Biogeochemistry, a prospecting tool in the search for mercury mineralization

Summary of biogeochemical prospecting for mercury mineralization in the Pinchi Fault is given. One thousand two hundred and eight plant samples were collected and analyzed for mercury. In mineralized areas the typical mercury content of dried plants was not less than 0.2 and 0.4 μg/g and even concentrations between 0.6 and 1.6 μg/g were observed. In nonmineralized zones at least 90% of the plants contained no more than 0.15 μg/g of mercury. Analytical and sampling procedures are described.     

Temperature variation in the mesosphere during solar eclipse

Rocket-borne observations of the extinction of solar hydrogen Lyman-alpha radiation made during the solar eclipses of 20 May 1966 at Karistos for normal and 44% visibility and of 7 March 1970 at East Quoddy for normal, 10% and 0.6% visibility have been used to study the variation of temperature in the mesosphere during these events. It is seen that near the mesopause the decrease of temperature at Karistos is by 20° K for 44% visibility and at East Quoddy by 100° K for 0.6% visibility. Possible causes of these temperature variationsvis-a-vis molecular oxygen and pressure variations have been briefly discussed.     

The Features of the Transformation of Organic Matter of Precambrian Carboniferous Rocks of the Ukrainian Crystalline Shield

The main features of the transformation of organic matter (OM) in the greenschist, amphibolite, and granulite facies of metamorphism are considered based on the example of the Ukrainian crystal shield. The occurrence area and OM content in highly carbonaceous ancient rocks are characterized. The composition of primary sedimentary rocks and the processes of accumulation of biophile elements under the OM transformation are reconstructed.     

Main Stages of Evolution of Pacific Ferromanganese Stromatolites and Oncolites

As exemplified by cobalt–bearing Fe–Mn crusts (ferromanganese stromatolite) of the Magellan Seamounts (Clarion–Clipperton Province), the main stages of the structural evolution of bacterial communities have been recognized. It has been demonstrated that the change of the stages is caused by the effect of major tectonic, volcanic, and other geological events.     

The Spots and Activity of Stars in the Beehive Cluster Observed by the Kepler Space Telescope (K2)

The spottedness parameters S (the fraction of the visible surface of the star occupied by spots) characterizing the activity of 674 stars in the Beehive Cluster (age 650 Myr) are estimated, together with variations of this parameter as a function of the rotation period, Rossby number Ro and other characteristics of the stars. The activity of the stars in this cluster is lower than the activity of stars in the younger Pleiades (125 Myr). The average S value for the Beehive Cluster stars is 0.014, while Pleiades stars have the much higher average value 0.052. The activity parameters of 61 solar-type stars in the Beehive Cluster, similar Hyades stars (of about the same age), and stars in the younger Pleiades are compared. The average S value of such objects in the Beehive Cluster is 0.014± 0.008, nearly coincident with the estimate obtained for solar-type Hyades stars. The rotation periods of these objects are 9.1 ± 3.4 day, on average, in agreement with the average rotation period of the Hyades stars (8.6 ^d ). Stars with periods exceeding 3–4 ^d are more numerous in the Beehive Cluster than in the Pleiades, and their periods have a larger range, 3–30 ^d . The characteristic dependence with a kink at Ro (saturation) = 0.13 is not observed in the S–Rossby number diagram for the Beehive and Hyades stars, only a clump of objects with Rossby numbers Ro > 0.7. The spottedness data for the Beehive Cluster and Hyades stars are in good agreement with the S values for dwarfs with ages of 600–700 Myr. This provides evidence for the reliability of the results of gyrochronological calibrations. The data for the Beehive and Pleiades stars are used to analyze variations in the spot-forming activity for a large number of stars of the same age that are members of a single cluster. A joint consideration of the data for two clusters can be used to draw conclusions about the time evolution of the activity of stars of different masses (over a time interval of the order of 500 Myr).     

Clay Minerals in Basalt Sills from the Sediment Cover,East Pacific Rise

Clay minerals in basalt sills from the northern East Pacific Rise, covered by Upper Pleistocene clayey–sandy–silty sediments (turbidites, hemipelagites, and diatom oozes) sampled from DSDP Holes 477, 478, and 481A, were studied by X-ray methods based on the modeling of diffraction patterns. Trioctahedral smectites formed in thin (0.1–0.5 and 1.8–4 m) fissured sills that are well permeable for water delivered from the water-saturated host sediments heated by the sills. Smectites in basalts are found in the interstices (20–40 vol % in the rock and up to 50–80 vol % in hyalobasalts). They replace olivine and fill cracks and vesicles. Plagioclase and clinopyroxene are generally unaltered. The structure of smectites is characterized by different height of layers depending on the composition of cations in the interlayers and the degree of their hydration. The different-height layers either make up individual smectite phases or alternate in different proportions and with a high degree of segregation in the mixed-layer structures. Under conditions of a prolonged cooling, thick (43 m) sills are distinguished from the thin varieties by the formation of trioctahedral minerals (smectite–chlorite, chlorite, defective chlorite, and talc). They are found mainly in the interstices that make up 3–7 vol % of the rock.     

Mudbank regime off the Kerala coast during monsoon and non-monsoon seasons

Field experiments conducted in the nearshore ocean to understand the dynamics of mudbank off Kerala, south-west coast of India, are highlighted. Real time monitoring of the nearshore ocean off Purakkad, Kerala was accomplished using pressure transducers for nearshore surface wave measurements, and current sensors for nearshore velocity measurements. Comprehensive information on the spatial structure of mudbank was obtained from aerial surveys. Extensive data collected on surface waves and currents in the nearshore ocean, indicate that the infra-gravity (IG) waves (leaky modes and trapped edge wave modes), and far infra-gravity (FIG) waves coupled with strong shoreline reflections and undertow play an important role in the dynamics associated with the mudbanks off Kerala during the monsoon season. During the non-monsoon season evidence for progressive edge waves in the infragravity frequency band, an energetic gravity wave band and a strong undertow with weak reflections was observed.