Hindawi Publishing Corporation Journal of Geochemistry Volume 2014, Article ID 960139, 13 pages http://dx.doi.org/10.1155/2014/960139 Research Article Determination of Provenance and Tectonic Settings of Niger Delta Clastic Facies Using Well-Y, Onshore Delta State, Nigeria S. O. Oni, A. S. Olatunji, and O. A. Ehinola Department of Geology, University of Ibadan, Ibadan 200284, Oyo State, Nigeria Correspondence should be addressed to S. O. Oni; talk2nicesam@hotmail.com Received 25 August 2014; Revised 8 November 2014; Accepted 10 November 2014; Published 28 December 2014 Academic Editor: Franco Tassi Copyright © 2014 S. O. Oni et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Provenance analysis serves to reconstruct the predepositional history of a sediment/sedimentary rock. his paper focuses on the reconstruction of the provenance and tectonic settings of the Niger delta clastic facies using geochemical approach. he 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 �m. About 5 g was packed and sent to Acme analytical Laboratory Ltd., Vancouver, Canada. he 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. he bivariate plots of La versus h, La/Y versus Sc/Cr, and Ti/Zr versus La/Sc and the trivariate plots of La-h-Sc, h-Sc-Zr/10, and h-Co-Zr/10 are all plotted on the ields of active continental margin sediments which is consistent with the known actively opening of a failed arm of triple junction. he trace elements and REE analysis indicates that they are virtually Fe-rich, lithic/quartz arkosic sandstones. he normalizing factors used for the REE are Wakita chondrite. heir rare earth elements (REE) pattern displays high light REE/heavy REE (LREE/HREE) ratio, lat HREE, and a signiicant negative Eu anomaly which correlate well with the UCC and PAAS average composition. he source area may have contained felsic igneous rocks. 1. Introduction he samples were taken from Y-ield in Niger delta. he coordinates of the study area were not given because of the proprietary nature of the data but the estimated location is shown in Figure 1. he Niger delta extends from about longitudes 3∘ E and 9∘ E and latitudes 4∘ 30� N to 5∘ 21� N. he Niger delta is located in the southern part of Nigeria. he Niger delta is situated in the Gulf of Guinea, which northwards merges with the structural basin in the Benue and middle Niger terrain holding thick marine paralic and continental sequence. he onshore portion of the Niger delta province is delineated by the geology of southern Nigeria and southwestern Cameroon. he Niger delta was formed as a result of basement tectonics related to the crustal divergence during the late Jurassic to cretaceous continental riting of Gondwanaland that led to the separation of South American African continents. he Niger delta is large arcuate to lobate tropical constructive wave of dominated type. Active deposition is presently occurring simultaneously in these depobelts under luviatile conditions where there is interplay between terrestrial and marine inluences. he Niger delta basin to date is the most proliic and economic sedimentary basin in Nigeria. It is an excellent petroleum province. he Niger delta is situated in the Gulf of Guinea and extends throughout the Niger delta province. From the Eocene to the present, the delta has prograded southwestward, forming depobelts that represent the most active portion of the delta at each stage of its development [1]. hese depobelts form one of the largest regressive deltas in the world with an area of some 300,000 km2 [2], a sediment volume of 500,000 km3 [3], and a sediment thickness of over 10 km in the basin depocenter [4]. he Niger delta province contains only one identiied petroleum system [2, 5]. his system is referred to here as the tertiary Niger delta (Akata-Agbada) petroleum system. 2 Journal of Geochemistry 5.0 4.0 Passive margin 3.0 Oceanic island arc 2.0 1.0 0.0 −1.0 CIA −2.0 −3.0 Active continental margin −4.0 −5.0 −6.0 −4.0 −2.0 −8.0 −7.0−6.0 0.0 2.0 4.0 −8.0 Discriminant −9.0 −10.0 Discriminant function 2 9∘ 8∘ 7∘ 6∘ −10.0 5∘ 4∘ 0 (km) 50 100 ∘ 5E Series 1 ∘ 6E Study area Eocene recent cycle with approximate coast lines Campanian-Paleocene cycle ∘ 7E ∘ 8E Albian-Santonian cycle Metamorphic basement complex (precretaceous) Volcanics Figure 2: he plot of discriminant 2 against discriminant 1; the discriminant function diagram for sandstones (ater [8]), showing ields for sandstones from passive continental margins, oceanic island arcs, continental island arcs, and active continental margins. he CIA at the centre represents continental island arc. 1.0 Oceanic arc Figure 1: Generalized and simpliied geological map of Niger delta basin as obtained from http://www.intechopen.com. TiO2 (%) he maximum extent of the petroleum system coincides with the boundaries of the province. he minimum extent of the system is deined by the areal extent of ields and contains known resources (cumulative production plus proved reserves) of 34.5 billion barrels of oil (BBO), 93.8 trillion cubic feet of gas (TCFG), and 14.9 billion barrels of oil equivalent (BBOE) [6]. Currently, most of this petroleum is in ields that are onshore or on the continental shelf in waters less than 200 meters deep and occurs primarily in large, relatively simple structures. Among the provinces ranked in the U.S. Geological Survey’s World Energy Assessment [7], the Niger delta province is the twelth richest in petroleum resources, with 2.2% of the world’s discovered oil and 1.4% of the world’s discovered gas [6]. 0.8 0.6 Continental arc 0.4 Active continental margin 0.2 Passive margin 0 0 4 8 12 Fe2 O3(total ) + MgO (%) 16 20 Figure 3: Bivariate plot of TiO2 versus (Fe2 O3 + MgO) diagrams for sandstones (ater [8]). he ields are oceanic island arc, continental island arc, active continental margin, and passive margins. 3. Results 2. Materials and Methods 3.1. Tectonic Settings of Niger Delta Based on Major Oxides. See Table 1 and Figures 2 and 3. 2.1. Sample Collection and Analysis. Twenty-one core samples were collected and subjected to inorganic analysis which includes major oxides, trace elements, and rare earth element. he samples are irst dried. To avoid contamination, the samples are then washed in deionized water and dried again. Ater preparation, the samples are grinded and pulverized. Sample reduction entails comminuting by sieving or crushing and grinding. Standard procedure at most laboratories is to sieve soils and sediments to <75 �m. he samples are thus sieved with <75 �m. his is because sample preparation must reduce the sample volume to a size suitable for analysis yet preserves the bulk geochemical signature of the larger body. About 3 g of the pulverized sample was then packed in a suitable bag and sent to Acme labs, Vancouver, Canada, for analysis. 