High MnO Contents Research Articles

Growth of Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal boule with MnO content gradient along growth direction using continuous-feeding Bridgman method and MnO content dependence of ferroelectric and piezoelectric properties

A Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal boule was grown by the continuous-feeding Bridgman method to investigate the relationship between the MnO content and the properties such as piezoelectric coefficient and mechanical quality factor. Using high MnO content ceramics as an initially loaded material and low MnO content ceramics as a continuous-feeding material, a suitable composition distribution was achieved for the investigation (i.e. MnO content monotonically decreases from 0.45 to 0.29 wt% while the content of other elements are stable along the growth direction). The evaluation of the boule revealed that the MnO content greatly affects the properties despite the small variation in MnO content (0.16 wt%). The highest mechanical quality factor Qm31 of 900 along with a high piezoelectric constant d 33 of 840 pC/N was obtained at 0.35 wt% MnO. The data obtained during this investigation will be beneficial to determine a suitbable MnO content for building a practical piezoelectric device.

Effect of ferrochromium (FeCr) and ferroniobium (FeNb) alloys on inclusion and precipitate characteristics in austenitic stainless steels

Lab-scale alloying experiments were carried out by first adding commercial low-carbon ferrochrome (LCFeCr) alloys and then adding ferroniobium (FeNb) alloys in 316-grade austenitic stainless steel in this study. The inclusion and precipitation characteristics in LCFeCr and FeNb were evaluated as well as in a 316 austenitic stainless steel after the alloy additions by using two- and three-dimensional characterization methods in combination with thermodynamic calculations. The results showed that MnCr2O4 spinels and pure Al2O3 were the main types of inclusions in LCFeCr alloys, while pure TiOx, Al2O3 inclusions and complex TiOx-Al2O3 aggregates were mainly found in FeNb alloys. After the addition of LCFeCr alloy to the steel, the SiO2 contents in liquid inclusions decreased to some extent, while more inclusions containing higher MnO contents were observed. Some MnCr2O4 spinel inclusions can be reduced by Si in steel and form liquid inclusions. Some MnCr2O4 spinel and Al2O3 inclusions from LCFeCr alloy can remain in the steel melt, which decreased the steel cleanliness. After the addition of FeNb alloy, pure TiOx inclusions present in this alloy can hardly be found in the steel melt. The inclusion types in steel were not changed so much but high Nb-containing phases were found around the inclusions and coarse Laves phases were formed in the matrix. Overall, this work aims to understand the impurity particle behavior during the alloying process when using ferroalloys to produce high-performance stainless steels.

Multi-origin authigenic calcite controlled by the depositional environment and fluid−rock interactions in the Triassic siliciclastic strata, Junggar basin, NW China

Authigenic calcite records geologic fluid activities in sedimentary rocks, and its origin varies with changing sedimentary environments and fluid−rock interactions. This study investigated authigenic calcite with multiple origins in the Triassic siliciclastic strata of the petroliferous Mahu Sag, Junggar Basin, NW China. Detailed core logging was followed by lithological studies including optical, scanning electron and cathodoluminescence microscopic observations together with geochemical analyses of major elements and stable carbon and oxygen isotopes. The results show that there are three stages of calcite in the Baikouquan Formation with significantly differential MnO contents (average = 0.94%, 3.87%, 7.84%, respectively) and obviously negative δ13C values (−57.5‰ to −13.9‰, VPDB). It reflects the evaporation during deposition, and oxidation of hydrocarbon in oxidizing diagenetic environment. Extensive feldspar dissolution promotes the precipitation of late-stage calcite. There are two stages of calcite in the Karamay Formation and Baijiantan Formation. The positive correlation of their MgO and FeO contents reflects the alteration of volcanic materials in the strata. For the early-stage calcite, the low MnO contents (average = 0.50% and 0.61%) and positive δ13C values (>−10‰), demonstrate the paleo-meteoric water input. While the high MnO contents (average = 4.59%) and negative δ13C values (−25‰ to −10‰) of the late-stage calcite in the Karamay Formation indicate hydrocarbon charging and subsequent decarboxylation of organic acid, accompanied by feldspar dissolution. The late-stage recrystallization calcite of the Baijiatan Formation inherits the MnO and carbon isotopic characteristics of the early-stage calcite. This study shows that authigenic calcite is an effective recorder of sedimentary environment and fluid−rock interactions in siliciclastic strata. It enhances the heterogeneity of siliciclastic strata and is beneficial to hydrocarbon accumulation in lithological reservoirs.

