scholarly journals A Plethora of Epigenetic Minerals Reveals a Multistage Metasomatic Overprint of a Mantle Orthopyroxenite from the Udachnaya Kimberlite

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 264
Author(s):  
Dmitriy I. Rezvukhin ◽  
Taisia A. Alifirova ◽  
Alexander V. Golovin ◽  
Andrey V. Korsakov
Keyword(s):  
Melt Inclusions ◽  
Kimberlite Pipe ◽  
Mantle Metasomatism ◽  
Crystal Chemical Formula ◽  
Mineral Inclusions ◽  
Reaction Zones ◽  
Geochemical Analyses ◽  
Individual Grains ◽  
Kimberlite Field ◽  
Intergranular Space

More than forty mineral species of epigenetic origin have been identified in an orthopyroxenite from the Udachnaya-East kimberlite pipe, Daldyn kimberlite field, Siberian platform. Epigenetic phases occur as: (1) Mineral inclusions in the rock-forming enstatite, (2) daughter minerals within large (up to 2 mm) crystallized melt inclusions (CMI) in the rock-forming enstatite, and (3) individual grains and intergrowths in the intergranular space of the xenolith. The studied minerals include silicates (olivine, clinopyroxene, phlogopite, tetraferriphlogopite, amphibole-supergroup minerals, serpentine-group minerals, talc), oxides (several generations of ilmenite and spinel, rutile, perovskite, rare titanates of the crichtonite, magnetoplumbite and hollandite groups), carbonates (calcite, dolomite), sulfides (pentlandite, djerfisherite, pyrrhotite), sulfate (barite), phosphates (apatite and phosphate with a suggested crystal-chemical formula Na2BaMg[PO4]2), oxyhydroxide (goethite), and hydroxyhalides (kuliginite, iowaite). The examined epigenetic minerals are interpreted to have crystallized at different time spans after the formation of the host rock. The genesis of minerals is ascribed to a series of processes metasomatically superimposed onto the orthopyroxenite, i.e., deep-seated mantle metasomatism, infiltration of a kimberlite-related melt and late post-emplacement hydrothermal alterations. The reaction of orthopyroxene with the kimberlite-related melt has led to orthopyroxene dissolution and formation of the CMI, the latter being surrounded by complex reaction zones and containing zoned olivine grains with extremely high-Mg# (up to 99) cores. This report highlights the utility of minerals present in minor volume proportions in deciphering the evolution and modification of mantle fragments sampled by kimberlitic and other deep-sourced magmas. The obtained results further imply that the whole-rock geochemical analyses of mantle-derived samples should be treated with care due to possible drastic contaminations from “hiding” minor phases of epigenetic origin.

Mineral assemblage within secondary crystallized melt inclusions in olivine of mantle xenoliths from the Bultfontein kimberlite pipe (Kaapvaal craton, South Africa)

2021 ◽  
Author(s):  
Alexey Tarasov ◽  
Igor Sharygin ◽  
Alexander Golovin ◽  
Anna Dymshits ◽  
Dmitriy Rezvukhin
Keyword(s):  
Melt Inclusions ◽  
Basic Research ◽  
Kimberlite Pipe ◽  
Mantle Xenoliths ◽  
Mantle Minerals ◽  
Source Regions ◽  
Basic Research Grant ◽  
Carbonate Composition ◽  
First Time ◽  
Ca Carbonate

