Neoproterozoic iron formation: An evaluation of its temporal, environmental and tectonic significance

Neoproterozoic iron formation (NIF) provides evidence for the widespread return of anoxic and ferruginous basins during a time period associated with major changes in climate, tectonics and biogeochemistry of the oceans. Here we summarize the stratigraphic context of Neoproterozoic iron formation and its geographic and temporal distribution. It is evident that most NIF is associated with the earlier Cryogenian (Sturtian) glacial epoch. Although it is possible that some NIF may be Ediacaran, there is no incontrovertible evidence to support this age assignment. The paleogeographic distribution of NIF is consistent with anoxic and ferruginous conditions occurring in basins within Rodinia or in rift-basins developed on its margins. Consequently NIF does not require whole ocean anoxia. Simple calculations using modern day iron fluxes suggest that only models that invoke hydrothermal and/or detrital sources of iron are capable of supplying sufficient iron to account for the mass of the larger NIF occurrences. This conclusion is reinforced by the available geochemical data that imply NIF record is a mixture of hydrothermal and detrital components. A common thread that appears to link most if not all NIF is an association with mafic volcanics.Earth and Planetary Science

Trace element partitioning between majoritic garnet and silicate melt at 10-17 GPa: Implications for deep mantle processes

International audienceMelting experiments were performed on a silica-rich peridotite composition at 10-17 GPa to determine majoritic garnet-melt partition coefficients (D) for major and trace elements. Our results show that D for many elements, including Na, Sc, Y and rare earth elements (REE), varies significantly with increasing pressure or proportion of majorite component. Lu and Sc become incompatible at 17 GPa, with D decreasing from 1.5 at 10 GPa to 0.9 at 17 GPa. As predicted from lattice strain, log D for isovalent cations entering the large site of majoritic garnet exhibits a near-parabolic dependence on ionic radius. Our data are used to refine a previously published predictive model for garnet-melt partitioning of trivalent cations, which suffered from a lack of calibration in the 10-20 GPa range. Our results suggest that Archean Al-depleted komatiites from Barberton (South Africa) may have been generated by partial melting of dry peridotite at depths between 200 and 400 km. We also speculate that transition zone diamonds from Kankan (Guinea), which contain inclusions of majoritic garnet, may have formed from the partial reduction of CO2-rich magmas that subsequently transported them to the surface. This hypothesis would provide an explanation for the REE patterns of majoritic garnet trapped within these diamonds, including Eu anomalies. Finally, we show that segregation of majoritic garnet-bearing cumulates during crystallisation of a deep Martian magma ocean could lead to a variety of Lu/Hf and Sm/Nd ratios depending on pressure, leading to a range of ε143Nd and ε176Hf isotope signatures for potential mantle sources of Martian rocks

Carfilzomib, Lenalidomide, and Dexamethasone for Relapsed Multiple Myeloma.

Background Lenalidomide plus dexamethasone is a reference treatment for relapsed multiple myeloma. The combination of the proteasome inhibitor carfilzomib with lenalidomide and dexamethasone has shown efficacy in a phase 1 and 2 study in relapsed multiple myeloma. Methods We randomly assigned 792 patients with relapsed multiple myeloma to carfilzomib with lenalidomide and dexamethasone (carfilzomib group) or lenalidomide and dexamethasone alone (control group). The primary end point was progression-free survival. Results Progression-free survival was significantly improved with carfilzomib (median, 26.3 months, vs. 17.6 months in the control group; hazard ratio for progression or death, 0.69; 95% confidence interval [CI], 0.57 to 0.83; P=0.0001). The median overall survival was not reached in either group at the interim analysis. The Kaplan-Meier 24-month overall survival rates were 73.3% and 65.0% in the carfilzomib and control groups, respectively (hazard ratio for death, 0.79; 95% CI, 0.63 to 0.99; P=0.04). The rates of overall response (partial response or better) were 87.1% and 66.7% in the carfilzomib and control groups, respectively (P<0.001; 31.8% and 9.3% of patients in the respective groups had a complete response or better; 14.1% and 4.3% had a stringent complete response). Adverse events of grade 3 or higher were reported in 83.7% and 80.7% of patients in the carfilzomib and control groups, respectively; 15.3% and 17.7% of patients discontinued treatment owing to adverse events. Patients in the carfilzomib group reported superior health-related quality of life. Conclusions In patients with relapsed multiple myeloma, the addition of carfilzomib to lenalidomide and dexamethasone resulted in significantly improved progression-free survival at the interim analysis and had a favorable risk-benefit profile. (Funded by Onyx Pharmaceuticals; ClinicalTrials.gov number, NCT01080391 .)