Robert Frei

Robert Frei
University of Copenhagen · Department of Geosciences and Natural Resource Management

Dr. Natw. ETH

About

426
Publications
117,911
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17,293
Citations
Additional affiliations
January 2008 - December 2011
University of Copenhagen
Position
  • Group Leader

Publications

Publications (426)
Article
Early Ediacaran cap dolostones are distinctive strata deposited directly above glaciogenic rocks from the Marinoan Glaciation (650–635 Ma), one of the most dramatic ice ages in Earth's history. These cap dolostones were rapidly deposited during global synchronous deglaciation, being a superb depositional window into the immediate glaciation afterma...
Article
The geotectonic setting for plumasite-type corundum occurrences is understudied, even though it is of importance for the understanding of trace-element patterns used for fingerprinting of ruby and sapphire. Mineral reactions related to metasomatism caused by pegmatite intrusion into ultramafic rock result in a characteristic trace element signature...
Article
In this study, we integrated extensive field, petrographic, whole-rock major and trace element, and Nd–Pb–Sr–O isotope, and zircon U–Pb ages, trace element and Lu–Hf isotope data from the Neoarchean Shawmere Anorthosite Complex and surrounding gneisses to unravel their petrogenetic origin and tectonic history. The ~2765 Ma Shawmere Anorthosite Comp...
Article
The geochemistry of Archean anorthosite-bearing layered intrusions has major implications for the thermal and chemical state of the Archean crust/mantle system, as originally posited by Bowen (1917) as “the anorthosite problem” and expanded on by Ashwal (1993). Debates have centred on the nature of the parental magmas, emplacement mechanisms and ge...
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Full-text available
The preservation of organic and human remains in Early Nordic Bronze Age mounds (1700 BCE -1100 BCE) permits new provenance work on this important period. Studies have shown that different mobility/non-mobility patterns were exercised by elite women during this time. To extend the database, we conducted strontium isotope analyses of the enamel from...
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Plumasite-type corundum occurrences in the Nattivit area in South-East Greenland offer a unique opportunity to study corundum formation in-situ where pegmatites intruded into metamorphosed lherzolite and dunite of the Archean-Paleoproterozoic continental crust. The Nattivit area, located in the Isertoq Terrane of North Atlantic Craton, forms part o...
Article
The Chapada Diamantina region in the São Francisco craton of eastern Brazil is composed of sedimentary successions containing both Mesoproterozoic and Neoproterozoic carbonate levels, making it a key natural laboratory for understanding the fluctuations of Earth’s biogeochemical cycles during its middle age. The ca. 1.4–1.2 Ga Caboclo Formation str...
Article
The Spanish region of Almería is well known for its rich geological records and its richness in archaeological remains. Sr isotopes have been applied in archaeology as a powerful tracing tool for individual human and animal mobility, but their application requires extensive regional baselines as reference against which the target materials can be c...
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Earth’s environment during the diversification of metazoans in the Late Ediacaran was characterised, amongst other factors, by changing oxygen levels and an extreme negative carbon isotope (δ¹³C) excursion, the Shuram Excursion. The Portfjeld Formation, North Greenland, deposited in the Franklinian Basin of eastern Laurentia, presents a unique oppo...
Article
Unique deposits that formed in the Precambrian oceans are the Banded Iron-Formations (BIFs) which are chemical sediments comprised of alternating layers of iron- and silica-dominated precipitates. The origin of this enigmatic banding is still debated, with most favoring a primary sedimentary and a few others arguing for a secondary diagenetic origi...
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Cadmium (Cd) isotope signatures (expressed as δ¹¹⁴Cd values) in seawater and in suitable modern and ancient sediments have been proposed as a useful tracer for paleobioproductivity and for constraining Cd as a micronutrient. This study contributes to the calibration of Cd isotope compositions in ancient shallow-water carbonates and proposes a combi...
