DBPapers
DOI: 10.5593/sgem2017/11/S01.046

NATIVE GOLD PARAGENESIS WITH BISMUTH AND TELLURIUM MINERALS IN SUBPOLAR URAL PLACERS (RUSSIA)

T. Mayorova, S. Kuznetsov
Saturday 9 September 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7105-98-8 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 11, 359-366 pp, DOI: 10.5593/sgem2017/11/S01.046

ABSTRACT

In the placers of the south-eastern boundary of the Lyapin megaanticlinorium at the Subpolar Urals for the first time the relation of native gold with bismuth and telluride minerals was reliably established. The placer area is located within the Lower Proterozoic and Riphean metamorphic rocks. Directly in the placers Bi-tellurosulphides, tellurides and sulphosalts (tetradimite, joseite-B, joseite-A, tsumoite, hedleyite, cosalite), native bismuth, native silver, maldonite are determined together with gold in large quantities. Nodules of tetradimite, joseite-B, native bismuth have size from 1 to 2-8 mm. Tsumoite forms inclusions in tetradimite, hedleyite – in gold, joseite-B, garnet and ilmenite. The crystals of cosalite and cobaltine (glaucodote) have size to 1 mm. The increased content of cassiterite, wolframite and galena is present, grains of arsenopyrite are rare. Intergrowths of gold with quartz, tetradimite, joseite-B, hedleyite, iron oxides, ilmenite and hematite are present. These minerals indicate here the presence of a new type of mineralization – gold-telluride-bismuth (with Sn and W). Probable sources of Au-Te-Bi minerals in the placers are occurrences of low sulphide Au-quartz formation, Au-polymetallic, skarn or porphyry occurrences. The indicator of minimal upper limit of Au-Te-Bi formation temperature can be the thermal interval of maldonite stability (371–116°C). However it is not excluded that the Au-Te-Bi mineralization is also present in the Au-polymetallic and Au-sulphide occurrences as one of the stages of mineral formation. The isotope composition of sulfur of galena (ẟ...⁴S 7.2-8.4 ‰) from the placer indicates assimilation of sulfur from the enclosing rocks.

Keywords: gold, Bi-Te minerals, placers, indigenous sources, Subpolar Urals

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