The chromian spinels of the Lyavaraka ultrabasic complex, Serpentinite Belt, Kola Peninsula, Russia: Patterns of zoning, hypermagnesian compositions, and early oxidation

ABSTRACT The maximum value of Mg# [= 100Mg/(Mg + Fe2+ + Mn)] in chromium-bearing spinel-group minerals (Chr) in the Ultrabasic Core Zone (UCZ) of the Lyavaraka orthopyroxenite – harzburgite – dunite complex of the Serpentinite Belt in the Kola Peninsula is 54.5–67.5. Such highly magnesian compositions of spinel are associated with notable enrichments of ferric iron (Fe3+# 58–63). There are two generations of accessory Chr in the UCZ unit. The first generation occurs as inclusions in olivine that is not unusually magnesian (Mg# 90.3), and the second is closely associated with serpentine. The compositional series of Chr at Lyavaraka attains more aluminous compositions than was observed in nearby intrusive bodies. The anomalously high level of Mg in Chr, also manifest in ilmenite, is mainly a result of the high intrinsic fugacity of oxygen attained locally in the melt. A progressive buildup in H2O and increase in fO2 likely resulted from efficient vesiculation and selective loss of H2 from the Al-undepleted komatiitic magma crystallizing in a shallow setting. The chromian spinel forming in such a modified magma is virtually unzoned in Mn, and a minor quantity of Mn is also present in olivine and orthopyroxene. In contrast, zinc is strongly partitioned in the core of Chr, as it is relatively incompatible in the coexisting olivine and orthopyroxene at that stage. Zinc efficiently partitioned into the H2O-enriched melt, which crystallized as the pegmatitic orthopyroxenite near the contacts at Lyavaraka. A high potential of oxidation appears to be characteristic of all orthopyroxenite – harzburgite – dunite suites of the Serpentinite Belt formed from a primitive melt of komatiitic composition.

Recovery of Hydrothermal Wustite-Magnetite Spherules from the Central Indian Ridge, Indian Ocean.

Not many studies have reported the hydrothermal-related origin of the magnetite-bearing spherules, and hardly any literature discusses the hydrothermal-related origin of wustite-magnetite-bearing spherules. A sediment sample with high abundance (19 spherules in ~85 g) of spherules is recovered from Central Indian Ridge (CIR) segment S2 (70°54′E, 25°14′S to 70°50′E, 24°41′S), ~85 km north of Rodrigues triple junction (RTJ). On the external surface of the spherules, magnetite appears as crystals, whereas wustite mostly appears as a homogenous glass phase. These spherules are composed of wustite and magnetite hosting Mn, unlike micrometeorites which essentially hosts Ni. Mn is more heterogeneously distributed with a relatively higher concentration in the wustite phase than the magnetite, suggesting hydrothermal origin. Furthermore, the presence of sulfide nano-particles in the wustite phase and a minor quantity of Pb and S in the ferrihydrite matrix points to the fact that CIR spherules are of hydrothermal origin. We propose that the CIR spherules originated by the interaction of the reduced hydrothermal fluids with the ultramafic/basaltic rocks or silica-undersaturated magmatic melts. The finding of Mn hosting wustite-magnetite assemblage suggests an active hydrothermal system in the near vicinity and can be considered as an additional proxy for locating hydrothermal vents.

Characterization of hydrothermal events associated with the occurrence of copper-molybdenum minerals in the El Chucho creek at Cerrito, Valle del Cauca-Colombia

