Crust mass

Carlson R. W. and Hauri E. (2003) Mantle-crust mass balance and the extent of Earth differentiation. Earth Planet. Set Utt. (submitted 2002). 

Fig. 3. Some results of previous modelling, (a) Crustal growth scenarios used (curves give crust mass existing at times in the past relative to present-day continental crust mass of 2.1 x lO g (Taylor McLennan 1995). (b) V. Pb/ Pb plot showing modelling...

Fig. 4. (a) Crust mass v. time curve used in the present study, a simplified version of curve A in Figure 3a. 

Variations on a theme a single crust mass V. time curve... 

First, the total amount of crust-to-mantle recycling is defined by R, the time-integrated recycling mass flux over Earth history expressed as a fraction of present-day crust mass ... 

Second, it is assumed that the recycling mass flux and its ancillary trace species fluxes are at any time dependent on the amount of crust in existence at that time. This dependence can take the form of various functions, and a variable geometry parameter E is introduced, which describes the crust to mantle recycling flux (t)recycimg function of crust mass in existence. 

For any given crust mass v. time curve, the two parameters R and E determine the bulk crust formation and the crust recycling (erosion) fluxes through time, as... 

Further, the erosion law factor K, defined in equation (4), regulates the age distribution of eroded material relative to the age structure of the crust. Thus for a given crust mass v. time curve, the three parameters E, R and K fully describe the crust formation and erosion history. In the present modelling E was varied between 0.2 and 1, R from 0.3 to 0.7, and K from 1.5 to 3.5. The approach used and the effective partition coefficients, as well as initial (meteori-tic) concentrations of the trace species are the same as those used by Kramers Tolstikhin (1997) and Nagler Kramers (1998). 

Following this result, the total amount of crust recycled by erosion into the mantle would be about 60% of the present crust mass (R 0.6). This is not in conflict with any known geochemical data. An apparent contradiction exists with a maximum value of 30% derived from the mass balance of Ar in the atmosphere and K in the continental crust by Coltice et al. (2000). The argument used by these workers was based on the assumption that the amount of Ar in the atmosphere and the continental crust combined is equal to or greater than that generated over geological time by the amount of K that has ever been in the continental crust by (equation (3)... 

The sedimentary rock data provide information only on that portion of the crust exposed to weathering and erosion, but the upper crust is not representative of the entire 41-km thickness of the continental crust. Mass balance calculations show that a 41-km thick crust with K, Th, and U abundances equal to that of the present upper continental crust would require about 80-90% of the entire Earth s complement of these elements to be present in the continental crust. The heat-flow data show that the upper crust (about 10 km thick) is strongly enriched in the heat-producing elements (K, U, and Th). 

Although iron is only about two-thirds as abundant as aluminum in Earth s crust, mass for mass it costs only about one-quarter as much to produce. Why ... 

Crust Mass (g) Oceanic 5.0E+24 Lower 8.33E+24 Middle 9.63E+24 Upper 6.13E+24 Total 2.9E+25 Cosmo- genic IDP Oceanic 5.00E+24 Lower 8.33E+24 Middle 9.63E+24 Upper 6.13E+24 Cosmo- genic Total %of Atmosp. Atmosph. (0 P83)... 

The thin outer layer of Earth, called the crust, contains only 0.50 percent of Earth s total mass and yet is the source of almost all the elements (the atmosphere provides elements such as oxygen, nitrogen, and a few other gases). Silicon (Si) is the second most abundant element in Earth s crust (27.2 percent by mass). Calculate the mass of silicon in kilograms in Earth s crust (mass of Earth = 5.9 X 10 tons 1 ton = 2000 lb 1 lb = 453.6 g). 

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