Trace elements crustal abundances

In the geosphere, strontium is ranked fifteenth in the order of the elemental crustal abundance at 450 ppm. Its presence is greater than that of carbon or chlorine, and slightly less than that of sulfur or fluorine. Of the trace elements, it is ranked fifth [7). Strontium is mainly found in Scotland and the United States, where calcareous rocks with natural apatites containing up to 73000 ppm of strontium are located [8]. 

Phosphorus is the tenth most abundant element on Earth with an average crustal abundance of 0.1% and may be found in a wide variety of mineral phases. There are approximately 300 naturally occurring minerals in which PO4 is a required structural component. Phosphate may also be present as a trace component in many minerals either by the substitution of small quantities of POt into the crystal structure or by the adsorption of P04 onto the mineral surface (Nriagu and Moore, 1984 Slansky, 1986). 

The 76 elements are analyzed, including the 39 elements originally analyzed in analyzed in RGNR Projects and 37 elements newly added. The 76 elements analytical system were established using ICPMS, ICPAES and XRF as backbone, supplemented with other techniques (Table 1). The Detection limits of all trace and subtrace elements are lowered below their crustal abundance (Table 2). The log... 

Relationship between the trace elemental composition of phytoplankton, continental crust and seawater. Phytoplankton and crustal abundances are normalized to phosphorus (ppm trace metal ppm P). Seawater trace elements abundances are normalized to phosphate (ppb trace metal ppb P as phosphate). Source-. From Quigg, A., et al. (2003). Nature 425, 291-294. 

The soil inherits from the parent material a stock of trace elements which, in turn, is controlled by the geochemical nature of the parent material (West, 1981). In global terms this relationship can be illustrated by comparing the commonly accepted mean contents of soil elemental constituents with crustal rock abundances. Reasonably reliable data are available for 67 elements. 

Chapter 8 discusses aspects of the geochemistry of the first series transition elements, most of which are trace elements in the Earth s Crust (that is, their crustal abundances are below 1,000 ppm). 

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. 

The problem of crustal contamination is particularly acute for low mg continental flood basalts and smaller volume continental tholeiitic basalts, both of which have low trace-element concentrations (see Sections 3.03.3.2.3 and 3.03.3.3). The issue is less critical for many smaller volume continental rocks, such as kimberlites and alkali basalts, which have much higher abundances of many trace elements. As a result of their high strontium and neodymium content, for example, the isotopic compositions of these elements in kimberlites and alkali basalts are relatively insensitive to modification during crustal contamination. Conversely, the osmium and lead concentration of basaltic magmas are so low that these isotope systems are particularly vulnerable to modification by interaction with cmstal rocks (McBride et al, 2001 Chesley et al, 2002) hence these systems provide relatively sensitive indicators of crustal assimilation. 

Abundance of trace elements in crustal rocks, sea water and phosphorites (III and IV) ... 

Research in anoxic environments has suggested that some minor and trace elements are precipitated where free dissolved sulfide is present without undergoing a valency change, whereas others undergo a change in valency and are either more efficiently adsorbed onto solid surfaces under oxic or anoxic conditions or are precipitated under anoxic conditions. Therefore, the enrichment of many trace elements relative to their crustal abundances indicates only that the sediments accumulated under anoxic conditions, although not necessarily under anoxic bottom waters. However, Calvert and Pedersen (1993) demonstrated that I and Mn enrichments are reliable indicators of bottom... 

We turn next to consider the nonvolatile alkali and alkaline earth elements and the insoluble components of mineral origin. Their major natural sources are the Earth s crust and the ocean, respectively. We expect the chemical composition of the aerosol to reflect the relative contributions of elements from both reservoirs, provided other contributions from anthropogenic or volcanic sources are negligible. In Section 7.4.4 it has been noted, however, that his premise does not hold for all constituents of the aerosol. Some trace components are considerably enriched compared with their crustal abundances. It is appropriate, therefore, to inquire whether the observations confirm our expectations at least for the major elements listed in Table 7-13, or whether deviations occur also in these cases. As Rahn (1975a,b) has shown, the problem may be approached in two ways, either by calculating enrichment factors defined by... 

I Lead has a crustal abundance of between I0-I5ppm (0.0010-15 per cent). In granites and shales this may rise to 20 ppm. Copper is 5-6 times more abundant and zinc, 7-8 times. However, even these metals are only trace elements when measured in terms of average crustal abundance. See, for instance. Chapman and Roberts (1983) p55. 

Basalts, basaltic andesites, and andesites with this distribution are common in some island arcs (e.g., Jakes and Gill, 1970 Ewart et al., 1973 Taylor et al., 1969). Their presence is believed to result from melting of subducted oceanic crust. By and large, the sediment layers which lie above the ocean floor tholeiites and are derived mainly from continental material are not subducted but piled up against continental margins in some manner that prevents their modifying significantly the trace element and isotopic abundances of oceanic crustal matter in the production of this class of island arc volcanics. Nor does ocean water severely modify the lanthanide distributions in volcanics that are extruded under... 

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