Stratigraphy of the Okhotsk–Chukotka Belt in the Headwaters of the Malyi Anyui River (the Vicinity of Kupol Deposit): U–Pb and 40Ar/39Ar Age Data

Тихомиров, П. Л.; Lebedev, Ivan; Lhuillier, Florian; Павлов, В. Е.

doi:10.1134/s1028334x2112014x

Cited by 4 publications

(13 citation statements)

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“…We conducted an extensive set of API experiments on eight rapidly cooled lava flows from the north‐western part of Chukotka (NE Russia). These flows were accurately dated by the U–Pb method on zircons from adjacent acidic flows (Tikhomirov et al., 2021). The weighted‐mean age of 87.2 ± 1.65 Ma indicates that the investigated lava flows were emplaced at the termination of CNS (121–84 Ma; Ogg, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Age correlation between the sections is difficult due to the absence of reference horizons and significant lateral variability of volcanic complexes. However, the existing U–Pb and 40 Ar/ 39 Ar geochronology data indicate that the emplacement of the investigated sections within the Central Chukotka segment refers to a single pulse of volcanic activity that occurred 90–84 Myr ago (Tikhomirov et al., 2021). Zircons for U–Pb dating were selected from flows 0107 and 0117—the base and roof of section 01; flows 0400 and 0405—the base and middle of section 04 (Figure 1b; Tikhomirov et al., 2021).…”

Section: Settings and Methodsmentioning

confidence: 99%

“…However, the existing U–Pb and 40 Ar/ 39 Ar geochronology data indicate that the emplacement of the investigated sections within the Central Chukotka segment refers to a single pulse of volcanic activity that occurred 90–84 Myr ago (Tikhomirov et al., 2021). Zircons for U–Pb dating were selected from flows 0107 and 0117—the base and roof of section 01; flows 0400 and 0405—the base and middle of section 04 (Figure 1b; Tikhomirov et al., 2021). Therefore, in this paper, due to the complexity of interpolating the available ages, we computed a weighted average age of 87.02 ± 1.65 Ma based on the four U–Pb ages and valid for all studied flows in this area.…”

Section: Settings and Methodsmentioning

confidence: 99%

“…The area of our research is located in the north‐western part of Chukotka (NE Russia) on the border of the Anadyr and Central Chukotka segments of the OCVB (Figure 1a)—the largest marginal continental magmatic province extending for more than 3,000 km along the Pacific margin of Asia (e.g., Akinin & Miller, 2011; Tikhomirov et al., 2012). To the northeast of the Kupol gold deposit (66.9°N, 170.1°E), in the upper reaches of the Malyi Anyui River, we sampled 79 sites from seven distinct sections during two field campaigns in summers 2019 and 2020 (Lebedev et al., 2021; Tikhomirov et al., 2021). Each site was identified to be an independent basaltic flow with horizontal or subhorizontal occurrence (from 0° to 12°) of volcanogenic covers, usually controlled by paleorelief and elements of compensatory immersion structures.…”

Section: Settings and Methodsmentioning

confidence: 99%

“…To the northeast of the Kupol gold deposit (66. 9°N, 170.1°E), in the upper reaches of the Malyi Anyui River, we sampled 79 sites from seven distinct sections during two field campaigns in summers 2019 and 2020 (Lebedev et al, 2021;Tikhomirov et al, 2021). Each site was identified to be an independent basaltic flow with horizontal or subhorizontal occurrence (from 0° to 12°) of volcanogenic covers, usually controlled by paleorelief and elements of compensatory immersion structures.…”

Section: Geology and Samplingmentioning

confidence: 99%

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High‐Latitude Paleointensities During the Cretaceous Normal Superchron From the Okhotsk–Chukotka Volcanic Belt

