Vol 57, No 11 (2019)

We report the first combined investigation (neutron activation, X-ray fluorescence, and electron microprobe analysis) of mineral forms of Au and Ag and noble metal distribution in the sulfide-bearing phoscorites and carbonatites of the Guli alkaline ultrabasic massif (Polar Siberia) and magnetite and sulfide separates from these rocks. The highest noble metal contents were observed in the sulfide separates from the carbonatites: up to 2.93 Pt, 61.6 Au, and 3.61 ppm Ag. Pyrrhotite, djerfisherite, chalcopyrite, and pyrite are the most abundant sulfides and the main hosts for Au and Ag. The latest assemblage of chalcopyrite, Ag-rich djerfisherite, lenaite, sternbergite, and native silver shows significant Ag concentrations. The wide occurrence of K sulfides and presence of multiphase inclusions in pyrrhotite consisting of rasvumite, K‒Na–Ca carbonate, carbocernaite, strontianite, galena, chalcopyrite, sternbergite, lenaite, and native silver suggest that the sulfides were formed at high activities of K, Na, Sr, LREE, F, Cl, and S. Chlorine shows high complex-forming capacity to Ag and could be an agent of noble metal transport in the carbonatites. Crystallization of the early djerfisherite–pyrrhotite assemblages of the phoscorites and carbonatites began at a temperature not lower than 500°C and continued up to the formation of late Ag-bearing sulfides at temperatures not higher than 150°C. The carbonatite-series rocks could be enriched in Au and Ag during late low-temperature stages and serve as a source for Au placers.

The western Anatolian Miocene volcano-sedimentary basins in the Gördes, Demirci and Şaphane regions host abundant heulandite/clinoptilolite (hul/cpt) bearing widespread zeolitized pyroclastic rocks. Lithostratigraphy of these zeolitic pyroclastic levels show comparable association. Petrography and geochemistry of all the samples show mainly rhyolithic and rhyodacitic character and ash size vitric tuffs. Polarized microscopy and X-ray diffraction determinations of the samples show composition of 55–95 wt % hul/cpt and accessory of smectite, illite/mica, opal–CT, quartz, K–feldspar, plagioclase and opaque minerals. Geochemical results obtained from the studied samples represent hul/cpt–rich facieses formed under the moderate alkaline conditions in these pyroclastic units. Correlation of geochemical results and concentration of hul/cpt in these pyroclastic rocks gives some chemical data on zeolitization process and on adsorption and ion-exchange character of hul/cpt type of zeolites. Depleted and enriched elements by zeolitization have similar ionic radii in general. Ca and H₂O clearly increased, Si, Na and Si/Al ratio decreased in hul/cpt bearing Lower-Middle Miocene pyroclastic rocks of western Anatolia. Additionally, Sr, Nb, Th, Ni, Hf, Cs, Pb and Ta increased, and Zr, Co, W and most of the rare earth elements (REE) decreased in highly hul/cpt–rich pyroclastics.

The paper presents authors' original data on the isotope composition of the natural “excess” Pb‑210 and artificial Cs-137 radionuclides in the upper 25- to 50-cm layer of sea-bottom sediments in the Kara Sea (from the Ob and Yenisei estuaries, Eastern Novaya Zemlya trough, Voronin trough, and Sedov bay at the Novaya Zemlya). Sediment cores were collected during Cruises AMK-63 and AMK-66 of the R/V Akademik Mstislav Keldysh in 2015 and 2016. Results of this research show strong correlations between the sedimentation rates and facies-genetic types of the sea-bottom sediments. The highest sedimentation rates are typical of the terrigenous–estuarine sediments, which are subdivided into tractional load, whose sedimentation rate is 0.4–0.7 cm per year, and “mud bank” sediments, whose sedimentation rate is 0.7–1.0 cm per year. The terrigenous shallow marine sediments are characterized by the lowest sedimentation rate of 0.1–0.3 cm per year. The background terrigenous marine sediments show broad variations in the sedimentation rates: these rates are at a minimum (and comparable to the sedimentation rates of the terrigenous shallow marine sediments) on trough slopes and can increase to 0.9 cm per year in the central parts of the trough (as a result of gravity creep). The glacial sediments of Novaya Zemlya bays belong to a separate individual type. The measured “current” sedimentation rate within the inner depression of the Sedov bay is 0.1–0.2 cm per year.

