Diagenetic alterations of copper sulfides in modern ore-bearing sediments of the Logatchev-1 hydrothermal field (Mid-Atlantic Ridge 14°45′ N)

Authors: Gablina, I.; Semkova, T.; Stepanova, T.; Gor'kova, N.

Source: Lithology and Mineral Resources, Volume 41, Number 1, January 2006 , pp. 27-44(18)

Publisher: MAIK Nauka/Interperiodica

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Abstract:

Sulfide ore samples recovered by corers from and beyond Orebody 1 in the Logatchev-1 hydrothermal field (Mid-Atlantic Ridge, 14°45′ N) are studied by optical, electron microscopic, X-ray microspectral, and X-ray diffraction methods. The major and ore minerals are identified. Sulfides of the Cu-S system, the major ore-forming minerals in sediments, are investigated in detail. Specific features of their composition, structure, secondary alterations, and distribution in sediments of the Logatchev-1 field are considered. It has been established that sulfide concretions in modern sediments primarily consist of nonstoichiometric minerals of the chalcocite-digenite series, i.e., djurleite (Cu_1.96S) and roxbyite (Cu_1.75–1.86S). It is assumed that copper sulfides primarily precipitated from hydrothermal solutions as high-temperature hexagonal chalcocite that was replaced after the hydrothermal activity by djurleite, roxbyite, and other nonstoichiometric minerals of the Cu-S system. Based on the comparison of their paragenetic associations with those of copper sulfides in hydrothermal chimneys, the paper discusses constraints of the diagenetic transformation of sulfides in ore-bearing sediments and the halmyrolysis of modern hydrothermal edifices located in contact with seawater. Roxbyite recently discovered in oceanic sediments plays a specific role in these processes.

Document Type: Research article

DOI: http://dx.doi.org/10.1134/S0024490206010032

Affiliations: 1: Email: gablina@ilran.ru

Publication date: 2006-01-01