Investigations of karstic springs of the Biokovo Mt from the Dinaric karst of Croatia

Ten gravity springs from the slopes of the Biokovo Mt, Adriatic coast of Croatia were investigated. Three of them are included in the regional water supply system. The aim of this study was to investigate hydrogeological and geochemical characteristics of watershed, presenting one of the most typical karstic areas in the world.Hydrogeological investigations were performed during two seasons with dye tracing, using Na-fluoresceine which was poured into two pits, observing springs at distances of 1.82–8.8 km. Apparent velocities were 0.21–0.51 cm s^?1. Dye tracing was first time partially effective and second time ineffective, what could be due to immanent ore mineralization, which presents a natural barrier and was discovered by geochemical and mineralogical methods.Concentrations of 17 dissolved and total trace elements were determined first time in groundwater samples. Their concentrations were extremely low, more than 3 orders of magnitude less than allowed by the Croatian directives for the first category of groundwater and drinking water. The mass fractions of 60 elements were determined in 3 representative spring sediments. Highest concentrations of some metals in sediments (mg kg^?1) are: lead 5440, chromium 118, manganese 935, zinc 116 and barium 238. Origin of some elements and mineralogy is discussed.     

Laurite and Ir-Osmium from Plagioclase Lherzolite of the Yoko–Dovyren Mafic–Ultramafic Pluton,Northern Baikal Region

The near-bottom part of the Yoko-Dovyren layered ultramafic-mafic intrusion host the Baikal deposit of Cu–Ni sulfide ores with Pt–Pd mineralization, whereas horizons and pockets of low sulfide ores with Pt–Pd mineralization occur at higher stratigraphic levels, including the boundary between strata of troctolite and gabbronorite, within these rocks, as well as in strata of peridotite at the lower part of the intrusion. This paper represents a new (for the Yoko-Dovyren intrusion) type of “refractory IPGE-mineralization” discovered in the lower peridotite ranging from two-pyroxene-plagioclase-bearing lherzolite. This mineralization occurs in thin intercalations of plagioclase lherzolite containing as much as 7% of alumochromite, up to 50 ppb Ru, 15 ppb Ir, and 60 ppb Pt. Crystals of cumulate alumochromite with 0.2–0.8 wt % TiO₂ contain hexagonal plates of Ir-osmium up to 5 m in size. Crystals of cumulate alumochromite with 1.2–2.8 wt % TiO₂ host pentagonal dodecahedrons of laurite up to 4 m in size. One of the alumochromite crystals with an inclusion of Os-poor laurite was found inside a crystal of cumulate olivine Fo86. Intergrowth of laurite and Ir-osmium enclosed in alumochromite with 1.1% TiO₂ was observed in one case. Laurite from Yoko-Dovyren contains 93–66%, predominantly 92–82%, RuS₂ endmember (n = 10); 3–20, predominantly 5–12%, OsS₂ endmember; 4–5% IrS₂ endmember; and up to 0.7% Pd and 0.5% Au. Ir-osmium is divided into two groups by composition. The first group is enriched in Os (58–73 wt %, on average 64 wt %) and Ru (3–8 wt %, on average 5 wt %), contains 24–34 wt % Ir (n = 4), up to 1.4 wt % Au, and no Pt. Compositions of the second group have 57–58 wt % Os, 27–30 wt % Ir, 1.5–5.5 wt % Ru, approximately 10 wt % Pt (n = 3), and up to 0.2 wt % Pd. The Cr# and Fe²⁺/(Fe²⁺ + Mg) values, which range within 58–69 and 61–72, respectively, are identical in alumochromite with both enclosed laurite and Ir-osmium. Alumochromite, relatively enriched in Ti, crystallized slightly later, suggesting later crystallization for hosted laurite. Occurrence of Ir-osmium seems to indicate a picritic magma undersaturated with sulfide sulfur during bulk crystallization of alumochromite Judging from the diagram from (Brennan and Andrews, 2001), intergrowths of laurite and Ir-osmium, evidence that their probable crystallization temperature did not exceed 1250°C. The presence of own minerals of Ru, Os, Ir in the rocks, containing the first ppb of these PGE shows startling degree of magmatic differentiation. In the matrix of plagioclase lherzolites, containing laurite and Ir-osmium, in association with phlogopite, pargasite, pentlandite, troilite and chalcopyrite there were found the smallest crystals of geversite, sperrilite, insizwaite, niggliite, naldrettite, zvyagintsevite, in association with serpentine and chlorite–native platinum, Pd-platinum, osarsite, irarsite, platarsite.     