The plagioperidotites of the Yoko-Dovyren ultramafic–mafic intrusion, which were affected by low-grade metamorphism (LGM) to the prehnite–pumpellyite facies (PPF), show evidence of Ba, Cl, and Sr mobilization. The background Ba and Sr contents in the plagioperidotites are 36–313 ppm (at an average of 130 ppm) and 25–169 ppm (average 86 ppm), respectively, at Ba/Sr = 0.5–4 (average 1.5). The Ba-bearing minerals are phlogopite and plagioclase, and the Cl-bearing ones are chloroferrisadanagite in alumochromite-hosted inclusions, late magmatic phlogopite, K–Cl ferropargassite and Cl-apatite in the margins of sulfide pockets. In the course of the low-grade metamorphism, these minerals were replaced by chlorites, tremolite, and diopside, which contain very little Ba and Cl. In plagioperidotite domains containing Ba‑bearing minerals, these rocks contain 348–518 ppm Ba and 4–6 ppm Sr, which indicates that Ba was redistributed and Sr was removed. The metamorphic Ba minerals are Sr-free barite and Ba–Fe–Cl mica: Cl-dominant ferrokinochitalite. They coexist with minerals of the rodingite association: hydrogarnet, tremolite, diopside, chlorite, antigorite, magnetite, and hydroxylapatite. The ferrokinoshitalite replaces phlogopite, plagioclase, and sulfides, contains up to 21 wt % BaO, 31% FeO, and 11% Cl, and has a Fe mole fraction f = 75.8–90.5. The composition of a ferrokinochitalite individual riches in Cl corresponds to the formula \({{{\text{(B}}{{{\text{a}}}_{{{\text{0}}{\text{.83}}}}}{{{\text{K}}}_{{{\text{0}}{\text{.16}}}}}{\text{)}}}_{{{\text{0}}{\text{.99}}}}}{{{\text{(Fe}}_{{2.63}}^{{2 + }}{\text{M}}{{{\text{g}}}_{{{\text{0}}{\text{.28}}}}}{\text{Fe}}_{{0.04}}^{{3 + }}{\text{A}}{{{\text{l}}}_{{{\text{0}}{\text{.02}}}}}{\text{C}}{{{\text{r}}}_{{{\text{0}}{\text{.01}}}}}{\text{M}}{{{\text{n}}}_{{{\text{0}}{\text{.01}}}}}{\text{)}}}_{{\text{3}}}}{\text{[(C}}{{{\text{l}}}_{{{\text{1}}{\text{.86}}}}}{\text{O}}{{{\text{H}}}_{{{\text{0}}{\text{.12}}}}}{{{\text{S}}}_{{{\text{0}}{\text{.02}}}}}{{{\text{)}}}_{{\text{2}}}}{\text{/A}}{{{\text{l}}}_{{{\text{1}}{\text{.86}}}}}{\text{S}}{{{\text{i}}}_{{{\text{2}}{\text{.14}}}}}{{{\text{O}}}_{{{\text{10}}}}}{\text{]}}\). Because ferrokinochitalite from the Yoko-Dovyren Massif is Cl-dominated, it is a new mineral species.

The variation of groundwater properties caused by seawater intrusion, such as OH^–, TDS, \({\text{SO}}_{4}^{{2 - }},\) can potentially affect the groundwater Se levels. But there are no researches detailing the mechanism of groundwater selenium characteristics in seawater intrusion areas along coastal zones. Buzhuang town has been selected for study and groundwater is sampled to discuss the behavior of groundwater selenium with the intrusion of seawater. The groundwater Se levels range from 1.43 to 15.60 µg/L, with an average of 6.23 µg/L. All are within the limit of 10 µg/L except Wanglu village, but the local groundwater Se levels in 8 villages exceed the chronic criterion of 5 µg/L, and the Se levels in local groundwater are higher than those in the supplied water which has a non-seawater source. The groundwater Se levels have been shown to be elevated by seawater intrusion. The groundwater Se levels are positively correlated with Cl^–, TDS, Br^–, Na⁺, Mg²⁺, \({\text{SO}}_{4}^{{2 - }},\) Ca²⁺ and Fe and negatively correlated with pH. Ion competition effects and the Na-Mg-sulfate minerals play an important role in the adsorption and desorption for \({\text{SeO}}_{3}^{{2 - }}\) and \({\text{SeO}}_{4}^{{2 - }}\), which are the important dynamic species for groundwater selenium enrichment. However, Ca and Fe ions have less contribution to groundwater Se variation because of the lower affinity for \({\text{SeO}}_{3}^{{2 - }}\) and \({\text{SeO}}_{4}^{{2 - }}\) and lesser content in groundwater of seawater intrusion areas.