At El Chucho creek, located to the west of the Valle del Cauca department in Colombia, some hydrothermal alterations affecting the Buga Batholith rocks and dykes of porphyritic quartz-dioritic and tonalitic composition were identified. These lithological units host mineral occurrences of pyrite, chalcopyrite, and molybdenite that occur disseminated in the rocks or associated with quartz veinlets. The hydrothermal alterations identified were phyllic, propylitic, and, in minor quantity, potassic. The two firsts alterations’ distribution is related to structures and pervasive, whereas the last one seems restricted to contact zones of porphyritic dykes on tonalite. Microthermometric data were acquired i) on quartz veinlets of 1 cm thick over a phyllic alteration zone, and ii) on quartz veinlet of 1 cm thick with chalcopyrite ± molybdenite and copper silicates, both veinlets cutting the phaneritic tonalite. Those data suggest that the mineralizing fluids have an aqueous-saline chemical system and were trapped under low volatile content. The microthermal data allowed authors to identify two mineralizing events. One of them of higher temperature, with homogenization temperatures between 275°C-480°C; as the second event is characterized by lower homogenization temperatures that range from 100°C to 139°C.

The effect of drying time on the yield and the chemical composition of essential oil and dissolved oil in hydrolat from aerial parts of Moroccan Thymbra capitata (L.) Cav

<p>The present research aimed to study the effect of drying time on the yield and chemical composition of essential oil (EO) and dissolved oil in hydrolat (HY) from aerial parts of Moroccan <em>Thymbra capitata</em> (L.) Cav. Drying of plant material was carried out naturally in the shade of a draughty place at room temperature (25–27°C). A series of 10 plant samples were subjected to hydrodistillation using a Clevenger-type apparatus. The results indicated that the yield of EO increased with drying time to reach the highest value on the 8^th drying day (2.7%), while the yield of HY has not undergone an apparent variation (0.2% – 0.6%). Based on the GC-MS analyses, EO was composed mainly of the phenolic monoterpene carvacrol (80.10%–92.27%) along with its biogenetic precursors' monoterpene hydrocarbons in a 1.02%–4.81% range <em>p</em>-cymene and 0.24% -1.86 % <em>γ</em>-terpinene. Other essential components occurring in minor quantity were sesquiterpene hydrocarbon <em>a</em>-humulene (2.58% – 4.67%) and oxygenated monoterpene linalool (0.80% –2.06%). At the same time, HY was constituted mainly of carvacrol (94.67–98.42%) along with <em>a</em>-humulene at much lower concentrations (0.31%–0.86%) and the oxygenated derivative acetovanillone acetate (0.2%–1.80%). On the other hand, the highest concentration of carvacrol in EO was reached on the 5^th day of the drying plant process (92.27%), while the HY recovered on the 7^th day has shown carvacrol in its highest concentration (98.42%).</p>

Heliophyllite: a discredited mineral species identical to ecdemite

The type material for heliophyllite, preserved in the Swedish Museum of Natural History in Stockholm, was re-investigated through a combined EPMA (electron probe X-ray microanalysis), Raman, and X-ray powder diffraction (XRPD) and single-crystal study. EPMA chemical data, together with Raman and single-crystal structural studies, point to heliophyllite being identical to ecdemite. XRPD synchrotron data highlight the presence of a minor quantity of finely admixed finnemanite in the analyzed material, explaining the presence of some additional diffraction peaks, not indexable with the ecdemite unit cell, reported in the literature. The discreditation of heliophyllite has been approved by the IMA Commission on New Minerals and Mineral Names (proposal 19-H, 2019).

Influence of Chitosan Addition on Resorcinol–Formaldehyde Xerogel Structure

Gels are usually not environment-friendly due to their difficult biodegradability. Therefore, the addition of chitosan, even in small amounts, will make such gels biodegradable and thus can be useful in many applications that require environment-friendly materials. The addition of small quantities of chitosan to the reacting solution resorcinol–formaldehyde xerogel was investigated. Different hybrid resorcinol–formaldehyde–chitosan xerogels were characterized by different techniques, including Raman spectra, FTIR, XRD, TGA, SEM, surface area and porosity analyzer, and CHNS/O microanalyzer. It was seen that the addition of chitosan, even in a minor quantity, has a significant influence on the structural features of the resulting xerogels. The lattice order and crystallinity, chemical functions, thermal stability, morphology, elemental ratio, pore structure, and appearance were changed by adding chitosan into the xerogel structure.

