The paper "A dynamic 2000—540 Ma Earth history: From cratonic amalgamation to the age of supercontinent cycle" that was recently published in Earth-Science Reviews by Li et al. (2023) is an impressive piece of work, putting together data for the Proterozoic supercontinent cycle into a coherent model including both maps and animations. Nevertheless, as they write themselves, there will no doubt be room for improvements of their model, some of which I hope to contribute with in this comment from my Baltica perspective, in particular when it comes to the relations between Baltica, Amazonia and West Africa.

Supercontinent

Baltica

Rodinia

10.1016/j.earscirev.2023.104457

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Citations (2)

Magmatic activity along the southern part of the Protogine Zone, southern Sweden

Geologiska Foereningan i Stockholm Foerhandlingar (1992)

Åke Johansson

"Magmatic activity along the southern part of the Protogine Zone, southern Sweden." Geologiska Föreningen i Stockholm Förhandlingar, 114(3), pp. 359–360

10.1080/11035899209454807

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Citations (1)

U–Pb SIMS dating of some granitoids from eastern Blekinge, southern Sweden

GFF (2016)

Åke Johansson

Zircons from seven granitoids in eastern Blekinge have been dated using secondary ion mass spectrometry. The analyzed rocks include one Småland granitoid from north of the Småland-Blekinge Deformation Zone (SBDZ), two samples of megacrystic "Filipstad-type" granite from south of that zone and one sample each of the "Småland-type" Rödeby, Almö, Tjurkö and Jämjö granites. The results yield a crystallization age of 1778 ± 5 Ma for the Småland granitoid, and crystallization ages between 1770 ± 4 and 1758 ± 5 Ma for the other granitoids, in most cases substantially older than previous TIMS ages. These data show that the "Småland-type" granitoids in eastern Blekinge are similar in age to the surrounding Tving granitoids, and the more felsic of them may represent late-stage differentiates belonging to the same magmatic suite. As the Tving granitoids show differences both in degree of deformation, in geochemistry and in age, compared to the Småland granitoids north of the SBDZ, it is suggested that these represent two separate but closely related igneous suites, which could both be included within a TIB-1 supersuite. The investigated zircons showed very limited signs of metamorphic overprinting, and no metamorphic ages could be determined. However, the combined evidence from field observations and earlier U–Pb geochronology would suggest the presence of two separate metamorphic episodes in Blekinge, one in close connection with the formation of these rocks at 1.76–1.75 Ga and one connected to the intrusion of the Karlshamn granitoid suite at around 1.45 Ga.

10.1080/11035897.2016.1146328

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The Pre-Caledonian history of Nordaustlandet and Ny Friesland, Svalbard

David G. Gee Åke Johansson Yoshihide Ohta Alexander M. Tebenkov

Source

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Characterization of the Paleoproterozoic Mantle beneath the Fennoscandian Shield: Geochemistry and Isotope Geology (Nd, Sr) of ~ 1.8 Ga Mafic Plutonic Rocks from the Transscandinavian Igneous Belt in Southeast Sweden

International Geology Review (2007)

Ulf B. Andersson Henrikki Rutanen Åke Johansson Joakim Mansfeld Andrius Rimša

Abstract Geochemistry and Sr-Nd isotope geochemistry of ca. 1.8 Ga, mafic intrusions of the Transscandinavian Igneous Belt (TIB-1) in the Fennoscandian shield were studied in southeastern Sweden. These rocks show LILE-LREE-enriched, HFSE-depleted, calc-alkaline, continental arc signatures in the north, grading to slightly less enriched, oceanic affinities southward. ∊Nd(1.80) values range from +2.0 to +0.7 and 87Sr/86Sr(1.80) from 0.7022 to 0.7029 (with one outlier at 0 and 0.7033), without correlation to fractionation (e.g., Mg#) or crustal contamination, indicating sources that are mildly depleted. The most depleted ratios occur in the south, trending with the geochemistry toward more enriched compositions northward. The sources represent depleted mantle wedge material that was subjected to enrichment not long before (TDM ca. 2.0 Ga), i.e., during the preceding arc subduction (2.1-1.82 Ga), and/or during the TIB-1 magmatism itself, by hydrous fluids with a sediment and/or melt input increasing northward. The TIB-1 magmatism occurred above a south(west)ward-retreating subduction zone along the continental margin of the juvenile Svecofennian continent at 1.81-1.76 Ga.

