(b. Lunteren, Netherlands, 1 January 1903; d. Bilthoven, Netherlands, 12 November 1979)
Willem Nieuwenkamp was the second of four children (and the only son) born to Anna Wilbrink, daughter of an old Dutch landed family, and Wijnand Otto Jan Nieuwenkamp, a painter and engraver. A large part of his early life was spent on the water in the family’s elegantly appointed houseboat, de Zwerver, a full 100 feet long, wintering on the Dutch canals and cruising up the Rhine to Basel and back in summer. His quick intelligence showed itself in primary school, where, on finishing his assigned work before the other children, he would ask and receive the teacher’s permission to do somersaults up and down that aisle the divided the schoolroom.
In 1922 the Nieuwenkamps moved to Rome, and in 1926 they settled in San Domenico di Fiesole, outside Florence, in the villa Riposo de’ Vescovi, Nieuwenkamp had entered the University of Utrecht in 1919, and remained in Holland to complete his studies, spending vacations in Italy with the rest of the family. Despite an early interest in astronomy (which he never lost), he chose to study geology, seeing behind its then preponderantly descriptive and systematic character a future opportunity for exciting theoretical advances. His formal studies ended with the doctoraal examination in 1926, and he received the D.Sc. degree (cum laude) in 1932 for a dissertation on the crystal structures of lead bromide and lead fluorobromide. In 1947 he was appointed professor of mineralogy, crystallography, and petrology (later of geochemistry) at Utrecht, and held this post until his retirement in 1968. In 1965 he was elected to the Royal Netherlands Academy of Sciences.
Nieuwenkamp’s early experiences were varied and practical. After a year in Patagonia with an oil company, he went in 1933 to Göttingen as assistant to V.M. Goldschmidt, and later worked on gravity measurements, first with F.A. Vening Meinesz in submarines and then, with the onset of war, on land with a bicycle. But his thoughts were never far from the large-scale theoretical problems of geology that were waiting for solutions. His voyage to South America may have sparked an interest in global tectonics; a map drawn by him in this period shows the Atlantic continents assembled with their major tectonic lineaments restored. In these prewar years (1932–1937), he followed up his dissertation with ten papers on crystallographic subjects that included structure determinations on several halogen salts and on cristobalite. However, his abiding preoccupation was with the need for a satisfactory theory of the origin of rocks. Quick to see the logical flaws in classical magmatism (then still the orthodox view of petrogenesis), he traced it back to its origins in the neptunist-plutonist debate of 150 years before, looking for where it had gone wrong. This notorious controversy had ended in a posthumous victory for James Hutton in which, ironically, his cyclic picture of the earth’s metabolism was all but blotted out by the magma that had defeated Abraham G. Werner’s neptunists. On this magmatic tide Justus Roth then floated a new school of geology in Germany; it prospered and developed under Harry Rosenbusch into what is now called classical magmatism.
Classical magmatism postulated that the primitive crust of the earth had been made of magmatic rocks congealed from the supposedly molten globe. These igneous rocks were then weathered to produce sediments, which accumulated at the surface, and soluble cations (among them sodium), which accumulated in the sea. The loss of igneous rocks to weathering was made good by fresh eruptions, from the still molten interior, of what became known to the later magmatists as “juvenile” magma, that is magma fresh from the mantle, never before having seen the light of day. This contrasted with the Huttonian view, according to which the magma, being made of melted sediments, was resurgent. Classical magmatism admitted, however, that buried sediments could be subjected to heat and stress and converted into metamorphic rocks recognizable by their foliated or banded appearance. This could happen to igneous rocks, too, so that sedimentary and igneous rocks could become indistinguishable when metamorphosed. There was orthogneiss from granite, and paragneiss from mud. But magma was paramount. Hundreds of different kinds of igneous rocks were discovered, examined, and classified with materialistic zeal.
