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The Tajno ultramafic-alkaline-carbonatite massif, NE Poland : a review. Geophysics, petrology, geochronology and isotopic signature

Wiszniewska Janina, Petecki Zdzisław, Krzemińska Ewa, Grabarczyk Anna, Demaiffe Daniel

Geological Quarterly

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2020

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Vol. 64, No. 2

402--421

EN

This paper reviews all available geological data on the Tajno Massif that intruded the Paleoproterozoic crystalline basement of NE Poland (Mazowsze Domain) north of the Teisseyre-Tornquist Zone, on the East European Craton. This massif (and the nearby Ełk and Pisz intrusions) occurs beneath a thick Mesozoic-Cenozoic sedimentary cover. It has first been recognized by geophysical (magnetic and gravity) investigations, then by drilling (12 boreholes down to 1800 m). The main rock types identified (clinopyroxenites, syenites, carbonatites cut by later multiphase volcanic/subvolcanic dykes) allow characterizing this massif as a differentiated ultramafic, alkaline and carbonatite complex, quite comparable to the numerous massifs of the Late Devonian Kola Province of NW Russia. Recent geochronological data (U-Pb on zircon from an albitite and Re-Os on pyrrhotite from a carbonatite) indicate that the massif was emplaced at ~348 Ma (Early Carboniferous). All the rocks, but more specifically the carbonatites, are enriched in Sr, Ba and LREE, like many carbonatites worldwide, but depleted in high field strength elements (Ti, Nb, Ta, Zr). The initial87Sr/86Sr (0.70370 to 0.70380) and ɛNd(t) (+3.3 to +0.7) isotopic compositions of carbonatites plot in the depleted quadrant of the Nd-Sr diagram, close to the “FOcal ZOne” deep mantle domain. The Pb isotopic data (206Pb/204Pb <18.50) do not point to an HIMU (high U/Pb) source. The ranges of C and O stable isotopic compositions of the carbonatites are quite large; some data plot in (or close to) the “Primary Igneous Carbonatite” box, while others extend to much higher, typically crustal ẟ18O and ẟ13C values.

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Nowe doniesienia z wnętrza Ziemi

Grabarczyk Anna, Wiszniewska Janina, Ruszkowski Michał

Przegląd Geologiczny

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2019

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Vol. 67, nr 10

812--816

EN

A new research has been done on the high pressure minerals from the Earth’s Mantle Transition and Lower Zone. The Earth’s Mantle extends from the “Moho” (Mohoroviè) discontinuity down to a depth of 2,900 km and constitutes 83% of the Earth’s volume and 67% of its mass.The mantle is further divided into two seismic regions: the upper and thelower mantle separated by a seismic zone of discontinuity at a depth of 670 km, which is also the maximum depth to which subducted lithospheric plates can reach. The additional discontinuity zone, i.e. a depth of 410 km together with a zone of 670 km, corresponds to the transformation site of the silicate mineral structure, which also affects the speed of propagation of seismic waves. Mantle peridotite samples indicate that olivine is the main component of the uppermost part of the upper mantle, up to adepth of 410 km. At greater depths, down to 660 km, in the so-called Transition, transformation of olivine into its high-pressure poly-morphs (wadsleyite and ringwoodite) showing a spinel structure, is observed. Experimental research data on natural bridgmanite((Mg, Fe)SiO3), which exhibits a perovskite structure and is the main mineral of the lower mantle and the most common mineral in the Earth, have been presented. The problem of nitrogen and water amounts in the Earth’s lower mantle and a content of new iron polymorphs in the Earth’s core have also been discussed.

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Comparative geochemical assessment of jotunite rocks from the Suwałki Massif and the Sejny Intrusion (NE Poland)

Grabarczyk Anna, Wiszniewska Janina

Acta Geologica Polonica

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2019

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Vol. 69, no. 4

513--529

EN

Jotunites (hypersthene monzodiorites/ferromonzodiorites) are rocks coeval with plutonic AMCG (anorthosite– mangerite–charnockite–rapakivi granite) suites, which are characteristic of the Proterozoic Eon. It has been experimentally shown that jotunite magma can be recognised as parental to anorthosites and related rocks: since then, research on these rocks has taken on a particular importance. Jotunites were recently described within the deeply buried c. 1.5 Ga Suwałki and Sejny anorthosite massifs in the crystalline basement of NE Poland. The major and trace element compositions of Polish jotunites show them to have a calc-alkalic to alkali-calcic and ferroan character, with a relatively wide range of SiO2 content (40.56 wt. % up to 47.46 wt. %) and high concentrations of Fe (up to 22.63 wt. % Fe2O3), Ti (up to 4.34 wt. % TiO2) and P (up to 1.46 wt. % P2O5). Slight differences in textural features, mineralogical compositions, and geochemistry of whole-rock jotunite samples from distinct massifs allow us to distinguish two kinds: a primitive one, present in the Sejny Intrusion, and a more evolved one, related to the Suwałki Massif.