3.2. Results and Discussion. Knowledge of the tectonic setting of a basin is important for the exploration of petroleum and other resources as well as for paleogeography. Some authors have described the usefulness of major element geochemistry of sedimentary rocks to infer tectonic setting based on discrimination diagrams (e.g., [8, 9]). his is because plate tectonics processes impart distinctive geochemical signature to sediments in two separate ways. Firstly, tectonic environments have distinctive provenance characteristics and secondly they are characterized by distinctive sedimentary process. Bhatia [8] proposed major element geochemical criteria to discriminate plate tectonic settings for sedimentary basins from identiied well-deined sandstone suites. He compiled Journal of Geochemistry 3 Table 1: Table of the eleven major element oxides in percentages. Samples depth Lithology 1160–1180 1560–1580 1960–1980 2960–2980 3960–3980 4560–4580 5460–5480 5760–5780 6160–6180 7060–7080 7260–7280 7560–7580 7760–7780 7960–7980 8060–8080 8160–8180 8560–8580 8960–8980 10,360–10,380 11,060–11,080 11,460–11,480 Sand Sand Sand Shale Shale Shale Shale Shale Shale Sand Sand Sand Shale Shale Shale Sand Sand Shale Shale Shale Shale FeO % 0.5 0.4 1.0 2.2 4.3 3.9 3.6 4.7 3.4 2.9 2.8 3.2 4.3 2.8 2.9 3.0 3.8 4.7 2.7 7.7 6.1 Fe2 O3 % 0.5 0.5 1.1 2.4 4.7 4.4 4.0 5.2 3.8 3.2 3.2 3.6 4.8 3.1 3.2 3.4 4.2 5.2 3.0 8.6 6.8 CaO % 1.1 0.6 0.8 0.4 0.4 0.4 0.2 0.2 0.7 0.7 0.7 0.6 0.8 0.8 1.4 3.1 1.7 0.9 0.5 0.7 0.5 P2 O5 % 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.1 0.1 0.2 0.1 0.1 0.1 0.1 0.0 0.1 0.1 0.1 0.1 0.2 0.1 the average chemical compositions of medium- to inegrained sandstones (e.g., arkose, greywacke, lithic arenite, and quartz arenite) and modern sands from various regions of the world and used these average values to propose discrimination diagrams. Bhatia [8] used these diagrams to infer the tectonic settings of ive Paleozoic sandstone suites of eastern Australia. He then proposed discriminant functions (functions 1 and 2) by using 11 major element oxides (shown in Table 1) as discriminant variables to construct a territorial map for the tectonic classiication of sandstones. Discriminant scores of functions 1 and 2 [8] were calculated from the unstandardized function coeicient and the actual abundance of major element oxides in the average. Bhatia [8] considered the tectonic setting of sandstones that he studied and generally concluded that sedimentary basins may be assigned to the following tectonic settings based on the 11 major oxides (Table 1): (1) oceanic arc: fore arc or back arc basins, adjacent to volcanic arcs developed on oceanic or thin continental crust; (2) continental island arc: inter arc, fore arc, or back arc basins adjacent to a volcanic arc developed on a thick continental crust or thin continental margins; (3) active continental margin: Andean type basin developed on or adjacent to thick continental margins and strike-slip basins also developed in this environment; (4) passive continental margin: rited continental margins developed on thick continental crust on the edges MgO % 0.1 0.1 0.1 0.2 0.4 0.4 0.1 0.1 0.2 0.1 0.1 0.2 0.6 0.2 0.6 1.6 0.4 0.4 0.3 0.9 0.5 TiO2 % 0.1 0.1 0.1 0.3 0.7 0.7 0.3 0.8 0.6 0.3 0.3 0.3 0.6 0.3 0.2 0.3 0.2 0.8 0.4 0.8 0.9 Al2 O3 % 1.7 1.5 1.7 5.1 11.1 13.5 3.8 6.5 11.0 3.1 4.4 5.4 9.0 5.4 3.5 4.8 3.9 11.7 6.0 13.5 14.6 Na2 O % 0.2 0.4 0.6 1.8 2.6 3.3 4.6 4.5 3.7 6.0 6.8 6.0 1.9 4.7 1.0 0.7 1.0 0.9 1.3 1.2 1.1 K2 O % 0.2 0.3 0.6 1.7 3.0 3.1 2.9 2.9 2.8 4.3 4.7 4.5 3.1 3.9 1.7 1.7 1.6 2.5 2.8 2.7 2.1 MnO % 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 SiO2 % 95.5 96.0 93.8 85.8 72.7 70.1 80.4 74.9 73.8 79.2 76.9 76.0 74.7 78.6 85.5 81.2 82.9 72.7 82.8 63.6 67.2 Total % 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 of continents and sedimentary basins on the trailing edge of continent. hese diagrams are used for the recovered sediments from well-Y, southwestern Niger delta in order to determine the tectonic setting of the area in Figure 2. Bhatia [8] proposed a discrimination diagram based on a bivariate plot of irst and second discriminant functions of major element analysis. he sandstones were chosen to represent the four diferent tectonic settings, assigned on the basis of comparison with modern sediments as shown in Figure 2. When this diagram is used, samples with high content of CaO as carbonate must be corrected for carbonate content. his discrimination diagram is used to classify the suites of various samples into diferent tectonic settings. he discriminant functions are discriminant function 1: −0.0447SiO2 − 0.972TiO2 + 0.008Al2 O3 − 0.267Fe2 O3 + 0.208FeO − 3.082MnO + 0.140MgO + 0.195CaO + 0.719Na2 O − 0.032K2 O + 7.510P2 O5 + 0.303; discriminant function 2: −0.421SiO2 + 1.998TiO2 − 0.526Al2 O3 − 0.551Fe2 O3 − 1.610FeO + 2.720MnO + 0.881MgO − 0.907CaO − 0.177Na2 O − 1.840K2 O + 7.244P2 O5 + 43.57 (ater [8]). he discriminant plot is shown in Figure 2. Modern sandstones from oceanic and continental arcs and active and passive continental margins have variable composition, especially in their Fe2 O3 + MgO, Al2 O3 /SiO2 , K2 O/Na2 O, and Al2 O3 /(CaO + Na2 O) contents. Bhatia [8] 4 Journal of Geochemistry 1000.0 Passive continental margin 10.0 1.0 0.1Oceanic island arc 0.0 54.0 64.0 67.2, 0.3Active continental margin 74.0 84.0 94.0 104.0 SiO2 Figure 4: he plot of log K2 O/Na2 O-SiO2 discrimination diagrams of Roser and Korsch [9] for sandstone mudstone suites showing the diferent tectonic settings. Discriminant function 2 Log K2 O/Na2 O 100.0 Felsic Provenance 3.3. Provenance or Source Rock Determination Using Major Oxides. Discrimination diagram proposed by Roser and Korsch [9] distinguish the sources of the sediments into four provenance zones, maic, intermediate, felsic, igneous provenances (Figure 5). he analysis was based on the chemical analyses in which Al2 O3 /SiO2 , K2 O/Na2 O, and Fe2 O3 +MgO proved the most valuable discriminant. he plot of the two discriminant functions is based upon the oxides of Ti, Al, Fe, Mg, Ca, Na, and K and most efectively diferentiates between