Composition and secondary alterations of microfossils in sediments of the Ashadze-1 hydrothermal field (tropical Mid-Atlantic Ridge) |
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| Authors: | I F Gablina L L Demina O B Dmitrenko N S Os’kina E A Popova T A Khusid V V Shilov |
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| Institution: | 1.Geological Institute,Russian Academy of Sciences,Moscow,Russia;2.Shirshov Institute of Geology,Russian Academy of Sciences,Moscow,Russia;3.Federal State Unitary Enterprise Gramberg All-Russia Research Institute of Geology and Mineral Resources of the World Ocean (VNIIOkeangeologiya),St. Petersburg,Russia;4.Polar Marine Geological-Prospecting Expedition,St. Petersburg,Russia |
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| Abstract: | The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 hydrothermal field in the Mid-Atlantic
Ridge sampled during cruise 26 of the R/V Professor Logachev in 2005 revealed the substantial influence of hydrothermal processes on the preservation of planktonic calcareous organisms,
as well as on the preservation and composition of the benthic foraminifers. From the lateral and vertical distribution patterns
and the secondary alterations of the microfossils, it is inferred that the main phase of the hydrothermal mineralization occurred
in the Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts.
The distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to the hydrothermal
activity. There are three mineral-geochemical zones defined: the sulfide zone, the zone with an elevated Mg content, and zone
of Fe-Mn crusts. |
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