Grain size distribution of surface sediment. Mineralogy of different sediment fractions. Geochemistry of surface sediment fine fraction

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Javier Huertas3, Alberto López-Galindo3 1 National nstitute of Science and Marine Technology, Salamboo,

1 TRACE ELEMENT N DFFERENT MARNE SEDMENT FRACTONS OF THE GULF OF TUNS: CENTRAL MEDTERRANEAN SEA Noureddine Zaaboub1*, Walid Oueslati2, Saadi Abdeljaoued2, F. Javier Huertas3, Alberto López-Galindo3 1 National nstitute of Science and Marine Technology, Salamboo, Tunis, Tunisia 2 Science University of Tunisia, Manar, Tunis,Tunisia 3 nstituto Andaluz de Ciencias de la Tierra. CSC UGR. 002 Granada, Spain *nouri_zaaboub@yahoo.fr

2 Contents ntroduction Grain size distribution of surface sediment Mineralogy of different sediment fractions Geochemistry of surface sediment fine fraction Statistical analysis:pca and Cluster analysis Conclusion

3 ntroduction Outlet fo Ghar le Melh Lagoon Outlet of Mejerda Mediterranean sea Algeria Oued Medjerda Tabarka Ghardimaou Oued Mellégue Oued Rhezla Jendouba Oued Zerga Oued Tessa Oued Siliana Bizerte Tunisia Tunis Kairouan 0 Gulf of Tunis Sousse N 38 4 N Lagune de Ghar El Melh Kallat Al 33 Andalous Oued Mejerda Kaliji Chenal Fig1: Study area and sampling sites of surface sediment in the north of Tunisia 0 Km 0 5 Km Gammart Topography of the gulf of Tunis n the North of Tunisia the major wind period is marked by strong and frequent North West direction. This wind engenders littoral currents, gyrating current anticlockwise forms in the centre of the gulf, forming weak current in the central part. Sediment dynamics along a littoral zone is closely dependent on the direction and the intensity of the littoral currents. The Gulf of Tunis is connected to two principal water flows, the Mejerda and the Ghar el Melh lagoon.

4 Grain size distribution of surface sediment The clayey silt and the sandy silt represent the main fractions. We are interested in the fraction which is <3µm that is often selected for geochemical analysis. Three surface sediment fine fractions are separated (<2µ, 2-µ, -3µ) for Major and trace element Silty clay Clayey silt Sandy clay Silt Sandy silt Clayey sand 0 Silty sand 0 0 Clay Fig 2: Ternary diagram of particle size fractions of surface sediment Sand The particles that are less than 2 µm constitute the clay fraction, a fine silt fraction (2 µm) and a mixture of fine and coarse silt fractions (-3 µm). Table 1: particle size fractions of surface sediment less than 3µm µm < Max Min Average 0

5 .1 Meje rd a Ca nal Ca nal 0-2µ 2-µ Meje rd a Meje rd a Ca nal -3µ Fig3: Distribution of fine fractions of surface sediment in the outlet of Mejerda n the central zone, the clay and the fine silt fraction are dominant 5-5%. The fine and coarse silt fraction is dominant in the coastal zone. However, in the central zone there is a punctual accumulation by the presence of a region of offshore outcrops.

6 Mineralogy of different sediment fractions Table 2: average of clay minerals and quartz in surfacial sediment Coastal zone smectite llite Kaolinite Chlorite - S quartz < 2 µm µm µm Central zone smectite llite Kaolinite Chlorite - S quartz < 2 µm µm 3-3 µm Dominant phases are dioctahedral smectite, illite and kaolinite. Chlorite and interstratified illite-smectite are also present. Smectite percentage is higher in the coastal zone compared to the central one. Quartz percentage is almost the same in the coastal zone and the central zone.

7 0-2µ 2-2 0µ -3µ Smectite and fine Quartz grain size are accumulated in littoral zone and in the central part of the Gulf..1 Me je rd a Ca nal Quartz Meje rd a Ca nal Quartz Meje rd a Riv er Ca nal Quartz The distribution of smectite and fine particles of Quartz follow the principal coastal drift directions..1 Smectite Smectite Meje rd a Ca nal Smectite Fig 4: Distribution of quartz and smectite in different grain size fration of surfacial sediment

8 Geochemistry of surface sediment fine fraction Total organic carbon shows a low accumulation in front of Mejerda and Ghar El Melah Lagoon. Lagoon Lagoon Most part of total organic carbon is concentrated in the south part of the gulf. Mejerda Mejerda The C/N ratio shows a terrestrial organic matter influence mainly in front of Ghar El Melh lagoon (), Mejerda () and in the south part of the gulf (). Canal C/N Canal TOC Fig 5: Distribution of TOC and C/N in the surfacial sediment

