Origin and depositional environments of source rocks and crude oils from Niger Delta Basin: Carbon isotopic evidence     

《China Geology》2020,3(4):602-610

Thirty-nine crude oils and twenty-one rock samples from Niger Delta Basin, Nigeria have been characterized based on their isotope compositions by elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry. The bulk carbon isotopic values of the whole rock extracts, saturate and aromatic fractions range from –28.7‰ to –26.8‰, –29.2‰ to –27.2 ‰ and –28.5 ‰ to –26.7 ‰, respectively while the bulk carbon isotopic values of the whole oils, saturate and aromatic fractions range from –25.4 ‰ to –27.8 ‰, –25.9 ‰ to –28.4 ‰ and –23.5 ‰ to –26.9 ‰, respectively. The average carbon isotopic compositions of individual alkanes (nC₁₂-nC₃₃) in the rock samples range from –34.9‰ to –28.2‰ whereas the average isotopic values of individual n-alkanes in the oils range from –31.1‰ to –23.8‰. The δ¹³C isotope ratios of pristane and phytane in the rock samples range from –29.2 ‰ to –28.2 ‰ and –30.2 ‰ to –27.4 ‰ respectively while the pristane and phytane isotopic values range from –32.1‰ to –21.9‰ and –30.5‰ to –26.9‰, respectively. The isotopic values recorded for the samples indicated that the crude oils were formed from the mixed input of terrigenous and marine organic matter and deposited under oxic to sub-oxic condition in lacustrine-fluvial/deltaic environments. The stable carbon isotopic compositions were found to be effective in assessing the origin and depositional environments of crude oils in the Niger Delta Basin.  相似文献   

尼日利亚巴古多(Bagudo)锰矿地质特征及找矿标志          下载免费PDF全文

梁树旺 《地质找矿论丛》2022,37(4):501-506

尼日利亚的巴古多(Bagudo)锰矿是近年新发现的具有找矿潜力的沉积变质型锰矿床,位于马如—安卡费金铜铁成矿带的西北缘附近。矿区共圈定了3个锰矿区,锰矿体出露于地表,整体呈NW向或近SN向延伸。矿体中的条纹状锰矿石和块状锰矿石均属低磷中铁中品位的氧化锰-硅酸锰混合矿石,且块状锰矿石锰品位低于条纹状锰矿石。目前矿区的勘查深度主要为-50m以上的浅表部分,深部的勘查工作尚未进行。由于锰矿石具弱磁性,故而高精度磁异常的部位具有找锰意义。  相似文献   

Distribution of heavy metals in soils of Port Harcourt and its environs,Niger Delta,Nigeria   总被引：1，自引：0，他引：1  

Minapuye I Odigi  Lucky O. Ukren  Hycienth O. Nwankwoala 《中国地球化学学报》2011,30(4):415-421

Geochemical evaluation of the distribution of heavy metals in soils of Port Harcourt and its environs in the Niger Delta region is presented in respect of anthropogenic factor and index of geoaccumulation. Sixteen (16) soil samples were collected from two horizons (0-10 cm and 100 cm) from the various grids and analyzed. The geo-chemical analyses showed the vertical and horizontal distributions of heavy metals. The results showed the ranges of the metals determined as follows: Pb (6.86-2.49)×10-6, with an average of 4.63×10-6; Cd (0.05-0.00)×10-6, with an average of 0.02×10-6, As (0.01-0.00)×10-6, with an average of 0.00×10-6. Cu (15.36-10.80) ×10-6, with an average of 13.36×10-6, and V (1.36-0.20)×10-6, with an average of 0.94×10-6. Quantification of the degree of pollution was carried out using anthropogenic factor (AF) and index of geoaccumulation (Igeo). The Igeo values of 0.06, 0.02 and 0.00 for Pb, Cd and As, respectively indicate low-level contamination while Zn (1.14) and V (1.40) show me-dium-level contamination. The sources of contamination are attributed to urbanized anthropogenic activities. The majority of the samples analyzed show that the AF values are less than 1 with the exception of vanadium (V) whose AF values range from 2.73 to 13.60×10-6. Vanadium is more enriched than As, Cd, Pb, and Cu. The order of degrees of anthropogenic contamination and index of geoaccumulation in the soil is V >Zn >Pb >Cu >Cd >AS. Metals were retained near the top soil and their concentrations in the deepest horizons were lower and normal for uncontaminated soils. Metal concentrations in the top soil horizons were significantly related to distance from the industrial and hu-man activities.  相似文献   

