Suchergebnisse

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record ; Data availability: The data presented in this manuscript are available as a supplementary data table and will also be deposited in the PANGAEA open access library. ; Data availability: The data presented in this manuscript are available as a supplementary data table and will also be deposited in the PANGAEA open access library. ; Climate projections for the North American Southwest (NASW) predict an increasing frequency and duration of droughts over the 21st century in response to human- induced warming, with potentially severe economic and social consequences. The geological record provides a way to contextualise this prediction because of the past occurrence of abrupt hemispheric warming events and sustained intervals of atmospheric carbon dioxide loading equivalent to those projected for AD 2100 (between ~500 and 900 ppmv). Yet, terrestrial climate archives are typically too short and incomplete to provide a full record of these events. In principle, drill cores from deep sea sediments in the eastern Pacific Ocean can be used to overcome this problem because they contain long records of continental dust and distal riverine- supplied sediments from North America. Yet our limited understanding of the provenance and transport pathways of these sediments impedes use of these marine archives for this purpose. Here we present radiogenic isotope data (Sr, Nd and Pb) from known NASW dust-producing hot spots – playa lakes in the Mojave Desert, Quaternary silts mantling the California Channel Islands and the terrigenous fraction from marine sediments of the eastern Pacific Ocean, supported by new maps of bedrock isotopic composition in the NASW. We use these and published data sets to infer the origin of playa lake silts in the Mojave Desert and the source of windblown sediments to the California Channel Islands and nearby ocean basins. Our results rule out a significant contribution from the distal tails of either the Pacific Asian dust plume or the North African dust plume to the Quaternary Channel Island silt mantles, corroborating the suggestion that they are aeolian in origin and sourced from the NASW on the Santa Ana winds. We identify the Outer California Borderland basins as an attractive proposition for studying past dust flux and palaeoaridity in the North American South West. ; University of Southampton ; European Union ; Royal Society

The increasing global consumption of seafood has led to increased trade among nations, accompanied by mislabeling and fraudulent practices that have rendered authentication crucial. The multi-isotope ratio analysis is considered as applicable tool for evaluating geographical authentications but requires information and experience to select target elements such as isotopes, through a distinction method based on differences in habitat and physiology due to origin. The present study examined recombination conditions of multi-elements that facilitated geographically distinct classifications of the clams to sort out appropriate elements. Briefly, linear discriminant analysis (LDA) analysis was performed according to several combinations of five stable isotopes (carbon (δ(13)C), nitrogen (δ(15)N), oxygen (δ(18)O), hydrogen (δD), and sulfur (δ(34)S)) and two radiogenic elements (strontium ((87)Sr/(86)Sr) and neodymium ((143)Nd/(144)Nd)), and the geographical classification results of the Manila clam Ruditapes philippinarum from Democratic People's Republic of Korea (DPR Korea), Korea and China were compared. In conclusion, linear discriminant analysis (LDA) with at least four elements (C, N, O, and S) including S revealed a remarkable cluster distribution of the clams. These findings expanded the application of systematic multi-elements analyses, including stable and radiogenic isotopes, to trace the origins of R. philippinarum collected from the Korea, China, and DPR Korea.

As a rule materials of small atomic weight (light and heavy water, graphite, and so on) are used as neutron moderators and reflectors. A new very heavy atomic weight moderator is proposed—radiogenic lead consisting mainly of isotope 208Pb. It is characterized by extremely low neutron radiative capture cross‐section (0.23 mbarn for thermal neutrons, i.e., less than that for graphite and deuterium) and highest albedo of thermal neutrons. It is evaluated that the use of radiogenic lead makes it possible to slow down the chain fission reaction on prompt neutrons in a fast reactor. This can increase safety of the fast reactors and reduce as well requirements pertaining to the fuel fabrication technology. Radiogenic lead with high 208Pb content as a liquid‐metal coolant of fast reactors helps to achieve a favorable (negative) reactivity coefficient on coolant temperature. It is noteworthy that radiogenic lead with high 208Pb content may be extracted from thorium (as well as thorium‐uranium) ores without isotope separation. This has been confirmed experimentally by the investigations performed at San Paulo University, Brazil.

