scholarly journals Growth of the Archean sialic crust as revealed by zircon in the TTGs in eastern Finland

2021 ◽  
Vol 93 (2) ◽  
pp. 77-104
Author(s):  
Pentti Hölttä ◽  
◽  
Irmeli Mänttäri ◽  
Hannu Huhma ◽  
Matti Kurhila ◽  
...  
Keyword(s):  
Fennoscandian Shield ◽  
Zircon Population ◽  
Sialic Crust ◽  
Icp Ms ◽  
Depleted Mantle ◽  
Archean Crust ◽  
Eastern Finland ◽  
Age Determinations

U–Pb age determinations on zircon from granitoids in the Archean of eastern Finland were conducted using the SIMS, LA-ICP-MS and TIMS techniques, with an emphasis on low-HREE granitoids. The oldest rocks in the Fennoscandian Shield are 3.4–3.5 Ga. Several samples were collected close to these rocks, but none of the samples were as old, indicating that the oldest rocks are only small, possibly allochthonous fragments in the Neoarchean bedrock. Some tonalite–trondhjemite–granodiorite (TTG) samples yielded homogeneous 2.72–2.73 Ga zircon populations, and in these samples, the initial εNd was also close to the depleted mantle (DM) values. However, several granitoid samples with a main zircon population of 2.7–2.8 Ga had 2.9–3.2 Ga grains or inherited cores, and in some samples, all grains were of 2.9–3.0 Ga. In these samples, the εNd value was also close to zero or slightly negative. These features suggest that apart from the juvenile Neoarchean magmas, the abundance of reworked 2.9 Ga material is considerable in the Archean crust, which developed during successive juvenile magmatic inputs that melted and assimilated the older sialic crust. The low- HREE geochemical character of granitoids has no correlation with their age, with the low-HREE granitoids yielding an age span of 2.72–2.98 Ga.

Petrogenesis of silicic magmatism related to the ∼2.44 Ga rifting of Archean crust in Koillismaa, eastern Finland

Lithos ◽  
2006 ◽  
Vol 86 (1-2) ◽  
pp. 137-166 ◽  
Author(s):  
L.S. Lauri ◽  
O.T. Rämö ◽  
H. Huhma ◽  
I. Mänttäri ◽  
J. Räsänen
Keyword(s):  
Archean Crust ◽  
Silicic Magmatism ◽  
Eastern Finland

Detrital zircon populations of the eastern Laurentian margin in the Appalachians

Geology ◽  
2020 ◽  
Author(s):  
Yvette D. Kuiper ◽  
Christopher Hepburn
Keyword(s):  
United States ◽  
Detrital Zircon ◽  
Orogenic Belt ◽  
Grenville Province ◽  
Zircon Age ◽  
Zircon Population ◽  
Middle Ordovician ◽  
Archean Crust ◽  
Laurentian Margin

Newly compiled U-Pb detrital zircon data from eight geographic domains along the eastern Laurentian margin from Newfoundland (Canada) to Alabama (United States) show a highly consistent signature along strike, with only minor local variations. The Precambrian signature is characterized by a small ca. 2.7 Ga population and a major ca. 1.9–0.9 Ga population that peaks at ca. 1.2–1.0 Ga. Detrital zircon populations are from Laurentian Archean crust (ca. 2.7 Ga population), Paleoproterozoic orogens (ca. 1.9–1.6 Ga), the Granite-Rhyolite Province (ca. 1.5–1.4 Ga), and the Elzevir terrane and Grenville Province (ca. 1.3–0.9 Ga). The Mesoproterozoic populations vary in size depending on proximity to the ca. 1.5–1.4 Ga Granite-Rhyolite Province, the ca. 1245–1225 Ma Elzevir terrane, and the ca. 1.2–0.9 Ga Grenville Province. A middle Ordovician zircon population varies in size along strike depending on input from the Taconic orogenic belt, but it is strongest in the northern Appalachians. Because of the general along-strike consistency in detrital zircon age populations, the compilation of all 7534 concordant U-Pb detrital zircon data can be used in future U-Pb detrital zircon studies as an indicator for eastern Laurentian margin sources.

Geochemical researches in situ (LA-ICP-MS) of accessory and ore minerals from multimetal (PGE, Cu-Ni) deposits in the Arctic zone (Fennoscandian Shield) of the Russian Federation

2020 ◽  
Author(s):  
Svetlana Drogobuzhskaya ◽  
Tamara Bayanova ◽  
Andrey Novikov
Keyword(s):  
Inductively Coupled Plasma ◽  
Arctic Region ◽  
Sulfide Minerals ◽  
Fennoscandian Shield ◽  
The Arctic ◽  
Local Analysis ◽  
Icp Ms ◽  
Ore Minerals ◽  
Rfbr Grant

