Ni-Cu sulfide mineralization and PGM from the Samapleu mafic-ultramafic intrusion, Yacouba complex, western Ivory Coast

ABSTRACT The mafic-ultramafic Samapleu deposits of the Yacouba complex, which host nickel, copper sulfides, and platinum-group minerals, are located in the Biankouma-Silipou region, western Ivory Coast. These intrusions originate from the mantle and would have been established during the Proterozoic (2.09 Ga) around 22 km deep within the Archean granulites (3.6–2.7 Ga) which at least partially contaminated them. Platinum-group and sulfide minerals from the Samapleu deposits were studied using optical microscopy, scanning electron microscopy, the electronic microprobe, X-ray fluorescence, fire assay, and a Thermo Fisher Scientific Delta S isotope ratio mass spectrometer system. The sulfide mineralization (mainly pyrrhotite, pentlandite, chalcopyrite ± pyrite) is mainly disseminated with, in places, semi-massive to massive sulfide veins. It is especially abundant in pyroxenite horizons with net or breccia textures. The isotopic ratios of sulfur measured from the sulfides (an average of 0.1‰), the R factor (between 1500 and 10,000), and the Cu/Pd ratios indicate a mantle source. Thus, the sulfides would have formed from sulfide liquids produced by immiscibility from the silicate mantle magma under mafic-ultramafic intrusion emplacement conditions and with possible geochemical modification of the magmas by assimilation of the surrounding continental crust. The platinum-group minerals (michenerite, merenskyite, moncheite, Co-rich gersdorffite, irarsite, and hollingworthite) are mainly associated with the sulfide phases. The nature of the platinum-group minerals is indicative of the probable role of late-magmatic hydrothermal fluids during the mineralizing process.

Nano-Micron Exsolved Spinels in Titanomagnetite and Their Implications for the Formation of the Panzhihua Fe–Ti–V Oxide Deposit, Southwest China

The nano-micron exsolved spinels with various mineralogical characteristics in titanomagnetite from Fe–Ti oxide gabbros in the Panzhihua Fe–Ti–V oxide deposit, SW China, have been studied by field emission scanning electron microscopy (FE-SEM) and electron probe microanalysis (EPMA) based on comparisons of physical and chemical conditions at different stratigraphic heights to investigate the compositional inheritance between titanomagnetite and exsolved spinel and further explore the relationship between the morphology and growth of exsolved spinels. Restored chemical data for titanomagnetite combined with evidence from petrography and whole-rock geochemistry imply fractional crystallization of the Panzhihua Fe–Ti–V oxide deposit, where the titanomagnetite of thick massive oxides at the bottom of the No. VIII orebody represents the early crystallizing phase characterized by high temperature and oxygen fugacity. The chemical variation in the exsolved spinel, which has the same trend as the restored composition of titanomagnetite, represents inheritance from the parent rock within the Panzhihua deposit. Exsolved spinel continuously adjusts morphology and grain size to decrease the total energy of the manganate-spinel system from fine-grained spinels parallel to the {100} plane of titanomagnetite to spinels with complex stellate morphology to bulky granular spinels with high degrees of idiomorphism. The unusual multiple magma replenishment during the mineralizing process and at different stratigraphic heights in the Panzhihua intrusion had an important influence on the thermal evolution history of the orebody, resulting in the identifiable spatial distribution patterns of spinel morphology and grain size. Using spinel exsolution as a discriminator for the provenance of magmatic ore deposits may provide intuitive and easy mineralogical evidence to qualitatively discuss the evolution of the metallogenetic environment and the ore-forming conditions for similar large mafic intrusions.

Biomimetic mineralizable collagen hydrogels for dynamic bone matrix formation to promote osteogenesis

Biomimetic mineralizable collagen hydrogels simulate the dynamic bone matrix mineralizing process via the synergy of cellular secretions, and form a microenvironment that promotes osteogenesis.

Graftonite in phosphatic iron formations associated with the mid-Proterozoic Gamsberg Zn-Pb deposit, Namaqua Province, South Africa

Granular aggregates of fine-grained graftonite (Fe,Mn,Ca)3(PO4)2 and intergrown wolfeite (Fe,Mn)2(PO4)(OH) occur in amphibolite-facies metamorphosed iron formations associated with the Gamsberg Zn-Pb deposit, South Africa. To date, these minerals were believed to have limited parageneses, being essentially restricted to granitic pegmatites and iron meteorites. This paper is the first report of the occurrence of graftonite and wolfeite in a regionally metamorphosed, iron formation-hosted setting. The aggregates are found together with Mn- and Pb-rich apatite and calcian pyromorphite in a pristine unit of almost pure chemical precipitates, the origin of which is intimately linked to the base-metal mineralizing process. Evidence from Gamsberg supports previous studies conducted on pegmatite-hosted graftonites that a simple host rock mineralogy and geochemical prerequisites, such as high activities of Fe, Mn, Ca and a deficiency in F, exert a dominant control on the stabilization of these minerals. However, in a marine sedimentary environment, significant concentrations of phosphorus have to be precipitated to prevent stabilization of all the phosphorus as fluorapatite. The paucity of graftonite in such settings suggests that the combination of these requirements is only rarely achieved.