<p>For the first time, snapshots of crystallized melts in olivine of sheared garnet peridotite xenoliths from the Bultfontein kimberlite pipe have been studied. This type of xenoliths represents the deepest mantle rocks derived from the base of lithosphere (at depths from 110 to 230 km for various ancient cratons). According to different models, such type of inclusions (secondary) in mantle minerals can be interpreted as relics of the most primitive (i.e., close-to-primary) kimberlite melt that infiltrated into sheared garnet peridotites. In general, these secondary inclusions are directly related to kimberlite magmatism that finally formed the Bultfontein diamond deposits. The primary/primitive composition of kimberlite melt is poorly constrained because kimberlites are ubiquitously contaminated by xenogenic material and altered by syn/post-emplacement hydrothermal processes. Thus, the study of these inclusions helps to significantly advance in solving numerous problems related to the kimberlite petrogenesis.</p><p>The unexposed melt inclusions were studied by using a confocal Raman spectroscopy. In total, fifteen daughter minerals within the inclusions were identified by this method. Several more phases give distinct Raman spectra, but their determination is difficult due to the lack of similar spectra in the databases. Various carbonates and carbonates with additional anions, alkali sulphates, phosphates and silicates were determined among daughter minerals in the melt inclusions: calcite CaCO<sub>3</sub>, magnesite MgCO<sub>3</sub>, dolomite CaMg(CO<sub>3</sub>)<sub>2</sub>, eitelite Na<sub>2</sub>Mg(CO<sub>3</sub>)<sub>2</sub>, nyerereite (Na,K)<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub>, gregoryite (Na,K,Ca)<sub>2</sub>CO<sub>3</sub>, K-Na-Ca-carbonate (K,Na)<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub>, northupite Na<sub>3</sub>Mg(CO<sub>3</sub>)<sub>2</sub>Cl, bradleyite Na<sub>3</sub>Mg(PO<sub>4</sub>)(CO<sub>3</sub>), burkeite Na<sub>6</sub>(CO<sub>3</sub>)(SO<sub>4</sub>)<sub>2</sub>, glauberite Na<sub>2</sub>Ca(SO<sub>4</sub>)<sub>2</sub>, thenardite Na<sub>2</sub>SO<sub>4</sub>, aphthitalite K<sub>3</sub>Na(SO<sub>4</sub>)<sub>2</sub>, apatite Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH,Cl,F) and tetraferriphlogopite KMg<sub>3</sub>FeSi<sub>3</sub>O<sub>10</sub>(F,Cl,OH). Note that carbonates are predominant among the daughter minerals in the melt inclusions. Moreover, there are quite a lot of alkali-rich daughter minerals within the inclusions as well. During the last decade, some research groups using different approaches proposed a model of carbonate/alkali‑carbonate composition of kimberlite melts in their source regions. This model contradicts to the generally accepted ultramafic silicate nature of parental kimberlite liquids. This study is a direct support of a new model of carbonatitic composition of kimberlite melts and also shows that alkali contents in kimberlite petrogenesis are usually underestimated.</p><p>This work was supported by the Russian Foundation for Basic Research (grant No. 20-35-70058).</p>

Composition and origin of kelyphitic rims around garnets in fresh sheared lherzolite from the Udachnaya-East kimberlite pipe, the Siberian Craton

2020 ◽  
Author(s):  
Konstantin Solovev ◽  
Igor Sharygin ◽  
Alexander Golovin
Keyword(s):  
Chemical Composition ◽  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Wave Length ◽  
Kimberlite Pipe ◽  
Mantle Metasomatism ◽  
Material Transfer ◽  
Mineral Association ◽  
Russian Science ◽  
Wide Range

<p>A zoned reaction rim (kelyphite) around garnet of xenolith of fresh sheared lherzolite from the Udachnaya-East kimberlite pipe, Russia, has been investigated. The aim of the study is a detailed characterization of bulk major and trace element compositions of the kelyphite zones, kelyphite-forming minerals and theirs relationships with each other and with rock-forming minerals of the lherzolite. <br>There are three point of possible origin of the kelyphite: 1) a solid-solid reaction (between garnets and rock-forming minerals) during transporting to the surface and modifying by a kimberlite melt (introduction of Na, K, Ca and H<sub>2</sub>O into the kelyphite) after reaction, 2) a reaction between garnets and a kimberlite melt, 3) mantle metasomatism.<br>Scanning electron microscopy coupled with energy dispersive spectrometry was used for phase determination and chemical analyses. Chemical composition of large grains (>6 μm) was also examined with wave-length-dispersive spectrometry on electron probe micro-analyzer. Raman spectroscopy was used for phase verification. Bulk trace element composition of reaction rim was studied by laser ablation‐inductively coupled plasma‐mass spectrometry.<br>Garnet forms rounded grains up to 4 mm in size, which are surrounded by the kelyphitic rim. The kelyphite has a concentric structure forming three distinct textural and chemical zones, which are extremely fine-grained aggregates of Cr- and Al-rich orthopyroxene, spinel with a wide range of Cr#, Cr and Al-rich clinopyroxene, amphibole, phlogopite, sodalite and olivine. Veinlets, which traverse the reaction rim and the garnet, are composed of the kelyphite-like mineral aggregate.<br>The kelyphite formation took place after the lherzolite was entrapped by the kimberlite magma during ascent and emplacement. Orthopyroxene, clinopyroxene and spinel were primarily formed (hereafter the first association). Known limits of pressure-temperature stability of sodalite, phlogopite and amphibole suggest their low-pressure crystallization in the kelyphite (hereafter the second association). The kimberlite melt participated in the formation of both the first mineral association and the second mineral association of the kelyphite. Olivine is believed to be result from a reaction between the kimberlite melt and the kelyphite after forming of the first association but before forming of the second association. On the basis of bulk chemical composition for each zone of the kelyphite and chemical composition of the precursor garnet, a material transfer into the kelyphite during the formation was quantitatively evaluated. Introduction of Mg, Fe, Ti and Ca in the kelyphite occured before formation of the second mineral association and introduction of Na, K, Ca, Cl, F and H<sub>2</sub>O due to formation of the second mineral association. Therefore, we can expect that the kimberlite melt was a diffusion agent during formation of the first mineral association (the garnet and rock-forming minerals are considered as reactants) and was a reactant during formation of the second mineral association.<br>This study was supported by the Russian Science Foundation (grant No 18-77-10062).</p>