Two men walking across a bridge along highway I‐75 found a young woman's body floating in the water below. This 1971 case has since become known as the "Little Miss Panasofkee" case. It is still an open homicide, for which neither the victim nor the perpetrator have been identified. Throughout the United States, thousands of similar cases remain open. The medicolegal communities work on these cases, as the years pass, applying new scientific methods and following new leads as they can be developed. As the years pass, the priorities of the investigations often shift. In any homicide investigation the goal is to solve the murder and bring the perpetrator to justice. While this is still true for long‐term open or cold cases, the needs of families to know the truth, find and bury remains, and find closure outside of criminal trials become increasingly important. In the case study presented here, we reanalyzed the biological profile of the decedent, created a new facial approximation and imaging for visualization of personal evidence, and analyzed samples of hair, bone, and enamel for Sr, Pb, C, N, and O isotopes to decipher a geographical place of origin for the decedent. Hair data show a shift from lighter to heavier C isotopic values indicating a diet change from more grain‐based (hair tip) to more corn‐based (hair root) diet. Oxygen isotopes in teeth show relatively heavy isotopic values suggesting southern geographical origin near a major water basin. Lead isotopic data for teeth and bone samples show relatively low‐radiogenic values suggesting that the victim was born and raised in Europe. There is shift to low 87Sr/86Sr from first to third molar and bone indicating possible migration and dietary change. Taken together, the radiogenic and stable isotope data indicate that the decedent was foreign born. The shift in the hair C isotopes suggests that the victim arrived in Florida/United States between 2 and 12 months before she was murdered. The Pb isotope data suggest European origin. Considering all of the chemical data, including Pb concentrations and Pb, Sr, O, and C isotope analyses on teeth, rib, and hair samples, we can suggest that the victim was most likely a foreigner from southeastern Europe, possibly Greece. The methods used here and the impact of these methods for developing new leads for investigators decades later are discussed and provide new avenues of investigation for other unsolved cases.

This research was financially supported by FEDER Funds and the following Spanish Projects: PID2019-105625RB-C21 and RTI2018099157AI00 granted by the Ministerio de Ciencia, Innovacion y Universidades to JAP and JMGJ, respectively. Additional funding was provided by the Ramon y Cajal Fellowship RYC-2015-17596 to JMGJ. This is also a contribution from the ARC National Key Centre for Geochemical Evolution and Metallogeny of Continents (www.gemoc.mq.edu.au) and the ARC Centre of Excellence for Core to Crust Fluid Systems (www.ccfs.mq.edu.au). TA was supported by the Centre of Advanced Mining and Metallurgy (CAMM; www.ltu.se/centres/o/camm). ; In this short communication, we present preliminary data on the Re-Os isotopic systematics of platinum-group minerals (PGM) recovered from different horizons in the Falcondo Ni-laterite in the Dominican Republic. The results show differences in the Os-isotope composition in different populations of PGM: (i) pre-lateritic PGM yield Os-187/Os-188 varying from 0.11973 & PLUSMN; 0.00134 to 0.12215 & PLUSMN; 0.00005 (2 sigma uncertainty) whereas (ii) lateritic PGM are more radiogenic in terms of Os-187/Os-188 (from 0.12390 & PLUSMN; 0.00001 to 0.12645 & PLUSMN; 0.00005; 2 sigma uncertainty). We suggest that these differences reflect the opening of the Re-Os system in individual grains of PGM during lateritic weathering. The implications of these results are twofold as they will help to (1) elucidate the small-scale mobility of noble metals in the supergene setting and therefore the possible formation of PGM at these very low temperatures, (2) better refine the Os-isotopic datasets of PGM that are currently being used for defining dynamic models of core-mantle separation, crustal generation, and fundamental plate-tectonic processes such as the opening of oceans. ; FEDER by the "Ministerio de Ciencia, Innovacion y Universidades" PID2019-105625RB-C21 RTI2018099157AI00 ; Spanish Government RYC-2015-17596 ; Centre of Advanced Mining and Metallurgy (CAMM)

