Coeval potassic and sodic calc-alkaline series in the post-collisional Hercynian Tanncherfi intrusive complex, northeastern Morocco: geochemical, isotopic and geochronological evidence   总被引：23，自引：0，他引：23  

Tamimount Ajaji  Dominique Weis  Andr Giret  Mohamed Bouabdellah 《Lithos》1998,45(1-4):371-393

The post-collisional late Hercynian Tanncherfi intrusive complex (TIC) is part of a widespread intrusive episode in the Moroccan Meseta. The complex contains a wide range of rock types, from monzogabbros to monzogranites. Two distinct magmatic series are recognized: (1) a potassic (shoshonitic) series consisting of monzogabbros, quartz monzonites and monzogranites; and (2) a sodic (granodioritic) series represented by quartz monzodiorites and granodiorites. All the Tanncherfi plutonic rocks display similar spider-diagram profiles, with LILE and LREE enrichment and Nb, Ta, Ti depletion, which are typical of subduction-related magmas. Combined major, trace element compositions and Sr, Nd isotopic results indicate that the two series have been derived from a LILE- and LREE-enriched continental lithospheric mantle source, under different partial melting and/or depth conditions. Intrusion of the Tanncherfi rocks was not temporally related to subduction and the enrichment of their source is likely to be linked to preceding subduction events. The two series evolved by fractional crystallization, of clinopyroxene, plagioclase, hornblende, biotite, K-feldspar and accessories (Fe–Ti oxide minerals, titanite, apatite and zircon) for the potassic series while the sodic series combined fractional crystallization with assimilation of felsic magmas with lower Sr isotopic ratio than the more mafic term of the series, the quartz monzodiorite. The intrusion of the potassic magmas (344±6 Ma) marks a major change in the tectonic regime of eastern Meseta. These magmas intruded during post-thickening uplift and extension, both probably favored by convective thinning of the lithosphere. This model provides a reasonable mechanism for the genesis of other Hercynian intrusive complexes in Morocco.  相似文献   

GGR Biennial Critical Review: Analytical Developments Since 2014          下载免费PDF全文

Kathryn L. Linge  L. Paul Bédard  Roxana Bugoi  Jacinta Enzweiler  Klaus Peter Jochum  Rüdiger Kilian  Jingao Liu  Johanna Marin‐Carbonne  Silke Merchel  Frans Munnik  Luiz F.G. Morales  Claire Rollion‐Bard  A. Kate Souders  Paul J. Sylvester  Ulrike Weis 《Geostandards and Geoanalytical Research》2017,41(4):493-562

This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC‐ICP‐MS and laser ablation‐ICP‐MS, as well as of radioactive isotope geochronology by LA‐ICP‐MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro‐XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF.  相似文献   

Geochemical constraints on the origin of the late Jurassic proto-Caribbean oceanic crust in Hispaniola     

J. Escuder Viruete  A. Pérez-Estaún  D. Weis 《International Journal of Earth Sciences》2009,98(2):407-425

The nature of the oceanic crust produced through rifting and oceanic spreading between North and South America during the Late Jurassic is a key element for the Caribbean plate tectonic model reconstruction. Located in the Cordillera Central of Hispaniola, the Loma La Monja volcano-plutonic assemblage (LMA) is composed of gabbros, dolerites, basalts, and oceanic sediments, as well as metamorphic equivalents, which represent a dismembered fragment of this proto-Caribbean oceanic crust. Petrologic and geochemical data show that the LMA have a relatively broad diversity in composition, which represent the crystallization products of a typical low-pressure tholeiitic fractionation of mid-ocean ridge basalts (MORB)-type parental magmas, ranging from N- to E-MORB. Three geochemical groups have been distinguished in the volcanic sequence: LREE-flat to slightly LREE-enriched basalts of groups II and III occur interlayered in the lower stratigraphic levels; and LREE-depleted basalts of group I in the upper levels. Mantle melt modeling suggests that group III magmas are consistent by mixing within a mantle melt column of low-degree (<1%) melts of a deep garnet lherzolite source and high-degree (>15%) melts of a shallow spinel source, and groups II and I magmas are explained with moderate to high (14–18%) and very high (>20%) fractional melting degrees of a shallower spinel mantle source, respectively. Thus, upward in the volcanic sequence of the LMA, the magmas represent progressively more extensive melting of shallower sources, in a plume-influenced spreading ridge of the proto-Caribbean oceanic crust. Nb/Y versus Zr/Y systematics combined with recent plate tectonic model reconstructions reveal that Caribbean Colombian oceanic plateau fragments in Hispaniola formed through melting of heterogeneous mantle source regions related with distinct plumes during at least from Aptian–Albian (>96 Ma) to Late Campanian.  相似文献   

