Shoshonite and sub-alkaline magmas from an ultrapotassic volcano: Sr–Nd–Pb isotope data on the Roccamonfina volcanic rocks,Roman Magmatic Province,Southern Italy

The Roccamonfina volcano is characterised by two stages of volcanic activity that are separated by volcano-tectonic caldera collapses. Ultrapotassic leucite-bearing rocks are confined to the pre-caldera stage and display geochemical characteristics similar to those of other volcanoes in the Roman Province. After the major sector collapse of the volcano, occurred at ca. 400 ka, shoshonitic rocks erupted from cinder cones and domes both within the caldera and on the external flanks of the pre-caldera Roccamonfina volcano. On the basis of new trace element and Sr–Nd–Pb isotope data, we show that the Roccamonfina shoshonitic rocks are distinct from shoshonites of the Northern Roman Province, but are very similar to those of the Neapolitan volcanoes. The last phases of volcanic activity erupted sub-alkaline magmas as enclaves in trachytic domes, and as lavas within the Monte Santa Croce dome. Ultrapotassic rocks of the pre-caldera composite volcano are plagioclase-bearing leucitites characterised by high levels of incompatible trace elements with an orogenic signature having troughs at Ba, Ta, Nb, and Ti, and peaks at Cs, K, Th, U, and Pb. Initial values of ⁸⁷Sr/⁸⁶Sr range from 0.70926 to 0.70999, ¹⁴³Nd/¹⁴⁴Nd ranges from 0.51213 to 0.51217, while the lead isotope rations vary between 18.788–18.851 for ²⁰⁶Pb/²⁰⁴Pb, 15.685–15.701 for ²⁰⁷Pb/²⁰⁴Pb, and 39.048–39.076 for ²⁰⁸Pb/²⁰⁴Pb. Shoshonites show a similar pattern of trace element depletions and enrichments to the earlier ultrapotassic leucite-bearing rocks but have a larger degree of differentiation and lower concentrations of incompatible trace elements. On the other hand, shoshonitic rocks have Sr, Nd, and Pb isotopes consistently different than pre-caldera ultrapotassic leucite-bearing rocks. ⁸⁷Sr/⁸⁶Sr ranges from 0.70665 to 0.70745, ¹⁴³Nd/¹⁴⁴Nd ranges from 0.51234 to 0.51238, ²⁰⁶Pb/²⁰⁴Pb ranges from 18.924 to 19.153, ²⁰⁷Pb/²⁰⁴Pb ranges from 15.661 to 15.694, and ²⁰⁸Pb/²⁰⁴Pb ranges from 39.084 to 39.212. High-K calc-alkaline samples have intermediate isotopic values between ultrapotassic plagioclase leucitites and shoshonites, but the lowest levels of incompatible trace element contents. It is argued that ultrapotassic magmas were generated in a modified lithospheric mantle after crustal-derived metasomatism. Interaction between the metasomatic agent and lithospheric upper mantle produced a low-melting point metasomatised veined network. The partial melting of the veins alone produced pre-caldera leucite-bearing ultrapotassic magmas. It was possibly triggered by either post-collisional isotherms relaxation or increasing T°C due increasing heat flow through slab tears. Shoshonitic magmas were generated by further melting, at higher temperature, of the same metasomatic assemblage with addition 10–20% of OIB-like astenospheric mantle material. We suggest that addition of astenospheric upper mantle material from foreland mantle, flowing through slab tearing after collision was achieved. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Study of the post-flare loops on 29 July 1973

Bright and dark curvilinear structures observed between the two major chromospheric ribbons during the flare of 29 July 1973 on films from the Big Bear Solar Observatory are interpreted as a typical system of coronal loops joining the inner boundaries of the separating flare ribbons. These observations, made through a 0.25 Å H filter, only show small segments of the loops having Doppler shifts within approximately ± 22 km s^–1 relative to the filter passband centered at H, H -0.5 Å or H +0.5 Å. However, from our knowledge of the typical behavior of such loop systems observed at the limb in H and at 5303 Å, it has been possible to reconstruct an appoximate model of the probable development of the loops of the 29 July flare as they would have been viewed at the limb relative to the position of a prominence which began to erupt a few minutes before the start of the flare. It is seen that the loops ascended through the space previously occupied by the filament. On the assumption that H fine structures parallel the magnetic field, we can conclude that a dramatic reorientation of the direction of the magnetic field in the corona occurred early in the flare, subsequent to the start of the eruption of the filament and prior to the time that the H loops ascended through the space previously occupied by the filament.     

Analysis of patterns of vertical and temporal distribution of phytoplankton using multifactorial analysis: Acidic Lake Caviahue, Patagonia, Argentina

Most existing studies on the algal communities of acid lakes are based on environments that have been caused by anthropogenic disturbances. Such lakes have a different origin compared to the natural acidic lakes and could be expected to differ also in the mechanisms controlling phytoplankton and trophic status. Planktonic community in Lake Caviahue is somewhat diverse in spite of the low pH of the water. Algae have a distinctive vertical distribution: the values of phytoplankton biomass remain constant throughout the water column and at times were highest in the upper end of the hypolimnion, forming a maximum or a layer of chlorophyll a at depth. The goal of this work was to investigate the factors influencing the seasonal and vertical distribution of phytoplankton. The lake was sampled between the years 2004 and 2006. Physical, chemical and biological parameters at different depths throughout the water column were determined. The interrelationships between environmental variables at different sampling dates were analyzed using an integration of multivariate matrices, multiple factor analysis, to analyze any joint partnerships in the samples. We found that phytoplankton biomass is dominated by Keratococcus rhaphidioides. With regard to zooplankton, we found a single species of rotifers (Philodina sp.). The two arms of the lake and the depths have different behaviours showing differences in the arms' conductivity, dissolved oxygen and pH. The more superficial layers were characterized by high values of phytoplankton and zooplankton biomass, organic and inorganic carbon, dissolved oxygen and pH. The deeper layers showed high values of chlorophyll a, ammonium and phosphorus (dissolved and particulate). From the multivariate analysis the relationships of the each algal species with pH, as a possible indicator of the degree of “acidophilia”, could be extracted.     

