Spinel ◽  
Partial Melt ◽  
Host Magma ◽  
Mineral Assemblages

AbstractWe present petrographic and mineralogical data for 21 mantle xenoliths (12 lherzolites, 8 wehrlites and 1 composite) selected from a suite of more than 70 samples collected from the Monticchio Formation, Mt. Vulture volcano, southern Italy. The xenoliths are rounded, coarse- to porphyroclastic-textured, and very fresh, with the following equilibrated mineral assemblages; olivine (Fo90–92), orthopyroxene (∼En89, Wo2.0), clinopyroxene (Mg90–92, 3–6% Al2O3, 1–1.5% Cr2O3), and chrome-spinel (14–20% MgO, ∼30–40% Cr2O3). Many xenoliths contain partial melt glasses and accessory sulphide (pentlandite) Some contain primary mica (phlogopite with ∼4% FeO, 1.8% Cr2O3, 1.4–2.8% TiO2) with slightly zoned rims (Fe-, Ti-, Al-enriched). One contains relics of garnet (pyrope; Mg84). Secondary veins in several xenoliths contain carbonate with significant Sr levels (∼0.5–1.0% SrO), occasional apatite and scarce melanite, all typical of carbonatites and presumably related to the host magma (melilitite/carbonatite). Although amphibole is a common megacryst in the same volcanic units, no primary amphibole was found in the xenoliths themselves. Calculated pressures and temperatures using a range of geothermometers/barometers give values of 14–22 kbar and 1050–1150°C. In particular, the En-Sp and Di-Sp thermo/barometers (Mercier, 1980) show a good positive correlation between P and T. The Monticchio xenoliths lie on the high-T side of an ‘oceanic’ geotherm. The xenolith geotherm is hotter than general heat flow values in this region at the current day (50 mWm−2) but it compares well with the high-pressure end of a typical alkaline continental rift.

Crust–Mantle Xenoliths from the Kharchinsky Volcano (Central Kamchatka Depression): Mineralogy and Petrogenesis

2021 ◽  
Vol 62 (03) ◽  
pp. 339-356
Author(s):  
V.S. Sekisova ◽  
S.Z. Smirnov ◽  
D.V. Kuzmin ◽  
A.Ya. Shevko ◽  
M.P. Gora
Keyword(s):  
Plutonic Rock ◽  
Mantle Xenoliths ◽  
Stability Field ◽  
Mineral Assemblages ◽  
Vein Mineral ◽  
Central Kamchatka Depression ◽  
Primary Minerals

Abstract —We present results of a study of plutonic-rock xenoliths from the Kharchinsky Volcano (Central Kamchatka depression). The studied xenolith collection comprises nine samples of peridotites and clinopyroxenites. The peridotites are identified as wehrlites, dunites, and harzburgites composed of olivine, clino- and orthopyroxenes, amphibole, and chromite in varying amounts. The clinopyroxenites consist mostly of clinopyroxene and often contain subordinate olivine, amphibole, hercynite, and magnetite. The xenoliths have interstitial segregations and veins composed of chlorite, plagioclase, K-feldspar, orthopyroxene, barite, fluorapatite, ilmenite, and, more seldom, anhydrite, phlogopite, and some other minerals. The study has revealed that veinlet minerals sometimes replace primary minerals and form pseudomorphs, thus indicating the metasomatic origin of interstitial and vein mineral assemblages. The thermobarometric calculations for minerals have shown that peridotites formed at ~1140 °C and ≤10 kbar in the intermediate chambers at the depths from the spinel stability field to the Moho. Interstitial metasomatic alterations of rocks took place at ~400–850 °C.