Age, petrogenesis, and tectonic setting of granitic gneiss and amphibolite from the Weizigou gold deposit, Heilongjiang Province, NE China: Constraints from geochronology and geochemistry

The Weizigou gold deposit is located in the western Jiamusi Massif, Northeast China. Gold mineralization is hosted in the amphibolite, which intruded the granitic gneiss. Although the deposit shows similarities to iron-oxide–copper–gold deposits, the detailed ore-forming process remains uncertain. To determine the formation age, petrogenesis, and tectonic setting of the granitic gneiss and amphibolite, LA–ICP–MS zircon, titanite, and monazite UPb dating, whole-rock major- and trace-element analyses, and LA–ICP–MS in situ zircon Hf isotope analyses were conducted on samples from these rocks. The granitic gneiss yielded two age populations of 951–882 Ma, and ca. 500 Ma, with a monazite UPb concordia age of 501.5 ± 5.1 Ma. The amphibolite yielded a crystallization age of 292 Ma, consistent with the results for magmatic titanite UPb dating, and a metamorphic age of 272–258 Ma. The granitic gneiss contains typical aluminum-rich minerals, such as garnet and muscovite, mean SiO2 = 73.31 wt%, and molar ratio Al2O3/(CaO + K2O + Na2O) values of 1.02–1.07, indicating an S-type granite protolith. The amphibolite belongs to the tholeiitic basalt series and has low SiO2 and high MnO contents. These results, together with εHf(t) values and two-stage model ages ranging from −9.5 to 2.3 and − 0.3 to 5.7, and from 2010 to 1659 Ma and from 1331 to 947 Ma, respectively, allow us to infer that the parental magmas of the granitic gneiss and amphibolite were derived from the partial melting of Paleoproterozoic lower crust and the partial melting of metasomatized depleted mantle, respectively. The granitic gneiss is characterized by positive Th and Hf anomalies, and negative Nb, Ta, Sr and Ti anomalies, whereas the amphibolite is enriched in K, Rb, and depleted in Ba, Nb, Ti, and Zr. These geochemical features suggest that the S-type granite was formed in an active continental margin during the Neoproterozoic and underwent granulite-facies metamorphism during the early Paleozoic. The protolith of the amphibolite was gabbro that formed in an extensional setting (e.g., a backarc basin) associated with westward subduction of the Paleo-Pacific oceanic plate beneath the eastern Jiamusi Massif during the early Permian. The gold mineralization can most likely be attributed to contact metasomatic metamorphism of gabbro during the middle–late Permian.

Mineralogical and Re-Os isotope constraints on fluid– and melt–rock interactions and the origin of mantle peridotites from the Amdo ophiolite, northern Tibet

Ophiolites from the Bangong–Nujiang Suture Zone in the central part of the Tibetan Plateau represent relics of Neo-Tethyan oceanic lithosphere. Here we present the results of a detailed mineralogical and Os isotopic study of mantle peridotites of the Amdo ophiolite, which provide new insights into the origin of the peridotites and their diverse melt/fluid–peridotite reactions. The Amdo ophiolite comprises mantle peridotites, mafic–ultramafic cumulates, massive gabbros, diabases, and pillow basalts. The mantle peridotites are mainly refractory harzburgites, composed of olivine (Ol, 65%–85%), orthopyroxene (Opx, 12%–35%), clinopyroxene (Cpx, <4%), and Cr-spinel (Cr-Spl, ~2%). Most olivine grains (Ol-I) are protogranular, locally enclosed in orthopyroxene and Cr-spinel, and have high Fo values (91.1–92.9) and NiO contents (0.29–0.44 wt%), typical of residual origin. In contrast, interstitial olivines (Ol-II) have low Fo values (67.2–84.7) and NiO contents (<0.05 wt%), but extremely high MnO contents (0.28–1.65 wt%), suggesting metasomatism by carbonate-bearing fluids. Hypidiomorphic-granular clinopyroxene grains (Cpx-I) have high Mg# values (~94.5) and low Al2O3 (average 1.26 wt%) and Na2O (<0.19 wt%) contents, typical of residual phases after melting. However, clinopyroxene coronas (Cpx-II) around orthopyroxene have higher Na2O contents (0.24–1.06 wt%), indicative of mantle metasomatism by melts. Osmium isotopic compositions in the harzburgites vary from subchondritic to suprachondritic (187Os/188Os ratios: 0.11716–0.13284). The subchondritic Os isotopic compositions (0.11716–0.12367) correspond to TRD model ages of 0.76–1.56 Ga, suggesting Mesoproterozoic mantle depletion events. On the other hand, several harzburgites with low Os (0.29–0.86 ppb) and suprachondritic 187Os/188Os ratios (0.12823–0.13284) reflect the overprinting of original Os budgets and Os isotopic compositions by percolating melts or fluids. The combined mineralogical and Os isotopic compositions suggest that the Amdo peridotites represent a mixture of ancient subcontinental lithospheric mantle (SCLM) and Mesozoic oceanic lithosphere, which were subsequently infiltrated by carbonate-bearing fluids and silicate melts in a supra-subduction zone.