Sedimentation was thus viewed as an essentially secular process. Estimates of the earth’s age based on this view, whether derived from the supposed mass of the sedimentary rocks (T. M. Reade) or the amount of sodium released on their formation from igneous rocks and now in the sea (J. Joly), had agreed faily well with Lord Kelvin’s result from the supposed cooling history of the earth. But they did not accord with the radiometric dates that began appearing on the geologic time scale a decade or two later and that by Nieuwenkamp’s day indicated that all of the sodium now in the sea could have accumulated, at the present rate, since some time in the Cretaceous Period. F. W. Clarke in 1908 calculated the mass of sediment that should correspond to the sodium now in the sea, and V. M. Goldschmidt repeated the calculation, with some refinements, in 1933. Their results were essentially the same: enough to spread an even layer 2,000 meters thick over the land surface of the earth. At the time, no one seemed troubled by this outcome, which was so paltry in contrast with the observed mass of sediments of the earth’s crust.
The confining war years extended Nieuwenkamp’s command of the literature and ripened his ideas. Exhaustive reading of Hutton and John Playfair, and of their opponents in the Wernerian Society, and careful study of field observations, especially those of the great Scandinavian geologists, such as Pentti E. Eskola and Johannes J. Sederholm, drew Nieuwenkamp to the neo-Huttonian viewpoint from which he later created the “persedimentary hypothesis” that came to be associated with his name. After the war he was able to travel and see for himself. Detailed studies of granitic bodies and their field relations in Spain and in the Massif Central of France made it clear that many granites had originated from sedimentary rocks, an idea that is commonplace today but was still controversial in 1950. These field studies formed the subject of a number of doctoral dissertations at Utrecht, and the sedimentary heritage of granite made it the starting point for a new approach to petrogenesis through the “continuous rock series.” No rock can be defined in a natural way; each grades imperceptibly in character into its neighbors, and all together form acontinuum. In an article published in 1968 he wrote: “We need only suppose that the rocks have been formed somehow in order to get convinced that it will be hard to ascribe two diametrically opposed derivations to two rocks … lying close together in the series” (p. 367). If orthoamphibolite was formed by metamorphism of basalt erupted from the mantle, what of paraamphibolite derived from marl, if one could not tell the difference between them?
Nieuwenkamp developed his ideas in a sporadic series of papers and in conversations with European geologists who, like himself, saw the difficulties of classical magmatism and welcomed “persedimentarism” as an alternative working hypothesis. Prominent among these were T. F. W. Barth, A. Holmes, E. Raguin, and H. G. F. Winkler, all of whom were strongly influenced by Nieuwenkamp and carried his influence into the general current of European geologic thought. He drew attention to the sodium problem at the International Geological Congress at London in 1948. Until then, nobody had seriously questioned Clarke’s and Goldschmidt’s poor sediment yield from the sodium calculation, although some (including Holmes, a pioneer in radiometric age measurement) had begun to suspect the reason why Joly, using the same argument before them, had failed to get a reasonable age for earth.
The chief significance of this paper, “Geochemistry of Sodium,” was that it brought the “sodium problem” into juxtaposition with another question that had been recognized more recently by the Scandinavians and others working on granitic terrains that were clearly of sedimentary origin: What was the source of the sodium that had created these rocks out of mudstones and shales? The answer of classical magmatism was unsatisfying: It was brought in a hypothetical “ichor” of (juvenile) magmatic origin that arose from the earth’s interior and pervaded the sediments. A few years earlier S.J. Shand had criticized this ad hoc invention and suggested that the sodium had been there all the time, in connate pore water. For Nieuwenkamp, these possibility that thse two problems might be solvable at one stroke by closing a loop in the sodium cycle between the ocean (losing sodium) and the metasediments (gaining it) through marine sediments carrying entrapped sodium opened a line of thought whose destination was not yet clear:
In the original plutonism of Hutton, the magma consisted of melted sediments. It would be an interesting historical study to see how it came about that this origin has been rejected. . . . The whole interest which could be derived from such an investigation depends on whether anything more definite can be postulated, than merely that every rock or lava once has been a sediment (1948).