IODP Hole 1473A (Atlantis Bank, SWIR) - Formation of felsic veins in gabbros: reactions at the contact between felsic melt and host rock

2021 ◽  
Author(s):  
Artur Engelhardt ◽  
Jürgen Koepke ◽  
François Holtz
Keyword(s):  
Host Rock ◽  
Liquid Immiscibility ◽  
Southwest Indian Ridge ◽  
Equilibrium Study ◽  
Eutectic Crystallization ◽  
Mineral Assemblages ◽  
Atlantis Bank ◽  
Slow Spreading ◽  
Ti Content ◽  
Calculated Equilibrium

&lt;p&gt;Hole U1473 (32&amp;#176; 42.3622&amp;#8217; S; 57&amp;#176; 16.6880&amp;#8217; E), located on the summit of Atlantis Bank at the ultra-slow spreading Southwest Indian Ridge was drilled to 789.7 m below seafloor (mbsf) during IODP Expedition 360. It consists of massive gabbros cut by nearly 400 felsic veins, which are evolved, SiO&lt;sub&gt;2&lt;/sub&gt;- enriched lithologies comprising ~1.5 vol% of the drill core. They vary in composition from diorite to trondhjemite. For their formation, 3 endmember models are discussed: (1) fractional crystallization; (2) hydrous anatexis of mafic rocks; (3) liquid immiscibility in an evolved MORB system.&lt;/p&gt;&lt;p&gt;Mineral assemblages in the felsic veins include mainly plagioclase, amphibole, Fe-Ti oxides &amp;#177; quartz and minor zircon, apatite, &amp;#177; titanite, &amp;#177; biotite, &amp;#177; K-feldspar.&lt;/p&gt;&lt;p&gt;Vein minerals often show strong zoning, which is especially expressed in amphiboles clearly visible by their variation in color ranging from brown to green corresponding to compositions from pargasite via pargasitic amphiboles, magnesiohornblendes to tremolite/actinolite. Moreover, zoning patterns can be observed in plagioclases from the veins, in which their An contents vary from An&lt;sub&gt;34&lt;/sub&gt; down to An&lt;sub&gt;5&lt;/sub&gt;. This is distinctly lower than in the plagioclases of the host gabbros, which are virtually unzoned.&lt;/p&gt;&lt;p&gt;Clinopyroxenes at the contact between felsic vein and host gabbro show reactions either towards orthopyroxene or amphibole. TiO&lt;sub&gt;2&lt;/sub&gt; in brown pargasites in the host rock at the contact is enriched (up to ~4.6 wt%), whereas counterparts of the same crystals in the felsic veins are distinctly lower in TiO&lt;sub&gt;2&lt;/sub&gt; varying from ~2.5&amp;#160;wt% down to 0.1 wt% TiO&lt;sub&gt;2&lt;/sub&gt;, associated with variation in color from brown to green. Calculated equilibrium temperatures based on Ti-content in amphibole (Ernst&amp;#160;&amp; Liu, 1998), consequently lead to higher formation temperatures for amphiboles in the host gabbro (up to ~1000&amp;#160;&amp;#176;C) compared to their counterparts in the veins, ranging from ~890 &amp;#176;C to ~500 &amp;#176;C.&lt;/p&gt;&lt;p&gt;Amphiboles contain ~0.2 wt% F and distinctively lower contents in Cl (with one exception found). Most amphiboles at the contact show a core-rim evolution trend with decreasing F and increasing Cl content, implying a magmatic formation with increasing influence of processes involving a hydrothermal fluid. Only one out of twenty-two investigated samples shows a trend vice versa.&lt;/p&gt;&lt;p&gt;The record of eutectic crystallization expressed by granophyric structures of quartz and plagioclase indicates that the felsic veins crystallized from a melt.&lt;/p&gt;&lt;p&gt;&lt;em&gt;Ernst, W. G., &amp; Liu, J. (1998). Experimental phase-equilibrium study of Al-and Ti-contents of calcic amphibole in MORB&amp;#8212;A semiquantitative thermobarometer.&amp;#160;American mineralogist,&amp;#160;83(9-10), 952-969.&lt;/em&gt;&lt;/p&gt;

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