New data on the age of the oldest tonalite-trondhjemite association in the Baltic Shield

Chekulaev, V. P.; Arestova, N. A.; Berezhnaya, N. G.; Presnyakov, S. L.

doi:10.1134/s0869593809020105

Cited by 7 publications

(5 citation statements)

References 3 publications

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“…0.97 (average initial  187 Os = +777). Regression of the data using ISOPLOT yields a Model 2 (Ludwig, 2003) age of 3334±710 Ma; this age is consistent with the emplacement age of the tonalites of 3213±32 Ma (Chekulaev et al, 2009). The average initial  187 Os calculated at the time of tonalite emplacement is +304±64 (2SE).…”

Section: Re-os Isotopic Datasupporting

confidence: 64%

“…Geochemically, the tonalites are characterized by high Al 2 O 3 , high Na 2 O/K 2 O, and (La/Yb) N >30 that are similar to other tonalites from the Fennoscandian Shield, such as those from the 3.1 Ga TTG complexes of southeastern Karelia and northern Finland (Jahn et al, 1984), and the 2.85 and 2.65 Ga TTG suite of eastern Finland (Martin et al, 1983). These rocks have T DM Nd model ages of 3288±94 Ma (2SE, N = 9) and a U-Pb SHRIMP zircon age of 3213±32 Ma (Kulikov et al, 1990;Chekulaev et al, 2009).…”

Section: Geological Background Samples and Previous Studiesmentioning

confidence: 54%

“…We also analyzed four representative tonalite samples from the tonalite-trondhjemite-granodiorite (TTG) complex of the Vodla Block in order to assess effects of crustal contamination on the Os, W, Nd, and Hf isotope systematics of the Victoria's lava lake komatiitic basalts. Detailed information on location of the samples, trace element geochemistry, and Sm-Nd and U-Pb zircon chronology for the tonalites can be found in Kulikov et al (1990), Kulikova (1993), Lobach-Zhuchenko et al (1993) and Chekulaev et al (2009). Geochemically, the tonalites are characterized by high Al 2 O 3 , high Na 2 O/K 2 O, and (La/Yb) N >30 that are similar to other tonalites from the Fennoscandian Shield, such as those from the 3.1 Ga TTG complexes of southeastern Karelia and northern Finland (Jahn et al, 1984), and the 2.85 and 2.65 Ga TTG suite of eastern Finland (Martin et al, 1983).…”

Section: Geological Background Samples and Previous Studiesmentioning

confidence: 99%

“…For Re, Pt, and Os abundances of the crustal end member, we used two model compositions, one being the average composition of the Vodla Block tonalites (VBT) from this study and the other being composition of the upper continental crust (UCC) from Peucker-Ehrenbrink and Jahn (2001). As mentioned earlier, the UCC in this part of the Karelian granite-greenstone terrain consists of Vodla Block TTG gneisses with a U-Pb zircon age of ~3.21 Ga (Lobach-Zhuchenko et al, 1993;Chekulaev et al, 2009). Assuming that the UCC in the area was derived from a source with an average BSE 186 Os/ 188 Os = 0.1198304 and 187 Os/ 188 Os = 0.10492 at 3.21 Ga, it had ~800 Ma to evolve from this Os isotopic composition, with its respective Pt/Os and Re/Os ratios, prior to being assimilated by the original Vetreny komatiite magma.…”

Section: Hse Systematics Of the Vetreny Komatiite Mantle Sourcementioning

confidence: 99%

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Lithophile and siderophile element systematics of Earth’s mantle at the Archean–Proterozoic boundary: Evidence from 2.4 Ga komatiites