A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108     

Wafa Abouchami  Stephen J. G. Galer  Tristan J. Horner  Mark Rehkämper  Frank Wombacher  Zichen Xue  Myriam Lambelet  Melanie Gault‐Ringold  Claudine H. Stirling  Maria Schönbächler  Alyssa E. Shiel  Dominique Weis  Philip F. Holdship 《Geostandards and Geoanalytical Research》2013,37(1):5-17

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio ¹¹⁴Cd/¹¹⁰Cd for NIST SRM 3108 lies within ～ 10 ppm Da^?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.  相似文献   

Geostandards and Geoanalytical Research Bibliographic Review 2012     

Klaus Peter Jochum  Uwe Nohl  Nadja Rothbarth  Beate Schwager  Brigitte Stoll  Ulrike Weis 《Geostandards and Geoanalytical Research》2013,37(4):469-473

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Beyond peasant deforestation: environment and development in rural Jamaica     

Tony Weis   《Global Environmental Change》2000,10(4)

Jamaica is experiencing one of the highest rates of deforestation in the world, with severe environmental consequences attendant to the loss of its forests. It is also plagued by high levels of poverty, particularly in rural areas. As throughout much of the tropics, impoverished peasant farmers are blamed as the primary agents in Jamaica's forest colonisation. Employing a case study in the Blue Mountains, this paper explores the discord that exists between forest conservation and the development priorities of poor farmers, arguing that this unsustainable dichotomy can only be understood by acknowledging the political economy which constrains peasant agriculture.  相似文献   

Vertical accretion rates and heavy metal chronologies in wetland sediments of the Tijuana Estuary   总被引：3，自引：0，他引：3  

Daniel A. Weis  John C. Callaway  Richard M. Gersberg 《Estuaries and Coasts》2001,24(6):840-850

This study represents the first report on sediment accretion rates using¹³⁷Cs dating for a southern California salt marsh. Vertical accretion rates ranged from 0.7 to 1.2 cm yr⁻¹, which is at the high end of sediment accretion values for coastal wetlands. This has lead to increases in elevation within the estuary from 18 to 35 cm over the last 35 years. Depth profiles of metal concentrations were converted to time-based profiles using vertical accretion rates. Chronologies for most cores indicate a consistent peak in sediment lead (Pb) concentrations in the early to mid 1980s, corresponding to the historic decline in Pb use, which was completed in the U.S. by the early 1980s, but not begun in Mexico until 1991. Sediment Pb levels ranged from about 6–56 μg g⁻¹. Other metals did not show any consistent trends in sediment chronology, except for a single core from a mid-marsh site (east-mid 2), which showed a 2–3-fold increase in levels of Cu, Ni, and Zn during the past two decades. Sediment levels of copper (Cu), nickel (Ni), and zinc (Zn) ranged from 6–34 μg g⁻¹, 11–27 μg g⁻¹, and 42–122 μg g⁻¹, respectively. Despite rapid industrial development of the watershed, a comparison of the sediment metal concentrations in the Tijuana Estuary to other anthropogenically-impacted estuaries in the United States and Europe, shows that metal levels in sediments of the north arm of the estuary are relatively low.  相似文献   

