Geochemistry of the Recent Black Sea Sediments

Öz

Geochemistry of the Recent Black Sea sediments comprising the Coccolithic, Sapropelic and Lutite units is largely governed by the special characteristics of the Black Sea, related to its geology, morphology, biology and chemistry. According to their statistical distribution, their abundance in the three units, and their areal distribution, the trace elements in the Black Sea sediments fall into the "authigenic" and "allogenic" element groups. The authigenic elements occur as associated largely with the authigenic minerals and organic matter, and have been syngenetically incorporated into the sediments. The Sapropelic unit is relatively more enriched in the authigenic elements such as Mo, U, Cu, B, Ni, Co, V and B than the other two units. These elements show trends of increasing concentration towards the abyssal plains of the Black Sea basin, which are generally characterized by low rates of sedimentation. On the other hand, the allogenic elements such as Ti, Zr, and Cr which are dominantly of detrital mineral origin, occur in higher concentrations in the Lutite unit than the Sapropelic and Coccolithic units. Vanadium and Ni, which appear as authigenic elements in the Sapropelic unit, present a characteristic allogenic distribution pattern in the Coccolithic and Lutite units. Compared with the Lutite and Sapropelic units, the Coccolithic unit is relatively elevated in Ca and Sr, which is widely due to the Coccolithic shells made up of CaCOj. Moreover, the Coccolithic unit is more enriched in SİO2, AI2O3 and TİO2 than the Sapropelic unit. A comparison of the average composition of the Black Sea sediments with that of the deep sea sediments shows that the former are considerably depleted in many elements including Cu, Ni, Co, B, Mn and V. On the other hand, the average composition of the Black Sea sediments is similiar to that of shales except for the higher content of Ca, and relatively lower contents of V, Pb, Cu, Ba and Y.

Anahtar Kelimeler

• Geochemistry
• Sediment
• Karadeniz

Karadeniz'in Güncel Çökellerinin Jeokimyası

Öz

Karadeniz'de yaklaşık son 30.000 yılda çökelen, kokolit, sapropel ve lutit birimlerinin jeokimyası, Karadeniz'in kendine özgü morfolojik, jeolojik, biyolojik ve kimyasal özellikleri ile denetlenmiştir. Karadeniz çökellerindeki iz elementler, istatistiksel dağılımları, üç değişik birimdeki bollukları ve alansal dağılım özellikleri açısından "iç kökenli" (autigenic) ve "dış kökenli" (allogenic) olmak üzere, iki grupta toplanır. Basen içinde, çökellerle eş zamanlı olarak oluşan minerallere ve organik maddeye bağlı, Mo, Cu, U, B, Ni, Co, V ve Ba gibi iç kökenli elementler, organik madde ve demir sülfidlerce zengin sapropel biriminde, diğer birimlerdekine göre daha bol bulunur. Bu elementler, çökelme hızının genel olarak düşü k olduğu derin düzlüklere doğru artan değerler gösterirler. Öte yandan lutit birimi, Ti, Zr ve Cr gibi daha çok kırıntı minerallere bağlı dış kökenli elementler olarak gözüken V ve Ni; kokolit ve lutit biriminde dış kökenli elementlere özgü dağılım biçimi sunarlar. Diğer iki birime göre biyolojik kökenli olarak yüksek Ca ve Sr içeren kokolit birimi; ayrıca sapropel biriminden daha yüksek SİO2, AI2O3 ve TİO2 içeriğine sahiptir. Karadeniz'in güncel çökellerinin ortalama bileşimi, derindeniz çökellerinin bileşimine göre Cu, Ni, Co, Ba, Mn ve V yönünden çok fakirdir. Ortalama bir şeyi bileşimine genelde bir benzerlik sunmasına karşın, Karadeniz çökelleri, şeyl veya siyah şeyl bileşimine göre daha yüksek Ca, daha düşük V, Pb, Cu, Ba ve Y içerirler.

Anahtar Kelimeler

• Jeokimya
• Çökel
• Karadeniz

Kaynakça

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