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.

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.

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.

scholarly journals On the nature and origin of garnet in highly-refractory Archean lithospheric mantle: constraints from garnet exsolved in Kaapvaal craton orthopyroxenes

2017 ◽  
Vol 81 (4) ◽  
pp. 781-809 ◽  
Author(s):  
Sally A. Gibson
Keyword(s):  
Rare Earth ◽  
Lithospheric Mantle ◽  
Incompatible Trace Element ◽  
Mantle Xenoliths ◽  
Kaapvaal Craton ◽  
Depth Interval ◽  
Stability Field ◽  
Full Spectrum ◽  
Continental Lithospheric Mantle ◽  
Peridotitic Mantle

AbstractThe widespread occurrence of pyrope garnet in Archean lithospheric mantle remains one of the 'holy grails' of mantle petrology. Most garnets found in peridotitic mantle equilibrated with incompatible-trace-element enriched melts or fluids and are the products of metasomatism. Less common are macroscopic intergrowths of pyrope garnet formed by exsolution from orthopyroxene. Spectacular examples of these are preserved in both mantle xenoliths and large, isolated crystals (megacrysts) from the Kaapvaal craton of southern Africa, and provide direct evidence that some garnet inthe sub-continental lithospheric mantle formed initially by isochemical rather than metasomatic processes. The orthopyroxene hosts are enstatites and fully equilibrated with their exsolved phases (low-Cr pyrope garnet ± Cr-diopside). Significantly, P-T estimates of the postexsolution orthopyroxenes plot along an unperturbed conductive Kaapvaal craton geotherm and reveal that they were entrained from a large continuous depth interval (85 to 175 km). They therefore represent snapshots of processes operating throughout almost the entire thickness of the sub-cratonic lithosphericmantle.New rare-earth element (REE) analyses show that the exsolved garnets occupy the full spectrum recorded by garnets in mantle peridotites and also diamond inclusions. A key finding is that a few low-temperature exsolved garnets, derived from depths of ∼90 km, are more depleted in light rare-earth elements (LREEs) than previously observed in any other mantle sample. Importantly, the REE patterns of these strongly LREE-depleted garnets resemble the hypothetical composition proposed for pre-metasomatic garnets that are thought to pre-date major enrichment events in the sub-continental lithospheric mantle, including those associated with diamond formation. The recalculated compositions of pre-exsolution orthopyroxenes have higher Al2O3 and CaO contents than their post-exsolution counterparts and most probably formed as shallow residues of large amounts of adiabatic decompression melting in the spinel-stability field. It is inferred that exsolution of garnet from Kaapvaal orthopyroxenes may have been widespread, and perhaps accompanied cratonization at ∼2.9 to 2.75 Ga. Such a process would considerably increase the density and stability of the continental lithosphere.

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.

scholarly journals Archean Itabirites From Ovan, NE-Gabon: Petrography, Mineralogy And Elemental Mapping

2021 ◽  
Vol 17 (25) ◽  
pp. 380
Author(s):  
Stévy Retonda-Kondja ◽  
Simplice Marin Ndong-Ondo ◽  
Ambroise Edou-Minko ◽  
Tomohiko Sato ◽  
Benjamin Musavu-Moussavou ◽  
...  
Keyword(s):  
Sedimentary Rocks ◽  
Chemical Precipitation ◽  
Elemental Mapping ◽  
Sem Images ◽  
Secondary Minerals ◽  
Field Investigations ◽  
Mineral Assemblages ◽  
Archean Greenstone Belt ◽  
The One ◽  
Primary Minerals