Article
The Neoarchean Cross Lake-Pipestone Lake terrain, northwestern Superior Province, consists of the Cross Lake greenstone belt, the Pipestone Lake anorthosite complex, and multiple generations of granitoids. The Cross Lake greenstone belt includes an assemblage of basalt, picrite, gabbro, and sedimentary rocks (Pipestone Lake Group) that formed betwe...
Preprint
Unique deposits that formed in the Precambrian oceans are the Banded Iron-Formations (BIFs) which are chemical sediments comprised of alternating layers of iron- and silica-dominated precipitates. The origin of this enigmatic banding is still debated, with most favoring a primary sedimentary and a few others arguing for a secondary diagenetic origi...
Article
Full-text available
Early Cambrian black shales on the Yangtze Platform host a regionally distributed highly metalliferous sulfide-rich carbonaceous unit which has been the subject of extensive debate. This marker unit, with a few centimeters or tens of centimeters in thickness, displays extreme enrichment in Mo and Ni (wt% range), and in a broad spectrum of other met...
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In recent years, extensive archaeological studies have provided us with new knowledge on wool and woollen textile production at the Terramare site of Montale, in the Po plain, northern Italy. The large number of textile tools, and of zooarchaeological evidence suggesting intense sheepherding, hints at Montale being a specialized centre of wool prod...
Article
The evidence of prehistoric long-distance exchange networks in northern Italy is overwhelming, attested by several finds of non-local raw materials in Bronze Age pile-dwelling settlements of Lake Garda and eastern Po plain, like amber beads and bronze artefacts. Metals are dispersed throughout Bronze Age Europe from mining communities within the Al...
Article
Strontium (Sr) isotope based provenance and mobility studies of ancient humans and animals necessitate representative isoscapes/baselines. However, regions/terranes that were shaped and affected by glaciers during the last Ice Ages and are covered by glaciogenic sediments present a challenge with regards to the choice of suitable surface proxy arch...
Article
Soapstone was mined and traded by the Palaeo-and Neo-Eskimo cultures (Saqqaq, Dorset, and Thule) as well as the Norse and Moravian cultures living in Greenland through time. We collected soapstone from outcrops around Nuuk, which hold large quantities of Greenland's high-quality soapstone, and analysed their whole-rock geochemistry, Sm-Nd and Rb-Sr...
Article
Uranium isotopes (δ²³⁸U values) in ancient sedimentary rocks (shales, carbonate rocks) are widely used as a tool to reconstruct paleo-redox conditions, but the behaviour of U isotopes under modern non-sulfidic anoxic vs. oxic conditions remains poorly constrained. We present U concentration and isotope data for modern sediments from the Peruvian ma...
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87Sr/86Sr ratios have been frequently used for correlating marine sedimentary units and its fossils, especially where high fidelity reference curves exist. The latter are usually constructed from macrofossil calcite samples which have been screened for post-depositional alteration. Here, belemnite rostra from Lower Jurassic (Upper Sinemurian–Upper...
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We combine U-Pb in-situ carbonate dating, elemental and isotope constraints to calibrate the synergy of integrated mountain-basin evolution in western Gondwana. We show that deposition of the Bambuí Group coincides with closure of the Goiás-Pharusian (630-600 Ma) and Adamastor (585-530 Ma) oceans. Metazoans thrived for a brief moment of balanced re...
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The distribution of cadmium (Cd) within the oceans strongly suggests that it is used as a nutrient by marine phytoplankton. Biologically induced removal of Cd from modern surface waters is accompanied by an isotopic fractionation leaving surface-waters enriched in isotopically heavy Cd. This first study focusses on tying the Cd isotopic record pres...
Article
Widespread oceanic anoxia, biological crises, and volcanic activity are associated with the onset of Early Aptian (ca. 120 Ma) Oceanic Anoxic Event 1a (OAE1a). Reconstructions of oceanic deoxygenation and its links to broadly contemporaneous volcanism, however, remain poorly resolved. We use geochemical data, including δ53Cr ratios and rare Earth e...