the provenances in Figure 5. he plot is based on the discriminant functions 1 and 2 which are ratio for raw plots. he plots using the raw oxides (Figure 5) revealed that the sediments in the well were sourced from felsic and very little from quartzoze sedimentary provenances. he problem of biogenic CaO in CaCO3 and also biogenic SiO2 is circumvented by using ratio plots in which the discriminant functions are based upon the ratios of TiO2 , Fe2 O, MgO, Na2 O, and K2 O all to Al2 O. he formula for the raw oxides used in Figure 5 is given as discriminant function 1: −1.773TiO2 + 0.607Al2 O3 + 0.76Fe2 O3(total) − 1.5MgO + 0.616CaO + 0.509Na2 O − 1.224K2 O − 9.09; Intermediate 1.9 0 Quartzoze Maic −8 −9.2 −8 used this chemical variability to discriminate between diferent tectonic settings on a series of bivariate plots. Figure 3 shows the discrimination diagrams for sandstones (ater [8]) based upon a bivariate plot of TiO2 versus (Fe2 O3 + MgO). he ields are oceanic island arc, continental island arc, active continental margin, and passive margins. Roser and Korsch tectonic settings determinant diagrams are as follows: the three tectonic settings, passive continental margin PM, active continental margin ACM, and oceanic island arc (ARC) are recognized on the K2 O/Na2 O-SiO2 discrimination diagrams of Roser and Korsch [9] for sandstone mudstone suites as shown in Figure 4. Where sediments are rich in carbonate components, the analysis was recalculated as CaCO3 -free. Failure to do this will shit samples to lower SiO2 values and from passive margin ield into volcanic arc ield. he other data values are plotted in active continental margin but could not show on the negative side of the vertical logarithmic scale (Figure 4). −2 −4 8 5.6 −2 −0.6 0 3.1 Discriminant function 1 8 9 Figure 5: Discriminant function diagram for the provenance signatures of sandstone mudstone suites using major elements ater Roser and Korsch [9]. he ields were dominantly maic, intermediate, and felsic igneous provenances. Also shown is the ield with quartzoze sedimentary provenance. discriminant function 2: 0.445TiO2 + 0.7Al2 O3 − 0.25Fe2 O3(total) − 1.142MgO + 0.438CaO + 1.475Na2 O + 1.426K2 O − 6.861. Also the discrimination diagram for detrital grains ater Grigsby [10] using detrital grains as a provenance indicator is shown in Figure 6. Grigsby proposed that the provenance source for sedimentary grains can be determined by the plot in Figure 6. he trace element oxide distributions as plotted in Figure 7 generally show positive correlation with Al2 O3 , relecting association of most elements with the clay fraction. SiO2 content has a strong negative correlation with Al2 O3 relecting that much of SiO2 is present as quartz grains. It also conirms the quartz enrichment in the sand fraction. With the exception of SiO2 , Na2 O, and CaO, the other oxides broadly follow the trend of positive correlation with (increasing as Al2 O3 increases) indicating that they are associated with micaceous and/or clay minerals in the sediments. Plotting graphs of major oxides versus Al2 O3 (Figure 7) variation diagrams, Fe2 O3 , MnO2 , MgO, TiO2 , FeO, P2 O5 , and K2 O, show positive correlation. he observed depletion in Na2 O and CaO (negative correlation) indicates that the studied sediments have sufered from weathering and recycling [11, 12]. Generally, Ca, Na, and K contents are controlled by feldspars and thus strong depletion in CaO and Na2 O further suggests destruction of plagioclase due to chemical weathering in the source or during transport (Table 2). 3.4. Trace Elements. Discrimination diagram to describe source rock composition is the Zr/Ti-Nb/Y discrimination diagram ater Winchester and Floyd [13] and the h/Sc-Z/Sc diagram ater McLennan et al. [14]. Journal of Geochemistry 5 Table 2: h/Sc-Zr-Sc, La, Co, h, and Sc values. Samples depth 1160–1180 1560–1580 1960–1980 2960–2980 3960–3980 4560–4580 5460–5480 5760–5780 6160–6180 7060–7080 7260–7280 7560–7580 7760–7780 7960–7980 8060–8080 8160–8180 8560–8580 8960–8980 10,360–10,380 11,060–11,080 11,460–11,480 Average value Lithology Sand Sand Sand Shale Shale Shale Shale Shale Shale Sand Sand Sand Shale Shale Shale Sand Sand Shale Shale Shale Shale h/Sc 2.8 2.4 2.0 1.7 1.4 1.2 1.5 1.3 0.9 1.4 0.6 0.7 1.3 0.8 1.9 2.2 1.5 1.6 2.5 1.1 0.8 1.5 Zr/Sc 36.6 29.5 27.5 28.3 23.0 17.2 37.3 40.1 20.6 40.9 37.3 27.0 23.6 26.3 38.3 36.3 21.5 24.8 37.5 19.6 17.5 29.1 1.0000 MgO/(MgO + Al2 O3 ) 0.9000 Intermediate 0.8000 0.7000 0.6000 Maic plutonic 0.5000 0.4000 0.3000 0.2000 Felsic (plutonic) 0.1000 30.0000 25.0000 20.0000 15.0000 10.0000 5.0000 0.0000 0.0000 TiO +V2 O3 MgO/(MgO + Al2 O3 ) Figure 6: Discrimination plot of TiO2 + V2 O3 versus MgO/(MgO + Al2 O3 ) for detrital grains ater Grigsby [10]. Floyd and Winchester, in a series of papers (e.g., [13, 16– 18]), speciically addressed the identiication of rock type. he most commonly used approach is their Zr/TiO2 -Nb/Y diagram [13], which has subsequently been updated using a much larger dataset and statistically drawn boundaries La 8.9 8.1 9.2 16.7 30.1 31.7 9.1 9.6 23.2 8.9 4.6 6.4 16.1 5.9 8.1 17.9 11.5 26 18.6 37.6 29.2 Co 1.9 1.4 3.9 13 13.2 12.9 9 17.4 9.7 11.7 12 19.2 13.2 29.4 11.5 12.4 41.4 8.5 11.4 21.4 22.4 h 3.4 2.6 3.2 5.5 9.9 10.4 3.8 5.8 6.8 2.6 1.7 2.2 6.6 2.2 3.4 6.4 3.8 10 6.6 10.1 9 Sc 1.2 1.1 1.6 3.2 7.1 8.6 2.5 4.4 7.5 1.9 2.7 3.1 4.9 2.9 1.8 2.9 2.5 6.3 2.6 9.3 10.9 Zr/10 4.39 3.24 4.4 9.04 16.3 14.8 9.33 17.65 15.48 7.78 10.07 8.36 11.56 7.63 6.9 10.52 5.38 15.6 9.76 18.23 19.08 by Pearce [19]. his diagram is essentially a proxy for the TAS classiication diagram, where Nb/Y is a proxy for alkalinity (Na2 O + K2 O) and Zr/TiO2 is a proxy for silica. Nb/Y increases from subalkalic to alkalic compositions and Zr/TiO2 increases from basic to acid compositions. h/Sc-Z/Sc diagram ater McLennan et al. [14] plot gives insight in the degree of fractionation of the source rocks which is expressed in h/Sc ratio. Furthermore, this plot describes the degree of sediment recycling that is expressed in the Zr/Sc ratio. Increased recycling concentrates zircon in sedimentary rocks (increase in Zr concentration) at the expense of volcanic material contained in the detritus (decrease in Sc-concentrations). he plot of h/Sc versus Zr/Sc diagram is shown in Figure 8, describing most of the sediments found in the zone of recycling and zircon concentration of upper continental crust. Trace elements such as La, h, Zr, Nb, Y, Sc, Co, and