Ion Probe Study of Silicate Inclusions from Colomera (ⅡE) Iron Meteorite: the Rare Earth Element Perspective

Coupled with a petrographical study, I carried out an ion probe study of rare earth element microdistributions in mineral phases of silicate inclusions from the Colomera ⅡE iron meteorite. Most mineral grains have homogeneous REEs, but show considerable inter-grain variations by a factor of 2 to 100. The whole rock REE abundances for Colomera, estimated by combining REE data with modal abundances, are relatively LREE-enriched with REEs of -10'CI, which suggest that Colomera silicates were highly differentiated and might represent a low degree partial melt (-10%) of a chondritic source. REE geochemistry of Colomera silicate inclusions points to an origin that involves differentiation, dynamic mixing, remelting, reduction, recrystallization, and subsequent rapid cooling near the surface of a planetary body.     

A review of mantle xenoliths and their role in diamond exploration

An historical introduction to the geotherm and its significance for the existence of a diamond window at the base of the peridotite lithosphere is followed by a brief survey of types of mantle zenoliths (low T, high T and metasomatized peridotites, megacrysts or discrete nodules, eclogites and less common varieties). The similarities of eclogite xenoliths to the subducted eclogites with graphitized diamonds in the peridotite massif of Beni Bousera, northern Morocco, are reviewed. Diamond-bearing peridotite (Archaean harzburgite and lherzolite) and eclogite xenoliths are rare, having suffered excessive disaggregation. They do not necessarily relate proportionately to the types of diamonds in the host kimberlite/lamproite.Batches of single mineral species from disaggregated diamondiferous xenoliths, particularly garnets, form a realistic approach to diamond exploration. Nickel thermometry applied to Cr pyropes, developed by Griffin et al. (1989) Contr. Miner. Petrol. 103, 199–203, and barometry dependent upon Cr content in notional coexisting spinels, provide a realistic appreciation of the extent of the diamond window. Sodium and K pressure “indicators” in eclogitic garnets and clinopyroxenes are reviewed, but estimates are affected by mantle processes (metasomatism) and amounts of coexisting P and Ti.Metasomatic processes in the basal lithosphere are sourced in the underlying asthenospheric (megacryst) magmas. Depending on the degree and type of interaction they can result in the destruction of ancient diamonds or the growth of new peridotitic diamonds. Partial destruction or replacement of mineral indicators may also result and Cr garnets acquire distinctive quantifiable trace element signatures. High T minerals encapsulated in diamond are either relict from former ambient high T conditions or the result of localized thermal highs emanating from asthenospheric magmas (or plume/diapir).It is concluded that the fullest significance of the geochemistry (sensuo lato) of the diamondiferous debris erupted by kimberlites and lamproites, can only be made by reference to complementary geophysical, structural and isotopic studies of the surrounding cratonic country rocks. Thus, tectonothermal events which punctuate the varied evolutionary histories of cratons—plume migration, rifting, subduction/overthrusting, delamination, cratonization, flood basalt generation, regional metamorphism and metasomatism, etc.—can be manifested in the deep lithosphere environment, and cannot be divorced from questions of diamond formation and survival.     

应用烃类流体包裹体GOI和成分研究凝析气藏成藏过程：以准噶尔盆地莫索湾地区为例

The Grains containing Oil Inclusions(GOI)data in currently gas/condensate-beating Jurassic and Cretaceous reservoir sandstones of Well Pen 5(the Mosuowan area of central Junggar Basin,NW China)are generally greater than the empirical threshold line of 5%.This is consistent with the gas-condensate section originally containing a palaeo-oil column.In order to assess the origin of the oil trapped in the oil inclusion and its relationship to the free oil/gas-condensate,a detailed molecular geochemical study was carried out for correlation between the free and inclusion oils.The paleo oil is most likely sourced from the Lower Permian Fengeheng Formation,which generated hydrocarbons primarily during Late Triassic and the oils were later secondarily altered and dysmigrated along faults likely during Late Jurassic-Early Cretaceous.In contrast,the current reservoired oil/gas-condensate mainly derived from the Middle Permian Lower Wuerhe Formation,whose peak generation time last from Late Cretaceous even to the present.This paper showed that integrated oil-bearing fluid inclusion analyses have likely allowed a complex multi-phase charge history to be recognized and resolved with a high degree of confidence.     

Bulge Migration and Pinnacle Reef Development, Devonian Appalachian Foreland Basin

Detailed stratigraphic analyses of Late Emsian and Early Eifelian (Lower to Middle Devonian) carbonate-dominated strata in the northern Appalachian Basin indicate anomalous, locally varying relative sea level changes and inversions of topography. The distribution of a major basal-bounding unconformity, basinal pinnacle reefs, local absence of parasequences, and eastward migration of shallow marine carbonate lithofacies and related biofacies in the Onondaga Limestone and underlying strata mark the retrograde migration of an elongate, northeast-southwest-trending area of positive relief, bordered on its cratonward side by a similarly migrating basin of intermediate depth. These features are thought to represent the forebulge and back-bulge basin of the Appalachian foreland basin system as it developed during a time of relative quiescence within the Acadian Orogeny. However, the relatively small size of the bulgelike feature (ca. 80-100-km-wide, 20-50-m positive relief), its great distance from the probable deformation front (>400 km), and the lack of a well-developed foredeep immediately adjacent to the bulgelike feature may indicate that it represents a smaller-scale flexural high ("flexural welt") superposed over the cratonward edge of the larger-scale classical forebulge of the basin. Development of shallow-water reefs on the crest of the bulge during sea level lowstand, followed by migration of the bulge and widespread transgression, permitted growth of economically significant pinnacle reefs in the deep basin center. Further subsurface reef exploration should concentrate along the projected position of the bulge during the basal Onondaga lowstand.     

