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Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores

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A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (20 July 2020) | Viewed by 29575

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Special Issue Editors

Dr. Igor Ashchepkov

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Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia
Interests: mantle xenolith; xenocryst thermobarometry; geochemistry; magmas; peridotites; eclogites; craton layering
Special Issues, Collections and Topics in MDPI journals

Prof. Martin Flower

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Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
Interests: young and old (Atlantic and Pacific) oceanic crust; fractionation of polybaric magma systems; magmatism at convergent and collisional plate margins and backarc basins; intra-plate basalt volcanism; ophiolites

Prof. Eugenii Sharkov

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Guest Editor

Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Staromonetny per., 35, 119017 Moscow, Russia
Interests: magma differentiation; layered intrusions; evolution of within-plate magmatism; basalt granites; plumes

Prof. Dr. Sergei Rasskazov

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Guest Editor

1. Institute of the Earth’s crust, Russian Academy of Sciences, Irkutsk, Russia
2. Faculty of Geology, Irkutsk State University, Irkutsk 664033, Russia
Interests: Cenozoic rifts in Central and East Asia, North America, and East Africa; origin of volcanic rocks erupted at the latest geodynamic stage of the evolving Earth
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The proposed Special Issue will include new results pertaining to the deep-seated magmas and the evolution of their deep crust and mantle roots by a range of academic and corporate research groups based in Western Europe, the Russian Federation, East Asia, and North America.

This project will attempt to address the following problem areas:

(1) Structural and compositional reconstruction of lithospheric mantle in response to mantle plume and subduction activity;
(2) Interactions of plume- and subduction-related melts and fluids with the continental lithosphere mantle, and associated metasomatic processes;
(3) The nature of magmatic sources, petrogenetic conditions (P-T-fO2), and melting within and below the lithosphere and sublithospheric mantle;
(4) Melting processes, fluid migration, and phase transformations associated with deep mantle plume regions;
(5) Modes of melt migration and ascent as constrained by numerical modelling and microstructures of mantle xenoliths;
(6) The role of mantle melts and fluids in generating hybrid and acid magmas;
(7) Ore genesis in layered intrusions and carbonatites.

These topics will be addressed on the basis of geochemical data for mantle-derived melts, fabric studies of mantle xenoliths, and orogenic peridotites and experimental and computer-based simulations.

Dr. Igor Ashchepkov
Prof. Martin Flower
Prof. Eugenii Sharkov
Prof. Sergei Rasskazov
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Proterozoic magmas and massifs
mountain belts
plumes and hot spots
arc system magmatisms
experimental and numerical modeling
mantle mineralogy and processes
carbonatite
magmatic ore mineralogy

Published Papers (10 papers)

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Research

41 pages, 16504 KiB

Open AccessFeature PaperArticle

Tectonic Generation of Pseudotachylytes and Volcanic Rocks: Deep-Seated Magma Sources of Crust-Mantle Transition in the Baikal Rift System, Southern Siberia

by Sergei Rasskazov, Irina Chuvashova, Tatyana Yasnygina, Elena Saranina, Nikolay Gerasimov, Youseph Ailow and Yi-Min Sun

Minerals 2021, 11(5), 487; https://0-doi-org.brum.beds.ac.uk/10.3390/min11050487 - 02 May 2021

Cited by 1 | Viewed by 2950

Abstract

Volcanic rocks from deep-seated sources of the crust-mantle transition (CMT) are geochemically distinguished from those of ocean island basalts (OIB). Here, we report geochemical data on tectonic pseudotachylytes from the Main Sayan Fault (MSF) and volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT) that represent the deep-seated CMT magmatic sources in the central part of the Baikal Rift System (BRS). The tectonic generation of the KSZHT magmas between 18.1 and 11.7 Ma is compared with present-day seismogenic deformations in the middle-upper crust of the South Baikal Basin and adjacent Tunka Valley, where strong earthquakes are distributed along the Main Sayan and Primorye sutures of the Siberian paleocontinent. From a detail seismic tomography model and geological evidence, we infer that the KSZHT crust–mantle magmatic processes were due to delamination and lamination of a thickened root part of the South Baikal Orogen existed in the Late Cretaceous and Paleogene. In addition, we identify similar deep-seated CMT sources for melts erupted in the past 17 Ma from a delaminated root part of the East Hangay Orogen and adjacent Orkhon-Selenga Saddle in the southwestern BRS. We suggest that both in the central and in the southwestern BRS, the deep-seated CMT magma sources designate cooperative pull-to-axis and convergent effects created in the Japan-Baikal Geodynamic Corridor and in the Indo-Asian interactional region, respectively. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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30 pages, 11603 KiB