<p>The laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) is a unique method for local analysis that allows studying mineral grains in situ. The aims of these geochemical researches are to estimate concentrations and distributions of REE, Hf, U, Th, Y, Ti, PGE and other elements in accessory and ore minerals from complex deposits in the Arctic region (Fennoscandian Shield), using the LA-ICP-MS local analysis of trace elements. Accessory minerals of zircon and baddeleyite are much valued to study distributions of rare and rare earth elements (REE). Besides, pyrite, pentlandite, pyrrhotite and other sulfides are important for determining platinum-group elements (PGE), REE, etc.</p><p>The electron (LEO-1415) and optic (LEICA OM 2500 P, camera DFC 290) spectroscopy have been applied to study the morphology of the samples. Analytical points have been selected on baddeleyite, zircon crystals and sulfide minerals based on analyses of their BSE, CL and optical images. REE, PGE and other elements have been estimated in situ by ICP-MS, using an ELAN 9000 DRC-e (Perkin Elmer) quadrupole mass spectrometer equipped with UP-266 MAСRO laser (New Wave Research).</p><p>More than 19 elements were profiled during each measurement in zircon or baddeleyite. For the first time, LA-ICP-MS techniques have been applied to estimate PGE, REE and other (S, Cr, Fe, Cu, Ni, Co, As, Se, Mo, Cd, Sn, Sb, Re, Te, Tl, Hf, W, Bi, Pb, Th, U) elements in sulfide minerals. NIST 610, NIST 612 and tandem graduation (using solutions), considering sensitivity coefficients of isotopes have been used to check the accuracy of estimations. Fe, Ni and Cu have been used as internal standards, being most evenly distributed elements in minerals, when concentrations of elements in sulphides were calculated. The estimates have been carried out, using inter-laboratory standards of chalcopyrite, pentlandite and pyrrhotite, which had been preliminarily prepared and studied using micro probe analysis (Cameca MS-46).</p><p>These techniques had been used to estimate elements in zircon extracted from basic and acidic rocks of the Lapland belt (1.9 Ga), the Keivy zone (2.7 Ga), the Kandalaksha and Kolvitsa zone (2.45 Ga) and from the Cu-Ni deposit (Terrace, Mt. Nyud, 2.5 Ga). Novel techniques have been used to analyze baddeleyite from rocks of layered PGE intrusions of the Monchegorsk ore area (2.5 Ga) and carbonatites of Kovdor and Vuoriyarvi (380 Ma). Elaborated LA-ICP-MS techniques have been applied to provide in situ measurements of PGE, Au, Ag, siderophile and chalcophile elements in sulphide minerals from the Pechenga and Allarechka Cu-Ni deposits (1.98 Ga), Fedorova Tundra and Severny Kamennik PGE deposits (2.5 Ga).</p><p>The scientific researches are supported by RFBR Grant No 18-05-70082, scientific themes 0226-2019-0032 and 0226-2019-0053.</p>

The zircon ‘matrix effect’: evidence for an ablation rate control on the accuracy of U–Pb age determinations by LA-ICP-MS

2014 ◽  
Vol 29 (6) ◽  
pp. 981-989 ◽  
Author(s):  
E. Marillo-Sialer ◽  
J. Woodhead ◽  
J. Hergt ◽  
A. Greig ◽  
M. Guillong ◽  
...  
Keyword(s):  
Matrix Effect ◽  
Rate Control ◽  
Ablation Rate ◽  
Systematic Bias ◽  
Zircon Dating ◽  
Icp Ms ◽  
Age Determinations

This papers describes the source of systematic bias in U–Pb zircon dating by LA-ICP-MS.

Isotope systematics (Pb-Nd-Sr) and LA-ICP-MS (REE, Os, PGE) data on time, duration and origin of Paleoproterozoic complex deposits in the N-E part of the Arctic region, Fennoscandian Shield

2021 ◽  
Author(s):  
Tamara Bayanova ◽  
Pavel Serov ◽  
Svetlana Drogobuzhskaya
Keyword(s):  
Arctic Region ◽  
Fennoscandian Shield ◽  
The Arctic ◽  
Layered Intrusions ◽  
Time Duration ◽  
Time Activity ◽  
Sulphide Minerals ◽  
Icp Ms ◽  
Mantle Reservoir ◽  
Isotope Systematics