The Archean greenstone belt called Bélinga Group was highlighted in NE-Gabon around 1960. It consists of many petrographic types such as itabirites (BIFs), ultrabasites, and amphibolites. Recent geophysical studies revealed the presence of BIFs and associated rocks at Ovan, which were linked to the Bélinga Group according to similar magnetic and some petrographic characteristics. Unfortunately, data on itabirites in respect with petrography, mineralogy and geochemistry are rare. This note aims at contributing to petrography, mineralogy and elemental mapping of Ovan itabirites on the one hand, and giving strong proofs that they belong to the Bélinga Group on the other. Field investigations bring samples from six sites around Ovan. Selected itabirites samples have been studied in petrography, mineralogy (XRD) and elemental mapping (SEM). Two (2) itabirites lithofacies are recognized: the well-banded and the massive itabirites. Mineral assemblages show principally quartz, magnetite, hematite and goethite. SEM images show euhedral to sub-euhedral grains of quartz and Fe-oxides of two types: the biggest (Fe1), seen as primary minerals within Fe-rich bands and the smallest (Fe2), as secondary minerals disseminated in the siliceous levels. Elemental mapping clearly reveals alternating Fe- and Si-rich bands with Fe-rich bands predominance. Finally, the itabirites around Ovan are sedimentary rocks essentially formed by chemical precipitation and belonging to the Bélinga Group.

scholarly journals Pacific Lithosphere Evolution Inferred from Aitutaki Mantle Xenoliths

2019 ◽  
Vol 60 (9) ◽  
pp. 1753-1772
Author(s):  
Eric Snortum ◽  
James M D Day ◽  
Matthew G Jackson
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Mantle Xenoliths ◽  
Stability Field ◽  
Mantle Lithosphere ◽  
Rock Interaction ◽  
Element Abundances ◽  
Enriched Mantle ◽  
Garnet Stability Field ◽  
Host Rocks

Abstract Highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re), major and trace element abundances, and 187Re–187Os systematics are reported for xenoliths and lavas from Aitutaki (Cook Islands), to investigate the composition of Pacific lithosphere. The xenolith suite comprises spinel-bearing lherzolites, dunite, and harzburgite, along with olivine websterite and pyroxenite. The xenoliths are hosted within nephelinite and alkali basalt volcanic rocks (187Os/188Os ∼0·1363 ± 13; 2SD; ΣHSE = 3–4 ppb). The volcanic host rocks are low-degree (2–5%) partial melts from the garnet stability field and an enriched mantle (EM) source. Pyroxenites have similar HSE abundances and Os isotope compositions (Al2O3 = 5·7–8·3 wt %; ΣHSE = 2–4 ppb; 187Os/187Os = 0·1263–0·1469) to the lavas. The pyroxenite and olivine websterite xenoliths directly formed from—or experienced extensive melt–rock interaction with—melts similar in composition to the volcanic rocks that host the xenoliths. Conversely, the Aitutaki lherzolites, harzburgites and dunites are similar in composition to abyssal peridotites with respect to their 187Os/188Os ratios (0·1264 ± 82), total HSE abundances (ΣHSE = 8–28 ppb) and major element abundances, forsterite contents (Fo89·9±1·2), and estimated extents of melt depletion (&lt;10 to &gt;15%). These peridotites are interpreted to sample relatively shallow Pacific mantle lithosphere that experienced limited melt–rock reaction and melting during ridge processes at ∼90 Ma. A survey of maximum time of rhenium depletion ages of Pacific mantle lithosphere from the Cook (Aitutaki ∼1·5 Ga), Austral (Tubuai’i ∼1·8 Ga), Samoan (Savai’i ∼1·5 Ga) and Hawaiian (Oa’hu ∼2 Ga) island groups shows that Mesoproterozoic to Neoproterozoic depletion ages are preserved in the xenolith suites. The variable timing and extent of mantle depletion preserved by the peridotites is, in some instances, superimposed by extensive and recent melt depletion as well as melt refertilization. Collectively, Pacific Ocean island mantle xenolith suites have similar distributions and variations of 187Os/188Os and HSE abundances to global abyssal peridotites. These observations indicate that Pacific mantle lithosphere is typical of oceanic lithosphere in general, and that this lithosphere is composed of peridotites that have experienced both recent melt depletion at ridges and prior and sometimes extensive melt depletion across several Wilson cycles spanning periods in excess of two billion years.

scholarly journals First report of ultra-high pressure metamorphism in the Paleozoic Dunhuang orogenic belt (NW China): Constrains from <i>P</i>-<i>T</i> paths of garnet clinopyroxenite and SIMS U-Pb dating of titanite