The role of plicative structures as forecast criteria in the Alakit-Мarkhinsky field (western Yakutia)

2021 ◽  
pp. 6-13
Author(s):  
Dmitry Ivanov ◽  
Alexander Tolstov ◽  
Vyacheslav Ivanov
Keyword(s):  
Opposite Sign ◽  
Kimberlite Pipe ◽  
Pipe Formation ◽  
Regional Factors ◽  
Tectonic Features ◽  
Low Amplitude ◽  
Kimberlite Field

This paper describes the tectonic features of the Alakit-Markha kimberlite field, regional factors of kimberlite magmatism control in this area, structural and tectonic preconditions for kimberlite pipe prospecting. The paper highlights kimberlite pipe formation features and the role of tectonics in this process. The most promising areas are those related to low-amplitude negative structures (e.g. depressions), especially transverse low-amplitude complications of the opposite sign for the main plicative structure: for antiforms (elevations), these are saddle-shaped depressions, and antiform elevations are for synforms (depressions).

Mantle xenoliths from the Komsomolskaya-magnitnaya kimberlite pipe (Upper Muna kimberlite field, Siberian Craton) Evidences of the composition of the SCLM

2020 ◽  
Author(s):  
Igor Iakovlev ◽  
Vladimir Malkovets ◽  
Anastasiya Gibsher
Keyword(s):  
Rare Earth ◽  
Lithospheric Mantle ◽  
Kimberlite Pipe ◽  
Mantle Xenoliths ◽  
Coarse Grained ◽  
Peridotite Xenoliths ◽  
Rare Earth Element Distribution ◽  
Group 2 ◽  
Kimberlite Field ◽  
Group 1

