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The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts.sup.1. However, geochemical modelling and the occurrence of high .sup.3He/.sup.4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions.sup.2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle.sup.3,4, but key questions regarding the longevity of such sources on planetary timescales--and whether any survive today--remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth's deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history--to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts. Globally distributed kimberlites have their origins in a single, homogeneous early Earth reservoir that was subsequently perturbed, probably by subduction along the margins of Pangaea, around 200 million years ago., Author(s): Jon Woodhead [sup.1] , Janet Hergt [sup.1] , Andrea Giuliani [sup.1] [sup.2] [sup.5] , Roland Maas [sup.1] , David Phillips [sup.1] , D. Graham Pearson [sup.3] , Geoff Nowell [...]

Analysis of otolith strontium isotope ratios ([sup.87]Sr/[sup.86]Sr) is an increasingly utilized approach for studying fish migration. We analysed surface and ground water from the Daly River catchment in the wet-dry tropics of northern Australia over 2 years. Analyses of otolith [sup.87]Sr/[sup.86] Sr ratios were also conducted for freshwater sooty grunter (Hephaestus fuliginosus) and the putatively diadromous diamond mullet (Liza ordensis). Spatial variation in freshwater[sup.87]Sr/[sup.86] Sr was high (range: 0.71612-0.78059), and there was strong seasonality in water [sup.87]Sr/[sup.86]Sr, with highest values in the wet season. Temporal variation in water [sup.87]Sr/[sup.86]Sr ratios is attributed to seasonal patterns in surface runoff from geological formations with radiogenic compositions versus input from groundwater aquifers interacting with less radiogenic formations. Temporal variation in water [sup.87]Sr/[sup.86]Sr ratios precluded robust inference on movement within fresh water for both species, although movement across salinity gradients by diamond mullet was clearly identified. We conclude that temporally and spatially replicated water Sr data should be a general requisite for studies that analyse otolith Sr ([sup.87]Sr/[sup.86]Sr, Sr/Ca, Sr/Ba) to make inferences about fish movement and migration. L'analyse des rapports isotopiques [sup.87]Sr/[sup.86] Sr des otolithes est une approche de plus en plus utilisee pour etudier la migration des poissons. Nous avons analyse de l'eau souterraine et de surface dans le bassin versant de la riviere Daly dans la region tropicale humide/seche d'Australie meridionale sur une periode de 2 ans. Des analyses des rapports [sup.87]Sr/[sup.86]Sr d'otolithes ont egalement ete realisees pour Hephaestus fuliginosus, un poisson d'eau douce, et Liza ordensis, presume etre diadrome. L'eau douce presentait de fortes variations du [sup.87]Sr/[sup.86] Sr dans l'espace (fourchette : 0,71612-0,78059), et la saisonnalite du [sup.87] Sr/[sup.86] Sr de l'eau etait marquee, les valeurs les plus elevees caracterisant la saison humide. Les variations dans le temps des rapports [sup.87]Sr/[sup.86] Sr de l'eau sont attribuees a des motifs saisonniers des apports relatifs d'eau de ruissellement issue de formations geologiques radiogeniques et d'eau souterraine interagissant avec des formations moins radiogeniques. Les variations temporelles de[sup.87]Sr/[sup.86]Sr empechent toute inference robuste concernant les deplacements en eau douce pour les deux especes, bien que des deplacements de Liza ordensis le long de gradients de salinite aient ete clairement discernes. Nous en concluons que des donnees surle Srde l'eau reproduites dans le temps et dans l'espace devraient constituerun element necessaire des etudes du Sr ([sup.87]Sr/[sup.86] Sr, Sr/Ca, Sr/Ba) d'otolithes ayant pour but de faire des inferences sur les deplacements et la migration des poissons. [Traduit par la Redaction], Introduction Movement and migration by fishes is an important process in many riverine ecosystems, creating ecological connections between spatially distant habitats and functioning as a conduit for the transport of [...]