Ti have been recognized as valuable provenance signatures for shales, arenites, and wackes [15, 20, 21]. Bivariate plots of Ti/Zr-La/Sc as well as triangular La-h-Sc, h-Sc-Zr/10, h-Sc-Zr/10, and h-Co-Zr/10 plots are useful means to discriminate the tectonic settings of clastic sedimentary rocks [15]. Distinctive ields for four environments are recognized on the trivariate plots of La-h-Sc, h-Sc-Zr/10, and hCo-Zr/10. On La-h-Sc plot, the ields of active continental margin sediments and passive continental margin sediments 6 Journal of Geochemistry Titanium oxide TiO2 16 14 12 10 8 6 4 2 0 Magnesium oxide MgO 20 y = 15.419x − 0.0404 R2 = 0.8463 y = 2.9156x + 5.628 R2 = 0.0656 15 10 5 0 0 0.2 0.4 0.6 0.8 1 Potassium oxide K2 O 16 14 12 10 8 6 4 2 0 1 2 3 4 2 4 6 8 10 Manganese oxide MnO2 18 16 14 12 10 8 6 4 2 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 y = −1.6841x + 8.1044 R2 = 0.0647 0 0.5 1 1.5 2 2.0 4 6 10 8 2.5 16 14 y = 56.849x + 2.1434 R2 = 0.3403 12 10 8 6 4 2 0 0 0.05 0.1 0.15 0.2 Sodium oxide Na 2 O y = −0.1004x + 6.9868 R2 = 0.0025 0 1 2 3 4 5 6 7 8 Silica oxide SiO2 Calcium oxide CaO 16 14 12 10 8 6 4 2 0 2 16 14 12 10 8 6 4 2 0 y = 185.81x + 1.8806 R2 = 0.4864 0 1.5 Phosphorus oxide P2 O5 y = 1.81x − 0.0903 R2 = 0.658 0 1.0 y = 2.0126x − 0.0903 R2 = 0.658 0 5 Iron III oxide Fe 2 O3 18 16 14 12 10 8 6 4 2 0 0.5 Iron II oxide FeO 18 16 14 12 10 8 6 4 2 0 y = 0.948x + 4.3228 R2 = 0.0808 0 0.0 3 3.5 16 y = −0.4227x + 40.228 14 R2 = 0.7614 12 10 8 6 4 2 0 20 40 60 −2 0 80 100 120 Figure 7: Covariation of Al2 O3 versus major elements for the 11 major oxides. here is a positive correlation of Al2 O3 with almost all the major elements; SiO2 shows negative correlation. overlap, but the h-Sc-Zr/10 and h-Co-Zr/10 show complete separation: h-Co-Zr/10 discrimination diagrams for greywackes in Figure 11 (ater [15]). La-h-Sc discrimination diagram for greywackes in Figure 9; Also the various plots that indicate the felsic provenance of the samples are as shown in Figures 12 and 13 (Table 4). h-Sc-Zr/10 discrimination diagrams for greywackes in Figure 10; 3.5. Various Trace Elemental Ratios Used in Evaluating Provenance and Depositional Conditions. Elevated values of Journal of Geochemistry 7 Th 3 2.5 Upper continental crust Th/Sc 2 Zone of sediment recycling 1.5 and zircon concentration 1 0.5 Lower continental crust 0 0 10 20 30 40 C 50 Zr/Sc D B Figure 8: h/Sc versus Zr/Sc diagram ater McLennan et al. [14], relecting reworking and upper crust input. A · Co Zr/10 Figure 11: h-Co-Zr/10 plot showing the provenance of the sediments to be active continental margin (ater [15]). 1 La 0 0.8 0.2 C 0.6 10.0 0.4 1.0 0.4 0.6 B Felsic Th/Co D 0.1 0.2 Basic rocks 0.8 A 0 Th 1 Sc 1 0.8 0.6 0.4 0.2 0 Th C D A Sc 0.1 1 10 La/Sc Figure 9: he plot of La-h-Sc showing the provenance of the sediments to be mainly of active continental margin (ater [15]). he ields are A: oceanic island arc, B: continental island arc, C: active continental margin, and D: passive margin. B 0.0 0.01 Zr/10 Figure 10: h-Sc-Zr/10 plot showing the provenance of the sediments to be still mainly of active continental margin (ater [15]). Figure 12: h/Co versus La/Sc for the samples. he logarithmic plot shows that the samples are sourced from felsic or acidic silicic rocks, and very few of the samples tend towards intermediate provenance. thorium with respect to uranium can indicate a felsic source. he h/U ratio, which is oten used in relation to h- and U-concentrations as present in weathering under oxidizing conditions, has been used to determine felsic provenance [14, 22]. Weathering under oxidizing conditions results in the mobilization of uranium as U6+ , whereas thorium (h) remains immobile. his causes the h/U ratio to increase signiicantly. Higher abundances of incompatible elements like h indicate felsic rather than maic sources. Materials such as granodiorite source from old upper continental crust and from felsic gneisses are good examples. he h/U ratio can only be used for sedimentary rocks. he h/U ratio has an average of 4.1 (Table 3) which is very close to that of upper continental crust of 3.8. he high ratios of h/Sc and Zr/Sc indicate a slight input of felsic materials from recycled sedimentary provenance. Al2 O3 /TiO2 ratios of most clastic rocks are essentially used to infer the source rock compositions, because ratio Al2 O3 /TiO2 increases from 3 to 8 for maic igneous rocks, from 8 to 21 for intermediate rocks, and from 15 to 70 for felsic igneous rocks [27]. It will be observed that almost all values 8 Journal of Geochemistry Table 3: Table of various elemental ratios. Lithology Sand Sand Sand Shale Shale Shale Shale Shale Shale Sand Sand Sand Shale Shale Shale Sand Sand Shale Shale Shale Shale K/Cs ratio 0.2 0.3 0.4 1.1 1.1 1.0 2.0 1.3 0.9 3.2 3.3 2.9 2.0 3.3 1.4 1.6 2.3 1.9 3.4 1.1 0.8 1.7 h/U ratio 4.9 4.3 4.0 3.4 3.5 3.7 4.8 4.8 4.0 5.2 1.5 2.8 4.1 3.1 3.1 4.3 4.8 4.3 6.0 5.3 4.7 4.1 Table 4: Range of elemental ratios for felsic and maic igneous rocks and corresponding upper continental crust values. he table of range of maic and felsic rocks is ater Cullers [23, 24]; Cullers and Podkovyrov [25]; Cullers et al. [26]; and the UCC values are ater Taylor and McLennan [20]. Elemental ratios Felsic rocks Maic rocks Upper continental crust h/Sc h/Co h/Cr Cr/h La/h 0.84–20.05 0.27–19.4 0.13–2.7 4.00–15.00 25.0–16.3 0.05–0.22 0.04–1.4 0.018–0.046 25–500 0.43–0.86 0.79 0.63 0.13 7.76 2.21 Cr/h 2.9 2.7 3.8 6.5 7.1 7.7 16.6 14.1 9.9 23.5 55.3 56.8 8.6 75.5 12.1 8.0 51.8 9.4 7.0 9.2 10.7 19.0 La/Th Sample (in meters) 1160–1180 1560–1580 1960–1980 2960–2980 3960–3980 4560–4580 5460–5480 5760–5780 6160–6180 7060–7080 7260–7280 7560–7580 7760–7780 7960–7980 8060–8080 8160–8180 8560–8580 8960–8980 10,360–10,380 11,060–11,080 11,460–11,480 Average 10 9 8 7 6 5 4 3 2 1 0 h/Co 1.8 1.9 0.8 0.4 0.8 0.8 0.4 0.3 0.7 0.2 0.1 0.1 0.5 0.1 0.3 0.5 0.1 1.2 0.6 0.5 0.4 73.7 Al2 O3 /SiO2 17 15 17 17 16 19 13 8 18 10 15 18 15 18 18 16 20 15 15 17 16 15.9 La/Sc 7.42 7.36 5.75 5.22 4.24 3.69 3.64 2.18 3.09 4.68 1.70 2.06 3.29 2.03 4.50 6.17 4.60 4.13 7.15 4.04 2.68 h/Sc 2.83 2.36 2.00 1.72 1.39 1.21 1.52 1.32 0.91 1.37 0.63 0.71 1.35 0.76 1.89 2.21 1.52 1.59 2.54 1.09 0.83 More felsic More maic 0 2 4 6 8 10 Th/Yb Figure 13: La/h versus h/Yb plot showing felsic versus maic character ater McLennan et al., [20]. for the Al2 O3 /TiO2 ratio are above 15 with an average of 15.9 (Table 3) which is an indication that