United states government accountability office washington, dc. Best practice guide on the control of arsenic in drinking water. Her research focuses on the origin and evolution of the continents, particularly the lower continental crust and the underlying mantle lithosphere. The former is often 79 considered to be representative of the middle crust bohlen and mezger, 1989 and 80 the latter to be representative of the lower crust rudnick and gao, 2003. United states government accountability office november 19, 2004 the honorable mike dewine. Chemical composition of the continental crust geochemical society. Recent developments on seafloor petrology and tectonics. Pdf composition of the continental crust roberta rudnick. These developed within the framework of a fixist view of continental crust and ocean basins but. The geochemical composition of the terrestrial surface. Earths unique continents apollo 17 view of earth roberta l. Because of a lack in knowledge of the geochemical composition of the terrestrial surface, it is not well understood how the geochemical evolution of the earths crust is. Mclennan, 1995 and recently by rudnick and gao, 2003. Rudnick university ofmaryland, college park, md, usa and s.
Continental crust can be recycled as subducted sediment plank and. Apr 29, 2003 symplicity corporation protests the award of a task order to tmp worldwide, inc. United states government accountability office washington. The terrestrial surface, the skin of the earth, is an important interface for global geochemical material fluxes between major reservoirs of the earth system. The composition of the continental crust the composition of. Ohuen fanerotsooisen alakuoren litologia on vaihtelevampaa kuin prekambrisen alakuoren. Jan 28, 2011 the terrestrial surface, the skin of the earth, is an important interface for global geochemical material fluxes between major reservoirs of the earth system. Earths global ag, al, cr, cu, fe, ni, pb, and zn cycles. Effects of trace metal compositions of igneous intrusions on. H crustal noble he gases abundance nonmetals 5 wt% li b n 0. Gsa data repository 2015244 geological society of america. This value is within uncertainty of those estimated by wedepohl 1995 and rudnick and gao 2003, but is significantly lower than that estimated by taylor and mclennan, 1983, taylor and mclennan, 1985, taylor and mclennan, 1995. Continental and oceanic crust recyclinginduced melt.
In another example, in september 2003 the dc appleseed center for law and justice5 and piper rudnick llp issued a study on special education problems in dcps, which we also discussed in our may 2003 report. Such cumulates may form during arc magma differentiation and possibly densify during subsequent metamorphic reequilibration at high. The geochemical average compositions of distinct lithological classes are. Bulk continental crust composition from rudnick and gao 2003 rg03. If our hypothesis for the syncollisional felsic magmatism is proved to be of general significance, then continental collision zones are ideal sites of crustal growth, which relieves the need. Cammarano 1dipartimento di scienze geologiche, university of roma tre, rome, italy abstract unraveling the temperature distribution and composition of earths crust is key for understanding its origin, evolution, and mechanical behavior. Thus, juvenile material added to the crust must be modi.
Contribution of syncollisional felsic magmatism to. The average value of cd in the study area is 10 times higher than the average crustal values given by wedepohl 1995 and rudnick and gao 2003. Once formed, cc is hard to recycle into the mantle because of its buoyancy rudnick and gao, 2003. Earth and planetary science letters 198 2002 307322 309 collision occurred between the two blocks at 2500 ma followed by rifting during the period of 2300. Regional flow in the lower crust and upper mantle under the southeastern tibetan plateau. This cited by count includes citations to the following articles in scholar. The possibility that both layers are linked by processes of magma fractionation is explored here by considering batholiths upper crust as melts extracted from a parental magma leaving behind a solid residue that can be compared to the rocks of the lower continental crust. Germ reservoir database geochemistry results from rudnick.
Most likely, this difference can be explained by removal of dense, gravitationally unstable cumulates at the base of the arc crust. Photos of underground mining operations, carlsbad, new mexico, intrepid potash company, carlsbad west mine. Potash a vital agricultural nutrient sourced from geologic. Webservices and database support by the san diego supercomputer center supported by scripps institution of oceanography and the. Stein, geological survey of israel, jerusalem, israel. Effects of trace metal compositions of igneous intrusions. Pdf the earth is an unusual planet in our solar system in having a bimodal topography that. The chapter is from the book best practice guide on the control of arsenic in drinking. The ones marked may be different from the article in the profile. Gao chinauniversityofgeosciences,wuhan,peoplesrepublicofchina andnorthwest university,xian,peoples republic ofchina 3. Constraints on the seismic properties of the middle and lower continental crust. Composition of the continental crust request pdf researchgate.
Mcdonough1,2 3 1department of geology, university of maryland, college park, md 20742, usa. Knowledge of the age and composition of the continental crust is essential for understanding. The average concentration of cr in the rock samples is 4. For instance, the measured pwave velocity of the lower crust is typically 6. The chemical composition of the continental crust is critically important for understanding its formation and evolution and, ultimately, understanding earth differentiation. The geochemical composition of the terrestrial surface without. Metal concentrations in the upper, middle, and lower continental crust were taken fromrudnickandgao, 2003. Reos evidence for replacement of ancient mantle lithosphere beneath the north china craton shan gaoa. Early discussions of continental geology focussed on the origins and the development of different rock associations and structures. One is to establish weighted averages of the compositions of rocks exposed at the surface. Data for individual elements are then normalized to the average ucc of rudnick and gao 2003 hereafter referred to as uccrg with the. Analysis of these results provide further evidence that.
Instead, we have performed a series of sensitivity tests of our bcc composition, focusing on the lcc composition, which is the only portion of the crust to show a. Fy 2003 performance report shows continued improvements, gao 04940r washington, d. Zhi wang, runqiu huang, jian wang, shunping pei, wenli huang. Rudnick and gao 2003 measured global iridium concentrations of 0. In the following, the mcc and lcc together will be described as the 103 deep continental crust. For instance, the measured pwave velocity of the lower crust is.
Although not normally classified as a geochemically. Mcdonough1,2 3 1department of geology, university of maryland, college park, md 20742, usa 4 2department of earth sciences and research center for neutrino science, tohoku university, sendai 5 6 9808578, japan 7 key points. Magnesium isotopic composition of the deep continental crust. A vital agricultural nutrient sourced from geologic deposits. Constraints on the seismic properties of the middle and.
Theconcentrationofmetalin the oceanic crust is available for most metals wedepohl and. The composition of the continental crust the composition. Rudnick, 1992 as well as the primitive island arc basaltlike incompatible element content of the bulk lower crust e. Impacts, megatsunami, and other extraordinary claims. Two approaches have generally been used to determine the composition of the upper continental crust ref. Roberta rudnick is a professor in the department of earth sciences at the university of california, santa barbara. Reos evidence for replacement of ancient mantle lithosphere.
Evidence from modern arcs indicates that more felsic compositions arise because the ma. Solo30000003, issued by the office of personnel management opm, for online federal employment information services. Generation of new continental crust by sublithospheric. Lower crustal composition in the southwestern united states. Mareschal, 2003 or may assimilate felsic xenoliths. We sustain the protest because opm did not adequately consider. Such reaction may produce an olivinefree pyroxenite, which, if subsequently melted, will generate basaltic melt kogiso et al. The average concentration of cd in the rock samples is 0. The composition of the continental crust the composition of the. The average value of cr in the study area is lower than the average crustal values given by taylor and mclennan 1995, wedepohl 1995 and rudnick and gao 2003. Solid earth 1 lower crustal composition in the southwestern united 2 states l. This technique allows estimation of the bulk composition and associated uncertainties with all samples taken into account.
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