Open AccessArticle

Multistage Magmatism in Ophiolites and Associated Metavolcanites of the Ulan-Sar’dag Mélange (East Sayan, Russia)

by Olga N. Kiseleva, Evgeniya V. Airiyants, Dmitriy K. Belyanin, Sergey M. Zhmodik, Igor V. Ashchepkov and Semyon A. Kovalev

Minerals 2020, 10(12), 1077; https://0-doi-org.brum.beds.ac.uk/10.3390/min10121077 - 30 Nov 2020

Cited by 5 | Viewed by 2511

Abstract

We present new whole-rock major and trace element, mineral chemistry, and U-Pb isotope data for the Ulan-Sar’dag mélange, including different lithostratigraphic units: Ophiolitic, mafic rocks and metavolcanites. The Ulan-Sar’dag mélange comprises of a seafloor and island-arc system of remnants of the Paleo-Asian Ocean. Detailed studies on the magmatic rocks led to the discovery of a rock association that possesses differing geochemical signatures within the studied area. The Ulan-Sar’dag mélange includes blocks of mantle peridotite, podiform chromitite, cumulate rocks, deep-water siliceous chert, and metavolcanic rocks of the Ilchir suite. The ophiolitic unit shows overturned pseudostratigraphy. The nappe of mantle tectonites is thrusted over the volcanic-sedimentary sequence of the Ilchir suite. The metavolcanic series consist of basic, intermediate, and alkaline rocks. The mantle peridotite and cumulate rocks formed in a supra-subduction zone environment. The mafic and metavolcanic rocks belong to the following geochemical types: (1) Ensimatic island-arc boninites; (2) island-arc calc-alkaline andesitic basalts, andesites, and dacites; (3) tholeiitic basalts of mid-ocean ridges; and (4) oceanic island basalts. U–Pb dating of zircons from the trachyandesite, belonging to the second geochemical type, yielded a date of 833 ± 4 Ma which is interpreted as the crystallization age during mature island-arc and intra-arc rifting stages. The possible influence of later plume magmatic-hydrothermal activities led to the appearance of moderately alkaline igneous rocks (monzogabbro, trachybasalt, trachyandesite, subalkaline gabbro, and metasomatized peridotites) with a significant subduction geochemical fingerprint. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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29 pages, 5251 KiB

Open AccessArticle

Thermobarometry and Geochemistry of Mantle Xenoliths from Zapolyarnaya Pipe, Upper Muna Field, Yakutia: Implications for Mantle Layering, Interaction with Plume Melts and Diamond Grade

by Igor Ashchepkov, Nikolay Medvedev, Nikolay Vladykin, Alexander Ivanov and Hilary Downes

Minerals 2020, 10(9), 755; https://0-doi-org.brum.beds.ac.uk/10.3390/min10090755 - 26 Aug 2020

Cited by 5 | Viewed by 3293

Abstract

Minerals from mantle xenoliths in the Zapolyarnaya pipe in the Upper Muna field, Russia and from mineral separates from other large diamondiferous kimberlite pipes in this field (Deimos, Novinka and Komsomolskaya-Magnitnaya) were studied with EPMA and LA-ICP-MS. All pipes contain very high proportions of sub-calcic garnets. Zapolyarnaya contains mainly dunitic xenoliths with veinlets of garnets, phlogopites and Fe-rich pyroxenes similar in composition to those from sheared peridotites. PT estimates for the clinopyroxenes trace the convective inflection of the geotherm (40–45 mW·m⁻²) to 8 GPa, inflected at 6 GPa and overlapping with PT estimates for ilmenites derived from protokimberlites. The Upper Muna mantle lithosphere includes dunite channels from 8 to 2 GPa, which were favorable for melt movement. The primary layering deduced from the fluctuations of CaO in garnets was smoothed by the refertilization events, which formed additional pyroxenes. Clinopyroxenes from the Novinka and Komsomolskaya-Magnitnaya pipes show a more linear geotherm and three branches in the P-Fe# plot from the lithosphere base to the Moho, suggesting several episodes of pervasive melt percolation. Clinopyroxenes from Zapolyarnaya are divided into four groups according to thermobarometry and trace element patterns, which show a stepwise increase of REE and incompatible elements. Lower pressure groups including dunitic garnets have elevated REE with peaks in Rb, Th, Nb, Sr, Zr, and U, suggesting mixing of the parental protokimberlitic melts with partially melted metasomatic veins of ancient subduction origin. At least two stages of melt percolation formed the inclined PT paths: (1) an ancient garnet semi-advective geotherm (35–45 mW·m⁻²) formed by volatile-rich melts during the major late Archean event of lithosphere growth; and (2) a hotter megacrystic PT path (Cpx-Ilm) formed by feeding systems for kimberlite eruptions (40–45 mW·m⁻²). Ilmenite PT estimates trace three separate PT trajectories, suggesting a multistage process associated with metasomatism and formation of the Cpx-Phl veinlets in dunites. Heating associated with intrusions of protokimberlite caused reactivation of the mantle metasomatites rich in H₂O and alkali metals and possibly favored the growth of large megacrystalline diamonds. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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39 pages, 13506 KiB