GENDER,RACE, AND COMMUTING AMONG SERVICE SECTOR WORKERS*

The generality that women work closer to home and have shorter commuting times than men needs to be assessed for racial groups. Statistical analysis of commuting times for a large sample of service workers in the New York metropolitan area shows that black and hispanic women commute as far as their male counterparts and their commuting times far exceed those of white men and women. Workplace factors, such as income, occupation, and job accessibility, are important in explaining these findings.     

Petrogenesis of post-collisional A-type granitoids from the Urumieh–Dokhtar magmatic assemblage,Southwestern Kerman,Iran: Constraints on the Arabian–Eurasian continental collision

Three plutons (Deh-Siahan, Bande-Bagh and Baghe-Khoshk Sharghi, collectively referred to as the DBB hereafter) in southwestern Kerman, in the southeastern part of the Urumieh–Dokhtar magmatic assemblage (UDMA) of the Zagros orogenic belt differ from the typical calc-alkaline metaluminous, I-type intrusions of the region. The DBB intrusions have a distinct lithological assemblage varying from diorite through monzogranite and monzonite to alkali feldspar syenite and alkali granite. The DBB granitoids are metaluminous to slightly peraluminous, alkaline to shoshonitic in composition and have high total alkali contents with K₂O > Na₂O, high FeO_T/MgO values, and low CaO and MgO contents. They are enriched in some LILEs (such as Rb and Th) and HFSEs (such as Zr, Y and REEs except Eu) and depleted in Sr and Ba relative to primordial mantle, and have low concentrations of transitional metals. These features along with various geochemical discriminant diagrams suggest that the DBB granitoids are post-collisional A-type granitoids, which had not been recognized previously in the UDMA. The chondrite-normalized REE patterns of the DBB granitoids show slightly enriched light REEs [(La/Sm)_N = 2.26–4.13], negative Eu anomalies [(Eu/Eu*)_N = 0.19–0.74] and flat heavy REE patterns [(Gd/Yb)_N = 0.80–1.87]. The negative Eu anomaly indicates an important role for plagioclase and/or K-feldspar during fractional crystallization. Whole-rock Rb–Sr isotope analysis yields an isochron age of 33 ± 1 Ma with an initial ⁸⁷Sr/⁸⁶Sr value of 0.7049 ± 0.0001. Whole-rock Sm–Nd isotope analysis gives ε_Nd^t values from + 2.56 to + 3.62 at 33 Ma. The positive ε_Nd^t and low I_Sr values of the DBB granitoids together with their T_DM of 0.6–0.7 Ga suggest their formation from partial melting of a lithospheric mantle source, modified by fluids or melts from earlier subduction processes. Melting of lithospheric mantle occurred via a dehydration melting process at pressures below the garnet stability field, as a consequence of lithospheric mantle delamination or break-off of a subducted slab and melting of the lithospheric mantle by upwelling of hot asthenosphere. On the basis of Rb/Sr age dating and the post-collisional geochemical signatures of the DBB granitoids, along with extensive pre-collisional volcanic eruptions in Middle Eocene, we suggest Late Eocene for the time of collision between the Arabian and Central Iranian plates. This also implies that the calc-alkaline I-type intrusions in the southwestern Kerman and in other parts of the UDMA may have formed in a post-collisional context.     

新形势下林区的就业机会与渠道

我国实施“天然林保护工程”以来,林区人民积极转产分流,寻找新的就业门路和生计,为走出困境、改善生活做出了不懈的努力。为了进一步开阔视野,拓展思路,借鉴他国的经验,我们选刊了“国际森林趋势组织”的几篇关于寻找新的林区就业渠道和森林环境服务市场开发方面的研究文章,以期对我国的林业改革与建设有所启示。(注:这些文章已经“森林趋势组织”的执行主管Mivhael Jenkins先生同意译成中文在本刊刊登,本刊作了部分删节和改动。原文及参考文献请参阅森林趋势组织的网页:http://www. forest-trends. org)     

Hispanic Immigrants' Vulnerabilities to Flood and Hurricane Hazards in Two United States Metropolitan Areas

Research reveals that disasters are disproportionately debilitating for marginalized social groups. Numerous studies have examined racial/ethnic dimensions of disaster vulnerability, but few have focused on Hispanic immigrants. More research on Hispanic immigrants is needed, since they constitute a major component of the Hispanic population—the largest and fastest‐growing minority group in the U.S.—and because they experience distinctive cultural and immigration status disadvantages. We examine the flood/hurricane vulnerabilities of Hispanic immigrants in comparison to U.S.–born Hispanics and non‐Hispanic whites. Using mixed methods to analyze data from 429 surveys and 31 interviews with residents living in flood zones, we examine differences in self‐protective action, risk perception, and hazard knowledge between the three groups in Houston and Miami. Hispanic immigrants exhibited lower levels of self‐protection and hazard knowledge, and higher perceptions of risk, which reflects their heightened vulnerability. Risk‐reduction programs should target the particular vulnerabilities of Hispanic immigrants, and future studies should examine their vulnerabilities in other contexts.