Hepatic histopathology in two populations of the mummichog,Fundulus heteroclitus     

Schmalz WF  Hernandez AD  Weis P 《Marine environmental research》2002,54(3-5):539-542

The pollution-tolerant mummichog, Fundulus heteroclitus, inhabits a heavily contaminated estuary, Piles Creek (PC), in Linden, NJ. PC contaminants include PAHs, PCBs and many metals, including high Hg and Pb. PC mummichog livers and kidneys were compared with those from a pristine estuary in Tuckerton (TK), NJ, by standard histopathological methods, with quantification by computerized image analysis. PC livers had > 2 x the lipid ratios of TK livers. Cell sizes and shapes were not different between populations. TK livers had a 25% incidence of basophilic areas and an age-related 30% incidence of macrophage aggregates; PC livers had none of these lesions. PC livers had a 100% incidence of necrotic foci, compared with 55% of TK livers. Inflammation was noted in 50% of TK livers but only 27% of PC livers. Curiously, the TK livers had a 45% incidence of metacercarial cysts of a digenetic trematode, while none were found in the PC livers. The TK focal necrosis and macrophage aggregates coincided with parasite infestation. There were no observed kidney lesions in either population. Positive biomarkers in this species thus included high hepatic lipid content, possibly necrosis, but no other lesions. The lack of trematode cysts in PC livers may reflect the lack of an intermediate host in this low biodiversity estuary.  相似文献   

A rapid change in methylmercury tolerance in a population of killifish,Fundulus heteroclitus,from a golf course pond     

Judith S. Weis  Peddrick Weis 《Marine environmental research》1984,13(3):231-245

Embryos of killifish (Fundulus heteroclitus) from Bullhead Bay, Southampton, New York, showed considerable variation in tolerance to methylmercury (meHg) in 1980, 1981 and 1983, in that some females produced eggs that were tolerant to the teratological effects of 0·05 ppm, while other females produced susceptible eggs. However, in 1982, over 40% of the females produced clutches of non-viable eggs (which could not be tested for meHg tolerance) and those fish which produced viable eggs generally produced tolerant ones. After hatching, the larvae were also more tolerant. Accompanying the shift in meHg tolerance was a trend of increasing fin ray count of the females, a parameter which has previously been correlated with the production of more tolerant embryos. In 1982, a nearby population exhibited a distribution of embryonic and larval tolerance and fin ray count comparable with that of the first population in the other years.We hypothesize that the unusually high rainfall in June, 1982 caused an inflow of pesticides and heavy metals from a golf course adjacent to the first site, and that the contaminants were responsible for the striking changes in reproductive success and meHg tolerance. Residues of chlorinated hydrocarbon insecticides were found in fish of the first, but not of the second, population. The variability in the original population may have permitted a segment of it to withstand the inflow of pollutants, while the susceptible individuals produced non-viable eggs. This may have been the cause of the rapid shift of overall tolerance in the population.  相似文献   

Evaluating prey capture by larval mummichogs (Fundulus heteroclitus) as a potential biomarker for contaminants     

Weis JS  Samson J  Zhou T  Skurnick J  Weis P 《Marine environmental research》2003,55(1):27-38

We evaluated larval prey capture as a "behavioral biomarker" of contamination by examining feeding behavior of larval mummichogs (Fundulus heteroclitus) from many different sites, including a severely contaminated "Superfund" site, moderately contaminated sites, and reference areas. Prey capture ability was related to sediment contaminant levels. The levels of contaminants at a site were highly correlated with each other, so that the impact of individual contaminants was confounded. The number of captures of brine shrimp by mummichog larvae from all sites was highly variable, but significant negative correlations of prey capture were seen with mercury, lead, zinc, cadmium, and PCBs. As observed previously with adults, polyaromatic hydrocarbons (PAHs) did not appear to impair prey capture ability. The only site in which prey capture rates of 8-day old larvae were severely affected was the most highly contaminated Superfund site, Berry's Creek, NJ. This implies that larval prey capture is not as sensitive a behavioral biomarker for contamination as adult behavior studied previously.  相似文献