Lithology and Mineral Resources最新文献

The article presents the results of experimental studies of the sorption and desorption of rare-earth metal (REM) cations by the Co-bearing ferromanganese crusts of the Govorov Guyot. It has been established that the REM cations are sorbed on the CFC ore minerals (Fe-vernadite, vernadite, Mn-feroxyhite, and goethite. The crusts are characterized by high exchange capacity (1.78–3.57 mg-equiv/g, which increases in the following series: (Dy < Gd < Lu < Sm < Nd < Y, La < Eu) ( ll ) Ce. The REM cation sorption proceeds by the irreversible ion-exchange equivalent mechanism. The exchange complex of ore minerals consists of Na⁺, K⁺, Ca²⁺, and Mg²⁺ cations, which contribute 97‒98% to their total capacity. The crusts are characterized by the group sorption of REM cations from multicomponent water solutions of metal salts. The selectivity of manganese and ferruginous minerals of crusts to REM cations is significantly higher than to the main cations of ocean water. Experimental data on the desorption of sorbed REM cations with the NaCl solution suggest their irreversible sorption by ore minerals and strengthening of the chemical bond of sorbed REM cations with the main structural elements of these minerals over time. An important property of ore minerals, primarily manganese minerals, is their chemical and structural stability in aqueous electrolyte solutions, suggesting the repeated use of FMC as sorbents of REM cations.

The results of regional studies of Early Miocene deposits in Western Ciscaucasia, based on the seismic stratigraphic analysis, are presented. The spatial pattern of sediment accumulation is analyzed and the paleogeographic conditions during the Late Miocene regressive stages in Western Ciscaucasia are refined. Erosional incisions of several levels, developed during the base-level fall in the course of major regressions in the studied time interval, were identified. Based on the spatial correlation of paleoincisions using a chosen series of intersecting seismic profiles, the buried Paleo-Don and Paleo-Donets river valleys were reconstructed at the Sarmatian‒Meotian boundaries and within the Meotian‒upper Pontian interval.

This paper completes the examination of results of the study of lithogeochemical characteristics of a pilot collection of the Riphean–Vendian sandstones, siltstones, and claystones (last one based on the interpretation of results) in Belarus. Data on the age of detrital zircon published in recent years suggest that Upper Precambrian rocks of this region were sourced from the Osnitsk–Mikashevichi and the Trans-Scandinavian igneous belts, the Volyn–Brest large igneous province, rapakivi granites, as well as various rock associations of Sarmatia, Danopolonian orogen and Svecofennides. Based on the lithogeochemical characteristics, the distribution of data points of the studied clastic rocks on discriminant diagrams provides insight into the possible provenance, paleogeodynamic, paleogeographic, and paleoclimatic settings and suggests several conclusions. The considered Riphean–Vendian stratons in Belarus are composed mainly of erosion products of within-plate granitoids, as well as various island-arc and syncollisional felsic igneous rocks. The share of erosion products of mafic rocks among them generally does not exceed 30%. It is significant mainly in the Volyn Group rocks (erosion products of the Volyn–Brest large igneous province), as well as in some samples of the Nizov, Selyavy, and Kotlin formations (fragments of mafic rocks from other provenances?). The source-to-sink transport was accomplished mainly by large rivers. Paleogeodynamic settings varied from quite active to quite passive. The paleoclimate in catchment areas was most likely arid/semiarid in the Riphean. In the Vendian, it was humid and varied from subtropical in the Early Vendian (except the Glusk Formation) to tropical in the Late Vendian. The obtained results also make it possible to show some peculiarities of the known methods and techniques of paleoclimate reconstruction.

The article presents a comparative analysis of the Paleozoic and Cenozoic reef formation, mainly in terms of the position of reefs in the basins of continental and oceanic blocks. It is shown that the main formation of reefs took place in the Cenozoic directly in the oceans, including boundaries between oceans and continents, and, to an extremely limited scales, in the basins of the continental segment. In the Paleozoic, reefs were formed not only in oceans, but also in spacious basins of continental block. This is one of the manifestations of the general evolution of carbonate accumulation, when the Paleozoic carbonate sediments were formed in such shallow-water bodies that covered very significant surfaces of continents.

At the current level of research, a generalization of previously studied and new lithological-mineralogical, structural, and crystal-chemical characteristics of globular layer silicates (GLS) of the Mg-rich glauconite–illite series from Upper Proterozoic sections of eastern and northern Siberia (Uchur–Maya region, Anabar uplift) has been carried out. The classification of glauconite–illite minerals was carried out in accordance with recommendations of the International Nomenclature Committees for Mica and Clay Minerals, as well as based on the available literature and our own data. The Al index, i.e., (K_Al = ^VIAl/[^VIFe³⁺ + ^VIAl]), in minerals of the glauconite–illite series varies from 0.40 to 0.85; the content of Mg and K cations varies, respectively, from 0.51 to 0.75 and from 0.63 to 0.80 f.u. Application of the X-ray modeling method for diffraction patterns of the oriented and unoriented specimens of Upper Proterozoic GLS made it possible to determine the following properties: the content of swelling layers (4–10%), their types (mica, smectite, chlorite), the nature of the alternation (short-range order factor, R = 0), unit cell parameters c sin β, c cos β/a, and average value of parameter b (9.018–9.074 Å). The conditions of glauconite formation in the Upper Proterozoic basins are considered, and their influence on the structural and crystal-chemical features of Mg presence in hydrocarbons is discussed.

