212
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
1988). Heavy REE concentrations of Vilyuy and Aldan SPM were similar to the Chara while
light REE concentrations were significantly lower. In addition, Vilyuy SPM was characterized
by a positive Eu anomaly. The catchment of the upper Vilyuy consists of basaltic rocks of the
Siberian Trap. Due to the magmatic fractionation of Ca-rich feldspars, the upper continental
crust and average shale are characterized by a negative Eu anomaly relative to the primitive earth
mantle or chondrite, respectively. Continental flood basalts, on the other hand, do not exhibit
this pronounced Eu anomaly since they are less fractionated. Therefore, the average shalenormalized REE patterns of material derived from basaltic rocks display a positive Eu anomaly.
The SPM of the Vilyuy reflected the REE composition of the Trap basalts. Since the Khatanga
almost exclusively drains the Siberian Trap, a detailed discussion of the major, trace, and REE
composition of the basalt is given in the Khatanga chapter. Summarizing, it can be concluded
that REE patterns of the Lena tributaries clearly reflect the geology of their corresponding
catchments. The Lena integrates the SPM derived from different lithologies and imported via
tributaries. For this reason, the average REE pattern of the Lena cannot be distinguished from
other major rivers.
Yana SPM
In general, the Yana was characterized by the highest total SPM concentrations observed in the
studied rivers, ranging from 57 to 750 mg/l and averaging 285 mg/l. Consequently, the SPM of
the Yana contained higher amounts of comparatively coarse-grained material (upper left corner
of Figure 6). Due to the frequent occurrence of silt-sized particles, the SPM consisted mainly of
quartz and feldspars. Plagioclase and K-feldspars could be identified. The clay minerals chlorite
and illite were observed; smectite and mixed-layer minerals did not occur (Table 2). However,
in comparison to the other rivers studied, the clay minerals were less abundant.
The chemical composition of SPM of the Yana and its tributaries exhibited the most
pronounced variations observed in this study. On the one hand, these variations must be
attributed to the heterogeneity of the catchment, and on the other hand, to the abundance of
coarse-grained material. The average AI-normalized major and trace element concentrations of
Yana SPM in comparison to average shale (Wedepohl, 1971 and 1991) are presented in Figure
6. In contrast to average Lena SPM, the AI-normalized concentrations of several elements differ
from average shale. In particular, As, Ba, Bi, Cd, Cs, Na, Sb, W, Zn, and Zr are characterized
by higher, and Ca and Sr by lower, AI-normalized concentrations. In order to explain the
deviations, several processes must be considered.
(1) As with the Lena, Cd and Zn may be enriched due to adsorption onto organic material.
However, since the grain-size distribution of Yana SPM was displaced towards coarser
material, the enrichment is less pronounced.
(2) The enrichment in Zr in Yana SPM may be related to the dominance of silt-sized particles.
The mineral zircon is strongly enriched in this fraction as can be seen from the high Zr
concentrations in loess (Schnetger, 1992). Zr and Hf concentrations in the bedload are
consequently significantly higher than in the suspended load (Dupre et aI., 1996), as they are,
for example, in the Congo river.
(3) Low CaJAI, Sr/AI, and high NaJAI ratios must be attributed to the lithology of the drainage
basin, which consists mainly of Mesozoic terrigenous sediments and volcanic rocks as well as
granitic intrusions of Triassic and Jurassic age. As for the Lena, high BaJ AI ratios can be
explained by the occurrence of feldspar.
(4) Pronounced enrichments in As, Bi, Cs, Sb, and W indicate the influence of ore deposits
in the Yana basin. Au and Sn ore deposits originating from granitic intrusions are a typical
feature of the Yana basin (Efremenko, 1976). The source rocks consist of granite and
granodiorite, tourmaline granite, and aplite. They exhibit very high concentrations of As (up to
Land-Ocean Systems in the Siberian Arctic: Dynamics and History
1988). Heavy REE concentrations of Vilyuy and Aldan SPM were similar to the Chara while
light REE concentrations were significantly lower. In addition, Vilyuy SPM was characterized
by a positive Eu anomaly. The catchment of the upper Vilyuy consists of basaltic rocks of the
Siberian Trap. Due to the magmatic fractionation of Ca-rich feldspars, the upper continental
crust and average shale are characterized by a negative Eu anomaly relative to the primitive earth
mantle or chondrite, respectively. Continental flood basalts, on the other hand, do not exhibit
this pronounced Eu anomaly since they are less fractionated. Therefore, the average shalenormalized REE patterns of material derived from basaltic rocks display a positive Eu anomaly.
The SPM of the Vilyuy reflected the REE composition of the Trap basalts. Since the Khatanga
almost exclusively drains the Siberian Trap, a detailed discussion of the major, trace, and REE
composition of the basalt is given in the Khatanga chapter. Summarizing, it can be concluded
that REE patterns of the Lena tributaries clearly reflect the geology of their corresponding
catchments. The Lena integrates the SPM derived from different lithologies and imported via
tributaries. For this reason, the average REE pattern of the Lena cannot be distinguished from
other major rivers.
Yana SPM
In general, the Yana was characterized by the highest total SPM concentrations observed in the
studied rivers, ranging from 57 to 750 mg/l and averaging 285 mg/l. Consequently, the SPM of
the Yana contained higher amounts of comparatively coarse-grained material (upper left corner
of Figure 6). Due to the frequent occurrence of silt-sized particles, the SPM consisted mainly of
quartz and feldspars. Plagioclase and K-feldspars could be identified. The clay minerals chlorite
and illite were observed; smectite and mixed-layer minerals did not occur (Table 2). However,
in comparison to the other rivers studied, the clay minerals were less abundant.
The chemical composition of SPM of the Yana and its tributaries exhibited the most
pronounced variations observed in this study. On the one hand, these variations must be
attributed to the heterogeneity of the catchment, and on the other hand, to the abundance of
coarse-grained material. The average AI-normalized major and trace element concentrations of
Yana SPM in comparison to average shale (Wedepohl, 1971 and 1991) are presented in Figure
6. In contrast to average Lena SPM, the AI-normalized concentrations of several elements differ
from average shale. In particular, As, Ba, Bi, Cd, Cs, Na, Sb, W, Zn, and Zr are characterized
by higher, and Ca and Sr by lower, AI-normalized concentrations. In order to explain the
deviations, several processes must be considered.
(1) As with the Lena, Cd and Zn may be enriched due to adsorption onto organic material.
However, since the grain-size distribution of Yana SPM was displaced towards coarser
material, the enrichment is less pronounced.
(2) The enrichment in Zr in Yana SPM may be related to the dominance of silt-sized particles.
The mineral zircon is strongly enriched in this fraction as can be seen from the high Zr
concentrations in loess (Schnetger, 1992). Zr and Hf concentrations in the bedload are
consequently significantly higher than in the suspended load (Dupre et aI., 1996), as they are,
for example, in the Congo river.
(3) Low CaJAI, Sr/AI, and high NaJAI ratios must be attributed to the lithology of the drainage
basin, which consists mainly of Mesozoic terrigenous sediments and volcanic rocks as well as
granitic intrusions of Triassic and Jurassic age. As for the Lena, high BaJ AI ratios can be
explained by the occurrence of feldspar.
(4) Pronounced enrichments in As, Bi, Cs, Sb, and W indicate the influence of ore deposits
in the Yana basin. Au and Sn ore deposits originating from granitic intrusions are a typical
feature of the Yana basin (Efremenko, 1976). The source rocks consist of granite and
granodiorite, tourmaline granite, and aplite. They exhibit very high concentrations of As (up to