2020 ◽  
Author(s):  
Zhen M. G. Li ◽  
Hao Y. C. Wang ◽  
Qian W. L. Zhang ◽  
Meng-Yan Shi ◽  
Jun-Sheng Lu ◽  
...  
Keyword(s):  
High Pressure ◽  
Northwest China ◽  
Orogenic Belt ◽  
Stability Field ◽  
Uhp Metamorphism ◽  
High Pressure Metamorphism ◽  
Ultra High Pressure ◽  
Mineral Assemblages ◽  
Metamorphic Facies ◽  
Tectonic Exhumation

Abstract. Ultra-high pressure (UHP) metamorphism is recorded by garnet clinopyroxenite enclaves enclosed in an undeformed, unmetamorphosed granitic pluton, northeastern Paleozoic Dunhuang orogenic belt, northwest China. Three to four stages of metamorphic mineral assemblages have been found in the garnet clinopyroxenite, and clockwise metamorphic pressure-temperature (P-T) paths were retrieved, indicative of metamorphism of a possible subduction environment. Peak metamorphic P-T conditions (790~920 °C/28~41 kbar) of garnet clinopyroxenite suggest that they experienced high pressure to UHP metamorphism, and the UHP metamorphism occurred in the coesite- or diamond-stability field. The UHP metamorphic event is further confirmed by the occurrence of high-Al titanite enclosed in the garnet, along with at least three groups of aligned rutile lamellae exsolved from within the garnet. SIMS U-Pb dating of metamorphic titanite indicates that the post peak, subsequent tectonic exhumation of the UHP rocks occurred in the Devonian (~ 389~370 Ma). These data suggest that part of the Paleozoic Dunhuang orogenic belt experienced UHP metamorphism, and diverse metamorphic facies series prevailed in this orogen in the Paleozoic. It can be further inferred that most of the UHP rocks of this orogen are now buried in the depth.

Depletion, metasomatism and refertilisation in the Sub-Continental Lithospheric Mantle beneath northern Victoria Land (Antarctica): a review

2021 ◽  
Author(s):  
Massimo Coltorti ◽  
Costanza Bonadiman ◽  
Federico Casetta ◽  
Barbara Faccini ◽  
Pier Paolo Giacomoni ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Large Scale ◽  
Ross Sea ◽  
Mantle Xenoliths ◽  
Rift System ◽  
Stability Field ◽  
Alkaline Magmatism ◽  
Metasomatic Process ◽  
Victoria Land ◽  
Continental Lithospheric Mantle

