Karl Hans Wedepohl

Distribution of the Elements in Some Major Units of the Earth's Crust

This paper presents a table of abundances of the elements in the various major units of the Earths lithic crust with a documentation of the sources and a discussion of the choice of units and data.

Spurenanalytische Untersuchungen an Tiefseetonen aus dem Atlantik: Ein Beitrag zur Deutung der geochemischen Sonderstellung von pelagischen Tonen

Abstract The data from these minor element investigations of Atlantic bottom samples shall contribute to a geochemical comparison of pelitic sediments from different oceans. General considerations about the source of abnormally high abundances of some elements in pelagic clays in comparison with near-shore argillaceous sediments should depend on representative data of best quality. Therefore only methods of X-ray fluorescence, d.c.-arc spectroscopy and colorimetry with less or about 10 per cent standard deviation have been applied for this investigation. Eighteen samples and two composites (with no or moderate carbonate content) have been analysed for the following minor elements: Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Mo, Ba, La, Pb. Data of the same elements in near-shore clays and shales have been revised and supplemented. Some analyses of Pacific samples could be checked. The main result of this investigation is the grouping of elements into three classes with different geochemical behaviour: 1. (a) The average abundances of Ti, V, Cr, Ga, Rb and Zr are the same in near-shore and pelagic clays within the limits of analytical error. 2. (b) On the average the elements La, Sc, Y and Ba are as abundant in near-shore clays as in pelagic clays from the Atlantic but are more abundant in those from the Pacific. 3. (c) The average abundances of Zn, Ni, Pb, Cu, Co, Mn and Mo increase from near-shore argillites to Atlantic clays and from there to Pacific clays regardless of similar composition in their major elements. The fact that elements like Ti, V, Cr are not enriched in these clays shows that there is no enhanced contribution from submarine weathering of volcanics and pyroclastics. For the discussion of higher abundances of Group B elements in Pacific clays one should consider the evidence of organic contributions to the sediment and mobilization during diagenesis. The abundances of the Group C elements in clays from the two oceans exceeding that of near-shore argillites are presented in a diagram. It shows a striking proportionality between the sediments from the Atlantic and the Pacific in relation to the abundances of these elements. This should be interpreted as the result of one uniform process. Most of these elements exceed the values required for balance computations of weathered average crust material, if the portion of pelagic clays in all the sediments is estimated as 10 per cent. This figure of 10 per cent is supported as a minimum by geological and geophysical experience. Extraterrestrial sources cannot supply the above-mentioned element association in the abundances established. However, this association seems to be typical for volcanic exhalations. An influence of the secular air-contaminating action of these emanations on sediments with a rate of sedimentation in the range of mm per thousand years must be taken in account according to thermodynamical and geological evidence. The proportion 1: 3·4 in the diagram probably reflects the different average rates of sedimentation in the two oceans.

Untersuchungen am Kupferschiefer in Nordwestdeutschland; Ein Beitrag zur Deutung der Genese bituminöser Sedimente