Open AccessArticle

Mantle Evolution of Asia Inferred from Pb Isotopic Signatures of Sources for Late Phanerozoic Volcanic Rocks

by Sergei Rasskazov, Irina Chuvashova, Tatyana Yasnygina and Elena Saranina

Minerals 2020, 10(9), 739; https://0-doi-org.brum.beds.ac.uk/10.3390/min10090739 - 21 Aug 2020

Cited by 2 | Viewed by 2568

Abstract

We present a systematic study of Pb isotope ages obtained from sources of the late Phanerozoic volcanic rocks from unstable Asia and also volcanic rocks and kimberlites from stable regions of the Siberian and Indian paleocontinents. In the mantle sources, we have recorded events of the Early, Middle, and Late epochs of the Earth’s evolution. Evidence on the Early epoch are preserved in sources of the protolithosphere and viscous lower protomantle likely generated from the Hadean magma ocean about 4.51 and 4.44 Ga and in sources of the viscous upper mantle that acquired low µ and elevated µ (LOMU and ELMU) signatures in the early Archean (4.0–3.7 Ga). The Middle and Late epochs are denoted by sources of the viscous upper mantle that was generated, respectively, in the late Archean-Paleoproterozoic (2.9–2.6 Ga and 2.0–1.8 Ga) and in the Neoproterozoic-late Phanerozoic (0.7–0.6 Ga and < 0.25 Ga). Our results show the specific role of the mantle beneath unstable Asia in terms of globally varied µ signatures and the same mantle epochs in sources of the late Phanerozoic volcanic rocks and kimberlites from stable regions of the Siberian and Indian paleocontinents, but with high μ (HIMU) signatures that are distributed worldwide and explained by sulfide sequestration of Pb from the mantle to the core. We refer the LOMU-ELMU mantle sources to the Asian high-velocity lower mantle domain and propose that the HIMU generating processes were focused mainly in the South Pacific and African low-velocity lower mantle domains in the Middle Mantle Epoch of the Earth’s evolution due to influence of the unbalanced solid core. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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29 pages, 9037 KiB

Open AccessArticle

Aillikites and Alkali Ultramafic Lamprophyres of the Beloziminsky Alkaline Ultrabasic-Carbonatite Massif: Possible Origin and Relations with Ore Deposits

by Igor Ashchepkov, Sergey Zhmodik, Dmitry Belyanin, Olga N. Kiseleva, Nikolay Medvedev, Alexei Travin, Denis Yudin, Nikolai S. Karmanov and Hilary Downes

Minerals 2020, 10(5), 404; https://0-doi-org.brum.beds.ac.uk/10.3390/min10050404 - 29 Apr 2020