&lt;p&gt;Assessing the nature and evolution of the Sub-Continental Lithospheric Mantle (SCLM) is crucial to understand the dynamics of Earth&amp;#8217;s interior and the global scale tectono-magmatic processes. The study of ultramafic xenoliths brought to the surface in specific context, such as northern Victoria Land (Antarctica), is a key to investigate how the SCLM bear witness of large-scale geodynamic episodes. Indeed, the Antarctica lithosphere was involved into three main tectono-magmatic episodes since Paleozoic, i.e. the 550-110 Ma Ross subduction, the Jurassic (~182 Ma) Ferrar magmatism and the Cenozoic alkaline magmatism responsible for the opening of the West Antarctic Rift System (WARS).&lt;/p&gt;&lt;p&gt;In this study, a review of the petrological and geochemical features of &gt;200 mantle-derived and cumulate xenoliths brought to the surface at Baker Rocks, Greene Point, Handler Ridge, Harrow Peaks, Browning Pass and Mount Overlord enabled us to reconstruct the main depletion and enrichment processes that took place in the Antarctica SCLM. Strong depletion is recorded by Greene Point lherzolites and harzburgites (18-21%), which likely began melting in the garnet facies and terminated in the spinel facies (Perinelli et al. 2006), whereas mild melt extraction in the spinel stability field was hypothesized at Baker Rocks and Handler Ridge (12-16% and 7-13% melting, respectively). The onset of the Jurassic Ferrar large magmatic event is testified by both the refertilisation in Greene Point-Baker Rocks peridotites and the appearance of cumulate orthopyroxenites/olivine-websterites at Harrow Peaks and Baker Rocks. Late enrichment process/es took place in concomitance with the Cenozoic alkaline magmatism of the WARS, resulting in both cryptic and modal metasomatism and overprinting earlier chemical modifications. This metasomatism was particularly effective at Baker Rocks, as shown by the increase of clinopyroxene abundance, its trace element enrichment and the formation of amphibole disseminated and in veins. Clinopyroxene composition in Cenozoic cumulate rocks matches the enrichment path observed in the peridotites, supporting the link between the last metasomatic process and the recent alkaline magmatism.&lt;/p&gt;&lt;p&gt;Among mantle xenoliths populations, Greene Point record the highest T-P (870-1059 &amp;#176;C; 0.8-1.6 GPa) and the least oxidized conditions (fO&lt;sub&gt;2&lt;/sub&gt; down to -2/-3 &amp;#916;FMQ). Cumulate rocks yield the highest fO&lt;sub&gt;2&lt;/sub&gt; (up to +1.5 &amp;#916;FMQ), at T varying between 900 and 1150&amp;#176;C, approximating the conditions of crystallizing melts. No discrepancies in fO&lt;sub&gt;2&lt;/sub&gt; emerged between amphibole-bearing and amphibole-free peridotites, ruling out a strict correlation between amphibole stability, H&lt;sub&gt;2&lt;/sub&gt;O activity and fO&lt;sub&gt;2&lt;/sub&gt;. Nevertheless, the alkaline metasomatic event, which led to amphibole formation, caused a remarkable increase in the H&lt;sub&gt;2&lt;/sub&gt;O content of the system. In fact, anhydrous peridotites preserve bulk H&lt;sub&gt;2&lt;/sub&gt;O contents &amp;#8804;128 ppm, while lherzolites with disseminated amphibole and hornblendites have H&lt;sub&gt;2&lt;/sub&gt;O contents as up to 354-1120 ppm and 1.42 wt%, respectively.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Perinelli, C., et al. 2006. Geochemical and O-isotope constraints on the evolution of lithospheric mantle in the Ross Sea rift area (Antarctica). Contributions to Mineralogy and Petrology, 151(3), 245-266.&lt;/p&gt;

Kimberlites from the Wawa area, Ontario

2002 ◽  
Vol 39 (12) ◽  
pp. 1819-1838 ◽  
Author(s):  
Felix V Kaminsky ◽  
Sergei M Sablukov ◽  
Ludmila I Sablukova ◽  
Vladimir S Shchukin ◽  
Dante Canil
Keyword(s):  
Rare Earth ◽  
Earth Element ◽  
Mantle Xenoliths ◽  
Igneous Rocks ◽  
Chromian Spinel ◽  
Stability Field ◽  
Light Rare Earth ◽  
Mantle Minerals ◽  
Asthenospheric Mantle ◽  
Group 1

Two newly discovered kimberlites from the Wawa area, Ontario, are Group-1 kimberlites in their petrographic, mineralogical, geochemical, and isotopic features. They contain mantle minerals and xenoliths of the Fe–Ti-association (magnesian ilmenite, iron-rich olivine, orange Ti-pyrope garnet, augite, and ferroan enstatite) and of the Cr-association (chromian spinel, forsteritic olivine, purple Cr-pyrope garnets, chromian diopside, and enstatite); minerals of Fe–Ti-association are much more abundant. Minerals of eclogitic association are absent. Both G-10 pyrope garnets and high Cr spinels typically associated with diamond are represented in the Cr-association. The average age of the kimberlites is 1097 ± 7 Ma; i.e., contemporaneous with other alkaline igneous rocks in the Wawa area. Equilibration pressures and temperatures of mantle xenoliths plot close to a 40–45 mW m–2 geotherm. On the basis of the Ni-in-garnet geothermometer, garnets from the Wawa kimberlites equilibrated at 800–1350°C, and at least in part within the diamond stability field. It is likely that kimberlitic magma was derived from light rare earth-element-enriched asthenospheric mantle.

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