Zusammenfassung Nach der Auswertung von Literaturdaten bituminoser Sedimente wurden fur deren Genese charakteristische Elemente zur Untersuchung des Kupferschiefers ausgewahlt. Es standen Bohrkemproben aus Nordwestdeutschland zum Vergleich mit dem Gebiet der Lagerstattenvorkommen um Mansfeld-Richelsdorf zur Verfugung. Der Mineralbestand und die Gehalte an CO2, C, S, B, Ti, V, Cr, Mn, Fe, Co, Ni, Ou, Zn, As, Rb, Sr, Mo, Ba und Pb wurden in den meisten der rund 50 Proben quantitativ bestimmt. Der Karbonatanteil liegt m dem braunschwarzen, feingeschichteten, meist 20–50 cm machtigen Mergel bei 30%. In kustennahen Ablagerungen herrscht Dolomit im kustenfem gebildeten Sediment Calzifc vor. Die Karbonatart kann im Profil wechseln und wird als Produkt fruher Diagenese gedeutet. Der relativ hohe Mn- und der niedrige Sr-Gehalt ist dem. Karbonatgehalt proportional. Zwischen den Anteilen der uberwiegend detritischen Silikate, des Quarz (diagenetisehe Neubildung von Albit und Chlorit moglich) und den meisten der oben genannten chemischen Bestandteile ist keine Beziehung festzustellen. Erwartungsgemass hengt der B- und Rb-Gehalt von der Illitmenge im Kupferschiefer ab. Die V-, Cr- und Ni-Konzentrationen sind mit relativ geringer, die Mo- und Co-Konzentrationen mit grosserer Streuung den Kohlenstoffgehalten proportional. Diese Proportionalitat und die Herkunft der grossen Metallmengen wird als Ergebnis erhohter und durch Reaktion und Adsorption an Reste organischer Substanz gebundener Meerwassergehalte diskutiert. Die Sulfidkonzentrationen des Kupferschiefers stehen in keiner Beziehung zu den Kohlenstoffgehalten. Die regionale Verteilung der Sulfide des Cu, Pb und Zn zeigt eine Konzentrierung im mitteldeutschen Becken. Die Verbreitung hoher Gehalte nimmt in dieser Reihenfolge der Elemente zu. Es gibt auch im norddeutschen Becken ortlich grosso Sulfidmengen (meist im Kustengebiet). Im Nordwesten des Transgressionsgebietes mit den wahrscheinlich starksten marinen Einflussen sind die Cu- Pb- und Zn-Werte des Kupferschiefers so niedrig wie in vielen anderen bituminosen Tonen. Verschiedene Profile einander weit entfernter Lokalitaten zeigen eine fur die Diskussion der Genese wichtige Ahnlichkeit in der vertikalen Verteilung der Metalle und Erze, die Ausscheidungsfolge: Cu/Ag, Pb, Zn. Die Bedingungen der H2S-Bildung im stagnierenden Meerwasser und der Fallung von Sulfiden werden nach rezenten Beispielen bzw. Daten der Loslichkeit besprochen. Da eine Bilanzrechnung zeigt, dass “nonnales” Meerwasser zur Liefenmg der Metallmengen im Kupferschiefer nicht ausreicht, steht hauptsachlich eine durch den Fazieswechsel “Red-Bed”-und Sapropel-Sediment bedingte Mobilisierung von Stoffbestand zur Diskussion. Der Nachweis der Fixierung fur den Kupferschiefer charakteristischer Elemente durch die Eisenoxyde roter Sandsteine und die Moglichkeit ihrer Mobilisierung durch Reduktion des Fe3+ macht die Zufuhren aus Rotliegend-Sedimenten in das stagnierende Wasser vorstellbar. Diese Vorstellungen werden mit zahlreichen geologischen Beispielen belegt. Alle fur die syngenetische Metallanreicherung im Kupferschiefer sprechenden Befunde sind in einem besonderen Abschnitt zusammengestellt worden. Ein starkes Argument fur die Syngenese ist die gleichmassige, horizontbestandige Verbreitung hoher Metallgehalte in einem geringmachtigen, gegenuber zirkulierenden Losungen sehr wenig durchlassigen Sediment. Begrenzte sekundare Umlagerungen des Mineralbestandes und aszendente Zufuhren konnen ortlich diese Deutung erschweren.