Cited by 14 | Viewed by 3154

Abstract

The 650–621 Ma plume which impinged beneath the Siberian craton during the breakup of Rodinia caused the formation of several alkaline carbonatite massifs in craton margins of the Angara rift system. The Beloziminsky alkaline ultramafic carbonatite massif (BZM) in the Urik-Iya graben includes alnöites, phlogopite carbonatites and aillikites. The Yuzhnaya pipe (YuP) ~ 645 Ma and the 640–621 Ma aillikites in BZM, dated by ⁴⁰Ar/³⁹Ar, contain xenoliths of carbonated sulfide-bearing dunites, xenocrysts of olivines, Cr-diopsides, Cr-phlogopites, Cr-spinels (P ~ 4–2 GPa and T ~ 800–1250 °C) and xenocrysts of augites with elevated HFSE, U, Th. Al-augites and kaersutites fractionated from T ~ 1100–700 °C along the 90 mW/m² geotherm. Higher T trend for Al-Ti augite, pargasites, Ti-biotites series (0.4–1.5 GPa) relate to intermediate magma chambers near the Moho and in the crust. Silicate xenocrysts show Zr-Hf, Ta-Nb peaks and correspond to carbonate-rich magma fractionation that possibly supplied the massif. Aillikites contain olivines, rare Cr-diopsides and oxides. The serpentinites are barren, fragments of ore-bearing Phl carbonatites contain perovskites, Ta-niobates, zircons, thorites, polymetallic sulphides and Ta-Mn-Nb-rich magnetites, ilmenites and Ta-Nb oxides. The aillikites are divided by bulk rock and trace elements into seven groups with varying HFSE and LILE due to different incorporation of carbonatites and related rocks. Apatites and perovskites reveal remarkably high LREE levels. Aillikites were generated by 1%–0.5% melting of the highly metasomatized mantle with ilmenite, perovskite apatite, sulfides and mica, enriched by subduction-related melts and fluids rich in LILE and HFSE. Additional silicate crystal fractionation increased the trace element concentrations. The carbonate-silicate P-bearing magmas may have produced the concentration of the ore components and HFSE in the essentially carbonatitic melts after liquid immiscibility in the final stage. The mechanical enrichment of aillikites in ore and trace element-bearing minerals was due to mixture with captured solid carbonatites after intrusion in the massif. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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24 pages, 6333 KiB

Open AccessArticle

Trace-Element and Pb Isotope Evidence on Extracting Sulfides from Potassic Melts beneath Longmenshan and Molabushan Volcanoes, Wudalianchi, Northeast China

by Sergei Rasskazov, Yi-Min Sun, Irina Chuvashova, Tatyana Yasnygina, Chen Yang, Zhenhua Xie, Elena Saranina, Nikolay Gerasimov and Tatyana Vladimirova

Minerals 2020, 10(4), 319; https://0-doi-org.brum.beds.ac.uk/10.3390/min10040319 - 31 Mar 2020

Cited by 3 | Viewed by 2457

Abstract

In the Wudalianchi volcanic field, eruptions started with low-Mg potassic lava flows 2.5–2.0 Ma ago and later changed to both low- and moderate-Mg potassic compositions. Volcanic rocks from the Molabushan and Longmenshan volcanoes record an unusually wide range of Pb abundances (from 3.7 ppm to 21 ppm relative to predominant range of 10–15 ppm). To determine the cause of these, we performed a comparative trace-element and Pb isotope study of rocks from these volcanoes and older lava flows. On a uranogenic lead diagram, older low-Mg lavas from lithospheric mantle sources plot on a secondary isochron with a slope corresponding to an age of 1.88 Ga. This contrasts with moderate-Mg volcanic rocks from the Molabushan cone, interpreted to have been derived from a recent convective mantle source, which define a flat linear pattern. Low-Mg rocks from the Molabushan flow have lead isotopic compositions that indicate mixed Gelaqiu and Molabu sources. Relative to rocks from the Molabushan cone, moderate-Mg lavas and slags from the East Longmenshan volcano have modified compositions characterized by Pb, S, and Ni abundances, Ni/Co, Ni/MgO ratios as well as ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb, Ce/Pb, Th/Pb, and U/Pb ratios. We infer that the older Wudalianchi magmas were likely derived from a Paleoproterozoic lithospheric fragment, related to the evolved primordial mantle, and that later magmas were generated in the convecting mantle. These were influenced by segregation of small amounts of sulfides. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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17 pages, 3739 KiB

Open AccessArticle

The Origin and Evolution of Ore-Bearing Rocks in the Loypishnun Deposit (Monchetundra Massif, NE Fennoscandian Shield): Isotope Nd-Sr and REE Geochemical Data

by Evgeniy Kunakkuzin, Elena Borisenko, Luydmila Nerovich, Pavel Serov, Tamara Bayanova and Dmitry Elizarov

Minerals 2020, 10(3), 286; https://0-doi-org.brum.beds.ac.uk/10.3390/min10030286 - 21 Mar 2020