Species composition and gear characteristics of the <Emphasis Type="Italic">Macrobrachium</Emphasis> fishery of the Cross River Estuary,Nigeria     

Francis M. Nwosu 《中国海洋大学学报(英文版)》2010,9(1):71-75

The Cross River Estuary, Nigeria, is an important shrimping area for artisanal fishermen of the coastal communities. The multi-species Macrobrachium fishery is exploited with three main gears, namely beach seine, push net and trap. Studies on species composition of this fishery recorded thirteen shrimp species, one swimming crab (Callinectes amnicola) and two fish species (Eleotris sp. and Pellonula leonensis). The shrimp species identified included Macrobrachium macrobrachion (83.39% and 55.69% by number and weight, respectively), M. vollenhovenii (9.66% and 37.18%), M. equidens (3.8% and 2.87%), juveniles-sub-adults of Penaeus notialis (1.11% and 1.3%), M. dux, M. felicinum, Palaemonetes africanus, Palaemon maculatus, Palaemon elegans, Desmocaris sp., Leander sp., Nematopalaemon hastatus and Alpheus pontederiae. While the selectivity index for trap was 0.25, beach seine and push net had a lower index of 0.063. The results present the first comprehensive and representative report for the Estuary shrimp fishery and will assist in the management of the biodiversity of this ecosystem.  相似文献   

Measurements of net all-wave radiation at a tropical location,Ile-Ife,Nigeria     

《Atmósfera》2014,27(3):305-315

Hourly averaged net all-wave radiation data spanning a complete three-year period (2010-2012) at a meteorological station located inside the Obafemi Awolowo University campus in Ile-Ife (7.52° N, 4.52° E), Nigeria is presented in this study to investigate its diurnal and seasonal variations. Using a high-sensitivity four-component net radiometer, the data represents so far the most consistent and detailed information available for a tropical location in West Africa. From the dataset, hourly maxima of the net radiation occurred at 14:00 LT (GMT + 1), whose values increased considerably from 337.6 ± 146.4 Wm⁻² in July, which is the peak of the wet season, to 441.7 ± 82.4 Wm⁻² in March, the end of the dry season. April and October, both of which mark the beginning and end of the raining season at Ile-Ife have recorded the highest values of 584.7 and 612.2 Wm⁻², respectively. There was strong intra/inter-seasonal variation observed in the monthly mean values of the net radiation due mainly to the fluctuations in cloudiness and humidity. In the study area, the data indicated a net radiative heating taking place at the surface, whose annual trend follows a bimodal distribution. The present data supports the results published in earlier studies by other authors.  相似文献   

Interpretation of aeromagnetic data across the central crystalline shield area of Nigeria     

D. E. Ajakaiye  D. H. Hall  T. W. Millar 《Geophysical Journal International》1985,83(2):503-517

Summary. A residual map of the total magnetic field (above 25 000 nT base) is presented for a portion of the central crystalline shield area of Nigeria and overlapping small portions of the Chad basin and the Benue rift (8°30'−12° 00'lat, and 7°−10°30' long). The map (based on a dataset digitized from recently released aeromagnetic sheets of Nigeria) leads to four results. (1) A magnetic boundary, evident on the map, separates the Younger Granite complexes into two groups. The groups are petrologically different, and the boundary may be a fault line with uplift to the south. (2) South of the boundary the map is dominated by a system of sub-parallel anomalies striking NE–SW, possibly representing major tectonic trends, and a set of fractures through which the Younger Granite complexes were intruded. The trend of the system parallels the Benue rift and lineaments in the oceanic crust off West Africa. (3) Negative magnetic anomalies lie over most of the known ring complexes, and over some suspected buried ring complexes and other intrusions. (4) 2½-and 3-D modelling shows that the larger complexes extend to 12 km depth, and the smaller ones to 6 km. They have nearly vertical sides, and magnetization contrasts range from 0.3 to 0.5 A m⁻¹.  相似文献   

