Crustal reworking

Knudsen T.-E., Griffin W. E., Hartz E. H., Andersen A., and Jackson S. E. (2001) In-situ hafnium and lead isotope analyses of detrital zircons from the Devonian sedimentary basin of NE Greenland a record of repeated crustal reworking. Contrib. Mineral. Petrol. 141, 83-94. 

McDermott F., Harris N. B. W., and Hawkesworth C. J. (1989) Crustal reworking in southern Africa constraints from Sr-Nd isotope studies in Archean to Pan-African terranes. Tectonophysics 161, 257-270. 

Sawyer E. W. (1998) Formation and evolution of granite magmas during crustal reworking the significance of diatexites. J. Petrol. 39, 1147-1167. 

Choukroune, P., Bouhallier, H. Arndt, N. T. 1995. Soft lithosphere during periods of Archaean crustal growth or crustal reworking. In Coward, M. R. Ries, A. C. (eds) Early Precambrian Processes. Geological Society, London, Special Publications, 95, 67-86. 

The sedimentary and metamorphic rocks uplifted onto land have become part of continents or oceanic islands. These rocks are now subject to chemical weathering. The dissolved and particulate weathering products are transported back to the ocean by river runoff. Once in the ocean, the weathering products are available for removal back into a marine sedimentary reservoir. At present, most mass flows on this planet involve transport of the secondary (recycled) materials rather than the chemical reworking of the primary (juvenile) minerals and gases. The natirre of these transport and sediment formation processes has been covered in Chapters 14 through 19 from the perspective of the secondary minerals formed. We now reconsider these processes from the perspective of impacts on elemental segregation between the reservoirs of the crustal-ocean-atmosphere factory and the mantle. 

Downes H., Peltonen P., Manttari I., and Sharkov E. V. (2002) Proterozoic zircon ages from lower crustal granulite xenoliths. Kola Peninsula, Russia evidence for crustal growth and reworking. J. Geol. Soc. 159, 485-488. 

Any successful model of varnish formation, however, must also explain additional issues associated with varnish chemistry. First, iron is enhanced slightly in varnish over crustal and adjacent soil concentrations. Although most of the iron derives from the clay minerals, some is biotically enhanced (see Figure 8.7 and Dorn and Oberlander, 1982 Adams et al., 1992 Sterflinger et al., 1999) as the nanometre-scale Fe seen in the bacterial casts (Krinsley, 1998) is also found reworked into the weathered remnants of clay minerals seen in HRTEM imagery. Considerable HRTEM work, however, is needed to better document processes of minor iron enhancement. 

The age distribution of crustal rocks An estimate of the relative volumes of continental crust of different ages is an obvious way to assess crustal growth models. However, making such an estimate is not straightforward for two reasons. First, it cannot be assumed that the age of the continents is the same at depth as it is at the surface (Corfu, 1987). Second, the reworking of older crust... 

Although major crustal fractures at depth may provide entry to the upper crust for metalliferous granites, the later hydro-thermal reworking of uranium and associated metals to form vein-type mineralization after emplacement requires the development of a mesh of fractures in the upper crust capable of transmitting large volumes of fluid through both the granites and their envelopes. The swarms of mineral lodes that occupy... 

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