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

Global quieting of high-frequency seismic noise due to COVID-19 pandemic lockdown measures

Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the COVID-19 pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record. While the reduction is strongest at surface seismometers in populated areas, this seismic quiescence extends for many kilometers radially and hundreds of meters in depth. This provides an opportunity to detect subtle signals from subsurface seismic sources that would have been concealed in noisier times and to benchmark sources of anthropogenic noise. A strong correlation between seismic noise and independent measurements of human mobility suggests that seismology provides an absolute, real-time estimate of population dynamics

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

Response and progression-free survival according to planned treatment duration in patients with relapsed multiple myeloma treated with carfilzomib, lenalidomide, and dexamethasone (KRd) versus lenalidomide and dexamethasone (Rd) in the phase III ASPIRE study

Background: In ASPIRE, carfilzomib, lenalidomide, and dexamethasone (KRd) significantly improved progression-free survival (PFS) and response rates versus lenalidomide and dexamethasone (Rd) in patients with relapsed multiple myeloma. Per protocol, patients received KRd for a maximum of 18 cycles followed by Rd to progression, so the benefit/risk profile of KRd to progression was not established. Methods: This post hoc analysis evaluated the efficacy and safety of KRd versus Rd at 18 months from randomization. Cumulative rates of complete response (CR) or better over time and PFS hazard ratio (HR) at 18 months were evaluated for KRd versus Rd. PFS HRs were also assessed according to cytogenetic risk, prior lines of therapy, and prior bortezomib treatment. Cox regression analysis was used to evaluate PFS HRs. Results: The hazard ratio (HR) for PFS at 18 months was 0.58 versus 0.69 for the overall ASPIRE study. Patients with high-risk cytogenetics, ≥ 1 prior lines of therapy, and prior bortezomib exposure benefited from KRd up to 18 months versus Rd. The HRs for PFS at 18 months in the pre-defined subgroups were lower than those in the overall study. The difference in the proportion of KRd and Rd patients achieving at least a complete response (CR) increased dramatically over the first 18 months and then remained relatively constant. The safety profile at 18 months was consistent with previous findings. Conclusions: The improved PFS HR at 18 months and the continued increase in CR rates for KRd through 18 cycles suggest that there may be a benefit of continued carfilzomib treatment. Trial registration: Clinical trials.gov NCT01080391. Registered 2 March 2010. © 2018 The Author(s)

Response and progression-free survival according to planned treatment duration in patients with relapsed multiple myeloma treated with carfilzomib, lenalidomide, and dexamethasone (KRd) versus lenalidomide and dexamethasone (Rd) in the phase III ASPIRE study

Abstract Background In ASPIRE, carfilzomib, lenalidomide, and dexamethasone (KRd) significantly improved progression-free survival (PFS) and response rates versus lenalidomide and dexamethasone (Rd) in patients with relapsed multiple myeloma. Per protocol, patients received KRd for a maximum of 18 cycles followed by Rd to progression, so the benefit/risk profile of KRd to progression was not established. Methods This post hoc analysis evaluated the efficacy and safety of KRd versus Rd at 18 months from randomization. Cumulative rates of complete response (CR) or better over time and PFS hazard ratio (HR) at 18 months were evaluated for KRd versus Rd. PFS HRs were also assessed according to cytogenetic risk, prior lines of therapy, and prior bortezomib treatment. Cox regression analysis was used to evaluate PFS HRs. Results The hazard ratio (HR) for PFS at 18 months was 0.58 versus 0.69 for the overall ASPIRE study. Patients with high-risk cytogenetics, ≥ 1 prior lines of therapy, and prior bortezomib exposure benefited from KRd up to 18 months versus Rd. The HRs for PFS at 18 months in the pre-defined subgroups were lower than those in the overall study. The difference in the proportion of KRd and Rd patients achieving at least a complete response (CR) increased dramatically over the first 18 months and then remained relatively constant. The safety profile at 18 months was consistent with previous findings. Conclusions The improved PFS HR at 18 months and the continued increase in CR rates for KRd through 18 cycles suggest that there may be a benefit of continued carfilzomib treatment. Trial registration Clinical trials.gov NCT01080391. Registered 2 March 2010