Fluid circulation in the Apuane Alps core complex: evidence from extension veins in the Carrara marble

In the Apuane Alps (AA) metamorphic core complex, syn-metamorphic mineral deposits are mainly restricted to extensional shear zones in the Lower Plate Palaeozoic basement. By contrast, the extension structures at upper levels, such as the detachment fault, that are typically the seat of fluid circulation and mineralization in other core complexes, are barren in the AA. Extension veins hosted by the Jurassic Carrara marbles are among the few examples of (minor) mineralization located in the upper levels of the AA core complex. Calcite–dolomite geothermometry and fluid inclusion data suggest that the mineralizing process in these veins began under pressure (P)-temperature (T) conditions close to the metamorphic peak (about 400°C, 3 kbar). Progressive cooling and mixing between metamorphic and late stage meteoric fluids were probably responsible for most of the mineral deposition. Batches of relatively saline fluids presumably resulted from interaction with evaporitic levels located along the detachment fault. In agreement with previous estimates, fluid inclusion constraints on the P—T synmetamorphic path of the AA suggest a relatively rapid cooling of the core complex as a result of uplift. However, the maximum estimated geothermal gradient (about 35°C/km) is considerably lower than in other core complexes, where large-scale hydrothermal circulation was associated with extension and uplift. Hence, in the AA, fluid circulation at shallow levels and mixing among fluids of different origin were not favoured, thus precluding the formation of mineral deposits along major extensional structures.

The attachment of teeth in Lophius

The mandibular teeth in Lophius present the two kinds of attachment typical of predatory bony fish: ankylosis and fibrous hinge. Light microscopy and microradiography showed that ankylosis, occurring through a gradual transition between basal dentine, attachment bone, and bone proper, is the most achieved type encountered in fish. The ligament of the hinge appeared to consist of collagen fibres exclusively. No elastic components were found. Ankylosis and hinged attachment in Lophius are merely levels in the mineralizing process of collagen fibres. The resilience of the dental apparatus is enhanced by the freely movable bone and cartilage of the jaws and pharyngeals, which allow ingestion of large prey, making up for the disadvantages of nonocclusion and reduced bony architecture.

III. Observations on the changes which have taken place in some antient alloys of copper. By John Davy, M. D. F. R. S. In a letter to Sir Humphry Davy, Bart. Pres. R. S

Permit me through you to lay before the Royal Society, the results of some experiments and observations on the incrustations of certain antient alloys of copper, which I trust may not he undeserving of notice, whether considered in connexion with the arts of Antient Greece, or in relation to the slow play of chemical affinities acting during a long period of time. I shall commence with the most interesting object that I have examined since I have been in the Mediterranean, for which I am indebted to His Excellency Sir Frederick Adam, His Majesty’s Lord High Commissioner in the Ionian islands. This is a bronze helmet of the antique Grecian form, recently found in a shallow part of the sea, between the citadel of Corfu, and the village of Castrades. Both internally and externally it is partially encrusted with shells, and a deposit of carbonate of lime. The surface of the helmet generally, both under the incrustation, and where freed from it, is of a variegated colour, mottled with spots of green, dirty white, and red. On minute inspection, the green and red patches exhibit a crystalline structure, and the red very distinctly; and on examining them with a lens, they were found to be formed of octohedrons of the red oxide of copper, intermixed with crystals of the same form of metallic copper. These crystals are most distinct at the surface; they even adhere to the calcareous crust, and may be detached with it, pre­senting well-formed facets towards the part from which they have been separated. Chemical examination shows that they are actually composed of metallic copper, without the least tarnish, and of the pure ruby protoxide of copper; and that the green rust consists principally of carbonate and sub-muriate of copper, and the dirty white chiefly of oxide of tin. The mineralizing process (if I may be allowed the expression) which has produced these new combinations, in general has penetrated very little into the substance of the helmet. The incrustation and rust removed, the metal is found bright beneath; in some places considerably corroded, in others very slightly, It proves on analysis to be copper alloyed with 18.5 per cent, of tin. Its colour is that of our common brass, and it possesses a considerable degree of flexibility.