The idea is developed further in “Géochimie classique et transformiste” (1956), which begins with the calculation of a geochemical balance between igneous rocks on the one hand and sediments and seawater on the other. Uncertainty about the proportions of shale, sandstone, and limestone in the sedimentary reservoir is ingeniously sidestepped by expressing the abundance of each element (as its lowest oxide) in terms of alumina, whose virtually exclusive occurrence in the clay fraction of sediments (of whatever kind) reduces the problem to comparison of the average igneous rock with the average clay. Among the seven major elements, the only significant discrepancies are in magnesium, calcium, and sodium. The missing calcium and magnesium are inadequate to account for any reasonable estimate of the proportion of carbonate rocks to shales unless the Precambrian sediments and metasediments (poor in carbonates) are included; but this makes the case of sodium much worse than before: The amount found in the sea is far too small, and the earth’s sedimentary cover is far too thick, to agree with classical magmatism.
Next, the continuous rock series is examined at the convergence of gneiss and granite. Here is a dilemma: If a granite and a gneiss of similar composition are found side by side, no one will readily admit that their origins have nothing in common. Either most of the granite comes from a juvenile magma whose alkaline exhalations have transformed the adjoining sediments into gneiss and, eventually, granite (classical magmatism), or the gneiss is entirely of sedimentary origin (the sodium congeneric, having been held in pore water and on clay minerals). Then what are the odds that a granitic magma of the same composition happened to arrive from the depths of the earth and congeal just beside it? Surely the odds are much longer than that some of the gneiss melted and congealed to form granite.
Once on [that] road, there’s no stopping. If the granite was formed entirely from sediments, it seems absurd to postulate a juvenile source for rhyolite. There is no sharp line between granite, diorite and gabbro. If granite is made from sandy clay, marly clays make more basic rocks. Associations of amphibolites, basic [eruptive] rocks and metamorphic limestones are common too. Amphibolites and gabbros pose the same problem as gneisses and granites (1956, pp. 419–420).
Nieuwenkamp stops short of denying altogether the existence of juvenile magmas; instead he advances the persedimentary hypothesis as a “clear, unequivocal starting point for petrogenetic and geochemical interpretations,” an antithesis to classical magmatism, so that the two can be compared in regard to their predictions concerning geochemical and petrologic data.
As an example, the distribution of some refractory elements (such as aluminum) and some mobile ones (such as boron) between different geologic reservoirs (igneous rocks, metamorphic rocks, sediments, hydrosphere, atmosphere) is examined from each viewpoint. For both, the refractory elements should be distributed in essentially the same manner: more or less equally among the three rock reservoirs, scarce or absent in the hydrosphere and atmosphere. With the volatile elements it is otherwise. They should be scarce in igneous and metamorphic rocks (depending on their mobility), and distributed instead among sediments, hydrosphere, and atmosphere according to their individual propensities. But here the two models diverge. Classical magmatism, with its secular scheme of sedimentation, limits the amount of sediment produced in geologic time so severely that it cannot even account for the observed mass of Phanerozoic sediments, let alone the Precambrian ones. According to it, the volume of these latter (whose existence we cannot doubt) must be minuscule. Whatever mobile elements in seawater (for example, boron) are concentrated in insoluble sedimentary minerals ought to be much more abundant in the scarce Precambrian sediments than in the much larger mass of Phanerozoic ones.
The persedimentary model, on the other hand, imposes no such restrictions. The sediments are recycled again and again; there is no reason to suppose that the Precambrian ones, when laid down, were any less abundant that those of today, or that the concentration of boron in them should be any different. The persedimentary prediction, not too easily verified in 1956, was later thoroughly vindicated by R. C. Reynolds. Jr. (1965), who measured the boron content of thirty-one Precambrian marine illites ranging in age from 1.0 to 1.7 billion years. Twenty-three of the measurements lay inside the 95 percent confidence limits for seventy samples from Phanerozoic rocks. Classical magmatism was unable to account for (1) the distribution of sodium among igneous rocks, sediments, and the ocean; (2) the sodium added in metamorphism of sediments to paragneiss; (3) the observed proportion of lime-stone in the Phanerozoic sedimentary reservoir; and (4) the observed age distribution in sediments of some mobile minor elements, among them boron.