Conference Paper
Full-text available
Cadmium (Cd) is an essential trace-micronutrient, and its distribution in modern ocean seawater columns is similar to major nutrients. Cadmium isotopes and cadmium concentrations [Cd] in seawater are useful proxies for reconstruction of ocean circulation, and for tracing the distribution of seawater nutrients from deep waters to surface waters. The...
Article
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While atmospheric oxygenation occurred largely in two major steps, the oxygenation of Earth's oceans is assumed to be more complicated, shifting repeatedly between oxic and anoxic conditions. The exact timeline and causal drivers of these changes, which seemingly culminated in the well‐ventilated oceans we see today are not well understood. This st...
Article
Sr isotopes are a powerful tool used to reconstruct human mobility in archaeology. This requires extensive bioavailable ⁸⁷Sr/⁸⁶Sr baselines used as reference for deciphering potential areas of origin. We define the first extensive bioavailable Sr isotope baselines for the different geographical regions and surface lithologies of Greece by combining...
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The Bronze Age of Sweden’s southernmost region, Scania, is complex and intriguing. One could say that Scania represented in many ways a gateway for people, ideas and material culture connecting continental Europe with Sweden. Shedding light on the dynamics of human mobility in this region requires an in depth understanding of the local archaeologic...
Article
Chromium isotope (δ⁵³Cr) values of marine sedimentary rocks are increasingly utilised for monitoring changes in redox conditions in the Earth's ancient oceans and atmosphere. Carbonate rocks are of particular interest as they are relatively common in the sedimentary record and have been shown under laboratory conditions to be capable of recording t...
Article
The mid-Proterozoic (1.8-0.8 Ga) may have witnessed persistent and predominant anoxia at the Earth's surface. However, recent studies suggest that there was a period around ~1.4 Ga where oxygen levels might have been transiently elevated, both in the atmosphere and oceans. In order to shed light on this debated topic, we analyzed rare earth element...
Article
The Ediacaran Santana dos Garrotes Formation Cachoeirinha Group of the Transversal Zone Domain (TZD) in the Borborema Province, NE Brazil, comprises a metaturbiditic sequence with carbonates, banded iron formations (BIF), and metavolcanic intercalations associated with a marine basin. Rare earth element patterns allow the identification of chemogen...
Article
Sr isotopes are a powerful tool used for provenancing in many disciplines, but their successful application requires the availability of robust Sr baselines of potential target areas. This study presents ⁸⁷Sr/⁸⁶Sr signatures and Sr concentrations of water, plants and soil leachates from the Peloponnese peninsula, Greece, to establish the first comp...
Article
The Piedras de Afilar Formation (PAFm) is a late Neoproterozoic sedimentary succession autochthonous to the Tandilia Terrane, part of the Río de la Plata Craton. It overlies with erosional unconformity a Paleoproterozoic igneous and metamorphic basement. According to facies analysis and lithostratigraphy, the PAFm is divided into three members for...
Article
Chromium isotopes have emerged as powerful redox proxies for past ocean-atmosphere systems as shifts in Cr isotope ratios towards heavier isotope compositions are indicative of Cr redox cycling on Earth. Knowledge of the Cr cycle in the critical zone and the fate of Cr during serpentinization and other hydrothermal processes is therefore important...
Article
The combination of authigenic chromium and cadmium stable isotopes in marine sedimentary archives enables reconstruction of the redox conditions and levels of primary productivity in past oceans and basins. The Ediacaran to Cambrian Nanhua Basin (Yangtze Platform, South China) and its sedimentary sequences have been studied intensively in the past...
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In east‐central Brazil, the Ediacaran‐Cambrian Bambuí Basin has the potential to provide a record of unique geochemical responses of Earth's ocean and atmosphere evolution during this key time interval. From this perspective, we studied an interval of the upper Bambuí Basin using sedimentologic, stratigraphic, and chemostratigraphic tools. The lowe...