Cited by 4 | Viewed by 3053

Abstract

The Monchetundra massif is located in the north-eastern Fennoscandian Shield and refers to Paleoproterozoic massifs of the East-Scandinavian Large Igneous Province. The general section of the massif comprises two parts, the lower norite-orthopyroxenite and the upper mafic zones. The lower zone is of great interest due to its associated industrial platinum group elements (PGE) mineralization. The structure and peculiar features of rocks in the lower zone were studied using a drill core from the borehole MT-70 in the south-eastern slope of the Monchetundra massif intersecting the ore zone 1 of the Loypishnun deposit (according to the CJSC Terskaya Mining Company data). A comparison of the barren and ore-bearing varieties of norites and pyroxenites in the Loypishnun deposit shows that the ore samples have the lowest negative εNd values, a relatively more differentiated distribution spectrum with the Light rare earth elements (LREE) dominating over the Heavy REE (HREE), Eu/Eu* ≥ 1, and a higher mean content of alkali and large-ion lithophile elements (Ba, Rb, and Cs). New geochemical data indicated an origin of magmas for rocks from a layered series in the Loypishnun deposit by a high degree of melting of a LREE-rich source with a low mean content of REE. Negative εNd values, low ISr values, and a marked negative Nb indicate that the crustal material affected the evolution of rocks in the lower zone of the massif more than in the upper zone. The formation of ore bodies in the Loypishnun deposit was governed by the crust-mantle interaction, magmatic differentiation, and association with the most differentiated varieties, and by further concentration of the ore at the late and post-magmatic stages in a highly permeable environment for fluids in the Monchetundra fault zone. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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16 pages, 4877 KiB

Open AccessArticle

The Paleoproterozoic Kandalaksha-Kolvitsa Gabbro-Anorthosite Complex (Fennoscandian Shield): New U–Pb, Sm–Nd, and Nd–Sr (ID-TIMS) Isotope Data on the Age of Formation, Metamorphism, and Geochemical Features of Zircon (LA-ICP-MS)

by Ekaterina N. Steshenko, Tamara B. Bayanova and Pavel A. Serov

Minerals 2020, 10(3), 254; https://0-doi-org.brum.beds.ac.uk/10.3390/min10030254 - 10 Mar 2020

Cited by 4 | Viewed by 2943

Abstract

The paper provides new U–Pb, Sm–Nd, and Nd–Sr isotope-geochronological data on rocks of the Paleoproterozoic Kandalaksha-Kolvitsa gabbro-anorthosite complex. Rare earth element (REE) contents in zircons from basic rock varieties of the Kandalaksha-Kolvitsa area were analyzed in situ using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Plots of REE distribution were constructed, confirming the magmatic origin of zircon. Temperatures of zircon crystallization were estimated using a Ti-in-zircon geochronometer. The U–Pb method with a ²⁰⁵Pb artificial tracer was first applied to date single zircon grains (2448 ± 5 Ma) from metagabbro of the Kolvitsa massif. The U–Pb analysis of zircon from anorthosites of the Kandalaksha massif dated the early stage of the granulite metamorphism at 2230 ± 10 Ma. The Sm–Nd isotope age was estimated on metamorphic minerals (apatite, garnet, sulfides) and whole rock at 1985 ± 17 Ma (granulite metamorphism) for the Kolvitsa massif and at 1887 ± 37 Ma (high-temperature metasomatic transformations) and 1692 ± 71 Ma (regional fluid reworking) for the Kandalaksha massif. The Sm–Nd model age of metagabbro was 3.3 Ga with a negative value of εNd = 4.6, which corresponds with either processes of crustal contamination or primary enriched mantle reservoir of primary magmas. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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19 pages, 4462 KiB

Open AccessArticle

Metallogenic Setting and Evolution of the Pados-Tundra Cr-Bearing Ultramafic Complex, Kola Peninsula: Evidence from Sm–Nd and U–Pb Isotopes

by Pavel A. Serov, Tamara B. Bayanova, Ekaterina N. Steshenko, Evgeniy L. Kunakkuzin and Elena S. Borisenko

Minerals 2020, 10(2), 186; https://0-doi-org.brum.beds.ac.uk/10.3390/min10020186 - 19 Feb 2020

