The Lomonosov Equatorial Undercurrent according to Data Measured with a Shipborne Profiler, 2014–2017

The velocity and structure of the Lomonosov Equatorial Undercurrent of the Atlantic Ocean are determined based on the data measured with a shipborne acoustic profiler from 2014 to 2017. The seasonal variability of this flow is estimated, and the cases of its outcropping to the surface in the spring of the Northern Hemisphere are revealed.

     

Symplectitic augite: evidence for discontinuous precipitation as an exsolution mechanism in Ca-rich clinopyroxene

Abstract Part of the augite in the Artfjället gabbro consists of symplectitic intergrowths between augite and blebs or lamellae of orthopyroxene. Mineral compositions are consistent with formation of these symplectites by exsolution of orthopyroxene from magmatic augite at a temperature of ca . 900–1000°C. The microstructures indicate that the exsolution mechanism is discontinuous precipitation, whereby the boundary of an augite grain sweeps through a neighbouring augite, leaving the symplectite in its wake. The formation of this symplectitic augite is catalysed by the presence of an intergranular water-rich fluid phase, which promotes grain boundary mobility.     

The Hinode Spectro-Polarimeter

The joint Japan/US/UK Hinode mission includes the first large-aperture visible-light solar telescope flown in space. One component of the Focal Plane Package of that telescope is a precision spectro-polarimeter designed to measure full Stokes spectra with the intent of using those spectra to infer the magnetic-field vector at high precision in the solar photosphere. This article describes the characteristics of the flight hardware of the Hinode Spectro-Polarimeter, and summarizes its in-flight performance.     

Mixed-layer corrensite-chlorites and their formation mechanism in the glauconitic sandstone-clayey rocks (Riphean, Anabar Uplift)

The paper presents the first detailed mineralogical, structural, and crystal-chemical characteristics of the mixed-layer corrensite-chlorites from the glauconitic sandy-clayey rocks that make up the bottom (0.10 m) of a basal member (1.50 m) of the lower subformation of the Yusmastakh Formation (Riphean, Anabar Uplift, North Siberia). Like the overlying mudstones (1.40 m) in the basal member, these rocks are generally transformed up to the deep catagenesis level and included in a thick dolomite sequence. In mudstones represented by the dioctahedral micas, the corrensite-type minerals are observed as traces.     

Determining rainy season onset and retreat over Nigeria from precipitation amount and number of rainy days

Summary This study assesses the relative efficiency of the use of rainfall amount and rainy days in the determination of rainfall onset and retreat dates in Nigeria based on rainfall data for the period 1961 to 2000. Daily rainfall data were sourced from the archives of the Nigerian Meteorological Services, Oshodi Lagos. The specific locations for which data were collected are: Ibadan, Ilorin, Kaduna and Kano. The method of percentage cumulative mean rainfall values was employed in the determination of the rainfall onset and retreat dates. The results obtained show that both rainfall amount and rainy days are equally effective in the determination of the mean rainfall onset and retreat dates in Nigeria. With regards to the rainfall onset and retreat dates of the individual years however, the method based on the rainy days is more effective than that based on rainfall amount, as the former yielded more realistic dates than the latter. It is thus recommended that studies investigating rainfall onset and retreat dates within a series of individual years in Nigeria, should be based on rainy days rather than rainfall amount.     

Pressure-temperature cartography of Fe-S-Si immiscible system

Multi-anvil press experiments were performed using a single cell assembly containing six different compositions. This set-up allows a careful sampling of the miscibility gap for given P-T conditions. Shrinking of the miscibility gap in the Fe-S-Si system has been studied from 4 to 12 GPa up to 2200 K, demonstrating a stable immiscible zone up to 4 GPa and 2200 K and its closure at higher pressures. Presence of both S and Si in the Earth’s core is suggested by chondritic models. Therefore, its composition is inherited from processes at pressures higher than 4 GPa. This evolution of the Fe-S-Si miscibility gap is linked with the change in the local short-range order in Fe and Fe-S liquids. Our results indicate that core formation under reducing conditions would be affected by immiscibility for planetesimals up to size of the Moon. Furthermore, due to the difference in wetting properties between the two immiscible liquid phases, the S-rich metal phase would control the chemical exchange between liquid metals and silicates during early differentiation in planetesimals.