Microfossils and chemical elements in bottom sediments of the Ashadze-1 Hydrothermal Field (tropical Mid-Atlantic Ridge)

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 R/V Professor Logachev in 2005 revealed substantial influence of hydrothermal processes on preservation of planktonic calcareous organisms as well as on preservation and composition of benthic foraminifera. From lateral and vertical distribution patterns and secondary alterations of microfossils it is inferred that the main phase of hydrothermal mineralization occurred in Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts. Distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to hydrothermal activity. There are three mineral-geochemical zones defined: sulfide zone, zone with elevated Mg content, and zone of Fe-Mn crusts.

2005年通过“罗加乔夫教授号”（R/V Professor Logachev）第26航次在大西洋中脊Ashadze-1热液田采集的含矿沉积物中的微体化石的首次全面分析，揭示了热液作用对浮游钙质生物体保存，以及底栖有孔虫的保存状况与群落组成的显著影响。基于微体化石的侧向与垂向分布模式及其次生蚀变特征，研究人员推断热液成矿的主阶段发生于全新世（Holocene）。重金属（铜Cu、钴Co、铬Cr与银Ag）在有孔虫壳体及其包裹的铁锰结壳中富集。置换有孔虫壳体的自生矿物的分布特征展现出与热液活动相关的局部分带性。现已划定三类矿物-地球化学分区：硫化物带、镁含量升高带以及铁锰结壳带。