Lile

Continental arc

10.2747/0020-6814.49.7.587

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Citations (47)

Search for H→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector

Physics Letters B (2014)

G. Aad B. Abbott J. Abdallah S. Abdel Khalek O. Abdinov

A search is performed for Higgs bosons produced in association with top quarks using the diphoton decay mode of the Higgs boson. Selection requirements are optimized separately for leptonic and fully hadronic final states from the top quark decays. The dataset used corresponds to an integrated luminosity of 4.5 fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 7 TeV and 20.3 fb$^{-1}$ at 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess over the background prediction is observed and upper limits are set on the $t\bar{t}H$ production cross section. The observed exclusion upper limit at 95% confidence level is 6.7 times the predicted Standard Model cross section value. In addition, limits are set on the strength of the Yukawa coupling between the top quark and the Higgs boson, taking into account the dependence of the $t\bar{t}H$ and $tH$ cross sections as well as the $H \to \gamma\gamma$ branching fraction on the Yukawa coupling. Lower and upper limits at 95% confidence level are set at -1.3 and +8.0 times the Yukawa coupling strength in the Standard Model.

Yukawa potential

Branching fraction

10.1016/j.physletb.2014.11.049

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Citations (83)

Search for W′→tb¯ in the lepton plus jets final state in proton–proton collisions at a centre-of-mass energy of

Physics Letters B (2015)

G. Aad B. Abbott J. Abdallah S. Abdel Khalek O. Abdinov

A search for new charged massive gauge bosons, called $W'$, is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb$^{-1}$. This analysis searches for $W'$ bosons in the $W' \to t\bar{b}$ decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed $W'$ bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the $W' \to t\bar{b}$ cross-section times branching ratio and on the $W'$-boson effective couplings as a function of the $W'$-boson mass using the CL$_s$ procedure. For a left-handed (right-handed) $W'$ boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.

10.1016/j.physletb.2015.02.051

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Citations (53)

Cleaning up the record – revised U-Pb zircon ages and new Hf isotope data from southern Sweden

Figshare (2021)

Åke Johansson

Ten samples of felsic plutonic rocks from the Eastern Segment of the Sveconorwegian Orogen in southern Sweden, previously dated by ID-TIMS on zircon, have been dated anew using SIMS spot analysis of individual zircon grains, leading to more reliable and in most cases also more precise revised magmatic crystallization ages. A gneissic monzonite within the Protogine Zone in Småland yields a revised U-Pb age of ca. 1725 Ma, four samples of orthogneiss from Skåne all yield revised ages between 1700 and 1690 Ma, while two samples of coarse-grained granitic gneiss in the same region yield ages between 1690 and 1680 Ma. These revised ages are between 15 and 250 m.y. older than previously obtained TIMS ages. Two samples of the Gumlösa-Glimåkra granite along the Protogine Zone in northern Skåne and one sample of related syenite yield ages around 1220 Ma, similar but more precise compared to the previous ages. The U-Pb zircon data have been complemented by Hf isotope analysis by LA-ICP-MS on the same grains, and previously obtained initial Sr and Nd whole-rock isotope data have been recalculated to the revised crystallization ages. The Sr isotope data scatter, while the revised initial ε_Nd values fall between +1 and +2 for the older rocks, and close to 0 for the younger intrusives along the Protogine Zone. Initial ε_Hf in magmatic undisturbed zircons shows relatively little spread within each sample, between 2 and 4 Epsilon units, disregarding a few outliers, with average values for the 1725 to 1680 Ma rocks between +3 and +5.5 and for the 1220 Ma rocks at ca. +1.5. Covariation between initial ε_Nd and initial ε_Hf in the older rocks suggests either mixing between two isotopically distinct magma sources or one magma source which was isotopically heterogeneous. The isotopic signatures of the 1220 Ma intrusive rocks along the Protogine Zone are indicative of juvenile mantle input to their magmas, rather than pure crustal melting.

10.6084/m9.figshare.16750693

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Isotopic composition of ore lead in the Pb-Zn deposits of the Dorotea district, central Swedish Caledonides

Geologiska Foereningan i Stockholm Foerhandlingar (1984)

Peter Schweda Åke Johansson

Abstract Galena in drill core samples from sandstone-lead deposits in the Dorotea district in the Caledonian Front was analysed for its lead isotope composition. Six samples were taken from Bellvikserg and three from the minor deposit of Ormsjö. The composition of all samples was highly radiogenic with 206Pb/204Pb-ratios between 22 and 23, and 207Pb/204Pb-ratios in the range 16.0 to 16.2. Plotted on a207Pb/204Pb versus 206Pb/204Pb diagram, the Dorotea lead follows a linear trend together with lead from Laisvall and Vassbo, suggesting their radiogenic component to be derived from source rocks of Svecokarelian age.

Radiogenic nuclide

Lead (geology)

10.1080/11035898409454602

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Citations (7)