the source rock is felsic or acidic igneous rock such as granite, granodiorite, rhyolite, dacite, or aplite. he elevated Zr/Sc ratios relect signiicant reworking and a clear input from upper crust igneous sources. h/Sc values for the analyzed samples (Table 3) were in the range of 0.83–2.83, implying a felsic igneous provenance. he same applies for the h/Co ratio (Table 3) as most of the values are above 0.27 and less than 19.5. However it will be observed that 7060–7080, 7260–7280, 7560–7580, and 7960– 7980; their h/Co ratio is less than 0.22 (implying maic source) and their Cr/h ratios are greater than 15.00, around 50, and even 75.5 for 7960–7980 and this also implies a maic source input. he La/h versus h/Yb plots have been used to diferentiate between felsic and maic nature of source rocks [15, 28]. In these plots Figure 13, the studied samples show felsic character of source rocks by its unusually high La/h (felsic provenance) as compared with h/Yb (maic provenance). 3.6. Provenance from Rare Earth Elements. Rare earth elements (shown in Table 5) comprise the lanthanide elements [La-Lu] as well as Y [29]. Since Y mirrors the heavy lanthanides Dy-Ho in terms of geochemical behavior, it is typically included with them for discussion. Sc may also be included because, in low temperature aqueous luids such as seawater, it behaves similarly to REE in having exceptionally Journal of Geochemistry 9 Table 5: Rare earth elements concentrations in ppm for the analyzed samples. Sample (in meters) 1160–1180 1560–1580 1960–1980 2960–2980 3960–3980 4560–4580 5460–5480 5760–5780 6160–6180 7060–7080 7260–7280 7560–7580 7760–7780 7960–7980 8060–8080 8160–8180 8560–8580 8960–8980 10,360–10,380 11,060–11,080 11,460–11,480 Average La ppm 8.9 8.1 9.2 16.7 30.1 31.7 9.1 9.6 23.2 8.9 4.6 6.4 16.1 5.9 8.1 17.9 11.5 26 18.6 37.6 29.2 1.6 Ce ppm 20.01 18.11 19.38 36.08 68.14 67.95 21.18 25.82 58.84 24.9 15.37 19.4 45.68 17.5 22.61 41.58 28.5 60.17 40.4 91.97 77.09 1.6 Pr ppm 2 1.9 2.1 3.9 7.6 7.6 2.6 3.1 7.3 3.4 2.2 2.6 6 2.3 2.8 4.8 3.2 7.1 4.4 9.6 9.6 1.5 Nd ppm 8.9 8 9.6 16.9 35.3 33.7 12.4 14.7 34.8 15.5 11 13.7 27.7 12.1 13.5 22.8 15.9 31.8 20.4 44.3 43.7 1.5 Sm ppm 1.5 1.3 1.6 2.8 5.7 5.2 1.9 2.8 5.8 2.6 1.8 2.3 4.5 2.1 2.2 3.6 2.6 4.8 3 7.3 7.4 1.2 Eu ppm 0.1 <0.1 0.2 0.4 1 0.9 0.3 0.5 1.1 0.5 0.3 0.5 0.8 0.4 0.4 0.6 0.5 0.9 0.5 1.1 1.3 #VALUE! low concentrations and by entering the sixfold coordinated mineral sites. Low atomic number members of the series from La-Sm are termed the light rare earth elements (LREE). hose with higher atomic numbers from Gd-Yb are termed the heavy rare earth elements (HREE). he patterns of shapes and trending structure on REE diagrams can be used to evaluate the petrology of a rock. Most important is the Europium anomaly that at most times is enriched or depleted and as such assumes position which oten lies of the general trend. his anomaly is deined by the other elements on the REE diagram and termed europium anomaly. If the plotted composition lies above the general trend, then the Eu anomaly is described as positive and if it lies below the general trend it is described as negative. he REE pattern of average sediments is interpreted to relect the average upper continental crust and thus a negative Eu anomaly is found in most sedimentary rocks. his indicates that shallow, intercrustal diferentiation involving plagioclase diferentiation (through either melting or fractional diferentiation) must be a fundamental process in controlling the composition and element distribution within the continental crust [20]. Before the plot, the REE values in ppm as obtained from the analyzed samples have to be normalized. he REE chondrite normalizing factors used for this study are from Wakita et al. [30] as shown in Figure 14. Also the North American shale composition is used as shown Gd ppm 1.2 1 1.4 2.2 4.4 4.8 1.7 2.5 4.9 2.7 1.6 2.3 3.4 1.8 1.6 2.9 2 3.6 2.4 6.1 6.3 1.0 Tb ppm 0.1 0.1 0.1 0.3 0.6 0.6 0.2 0.3 0.6 0.3 0.2 0.3 0.4 0.2 0.2 0.3 0.3 0.4 0.3 0.8 0.8 0.8 Dy ppm 1 0.8 1.1 1.8 3.5 3.5 1.2 1.9 3.8 1.8 1.3 1.6 2.4 1.4 1.2 2.1 1.5 2.8 1.8 5 4.9 0.8 Ho ppm 0.1 0.1 0.2 0.3 0.6 0.6 0.2 0.3 0.6 0.3 0.2 0.3 0.5 0.2 0.2 0.3 0.3 0.5 0.3 0.8 0.8 0.6 Er ppm 0.4 0.3 0.5 0.7 1.6 1.7 0.5 0.8 1.4 0.7 0.6 0.7 1 0.5 0.5 0.8 0.6 1.1 0.7 2.2 2 0.6 Tm Ppm <0.1 <0.1 <0.1 0.1 0.2 0.2 <0.1 0.1 0.2 <0.1 <0.1 <0.1 0.1 <0.1 <0.1 0.1 <0.1 0.2 0.1 0.3 0.3 0.4 Yb ppm 0.4 0.4 0.5 0.8 1.6 1.6 0.6 0.9 1.5 0.8 0.6 0.6 1 0.6 0.5 0.9 0.6 1.3 0.8 2.2 2.1 0.6 Lu ppm <0.1 <0.1 <0.1 0.1 0.2 0.2 <0.1 0.1 0.2 <0.1 <0.1 <0.1 0.1 <0.1 <0.1 0.1 <0.1 0.2 0.1 0.3 0.3 Y ppm 3.3 2.8 4.6 7.1 14.7 14.2 4.9 5.7 14.9 8.5 5.4 6 10.7 5.3 4.9 9 6.2 11.5 7.1 20.1 19.7 0.9 in Figure 15. Besides the normalized plot, other parameters used to characterize the REE abundant in rocks include: fractionation indices represented by (La/Yb)cn which is an index of the enrichment of the light rare earth elements (LREE) over heavy rare earth elements (HREE); Eu anomaly; Ce anomaly; HREE depletion represented by (Gd/Yb) > 2.0; grain size. 3.7. Fractionating Indices/Degree of Fractionation of REE. he degree of fractionation of REE pattern can be expressed by concentration of light REE (La or Ce) ratio to the concentration of heavy REE (Yb). he lanthanum (La) and ytterbium (Yb) are oten used which will have to be normalized and this ratio is expressed as (LaN /YbN ). his combined with Eu anomaly is very important parameter that describes REE patterns and can be used in determining the source rock. hese fractionation indices represented by (La)N /(Yb)N , that is, [(La sample/La chondrite)/(Yb sample/Yb chondrite)] ratio, can be used to deine relative behavior of LREE to the HREE. his ratio has been calculated for all the samples in the present study as presented in Table 6. It is within the range of 1.97 and 5.46 with an average value of 3.08 indicating that the HREE are very much depleted with respect to LREE in the present study. 10 Journal of Geochemistry 2.5000 2.0000 1.5000 1.0000 0.5000 0.0000 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y Series 1 Series 2 Series 3 Series 4 Series 5 Series 6 Series 7 Series 8 Series 9 Series 10 Series 11 Series 12 Series 13 Series 14 Series 15 Series 16 Series 17 Series 18 Series 19 Series 20 Series 21 Figure 14: Wakita chondrite normalized spider diagrams. 