A new evidence of cretaceous echinoids at the region Paleokastro of Stylis area (Fthiotida district)

The rich Fauna of Echinoids (114 individuals) coming from the region Paleokastro Fthiotida has been found for the first time in Greece. The most part of the Echinoids studied, belongs to the genus Echinocorys{12%), and in minor quantity to the genus Micraster(8%), Galeaster(l%) and Coraster(19%). 17 species has been indentidied which have been distributed 13 to the genus Echinocorys ( E. conoideus, E. gravesi, E. humilis, E. lamberti, E. marginatus, E. obliquus, E. ovatus, E. pyramidatus, E. rectus, E. sulcatus, E. turritus, E. vulgaris, E. zejszneri), 1 to the genus Micraster (M. coranguinum), 1 to the genus Galeaster (G. cf. bertrandi) and 2 to the genus Coraster (C. sphaericus, C. frechi). The accompagnied fauna is consisting of one Scleractinian (Caryophyllia sp.) and one Nautiloid (Eutrephoceras dekayi (MORTON)). The stratigraphical distributions of the studied fauna allow us to accept that the cretaceous layers with the Echinoid Fauna belong to the Upper Maestrichtian age. The studied fauna, with his monotonous character, is an ecological niche of the genus Echinocorys living in almost littoral waters.

Diterpene Foliar Exudates of Blakiella bartsiifolia and Phytotoxicity of Clerodanes

Blakiella bartsiifolia (S.F. Blake), an endemic and rare high altitude plant of the northern Andes, appears well adapted to the prevailing harsh environment owing in part to a thick glandular trichome cover. From foliar exudates, two new clerodanes, 15,16-epoxy-2-hydroxy-3,13(16),14-clerodatrien-20-oic acid (bartsiifolic acid) (2) and Z-15,16-dihydroxy-3,13-clerodien-20-oic acid (barthydrolic acid) (3), were isolated in addition to the known junceic acid (1). In addition, three new alicyclic furanoditerpenes: 1,20-epoxy-1,3(20),6( E),10( E),14-phytapentaen-18-methyl-19-oic acid (blakielic acid) (4), 1,20-epoxy-1,3(20),10( E),14-phytapentaen-18-methyl-19-oic acid (blakifolic acid) (5) and 1,20-epoxy-1,3(20),6,14-phytatetraen-19-methyl-18-oic acid (dihydrocentipedic acid) (6) were obtained in minor quantity. Seed germination and plantlet growth bioassays on Allium cepa and Lactuca sativa to monitor bioactivity during isolation procedures revealed compounds 1–3 with substantial inhibition comparable with synthetic linuron.

Processing Of Al-Cu-Fe Quasicrystalline Single Grains

The phase equilibria of the Al-Cu-Fe quasicrystalline phase (y phase) is complex and conventional crystal growth techniques like the Bridgman and Czochralski methods are not applicable in preparation of large crystals. Large single grains of the y phase been have prepared by either slow cooling or isothermal anneals. In the later technique, arc melted ingots were subjected to either single or multiple heat treatments between 825 and 840°C to encourage grain growth. Following heat treatment, grains of the icosahedral phase are found either as isolated pentagonal-faceted crystals within the ingot or within clusters of intergrown grains. The growth of the large grains is independent of the sample processing history of the sample, is facilitated by the presence of liquid at the growth temperatures and is constrained by the physical dimension of the ingot. The microstructure of both grain types is similar containing a minor quantity (on the order of 5–10 %) of a second phase and a high degree of porosity in the as-grown state. The second phase is usually present as a thin layer between adjacent grains or associated with a pore within a single grain. The grain porosity is distributed throughout the ingot. These defects can be removed through post-growth hot isostatic pressing and anneal treatments.