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A geochronological and isotope–geochemical study of alkaline basalts from three areas of young magmatism within the northeastern part of the Arabian Plate (Southeastern Turkey), Batman, Kurtalan and Alemdağ, was carried out. The obtained isotope data have indicated that the volcanism in the studied region developed over a 5-Ma period from the end of Miocene to the middle Pleistocene during four pulses separated by breaks in magmatic activity: 6.1–4.9 Ma (Batman area, hawaiites), ~3.0 Ma (Alemdağ plateau, phase I, basalts), 2.0–1.9 Ma (Alemdağ plateau, phase II, tephrites), and 1.5–1.3 Ma (Alemdağ plateau, phase III, basalts; Kurtalan area, basalts). A comparison of spatial–temporal changes of magmatic activity evolution in the studied part of the Arabian Plate and within the largest basalt plateau of Arabian foreland, Karacadağ Plateau, located to the west, was carried out. The results of Sr–Nd–Pb isotope–geochemical studies show that the development of young basalt volcanism in the Arabian Plate was characterized at different time by the contribution of various mantle sources in magma generation under this region. Initial pulses of magmatic activity are associated with melting of Arabian subcontinental lithospheric mantle (SCLM). The processes of fractional crystallization combined with crustal assimilation (AFC) have played an important role in the petrogenesis of lavas as well. Later, a deep mantle source (PREMA) with a depleted isotopic composition played a leading role in the formation of basaltic magmas of increased alkalinity. The melts generated by this source were mixed with the SCLM material in various proportions at different stages of magmatism with a limited participation of AFC processes in the petrogenesis of the rocks. It was concluded that young basalt volcanism of increased alkalinity in the northeast of the Arabian Plate is not related to the collision of the Eurasian and Arabian plates genetically, but presumably manifested here as a result of the migration of the initial rift geodynamic setting from the Red Sea basin to the north along Levantine and East Anatolian transform faults due to directed convection flows in the lower part of mantle under this part of the Earth. [ABSTRACT FROM AUTHOR]

Petrogeochemical data on basalts (lithophile elements and Sr–Nd–Pb isotopes, liquidus olivine and spinel compositions) from the transition zone of the Southwest Indian Ridge (SWIR) in the Du Toit–Andrew Bain fault zone indicate significant differences in their composition. Tholeiites enriched in Na and depleted in Fe (Na-TOR genetic type) are developed within the rift valley adjacent to the faults. Deep-type basalts (TOR-1) are present in the western wall of the Andrew Bain Fault. The outpouring of these magma types reflects a possible change in geodynamic setting during formation of this zone: from deep and high temperature to shallower magma generation conditions (Sushchevskaya et al., 2022). Differences in the primary melts of tholeiites from the rift valley and the Andrew Bain Transform Fault are also traced in the composition of liquidus olivine. The olivines from rift valley are similar to the typical Na-TOR olivines with Mg number of Fo88-87, low Ni and elevated Mn contents. On the contrary, olivines in tholeiite from the Andrew Bain Fault Zone are enriched in Ni and depleted in Mn, which may indicate the involvement of pyroxenite in melt generation. This component is either oceanic lithosphere recycled through the deep mantle or fragments of previously formed oceanic crust, which were subsequently involved in melting during the spreading axes jumping. A similar process is typical of the Bouvet Triple Junction, where the trace-element composition of olivine shows significant heterogeneity. The radiogenic composition of Pb and Sr of the Andrew Bain Fault tholeiites are similar to those of enriched magmas from such Indian Ocean rises as Crozet, Marion and Bouvet, but differ from those of the Conrad and Af. Nikitin rises. The source of such tholeiite melts is close in composition to the model HIMU type (with high U/Pb), which likely contains an admixture of EM-II component (with elevated Rb/Sr). [ABSTRACT FROM AUTHOR]

Numerous orogenic gold deposits of different age, scale, and mineralization type are located within Northern Transbaikalia. Among them, there is a large group of Early Permian deposits, whose sources and relationships with Late Paleozoic magmatism remain debatable. These issues were solved by the example of the middle-scale (~24 t, Au) Irokinda deposit, localized within the Precambrian rocks of the Baikal–Muya Terrane. 39Ar–40Ar geochronological dating of the ore-hosting altered rocks indicates that hydrothermal–metasomatic process took place about 270 myr ago. Gold mineralization has heterogeneous Pb-, S-, Sr-, and Nd-isotopic characteristics. Variations in the Pb, S, Sr, and Nd isotopic composition of ore and gangue minerals suggest that the mineral-forming components were involved in the hydrothermal system from different sources. Among them, the leading role belonged to the rocks of the Precambrian crust of the Baikal–Muya Terrane. Pb isotopic composition of the second identified source is close to that of the Early Permian alkaline and subalkaline rocks of the Baikal–Muya Terrane. This fact may indicate a genetic relationship between the Irokinda gold mineralization and intraplate alkaline magmatism, which developed in the region simultaneously with ore-forming processes. [ABSTRACT FROM AUTHOR]

The paper discusses the geochemical and Sr-Nd-Pb-isotope data on ice-rafted sediments (IRS) from different areas of the Arctic Ocean. Samples were collected during the Cruise of R/V Polarstern between Spitsbergen and North Pole, Yermak Plateau, as well as in Fram Strait. It is shown that the studied IRS samples in terms of LaN/YbN and εNd values are close to the composition of suspended particulate matter (SPM) from the mouth parts of large rivers and rivers transporting the sedimentary erosion products. This also follows from their Th/Sc, Th/Co, La/Sc, La/Sm, Sc/Th ratios and Sc content and from the position of their data points in the Sc-Th/Sc, La/Sc-Th/Co, and La/Sm-Sc/Th diagrams between the average SPM compositions of the Ob and Lena rivers. The values of 207Pb/206Pb and εNd in IRS samples give grounds to suggest that the rock complexes of the European, North American, and Asian continental margins could be potential sources for this sedimentary material. In the 207Pb/206Pb-εNd diagram, the IRS samples from all three studied areas define a compact cluster and are mainly confined to the triangle with corners represented by the Mackenzie River, Okhotsk-Chukotka volcanic area, and Lena River, being closer to the latter. In the Sm/Nd-εNd diagram, IRS points also form a compact field, being located almost in the middle between the average SPM compositions of the Yenisei and Ob rivers, on the one hand, and Lena River, on the other. In all diagrams, IRS samples from the different West Arctic areas show no significant scatter. With allowance for the fact that sediments are not subjected to significant homogenization during ice rafting, sediments from all three areas were obtained from a common source. As seen from the position of IRS data points in the 87Sr/86Sr-εNd diagram, this source was the Asian continental margin. [ABSTRACT FROM AUTHOR]

Data on strontium accumulation acquired by studying the floodplain soils of the Kuda River, Irkutsk Region, show that the bulk accumulation of this element and the accumulation of its water-soluble species are controlled by evaporative concentration. Floodplain areas maximally enriched in water-soluble strontium are defined. These areas are the most potentially hazardous if involved in agricultural activities because Sr can be transferred there into the surface- and soil-groundwaters in concentrations several times higher than the maximum permissible concentrations of this element in water bodies. [ABSTRACT FROM AUTHOR]