1.5 1 Similarly in oxidizing conditions, Ce3+ may be oxidized to Ce4+ leading to a decrease in the ionic radius of about 15%. he only place where this reaction occurs on a large scale is marine environment associated with the formation of manganese nodules. When Ce3+ oxidizes to Ce4+ , it separates as an insoluble phosphate if it is in a marine environment. his will cause a distinctive Ce depletion in ocean waters and phases precipitated in equilibrium with seawater. Apart from those anomalies, the REE behaves in an unusually coherent group of elements. here is a continuous decrease in ionic radii from La to Lu and this is termed lanthanide contraction. he decrease in ionic radii is due to increase in the efective nuclear charge pulling the electrons towards the nucleus thereby reducing the electron radii. 3.8. Eu Anomaly. Europium anomaly, usually represented by [Eu/Eu∗ ], may be quantiied by comparing the normalized measured Eu concentration with an expected concentration (Eu∗ ). he Eu∗ is obtained by interpolating between the normalized values of Sm and Gd; that is, Eu∗ = (Smn + Gdn )/2. he Eu used in this study is the concentration of Eu in the sediments, that is, Wakita chondrite normalized, and Eu∗ is a calculated value obtained by linear interpolation or average between Smn (samarium chondrite normalized) and Gdn (gadolinium chondrite normalized). So the europium anomaly is given by Eu 0.5 Eu∗ 0 La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Y −0.5 = Average value of chondrite normalized Eu of the data Eun Average value of chondrite normalized (Smn + Gdn ) /2 . (1) Taylor and McLennan [20] recommended the use of a geometric mean for calculating the Eu anomaly as follows: −1 −1.5 −2 Series 1 Series 2 Series 3 Series 4 Series 5 Series 6 Series 7 Series 8 Series 9 Series 10 Series 11 Series 12 Series 13 Series 14 Series 15 Series 16 Series 17 Series 18 Series 19 Series 20 Series 21 Figure 15: NASC normalized spider diagram. 3.7.1. Europium (Eu) and Cerium (Ce) Anomaly. Within rare earth elements under reducing conditions, as within the mantle or lower crust, europium may exist in the divalent state (Eu2+ ). his results in an increase in the ionic radius of about 17% making it essentially identical to Sr2+ . he consequence of this is that Eu substitutes freely in place of Sr in feldspars notably plagioclase feldspars, leading to distinctive geochemical behavior of “Eu” compared with other REE. In general, anomalous activity of Eu is an indication of an earlier event that occurred in a reducing igneous environment which eventually evolved into upper continental crust [20]. Eun Eu = √{ }. Eu∗ Snn × Gdn (2) Although a number of elements or minerals may determine the distribution of Eu during igneous processes, the most important is feldspar particularly plagioclase. Europium anomalies are majorly controlled by feldspars, particularly in felsic magmas. his is because Eu2+ (divalent form of Eu) is present in plagioclase and potassium feldspars are compactable, in contrast with the incompatible trivalent REE. hus the removal of feldspar from a felsic melt by crystal fractionation or partial melting of a rock in which feldspar is retained or present in the source will give rise to a negative Eu anomaly. In plagioclase, substantial Eu2+ may substitute for Ca2+ in place of Sr; thus the Eu anomaly (Eu/Eu∗ ) relects the extent of plagioclase fractionation, leading to pronounced enrichments of its associated trivalent REE and depletion of Eu. hus liquids that formed where plagioclase is a stable residual phase or from which plagioclase is crystallized and lost will tend to be signiicantly depleted in Eu so will have a negative Eu anomaly. On the other hand, Rudnick [31] suggested that the positive Eu anomaly is mainly due to the efect of areas prominent in hydrothermal vents or due to the feldspar origin. Journal of Geochemistry 11 Table 6: REE chondrite normalized elemental ratios used in analyzing the provenance of the sediments. Samples 1160–1180 1560–1580 1960–1980 2960–2980 3960–3980 4560–4580 5460–5480 5760–5780 6160–6180 7060–7080 7260–7280 7560–7580 7760–7780 7960–7980 8060–8080 8160–8180 8560–8580 8960–8980 10,360–10,380 11,060–11,080 11,460–11,480 Average Lithology Sand Sand Sand Sand Sand Sand Shale Shale Shale Sand Sand Sand Shale Shale Shale Sand Sand Shale Shale Shale Shale Eu/Eu∗ 0.48 0.00 0.81 0.83 0.79 0.78 0.87 0.86 0.79 0.85 0.90 0.91 0.83 0.92 0.94 0.83 0.92 0.83 0.85 0.74 0.76 0.79 La/Yb 5.46 5.30 4.02 3.02 2.26 2.29 3.28 2.37 2.20 2.53 2.60 2.93 2.55 2.84 3.86 2.81 3.51 2.44 3.10 2.04 1.97 3.02 Ce/Ce∗ 1.02 1.03 1.00 1.01 1.01 1.01 1.02 1.04 1.03 1.06 1.12 1.08 1.05 1.07 1.06 1.02 1.03 1.02 1.01 1.03 1.03 1.04 Gd/Yb 2.56 2.25 2.05 1.65 1.43 1.47 1.87 1.61 1.53 1.81 1.81 2.17 1.70 1.93 2.21 1.71 2.03 1.48 1.72 1.37 1.41 1.80 Values greater than 0.85 indicate positive Eu anomaly, values less than 0.85 indicate a negative Eu anomaly, and a value of precisely 0.85 indicates no anomaly. In the present study as illustrated in Table 6, Eu anomaly values vary from 0.00 to 0.92 with an average of 0.79 corresponding to negative Eu anomaly. his is also shown in Figures 14 and 15 as spider diagrams. Felsic rocks and sediments usually have negative anomalies due to lithospheric or intracrustal feldspar fractionation or breakdown of feldspars during weathering processes [32]. Felsic igneous rocks usually contain higher LREE/HREE ratios and more pronounced negative Eu anomalies, while maic igneous rocks contain lower LREE/HREE ratios with few or no Eu anomalies [24]. In addition, Cullers [23] proposed that sediments with Cr/h ratios ranging from 2.5 to 19.5 and Eu/Eu∗ values from 0.48 to 0.78 come mainly from felsic not maic sources. According to the study of McLennan et al. [21], active margin sediments, in contrast to passive margin sediments, oten show lower Eu/Eu∗ . 