9 Table 3: Average of major element in surfacial sediment (%) SiO2 Al2O3 Fe2O3 MnO < 2µm µm µm MgO The coarse fraction (-3µm) in comparison to fine fraction (<2µm) is richer in SiO2 signifying the presence of non-clay minerals such as quartz confirmed by X-ray diffraction. The reverse trend is noticed in Al2O3 and Fe2O3. The weight percentage of MnO remains constant in both fractions with an average of 0.02%. CaO Na2O K2O TiO2 P2O5 SO3

10 Table 4: Average of trace element in surfacial sediment Cl V Cr Co Ni Cu Zn Ga Br Rb Sr Y Zr Nb Ba Pb ppm < 2µm µm µm The distribution of Pb is homogenous in the three fractions. A little accumulation of Pb is observed in the fine fraction (<2µm) in the outlet of Mejerda (5ppm). The repartition of Cu, Zn and Zr represent a relative accumulation in the fine fraction (<2µm). Spacial distribution shows an accumulation of Zn in front of mejerda river. Lagoon Mejerda Canal Zn Lagoon Mejerda Canal Pb

11 Compenment 2 ompenment 2 Co Compenment SiO2 Smectite Na2O Pb SiO2 Zr Smectite Zr Na2O SiO2 Na2SO4 Pb V Ba V Fe2O3 Y Smectite Y P2O5 Zr TOC Compenment 1 MgO Ba Fe2O3 Zn Pb P2O5 MnO MnO Cl Cl Cu Zn Quartz MgO Cu 0-2µm Ba MnO Y MgO Fe2O3 Zn Cu P2O5 Cl Ni K2O Br Kaolinite Ni Quartz Sr V Nb Ga Cr Al2O3 TiO2 Rb K2O Br Al2O3 Cr 2-µm Sr TiO2 V Kaolinite Nb Rb Ga Compenment Compenment 1 Br TOC Quartz K2O Sr -3µm Kaolinite TiO2 Ni Cr Nb Rb TOC Al2O3 V Ga Statistical analysis PCA statistical analysis, identified three components that explained %, 4% and 4% of the total variance respectively in the three fractions <2µm, 2-µm and -3µm. There is a clear affinity between total iron and a group of trace elements except Pb (Group ). This element is in association with Smectite in 2- and -3µm fractions in respectively Group V and. The association phenomena took place in the Mejerda river and Ghar el Melh lagoon. Mlayah and al [0] have shown that suspended particles in rivers scarvege trace elements by ferrous, manganese and phosphorous hydroxides. A second group of trace element is associated to alluminosilicates in the three fractions (Group). Fig:Loading of the variables on the first two principal components

12 Ka lat Al Anda lous Kallat Al Andalous Lag oon 1 Mejerda Canal Kalij Km La goon Mejerda Canal Kalij Km Gam m art Gam m art µm µm N N Group1 Group2 Group3 Group4 Group5 Group1 Group2 Group3 Group4 Group5 The cluster analysis allows us to classify the sediments in terms of their inter-metallic and composition ratios. n the fraction < 2µm, Group 1 is characterized by a relatively highest average metal concentrations Fe, Pb, Zn, Ni and Cr. Most of the sites of this group are in front of Mejerda river. n coarser grain size sediment (2-µm), Group 1 contains an extended area of potential sources of metals contaminants in the region, mainly Zn, Cu and Pb. Kalla t Al Andalous Lagoon 1 Mejerda Canal Kalij Km Gam mart µm N Group1 Group2 Group3 Group4 Group5 Fig: Classification of the sites based on the cluster analysis n grain size fraction between (-3µm) there are Group 2 and 5 which form two areas: the northern area (lowest metal average) and the southern one (high metal average).

13 Conclusion Trace element reflects mining in the gulf of Tunis. n the different fractions <2µm, 2-µm and -3µm traces elements are associated to hydrogenous fraction from water source outlet. There is a week degradation of TOC, mainly in front of Ghar el Melh lagoon and in the Southern part of the Gulf. Trace element areal accumulations are clearly Distinguish according to their grain size fractions by cluster analysis in coastal sites in front of Ghar el Melh lagoon and in front of Mejerda.

Preliminary Progress Report. Mineralogy and Geochemistry of Well Cuttings. Prepared for: Gastem USA. Colgate University Department of Geology

Preliminary Progress Report. Mineralogy and Geochemistry of Well Cuttings. Prepared for: Gastem USA. Colgate University Department of Geology Preliminary Progress Report Mineralogy and Geochemistry of Well Cuttings Prepared for: Gastem USA By: Jaclyn Baughman Alison MacNamee Bruce Selleck Colgate University Department of Geology July 30, 2010