Conference Paper
Full-text available
This study contributes to the calibration of novel stable metal isotope proxies (Cd and Cr), applied to modern and ancient sedimentary archives deposited in shallow-water carbonate platforms. Cadmium stable isotope ratios of 114 Cd/ 110 Cd (ε 114 Cd) are proposed to be a useful tracer for investigating paleo-productivity in marine settings, includi...
Article
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The Ediacaran period (635–541 Ma) was a time of major environmental change, accompanied by a transition from a microbial world to the animal world we know today. Multicellular, macroscopic organisms preserved as casts and molds in Ediacaran siliciclastic rocks are preserved worldwide and provide snapshots of early organismal, including animal, evol...
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RESUMEN. El objetivo de este trabajo es determinar las zonas favorables para la posible acumulación industrial de minerales del grupo del platino (PGM) en la región al oeste de Bahía Honda, Cuba. El área de estudio es rica en recursos minerales cobre, cinc, hierro, manganeso, cromo. Sin embargo, atendiendo a las características geológicas del área...
Article
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Changes in stable chromium isotopes (denoted as δ53Cr) in ancient carbonate sediments are increasingly used to reconstruct the oxygenation history in Earth’s atmosphere and oceans through time. As a significant proportion of marine carbonate older than the Cambrian is microbially-mediated, the utility of δ53Cr values in ancient carbonates hinges on...
Conference Paper
Full-text available
The Neoproterozoic witnessed several low latitude glaciations and geochemical and paleontological evidence hint at vast environmental changes that led to the evolution of multicellular life along with deep ocean oxygenation. Recent findings from trace element and novel stable isotope geochemistry argue for rather fluctuating than step-wise oxygenat...
Article
The Tapes Complex crops out in the southeastern Nico Pérez Terrane (NPT) of the Río de la Plata Craton and forms part of a NE-trending Mesoproterozoic belt together with the Calymmian (1.48–1.43 Ga) Parque UTE and Mina Verdún groups. The complex is characterized by interbedded/tectonically interleaved metasedimentary (mainly siliciclastic) and meta...
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The hydrological relationship between surface waters and groundwaters in many regions of the world is well known and the effects of their mutual interaction and interaction with the soils and bedrocks, with respect to resulting changes in their chemical composition, are well studied. In this study we add to this knowledge by comparing the distribut...
Article
The intrinsic link between atmospheric oxygenation, surface seawater redox and bioproductivity in the upper water column of oceans offers to combine cadmium with chromium isotopes in marine archives to deduce information on past controls of biological metal and nutrient cycling. We here use a novel approach in combining chromium and cadmium isotope...
Article
Strontium isotope research to answer questions regarding mobility and provenance of individuals from archaeological cemeteries has, until very recently, been focused almost entirely on bone and tooth samples from inhumation burials. This study investigates whether cremated tooth enamel, when present, can provide reliable strontium isotope ratios de...
Article
The Ediacaran-Cambrian transition was characterized by the evolution from Ediacaran soft-body to Cambrian skeletal organisms, and fluctuations of the marine carbon cycle. Marine redox changes should have played an essential role in both ecological and environmental evolutions; however, temporary changes and spatial distribution of redox conditions...
Article
The Neoarchean (2742.8 ± 0.8 Ma) megacrystic anorthosite-bearing Mayville layered intrusion of the Bird River greenstone belt, the Superior Province of Canada, is well preserved and well exposed. Given its good preservation, we studied the Mayville Intrusion through a combination of extensive field and petrographic observations, mineral chemistry,...
Article
A unique exposure of a strongly deformed late Mesoproterozoic augen-granite (U–Pb zircon age 1146 ± 4 Ma) was detected within rocks on the eastern rim of the West African Craton. These rocks, together with their sedimentary cover, were reworked during the Neoproterozoic Pan-African Dahomeyan orogeny, and are now incorporated in the Dahomeyan orogen...