En el valle de Ambato, Catamarca, entre los siglos VI y XI DC se sucedió un proceso de complejización y diferenciación social que llevó al surgimiento de una sociedad no igualitaria, caracterizada por el mantenimiento de desigualdades en lo económico y político, especialización artesanal e intensificación en la explotación de los recursos. En este contexto, los camélidos tuvieron un rol relevante desde distintos aspectos económicos, sociales e ideológicos, lo cual llevó al surgimiento de una serie de interrogantes relativos a su procedencia y esferas de circulación. Precisamente, en este trabajo nos proponemos profundizar el estudio sobre las modalidades de obtención y manejo de estos recursos, a través de una nueva vía de análisis como es la utilización de isótopos radiogénicos de estroncio. Los resultados obtenidos nos permitieron observar que la mayor parte de los especímenes analizados presentan valores que se encuentran dentro de los correspondientes a los valores de isótopos de estroncio disponibles biológicamente en el valle de Ambato, lo que nos permite plantear, en primer lugar, que la mayor parte de los camélidos domésticos recuperados en los sitios arqueológicos fueron criados localmente; y segundo, que los camélidos silvestres también procederían de sectores aledaños o próximos al valle. ; In the valley of Ambato, Catamarca, between the sixth to the eleventh centuries AD a process of social differentiation and complexity led to the emergence of an unequal society characterized by the maintenance of economic and political inequalities, craft specialization and intensification in the exploitation of resources. In this context, camelids played an important role, not only from an economic standpoint, but also from different social and ideological aspects. However, there are a number of questions concerning the origin of the different species of camelids and areas of movement thereof. In this paper, we examine the modalities for obtaining and managing these resources through the analysis of radiogenic isotopes of strontium in samples from Aguada-affiliated archaeological sites. These data show that most of the analyzed specimens have values that are within the corresponding values of biologically available strontium isotopes in the valley of Ambato, allowing us to propose, first, that the most of the domestic camelids recovered in archaeological sites were bred locally and second, that wild camelids also come from neighboring or nearby valley sectors. ; Fil: Dantas, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Antropología de Córdoba. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades. Instituto de Antropología de Córdoba; Argentina ; Fil: Knudson, Kelly Jo. Laboratory For Archaeological Chemistry; Estados Unidos

En el valle de Ambato, Catamarca, entre los siglos VI y XI DC se sucedió un proceso de complejización y diferenciación social que llevó al surgimiento de una sociedad no igualitaria, caracterizada por el mantenimiento de desigualdades en lo económico y político, especialización artesanal e intensificación en la explotación de los recursos. En este contexto, los camélidos tuvieron un rol relevante desde distintos aspectos económicos, sociales e ideológicos, lo cual llevó al surgimiento de una serie de interrogantes relativos a su procedencia y esferas de circulación. Precisamente, en este trabajo nos proponemos profundizar el estudio sobre las modalidades de obtención y manejo de estos recursos, a través de una nueva vía de análisis como es la utilización de isótopos radiogénicos de estroncio. Los resultados obtenidos nos permitieron observar que la mayor parte de los especímenes analizados presentan valores que se encuentran dentro de los correspondientes a los valores de isótopos de estroncio disponibles biológicamente en el valle de Ambato, lo que nos permite plantear, en primer lugar, que la mayor parte de los camélidos domésticos recuperados en los sitios arqueológicos fueron criados localmente; y segundo, que los camélidos silvestres también procederían de sectores aledaños o próximos al valle. ; In the valley of Ambato, Catamarca, between the sixth to the eleventh centuries AD a process of social differentiation and complexity led to the emergence of an unequal society characterized by the maintenance of economic and political inequalities, craft specialization and intensification in the exploitation of resources. In this context, camelids played an important role, not only from an economic standpoint, but also from different social and ideological aspects. However, there are a number of questions concerning the origin of the different species of camelids and areas of movement thereof. In this paper, we examine the modalities for obtaining and managing these resources through the analysis of radiogenic isotopes of strontium in samples from Aguada-affiliated archaeological sites. These data show that most of the analyzed specimens have values that are within the corresponding values of biologically available strontium isotopes in the valley of Ambato, allowing us to propose, first, that the most of the domestic camelids recovered in archaeological sites were bred locally and second, that wild camelids also come from neighboring or nearby valley sectors. ; Fil: Dantas, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Antropología de Córdoba. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades. Instituto de Antropología de Córdoba; Argentina ; Fil: Knudson, Kelly Jo. Laboratory For Archaeological Chemistry; Estados Unidos