Geology, geochemistry and genesis of the Godar Sabz Mn deposit in the Baft region, Iran

The Godar Sabz Mn deposit is located in the Nain-Baft ophiolitic belt in the northeast margin of the Sanandaj-Sirjan zone, Iran. The Nain-Baft back-arc extensional basin resulted from the subduction of the oceanic crust of Neo-Tethys under the southern margin of the Iranian Plate in the Early Cretaceous and hosts several mineral deposits, including volcanogenic massive sulfide, chromite, and Mn deposits. The mineralization in the Godar Sabz Mn deposit occurred predominantly as stratabound, massive, banded, layered, and lenticular orebodies in radiolarian cherts within Baft ophiolitic complex. The main ore minerals are pyrolusite, braunite, with minor amounts of todorokite. The significant geochemical features of the Godar Sabz ores, such as the high MnO content (21.82–80.65 wt%, average = 64.91 wt%), high Mn/Fe (average = 278), Si/Al ratios (average = 92.6), high Ba contents (average = 4495.6 ppm), the low average contents of Cu (81.8 ppm), Ni (106.2 ppm), Co (29.4 ppm), LREE > HREE, and trace element discrimination diagrams indicate a hydrothermal-exhalative source for mineralization. Chondrite-normalized REE patterns of studied ores have negative Ce and slightly positive Eu anomalies, which are similar to hydrothermal Mn deposits. The REE patterns of Mn ores coincide with basaltic lavas, suggesting that the Mn-mineralization in the Godar Sabz deposit was genetically related to the leaching of basaltic lavas. The Godar Sabz Mn deposit has many similarities with the main characteristics of the hydrothermal exhalative Mn deposits, including tectonic setting, host rock type, the morphology of orebodies, ore textures, mineralogy, and chemical features of ores.

Crystallization conditions and compositional variations of silicate and sulfide minerals in the Pb-Zn skarn deposits, Biga Peninsula, NW Turkey

The Biga Peninsula (NW Turkey) is an important sector of the Tethyan Metallogenic Belt. In addition to Au and Ag, this region hosts several Pb, Zn, Cu, Fe, and Mo deposits. Pb-Zn skarn mineralizations in the Biga Peninsula (Biga Pb-Zn skarn) are bounded by carbonate lenses in the metamorphic rocks and localized along the regional faults and at the contact between carbonate units and igneous-metamorphic rocks. The primary ore minerals are galena, sphalerite, chalcopyrite, pyrite, arsenopyrite, magnetite, and hematite. Ore-bearing altered rocks are composed primarily of calc-silicate alteration minerals, including both prograde (grossular-andradite garnets and johannsenite-hedenbergite pyroxenes) and retrograde (epidote, chlorite, quartz, and calcite) assemblages. The garnet composition is a solid solution with <96% andradite and 1.4% to 94.4% grossular content. Some garnet grains exhibit zonings because of fluctuations in the content of Al3+ and Fe3+. Mn/Fe ratios are high, and the outermost grains have a high MnO content, up to 3 wt%. The pyralspite content is <10 wt%. The proportions of johannsenite and hedenbergite in clinopyroxenes range from 0.35 to 94.69 mol% and 2.13 to 77.90 mol%, respectively. Clinopyroxenes have high Mn/Fe values, with Mn content up to 10 wt%. The epidote-group minerals with a high Al3+ and Fe3+ content belong to the epidote-clinozoisite series (Ep37-21Czo78-63Pie1-0). Mineral chemistry data indicate that Biga Pb-Zn skarn deposits and distal Pb-Zn skarn deposits throughout the world have similar characteristics. The abundance of graphite in the metamorphic host rocks and the andradite-hedenbergite content of the skarns imply that the studied mineralizations were formed under reducing conditions. The ranges of crystallization depth and pressure values calculated from the chemistry of garnet-clinopyroxene pairs are 1.3–1.6 km and 10–12 MPa, respectively. Because these values are less than those of plutons hosting the Biga Pb-Zn skarn deposits, the mineralizations likely formed in the distal zones of plutons.