The contributions of nursery habitats to recruitment of non-native common carp (Cyprinus carpio) were estimated via analysis of water and otolith [sup.87]Sr/[sup.86]Sr and otolith trace element concentrations (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) over 3 years in the Lachlan River, Australia. Water samples and otoliths of postlarval carp were analyzed to characterize [sup.87]Sr/[sup.86]Sr and multielemental signatures of nursery habitats. Considerable temporal variation occurred in both water [sup.87]Sr/[sup.86]Sr and otolith multielemental signatures, which limited our ability to directly match water and otolith [sup.87]Sr/[sup.86]Sr in nurseries of the lower catchment. However, spatial variation in multi-elemental signatures was sufficient to allow accurate classification of nurseries within years. Assignment analysis of young-of-year fish suggested that several wetland and floodplain systems made significant contributions to young-of-year recruitment in the lower catchment. These contributions were strongly influenced by river flows and water management. Nurseries contributed fewer recruits to the main channel as distance from the nursery increased. Fish from the upper catchment originated from local sources, and there was no evidence of mixing of recruits between the upper and lower catchments. We conclude that identification of recruitment 'hotspots' via otolith chemical analysis can assist in developing strategies to control invasive fishes in large river networks. La contribution des habitats d'alevinage au recrutement de carpes communes (Cyprinus carpio) non indigenes a ete estimee par analyse du rapport [sup.87]Sr/[sup.86]Sr de l'eau et d'otolites et des concentrations d'elements en traces (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) d'otolites sur une periode de trois ans, dans la riviere Lachlan, en Australie. Des echantillons d'eau et des otolites de carpes post-larvaires ont ete analyses afin de caracteriser les signatures [sup.87]Sr/[sup.86]Sr et multi-elementaires d'habitats d'alevinage. Des variations temporelles considerables ont ete observees tant dans les rapports [sup.87]Sr/[sup.86]Sr de l'eau que dans les signatures multielementaires d'otolites, ce qui a limite la possibilite de relier directement les rapports [sup.87]Sr/[sup.86]Sr de l'eau et des otolites dans les habitats d'alevinage du bassin inferieur. Les variations spatiales des signatures multi-elementaires se sont toutefois averees suffisantes pour permettre une classification exacte des habitats d'alevinage pour des annees donnees. L'analyse d'affectation de jeunes de l'annee suggerait que plusieurs systemes de milieu humide-plaine inondable contribuaient de maniere significative au recrutement de jeunes de l'annee dans le bassin inferieur; ces contributions etaient fortement influencees par les debits de la riviere et la gestion l'eau. Plus la distance par rapport a l'habitat d'alevinage etait grande, moins l'apport au chenal principal de recrues provenant de ces habitats etait important. Les poissons issus du bassin superieur provenaient de sources locales, et rien n'indiquait la presence d'un melange de recrues issues des parties superieure et inferieure du bassin. Nous concluons que la delimitation de'points chauds'de recrutement grace a l'analyse chimique d'otolites peut appuyer l'elaboration de strategies de controle des poissons envahissants dans les grands reseaux fluviaux. [Traduit par la Redaction], Introduction The continuing spread of invasive fishes in rivers has severe impacts on aquatic ecosystems, and the human communities that rely upon them, in many regions of the world (Arthington [...]

Speleothems are well-proven archives of terrestrial climate variation, recording mean temperature, rainfall, and surface vegetation data at subannual to millennial resolution. They also form within the generally stable environment of caves, and thus may remain remarkably well preserved for many millions of years and, most important, can be dated radiometrically to provide robust chronologies that do not rely on orbital tuning, ice-flow modeling, or estimates of sediment deposition rates. The recent adaptation of the U-Pb dating technique to speleothems has greatly extended their potential as paleoclimate recorders back into the more distant geological past, well beyond the ~500 k.y. limit previously imposed by U-series techniques, but the opportunities presented by these new methods have yet to be fully explored. As an extreme example, here we report on samples recovered from Permian cave fills, the oldest radiometricaily dated speleothems SO far documented. Using state of the art analytical techniques it is possible to determine not only their age and state of preservation, but also to extract apparently nearly pristine climate proxy data. Armed with these methods, it now seems reasonable to apply the lessons learned from more recent speleothems to ancient materials, wherever they can be found, and of whatever age, to generate snapshots of paleoclimate that can be used to greatly refine the records preserved within the sediments and fossils of the time. doi: 10.1130/G30354.1

A severe drought in parts of low-latitude northeastern Africa and southwestern Asia ~4200 yr ago caused major disruption to ancient civilizations. Stable isotope, trace element, and organic fluorescence data from a calcite flowstone collected from the well-watered Alpi Apuane karst of central-western Italy indicate that the climatic event responsible for this drought was also recorded in mid-latitude Europe. Although the timing of this event coincides with an episode of increased ice-rafted debris to the subpolar North Atlantic, the regional ocean-atmosphere response seems atypical of similar Holocene icerafting events. Furthermore, comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longer-term climate anomaly. Keywords: speleothems, Holocene, drought, geochemistry, Italy.