Surface water quality evaluation in Odukpani, Calabar Flank, south-eastern Nigeria   总被引：1，自引：0，他引：1  

O. E. Offiong  A. E. Edet 《Environmental Geology》1998,36(3-4):343-348

 The present article is the second in a series of baseline water quality evaluation studies in parts of south-eastern Nigeria. Study results indicate that the water samples from the study are generally acidic, soft and fresh in addition to low sodium and salinity hazard. Regression equations indicate a good positive correlation between conductivity and Na, Ca, Mg and SO₄. Ca-SO₄ and Ca-Cl constitute the major facies in the area. Generally the waters in the area are good for most domestic and agricultural purposes. Received: 14 April 1997 · Accepted: 3 February 1998  相似文献   

Rare-earth elements as source indicators of Pan-African granites from Obudu Plateau,Southeastern Nigeria   总被引：1，自引：1，他引：0  

V. U. Ukaegbu  F. T. Beka 《中国地球化学学报》2008,27(2):130-134

The rare-earth element （REE） concentrations of representative granite samples from the southeast of the Obudu Plateau, Nigeria, were analyzed with an attempt to determine the signatures of their source, evolutionary history and tectonic setting. Results indicated that the granites have high absolute REE concentrations （190×10^-6-1191×10^-6; av.=549×10^-6） with the chondrite-normalized REE patterns characterized by steep negative slopes and prominent to slight or no negative Eu anomalies. All the samples are also characterized by high and variable concentrations of the LREE （151×10^-6-1169×10^-6; av.= 466×10^-6）, while the HREE show low abundance （4×10^-6-107×10^-6; av.=28×10^-6）. These are consistent with the variable levels of REE fractionation, and differentiation of the granites. This is further supported by the range of REE contents, the chondrite-normalized patterns and the ratios of LaN/YbN （2.30-343.37）, CeN/YbN （5.94-716.87）, LaN/SmN （3.14-11.68） and TbN/YbN （0.58-1.65）. The general parallelism of the REE patterns, suggest that all the granites were comagmatic in origin, while the high Eu/Eu＊ ratios （0.085-2.807; av.=0.9398） indicate high fo2 at the source. Similarly, irregular variations in LaN/YbN, CeN/YbN and Eu/Eu＊ ratios and REE abundances among the samples suggest behaviors that are related to mantle and crustal sources.  相似文献   

‘Borehole Race’ and the Dilemma of Governing the ‘Ungoverned’: Understanding the Urban Political Ecology of Groundwater Exploitation in Nigeria     

Emmanuel M. Akpabio  Ekerette S. Udom 《社会与自然资源》2018,31(9):1030-1044

Groundwater exploitation is an essential aspect of the numerous processes of transforming the urban natural environment for human gains. We use the political ecology of borehole exploitation in Nigeria’s urban environment to understand the micro-and macro-level processes mediating the transformation and changes in urban “groundwater scape”. The fieldwork processes depend on field counting of borehole distribution, in-depth and semi-structured interviews, and a review of secondary literatures. We argue that the social and environmental changes arising from the exploitation of groundwater bespeak the active and continual manifestation of the interplay of combustible interests and power friction among institutional agents within the permissible range of the natural environment. Such dynamic power relations engender a pattern of socio-natural transformation consistent with Swyngedouw’s notion of urban metabolism- “a series of interconnected heterogeneous and dynamic but contested and contestable processes of continuous quantitative and qualitative transformations that re-arranges humans and non-humans in new and often unexpected ways”.  相似文献   

The erodibility of some Nigerian soils: A comparison of rainfall simulator results with estimates obtained from the Wischmeier nomogram     

A. Vanelslande  R. Lal  D. Gabriels 《水文研究》1987,1(3):255-265

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