Recovery of interior brackish marshes seven years after the chalk point oil spill

Seven years after the April 2000 spill of 140,000 gallons of a mixture of No. 6 and No. 2 fuel oils in the Patuxent River, Maryland, heavily oiled brackish marshes showed continuing effects. Stem density and stem height were significantly lower in oiled versus unoiled sites for Spartina alterniflora but not Spartina cynosuroides habitats. In contrast, belowground biomass was significantly lower in S. cynosuroides habitats but not S. alterniflora habitats. Total PAH concentrations were up to 453 mg/kg in surficial soils (0-10 cm) and 2921 mg/kg with depth (10-20 cm). The oil had lost 22-76% of its initial PAH content after seven years, although the oil in marsh soils has undergone little to no additional weathering since Fall 2000. Based on amphipod acute toxicity tests and sediment quality guidelines, 25% of the soils in the marsh are expected to be toxic (ESB-TU_FCV values > 3.0; P_Max > 0.65).     

Natural and anthropogenic nitrogen uptake by bloom-forming macroalgae

The frequency and duration of macroalgal blooms have increased in many coastal waters over the past several decades. We used field surveys and laboratory culturing experiments to examine the nitrogen content and delta(15)N values of Ulva and Gracilaria, two bloom-forming algal genera in Narragansett Bay, RI (USA). The northern end of this bay is densely populated with large sewage treatment plant nitrogen inputs; the southern end is more lightly populated and opens to the Atlantic Ocean. Field-collected Ulva varied in delta(15)N among sites, but with two exceptions had delta(15)N above 10 per thousand, reflecting a significant component of heavy anthropogenic N. This variation was not correlated with a north-south gradient. Both Ulva and Gracilaria cultured in water from across Narragansett Bay also had high signals (delta(15)N= approximately 14-17 per thousand and 8-12 per thousand, respectively). These results indicate that inputs of anthropogenic N can have far-reaching impacts throughout estuaries.     

The impact of changing climate on phenology,productivity, and benthic–pelagic coupling in Narragansett Bay

The timing and magnitude of phytoplankton blooms have changed markedly in Narragansett Bay, RI (USA) over the last half century. The traditional winter–spring bloom has decreased or, in many years, disappeared. Relatively short, often intense, diatom blooms have become common in spring, summer, and fall replacing the summer flagellate blooms of the past. The annual and summer mean abundance (cell counts) and biomass (chl a) of phytoplankton appear to have decreased based on almost 50 years of biweekly monitoring by others at a mid bay station. These changes have been related to warming of the water, especially during winter, and to increased cloudiness. A significant decline in the winter wind speed may also have played a role. The changes in the phenology of the phytoplankton and the oligotrophication of the bay appear to have decreased greatly the quantity and (perhaps) quality of the organic matter being deposited on the bottom of the bay. This decline has resulted in a very much reduced benthic metabolism as reflected in oxygen uptake, nutrient regeneration, and the magnitude and direction of the net flux of N₂ gas. Based on many decades of standard weekly trawls carried out by the Graduate School of Oceanography, the winter biomass of bottom feeding epibenthic animals has also declined sharply at the mid bay station. After decades of relatively constant anthropogenic nitrogen loading (and declining phosphorus loading), the fertilization of the bay will soon be reduced during May–October due to implementation of advanced wastewater treatment. This is intended to produce an oligotrophication of the urban Providence River estuary and the Upper Bay. The anticipated decline in the productivity of the upper bay region will probably decrease summer hypoxia in that area. However, it may have unanticipated consequences for secondary production in the mid and lower bay where climate-induced oligotrophication has already much weakened the historically strong benthic–pelagic coupling.     

Soil Plug Effect Prediction and Pile Driveability Analysis for Large-Diameter Steel Piles in Ocean Engineering

Long steel piles with large diameters have been more widely used in the field of ocean engineering.Owing to the pile with a large diameter,soil plug development during pile driving has great influences on pile driveability and beating capacity.The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service.This paper addresses the former aspect.A numerical procedure for soil plng effect prediction and pile driveability analysis is proposed and described.By taking into consideration of the pile dimension effect on side and tip resistance,this approach introduces a dimensional coefficient to the conventional static equilibrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction.At the same time,this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soft ping and pile inner wall.The proposed approach has been applied in practical engineering analyses.Results show that the calculated plug effect and pile driveability based on the proposed approach agree well with the observed data.     

Increasing nutrient concentrations and the rise and fall of a coastal fishery; a review of data from the Nile Delta,Egypt

There is a conceptual basis, and some empirical evidence, that increasing nutrient loads to coastal waterbodies will initially increase ecosystem productivity up to a threshold, beyond which secondary productivity and fishery yields will decline. Here we have compiled data from the Egyptian and international literature for fish landings and inorganic nutrient (nitrogen and phosphorus) data from four large coastal lagoons (63–500 km²) on Egypt's Nile Delta to provide evidence for the initially positive, but then negative, response of fishery yields to increased nutrient supply across a very wide range of enrichment (up to 1 mM dissolved organic nitrogen, DIN). Taking the data from the four lagoons as an aggregate, fish landings increase with increased nutrients up to a peak in landings at approximately 100 μM DIN, beyond which there was an exponential decline in landings. It appears that pesticide and heavy metal contamination and overfishing played only minor roles in the lowered fishery yield at highest DIN concentrations. We do not have sufficient evidence about the specific mechanisms that led to the decline of the fishery, but suspect that some feature of eutrophication—low oxygen, for example, may have been involved.