Renewable agaric-based hierarchically porous cocoon-like MnO/Carbon composites enable high-energy and high-rate Li-ion batteries

Hierarchical pore structures in the composite electrode materials can offer greater accessibility to active sites for the lithium ions, shorter ion diffusion distances and quicker lithium ion diffusion, which can enable the high-rate and high-energy Li-ion batteries (LIBs). In this work, hierarchically porous cocoon-like MnO/C composites (PCM) have been prepared using natural agaric as raw materials via a sustainable and facile method associated with the hydrothermal and annealing treatment. The as-prepared porous PCM composites show a high reversible capacity of 981 mAh g−1 at 0.1 A g−1 and remain an high discharge capacity of 640 mAh g−1 after 900 cycles at 1 A g−1. Even at the high current density of 5 A g−1, the electrode can still deliver a high capacity of 440 mAh g−1. More importantly, the high MnO content (∼78 wt %) and micron-scale structure of PCM composite greatly improve the high specific capacity and tap density of electrode materials, and help to meet the requirements for practical application. Therefore, such novel preparation strategy of composite electrode from agaric also develops a new route to fully utilize the biomass resources for high-performance LIBs and other energy storage devices.

Geochemical Characteristics of Limestone of Wonosari-Punung Formation, Gunungkidul Regency, Yogyakarta, Indonesia

DOI: 10.17014/ijog.5.2.179-197A geochemical study was carried out to determine the geochemical characteristics of limestone in Wonosari-Punung Formation, and to suggest its depositional conditions and the source of rare earth elements. The study was conducted at Ponjong Area, Gunungkidul Regency, Daerah Istimewa Yogyakarta, Indonesia. White limestone which contains more abundant calcite is characterized by the highest CaO concentration. Red limestone which is associated with impure minerals such as siderite, rodochrosite, hematite, and titanite is typified by depleted CaO but higher SiO2, Fe2O3, MnO, and TiO2 concentrations. Grey limestone characterized by depleted CaO and higher MnO contents is considered to be influenced by the presence of impure minerals of manganite (Mn2O3.H2O) and/or pyrolusite (MnO2). Depletion of Sr concentration in the coloured limestone indicates that the diagenetic process increases from the white limestone to the coloured limestone. The process possibly occurred post-deposition of the limestones. The limestones show positive Mn* values (2.46 - 2.95) and authigenic U values (0.89 - 3.38) that suggest an oxidative environment. The Ce/Ce* values (0.57 - 0.80), Eu/Eu* values (1.04 - 1.88), high Y/Ho ratio, and low LaN/YbN ratio are indications that the rare earth elements in the limestones were derived from terrigenous materials. The positive Eu anomaly and enrichment of Cr and Mn of the limestones are indications of hydrothermal fluid activity taking place in the studied area. Based on the geochemical characteristics of the Punung-Wonosari limestones, the depositional environment and the source of rare earth elements of the limestones were therefore influenced by a combination of hydrothermal fluid activity with small amount of terrigenous material input and post depositional diagenetic process.

The Formation Mechanism of Mn–Al–O Inclusions in Fe–Cr–Mn Stainless Steel during Continuous Casting

The formation mechanism of Mn–Al–O inclusions in Fe–Cr–Mn stainless steel during continuous casting is investigated by industrial trials and thermodynamic calculation. The morphology, composition, and size distribution of inclusions in steel specimens are analyzed by scanning electron microscopy and energy dispersive spectroscopy. The main inclusions change from spherical Ca–Si–O and Ca–Si–Mn–O inclusions during LF refining to Mn–Al–O inclusions in continuous casting slab and hot‐rolled sheet. The size of most Mn–Al–O inclusions containing high MnO content is smaller than 4 µm. The formation of these inclusions is consistent with thermodynamic calculation, which indicates that MnO and Al2O3 inclusions are formed during continuous casting process. The calculation results of MnO and Al2O3 inclusions growth shown that the size of MnO inclusion (4 µm) is much larger than that of Al2O3 inclusion (0.4 µm) at the end of solidification, which also accords with the characteristics of inclusions in continuous casting slab and hot‐rolled sheet.