3.9. Ce Anomaly. Ce/Ce∗ anomaly is usually given by Ce/Ce∗ = 5 ×Cen/4{Lan +Smn } . he samples values (Table 6) range from 1.00 to 1.08 with calculated average value of 1.04. his is no anomaly as it is approximately 1. Ce anomaly (Ce/Ce∗ ) can indicate REE redistribution during weathering possibly a consequence of fractionation also for Sm and Nd isotopes. Since the Ce/Ce∗ ratios are close to 1, the small diference in Ce/Ce∗ for the studied rocks is within the uncertainties of the measurements. hus no anomalous Ce/Ce∗ can be deduced. Zr/TiO2 0.04 0.03 0.04 0.03 0.02 0.02 0.03 0.02 0.03 0.03 0.03 0.02 0.02 0.02 0.03 0.03 0.02 0.02 0.03 0.02 0.02 0.03 ΣLREE 6.0 5.8 6.1 7.4 8.8 8.8 6.4 6.8 8.6 6.8 5.8 6.3 8.1 6.1 6.5 7.8 7.0 8.6 7.6 9.4 9.2 7.33 ΣHREE 2.2 1.9 2.8 4.7 6.8 6.9 3.3 4.9 6.8 4.3 3.4 4.0 5.6 3.4 3.2 5.0 3.9 6.2 4.7 7.8 7.8 4.74 ΣL/ΣH 2.8 3.1 2.2 1.6 1.3 1.3 1.9 1.4 1.3 1.6 1.7 1.6 1.4 1.8 2.0 1.6 1.8 1.4 1.6 1.2 1.2 1.70 La/Y 2.70 2.89 2.00 2.35 2.05 2.23 1.86 1.68 1.56 1.05 0.85 1.07 1.50 1.11 1.65 1.99 1.85 2.26 2.62 1.87 1.48 1.81 La/V 2.70 0.74 0.66 0.44 0.46 0.45 0.28 0.14 0.33 0.31 0.14 0.18 0.32 0.19 0.37 0.69 0.38 0.48 0.66 0.40 0.33 0.41 3.10. (Gd/Yb)� Ratio. he (Gd/Yb)N ratio also documents the nature of source rocks and the composition of the continental crust [20]. Archean crust generally has higher (Gd/Yb)N ratio, recording typically values above 2.0 in sedimentary rocks, whereas the post-Archean rocks have (Gd/Yb)N values commonly between 1.0 and 2.0 [33– 35]. About four of the twenty-one analyzed samples have (Gd/Yb)N ratios greater than 2.0 (Table 6) indicating the possibility of the post-Archean rocks being the source rocks for the formation. 3.11. Grain Size and REE. REE in various grain sizes has been examined by Cullers et al. [36] and Cullers et al. [26]. hey found that clay contains the largest fraction of REE (high La/Yb), followed by silt which is of lesser proportion/fraction and lowest fractions in sands (least La/Yb) than iner grain sizes. he presence and magnitude of Eu anomalies are however similar for all grain sizes. Because sandstones tend to have lower REE than shales, their REE patterns are more prone to be considerably dominated by heavy minerals. 4. Conclusion 4.1. Provenance of the Sediments. Based on major oxides most of the sample plots in the ields were felsic igneous provenances suggesting high content of silica from an acid rock most probably granite or gneiss or dacite or any acidic (felsic) igneous rock. he provenance and prevalent conditions of deposition from various elemental ratios indicate that the h/U ratio 12 has an average of 4.1 which is very close to that of upper continental crust of 3.8. he high ratios of h/Sc and Zr/Sc indicate a slight input of felsic materials from recycled sedimentary provenance. Higher abundances of incompatible elements like h indicate felsic rather than maic sources. Elevated values of thorium with respect to uranium may imply a felsic source. It will be observed that most values for the Al2 O3 /TiO2 ratio fall between 15 and 70 (the range for igneous rock) which is an indication that the source rock is felsic or acidic igneous rock such as granite, granodiorite, rhyolite, dacite, or aplite. h/Sc values for the analyzed samples were in the range of 0.83–2.83, implying a felsic igneous provenance. he same applies for the h/Co ratio as most of the values are above 0.27 and less than 19.5 (h/Sc and h/Co values for felsic rocks are 0.84–20.05 and 0.27– 19.5, resp.). hus the source of the rock weathered to give the sediment is a felsic or acidic igneous rock, probably granite. h/Co versus La/Sc logarithmic plot shows that the samples are sourced from felsic or acidic silicic rocks, and very few of the samples tend towards intermediate provenance. Provenance from REE and negative EU anomaly points to the fact that average REE pattern of the sediments is interpreted to relect the average upper continental crust. Coupled with a negative Eu anomaly, conclusions can be drawn that shallow, intercrustal diferentiation involving plagioclase diferentiation (through either melting or fractional diferentiation) must be a fundamental process in removal of feldspar from a felsic melt. he LREE enrichment as well as relatively lat HREE pattern also conirms felsic source rock. he relative REE patterns and Eu anomaly size have also been utilized to deduce sources of sedimentary rocks [20, 37]. Maic rocks contain low LREE/HREE ratios and tend not to contain Eu anomalies, whereas more felsic rocks usually contain higher LREE/HREE ratios and negative Eu anomalies [38]. A negative Eu anomaly is a conirmation of the sediment’s provenance from felsic sources. hus from the enrichment LREE or higher LREE/HREE, we can conclude that the provenance of the sediments is felsic rock. 4.2. Tectonic Settings. From major oxides it can be concluded that the tectonic setting of the Niger delta is active continental margin and this conirms the cretaceous rit systems of West and Central Africa. he rit system extends for over 4000 km from Nigeria northwards into Niger and Libya and eastwards to Sudan and Kenya. his cretaceous rit system forms a trough in which those sediments are deposited. he trace elements conirmed the tectonic settings of the sediments as active continental margins. he trivariate plots of La-h-Sc, h-Sc-Zr/10, and h-Co-Zr/10 all register the provenance of the sediments to be active continental margin. he h/Sc versus Zr/Sc diagram ater McLennan et al. [14], conirms the zone of sediment recycling in upper crust input. Conflict of Interests he authors declare that there is no conlict of interests regarding the publication of this paper. Journal of Geochemistry References [1] H. Doust and E. Omatsola, “Niger Delta,” in Divergent/Passive Margin Basins, J. D. Edwards and P. A. Santogrossi, Eds., AAPG Memoir 48, pp. 239–248, American Association of Petroleum Geologists, Tulsa, Okla, USA, 1990. [2] H. Kulke, “Nigeria,” in Regional Petroleum Geology of the World. Part II: Africa, America, Australia and Antarctica, H. Kulke, Ed., pp. 143–172, Gebrüder Borntraeger, Berlin, Germany, 1995. [3] J. Hospers, “Gravity ield and structure of the Niger Delta, Nigeria, West Africa,” Bulletin of the Geological Society of America, vol. 76, no. 4, pp. 407–422, 1965. [4] A. Kaplan, C. U. Lusser, and I. O. Norton, “Tectonic map of the world, panel 10,” scale 1:10,000,000, American Association of Petroleum Geologists, Tulsa, Okla, USA, 1994. [5] C. M. Ekweozor and E. Daukoru, “Northern delta depobelt portion of the Akata-Agbada petroleum system, Niger Delta, Nigeria,” in he Petroleum System—From Source to Trap, L. B. Magoon and W. G. Dow, Eds., AAPG Memoir 60, pp. 341–358, American Association of Petroleum Geologists, Tulsa, Okla, USA, 1994. [6] Petroconsultants, Petroleum Exploration and Production Database, Petroconsultants, Houston, Tex, USA, 1996. [7] T. R. Klett, T. S. Ahlbrandt, J. W. Schmoker, and J. L. Dolton, “Ranking of the world’s oil and gas provinces by known petroleum volumes,” U.S. Geological Survey Open-File Report 97-463, 1997. [8] M. R. Bhatia, “Plate tectonics and geochemical composition of sandstones,” Journal of Geology, vol. 