Puchtel

Touboul

Blichert‐Toft

et al. 2016

Geochimica et Cosmochimica Acta

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New Os isotope and highly siderophile element (HSE) abundance data, in combination with lithophile trace element and Sm-Nd, Lu-Hf, and Hf-W isotope data, are reported for komatiitic basalts from the Vetreny Belt and tonalites from the adjacent Vodla Block in the Fennoscandian Shield. Komatiitic basalts define a Re-Os isochron with an age of 2407±6 Ma and an initial  187 Os = +1.7±0.2 (2SE). The Pt-Os data for chromite separates yield an average initial  186 Os = +0.03±0.02 (2SE). The 147 Sm-143 Nd and 176 Lu-176 Hf data for the komatiitic basalts give isochron ages and initial ratios of, respectively, 2403±32 Ma and  143 Nd = −0.90±0.09, and 2451±79 Ma and  176 Hf = +0.4±0.2 (2SE). Bulk tonalites are characterized by average initial  187 Os,  143 Nd, and  176 Hf values of +304±64, +1.8±0.6, and +2.5±1.6 (2SE), respectively, when calculated for the ~3.21 Ga age of the rocks. The komatiitic basalts and tonalites have  142 Nd values of, respectively, +0.5±2.8 and-0.4±5.2 (2SD). By contrast, both the komatiitic basalts and tonalites exhibit positive 182 W anomalies of +7.1±4.5 and +12.6±4.5 ppm (2SD), respectively. The komatiitic basalts were derived from a komatiitic parental magma with ~27 wt.% MgO; it was modified by both assimilation of the tonalites and fractional crystallization en route to the surface. Lithophile trace element data constrain the degree of crustal contamination to be 4.0±0.4%. Highly siderophile element abundance data indicate that crustal contamination must have had a negligible effect on the Os isotopic compositions of the komatiitic parental magma. By contrast, the Nd, Hf, and W isotope systematics of the komatiitic parental magma were strongly modified as a result of assimilation of the tonalites. The positive initial  143 Nd and  176 Hf values of the tonalites indicate that they formed via melting of a crustal precursor with time-integrated suprachondritic Sm/Nd and Lu/Hf. This precursor was most likely ancient mafic crust. The large positive 182 W anomaly present in the tonalites requires that the precursor crust incorporated a primordial component with Hf/W that became fractionated, relative to the bulk mantle, within the first 50 Ma of Solar System history. The absolute HSE abundances in the mantle source of the Vetreny komatiite system are estimated to be 66±7% of the present-day Bulk Silicate Earth. This observation, coupled with the normal 182 W/ 184 W composition of the komatiitic basalts, when corrected for crustal contamination ( 182 W = −0.5±4.5 ppm), indicates that the W-HSE systematics of the Vetreny komatiite system most likely were established as a result of late accretion of chondritic material to Earth. Our present results, combined with isotopic and chemical data available for other early and late Archean komatiite systems, are inconsistent with the model of increasing HSE abundances in komatiitic sources as a result of slow downward mixing into the mantle of chondritic material accreted to Earth throughout the Archean. The observed HSE concentration variations ...

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Section: Re-os Isotopic Datasupporting

confidence: 64%

Section: Geological Background Samples and Previous Studiesmentioning

confidence: 54%

Section: Geological Background Samples and Previous Studiesmentioning

confidence: 99%

Section: Hse Systematics Of the Vetreny Komatiite Mantle Sourcementioning

confidence: 99%

See 2 more Smart Citations

Lithophile and siderophile element systematics of Earth’s mantle at the Archean–Proterozoic boundary: Evidence from 2.4 Ga komatiites

Puchtel

Touboul

Blichert‐Toft

et al. 2016

Geochimica et Cosmochimica Acta

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“…A significant part of its area is occupied by rocks of the tonalite-trondhjemite-granodiorite (TTG) series. The available U-Pb zircon datings on some of these rocks are ~3.24 Ga [1][2][3], which makes it possible to consider the domain as the "ancient core" of the Bal tic shield [4,5]. The marginal parts of the domain are made up of greenstone belts consisting mainly of meta morphosed komatiite-basaltic volcanics.…”

mentioning

confidence: 99%