Carbon Nanotubes–MnOx Nanocomposite as Support for Iron‐Based Catalysts for the Fischer–Tropsch Synthesis of Liquid Fuels

AbstractA facile one‐pot hydrothermal method is developed to synthesize a series of carbon nanotubes–manganese oxide nanocomposites (CNTs–MnOx) with different morphologies and Mn valence states. These nanocomposite materials are then utilized as catalyst supports in iron‐based Fischer–Tropsch synthesis (FTS) for the production of liquid fuels. Experimental results indicate that Fe/CNTs‐K‐190 (iron catalyst supported on the CNTs treated with KMnO4 at 190 °C) and Fe/CNTs‐KU‐190 (iron catalyst supported on the CNTs treated with KMnO4 and urea at 190 °C) display higher FTS activity than the Fe/CNTs‐K‐110 (iron catalyst supported on CNTs treated with KMnO4 at 110 °C) and Fe/CNTs‐KU‐110 (iron catalyst supported on CNTs treated with KMnO4 and urea at 110 °C). This might be due to the weak metal–support interaction and high MnO content, and the poorer stability than Fe/CNTs‐K‐110 and Fe/CNTs‐KU‐110 catalysts with nanosheet morphology might be related to the structural collapse of the nanocubes or nanorods due to MnO evolution during the FTS process. The CNTs–MnOx nanocomposite‐supported iron FTS catalysts in particular display unparalleled high C5+ selectivity (over 90 %) and very low CH4 selectivity (below 4.6 %). The unique CNTs–MnOx nanocomposites may open a new window for the understanding, design, synthesis, and optimization of iron catalysts toward high‐efficiency transport fuel production.

Thermodynamic Calculation and MnS Solubility of Mn-Ti Oxide Formation in Si-Mn-Ti Deoxidized Steel

Mn-Ti oxides in Si-Mn-Ti deoxidized steels after cooling in the furnace were investigated. The composition and morphology of inclusions were analyzed by using FE-SEM with EDS. Mn-Ti oxides were found to be effective sites to induce intragranular ferrite formation. The thermodynamic calculation was employed to interpret the critical condition for Mn-Ti oxide formation. Mn-Ti oxide formation was controlled not only by Mn and Ti content, but also by total oxygen content in steel. When the Mn and Ti contents were around 1.5% and 0.005%–0.01%, respectively, Mn-Ti oxide could form as the total oxygen content was 0.001%–0.002%. The experimental results were in good agreement with thermodynamic calculation results. Also, MnS solubility was examined in Mn-Ti oxide inclusion system. With an increase of MnO content in Mn-Ti oxide, MnS solubility in the oxides increased. MnS precipitation benefited from high MnO content in Mn-Ti oxide.

Mineralogy and petrography of a kimberlite-picrite dike in the northwestern Urik-Iya Graben, the eastern Sayan region

Mica kimberlite and alkali picrite were identified in the northwestern Urik-Iya Graben of the eastern Sayan region. Typomorphism of Cr-diopside and high-Cr (up to 55.22 wt % Cr2O3) spinel from kimberlite of the Bushkanai dike indicate that the melt was generated in the mantle, composed of spinel peridotite. The high content of Cr-spinel (45–55 wt % Cr2O3) microlites in the groundmass of kimberlite and small amounts of ulvospinel and titanomagnetite in the absence of perovskite testifies to the diamond potential of this kimberlite. Picroilmenite, manganoilmenite with an anomalously high MnO content (11.37–17.78 wt %), and barium titanate with (wt %) 62.21 TiO2, 0.61 Cr2O3, 15.89 FeO, 4.05 MnO, 1.71 CaO, and 11.13 BaO close in composition to a new mineral species from the Murun pluton were identified in the groundmass for the first time. Kimberlite from the Bushkanai dike belongs to the Zolotitsa low-Ti geochemical type of kimberlites derived from the slightly enriched lithospheric mantle EM1. The distribution of trace elements, including REE, in picrite from the same dike corresponds to the slightly depleted asthenospheric mantle. Different mantle sources of kimberlite and picrite from the same dike indicate that these rocks are related to independent melts rather than to products of fractionation of a common parental alkaline ultramafic magma.