The basalt-amphibolite-marl problem still had to be confronted. Nieuwenkamp dealt with it in “Oceanic and Continental Basalts in the Geochemical Cycle” (1968). This paper begins with a thorough examination of the terms juvenile and resurgent in which almost no possibility is left unexplored, no stone (one might also say) unturned. The looming bulk of the earth’s mantle is considered as though possibly by some stretch it could be called resurgent in an emergency. (Meteorites on arrival are definitely not resurgent; but they become surface rocks at the moment of impact, might even be weathered before becoming part of the growing mantle. Then, if they should ever come to the surface again, they would technically qualify as resurgent.)
The importance of magma has been further attenuated by seismology, which has looked in vain for great reservoirs of it under the crust; whatever comes up must once have been solid rock and then melted for the occasion. With so limited a supply on hand, making large amounts of granite by differentiation would be more difficult than getting it by melting sediments. Winkler’s famous experiments in Bonn (1958–1961) have shown that this can be done. In this paper Nieuwenkamp displays the continuous rock series in its definitive, three-dimensional form (Figure 1, p. 679), with both the rocks themselves and the pathways by which they cycle around. Everything is resurgent; nothing is juvenile.
Making granite from shale poses no “space problem”; the transformation can be isovolumetric (more or less). In fact, it solves the problem posed by large granite bodies in former times; if they are intrusive, how did they find room? The case of marl and basalt is quite different: “Derivation of all basalts from marly sediments can hardly be seriously entertained because of the disproportion between the enormous volumes of basalt and the scarce occurrences of metamorphic limestones” (1968, p. 369). Nieuwenkamp proposes the following solution: juvenile basic magma formed a primeval crust of lava that was weathered wherever it rose above the sea.
silicates + CO2 = quartz + carbonates
(Clays, of course, would be formed as well.) The quartz (solid) accumulated on the spot and was reincorporated in the crust there, making it gradually more siliceous and lighter, so that it came to ride high on the mantle as emergent granitic masses. The carbonate (dissolved) went to the ocean, accompanied by calcium, magnesium, iron, and perhaps some clay, where it was precipitated with them on the floor. Lava that remained submerged was not weathered but formed a basaltic crust to which was added the sedimentary material derived from the emergent (protocontinental) crust. Subduction under continental margins converted these sediments to amphibolite (with release of volatiles and excess calcium), and eventually to basalt that was plated onto the subducted oceanic basement. Each realm, continental and oceanic, developed its own metabolism, the one granitic and the other basaltic, separate but interacting. Some basalt erupted onto the continents, which in turn supplied sediment of like composition to the ocean floor. (Material exchange in subduction zones does not seem to have been envisaged).
In this scheme, the disproportion between basalt and “metamorphic limestone” was no longer cause for worry. The six-kilometer oceanic crust must have been subducted and recycled several times in four billion years, enough to have incorporated a considerable thickness of deep-sea sediment, and so “tuned” the convergence of ortho-and paraamphibolite. Nieuwenkamp points out some snags, among which he mentions the high potassium content of granitic rocks that “can hardly be derived from basic volcanics”. This does not seem too great a difficulty, granted the affinity of potassium for clay, which presumably would remain largely in the continental domain. More serious, perhaps, would be
the disproportion not between basalt and “metamorphic limestone” but between the latter and the earth’ mantle (especially as the proportion of lime in deep-sea sediments may have been quite low until Mesozoic times).