En el valle de Ambato, Catamarca, entre los siglos VI y XI DC se sucedió un proceso de complejización y diferenciación social que llevó al surgimiento de una sociedad no igualitaria, caracterizada por el mantenimiento de desigualdades en lo económico y político, especialización artesanal e intensificación en la explotación de los recursos. En este contexto, los camélidos tuvieron un rol relevante desde distintos aspectos económicos, sociales e ideológicos, lo cual llevó al surgimiento de una serie de interrogantes relativos a su procedencia y esferas de circulación. Precisamente, en este trabajo nos proponemos profundizar el estudio sobre las modalidades de obtención y manejo de estos recursos, a través de una nueva vía de análisis como es la utilización de isótopos radiogénicos de estroncio. Los resultados obtenidos nos permitieron observar que la mayor parte de los especímenes analizados presentan valores que se encuentran dentro de los correspondientes a los valores de isótopos de estroncio disponibles biológicamente en el valle de Ambato, lo que nos permite plantear, en primer lugar, que la mayor parte de los camélidos domésticos recuperados en los sitios arqueológicos fueron criados localmente; y segundo, que los camélidos silvestres también procederían de sectores aledaños o próximos al valle. ; In the valley of Ambato, Catamarca, between the sixth to the eleventh centuries AD a process of social differentiation and complexity led to the emergence of an unequal society characterized by the maintenance of economic and political inequalities, craft specialization and intensification in the exploitation of resources. In this context, camelids played an important role, not only from an economic standpoint, but also from different social and ideological aspects. However, there are a number of questions concerning the origin of the different species of camelids and areas of movement thereof. In this paper, we examine the modalities for obtaining and managing these resources through the analysis of radiogenic isotopes of strontium in samples from Aguada-affiliated archaeological sites. These data show that most of the analyzed specimens have values that are within the corresponding values of biologically available strontium isotopes in the valley of Ambato, allowing us to propose, first, that the most of the domestic camelids recovered in archaeological sites were bred locally and second, that wild camelids also come from neighboring or nearby valley sectors. ; Fil: Dantas, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Universidad Nacional de Córdoba; Argentina. ; Fil: Knudson, Kelly J. Arizona State University; Estados Unidos.

Despite emphasis placed by transnational theorists on the uniqueness of contemporary connections to homeland, such theories are relevant to the expansion of the ancient Tiwanaku state into the Osmore Drainage of southern Peru. These archaeological connections to homeland were maintained in the broader context of Tiwanaku sociopolitical organization, understanding of which is advanced by recent approaches to inter-regional interaction emphasizing studies of heterogeneous identities in peripheral contexts. The present study employs radiogenic strontium isotope analysis and stable carbon and nitrogen isotope analysis of bone collagen from individuals buried at a Tiwanaku provincial center in comparison with published diet and mobility data to better understand how different communities engaged with their ethnic and broader political identities. Additionally, radiogenic strontium isotope analysis of architectural material from the same provincial center is used to determine its source location and to better understand how the construction of the provincial center's temple related to colonists' ethnic and/or broader sociopolitical identities. Overall, a lack of difference in diet and mobility practices between different colonial communities and the building material's origin in the Osmore Drainage supports more heterarchical notions of Tiwanaku colonial organization, as well as concepts of Tiwanaku as both a political entity and a deeply held cultural milieu. Moreover, the presence of an anomalous young woman suggests the possible exchange of marriage partners with coastal Huaracane-related populations, an intriguing mechanism for the poorly understood indirect procurement of marine resources by Tiwanaku colonists.