An Environmental Application of Regional Geochemical Mapping in Understanding Enzootic Geophagia of Calves in the Reivilo Area, South Africa

A specific enzootic form of geophagia (the deliberate ingestion of soil) occurs in young cattle and sheep in restricted areas of the Barkley-West, Postmasburg and Vryburg Districts of the Northern Cape- and North West Provinces of the Republic of South Africa. It results in severe, subacute to chronic hepatitis and jaundice, with a high mortality rate in untreated cases. An association between the disease and high concentrations of manganese in soils was shown since all the affected farms are situated on outcrops of the Reivilo Formation of the Campbell Rand Subgroup, which consists mainly of manganiferous dolomite. Furthermore high concentrations of manganese were found in the analysis of liver specimens from affected calves and the characteristic microscopic pathological changes in the liver could be induced experimentally in a calf and lamb by oral administration of manganese sulphate. The highest incidence of geophagia occurs at 7 to 14 days, whereas calves older than about 2 months are rarely affected. The symptoms usually start with intermittent, progressive geophagia, followed by constipation, dehydration and death within ca. 7–10 days in untreated cases. Young calves and lambs display an insatiable appetite for soil and sometimes lick iron poles. The treatment of calves by the parenteral injection of commercial iron-dextran- and vitamin B12 preparations at 1 to 2 days after birth, and at 14 days of age, at the registered therapeutic doses, appeared to have a marked preventative effect on the occurrence of geophagia and its complications. Regional geochemical maps show a northeast–southwest trending anomaly in MnO, Zn and Pb, visually correlating with the distribution of the affected farms. Anomalously high distributions of Pb and Zn are also spatially related to the Pering (Pb,Zn) Mine. In this study, two farms were selected for comparative purposes. Gam, a farm situated on the Reivilo Formation of the Campbellrand Subgroup was chosen where a high incidence of geophagia occurred, as well as the farm Holpan on the Lyttelton Formation of the Malmani Subgroup where the problem was not known to be present. The farm Holpan was chosen as a control area, and is situated close to an old manganese mine on dolomite with a high MnO content. Geographically, Holpan is situated in an area with a high rainfall, with leaching and the formation of deep red soils on the dolomite, together with a hilly relief and low soil pHH2O. Gam is situated in an area with lower rainfall, where precipitation would be less than evapotranspiration. The dolomite of the Malmani Subgroup and the Reivilo Formation are significantly different in their soil geochemistry. The MnO, Fe2O3T and Co contents are significantly higher in the soils of the Malmani Subgroup than in the Reivilo Formation. The MnO, Zn and Pb contents on Gam are higher than on Holpan, whereas the Fe2O3T and Co contents are lower. Soil on Holpan contains iron-minerals such as haematite, while no iron minerals were detected in the soils of Gam. The concretions, found in the soils on both farms, differs remarkably in iron-contents. Concretions on both farms have similar high concentrations of MnO, whereas the FeO content are low for the concretions on Gam and high for Holpan. Preliminary comparative analytical results of the colostrum, sampled from cows with new born calves within three days of birth, do not entirely reflect the soil geochemistry of the different farms. Whereas the soils on Gam have higher MnO, Zn and Pb, and lower Fe2O3T and Co than Holpan, the colostrum produced on Gam has lower Mn, Fe and Co than on Holpan. The Pb and Zn concentrations in the colostrum on both farms do not differ significantly. The comparative regional geochemical soil data, together with the colostrum data, suggest that young calves on the farm Gam probably suffer from Fe and Co deficiency. Conversely, it was illustrated that the Fe and Co content in the soils are high and the Fe is abundant in the concretions on the farm Holpan. These findings, together with the apparent absence of geophagia at Holpan, as well as the observed effect of iron and cobalt supplementation in the prevention of geophagia on the farm Gam, suggests an association of geophagia with iron and cobalt deficiencies on the farm Gam.

Thermodynamics of MnO, FeO, and phosphorus in steelmaking slags with high MnO contents

The thermodynamics of managanese oxide and iron oxide and the phosphate capacity of CaO-SiO2-MnO-Fe t O-P2O5-MgOsat slags with high MnO contents relevant to the smelting of MnO ores in steelmaking were investigated. Previous data were limited to about 5 pct MnO, whereas in this study MnO contents up to 25 pct were studied. The activity of MnO showed positive deviation from ideal behavior and increased with basicity, while that of Fe t O decreased with basicity. This is reflected in that the manganese distribution ratio at a given Fe t O content decreases with basicity and high Mn in the metal is favored by high basicity. CaF2 additions up to 4 pct did not affect the activities of MnO and Fe t O. The activity coefficient of P2O5 decreases and the phosphate capacity increases with basicity. There was not adverse effect of high MnO contents on the dephosphorizing abilities of the slags.