Natural and anthropogenic sources of Hg,Cd, Pb,Cu and Zn in seawater and sediment of Mljet National Park,Croatia

Distributions of Hg, Cd, Pb, Cu and Zn in seawater and sediment from Mljet National Park, Adriatic Sea are presented for the first time. Natural and anthropogenic factors play an important role in determining resultant trace metals' concentrations in the region. We place particular emphasis on the saline “lakes” of Malo Jezero and Veliko Jezero, which have restricted flows of seawater. In Malo Jezero lake, fresh karstic spring water generated by flooding, and weathering of dolomites are the main sources of naturally elevated Cd, Pb and Zn concentrations (20.7 ± 1.6, 289 ± 19, 1260 ± 0.08 ng L^?1, respectively); anthropogenic input is negligible. In Veliko Jezero lake enhanced Cu and Zn contents originate from anthropogenic input (tourism and agriculture). Distributions of the Pb and Zn in the water columns of both lakes are influenced by natural aragonite precipitation and sedimentation. Exceptionally high total Hg concentrations of 24.2 and 33.7 ng L^?1 in the water column of Malo Jezero, sampled during periods of high rainfall associated with strong eastern winds, suggest an airborne input. Total Hg concentrations in waters of both lakes are elevated because of inefficient mixing. Two different metal distribution patterns exist in the sediment columns. First, Hg, Pb, Cu and Zn show elevated concentrations in recent sediments due to anthropogenic input. Second, Cd content increases with depth due to reprecipitation via a downward redox boundary shift.Described natural processes, as well as anthropogenic influence, enhance levels of trace metals. Careful study followed by suitable interpretation based on geochemical data were necessary to distinguish natural from anthropogenic sources.     

Benthic Assemblages of the Powell Basin

Oceanology - —During 79th cruise of R/V Akademik Mstislav Keldysh twelve trawl hauls were collected in Powell Basin and adjacent area at depths 370–3771 m. The structure of the benthic...     

Cl-bearing lizardite in metamorphosed kimberlites from the Udachnaya Vostochnaya Pipe,Yakutia

Anhydrite-bearing dolomites and kimberlites from the contact zone of the Udachnaya Vostochnaya pipe, northern part of the Eastern Siberian Platform, were affected by low-grade metamorphism to the zeolite facies. The kimberlites are serpentinized and carbonatized and contain metasomes of anhydrite and saponite pockets. Twenty lizardite pseudomorphs after olivine (Fo _91–82) in the kimberlites were examined on an electron microprobe. The lizardite is rimmed by saponite and contains dolomite, calcite, magnetite, and anhydrite inclusions. Lizardite in the central parts of the pseudomorphs contains 1.5–1.9 wt % Cl and 6–9 wt % Fe₂O₃, and this mineral in the outer portions of the pseudomorphs bears 0.7–1.0 wt % Cl and 2–6 wt % Fe₂O₃ (the paper presents nine microprobe analyses and images showing the distribution of Cl, Mg, Al, Si, S, Ca, Ti, and Fe obtained in characteristic X-ray radiation). The amounts of Fe³⁺ in octahedrally and tetrahedrally coordinated sites of the Cl-bearing lizardite are roughly equal. Cl was borrowed in the course of serpentinization from the host Early Paleozoic evaporites and brines contained in them. The Cl concentration in our lizardite from the metamorphosed kimberlites from the Eastern Siberian Platform (continental lizardite) is much higher than the Cl concentration in oceanic lizardite from serpentine replacing peridotites (0.03–0.2 wt % Cl). This is likely explained by differences in the Cl concentrations in the metamorphic fluids, their salinity (3% for oceanic water and 65% for brines in the platform cover).     

Modeling of the Earth’s pole motion from data on the atmospheric and oceanic angular momenta over 1980–2002

The model values of the mantle quality factor Q=40±20 and the Chandler wobble period T=435–436 days are obtained by numerical modeling of the yearly and Chandler components in the pole motion from data on the angular momenta of the atmosphere and the ocean. The oceanic and the atmospheric excitations account for about 65–70% of the dispersion of the observed pole motion.     

New data on the Pb isotope composition of Noril’sk sulfide ores

Doklady Earth Sciences -