It was not very well known, in 1968, what became of the slabs of oceanic crust that were subducted under the leading edges of drifting plates. Nieuwenkamp supposed that the continents perhaps rode over them in the fashion of an icebreaker, but was not sure; “Leaving aside detailed guesses, the general conclusion seems unavoidable that parts of the basaltic ocean floor disappear downwards at or somewhere before the prow, and are reconstituted in the wake of a drifting continent”. If this were anything like the case, one could imagine the ocean floor, perhaps, as an entity somehow confined to the uppermost zone of the earth and effectively sealed off from the mantle beneath. From later work, however, it became apparent that subducted tectonic plates descended into the mantle or sank even deeper, perhaps to equilibrate with the mantle as a whole. In that case the influence of the sediment they carried with them must, even over four billion years, be negligible. “Once on [that] road, there’s no stopping.”
The persedimentary hypothesis had no alternative but to dive bravely into the mantle, that vast source of almost undeniably juvenile magma. If the mantle were well mixed, there would be faint hope of its ever coming back. Against the odds, it did. B. L. Weaver, D. A. Wood, J. Tarney, and J. L. Joron, after analyzing basaltic lavas from the South Atlantic, wrote in 1986: “The trace-element of Pb isotopic geochemistry of these lavas is explicable by contamination of the ocean-island basalt source that gave rise to Ascension, Bouvet and St. Helena lavas by variable, but small (about 1 percent) amounts of ancient (1.5–2.0 Ga) pelagic sediment”. Thus the influence of sediments was seen to extend even into the mantle, which was not well mixed enough to eradicate it.
The persedimentary hypothesis, developed before geophysics and geochemistry had revealed the detailed workings of subduction zones, could not foresee the full extent of interplay between the continental and oceanic regimes. It regarded the more silicic igneous rocks (granite-diorite and the volcanic equivalents) as little more than melted sediments. For a few of these rocks (such as dacites on St. Lucia, Windward Islands), this view seems valid; but the majority appear to have originated from remelted oceanic crust with or without an admixture of sediment. Thus some granitic magmas do seem to have risen from the depths, bringing with them heat to granitize sediments. And if they bring back, too, the conundrum of compositional convergence in rocks of different provenance, perhaps at the same time they bridge a gap between the continental and oceanic metabolisms that would otherwise make it difficult to understand the continuity between granite and gabbro.
Nieuwenkamp set out by inquiring in 1948 whether anything more definite could be postulated than merely that every rock or lava once had been a sediment. This postulate itself was an extreme one antithetical to that of classical magmatism, and chosen for that reason. It was the starting position, not the goal. Time (and improved analytical techniques) ultimately showed the pervasive influence of sediments in the earth’s metabolism, and at least vindicated the statement that every “rock or lava” appearing at the surface is likely to have had some prior experience, however dim or tenuous, of the exogenic environment. But the answer that influenced the course of geochemistry was the same Hutton had given in 1785 and James Croll had given again in 1871; the sediments are recycled again and again, and their mass remains more or less the same (“Géochimie classique et transformiste”, 1956). This time something was perceived that had been missed on the two previous occasions. A few people were becoming interested in modeling geologic processes mathematically; but although many small-scale processes were understood well enough to be modeled successfully, there was no satisfactory physical basis for modeling global phenomena such as the “rock cycle” (a mere textbook platitude) or the chemistry of the ocean.
The idea in “Geochemistry of Sodium” (1948) of an essentially steady-state ocean with cyclic fluxes was taken up by Harald Carstens (a student of Barth) in 1949. He translated it mathematically into a steady-state reservoir with constant input and an output regulated by first-order, feed-forward control, and showed that the steady state would have been attained (more or less) within the first few hundred million years of the ocean’s existence, so far as sodium was concerned. Barth later worked out residence times for several other elements; all were short compared with the lifetime of the ocean. Carstens’ model became the archetype of countless others that were applied in the succeeding decades, with varying degrees of complexity, to all sorts of geologic systems ranging from the continental crust to the global climate. The era of geochemical cycles had begun, preparing the way for a true synthesis in the 1980’s (Veizer and Jansen, 1985) of cyclic and secular influences in the history of the earth.