The Ab-Bagh clastic- and carbonate-hosted stratabound and stratiform Zn-Pb deposit in the Sanandaj-Sirjan zone, in the southeastern corner of the Malayer-Esfahan metallogenic belt of Iran, is typical of several sedimentary–exhalative (SEDEX) deposits in this metallogenic belt. The deposit is hosted in a late Jurassic-early Cretaceous sedimentary sequence. Based on position, there are two Zn-Pb-bearing stratigraphic ore horizons. Ore horizon 1 is hosted by late Jurassic-early Cretaceous black shale and siltstone. The wedge-shaped ore body is located close to a synsedimentary normal fault. Petrographic studies indicates that mineralization comprises three sulfide ore facies: stockwork, bedded and massive ore facies. Ore horizon 2 occurs in early Cretaceous carbonates and comprises a massive-replacement ore facies that is concordant with host rock layering; it is also underlain by a stockwork facies. Textures include framboidal, laminated, breccia, replacement, massive and vein-veinlet. Hypogene sulfide minerals are predominantly sphalerite, galena, pyrite and chalcopyrite. Calcite and quartz are major gangue minerals. Silicification and carbonatization are the main wallrock alteration styles; alteration intensity increases towards the feeder zone. Based on relationships between ore minerals and rock-forming minerals, sulfide mineralization in the Ab-Bagh deposit formed during two main stages: fine-grained sulfide bands (stage I) are intricately interlayered with organic matter-rich beds of black shale and siltstone. Sulfide bands exhibit classic sedimentary textures, such as laminations and bedding, indicative of a synsedimentary origin. Coarser-grained stage II base metal sulfides show breccia and vein-veinlet textures, and are considered to have formed by replacement during sub-seafloor fluid flow. Fluid inclusion microthermometry was carried out on calcite associated with sulfides of the stockwork ore facies. Homogenization temperatures are in the range of 180–301¿°C, and the average salinity is 17.93¿wt% NaCl eq. The size distribution of pyrite framboids of the bedded ore, geochemistry of host rock and presence of organic matter, collectively suggest anoxic to locally suboxic ambient conditions for the host basin. The d34S composition of pyrite, sphalerite, and galena ranges from -5.08 to +4.51‰. The highest d34S values are from massive and stockwork ore facies (+2.66 to¿+¿4.51‰) and the lowest from bedded ore (-5.08 to -4.72‰). In the bedded ore facies, the main sulfur source was bacterially reduced seawater sulfate. Whereas in massive and stockwork ore facies, thermochemically reduced seawater sulfate was the main source of sulfur. The 87Sr/86Sr ratios of calcite indicate that origin of ore forming fluids is Paleozoic radiogenic basement. Collectively, the isotopic, sedimentological, textural, mineralogical, fluid inclusion, and geochemical data for the Ab-Bagh deposit support a vent-proximal sub-seafloor replacement SEDEX ore deposit. ; This research was made possible by the help of the office of vice-chancellor for Research and Technology, Tarbiat Modares University (TMU) of Tehran. Strontium isotope analyses were sponsored by the National Natural Science Foundation of China (91855214, 41773043, 41320104004, 41773042), and conducted by Yu-cai Song at the Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China. Sulfur isotope analyses were funded by the Catalan Government project 2014-SGR-1661. Comments and suggestions from Prof. Hooshang Asadi Haroni and Prof. Jan Matthias Peter greatly improved the quality of the paper. ; Peer Reviewed ; Postprint (published version)