The potential source of lead in the Permian Kupferschiefer bed of Europe and some selected Paleozoic mineral deposits in the Federal Republic of Germany

New lead isotopic compositions have been measured for Paleozoic bedded and vein ore deposits of Europe by the high precision thermal emission (triple filament) technique. Eleven samples have been analyzed from the Upper Permian Kupferschiefer bed with representatives from Poland to England, three samples from the Middle Devonian Rammelsberg deposit and one from the Middle Devonian Meggen deposit, both of which are conformable ore lenses and are in the Federal Republic of Germany (FRG); and also two vein deposits from the FRG were analyzed, from Ramsbeck in Devonian host rocks and from Grund in Carboniferous host rocks. For Kupferschiefer bed samples from Germany, the mineralization is of variable lead isotopic composition and appears to have been derived about 250 m.y. ago from 1700 m.y. old sources, or detritus of this age, in Paleozoic sedimentary rocks. Samples from England, Holland, and Poland have different isotopic characteristics from the German samples, indicative of significantly different source material (perhaps older). The isotopic variability of the samples from the Kupferschiefer bed in Germany probably favors the lead containing waters coming from shoreward (where poor mixing is to be expected) rather than basinward (where better mixing is likely) directions. The data thus support the interpretation of the metal source already given by Wedepohl in 1964. Data on samples from Rammelsberg and Meggen tend to be slightly less radiogenic than for the Kupferschiefer, about the amount expected if the leads were all derived from the same source material but 100 to 150 m.y. apart in time. The vein galena from Ramsbeck is similar to that from Rammelsberg conformable ore lenses, both in rocks of Devonian age; vein galena from Grund in Upper Carboniferous country rocks is similar to some bedded Kupferschiefer mineralization in Permian rocks, as if the lead composition was formed at about the same time and from similar source material as the bedded deposits. Although heat has played a more significant role in the formation of some of these deposits (veins and Rammelsberg-Meggen) than in others (Kupferschiefer), there is no indication of radically different sources for the lead, all apparently coming from sedimentary source material containing Precambrian detritus. One feldspar lead sample from the Brocken-Oker Granite is not the same in isotopic composition as any of the ores analyzed.

Untersuchungen zur Geochemie des Bleis

Abstract After discussing literature on the geochemical distribution of lead, a quantitative spectrochemical method is described (0.01% Bi standard). The sensitivity of 0.0001% Pb is attained by relative concentration of light volatile elements with a double-arc instrument. In this investigation more than 500 analyses for lead of representative samples are discussed (more than 250 own determinations). During the last 3.3 . 109 years the total amount of lead of the earths crust has increased only by 20% from radiogenic sources. The average lead content of micas and potassium feldspars (~0.0025%) surpasses that of the lithosphere (0.0015%). Remarkable amounts of 0.010% Pb are gathered in the feldspars of pegmatites. Olivine and quartz (excepting rose-quartz) have the lowest contents (~0.0001% Pb); those are expected after their structural properties. Lead replaces potassium in its structural positions owing to similar ionic dimensions. In the course of magmatic differentiation the proportions K/Pb and Ba/Pb are increasing, only excepting some late minerals. Adulars, feldspathoids and zeolites are favoured in the replacement of K, Na and Ca. The feldspars contain the main lead content of eruptive rocks. The following figures are average Pb abundances of a great number of samples: granite 0.0019%, granodiorite 0.0015%, diorite 0.0010%, basalt 0.0006%, ultrabasic rocks 0.0003%. Galena seems to be a very rare compound in normal rocks. The behaviour of lead in rock alteration (weathering, mobilization, concentration, etc.) is discussed. Factors for concentration are low solubility (PbS, Bleiphosphat adsorption (clay minerals, Mn hydroxides, ferric hydroxides) and action of organisms (foraminiferae, plants, etc.). The clay minerals contain the bulk of lead in sediments. The relative high contents of Pb, Zn and Cu of pelagic sediments cannot have been derived entirely from continental weathering. It must be assumed that a part is due to volcanic exhalations. The following averages are results of sediment analyses: nonpelagic argillaceous rocks 0.0020%, deep-sea clays (Atlantic Ocean) 0.0043%, deep-sea clays (Pacific Ocean) 0.014%, sandstones 0.0007%, limestones and dolomites 0.0009% Pb. Part of the lead content of metamorphic rocks can be derived from their parent material. It increases from greenschists, amphibolites, granulites (0.0010%), to mica-schists and gneisses (0.0023% Pb). A number of lead analyses from specific minerals of metamorphic rocks are reviewed. Natural environments very rarely permit the formation of Pb . The Goldschmidt rules on the relationships between distribution of an element and its ionic dimensions and ionic charge give a sufficient explanation of most geochemical characteristics of lead.