The kimberlite rocks of the Udachnaya-East pipe (Siberia) are uniquely fresh and contain very high abundances of primary volatiles (Cl, C[O.sub.2], S). Alkali elements and chlorine are extremely abundant in the reconstructed kimberlite melt compositions, and this enrichment is very important for our understanding of deep-mantle melting and melt transport. Here we present new isotopic data that confirm a mantle origin for these kimberlitic chlorides and carbonates, and constrain the kimberlite emplacement age as ca. 347 Ma. The initial Nd and Pb isotope ratios in a large salt aggregate, in a CI-S-enriched water leachate of the groundmass, and in the silicate fraction of the groundmass are very similar ([[epsilon].sub.Nd] = +3 to +4, [sup.206]Pb/[sup.204]Pb = 18.6, [sup.207]Pb/[sup.204]Pb = 15.53), implying a comagmatic origin of the chlorides and carbonates and the silicates. Combined Sr, Nd, and Pb isotope data are used to rule out any significant contributions to the kimberlite chlorine budget from crustal sources, such as the Cambrian evaporite sequences of the Siberian platform. Our data support the interpretation that exsolved Na-K chloride and Na-K-Ca carbonate formed directly from original uncontaminated kimberlite magma. High Cl abundances in kimberlites suggest the presence of a Cl-rich reservoir in the deep sublithospheric mantle. Keywords: kimberlite, radiogenic isotopes, volatiles, chlorine, carbonate, mantle.

Kimberlite magmas, as the deepest probe into Earth's mantle (>150 km), can supply unique information about volatile components (hydrogen, carbon, chlorine, sulfur) in mantle-derived melts and fluids. All known kimberlite rocks are not suitable for studies of mantle volatiles because of their pervasive postmagmatic alteration; however, this study discusses an exceptionally fresh group I kimberiites ( Keywords: kimberlite, mantle volatiles, chlorine, carbonate, metasomatism, melt inclusions, immiscibility.

Dredged glass from the southern Mid-Atlantic Ridge near the Bouvet Triple Junction has unique major element, trace element, and isotopic composition, distinct from typical mid-ocean ridge basalts. It is a high-Mg (Mg# 67.8), high-Ni (NiO 290 ppm) andesite depleted in highly incompatible and heavy rare-earth elements with an isotopic signature of ancient continental lithosphere (i.e., low [sup.206]PB/[sup.204]PB and [sup.143]Nd/[sup.144]Nd and high [sup.87]Sr/[sup.86]Sr and [delta][sup.18]O). The origin of this glass is attributed to melting of a Precambrian garnet-bearing, mafic lithology, possibly related to lower crustal blocks stranded in the upper mantle during breakup of Gondwana and opening of the Atlantic. This composition can be used to explain anomalous geochemical features of oceanic rocks in the Southern Hemisphere Keywords: mid-ocean ridge basalts, isotopes, mantle heterogeneities, subcontinental lithosphere, South Atlantic, Gondwana.

Microsampling of cm-scale feldspar crystals within an S-type granite from the Lachlan Fold Belt of southeastern Australia has revealed complex internal Sr and Nd isotopic variations. The observed isotopic zonations are in part interpreted as recording feldspar crystallisation in a dynamically mixing magma system, the isotopic composition of which was varying in response to the influx of more mafic and isotopically more mantle-like magmas, the latter stages of which are now represented in modified form by microgranular enclaves. Similar core to rim isotopic variations in feldspar megacrysts from a microgranular enclave and the adjacent host granite strongly suggest megacrysts in the enclave were transferred from the granitic magma during crystallisation. Feldspar rims have higher [sup.87]Sr/[sup.86][Sr.sub.i] and lower [[epsilon].sub.Nd(i)] than adjacent whole rock analyses, .but match those of mineral separates from the surrounding enclave matrix. This suggests that the final stages of megacryst growth occurred in the presence of a component that had previously interacted with a high [sup.87]Sr/[sup.86]Sr, low [[epsilon].sub.Nd(i)] component such as metasedimentary wall rocks. Isotopic heterogeneities are also presererved within different mineral phases in the enclave matrix, suggesting that differing phases grew at differing stages of equilibration between the enclave magma and its host granitic magma. Our results reveal major isotopic heterogeneities on a single crystal and also inter-mineral scale in a pluton which shows well constrained evidence for magma mingling. These results indicate the suitability of feldspars as recorders of isotopic change in magmatic systems, even those which have cooled slowly in the plutonic environment and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale.

