Comparative characterisation of forest litter on sod-podzolic soils of Forest Experimental Dacha in RSAU–MAA named after K.A. Timiryazev

Forest litter under linden and pine forests was studied at the Forest Experimental Dacha of the RSAU–MAA named after K.A. Timiryazev. Despite significant differences in physical and chemical parameters between the litter formed under the conditions of different forest communities, the properties of sod-podzolic soils formed under both vegetation types are quite similar. The litter under linden forest has higher ash content, it is less acidic and contains almost 2 times more exchangeable bases, the content of hydrogen and nitrogen is higher by 0.82 wt% and 0.66 wt%, respectively. The litter of linden and pine forests, according to the atomic ratios H : C, C : N and the degree of oxidation, are equal to 1.82, 30.3, -0.92 and 1.64, 45.7, -0.71, respectively; the litter of linden forests differs from litter of pine forests in the higher content of aliphatic, nitrogen-rich, reduced organic compounds. In the litter of linden forests concentration coefficients of phosphorus and magnesium 1.2 times higher; of carbon, potassium and aluminium – 1.3 times higher; of calcium – 1.4 times higher; of nitrogen – 1.8 times higher, and of silicon – 3 times higher, than in the litter of pine trees. However, the concentration factor of manganese in the pine forest litter is 1.9 times higher compared to the litter of linden. According to the results of UV spectroscopy, water-soluble organic matter of pine forest litter, unlike water-soluble organic matter of linden forest litter, is more enriched by components of aromatic origin. This is evidenced by higher values of SUVA254 and lower values of coefficients E2/E3 and E4/E6

(Table 2) Representative major and trace element analyses of diabase dikes of ODP Hole 140-504B

Hole 504B is located in Panama Basin approximately 200 km south of the Costa Rica Rift within a tectonically undisturbed oceanic crust formed at the Costa Rica Rift spreading center. The hole was drilled in several Deep Sea Drilling Project (DSDP)/Ocean Drilling Program (ODP) legs, including ODP Leg 140. The 378.9 m of core drilled at Hole 504B during Leg 140 continues the dike complex recovered previously during DSDP Leg 83. All the rocks drilled during Leg 140 are fragments of variably metamorphosed dikes composed of olivine-plagioclase-clinopyroxene-, olivine-plagioclase-, and olivine-plagioclase-clinopyroxene-spinel-bearing basalts. We report results of determination of rare earth elements (REE) and large-ion lithophile (LIL) elements in 28 representative samples from the major units of the Hole 504B dike complex. Analyzed samples display relatively uniform REE patterns with only a slight difference in the extent of light REE depletion. LIL elements show large variations independent from other incompatible (Zr and Y), compatible (Cr, Ni, Co), and rare earth elements. Observed REE variations indicate that metamorphism has changed LIL distribution, but has not affected REE patterns. Variable REE depletions are believed to represent original magmatic characteristics of the Costa Rica Rift oceanic crust. LIL distribution favors Ba redistribution due to the fluid-rock interaction in the lower oceanic crust. REE systematics define various degree of depletion in Leg 140 diabase dikes consistent with their derivation from a variably depleted MORB-type source

GEOCHEMICAL PECULIARITIES OF TOP PEAT IN MIDDLE TAIGA OF THE PRE-OB REGION

The top peat in middle taiga of the Pre-Ob region represents a highly negative geochemical anomaly of several chemical elements as compared to that in southern taiga located in the middle and upper parts of this region. Obviously, due to close location of mountain systems (Altai, Salair ridge, Kuznetsk Alatau) and the aerial dust transfer the top peat in southern taiga is enriched with the major metals; this process is unachievable for the remote middle part of the Pre-Ob region