Use of Geochemical Fossils as Indicators of Thermal Maturation: An Example from the Anambra Basin, Southeastern Nigeria

Organic geochemical studies and fossil molecules distribution results have been employed in characterizing subsurface sediments from some sections of Anambra Basin, southeastern Nigeria. The total organic carbon (TOC) and soluble organic matter (SOM) are in the range of 1.61 to 69.51 wt% and 250.1 to 4095.2 ppm, respectively, implying that the source rocks are moderately to fairly rich in organic matter. Based on data of the paper, the organic matter is interpreted as Type III (gas prone) with little oil. The geochemical fossils and chemical compositions suggest immature to marginally mature status for the sediments, with methyl phenanthrene index (MPI-1) and methyl dibenzothiopene ratio (MDR) showing ranges of 0.14–0.76 and 0.99–4.21, respectively. The abundance of 1,2,5-TMN (Trimethyl naphthalene) in the sediments suggests a significant land plant contribution to the organic matter. The pristane/phytane ratio values of 7.2–8.9 also point to terrestrial organic input under oxic conditions. However, the presence of C27 to C29 steranes and diasteranes indicates mixed sources—marine and terrigenous—with prospects to generate both oil and gas.

Determination of Provenance and Tectonic Settings of Niger Delta Clastic Facies Using Well-Y, Onshore Delta State, Nigeria

Provenance analysis serves to reconstruct the predepositional history of a sediment/sedimentary rock. This paper focuses on the reconstruction of the provenance and tectonic settings of the Niger delta clastic facies using geochemical approach. The main types of geochemical tests include major, trace, and rare earth element (REE) tests. Twenty-one samples of shales and sandstones units were purposely collected from a depth between 1160 and 11,480 m, grinded, pulverized, and sieved with a <75 μm. About 5 g was packed and sent to Acme analytical Laboratory Ltd., Vancouver, Canada. The analyses were carried out by both induced coupled plasma-mass spectrometry (ICP-MS) and induced coupled plasma-emission spectrometry (ICP-ES). Bulk-rock geochemistry of major oxides, trace elements, and rare earth elements was utilized for the provenance and tectonic setting determination. Based on the discrimination diagram for major oxides, the probable provenance of the south eastern Delta clastic sediments was mainly of the active continental margins. The bivariate plots of La versus Th, La/Y versus Sc/Cr, and Ti/Zr versus La/Sc and the trivariate plots of La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 are all plotted on the fields of active continental margin sediments which is consistent with the known actively opening of a failed arm of triple junction. The trace elements and REE analysis indicates that they are virtually Fe-rich, lithic/quartz arkosic sandstones. The normalizing factors used for the REE are Wakita chondrite. Their rare earth elements (REE) pattern displays high light REE/heavy REE (LREE/HREE) ratio, flat HREE, and a significant negative Eu anomaly which correlate well with the UCC and PAAS average composition. The source area may have contained felsic igneous rocks.

Nature of C-(A)-S-H Phases Formed in the Reaction Bentonite/Portlandite

Reactions between bentonite/montmorillonite and portlandite have been studied in the context of the engineered barriers of a purpose built repository for the deep geological disposal of spent fuel and high-level radioactive wastes. Portlandite was selected as the representative material of cement leaching in the early alkaline stage expected in a repository when conventional Ordinary Portland Cement (OPC) is used. Eight different batch experiments were performed for a reaction time near to two months, including bentonite or montmorillonite at montmorillonite/portlandite molar ratios of 2 : 1 and 3 : 1 under hydrothermal conditions. Temperatures of reactions were maintained constant at either 60 or 120°C. Calcium silicates hydrates with limited substitution of Al for Si (C-(A)-S-H phases with Al/Si <0.3) were formed with different structures and compositions as a function of the reaction conditions. Orthorhombic 11 Å-tobermorite-type phase was detected in experiments at 120°C while a more disordered monoclinic tobermorite formed at 60°C. These results are useful for the interpretation of experimental data in more complex experiments using concrete or cement pastes and bentonite, where C-(A)-S-H phases of variable compositions can precipitate, in addition to the characteristic cement hydrates and other secondary minerals carbonates.

Lead Immobilization and Hydroxamate Ligand Promoted Chloropyromorphite Dissolution

The immobilization of lead, a major environmental contaminant, through phosphate amendments to form the sparingly soluble lead phosphate mineral chloropyromorphite [Pb5(PO4)3] (CPY) is an effective in situ strategy for soil remediation. An important question is the effect of microbial processes on this remediation. Here, we investigate the role of the microbial siderophore ligand desferrioxamine-D1 (DFO-D1) and its analog acetohydroxamic acid (aHA) in CPY lability using pH-dependent batch dissolution kinetics and model calculations. Both (0.01) M aHA and (0.00024) M DFO-D1 are similarly effective and enhance lead release from CPY by more than two orders of magnitude at pH > 6 compared to in the absence of ligands. This is consistent with model calculations of pH-dependent (aqueous) complexation of lead with hydroxamate ligands. More importantly, pH-dependent ligand sorption is predictive of its ligand promoted dissolution behavior. Our results suggest that organic ligands can significantly increase CPY lability at alkaline pHs in soils and sediments and that addition of P amendments to immobilize Pb as CPY may only be successful at acid pHs.

