Shale-normalized lanthanide composition

Fig. 8. Shale-normalized lanthanide compositions of 0.22 (tm filtrates of the Amazon, Fly (Papua New Guinea) and Mississippi River waters. Amazon and Mississippi data from Sholkovitz (1993, 1995) Fly River data from unpublished work of Sholkovitz. G/J Avg. refers to the averaged river water composition of Goldstein and Jacobsen (1988a).

Fig. 1. (a) The concentration of dissolved lanthanides in the surface waters of the Sargasso Sea. A composite of data measured by TIMS (Sholkovitz and Schneider 1991) and INAA (De Baar et al. 1983). Note classic sawtooth abundance pattern. Pm does not exist in nature, (b) Shale-normalized pattern of the composite seawater shown in (a) using shale concentrations of table 1. Tb, being inconsistent, probably reflects an incorrect concentration of the seawater. 

Fractionation of the lanthanides is often quantified by shale-normalized patterns. Normalization to shale represents an abundance relative to that of the upper crust of the continents. A flat shale pattern for river suspended particles would indicate a composition similar to that of averaged continental crust. To study fractionation in rivers, it is also instructive to normalize the dissolved composition to that of suspended particles on the assumption that the particles better represent the solids being weathered in the watershed. 

Shale-normalized data from a 255 m sample illustrate the major features observed by Sholkovitz et al. (1994) (fig. 16). Included in this comparison is the lanthanide composition of dust collected in Bermuda within a few months of the water sample collection (Sholkovitz et al. 1993). The major observation is that surface coatings have a lanthanide composition which is distinct from that of seawater, dust and the two mineral phases of the suspended particles. The mineral matrix of suspended particles and the atmospheric dust are similar in composition. Both mineral matrices have crustlike patterns indicating a detrital source from the atmosphere. About 40-70% of the lanthanides are contained in the acetic acid digest the strong acid digest carries 10-30% and the bomb digest carries 15-25%. At the heavy end of the series (Yb and Lu) the three fractions contribute equal proportions. These observations indicate that the surface... 

Shale-normalized patterns quantify the extent of fractionation during periods of anoxia as illustrated by the water column data collected from different depths of Chesapeake Bay on 26 July 1988 (fig. 38). The oxic surface water exhibits a heavy-enrichment and large negative Ce anomaly while anoxic bottom water has an almost flat pattern and a small negative Ce anomaly. Hence the lanthanide composition shifts away from the heavy-enriched pattern of oxic seawater toward one that is more crust-like. As redox conditions become more reducing, the relative order of trivalent lanthanide release to the... 

Fig. 6a. Lanthanide concentrations in seawater normalized to North American Shale Composite (Piepgras and Jacobsen 1992) are shown for average deep water and average surface water.

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