Organic matter and formation of buddingtonite - an example of organic-igneous interaction from Volyn pegmatite, Ukraine

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Marco E. Ciriotti
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Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Organic matter and formation of buddingtonite - an example of organic-igneous interaction from Volyn pegmatite, Ukraine

Messaggio da Marco E. Ciriotti » gio 22 giu, 2017 10:20

Prossima pubblicazione.

Referenza:
▪ Franz, G., Khomenko, V., Vishnyevskyy, A., Wirth, R., Struck, U., Nissen, J., Gernert, U., Rocholl, A. (2017): Organic matter and formation of buddingtonite - an example of organic-igneous interaction from the Paleoproterozoic Volyn pegmatite, Ukraine. American Mineralogist, 102, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 23532
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Organic matter and formation of buddingtonite - an example of organic-igneous interaction from Volyn, Ukraine

Messaggio da Marco E. Ciriotti » lun 02 ott, 2017 15:49

Pubblicazione effettuata.

Referenza:
▪ Franz, G., Khomenko, V., Vishnyevskyy, A., Wirth, R., Struck, U., Nissen, J., Gernert, U., Rocholl, A. (2017): Organic matter and formation of buddingtonite - an example of organic-igneous interaction from the Paleoproterozoic Volyn pegmatite, Ukraine. American Mineralogist, 102, 2119-2135.

Abstract:
The Volyn pegmatites from Volodarsk-Volynskyi in the Zhytomyr Oblast, NW Ukraine, are associated with granites genetically related to the Paleoproterozoic Korosten pluton. Their late-stage evolution is characterized by the formation of opal-cemented breccia. A polymineralic pseudomorph after beryl within the breccia includes bertrandite (±euclase) + F-muscovite (with tobelite component) + buddingtonite + organic matter (OM) + opal (+ traces of K-feldspar, albite, columbite, FeS2, barite, REE-minerals). Sector-zoned and platy to fibrous buddingtonite has variable (K+Na)- vs. NH4-contents (electron microprobe analyses) and some H2O or H3O+, as indicated by microscope infrared spectroscopy. We suggest that ammonium was produced by decay of OM, which is partly preserved in the pseudomorph. Energy-dispersive electron microprobe data of the OM show with increasing O–decreasing C-N-content due to degassing; the OM contains the high field strength elements Zr (≤7 at%), Y (≤3 at%), Sc (≤0.8 at%), REE (≤0.3 at%), Th (≤0.2 at%), and U (≤1.25 at%), which increase with increasing O-content. Transmission electron microscopy of the OM confirms the presence of N; Zr, Si, and O (with other HFSE) are concentrated in nanometer-sized areas and at the transition from OM to opal in nanometer-sized platy Zr-Si-O crystals. C-rich areas are amorphous but show poorly developed lattice fringes. OM is present in the pseudomorph also as brown pigmentation of opal and in pegmatitic beryl from Volyn as a component in late stage fluid inclusions, identified by C-H vibrational bands in infrared spectra. Stable isotope investigations of C and N of buddingtonite, black opal and kerite (fibrous OM known from the literature to occur in the Volyn pegmatites and interpreted as microfossils) indicate a biogenic origin of the OM. We propose that OM in the pseudomorph is condensed kerite, which achieved the high concentrations of high field strength elements via fluid-pegmatite interaction. Although no age determination of minerals in the pseudomorph is available, textural arguments and phase equilibria indicate its formation in a late stage of the pegmatite evolution, at P-T conditions below ~100 MPa/150 °C. We favor a conceptual model for the formation of the Volyn buddingtonite in analogy to Phanerozoic occurrences of buddingtonite, where over and around the shallow anorthosite-granite Korosten pluton hydrothermal convection cells introduced N-bearing hydrocarbons and its precursors into the cooling igneous rocks. Due to the elevated temperature, the OM disintegrated into degassing volatile and non-volatile residual components analogous to petroleum maturation. Organic N, released as NH4, was then incorporated into buddingtonite.
Marco E. Ciriotti

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