Nieuwenkamp left no voluminous literature behind him, nor did his soft, conversational voice carry far in the great lecture halls of Europe’s scientific societies. He never visited the United States. His considerable influence was felt instead at small colloquiums, at roadside stops by his favorite outcrops, in quiet bars and restaurants, in his comfortable and elegant room at the old geological institute on the Oude Gracht in Utrecht, and, by a lucky few, at his house in Bilthoven, where he and his wife, Sienie (Essienie Nannenga, also a geologist), and their three children kept a table justly reputed for its cuisine, wines, and conversation. His ideas were spread by his friends, most of all Barth, who restated and augmented them in his well-known textbook (Theoretical Petrology, 2nd. ed., 1962) and in a number of papers written in the early 1960’s. One of these (Barth, 1961) has practically the same title as one of Nieuwenkamp’s (“Korrelation von Sediment und Eruptivgesteine,” 1956).
It has been mainly through the assimilation of his ideas into the writings of Barth and others (with all of whom he was on the most cordial terms) that Nieuwenkamp’s cyclic views of geochemistry and petrology have achieved the wide (but still largely anonymous) currency that they enjoy today. Recognition came in the United States in 1972 with the founding of the Work Group on Geochemical Cycles (incorporated into the Geochemical Society in 1983), which has held a series of symposia attended by leading North American geochemists as well as by distinguished visitors from other continents. In 1980 the National Science Foundation sponsored a five-day conference with the theme “Chemical Cycles in the Evolution of the Earth,” the proceedings of which (Gregor et al., 1988) were published in a volume commemorating Nieuwenkamp’s contributions to geochemistry. Nieuwenkamp’s lifetime interest in the origins of geology led him to participate in the founding of the International Committee for the History of the Geological Sciences at the inaugural convocation at Yerevan, Armenia, in 1967; he remained active in this committee until his death.
In the last decade of his life, Nieuwenkamp turned his attention to scientific biography, writing articles on M. van Marum and (for the Dictionary of Scientific Biogarphy) C. L. von Buch, C. R. T. Krayenhoff, and F. A. Vening Meinesz. But his interest in the cycles never flagged, and at the time of his death he had begun a manuscript entitled (with characteristic modesty) “The New Petrology of Tom F. W. Barth.” Nieuwenkamp’s extraordinary erudition allowed him to view a subject from many vantage points, and a wide command of languages (both modern and classical) gave him access to a range of literature beyond the reach of most of his contemporaries. His underlying attitude was one of benign skepticism, and nothing amused him more than to discover in some dogma of the day an inconspicuous but pregnant inconsistency.
On his retirement from the chair of geochemistry, his colleagues at Utrecht gave Nieuwenkamp a beer mug engraved with the motto “Who sows doubt shall reap insight” (“Wie twijfel zaait zal inzicht oogsten”). Always urbane and good-natured, he made many friends among scientific supporters and opponents alike. His wit was mordant but never cruel. He was a delightful companion, and traveling with him was a continual series of digressions rewarded by unusual discoveries, arresting views, unexpected meetings, and memorable meals. He had little patience with stupidity, but was never unkind to simple ignorance. His towering intellect was half hidden by an irrepressible sense of fun that made him approachable. On hearing that a student using pyknometers thought they must have something to do with pigs, he got a glassblower to make some shaped like pigs and surreptitiously substituted them for the real ones. Unfailingly courteous, he would meet visitors at the little railway station in Bilthoven and walk or drive with them the half mile or so to his house in the Tenkatelaan. He continued this practice even after his health began to fail in 1978, and one would step from the train to see his slight, stooped figure stand tall for a moment with pleasure at the prospect of an approaching guest.