Cited by 10 | Viewed by 3071

Abstract

The article presents new Sm–Nd and U–Pb geochronological data on rocks of the poorly studied Pados-Tundra Cr-bearing complex. It is part of the Notozero mafic–ultramafic complex (western Kola Peninsula) and occurs at the border of the Paleoproterozoic Lapland Granulite Belt and the Archean Belomorian composite terrain. The Pados-Tundra complex hosts two major zones, the Dunite and Orthopyroxenite Blocks. Dunites are associated with four levels of chromite mineralization. Isotope Sm–Nd studies of dunites, harzburgites, and orthopyroxenites from the central part of the complex have been carried out. The isochron Sm–Nd age on 11 whole-rock samples from a rhythmically layered series of the complex is 2485 ± 38 Ma; the mineral Sm–Nd isochron for harzburgites shows the age of 2475 ± 38 Ma. It corresponds with the time of large-scale rifting that originated in the Fennoscandian Shield. When the rhythmically layered series of the intrusion and its chromite mineralization were formed, hornblendite dykes intruded. The U–Pb and Sm–Nd research has estimated their age at ca. 2080 Ma, which is likely to correspond with the occurrence of the Lapland–Kola Ocean. According to isotope Sm–Nd dating on metamorphic minerals (rutile, amphibole), the age of postmetamorphic cooling of rocks in the complex to 650–600 °C is 1872 ± 76 Ma. The U–Pb age on rutile from a hornblendite dyke (1804 ± 10 Ma) indicates further cooling to 450–400 °C. The conducted research has determined the early Proterozoic age of rocks in the rhythmically layered series in the Pados-Tundra complex. It is close to the age of the Paleoproterozoic ore magmatic system in the Fennoscandian Shield that developed 2.53–2.40 Ga ago. Later episodes of alterations in rocks are directly related to main metamorphic episodes in the region at the turn of 1.9 Ga. Results of the current study expand the geography of the vast Paleoproterozoic East Scandinavian Large Igneous Province and can be applied for further studies of similar mafic–ultramafic complexes. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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20 pages, 6350 KiB

Open AccessArticle

Geochemical Features and Geological Processes Timescale of the Achaean TTG Complexes of the Ingozero Massif and the Pechenga Frame (NE Baltic Shield)

by Elena Nitkina, Nikolay Kozlov, Natalia Kozlova and Tatiana Kaulina

Minerals 2019, 9(12), 767; https://0-doi-org.brum.beds.ac.uk/10.3390/min9120767 - 10 Dec 2019

Cited by 1 | Viewed by 2282

Abstract

This article provides a geological review and results of the structural, metamorphic, and geochronological studies of the Pechenga frame outcrops located in the NW part of the Central-Kola terrain and the Ingozero massif outcrops situated in the northeastern part of the Belomorian mobile belt of the Kola Region (NW Baltic Shield). As a result of the work, the deformation scales and ages of the geological processes at the Neo-Archaean–Paleoproterozoic stage of the area’s development were compiled, and the reference rocks were dated. The petrochemical and geochemical characteristics of the Ingozero rocks are similar to those of tonalite–trondhjemite–granodiorite (TTG) complexes established on other Archaean shields. The isotope U–Pb dating of individual zircon grains from the biotite gneisses provided the oldest age for magmatic protolith of the Ingozero gneisses, which is 3149 ± 46 Ma. Sm–Nd model ages showed that the gneisses protolite initial melt formed at 3.1–2.8 Ga. Ages of metamorphic processes were determined by using isotope U–Pb dating ID TIMS (isotope dilution thermal ionization mass spectrometry): Biotite gneisses—2697 ± 9 Ma; amphibole–biotite gneisses—2725 ± 2 Ma and 2667 ± 7 Ma; and biotite–amphibole gneisses 2727 ± 5 Ma. Ages of granitoids, which cut the deformed gneisses, are 2615 ± 8 Ma and 2549 ± 31 Ma for plagiogranites and pegmatoid veins in gneisses, respectively. The following age sequence of geological processes was established by using U–Pb zircon dating: 2.8 Ga—The time of the garnet–biotite gneiss metamorphism; 2722 ± 9 Ma—The granodiorite crystallization time; 2636 ± 41 Ma—The aplite emplacement age and 2620 ± 16 Ma—The age of pegmatites origin, which marked final stages of the Archaean evolution; 2587 ± 5 Ma—The age of gabbros emplacement and 2507 ± 7 Ma—The age of gabbros metamorphism; 2522–2503 Ma—The origin time of the iron quartzite interpreted as the age of gabbros and biotite gneiss metamorphism. Full article

(This article belongs to the Special Issue Crust and Mantle Magmas as Response on Mantle Dynamics: Genesis, Geochemistry and Ores)

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