Chemistry of Interstitial Waters of Marine Sediments

Abstract

In recen t years muc h in terest has developed in the processes that have l ed to the present chemical composi tion of the oceans. A mong the pioneering efforts were those o f Gol dschm idt 1933) and Conway 1943). These authors made up approxi­ mate mass balances and calculated the amounts of primary rocks that mus t have weathered to account for the chemical composition of the o cean and the sediments. This work was l ater amplified by Horn & A dams 1966). In the m ass bal ances considered by these various authors, no ser ious attention was given to the possible recycling of materials, nor to the o cean as just one geochemical reservoir through which the elemen ts pass on to a subsequ ent reservoir, namely the s ediments . Considerat ions of t his type were introduced by Barth (1952) and Gol dber g & Arrhenius 1958). The latter authors found good agreemen t between measured rates o f i nput o f some element s into the o cean, vi a the ri vers and the atmosphere, and the ratc of output into thc s edimcn ts. Such balanccs suggest that a stcady state exists in the overall geochemical cycle. In a different approach Sil len ( 967) used a simple chemical equi l ibrium model to account for the composition of sea water. He assumed an e quil ibrium between the ocean an d the m arine sediments, part icul arly w ith the alumino-sil icate and the carbonate phases. Broecker (1971) cri ticized this model , especially because i t tends to discourage any i nquiry into the reactions that m ay t ake place in the various geochemical reservoirs. Broeck er specifical ly ci tes examples that could impl y variatio ns in the i onic compositi on of sea water wi th time, an d he advocates a kinetic approach to the problem, which wou ld then l ead to a search for the processes that control the apparent s teady s tate as i t exists today. Garrels & Mackenzie (1971) developed a steady-state model based on the concept of chemical uniformi tarianism, in w hich the to tal mass and the chemical com­ pos ition of s edimen tary rocks, as well as the c h emical compos ition of the depos ited materials , have remained constan t wi th time, that is, at l east during the las t two b il l ion years. These authors (Garrel s & M ackenzie 1972, Garrels & Perry 1974) have developed this concept i nt o a quantitat ive model i nvolvi ng both estimates of overall fluxes and residen ce times of chemi cal el ements in various geochemical