91, no. 6, pp. 611–627, 1983. [9] B. P. Roser and R. J. Korsch, “Determination of tectonic setting of sandstone-mudstone suites using SiO2 content and K2 O/Na2 O ratio,” he Journal of Geology, vol. 94, no. 5, pp. 635– 650, 1986. [10] J. D. Grigsby, “Detrital magnetite as a provenance indicator,” Journal of Sedimentary Petrology, vol. 60, no. 6, pp. 940–951, 1990. [11] Y. J. Joo, Y. I. Lee, and Z. Bai, “Provenance of the Qingshuijian Formation (Late Carboniferous), NE China: implications for tectonic processes in the northern margin of the North China block,” Sedimentary Geology, vol. 177, no. 1-2, pp. 97–114, 2005. [12] Z. Jin, F. Li, J. Cao, S. Wang, and J. Yu, “Geochemistry of Daihai Lake sediments, Inner Mongolia, north China: implications for provenance, sedimentary sorting, and catchment weathering,” Geomorphology, vol. 80, no. 3-4, pp. 147–163, 2006. [13] J. A. Winchester and P. A. Floyd, “Geochemical discrimination of diferent magma series and their diferentiation products using immobile elements,” Chemical Geology, vol. 20, pp. 325– 343, 1977. [14] S. M. McLennan, S. Hemming, D. K. McDaniel, and G. N. Hanson, “ Geochemical approaches to sedimentation, provenence and tectonics,” in Processes Controlling the Composition of Clastic Sediments, M. J. Johnsson and A. Basu, Eds., vol. 284, Geological Society of America Special Paper, pp. 21–40, Geological Society of America, 1993. [15] M. R. Bhatia and K. A. W. Crook, “Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins,” Contributions to Mineralogy and Petrology, vol. 92, no. 2, pp. 181–193, 1986. [16] P. A. Floyd and J. A. Winchester, “Magma type and tectonic setting discrimination using immobile elements,” Earth and Planetary Science Letters, vol. 27, no. 2, pp. 211–218, 1975. Journal of Geochemistry [17] P. A. Floyd and J. A. Winchester, “Identiication and discrimination of altered and metamorphosed volcanic rocks using immobile elements,” Chemical Geology, vol. 21, no. 3-4, pp. 291– 306, 1978. [18] J. A. Winchester and P. A. Floyd, “Geochemical magma type discrimination: application to altered and metamorphosed basic igneous rocks,” Earth and Planetary Science Letters, vol. 28, pp. 459–469, 1976. [19] J. A. Pearce, “Sources and settings of granitic rocks,” Episodes, vol. 19, no. 4, pp. 120–125, 1996. [20] S. R. Taylor and S. M. McLennan, he Continental Crust: Its Composition and Evolution, Blackwell Publishing, Oxford, UK, 1985. [21] S. M. McLennan, S. R. Taylor, M. T. McCulloch, and J. B. Maynard, “Geochemical and NdSr isotopic composition of deepsea turbidites: crustal evolution and plate tectonic associations,” Geochimica et Cosmochimica Acta, vol. 54, no. 7, pp. 2015–2050, 1990. [22] J. A. Hurowitz and S. M. McLennan, “Geochemistry of CambroOrdovician sedimentary rocks of the northeastern United States. Changes in sediment sources at the onset of Taconian orogenesis,” Journal of Geology, vol. 113, no. 5, pp. 571–587, 2005. [23] R. L. Cullers, “he controls on the major and trace element variation of shales, siltstones, and sandstones of PennsylvanianPermian age from uplited continental blocks in Colorado to platform sediment in Kansas, USA,” Geochimica et Cosmochimica Acta, vol. 58, no. 22, pp. 4955–4972, 1994. [24] R. L. Cullers, “he geochemistry of shales, siltstones and sandstones of Pennsylvanian-Permian age, Colorado, USA: implications for provenance and metamorphic studies,” Lithos, vol. 51, no. 3, pp. 181–203, 2000. [25] R. L. Cullers and V. N. Podkovyrov, “Geochemistry of the Mesoproterozoic Lakhanda shales in Southeastern Yakutia, Russia: implications for mineralogical and provenance control, and recycling,” Precambrian Research, vol. 104, no. 1-2, pp. 77– 93, 2000. [26] R. L. Cullers, A. Basu, and L. J. Suttner, “Geochemical signature of provenance in sand-size material in soils and stream sediments near the Tobacco Root batholith, Montana, U.S.A.,” Chemical Geology, vol. 70, no. 4, pp. 335–348, 1988. [27] K.-I. Hayashi, H. Fujisawa, H. D. Holland, and H. Ohmoto, “Geochemistry of ∼1.9 Ga sedimentary rocks from Northeastern Labrador, Canada,” Geochimica et Cosmochimica Acta, vol. 61, no. 19, pp. 4115–4137, 1997. [28] S. M. McLennan, W. B. Nance, and S. R. Taylor, “Rare earth element-thorium correlations in sedimentary rocks and the composition of the continental crust,” Geochimica et Cosmochimica Acta, vol. 44, no. 11, pp. 1833–1839, 1980. [29] R. J. Puddephatt, he Periodic Table of Elements, Oxford University Press, 1972. [30] H. Wakita, P. Rey, and R. A. Schmitt, “Abundances of the 14 rare-earth elements and 12 other trace elements in Apollo 12 samples: Five igneous and one breccia rocks and four soils,” in Proceedings of the Second Lunar Science Conference, pp. 1319– 1329, Pergamon Press, Oxford, UK, 1971. [31] R. L. Rudnick, “Restites, Eu anomalies and the lower continental crust,” Geochimica et Cosmochimica Acta, vol. 56, no. 3, pp. 963– 970, 1992. [32] K. C. Condie, M. D. Boryta, J. Liu, and X. Qian, “he origin of khondalites: geochemical evidence from the Archean to Early Proterozoic granulite belt in the North China craton,” Precambrian Research, vol. 59, no. 3-4, pp. 207–223, 1992. 13 [33] S. M. McLennan, “Rare earth elements in sedimentary rocks: inluence of provenance and sedimentary processes. Geochemistry and mineralogy of the rare earth elements,” Reviews in Mineralogy and Geochemistry, vol. 21, pp. 169–200, 1989. [34] S. M. McLennan and S. R. Taylor, “Sedimentary rocks and crustal evolution: tectonic setting and secular trends,” he Journal of Geology, vol. 99, no. 1, pp. 1–21, 1991. [35] S. M. McLennan and S. Hemming, “Samarium/neodymium elemental and isotopic systematics in sedimentary rocks,” Geochimica et Cosmochimica Acta, vol. 56, no. 3, pp. 887–898, 1992. [36] R. L. Cullers, T. Barrett, R. Carlson, and B. Robinson, “Rareearth element and mineralogic changes in Holocene soil and stream sediment: a case study in the Wet Mountains, Colorado, U.S.A,” Chemical Geology, vol. 63, no. 3-4, pp. 275–297, 1987. [37] D. J. Wronkiewicz and C. C. Kent, “Geochemistry and provenance of sediments from the Pongola Supergroup, South Africa: evidence for a 3.0-Ga-old continental craton,” Geochimica et Cosmochimica Acta, vol. 53, no. 7, pp. 1537–1549, 1989. [38] R. L. Cullers and J. L. Graf, “Rare-earth elements in igneous rocks of the continental crust: intermediate and silicic rocks-ore petrogenesis,” in Rare Earth Element Geochemistry, P. 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