<p>Peridotite xenoliths from kimberlites provide important information about the composition, structure and thermal regime of the lithospheric mantle of ancient cratons. In this paper, we present the results of mineralogical studies of peridotite xenoliths from kimberlites of the Upper Muna field. The Middle Paleozoic (D3-C1) high diamondiferous kimberlite pipe Komsomolskaya-Magnitnaya was chosen as the object of research.</p><p>We studied a collection of 180 peridotite xenoliths of the Komsomolskaya-Magnitnaya pipe, of which 104 belong to dunite-harzburgite paragenesis, 74 to lherzolite and 4 websterites.</p><p>The chemical composition of basic minerals from xenoliths was determined using JEOL JXA-8100 electron microprobe. Chemical analysis of xenolith garnet compositions was also performed using the Agilent 7700cs LAM-ICPMS method.</p><p>Based on a study of the collection of deep xenoliths, we found that the lithospheric mantle under the Upper Muna kimberlite field is composed mainly of garnet-bearing and chromite-bearing dunites and harzburgites, as well as coarse grained garnet lherzolites.</p><p>The olivine Mg# varies from 88.4 to 94.12%, while the magnitude of the majority (60%) of the studied olivines does not exceed 92% and 30% of olivines have Mg#> 93%. We identified 2 groups according Mg # olivine from xenoliths. Group 1 with “typical” mantle values Mg # 88.39-90.70mol%, it is characteristic for fertile peridotites. And group 2 with highly depleted compositions Mg # 91.20-94.12mol%. A high proportion (~ 30%) of peridotites with high magnesian olivines (Mg #> 93 mol%) indicates the presence of a block of highly depleted rocks in the lithospheric mantle beneath the Upper Muna kimberilte field.</p><p>According to the distribution of calcium and chromium in garnets, 10 out of 35 studied garnets from xenoliths belong to diamondiferous harzburgite-dunite paragenesis. According to the distribution of rare-earth elements, we distinguish two groups of garnets. Group 1 includes garnets with typical rare earth element distribution spectra typical for fertile garnets, and group 2 garnets with S-shaped spectra that are characteristic of garnet mineral inclusions in diamonds. We noted a high proportion of garnets with S-shaped REE distribution spectra (~ 66%), as well as garnets belonging to the harzburgite-dunite paragenesis, it indicate a moderate role of metasomatic changes associated with silicate melts, as well as interaction with carbonatite melts enriched in LREE.</p><p>Using clinopyroxene monomineral thermobarometry, we found that the “diamond” window in the lithosphere mantle beneath the Upper Muna field, at the time of kimberlite magmatism (~ 360 Ma) was significant (about 95 km) and was located at a depth of 125 to 220 km.</p><p>The study was supported by the Russian Science Foundation (grant No. 18-17-00249).</p>

Archean Boninite-like Rocks of the Northwestern Youanmi Terrane, Yilgarn Craton: Geochemistry and Genesis

2019 ◽  
Vol 60 (11) ◽  
pp. 2131-2168 ◽  
Author(s):  
Jack R Lowrey ◽  
Derek A Wyman ◽  
Tim J Ivanic ◽  
R Hugh Smithies ◽  
Roland Maas
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Mantle Metasomatism ◽  
Chemical Compositions ◽  
Yilgarn Craton ◽  
Fine Grained ◽  
Mafic Intrusions ◽  
Field Evidence ◽  
Isotopic Analyses ◽  
Geochemical Analyses

Abstract Rocks with chemical compositions similar to Cenozoic boninites occur in many Archean cratons (boninite-like rocks), but they are rarely well-preserved, well-sampled, or presented within chrono- and chemo-stratigraphic context. This study provides a detailed description of the most extensive and well-preserved Archean boninite-like rocks reported to date. Within the 2820 to 2740 Ma magmatic suites of the northwest Youanmi Terrane, Yilgarn Craton, boninite-like rocks occur as two distinct units. The first boninite-like unit is thinner (several 10 s of m thick), occurs close to the base of the 2820–2800 Ma Norie Group and includes both volcanic flows and subvolcanic intrusions. The second boninite-like unit is thicker (locally several 100 s m), occurs near the base of the 2800–2740 Ma Polelle Group and consists of mainly fine-grained volcanic flows with local cumulate units. On average, major and trace element compositions for Youanmi Terrane boninite-like rocks are marginal between basalt, picrite and boninite and they have asymmetrically concave REE patterns, and Th–, Zr–Hf enrichments, similar to many Phanerozoic low-Si boninite suites, but at generally higher MREE–HREE contents. We report over 300 new whole-rock geochemical analyses, and 16 new Sm–Nd isotopic analyses, and associated petrographic evidence, including representative mineral compositions, which we support with published geochemical analyses and several decades of fieldwork in our study area. Comparison between Archean boninite-like rocks and Cenozoic boninites shows that most Archean examples had less depleted sources. We consider two possible petrogenetic models for the Youanmi Terrain examples: (1) they reflect variably contaminated komatiites, or (2) they reflect melts of metasomatised refractory mantle, analogous to Phanerozoic boninites. Trace element modelling indicates that crustal contamination could potentially produce rocks with boninite-like compositions, but requires an Al-enriched komatiitic parent liquid, for which there is no field evidence in our study area. Initial εNdT values in pre-2800 Ma rocks (εNdT -0·4 to +1·2) are on average slightly higher than those in 2800–2733 Ma examples (εNdT -3·2 to +1·2), compatible with increasing mantle metasomatism involving recycling of ≥ 2950 Ma crust. Integration of trace element and Nd isotopic data demonstrates that significant direct crustal assimilation was restricted to felsic magmas. The Th–Nb and Ba–Th systematics of mafic-intermediate rocks reflect fluid- and sediment-derived processes in the mantle, with boninite-like examples being linked primarily to fluid metasomatism. We compare the well-preserved igneous textures and mineralogy of Youanmi Terrane boninite-like rocks with those of their Phanerozoic counterparts, and based on studies of the latter, suggest that former had similarly hot, H2O-rich parent magmas. The association of boninite-like rocks in the Norie and Polelle Groups with coeval high-Mg andesites, sanukitoids and hydrous mafic intrusions of the Narndee Igneous Complex strongly suggests a metasomatised mantle source and subduction operating in the Yilgarn between 2820 and 2730 Ma.

