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Biologically mediated crystallization of buddingtonite in the Paleoproterozoic; organic-igneous interactions from the Volyn Pegmatite, Ukraine

Gerhard Franz, Vladimir Khomenko, Aleksei Vishnyevskyy, Richard Wirth, Ulrich Struck, Joerg Nissen, Ulrich Gernert and Alexander Rocholl
Biologically mediated crystallization of buddingtonite in the Paleoproterozoic; organic-igneous interactions from the Volyn Pegmatite, Ukraine
American Mineralogist (October 2017) 102 (10): 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 (+ or -euclase) + F-muscovite (with tobelite component) + buddingtonite + organic matter (OM) + opal (+ traces of K-feldspar, albite, columbite, FeS (sub 2) , barite, REE-minerals). Sector-zoned and platy to fibrous buddingtonite has variable (K+Na)- vs. NH (sub 4) -contents (electron microprobe analyses) and some H (sub 2) O or H (sub 3) O (super +) , 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 (< or =7 at%), Y (< or =3 at%), Sc (< or =0.8 at%), REE (< or =0.3 at%), Th (< or =0.2 at%), and U (< or =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 approximately 100 MPa/150 degrees 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 NH (sub 4) , was then incorporated into buddingtonite.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 102
Serial Issue: 10
Title: Biologically mediated crystallization of buddingtonite in the Paleoproterozoic; organic-igneous interactions from the Volyn Pegmatite, Ukraine
Affiliation: Technische Universitaet Berlin, Fachgebiet Mineralogie-Petrologie, Berlin, Germany
Pages: 2119-2135
Published: 201710
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 59
Accession Number: 2017-090037
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N49°00'00" - N52°00'00", E28°00'00" - E29°00'00"
Secondary Affiliation: Ukrainian Academy of Sciences, Institute of Geochemistry, Mineralogy and Ore Formation, UKR, UkraineGerman Research Centre for Geosciences, DEU, GermanyLeibniz-Institut fuer Evolutions-und Biodiversitaetsforschung, DEU, Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201747
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