I. Original Works. A comprehensive bibliography of Nieuwenkamp’s articles is in R. D. Schuiling, “In Memoriam W. Nieuwenkamp (1903–1979),” in Geologie en mijnbouw, 59 (1980), 183–186. Among them are “Geochemistry of Sodium,” in Report of the International Geological Congress, 18th Session, II (London, 1948), 96–100; “Géochimie classique et transformiste,” in Bulletin de la Société géologique de France, 6th ser., 6 (1956), 407–429; “Korrelation von Sediment und Eruptivgesteine,” in Gedenkboek H. A. Brouwer, Verhandelingen van het K. nederlandsch geologisch-mijnbouwkundig genootschap, 16 (1956), 309–316; and “Oceanic and Continental Basalts in the Geochemical Cycle,” in Geologische Rundschau, 57 (1968), 362–372.
II. Secondary Literature. T. F. W. Barth, “Ideas on the Interrelation Between lgneous and Sedimentary Rocks,” in Bulletin de la Commission géologique de Finlande, 196 (1961), 321–326, and Theoretical Petrology(New York, 1952; 2nd ed., 1962); H. Carstens, “Et nytt prinsipp ved Kvantitative geokimiske bereginger,” in Norsk geologisk tidskrift, 28 (1949), 47–50; F. W. Clarke, The Data of Geochemistry (Washington, D.C., 1908); J. Croll, “On a Method of Determining the Mean Thickness of the Sedimentary Rocks of the Globe,” in Geological Magazine, 8 (1871), 97–102, 285–287; V. M. Goldschmidt, “Grundlagen der quantitativen Geochemie,” in Fortschritte der Mineralogie, Kristallographie und Petrographie, 17 (1933), 112–156; C. B. Gregor, R. M. Garrels, F. T. Mackenzie, and J. B. Maynard, eds., Chemical Cycles in the Evolution of the Earth (New York, 1988); J. Hutton, Abstract of a Dissertation Read in the Royal Society of Edinburgh. . . Concerning the System of the Earth, Its Duration and Stability (Edinburgh, 1785); J. Poly, “An Estimate of the Geological Age of the Earth,” in Scientific Transactions of the Royal Dublin Society, 2nd ser., 7 (1899), 23–66; T. M. Reade, “Measurement of Geological Time,” in Geological Magazine, 3rd ser., 10 (1893), 97–100; R. C. Reynolds, Jr., “The Concentration of Boron in Precambrian Seas,” in Geochimica et Cosmochimica Acta, 29 (1965), 1–16; S. J. Shand, Eruptive Rocks (London, 1943); E. den Tex, “Willem Nieuwenkamp,” in Jaarboek van het K. Nederlandsch akademie van wetenschappen (1979); J. Veizer and S. L. Jansen, “Basement and Sedimentary Recycling—2: Time Dimension to Global Tectonics,” in Journal of Geology, 93 (1985), 625–643; Barry L. Weaver, David A. Wood, John Tarney, and Jean Louis Joron, “Role of Subducted Sediment in the Genesis of Ocean-Island Basalts: Geochemical Evidence from South Atlantic Ocean Islands,” in Geology, 14 91986), 275–278; H. G. F. Winkler, “La Genèse du granite et des migmatites par anatexie expérimentale,” in Revue de géographie physique et géologie dynamique, 3 (1960), 67–76; and H. G. F. Winkler and H. van Platen, “Experimentelle Gesteinsmetamorphose—II: Bildung von anatektischen granitischen Schmelzen bei der Metamorphose von NaCl-führenden kalkfreien Tonen,” in Geochimica et Cosmochimica Acta, 15 (1958), 91–112, “Experimentelle Gesteinsmetamorphose—III: Anatektische Ultrametamorphose kalkhaltiger Tone,” ibid., 18 (1960), 293–316, and “Experimentelle Gesteinsmetamorphose—IV: Bildung anatektischer Schmelzen aus metamorphisierten Grauwacken,” ibid., 24 (1961), 48–69.
Grateful acknowledgement is made to John Wiley & Sons for permission to use material from “W. Nieuwenkamp, a Biographical Note,” in C. B. Gregor, R. M. Garrels, F. T. Mackenzie, and J. B. Maynard, eds., Chemical Cycles in the Evolution of the Earth (New York, 1988).