Sedimentary rocks and processes related to them

The bulk present-day mass of sediments is 2.7 x 1024 g, of which 75 is situated within the continents, 15 at the continental margins and 10 on the ocean floor (Ronov, 1982 Hay et al., 2001). The ocean-floor sediments, even though comprising so little of the bulk inventory, are important because their subduction flux constitutes the principal feedback between the upper crustal and mantle reservoirs (Chapters 25 and 27). Sediments are highly variable in their mineralogy and major-element...

Lunar mountains the ancient crust

On the Moon there are two major landforms that can be clearly distinguished even with the naked eye relatively dark plains and light-coloured highlands. The plains are composed of lunar basalts, covering 17 of the lunar surface but constituting only 1 of the lunar crustal mass. The lunar crust, 83 of the lunar surface, forms the highlands. We always see the same side of the Moon because its centre of mass lies 2 km closer to the Earth than its geometrical centre. The conventional explanation of...

The upper continental crust magmatic rocks

The lateral heterogeneity of the upper crust can be seen from space by the naked eye. The rocks exposed at the Earth surface may be readily classified into four major types. (1) Magmatic rocks that formed via partial melting of mantle rocks or oceanic crust. These feed the continental crust the arc-like volcanic chains along the convergent margins of the continents, such as those making up the circum-Pacific belt, bear witness to the major contribution of subduction-zone magmatism in the...

The chronology of planetesimal processing

The cosmochronology of Rb-Sr and the initial 87Sr 86Sr ratios As briefly discussed in Section 10.3, the most common isochron dating methods use measurements of the parameters of Eqn (10.7a) for several different samples that originated (according to a priori data) simultaneously and from the same material. If the samples have remained closed systems, Eqn (10.7a) is valid for each sample, Table 12.3 Average compositions of iron-meteorite chemical groups. From Mittlefehldt et al. (1998)....

The postimpact Earth model

Modelling shows that the giant impact had a major effect on the evolution of the planet. It is expected that the distribution of the impact energy was highly heterogeneous in space and time. The sizes of the target and the impactor imply that both already had iron cores (Section 12.5). The energy released in this process heated the impactor core up to many thousands of degrees, causing it to melt and partially evaporate (the latter process is the most heat consuming) and the temperature of the...

Formation time scales

The oldest date on chondritic material other than CAIs, 4564.7 0.6 Myr, was obtained on chondrules from the Acfer CR chondrite (Fig. 11.6) using the Pb Pb method, which is the most precise absolute chronometer applicable to the early solar system (Section 10.3). Dating of the Ste Marguerite (H4) phosphates resulted in a similar age, 4563.0 0.6 Myr, even though the phosphates are secondary minerals (Fig. 13.1). According to these data, chondrules and chondrites were formed simultaneously within...

The Hadean era 44 to 38 Gyr ago

To reconstruct the rate of mantle fractionation in the Hadean era, we have assumed that this rate (equal to the rate of MORB + OIB production) and the corresponding degassing flux of liquid silicates was intense in early Earth history and then decreased gradually through time down to the present-day value. Taking into account (1) that no significant energy input from external sources (impacts) into the Earth is expected (at least after the late bombardment event at 3.9 Gyr ago), (2) that...

Atomic nuclei and binding energy with some predictions on isotope abundances

Show The Binding Energy Curve

The atomic nuclei are quite small the radius rA of a nucleus with atomic mass number A is about 1.4 x 10-13A1 3 cm. Thus, for the heaviest possible nuclides, rA 10-12 cm. The shape of atomic nuclei varies between spheroidal and ellipsoidal. The whole atom, i.e. the nucleus plus the electronic cloud, is a factor 105 larger. For example, the radius of the first electronic orbit of the hydrogen atom is 0.53 x 10-8 cm. However, the nucleus makes up almost all the mass of an atom. Generally this...

Mantle xenology

Xenon, with its five radiogenic and fissiogenic isotopes, has yielded important clues on the loss of the Earth's earliest atmosphere, as discussed in chapter 20. Here we consider these isotopes in the mantle in order to shed Xe-light on the formation of the noble-gas-bearing ancient mantle reservoir and on the timing and scales of mantle degassing. To do this the parents of the fissiogenic Xe isotopes must be identified, which is possible using the 136Xe 130Xe versus 134Xe 130Xe isotope plot...

Isotopes of Sr Nd and Pb in the continental crust

The continental crust is highly heterogeneous in Sr and Nd isotopes Fig. 27.9 . The positions of MORB and crustal data on opposite sides of the BSE composition clearly show the complementarity between the MORB-source mantle, which is depleted in incompatible elements LREEs and Rb in this case , and the continental crust, which is enriched in these elements Table 17.1 . In the upper crust the present-day s143 values vary from - 10, observed in young mantle-derived granitoids, down to a...

The Evolution Of Matter

From the Big Bang to the Present Day Earth Kola Scientific Centre, Russian Academy of Sciences Institute of Geological Sciences, University of Bern Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title www.cambridge.org 9780521866477 I. N. Tolstikhin and J. D. Kramers 2008 This...