Normalization to shale

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. 

The rare earth elements (REE) form a group of elements that have coherent geochemical behaviour due to their trivalent charge and similar ionic radii. They can, however, be fractionated from one another as a result of geochemical processes operating under specific physico-chemical conditions. In order to outline general trends within and differences between the individual REE, concentrations are usually normalized to a reference system (e.g. to shale). Deviations of individual elements from the generally smooth trend are referred to as anomalies. 

Figure 11 Enrichment factor of elements in (a) average ferromanganese nodule, and (b) average ferromanganese crust, as normalized to A1 and relative to shale (Table 2). The specific associations of elements with various phases are...

Figure 16 Enrichment factor of elements in metalliferous ridge and basal sediments as normalized to (a) A1 and shale, and to (b) Mn and hydrotbermal vent solution (Table 2).

The data in Tables I-III have been used to calculate elemental balances. The results are shown in Table V with all of the numbers put on a molar basis and normalized to 100 organic carbons in the starting shale. This treatment makes it easy to follow the movement of the elements and simplifies the discussion of molecular transformations occurring during retorting. The recovery of carbon (organic plus inorganic) is 95-96% for each experiment. 

Table I presents the actual elemental abundances for the four spent shales (8). Then the percentages of oxides normalized to 100% are given. Finally, the normative mineral assemblages are given using the rules established by Cox and others (12). Table I serves as the basis for much of the discussion that follows.

Figure 3. Relative distribution of PAH in two environmental samples ana three fossil fuels values are normalized to most abundant species. ° Amna crude oil Spiked in a sediment and carried through PAH isolation procedure. b Shale oil Partitioned using cyclohexane and nitromethane followed by silicic acid chromatography for PAH isolation. e Pittsburg seam bituminous coal Extracted with methylene chloride and carried through PAH isolation procedure.

Shale fissility is important drilling -normal to fissility leads to fewer problems than drilling -parallel to fissility (Fig 2). 

In the study area most veins are restricted to the limestone layers (Fig. 2). Comparatively few veins dissect the shale layers and those that do mostly follow inclined shear fractures in the soft shale layers. Thus, during vein formation the shale had no tensile strength and failed in shear rather than in extension. The veins occupying inclined shear fractures are thinner than the same veins in the limestone layers, where they are vertical extension fractures. This is because where the veins are inclined they are no longer perpendicular to the minimum principal compressive stress, 05, but normal to a higher stress cr (Fig. 6). 

Figure 4.21 Rare earth element abundances in North American Shale Composite (NASC) and European shale, normalized to chondritic values. Data from Table 4.7, columns 5 and 6 nonnalizing values from Table 4.5, column 4.

REE patterns in The aqueous geochemistry of the REE is a function of the type of complexes that sea and river the REE may form, the length of time the REE remain in solution in the oceans water (their residence time), and to a lesser extent the oxidizing potential of the water. The topic is well reviewed by Brookins (1989). The REE contents of rivers and seawater are extremely low (Table 4.6), for they are chiefly transported as particulate material. When normalized to a shale composite (Section 4.3.2), REE concentrations in seawater are between six and seven orders of magnitude smaller that the shale value. River wafers are about an order of magnitude higher. 

Fig. 38. Lanthanide abundance patterns for selected iron formations and iron-rich sedimentary rocks. Data are normalized to average shale values of the same period, Archean iron formation being normalized to average Archean shale (McLennan and Taylor 1984) and the others normalized to PAAS. In detail, iron formations exhibit considerable variability in lanthanide patterns. These samples illustrate the general feature of Eu enrichment, relative to contemporaneous upper continental crust, for Archean and early Proterozoic iron formations. The younger examples display no such Eu enrichment. This feature has been used to suggest that early Precambrian seawater was dominated by a hydrothermal signature, enriched in Eu (see fig. 30). (Data are from table 22.)...

Fig. 41. Lanthanide patterns for various grain size fractions of an unconsolidated sediment. Data normalized to the <2 pm fraction, the closest approximation to a shale derived from the same source. (Data are from table 24.)...

Figure 7 Chondrite-normalized REE patterns of selected rocks and reservoirs from oceanic crustal environments. Note that MORE and DMM have parallel REE patterns, a reflection that MORE is derived from DMM by high degrees (>10%) of partial melting. Also note that pelagic clays have REE patterns similar to shales derived from the upper continental crust. The slight negative Ce anomaly is significant and reflects a small component of authigenic material derived from seawater...

Oceans comprise 96.8% of the Earth s near-surfece water and accordingly, completely dominate the REE mass balance in the global hydrosphere. A thorough review of the geochemistry of REE in natural waters can be found in Byrne and Sholkovitz. Most REE in both terrestrial and marine waters are derived ultimately from the upper continental crust and accordingly, normalization to average shale is most informative. One notable exception is that REE in marine hydrothermal fluids are derived ultimately from interactions with oceanic basalts. 

So far, we have considered fractures, which have continuous pressures and tangential velocities but discontinuous normal velocities. Shales, by contrast, have discontinuous pressures and tangential velocities but continuous normal velocities. Special flow anomalies can be constructed by superposing linear combinations of the two. Sometimes a third class of flow arises, namely, rapid flows through mineralized faults and streaks which are not open to production. These are responsible for velocities tangent to the fracture but are different from... 

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.

Figures 6a and b provide the results of direct log (Mr) observations for average deep water and average surface water (a) normalized to North American Shale Composite (log(MT)sN) and (b) normalized to river water suspended load (Piepgras and Jacobsen 1992). Figure 6c shows the log + L /8n(M)[L ]") term in eq. (2) calculated at...

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