Geochemical analysis of bulk sediment and interstitial water of sediment cores from the North-West African continental margin

Molybdenum and vanadium were analysed in 9 scediment cores recovered from the continental slope and rise off NW Africa. Additionall chemical and sedimentological parameters as well as isotope stage boundaries were available for the same core profiles from other investigations.
Molybdenum, ranging between <1 and 10 ppm, occurs in two associateions, either with organic carbon and sulphides in sediments with reducing conditions or with Mn oxides in oxidized near-surface core sections.
Highest values (between 4 and 10 ppm Mo) are found in sulphide-rich core sections deposited during glacial times in a core from 200 m water depth. The possibility of anoxic near-bottom water conditions prevailing at thhis site during certain glacial intervals is discussed.
In oxidized near-surface core sections, the diagenetic mobility of Mo becomes evident from strong Mo enrichment together with Mn oxides (values up to 4 ppm Mo). This enrichment is probably due to coprecipitation and/or adsorption of Mo from interstitial water to the diagenetically forming Mn oxides.
The close relation between Mo and Corg results in strongly covarying sedimentation rates in both components reaching up to 10 times the rates in glacial compared to interglacial core sections.
Vanadium (values between 20 and 100 ppm) does not show clear relations to climate and near-bottom or sediment milieu. It occurs mainly bound to the fine grained terrigenous fraction, associated with aluminium silicates (clay minerals) and iron oxides. Additionally positive covariation of vanadium with phosphorus in most core profiles suggest that some V may be bound to phosphates.

对从西北非近海大陆坡及陆隆采集的9根沉积物岩芯中的钼、钒元素开展了分析。此外，其他研究已针对上述岩芯剖面提供了配套的化学、沉积学参数以及同位素阶段边界数据。
钼元素含量介于<1至10百万分之一（ppm），存在两种赋存组合：一是在还原环境沉积物中与有机碳及硫化物伴生，二是在氧化的近表层岩芯段中与氧化锰（Mn oxides）伴生。
在水深200米的某根岩芯中，冰期沉积的富硫化物岩芯段出现了最高钼含量（4~10 ppm Mo）。本文探讨了该站位在部分冰期时段存在底层水缺氧环境的可能性。
在氧化的近表层岩芯段中，钼的成岩迁移性可通过其与氧化锰的显著富集（钼含量最高可达4 ppm）得到佐证。该富集现象大概率源于孔隙水中的钼通过共沉淀和/或吸附作用结合至成岩作用形成的氧化锰矿物中。
钼与有机碳（Corg）之间存在密切关联，二者的沉积速率呈现极强的协同变化：冰期岩芯段的沉积速率可达间冰期段的10倍之多。
钒元素含量介于20至100 ppm，未表现出与气候、底层水或沉积环境的明确关联。其主要赋存于细粒陆源组分中，与铝硅酸盐（黏土矿物）及氧化铁伴生。此外，多数岩芯剖面中钒与磷呈现正相关关系，表明部分钒可能结合于磷酸盐矿物中。