Inclusions of crichtonite-group minerals in Cr-pyropes from the Internatsionalnaya kimberlite pipe, Siberian Craton: Crystal chemistry, parageneses and relationships to mantle metasomatism

Lithos ◽  
2018 ◽  
Vol 308-309 ◽  
pp. 181-195 ◽  
Author(s):  
Dmitriy I. Rezvukhin ◽  
Vladimir G. Malkovets ◽  
Igor S. Sharygin ◽  
Irina G. Tretiakova ◽  
William L. Griffin ◽  
...  
Keyword(s):  
Crystal Chemistry ◽  
Siberian Craton ◽  
Kimberlite Pipe ◽  
Mantle Metasomatism

Generation of Late Cretaceous Ji’an basalts through asthenosphere-slab interaction in South China

2020 ◽  
Vol 132 (5-6) ◽  
pp. 1316-1332 ◽  
Author(s):  
Yangming Wu ◽  
Feng Guo ◽  
Xuan-Ce Wang ◽  
Bo Zhang ◽  
Xiaobing Zhang ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Oceanic Crust ◽  
Late Cretaceous ◽  
South China ◽  
Melt Inclusions ◽  
Melt Inclusion ◽  
Geochemical Data ◽  
Oceanic Plate ◽  
Asthenospheric Mantle ◽  
Geochemical Analyses

Abstract Recycled crustal components have been widely identified in the source of continental basalts with geochemical features similar to oceanic island basalts (OIBs). However, the mechanism of how these recycled materials are involved remains highly debatable. Here we conduct comprehensive geochemical analyses (including whole-rock, olivine, and melt inclusion) and numerical modeling on Late Cretaceous Ji’an basalts from South China interior, aiming to investigate the possible role of recycled crustal components in basalt petrogenesis driven by the subducted paleo-Pacific oceanic plate. The Ji’an basalts show geochemical characteristics akin to OIBs and have depleted asthenospheric mantle-like Sr-Nd-Pb-Hf isotopic compositions with moderately radiogenic Os. Their olivine-hosted melt inclusions have low H2O and highly negative δD values and olivine phenocrysts are mainly characterized by depletion of 18O with δ18O values lowering to 3.9‰. These features are consistent with positive Sr and Eu anomalies in some whole-rock samples. The combined geochemical data suggest that the primary magmas were derived from an asthenospheric mantle enriched by melts from an altered gabbroic oceanic crust, which had experienced intensive dehydration. Further numerical modeling shows that melting of the dehydrated oceanic crust can occur along the torn flank of the subducting lithosphere, in the case that the slab is strongly thinned and fractured. The low δ18O preserved in olivine and the estimated slab age (<300 Ma) from the radiogenic whole-rock Os and Pb compositions also require the involvement of a recently recycled slab, probably represented by the subducted paleo-Pacific oceanic plate. Rollback of the subducting paleo-Pacific slab might create a slab window, in which melt from the torn/fractured slab reacted with the upwelling asthenosphere to form an enriched mantle source for the Ji’an basalts and similar counterparts.

Mineral inclusions in sublithospheric diamonds from Collier 4 kimberlite pipe, Juina, Brazil: subducted protoliths, carbonated melts and primary kimberlite magmatism

2010 ◽  
Vol 160 (4) ◽  
pp. 489-510 ◽  
Author(s):  
Galina P. Bulanova ◽  
Michael J. Walter ◽  
Chris B. Smith ◽  
Simon C. Kohn ◽  
Lora S. Armstrong ◽  
...  
Keyword(s):  
Kimberlite Pipe ◽  
Mineral Inclusions
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