Two chemically related granitoid suites belonging to the mid Cretaceous were found at the Hohonu Batholith of North Westland, New Zealand. The two suites were produced during a period of rapid tectonic transition and can be distinguished through their Al2O3, Na2O, Sr, Ba, Eu and HREE contents. The differing contents is due to residual formations controlled by differing water contents during melting of a metabasaltic source.

Determining fluid flow patterns and sources is important to understanding crustal evolution. Stable isotope geochemistry is successfully used in fluid-rock interaction studies. The infiltration of water-rich fluids into marbles from Jervois, central Australia is described. Some marbles garnet grew when the deltasuper18O values of the host rock were changing, due to different fluid volumes needed to reset mineralogies and oxygen isotopes. Marbles outside the fluid-flow zones consisted of calcite + quartz + anorthite + diopside plus or minus phlogopite.

Re-Os isotope data show that the ore-forming komatiites occurring in the upper mantle of the late Archaean greenstone terrains of Western Australia have been uncontaminated by radiogenic crust before and during turbulent surface flow. The Os isotopic concentrations of sulphide ores and the komatiite failed to reach radiogenic levels, the Re/Os ratio was low. The concentration of both Re and Os was also low. The results of the study indicate that ground melting and assimilation of sulphidic sediments is unimportant for ore formation.

Epidote metasomatism affected large areas of tholeiitic metabasalts of the ~1,780 Ma Eastern Creek Volcanics in the Western Fold Belt of the Proterozoic Mount Isa inlier. Hydrothermal epidote generally occurs in quartz veins parallel to or boudinaged within the dominant [S.sub.2] fabrics which formed during the regional metamorphic peak at ~1,570 Ma associated with the Isan orogeny. Previously published stable isotopic and halogen data suggest that the fluids responsible for epidote formation are metamorphic in origin (with an evaporitic component). Application of the Pb stepwise leaching technique to the epidote does not separate radiogenic [Pb.sup.4+] and common [Pb.sup.2+], generating little spread in [sup.206]Pb/[sup.204]Pb (between 16.0 and 30.5). The causes for this relatively low range are twofold: There is little radiogenic Pb in the epidotes (the most radiogenic steps account for Keywords Epidote * Pb stepwise leaching * Mount Isa * Uranium * Copper * Mineralization * Age inheritance, Introduction Regionally extensive epidote-rich hydrothermal alteration assemblages in the Proterozoic Mount Isa Inlier formed during regional metamorphism ([D.sub.2] event) at ~1,575 Ma (Heinrich et al. 1995; Hand and Rubatto 2002; [...]

The timing of arrival of early hominids in Southeast Asia has major implications for models of hominid evolution. The majority of evidence for the earliest appearance of hominids in the region has previously come from Java in western Indonesia. Much of this evidence remains controversial owing to a poor understanding of the stratigraphic and chronologic relationships of the depositional units from which the material was derived. Before artifacts may be placed into their proper archaeological context, the geologic history of archaeological sites must be thoroughly understood, and deposits containing artifacts must be properly dated. An extensive investigation has been undertaken on the island of Flores, in eastern Indonesia, to determine the depositional and chronological history of stratigraphic units within the Soa basin; many of the units are associated with stone artifacts attributed to Homo erectus. Zircon fission-track dates of tuffaceous deposits within this lacustrine basin now provide the most reliable data concerning the true time of arrival of Homo erectus into Southeast Asia and indicate that these early hominids must have successfully begun colonizing eastern Indonesia by ca. 840 ka. Keywords: fission-track dating, Indonesia, Homo erectus, stratigraphy, basin analysis, geologic mapping.

The c. 2.06 Ga Bushveld Complex intrudes the Transvaal Supergroup, South Africa. Calcsilicate xenoliths within the mafic phase of the Bushveld Complex (Rustenburg Layered Suite, or RLS) preserve calcsilicate xenoliths with high-temperature (c. 1200 [degrees] C) mineralogies that were later metasomatized by hydrous, retrograde (c. 600-700 [degrees] C) fluids whose timing has been unconstrained. New U-Pb isotope data from newly grown titanite within a completely retrogressed xenolith indicates that retrogression occurred at 2058.9 [+ or -] 0.8 Ma. This suggests that retrogression was due to hydrothermal circulation associated with the cooling RLS, and not slightly later Bushveld-related granites. The new data place a tight constraint on the minimum age of emplacement of the RLS. Keywords: Bushveld Complex, U-Pb, absolute age, emplacement.