Sources Of Sedimentary Matter Research Articles

Geochemical characteristics and detrital zircon U-Pb ages of the Yimin Formation, Kelulun Depression, Hailar Basin and constraints on uranium mineralization.

The sandstone uranium deposits in the Kelulun Depression are the first commercially viable uranium deposits discovered in the Hailar Basin and the ore-bearing strata corresponding to the Lower Cretaceous Yimin Formation. However, the source of sedimentary matter, uranium source conditions, and uranium mineralization processes in the region have not been characterized. Accordingly, we analyzed the lithology, whole-rock geochemistry, zircon U-Pb ages, and trace elements of the Yimin Formation sandstones. The Yimin Formation sandstones were primarily composed of detrital grains with low compositional maturity. A geochemical analysis indicated that the parent rocks are felsic igneous rocks formed at an active continental margin with a moderately high degree of weathering. The detrital zircon U-Pb ages of the Yimin Formation 215-287 Ma with a peak at 230-260 Ma. Based on chronological, geochemical, and lithological data, we conclude that the Yimin Formation matter is derived from the Adunchulu Uplift on the western side of the Kelulun Depression and its parent rocks are Triassic granites. The Adunchulu uplift since the late Early Cretaceous and weathering and denudation of its uranium-rich granites provided ample matter and uranium. Therefore, the Kelulun Depression is a promising area for the exploration of sandstone uranium deposits.

ПРОСТРАНСТВЕННЫЕ ЗАКОНОМЕРНОСТИ НАКОПЛЕНИЯ УГЛЕРОДА В ОЗ. ПЕСЧАНОЕ (ЮГ ЗАПАДНОЙ СИБИРИ) В ГОЛОЦЕНЕ

The paper is devoted to the study of the processes of Lake Peshchanoye, located on the territory of the Baraba Lowland (south of West Siberia). By the means of a set of analytical methods, the structure and composition of sapropelic accumulation were characterized and sources of sedimentary matter were identified. The main material source is an autochthonous sedimentary material (organic matter, authigenic minerals). Organic matter has a predominantly planktonic origin with a predominance of phytoplankton. Authigenic minerals are represented by framboid aggregates of pyrite, curdled precipitates of low-magnesian calcite intergrown with remains of biota mortmass and biogenic amorphous silica, the content of which is equal to 60% of the total silica in sapropel. The allochthonous part is represented by terrigenous particles of quartzfeldspar composition. The predominance of allochthonous material over autochthonous one was revealed in the northern part of the lake, it is associated with an input of terrigenous particles by the river. The main forms of carbon burial are undecomposed organic matter and authigenic carbonates. The estimated total carbon reserves in the lake are 113.21 thousand tons.

Atmospheric aerosols and sedimentation in arid zones of the Atlantic Ocean

The study of atmospheric aerosols over oceans is one of the new priority fields in the investigation of sedimentation in the oceans. Atmospheric transport of sedimentary particles suspended in the air is a link between the sources of matter transport from land, the ocean surface (substance mobilization zone), and bottom sediments [1‐3 and others]. Aeolian transport is especially important as a source of sedimentary matter in arid zones, where river discharge is minimal, especially in the ocean regions located far from the continents. Deserts, semideserts, and savannas in Africa are the main sources of aerosols in the Atlantic. A large number of publications is dedicated to the study of the main regions of outflow and pathways of transport of the African dust to the ocean observed by means of satellite images, calculation of inverse trajectories, identification of minerals and tracer elements, and so on [1‐5 and others]. However, publications estimating the specific contribution of aerosols to the composition of suspended particulate matter (SPM) in the ocean are quite rare. Most such works are dedicated to comparison of aerosol and matter fluxes collected by sedimentation traps in the water column [5 and others]. However, we did not find any publications devoted to comparison of the atmospheric aerosol and oceanic SPM samples taken simultaneously and processed using the same methods.

Geochemical history of South Atlantic Ocean sediments since Late Cretaceous

202 sediment samples recovered by “Glomar Challenger” in the South Atlantic Ocean have been analyzed for Si, Al, Ti, Fe, Mn and P, showing that the basal sediments far from the crest of the ridge are relatively rich in Fe, Mn and P, and poor in Si, Al and Ti. The results suggest that submarine ridge volcanism has been a source of sedimentary matter at least since the Eocene, possibly since the Late Cretaceous. The post-depositional rearrangement or migration of manganese is insignificant; most of it has remained in situ.