<p>The isotope U-Pb system on zircon and baddeleyite reflects the precise age of the origin (2.5, 2.45 and 2.4 Ga) and duration (more than 100 Ma) for Cu-Ni and PGE complex deposits widespread in the N-E part of the Fennoscandian Shield. The Monchegorsk, Fedorovo-Pansky and Mt. Generalskaya layered intrusions and ore regions of the orthomagmatic Cu-Ni and PGE deposits with Pt-Pd reefs originated on the continental crust (3.7 Ga). Main phases of gabbronorites were formed mainly at 2.5 Ga and secondary anorthosites at 2.45 Ga, according to U-Pb data on zircon-baddeleyite geochronometries. The Imandra lopolith with Cr deposits was active from 2.45 Ga to 2.4 Ga due to dyke deformation complexes. Isotope Sm-Nd studies and investigations of rock-forming and sulphide minerals from the deposits indicated coeval ages and 3 magmatic time activity with positive epsilon Nd. Deformation or metamorphic events were dated using the Rb-Sr system on minerals and whole rocks from the deposits at 1.9-1.8 Ga.</p><p>The Pados Cr (2.08 Ga), Pechenga Cu-Ni (1.98 Ga) and Kolvitsa Ti-Mg (1.89 Ga) orthomagmatic deposits were dated, using the Pb-Nd-Sr isotope systematics. The mentioned deposits originated probably on the oceanic crust (2.7 Ga). According to new in situ LA-ICP-MS data on Os, PGE and REE concentration in zircon, baddeleyite and sulphide minerals from the complex deposits are characterized by subchondritic sources (Malitch et al., 2019). Paleoproterozoic layered intrusions (2.5-1.8 Ga) and deposits were formed from the plume enrichment mantle reservoir (EM-1), according to Nd-Sr data on whole rocks. Baddeleyite as a mantle mostly mineral (Zircon, 2003) reflects the continental break-up and is connected with the oldest supercontinental reconstruction (Ernst, 2016).</p><p>All studies have been supported by RFRB 18-05-70082, Scientific Research Contracts Nos 0226-2019-0032 and 0226-2019-0053.</p>

Petrogenesis of Mesoproterozoic (Subjotnian) rapakivi complexes of central Sweden: implications from U–Pb zircon ages, Nd, Sr and Pb isotopes

2001 ◽  
Vol 92 (3) ◽  
pp. 201-228 ◽  
Author(s):  
U. B. Andersson ◽  
L. A. Neymark ◽  
K. Billström
Keyword(s):  
Lower Crust ◽  
Fennoscandian Shield ◽  
Zircon Geochronology ◽  
Pb Isotope ◽  
Isotopic Signatures ◽  
Melt Extraction ◽  
Depleted Mantle ◽  
Source Component ◽  
Age Range ◽  
Basic Rocks

ABSTRACTU-Pb zircon geochronology of Mesoproterozoic (Subjotnian) rapakivi complexes in central Sweden yields: 1526 ± 3 Ma (Mullnäset), 1524 ± 3 Ma (Mårdsjö), 1520 ± 3 Ma (Nordsjö) and 1497 ± 6 Ma (Rödön). Together with complexes further S in Sweden, they constitute the westernmost, youngest (1·53−1·47 Ga) belt of rapakivi magmatism in the Fennoscandian shield.The low initial εNd values (−8·9 to −4·8) of all studied Subjotnian basic, intermediate and silicic rocks, require an input from an old (Archaean) low-radiogenic source component, as evidence for Palaeoproterozoic protoliths in the age range 2·5−2·1 Ga is lacking in this region. Crustal, early Svecofennian + Archaean (roughly 30−40%) sources are suggested for the Subjotnian A-type granites and syenites, where the granites derive from undepleted, granodioritic, and the syenites from monzodioritic (±depleted crustal) protoliths. The basic rocks originate from a depleted mantle acquiring the enriched Nd isotopic signatures during interaction with an Archaean lower crust (20−40%), largely depleted after rapakivi melt extraction. Pb isotope data from feldspars (207Pb/204Pb to 15·018−15·542) support the presence of Archaean components in the magmas.The results indicate that an Archaean basement is underlying relatively wide areas of Svecofennian formations in central Sweden. This old basement section was most likely rifted off the Archaean craton in the NE in Palaeoproterozoic times.

scholarly journals Significance of Baddeleyite for Paleoproterozoic PGE Deposits with Pt-Pd and Cu-Ni reefs (North-Eastern Fennoscandian Shield): New Results of U-Pb and LA-ICP-MS Studies

2020 ◽  
pp. 1-7
Author(s):  
Bayanova Т.B. ◽  
Drogobuzhskaya S.V. ◽  
Subbotin V.V. ◽  
Serov P.А. ◽  
Steshenko Е.N. ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Fennoscandian Shield ◽  
Layered Intrusions ◽  
Inductively Coupled ◽  
The North ◽  
Icp Ms ◽  
North Eastern ◽  
Plasma Mass Spectrometry ◽  
First Time

Baddeleyite is a significant mineral successfully applied in the U-Pb geochronology for the precise dating of mafic rocks from layered intrusions with the platinum group element (PGE) and Cu-Ni mineralization. The Fennoscandian Shield hosts several layered Pt-Pd, Co-Cr-Ni, and Ti-V occurrences in the Northern (Karelian) and Southern (Karelian-Finnish) belts. The aim of this study is to estimate the content and distribution of rare earth elements (REE) in baddeleyite and to calculate temperatures (Т, ̊С) of the U-Pb system closure and baddeleyite crystallization compared to zircon from Cu-Ni and Pt-Pd deposits in the north-eastern Fennoscandian Shield. For the first time, baddeleyite crystals from Cu-Ni (Monchepluton) and Pt-Pd (Monchetundra) reefs of the Monchegorsk ore area have been studied in situ by the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure the U-Pb age of formation and the REE content.

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