We present partial melting experiments at 2–3 GPa on a basaltic pyroxenite (G2) similar in composition to typical oceanic crust. The 3.0 GPa solidus is located at 1310 ± 12°C and the liquidus is ...1500–1525°C. Clinopyroxene, garnet, quartz, and rutile are subsolidus phases. Garnet, quartz, and rutile are absent above 1475°C, 1365°C, and 1335°C, respectively. At the solidus, the garnet mode is low (18 wt.%) because clinopyroxene is unusually aluminous (13.8–15.5 wt.% Al2O3). In adiabatically upwelling mantle near 2–3 GPa, G2‐like pyroxenite begins melting 35–50 km deeper than peridotite. The calculated near‐solidus adiabatic productivity for G2 is ∼13%/GPa and averages ∼59%/GPa through the melting interval, suggesting substantial partial melting deep in basalt source regions: G2 is ∼60% molten at the 3 GPa peridotite solidus. Small percentages of pyroxenite in the source significantly affect oceanic crust production and composition, as the proportion of pyroxenite‐derived melt contributed to oceanic crust formation is 5 to >10 times the pyroxenite proportion in the source. Given the overall depleted isotopic character of mid‐ocean ridge basalt (MORB), oversampling of fertile G2‐like pyroxenite limits the abundance of such lithologies to ∼<2% of the MORB source. Owing to high extents of partial melting, the effect of modest amounts of pyroxenite on Sm/Yb ratios of aggregated basalts is limited and depends largely on the average bulk composition of the pyroxenite source. Low near‐solidus adiabatic productivities could allow small (∼1–2%) proportions of basaltic pyroxenite to enhance (230Th)/(238U) in oceanic basalts without requiring marked shifts in other indicators of heterogeneity, such as Sr or Pb isotopes.
Ratios of first-row transition elements (FRTE), such as Fe/Mn and Zn/Fe, may be fractionated differently by partial melting of peridotite than by partial melting of recycled lithologies like ...eclogite, and therefore may be useful as indicators of the source lithologies of mantle-derived basalts. Interpretation of basalt source lithologies from FRTE ratios requires accurate assessment of FRTE partitioning behavior between peridotitic minerals and coexisting melts. We present experimental determinations of partition coefficients for several of the FRTE (Sc, Ti, V, Cr, Mn, Fe, Co, Zn) and Ga and Ge between basaltic melt and olivine, garnet, pyroxenes, and spinel at 3GPa. Because mineral/melt partitioning is sensitive to phase compositions, a key feature of these experiments is that the melts and minerals are known from previous experiments to be in equilibrium at the solidus of garnet peridotite at 3GPa. Therefore, these partition coefficients are directly applicable to near-solidus partial melting of the mantle at 3GPa. We use these partition coefficients to calculate compositions of model partial melts of peridotite and compare these to natural OIB. Model partial melts of peridotite have lower Fe/Mn (<62) and higher Co/Fe (>7*10−4) than many primitive OIB, which implies that some other source lithology participates in the formation of many OIB. Alternatively, these ratios may potentially be produced by garnet peridotite if the source contains ∼0.3% Fe2O3, consistent with observations from continental xenoliths. Zn/Fe is a less sensitive indicator of non-peridotite source lithology than either Fe/Mn or Co/Fe, as Zn/Fe in partial melts of peridotite overlaps with >75% of primitive OIB. Ga and Sc are fractionated significantly by residual garnet, and high Ga/Sc may indicate the presence of garnet in basalt source regions. When taking into account several FRTE ratios simultaneously, few OIB appear to be consistent with derivation solely from a reduced peridotitic source. The source either must have a modest non-peridotitic component, be Fe-enriched, or be slightly oxidized.