Petrological and geochemical evidence for diagenesis of inoceramid bivalve shells in the Plentzia Formation (Upper Cretaceous, Basque–Cantabrian Region, northern Spain)

Inoceramid bivalve shells from the upper part of the Plentzia Formation (middle Cenomanian to lower Santonian) of the Basque-Cantabrian Region were tested for post-depositional, diagenetic alteration. From field relations, petrography and cathodoluminescence (CL) observations, the coarsely prismatic calcitic ostracum of the shells seem to be most affected by chemical diagenetic processes, but without textural changes in the prismatic microstructure, with the exception of some selective silicification by quartzine-lutecite rims at the margin of the shells and small euhedral calcite crystals (1-2 μm across) infilling possible organic filament ducts. CL is a bright red-yellowish colour owing to a relatively high MnO content, 0.28% vs. 0.03% (wt) in the whole rock. The δ 1 8 O isotopic values obtained from the shell prisms range from −1.76‰ to −4.70‰ [Pee Dee Belemnite (PDB)], with a mean value of −3.03±0.69‰ (PDB). The clearest evidence of diagenetic alteration is inferred from both whole-shell geochemistry and microprobe analysis. In fact, a complementary zonation in the distribution of ‘diagenetic tracers’ can be detected from internal to external surfaces of inoceramid shells, together with a rare earth element (REE) enrichment in the shells which have lighter δ 1 8 O values. Comparison between REE mean values of the marly host rock and those of inoceramid shells reinforces the idea of chemical diagenetic alteration of shell carbonate.

Petrogenesis of the gabbros from Mt. St. Hilaire, Quebec, Canada

AbstractMt. St. Hilaire occurs as a small funnel‐shaped intrusion in the Monteregian petrographic province of Quebec and consists of alkali gabbros and later nepheline syenites. Based on field relations, petrography, and geochemistry, five types of gabbro are recognized. In order of intrusion these are: leucogabbro, foliated gabbro, kaersutite‐biotite gabbro, kaersutite gabbro, and a gabbro‐melagabbro series. Based on analyses of the early‐forming ilmenite‐titanomagnetite, the gabbros crystallized under high fO2 conditions which lead to subsequent crystallization of olivines with high MnO contents. Fractionation of ilmenite and titanomagnetite was a major control on the Ti and A[TV]concentrations in the clinopyroxenes. Plagioclase compositions in the gabbros became richer in Ab contents in the sequence gabbro‐melagabbro to leucogabbro. Whole‐rock analyses suggest that the parental magma of alkali basaltic composition was fairly evolved prior to emplacement. Lack of olivine in the cumulate gabbro‐melagabbros and low Ni and Cr in all gabbros may reflect either extreme olivine fractionation and/or a very low olivine content in the source material for these basalts. Differentiation of the gabbros occurred both pre‐ and post‐emplacement, probably by a process of crystal‐liquid fractionation at depths between 3‐5 and 8 km. This is in accordance with geophysical measurements for other Monteregian intrusions. A model is presented for the mechanism of emplacement.

Ulv�spinel in native iron-bearing assemblages and the origin of these assemblages in basalts from Ovifak, Greenland, and B�hl, Federal Republic of Germany

Euhedral crystals of ulvospinel are found in many of the native-iron-bearing xenoliths from the basalt of Buhl near Kassel (West Germany) and Ovifak on Disko Island (West Greenland). The typical assemblage of these xenoliths at both localities is: native Fe, troilite, cohenite, ulvospinel, ilmenite, olivine, and plagioclase, as well as silicate glass containing droplets of former Fe and troilite melt. The ulvospinel subsolidus textures and intergrowths also indicate identical cooling histories for the xenoliths in both cases. Ulvospinel crystallized after the formation of iron, but still above the Fe-FeS eutectic at 988° C. A subsequent strong drop in oxygen fugacity revealed partial breakdown of ulvospinel according to the reaction $${\text{Fe}}_{\text{2}} {\text{TiO}}_{\text{4}} {\text{ = FeTiO}}_{\text{3}} {\text{ + Fe + }}\tfrac{{\text{1}}}{{\text{2}}}{\text{O}}_{\text{2}} $$ . Microprobe analyses of a Buhl xenolith indicate that ulvospinel contains up to 4.7 w.t.% MnO, while olivine compositions correspond to Fa64–74Fo12–24Te12–15. The entire xenolith contains 1.9 w.t.% MnO. This fact, together with the geological evidence and the occurrence of corroded quartz relicts within some of the xenoliths provides clear evidence for reduction under near-surface conditions in a blast-furnace-like process. The reducing agent was coal from the Tertiary seams cut by the erupting basalt, while the xenolith source material most probably was spherosiderite, which is very common in the coals and would explain the high MnO content. Consequently, the presence of cohenite is not necessarily an indicator of high pressure. The analogies between the Buhl and Ovifak localities and their xenoliths strongly suggest a similar formation through near surface reduction and not derivation from the mantle.

