Gold-Bearing Brown Coal Deposits of the Zeya–Bureya Sedimentary Basin (East Russia): Fundamental Model of Formation

The primary sources and the conditions for the formation of the Paleogene–Neogene coal-bearing deposits in the Zeya–Bureya sedimentary basin were identified and studied with the help of paleogeographic reconstructions and geochemical analyses. Based on the results obtained, we suggest a new basic model of element transfer into the coal, involving two mutually complementary processes to account for the introduction and concentration of gold and other trace elements in the sequences investigated. The first process reflects the system in which peatlands were concentrated along the basin’s junction zone and the passive internal residual mountain ranges. The second reflects the junction’s contrast-type (sharp-type) forms conditions along the external mobile mountain-fold frame. The eroded gold particles were transported over 10–20 km as complex compounds, colloids, dispersed particles, and nanoparticles, and remobilized into clastogenic and dissolved forms along the first few kilometers. The release of gold in the primary sources occurred due to weathering of gold-bearing ore zones, followed by transportation of gold by minor rivers to the areas of peat accumulation. This study considered the probability of the accumulation of high concentrations of gold and rare earth elements (REE) in coal due to the introduction of organic and inorganic materials during floods, with episodes of catastrophic events, and volcano–hydrothermal activities.

Distribution of Cenozoic metalliferous coal deposits in Zeya-Bureya Sedimentary Basin (Eastern Siberia): Tectonic reconstruction and paleogeographic analysis

Distribution of noble metals, rare metals and rare earth elements in the Paleocene and Lower-Middle Miocene coals of Zeya-Bureya sedimentary basin was analyzed. Reconstruction of the basin formation in the Mesozoic and Cenozoic was performed with detailed paleogeographic analysis of the Cenozoic coal-bearing sequences from the position of geodynamic features of the adjacent regions development. Geological events at the turn of the Cretaceous and Paleogene are considered. Comprehensive analysis of the metal content in the basin frame carried out. We described conditions of migration and localization of trace elements. Given conditions arose mainly in the process of geodynamics developed on the northwestern flank of the Zeya-Bureya basin including the static orogens in the Paleocene — Miocene where the sedimentation was actively expanding. Microelements migration with capturing denudation plains occurred in stable processes of peat accumulation and localization of economically important components in streams associated with plains. Contrasting forms of conjugation in the flexure-uplift system and uneven localization of microelements are determined by high level of geodynamic activity on the south-eastern margin of Zeya-Bureya sedimentary basin. The presence of gold throughout the strata of the Paleocene and Lower-Middle Miocen coal-bearing sediments in the Sergeevskoe, Yerkovetskoe and Raychikhinskoe deposits is established. The Sergeevskoe deposit coals are enriched with Be, Sc, V, Ga, Rb, Nb, Ta, REE + Y.