Lithologies abundances

Metasedimentary rocks formed in these two eons extending from 590 to 4,000 Ma B.P., but differ both in lithological abundances and geochemistry, for instance their Sr/ Sr ratios in carbonates are <0.703 for the Archean and <0.704 for the post-Archean. As might be expected almost all such rocks have undergone extensive metamorphism. Carbonates have been used to evaluate the history of the isotopic composition of seawater. As postdepositional alteration is... 

In Table 3 we present our best estimate for the chemical composition of the upper continental cmst. The footnote provides detailed information on how the value for each element was derived. In general, major-element values represent averages of the different surface-exposure studies, and errors represent one standard deviation of the mean. Because two independent studies are available for the Canadian Shield, and because it appears the Canadian Shield has lower abundances of mafic lithologies and higher abundances of sodium-rich tonalitic-trondhjemitic granitic gneisses compared to other areas (see Section 3.01.2.1),... 

Rehnements of the Taylor and McLennan (1985) model are provided by McLennan and Taylor (1996) and McLennan (2001b). The latter is a modihcation of several trace-element abundances in the upper crust and as such, should not affect their compositional model for the bulk crust, which does not rely on their upper crustal composition. Nevertheless, McLennan (2001b) does provide modihed bulk-crust estimates for niobium, rubidium, caesium, and tantalum (and these are dealt with in the footnotes of Table 9). McLennan and Taylor (1996) revisited the heat-flow constraints on the proportions of mahc and felsic rocks in the Archean crust and revised the proportion of Archean-aged crust to propose a more evolved bulk crust composition. This revised composition is derived from a mixture of 60% Archean cmst (which is a 50 50 mixture of mahc and felsic end-member lithologies), and 40% average-andesite cmst of Taylor (1977). McLennan and Taylor (1996) focused on potassium, thorium, and uranium, and did not provide amended values for other elements, although other incompatible elements will be higher (e.g., rubidium, barium, LREEs) and compatible elements lower in a cmst composition so revised. 

Bade K. E. and Fahrig W. F. (1973) Regional, Lithological, and Temporal Variation in the Abundances of some Trace Elements in the Canadian Shield. Geol. Sur. Canada Paper 72-46, Ottawa, Ontario. 

In the dissolved load, the preferential dissolution of the different types of lithology or mineral can cause large variations in trace-element abundances in rivers. A classical tracer of rock dissolution is strontium. The isotopic ratio of strontium in river waters is, to a first approximation, explained by mixing between different sources. Rain, evaporite dissolution, and carbonate and silicate weathering are the predominant sources of strontium in rivers (see Chapter 5.12). Examples of the use of Ca/Sr, Na/Sr, and Sr isotopic ratios to quantify the proportion of strontium derived from carbonate weathering in large basins can be found in Negrel et al. (1993)... 

The coefficients of variation determined among the cores for the major element oxides are generally very low (Table IV) and in many cases almost at the level of analytic uncertainty. Two exceptions to this are CaO and P2O5 which are associated with carbonate minerals and phosphate nodules. These are not part of the primary lithologies of the shale and are subject to being either locally abundant or absent. 

Patterns of Elemental Distribution. The major, minor, and trace element abundances and the lithology of the stratigraphic sequence are summarized in Tables I and II for the Beulah coals. The data from the Center Mine is given in Karner and others ( 1) where the spatial distribution of elements in the seam was described as fitting into several patterns. In this study the classification of elemental distribution patterns includes 1) Concentration at... 

---