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Carbonatite intrusions host the world’s most important light rare earth element (LREE) deposits, and their formation generally requires extraordinary fertile sources, magmatic evolution, and hydrothermal events. However, carbonatitic magma evolution, particularly the role of fractional crystallization and contamination from silicate rocks in REE enrichment, remains enigmatic. The Maoniuping world-class REE deposit in southwestern China, is an ideal target to decipher magmatic evolution and related REE enrichment as it shows continuous textual evolution from medium- to coarse-grained calcite carbonatite (carbonatite I) at depth, to progressively pegmatoidal calcite carbonatite (carbonatite II) at shallow levels. In both types of calcite carbonatites, four generations of calcite can be classified according to petrographic and geochemical characteristics. Early-crystalizing calcite (Cal-I and Cal-II) are found in carbonatite I and exhibit equigranular and a polygonal mosaic textures, while late calcites (Cal-III and Cal-IV) in carbonatite II are large-size oikocrysts (>0.5 mm in length) with strain-induced undulatory extinction and bent twinning lamellae. All these generations of calcite yield similar, near-chondritic, Y/Ho ratios (26.6−28.1) and are inferred to be of magmatic origin. Remarkably, gradual enrichment of MgO, FeO and MnO from Cal-I to Cal-IV is coupled with a significant increase in REE contents (~800 to 2000 ppm), with LREE-rich and gentle-to-steep chondrite-normalized REE patterns ((La/Yb)N = 3.1–26.8 and (La/Sm)N = 0.9–3.9, respectively). Such significant REE enrichment is ascribed to protracted magma fractional crystallization with initial low degree of fractional crystallization (fraction of melt remining (F) = ~0.95) evolving to late stage (F = 0.5–0.6) by formation of abundant calcite cumulates. Differential LREE and HREE behavior during magma evolution largely depend on separation of phlogopite, amphibole, and clinopyroxene from the carbonatitic melt, which is indicated by progressively elevated (La/Yb)N ratios ranging from 3.1 to 26.8. The four generations of calcite have significantly different C and Sr isotopic compositions with δ13CV-PDB decreasing from –3.28 to –9.97 ‰ and 87Sr/86Sr increasing from 0.70613 to 0.70670. According to spatial relations and petrographic observations, the relative enrichment of δ13C and depletion in 87Sr/86Sr ratios of Cal-I and Cal-II show primary isotopic characteristics inherited from initial carbonatitic magma. By contrast, the variable Sr and C isotopic compositions of Cal-III and Cal-IV are interpreted as the results of contamination by components derived from silicate wall rocks and loss of CO2 by decarbonation reactions. To model such contamination processes, Raleigh volatilization and Monte Carlo simulation have been invoked and the model results reveal that carbonatitic melt-wall rock interaction requires 40% radiogenic Sr contamination from silicate rocks and 35% CO2 degassing from carbonatitic melt. Moreover, positive correlations between decreasing δ13C values and increasing REE contents, together with bastnäsite-(Ce) precipitation, indicate further REE accumulation during the contamination processes. In summary, alongside REE-rich magma sources, the extent of fractional crystallization and contamination during carbonatitic magma evolution are inferred to be important mechanisms in terms of REE enrichment and mineralization in carbonatite-related REE deposits worldwide.

Background: An abdominal phlegmon is an inflammatory mass that can develop in the setting of penetrating Crohn's disease (CD). Anti-tumor necrosis factor (TNF) antibody therapy is typically avoided in CD complicated by phlegmon because of concern for peritoneal infection but may offer an effective alternative to surgical resection after infection has been controlled with antibiotics. The aim of this study was to examine outcomes for patients with CD who developed an abdominal phlegmon that was subsequently treated with an anti-TNF antibody. Methods: We retrospectively reviewed the records of all CD patients attending Beth Israel Deaconess Medical Center between 2004 and 2010 with an abdominal phlegmon who were treated with an anti-TNF antibody in order to evaluate the safety and efficacy of this treatment regimen. Results: There were 13 patients with CD complicated by a phlegmon treated with antibiotics and an anti-TNF antibody at our center between 2004 and 2010. Ten were male. Median time (interquartile range) from diagnosis to development of the phlegmon was 5.9 (1.9–22.7) years. The phlegmon was associated with an abscess in 12 patients. In addition to anti-TNF therapy, all patients were treated with broad-spectrum antibiotics. Anti-TNF therapy was effective without complications in all subjects. Two patients eventually had surgery more than a year after initiating anti-TNF treatment. Conclusions: Penetrating CD complicated by phlegmon formation may be safely and effectively managed with a combination of antibiotics and anti-TNF therapy. Larger, prospective trials are required to confirm these initial findings. (Inflamm Bowel Dis 2011;)

Caenorhabditis elegans has been used as a host for the study of bacteria that cause disease in mammals. However, a significant limitation of the model is that C. elegans is not viable at 37 °C. We report that the gonochoristic nematode Panagrellus redivivus survives at 37 °C and maintains its life cycle at temperatures up to and including 31.5 °C. The C. elegans pathogens Pseudomonas aeruginosa, Salmonella enterica, Staphylococcus aureus, but not Yersinia pseudotuberculosis, reduced P. redivivus lifespan. Of four strains of Burkholderia multivorans tested, one reduced P. redivivus lifespan at both temperatures, one was avirulent at both temperatures and two strains reduced P. redivivus lifespan only at 37 °C. The mechanism by which one of these strains killed P. redivivus at 37 °C, but not at 25 °C, was investigated further. Killing required viable bacteria, did not involve bacterial invasion of tissues, is unlikely to be due to a diffusible, bacterial toxin and was not associated with increased numbers of live bacteria within the intestine of the worm. We believe B. multivorans may kill P. redivivus by a temperature-regulated mechanism similar to B. pseudomallei killing of C. elegans.