et al. 2022

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We conducted an absolute paleointensity survey on 74 lava flows from the Okhotsk–Chukotka Volcanic Belt (NE Russia), emplaced 90–83 Ma toward the end of the Cretaceous Normal Superchron (CNS, 121–84 Ma). Relying on preliminary results, we restricted our analysis to eight lava flows (140 Thellier–Coe experiments), two of which also yielded successful Wilson determinations. A detailed analysis of the magneto‐mineralogy—based on X‐ray structural analysis, reflected‐light microscopy, and thermomagnetic curves—indicates that the determinations from solely two lava flows can be fully trusted, with remanence carriers (a) dominated by low‐titanium titanomagnetite, (b) showing unambiguous traces of high‐temperature oxidation, and (c) yielding partial thermoremanent magnetization (pTRM) tails representative of pseudo‐single‐domain grains. Recalculated in terms of geomagnetic dipole strength, our two successful flow‐mean determinations yield virtual dipole moments of 4.76 ± 0.26 × 1022 Am2 (N = 7) and 9.07 ± 0.84 × 1022 Am2 (N = 8). Using an updated version of the paleointensity database for the Cretaceous epoch, we stress that determinations based on nonglassy whole rocks, submarine basaltic glasses, and single crystals are mutually inconsistent, suggesting a separate analysis of their distributions is more appropriate. Despite statistically indistinguishable estimates of dipole strength before and after the onset of the CNS—in accord with recent studies refuting the existence of a strict correlation between chron duration and dipole moment—we found that the distribution of dipole moments during the CNS is slightly bimodal with a leptokurtic dominant mode, thus more inclined to produce outliers and suggesting distinct geomagnetic field behavior during the CNS.

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Section: Discussionmentioning

confidence: 99%

Section: Settings and Methodsmentioning

confidence: 99%

Section: Settings and Methodsmentioning

confidence: 99%

Section: Settings and Methodsmentioning

confidence: 99%

Section: Geology and Samplingmentioning

confidence: 99%

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High‐Latitude Paleointensities During the Cretaceous Normal Superchron From the Okhotsk–Chukotka Volcanic Belt

et al. 2022

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High‐Latitude Geomagnetic Secular Variation at the End of the Cretaceous Normal Superchron Recorded by Volcanic Flows From the Okhotsk‐Chukotka Volcanic Belt

Lhuillier,

Lebedev,

Tikhomirov

et al. 2023

JGR Solid Earth

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The Cretaceous Normal Superchron (CNS, 84–121 Ma) is a singular period of the geodynamo's history, identified by a prolonged absence of polarity reversals. To better characterize the paleosecular variation (PSV) of the geomagnetic field at the end of this interval, we sampled seven continuous sequences of lava flows from the Okhotsk‐Chukotka Volcanic Belt, emplaced 84–89 Ma in the vicinity of the Kupol ore deposit (NE Russia). From a collection of 1,024 paleomagnetic cores out of 82 investigated lava flows, we successfully determined the paleodirections of 78 lava flows, which led to 57 directional groups after removing the serial correlations. The resulting paleomagnetic pole is located at 170.0°E, 76.8°N (A95 = 5.2°, N = 57), in good agreement with previous estimates for north‐eastern Eurasia. Aiming at quantifying PSV at a reconstructed paleolatitude (λ) of ∼80°N, we obtained a virtual geomagnetic pole (VGP) scatter , the value of which was corrected for within‐site dispersion and is little dependent on the choice of the selection criteria. Compared to previous paleodirectional data sets characterizing PSV at various paleolatitudes during the CNS, our Sb estimate confirms a relative latitudinal increase Sb(λ = 90°)/Sb(λ = 0°) on the order of 2–2.5. Focusing on PSV at high paleolatitude within the 70°–90° range, we show that Sb was ∼15% lower at the end of the CNS than during the past 10 Myr, confirming that the singular polarity regime of the geodynamo observed during the CNS is likely accompanied with reduced PSV.

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On the Statistical Accuracy of Paleodirections

Khokhlov,

Gvozdik,

Lebedev

2024

jour

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Stratigraphy of the Okhotsk–Chukotka Belt in the Headwaters of the Malyi Anyui River (the Vicinity of Kupol Deposit): U–Pb and 40Ar/39Ar Age Data

Cited by 4 publications

References 9 publications

High‐Latitude Paleointensities During the Cretaceous Normal Superchron From the Okhotsk–Chukotka Volcanic Belt

High‐Latitude Paleointensities During the Cretaceous Normal Superchron From the Okhotsk–Chukotka Volcanic Belt

High‐Latitude Geomagnetic Secular Variation at the End of the Cretaceous Normal Superchron Recorded by Volcanic Flows From the Okhotsk‐Chukotka Volcanic Belt

On the Statistical Accuracy of Paleodirections

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