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Natalia А. Rumyantseva
Natalia А. Rumyantseva
Engineer of the 1st Category
Academician I.S.Gramberg All-Russia Scientific Research Institute for Geology and Mineral Resources of the Ocean
Engineer of the 1st Category
Academician I.S.Gramberg All-Russia Scientific Research Institute for Geology and Mineral Resources of the Ocean
Saint Petersburg
Russia
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Articles

Geology
  • Date submitted
    2022-04-04
  • Date accepted
    2022-05-18
  • Date published
    2022-07-13

Distribution of trace elements controlled by sector and growth zonings in zircon from a miaskite pegmatite of the Vishnegorsky massif, the Southern Urals

Data on the content and distribution of trace and rare-earth elements (SIMS method) in sectors and growth zones of a large zircon crystal from miaskite pegmatites of the Vishnegogorsky massif are presented. The morphology of the zircon crystal is a combination of a dipyramid {111} and prism {010}. It has been established that the growth sector of dipyramid {111} is characterized by almost one order of magnitude higher contents of Y, Nb, REE, Th; higher Th/U and Eu/Eu* values; REE distribution spectra are flatter compared to prism {010} growth sector. A regular decrease in the content of trace and rare-earth elements in the direction from the central zone to the marginal zone of crystal growth was revealed. A smooth regression of zircon crystallization temperature of zircon from 960 °C in the central zone to 740 °C in the marginal zone of the dipyramid sector and 700-650 °C in the prism sector has been revealed, which may be a reflection of thermal evolution of the crystallization process. It is assumed that crystallization of the central zone of zircon occurred at early stages from a relatively trace-еlement-rich melt. The crystallization was completed at lower temperatures, probably, simultaneously with the formation of REE-concentrating minerals, which resulted in natural decrease of content of trace and rare-earth elements in the melt and, consequently, in zircon crystallizing from it.

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Ekaterina V. Levashova, Vladimir A. Popov, Dmitry S. Levashov, Natalia A. Rumyantseva (2022) Distribution of trace elements controlled by sector and growth zonings in zircon from a miaskite pegmatite of the Vishnegorsky massif, the Southern Urals. Journal of Mining Institute. Vol 254. p. 136-148. DOI: 10.31897/PMI.2022.29
Geology
  • Date submitted
    2020-11-20
  • Date accepted
    2021-03-30
  • Date published
    2021-06-24

Petrochemical features of tholeiites from the Shaka ridge (South Atlantic)

The article presents original data of chemical composition of tholeiitic basaltoids and andesites, dredged from the Shaka Ridge (South Atlantic) in the course of field research in spring 2016 on the scientific expedition vessel “Akademik Fedorov”. The analytical part of the work on estimating the contents of petrogenic, trace and rare-earth elements was carried out using the classical method (“wet chemistry”), X-ray fluorescence analysis (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). The studied samples demonstrate elevated concentrations of large-ion lithophile elements, or LILE, (Ba, Rb, Pb) and light rare earth elements, or LREE, (La, Ce, Nd, Sm) relative to high field strength elements, or HFSE, (Nb, Ta) and heavy rare earth elements, or HREE, (Dy, Yb, Lu). The specifics of trace element geochemistry suggest a significant contribution of crustal or subduction components to the magmas of the Shaka Ridge. Discrimination diagrams of basaltoids and allied rocks with fields of different geodynamic settings indicate that they were formed in the setting of the mid-ocean ridge basalt (MORB). The reason behind the appearance of subduction and crustal marks in the rocks is possibly associated with assimilation of crustal matter by magmas or lies in their inheritance from the mantle source.

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Natalia А. Rumyantseva, Boris G. Vanshteyn, Sergey G. Skublov (2021) Petrochemical features of tholeiites from the Shaka ridge (South Atlantic). Journal of Mining Institute. Vol 248. p. 223-231. DOI: 10.31897/PMI.2021.2.6