Untersuchungen zur Geochemie des Zinks

Abstract A spectrochemical method for the determination down to 10 −4% Zn in numerous rocks and minerals has been developed. By means of fractionated distillation the separation of Zn occurring in silicates and spinells from Zn in ZnS-bearing rocks has been made possible. The result of 130 analyses confirms the figures given by Clarke-Washington (1924) (0.004%Zn) and the unpublished results by V.M. Goldschmidt (1938) (≤ 0,004% Zn) for the abundance of Zn in the lithosphere.

Untersuchungen an spilitischen Gesteinen der variskischen Geosynkline in Nordwestdeutschland

Abstract21 samples of spilitic rocks of Devonian to Carboniferous age from NW-Germany have been analyzed for major elements, a large group of minor elements and the modal mineral composition. Their major element and mineral composition is comparable to Recent spilites from oceanic ridges. Major emphasis has been given to the absolute and relative abundance of the lanthanides and yttrium. Their pattern, which is most probably not altered during processes of spilitization is that of tholeiitic basalts occuring on the continents and in oceanic islands.Spilitization of the rocks under investigation is explained as a metamorphic process in a partially open system (loss of Si, Ca, and gain of H2O, CO2, Na) in a temperature range from 200° to about 400° C. Most abundant new minerals are: albite and chlorite; basaltic relict minerals are: plagioclase (high in Ca) and diopsidic pyroxene. Minerals typical for the temperature range mentioned are: prehnite, pumpellyite, actinolithe, epidote biotite. Microprobe analyses of several typical minerals are listed.

General trends in the behavior of Cd, Hg, Tl and Bi in some major rock forming processes

Abstract Neutron activation data on Cd, Hg, Tl and Bi in 45 samples of abundant magmatic, sedimentary and metamorphic rocks and rock composites (consisting of a total of more than 200 samples) are reported. American standard rocks are included. On the base of literature values and the data of the present publication one arrives at the following average abundances for magmatic rocks in the upper continental crust: 110 ppb Cd, 30 ppb Hg, 970 ppb Tl, 60 ppb Bi and for sedimentary rocks: 260 ppb Cd, 330 ppb Hg, 830 ppb Tl, 375 ppb Bi. Abundance ratios for sedimentary to magmatic rocks are: 12 for Hg, 6 for Bi and 2·4 for Cd; the relative accumulation of the three elements in the sedimentary environment is assumed to be due to the degassing of the earth (excess volatile elements). In a thermal gradient of regional metamorphism from sedimentary to lower amphibolite facies a decrease of Hg, Bi and Cd from sedimentary abundances down to the range of “magmatic” abundances has been observed.

Geochemical characterization and origin of granitoids from the South Bohemian Batholith in Lower Austria