Electron Microscopic Studies of Ilmenite from the Chhatrapur Coast, Odisha, India, and Their Implications in Processing

Ilmenite from the Chhatrapur coast, Odisha, India, was studied using optical microscope, X-ray diffraction, particle size analysis, and electron microprobe to decipher their micromorphology, texture(s), and elemental composition. The micromorphological features by electron microscope indicate that weathering processes such as mechanical and chemical, affected the placer heavy mineral ilmenite. These detrital ilmenites contain TiO2 in the range of 50.25% to 55.41% and FeO 42.72% to 49.99% in addition to Al2O3, MgO, MnO, CaO, Na2O, Cr2O3, NiO, ZnO, ZrO2, V2O5, and HfO2 (0 to 0.034%). Ti/(Ti + Fe) ratio in the ilmenite varied from 0.413 to 0.5, which indicates the effect of weathering/oxidation confirming microscopic observations. All the results revealed that these ilmenite grains were derived from the gneissic/granitic, basic and high grade metamorphic rocks, belonging to the Eastern Ghats Group of the Precambrian complex of coastal Orissa.

Geochemical Association of Ni 2+ , Zn 2+ , Pb 2+ , Ag + , Cu 2+ , and Co 2+ Ions in Natural Pyrite

The natures of competitive adsorption of six metal ions on the natural pyrite surface have been studied with an objective to provide strong foundations towards mode of association/occurrence of trace elements on pyritic surface. Some parameters, for instance, adsorption edge, mechanism, correlation coefficient, monolayer coverage, pH, and thermodynamic parameters, have been considered here. The significant results are the order of increasing trend of adsorption edges which has been found to be Pb2+ < Cu2+ < Ni2+ < Zn2+ < Co2+ < Ag+. Nonuniformity in variation of adsorption edge of a particular metal ion in presence of a second metal ion in solution is evident from the study. However, in case of Ag2+ and Co2+ ions two adsorption edges are observed. These variations have been explained based on the formation of hydroxo complexes which are pH dependent. The competitive monolayer coverage of each metal ion as a function of pH has shown variation in the extent of adsorption. Computed higher correlation coefficient in a binary system indicates retardation in adsorption of metal ion in presence of a second metal ion. Further the adsorption of metal ions on pyrite surface showed exothermic processes due to the spontaneous nature at low temperature. Our study has strongly revealed promising adsorbent characteristics of natural pyrite with considerable geochemical and environmental implications.

Electro-Thermal and Semiconductivity Behaviour of Natural Sintered Complex Carbonate Ore for Thermo-Technological Applications

The polymetal (Zn, Pb, Fe, Ca, Mg, Cd, Ba, Ni, Ti, and SiO2) complex Umm-Gheig carbonate ore is subjected to sintering treatment at 573, 773, 973 and 1273 K respectively for four hours. Chemical, spectral, X-ray and differential thermal analyses are applied for the native ore as well as for the samples preheated and sintered. The current versus applied DC voltage (I–V) characteristics, bulk density (Db), percent shrinkage (%S), activation energy (Ea) and energy gap (Eg) are established for the sintered ore. The electrical conductivity σ, thermal conductivity (K) and thermoelectric power coefficient α have been investigated as a function of applied temperature for the sintered ore materials. The electrical conduction is mainly achieved by free electrons near or in conduction band or n-type. As the sintering temperature (Ts) increases the conduction of the ore is also increased due to the recombination process taking place between the electrons and holes. Electrons hopping between Fe2+ and Fe3+ are the main charge carriers. The formation of Fe3O4 at high sintering temperature acts as an active mineralizer, thus inducing an increased degree of crystallinity and a more ordered crystal structure is produced.

Spatial Distributions of Humic Substances and Evaluation of Sediment Organic Index on Lake Dalinouer, China

The aim of this study is to examine and interpret the spatial distribution of sedimentary humic substances in Lake Dalinouer. Humic substances in sediments were analyzed separately in different fractions: humins (HM), humic acid (HA), fulvic acid (FA), and different forms of organic carbon. The results showed that total organic carbon (TOC) contents varied from 7.25 to 65.54 g kg−1 with a mean of 36.37 ± 17.74 g kg−1. It was found that high TOC concentrations were at lake’s center and low TOC concentrations occurred at the estuary of inflows. Different redox conditions caused by water depth were of the most important factors which might influence TOC contents. Concentrations of HM, HA, and FA in sediments were detected in range of 6.40–58.16 g kg−1, 0.27–3.50 g kg−1, and 0.27–4.26 g kg−1, respectively. Of them, HM was the dominant form and accounted for 74–94% of TOC and 80–90% of humus. Organic Sediment Index (OSI) was used to assess the organics accumulation, and the value of OSI ranged from 0.001 to 0.30, which indicated that Lake Dalinouer was relatively clean. The relative high degree of humidification was found in the eastern of lake, where it should be taken into consideration seriously.