Mineralogical aspects of ores Sediments, ores and metamorphism: new aspects

Recent years have witnessed the discovery of new large stratabound deposits of base metals, tungsten and uranium, as well as intensified research efforts in the investigation of known occurrences. Three problems are of particular interest: (1) The response of stratabound metal concentrations to varying degrees of metamorphism, and the limits of ‘survival’ of their geometrical and compositional parameters, (2) the distribution of manganese in the ore environment of sulphide deposits, and (3) the participation of elements not traditionally associated with the sedimentary cycle, such as tungsten, in the formation of stratabound deposits. The northwestern Cape Province, S. Africa, has been selected for an initial study of these aspects because of its wealth in large and economically significant base metal concentrations. These occur in volcano-sedimentary successions of probable Kheis age (2600 Ma) which have been metamorphosed during the 1200 Ma Kibaran orogeny. Metamorphism was of amphibolite facies grade (600-700 °C, 3- 4.5 kbar) in the east (deposits of Aggeneys and Gamsberg) and of granulite facies grade (800-1000 °C, 6—8 kbar) in the west (deposits of the O’okiep Copper District, including the Wolfram Schist). In amphibolite facies terrain, the stratabound nature of orebodies is generally well preserved, although complicated by several phases of folding. Electron probe analyses reveal high MnO-contents in silicates of the ore environment (garnets 20 %, pyroxene 5 %, stilpnomelane 11 %). These findings correlate with recent data from the Broken Hill, N.S.W. deposits (Stanton 1976) and from the Red Sea (Cronan et al. 1976). Their potential value lies both in the fields of ore genesis and of exploration geochemistry. Major concentrations of copper ore in transgressive ‘ noritoids ’ are limited to the granulite facies terrain of the O’okiep Copper District. Their isotopic, geochemical and petrological parameters favour crustal rather than mantle origin. A source bed model deriving the noritoids by partial melting of Cu-bearing members of the stratigraphic sequence, is thus proposed. Small tungsten deposits have in the past been mined in the granulite facies terrains of Namaqualand: concordant quartz-ferberite veins occur in the ' Wolfram Schist ’ and have previously been interpreted as hydrothermal and pegmatitic. Their distinct limitation to a specific stratigraphic horizon as well as new quantitative data on the age and grade of metamorphism in the area suggested a review of this genetic concept. The recent discovery of stratabound tungsten mineralization in Austria, Norway and Rhodesia, and the recognition of the sedimentary origin of the Sundong, S. Korea, deposit further stimulated these considerations. The Namaqualand tungsten deposits are thus interpreted as the product of granulite-facies metamorphism of sedimentary scheelite concentrations. These investigations necessitate the combination of many geoscientific disciplines, including field work, structural geology, geophysics, petrology, isotopic studies, geochemistry, ore microscopy and experimental mineralogy, here termed ‘the comprehensive geoscience approach’. This clearly requires team work; the author has had the privilege of closely cooperating with groups led by Professor T. N. Clifford (Witwatersrand University) and Mr J. Marais (O’okiep Copper Company Limited).

Magnetic Ceramics: V, Magnetic Properties of Square Loop Ferrites Within the System MgO‐MnO‐Fe2O3

Thirteen compositions within the center of the system MgO‐MnO‐Fe2O3 were investigated because of their rectangular hysteresis‐loop characteristic. Initial permeabilities were measured, and Bm, BT, Hc, and R8m were obtained from quasi‐static hysteresis loops. High MgO content was found to be detrimental to the magnetic properties and to impair the loop rectangularity. The highest hysteresis‐loop squareness ratio, R, 8m, was found in a composition with high Fe2O3 content, and the lowest coercive force, Hc, was found in a composition with high MnO content.