Major and 31 minor elements have been determined in 39 large samples of Variscan granitoids from 6 plutons or intrusions from the South Bohemian Batholith (Rastenberg, Weinsberg, Mauthausen, Schrems, Eisgarn and Gebharts). The granitoids are mainly granites but also diorites, tonalites, trondhjemites, granodiorites. Average concentrations of Ba, Th, U, La, Ce, Pb, Nd, Sr and K in the Weinsberg, Mauthausen and Schrems granites exceed those in average felsic I- and S-type granites by factors ranging between 2.1 and 1.3. The granites melts formed at waterundersaturated conditions and intruded at 10 to 15 km depth during late-tectonic and post-tectonic phases of the Variscan orogeny (about 330 to 300 Ma ago). Hydrothermal or low temperature alteration is excluded for the majority of samples from a study of oxygen isotopes. The thickness of the plutons is estimated at about 6 km from heat balance constraints. By analogy with experimental partial melting, three different sources of the granitoids can be identified and chemically characterized: (1) The trondhjemites, tonalites and diorites in the early Rastenberg pluton are products of 15 to 40% melting respectively of a mafic (partly amphibolitic) lower crust. Redwitzites from the West Bohemian Massif which are comparable in age partly resemble the Rastenberg rocks. The mafic sources of the Rastenberg granitoids and redwitzites are crustally contaminated as reflected in their Sr-Nd isotopes. (2) The very large syn-tectonic Weinsberg pluton was formed from about 30% partial melting of a tonalitic lower crust at 800 to 850°C. Its low proportion of ca. 10% restite has a ferrodioritic composition. The post-tectonic fine-grained Mauthausen and Schrems granites which tend to a granodioritic mode, are very low in restite and are also products of melting of a tonalitic source. (3) The youngest (leuco-)granite, the Eisgarn pluton (high in Si, P, Li, Rb, Cs, U,87Sr/86Sr and low in Ca, Sr, Ba) reflects a pelitic source. The change from mafic to tonalitic to pelitic source composition for the granitoid sequence may indicate that the depth of melt formation decreased with time. The concentration of heavy rare earth elements decreased from Weinsberg to Eisgarn granites which indicates an increasing proportion of garnet in the source. The orogenic heat conformable with a heat flow of about 100 mWm-2 was provided by mafic intrusions. An alternative would be a drastic increase of the crustal thickness which cannot be recognized by barometry of the associated metamorphic rocks. Exposed metamorphic country rocks occur in higher amphibolite facies indicating about 5 kbar pressure. Mafic intrusions contain gabbros (Kleinzwettl) or have formed (quartz-)diorites (Gebharts), the latter being contaminated by granitic melts from partial melting of the wall rocks (MASH process). Largescale contamination by crustal materials can be observed in δ18O and in Sr-Nd isotopes. The major mafic activity was probably caused by depression of solidus temperatures in the mantle wedge above a subduction zone where water was available from dehydration of subducted ocean crust. This water initiated partial melting of ultramafic rocks and metasomatism in the uppermost mantle above the level of melting. The water also mobilized highly incompatible elements (Ba, Th, U, La, Ce, Pb, Nd, Sr and K) from the uppermost mantle and transported them into the lower crust. Indicators of a nearby subduction or collision zone of Late Variscan age in addition to the specific association of granitoidal rocks are abundant upper mantle tectonites. An alternate or additional source of metasomatic fluids may have been dehydration of lower crustal rocks during Variscan high-grade metamorphism.

Strontium isotope studies on young volcanic rocks from Germany and Italy

Abstract87Sr/86Sr ratios of Tertiary tholeiitic, basalts alkali olivine basalts and olivine nephelinites from Lower Saxony and Hessia and Quaternary leucite-nepheline tephrites from the Laacher See area are similar to those obtained from Hawaii and range from 0.7031 to 0.7054. Three trachytes and one phonolite from the Westerwald and one phonolite from the Laacher See area have higher values (0.7063 to 0.7093). Three Vesuvian lavas, three Somma lavas and two trachytes of the Phlegraic Fields show substantially higher ratios than the comparable basaltic rocks from N.W. Germany (0.7071 to 0.7102). Three peridotite nodules vary between 0.7048 and 0.7081. Three limestone composites of Paleozoic and Mesozoic age show values between 0.7129 and 0.7174.The 87Sr/86Sr ratios of the trachytes and phonolites from the Westerwald and Laacher See area are probably influenced by crustal material. Assimilation processes of limestones producing the olivine-nephelinites from N.W. Germany seem to be unlikely. A discussion of the origin of the Sr ratios in Vesuvian rocks and of mantle homogeneity is included.