Article
A provenance study on the Rocha Formation (Cuchilla Dionisio Terrane, Uruguay) based on elemental and isotope geochemistry and geochronology revealed characteristics typical of turbidites linked to orogenic arcs: textural and mineralogical immaturity, and low weathering and sedimentary recycling indicated by low CIA values, Th/U and Zr/Sc ratios. W...
Article
The groundwater contamination by hexavalent chromium (Cr(VI)) in a site of the Matanza-Riachuelo river basin (MRB), Argentina, has been evaluated by determining the processes that control the natural mobility and attenuation of Cr(VI) in the presence of high nitrate contents. The groundwater Cr(VI) concentrations ranged between 1.9E-5 mM and 0.04 m...
Article
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The application of Cr isotope compositions to the investigation of magmatic and post-magmatic effects on chromitites is unexplored. This study presents and compiles the first Cr stable isotope data (δ53Cr values) with major and trace element, contents from the Balkan Peninsula, aiming to provide an overview of the compositional variations of δ53Cr...
Article
Chromium (Cr) stable isotopes in marine sediments, in particular iron formations, have been used to track changes in Earth’s surface redox conditions. In recent years several studies have been published that focus on shale-hosted Cr isotopes to further constrain the evolution of atmospheric oxygen levels. As shales are composed of a mixture of detr...
Article
PURPOSE OF THE STUDY The results of the prospective study evaluating the outcomes of a combined therapeutic approach of non-operative therapy of Groin Pain Syndrome (GPS) in professional football players are presented. MATERIAL AND METHODS The evaluated cohort consisted of a total of 31 football players of a professional football club divided into...
Article
The Cr(VI) incorporation and chromium stable isotope composition in calcite has been studied in experiments performed in the pH range between 8.0 and 10.6 at constant temperature (T = 25 ± 1 °C), precipitation rate (rp = 10−7.7 ± 0.2 mol m⁻² s⁻¹) and total aqueous Cr(VI) concentration (Cr(VI) = 49.6 ± 1.3 mM). The obtained results indicate that Cr(...
Article
In this study, a strontium isotope baseline for Cyprus is presented. The aim of the study was two-fold; first to provide an environmental multi-proxy-based baseline (water/plants/soil leachates) suitable for archaeological provenance and mobility studies, food source authentication, and forensic investigations; and second, to contribute to the deba...
Article
Full-text available
An intensified debate centers on the use of strontium isotopes in surface water run-off as archive for bioavailable signatures in prehistoric provenance studies. Its use has been challenged by a recent suggestion that modern agricultural liming of farmlands exerts a serious imprint on the strontium isotope compositions of these waters. We here pres...
Article
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Earth’s atmosphere experienced a step of profound oxygenation during the Neoproterozoic era, accompanied by diversification of animals. However, during the Cryogenian period (720–635 million years ago) Earth experienced its most severe glaciations which likely impacted marine ecosystems and multicellular life in the oceans. In particular, large vol...
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Full-text available
Accurate estimates of the past extent of the Greenland ice sheet provide critical constraints for ice sheet models used to determine Greenland’s response to climate forcing and contribution to global sea level. Here we use a continuous ice core dust record from the Renland ice cap on the east coast of Greenland to constrain the timing of changes to...
Article
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We present results of the largest multidisciplinary human mobility investigation to date of skeletal remains from present-day Denmark encompassing the 3rd and 2nd millennia BC. Through a multi-analytical approach based on 88 individuals from 37 different archaeological localities in which we combine strontium isotope and radiocarbon analyses togeth...
Article
This study presents extensive new field, petrographic, and whole-rock major and trace element and Sm–Nd and Pb isotope data for the Neoarchean megacrystic anorthosite-bearing Bird River Sill, spatially associated Neoarchean supracrustal rocks of the Bird River greenstone belt, and the Mesoarchean Maskwa Lake TTG Batholith I, Manitoba, Canada. Field...