Rare earth elements (REE) of the host rocks (Fe-siliceous rocks) and manganese ores of the Nchwaning Mine (Hotazel Formation, Kalahari manganese field) were studied. An important feature of manganese ores and host rocks (Fe-silicites) is the presence of negative and positive cerium (Ce/Ce*) and europium (Eu/Eu*) anomalies. This testifies to the complex and long history of the formation of manganese ores. Initial metal-bearing (Mn, Fe) sediments of a shallow-water basin with a negative cerium anomaly (Ce/Ce*) were enriched in europium (positive Eu/Eu*) at different stages of lithogenesis both during sedimentation (underwater discharge of hydrothermal fluids), and subsequent processes of hydrothermal transformation of the ore-bearing strata. The source of manganese could be basaltic andesites of the underlying Ongeluk Formation.

The results of studies of a basaltic andesite sample (complicated by the mineralized fracture and voids, as well as fracture and gas voids filled with secondary mineralization) dredged on the submarine Esmeralda Volcano are presented. A detailed comparative study of the mineral composition of the substance lining the fracture, the near-fracture space, and the basaltic andesite part unaffected by secondary alterations made it possible to discover the presence of a mineral assemblage, which is atypical for the unaltered volcanic rocks, in the submarine Esmeralda Volcano. In the intra-fracture space and adjacent basaltic andesite zones, wide variation ranges of the plagioclase composition are recorded; isomorphism in the Fe–Ca pyroxene series is studied; REE oxides, hydroxides, and fluorohydroxides are studied; and variability in the composition of minerals of the magnetite–hematite series is shown. Tectonic movements in the previously formed basaltic andesites likely promoted the emergence of permeable zones, through which new portions of the melt leaked. In a limited space, high fluid gas saturation, temperature, and pressure fostered the extraction of metal compounds from the melt and host rocks.

The paper considers the composition of sandy rocks from the Upper Triassic deposits of the Mongugai Formation of southwestern Primorye and presents the results of its paleogeodynamic interpretation. It has been established that, according to their mineralogical and geochemical parameters, sandstones are petrogenic, correspond to graywackes and, only partially, to lithite arenites, are characterized by a significant degree of geochemical maturity of the clastic material, and their formation occurred due to the erosion of significantly weathered parent rocks of the source areas. Generalization and paleogeodynamic interpretation of the data obtained indicate that sedimentation in the southwestern Primorye in the Late Triassic occurred in basins related to the active continental margin settings probably complicated by strike-slip dislocations along transform faults. The dominant source of detrital material was continental land: cratons and crystalline basement inliers surrounding the rift zones or along transform faults. Felsic granite-metamorphic complexes were eroded with the participation of sedimentary rocks enriched with ancient components. A secondary source was a deeply dissected continental-margin igneous arc, which supplied an additional amount of sialic material, as well as a small amount of the basic–intermediate volcaniclastic rocks into the basin. The U–Pb geochronological studies of detrital zircons from sandy rocks of the formation made it possible to establish the age and the possible position of igneous complexes, destruction of which formed the sediments.

A comprehensive study of the Maastrichtian–Danian boundary rocks in the Klementyev Mountain section (eastern Crimea) was carried out. The lithological characteristics of carbonate, carbonate–clayey, and clastic rocks are scrutinized. The dynamic of changes in the benthic and planktonic foraminiferal assemblages is analyzed. The geochemical and isotopic data were obtained for this section for the first time. The stratigraphic range of the upper Maastrichtian and lower Danian has been specified. The late Campanian–early Maastrichtian age of the underlying rocks has been confirmed for the first time. Sediments of the Klementyev Formation were deposited in a deep-sea pelagic paleoenvironment on the submerged part of the outer shelf, whereas the overlying Lower Danian sediments were deposited in shallow waters of the inner shelf with terrigenous sedimentation and high hydrodynamic activity.

The results of studies of the regional structure of Solenovian deposits of the Early Oligocene Rupelian Stage in the Cisсaucasian–Caspian region, which represented the northern slope of Eastern Paratethys in the Cenozoic, are presented. The geological structure and paleogeographic conditions in the basin during the Solenovian (second half of Early Oligocene) were refined based on a comprehensive interpretation of geological and geophysical materials. The spatial consequences of the sea level drop in Eastern Paratethys during the Oligocene regressions are traced. The periodic draining of shelf areas is reflected in the structure of erosional unconformities and buried river incisions. It has been established that the most significant was the late Solenovian regression with a relative sea level drop by more than 500 m. Consequently, a prominent unconformity surface, complicated by river incisions, was formed in the sedimentary sequence in the shelf part of the paleobasin (Maikop seismic sequence). Erosion ledges and landslide bodies formed on the slopes, and basin-infill complexes were accumulated in depressions.