1 What are Lamprophyres? — History, Definitions, Classification -- 1.1 A brief history of lamprophyre research -- 1.2 Classification and nomenclature: the Lamprophyre Clan -- 1.3 In defence of the Lamprophyre Clan -- 1.4 Summary of criteria for identifying lamprophyres as a clan -- 1.5 Identification and nomenclature of closely related rock-types -- 1.6 Distinctions between some petrographically similar rock-types -- 1.7 Genetic connotations for lamprophyre names: are they reasonable? -- 1.8 A new definition of the term 'lamprophyre' -- 2 When and Where? — Global Distribution, Igneous Associations -- 2.1 A preliminary caveat: metamorphism and lamprophyres -- 2.2 A compilation of worldwide lamprophyre occurrences -- 2.3 Global distribution and abundance of lamprophyres -- 2.4 Tectono-magmatic associations -- 2.5 Repeated lamprophyre injection in one area over geological time -- 3 Field Geology and Petrography — Macroscopy and Microscopy -- 3.1 Field geology of lamprophyres: diagnostic forms of occurrence -- 3.2 Petrographical (thin section) characteristics of lamprophyres -- 4 Cognate Mineralogy -- 4.1 Mineralogical features diagnostic of the whole lamprophyre clan -- 4.2 Minerals and parageneses diagnostic of each lamprophyre branch -- 4.3 Olivines -- 4.4 Monticellites -- 4.5 Garnets -- 4.6 Clinopyroxenes -- 4.7 Amphiboles -- 4.8 Biotite-phlogopites -- 4.9 Feldspars -- 4.10 Feldspathoids -- 4.11 Melilites -- 4.12 Carbonates -- 4.13 Spinels -- 4.14 Ilmenites -- 4.15 Perovskites -- 4.16 Other oxides and sulphides -- 4.17 Miscellaneous primary minerals -- 4.18 Secondary minerals -- 4.19 Glass -- 5 Whole-rock Geochemistry -- 5.1 Major and minor oxides -- 5.2 CIPW normative composition -- 5.3 Trace elements -- 5.4 Rare-earth elements (REE) -- 5.5 Precious metals (PGE, Au) -- 5.6 Radiogenic isotopes -- 5.7 Stable isotopes -- 6 Inclusion Suites — Macrocrysts, Xenocrysts, Xenoliths, etc -- 6.1 Type B (largely cognate): inclusions derived from host melt at high-P -- 6.2 Type C (semi-cognate): inclusions derived from evolved melt -- 6.3 Type D (partly cognate): inclusions derived for related melts -- 6.4 Type E (related or foreign): mantle-type mafic-ultramafic inclusions -- 6.5 Type F: True xenocrysts and xenoliths of unrelated crustal rocks -- 6.6 The discrete nodule (macrocryst, megacryst) suite -- 6.7 Abundance of different inclusion types in different lamprophyres -- 6.8 P-T significance of inclusion suites -- 7 Plutonic and Volcanic Equivalents of Lamprophyres -- 7.1 Plutonic and volcanic equivalents of calc-alkaline lamprophyres -- 7.2 Plutonic and volcanic equivalents of alkaline lamprophyres -- 7.3 Plutonic and volcanic equivalents of ultramafic lamprophyres -- 8 Nature, Origin and Evolution of Lamprophyre Melts -- 8.1 Do 'lamprophyre magmas' exist? -- 8.2 How many distinct lamprophyre magma-types are there? -- 8.3 What parameters can we use to deduce lamprophyres' origins? -- 8.4 Petrogenesis of individual lamprophyre magma-types -- 8.5 Evolution (differentiation) of lamprophyre melts -- 8.6 Lamprophyres as parental melts to other igneous rock-suites -- 8.7 Petrogenetic overview -- 9 Economic Geology -- 9.1 Lamprophyres and diamond -- 9.2 Calc-alkaline lamprophyres and gold -- 9.3 Lamprophyres and miscellaneous mineral deposits -- 10 A Selective Lamprophyre Bibliography -- Appendix A Abbreviations and Symbols -- Appendix B Glossary of lamprophyres and ambiguous petrological terms -- Appendix C Global Compilation of Lamprophyre Occurrences -- Table C1 Confirmed occurrences of calc-alkaline lamprophyres -- Table C2 Confirmed occurrences of alkaline lamprophyres -- Table C3 Confirmed occurrences of ultramafic lamprophyres -- Table C4 Confirmed occurrences of lamproites -- Table C5 Additional documentation for the appinite suite and vaugnérite series -- Table C6 Confirmed mixed or transitional occurrences (covering two or more branches) -- Table C7 Unconfirmed occurrences of "lamprophyres" -- Table C8 Apocryphal occurrences of "lamprophyres" -- Appendix D The computerized lamprophyre database LAMPDA.

[EN] New chemical and Sr–Nd–Pb isotopic data of the Plio-Quaternary mafic lavas of Gran Canaria are used to investigate their mantle source composition. The most prominent aspects of the new dataset are the slight isotopic differences between the Plio-Quaternary (Post-Roque Nublo Group) and the older Pliocene (Roque Nublo Group) mafic parental magmas, which reflect small-scale mantle heterogeneities. Melting of two mantle materials, one isotopically more depleted and similar to the Depleted Mantle (DM) and the other with more radiogenic Pb-isotope ratios comparable to a mantle with high U/Pb ratio (HIMU), accounts for the isotopic and trace element composition of the Pliocene–Quaternary magmas of Gran Canaria. Geochemical variations show that the Pliocene–Quaternary mantle source is compositionally and lithologically heterogeneous and supports the presence of a silica-deficient pyroxenite mantle component. The contribution of the pyroxenite component in the generation of the Roque Nublo and Post-Roque Nublo magmas is estimated to be in the range from 50 to 70%. Trace element ratios support mixing between the two mantle components (pyroxenite veins in a peridotite matrix) which obscure the original chemical and isotopic composition of these two end-members. ; This research was funded by the Spanish Ministry of Education and Science through projects CGL2004-04039BTE and PB96-0243. ; This research was funded by project PI2002/148 from the Canarian Government. ; It was carried out in the framework of the Consolidated Research Group PEGEFA (Refs. SGR-2005-795 and SGR-2009-972), funded by AGAUR-DURSI, Catalan Government. ; It was carried out in the framework of the Consolidated Research Group GEOVOL Research Group, Universidad de Las Palmas de Gran Canaria (Spain). ; Peer reviewed

In the 1970s, the Pena Blanca region (~50 km north of Chihuahua City, Mexico) was a target of uranium exploration and mining by the Mexican government. Since that time the Nopal I uranium deposit, located in unsaturated volcanic tuff, has been studied extensively because it is a good analogue for evaluating the fate of spent fuel, associated actinides, and fission products at a Yucca Mountainrepository. Water samples were collected from various locations (aditseepage, perched water, water supply well) near the Nopal I uranium deposit. 234U/238U ratios were higher in samples collected previously during relatively wet (summer) conditions (Pickett and Murphy 1999) than those of our data collected over the last two years from the same locations during dry (winter) conditions. Wet season samples have uranium concentrations <6 ppb and 234U/238U ratios of 76'10-6 to 278'10-6 (Pickett and Murphy 1999). Dry season samples show uranium concentrations of <68 ppb and 234U/238U ratios of 50'10-6 to 156'10-6. Two processes could be responsible for the seasonal variations in uranium isotopic composition at the site: 1) increased uranium dissolution and/or lower a-recoil-associated 234U enrichment rates in the vadose zone near the deposit during the dry season; and 2) increased evaporation under low-humidity conditions. Large variations in the 238U concentration and 234U/238U ratio were also found in samples collected from the saturated zone during the dry season. Observations such as these are important to performance assessments for evaluating the effects of climate on the long-term behavior of uranium in an oxidizing geologic environment. To correct analytical model results for the possible effect of evaporative concentration, chloride and stable isotope measurements made on water samples from the vadose zone are compared to those of rainwater. The U-series model results contribute toward understanding of the 3-D transport of uranium and radiogenic daughter products at Pena Blanca.