We present partial melting experiments that constrain the near solidus phase relations of carbonated eclogite from 2 to 8.5 GPa. The starting material was prepared by adding 5 wt.% CO
2 in the form ...of a mixture of Fe–Mg–Ca–Na–K carbonates to an eclogite from Salt Lake crater, Oahu, Hawaii and is a reasonable approximation of carbonated oceanic crust from which siliceous hydrous fluids have been extracted during subduction. Melt-present versus melt-absent conditions are distinguished based on textural criteria. Garnet and clinopyroxene appear in all the experiments. Between 2 and 3 GPa, the subsolidus assemblage also includes ilmenite±calcio-dolomite
ss±CO
2, whereas above the solidus (1050–1075 °C at 3 GPa) calcio-dolomitic liquid appears. From 3 to 4.5 GPa, dolomite
ss is stable at the solidus and the near-solidus melt becomes increasingly dolomitic. The appearance of dolomite above 3 GPa is accompanied by a negative Clapeyron slope of the solidus, with a minimum located between 995 and 1025 °C at ca. 4 GPa. Above 4 GPa, the solidus rises with increasing pressure to 1245±35 °C at 8.5 GPa and magnesite becomes the subsolidus carbonate. Dolomitic melt coexists with magnesite+garnet+cpx+rutile along the solidus from 5 to 8.5 GPa.
Comparison of our results to other recent experimental studies T. Hammouda, High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle, Earth Planet. Sci. Lett. 214 (2003) 357–368; G.M. Yaxley, G.P. Brey, Phase relations of carbonate-bearing eclogite assemblages from 2.5 to 5.5 GPa: implications for petrogenesis of carbonatites, Contrib. Mineral. Petrol. 146 (2004) 606–619 shows that carbonate minerals are preserved in anhydrous or slightly hydrous carbonated eclogite to temperatures >1100 and >1200 °C at 5 and 9 GPa, respectively. Thus, deep subduction of carbonate is expected along any plausible subduction geotherm. If extrapolated to higher pressures, the carbonated eclogite solidus is likely to intersect the oceanic geotherm at a depth close to 400 km. Carbonated eclogite bodies entering the convecting upper mantle will thus release carbonate melt near the top of the mantle transition zone and may account for anomalously slow seismic velocities at depths of 280–400 km. Upon release, this small volume, highly reactive melt could be an effective agent of deep mantle metasomatism. Comparison of the carbonated eclogite solidus with that of peridotite-CO
2 shows a shallower solidus–geotherm intersection for the latter. This implies that carbonated peridotite is a more likely proximal source of magmatic carbon in oceanic provinces. However, carbonated eclogite is a potential source of continental carbonatites, as its solidus crosses the continental shield geotherm at ca. 4 GPa. Transfer of eclogite-derived carbonate melt to peridotite may account for the geochemical characteristics of some oceanic island basalts (OIBs) and their association with high CaO and CO
2.
Bimineralic eclogite, which consists solely of garnet and clinopyroxene, is a likely component of some of the ancient recycled crust residing in basalt source regions. It may originate during ...subduction of altered mid-ocean ridge basalt (MORB) crust, owing to extraction of small degree partial melts or siliceous hydrous fluids. It may also originate by fractional removal of early-formed partial melts from recycled crust or from pyroxenite originating by other processes. We have performed high-pressure experiments on a bimineralic eclogite (B-ECL1) and its mixture with olivine (B-ECL1-OL) at 3 and 5 GPa. Degrees of melting are slightly higher for B-ECL1-OL than for B-ECL1 at given temperatures, suggesting that addition of small amounts of olivine enhances melt productivity of bimineralic eclogite. Solidus and liquidus temperatures of B-ECL1 are slightly higher than those of B-ECL1-OL and MORB-like pyroxenite, but are lower than those of high-MgO pyroxenite and peridotite, suggesting that bimineralic eclogite is not necessarily refractory compared to other likely mantle lithologies. Partial melts of B-ECL1 and B-ECL1-OL are nepheline-normative. Because garnet and clinopyroxene in these compositions partially melt at a eutectic-like minimum with a composition that is nepheline-normative, a wide range of bimineralic eclogite compositions, including that of subducted-crust origin, that consist of garnet and clinopyroxene with compositions similar to those of B-ECL1 can produce nepheline-normative (=
alkali
−
basaltic) liquids. Thus, in contrast to the common assumption that partial melting of recycled oceanic crust produces silicic magmas, we conclude that such lithologies can produce nepheline-normative partial melts if they first experience fractional removal of fluids or melts. The partial melts from B-ECL1 are too low in MgO to be parental to many alkalic OIB, but have low Al
2O
3 and high FeO comparable to those of alkalic OIB, suggesting that bimineralic recycled crust is a potential source for a low-Al
2O
3 and high-FeO component that is necessary for the genesis of alkalic OIB.
A review of experiments on natural peridotites allows improved constraints on the location of the mantle solidus. Available constraints on the location of the nominally dry peridotite solidus show ...considerable scatter, owing to interlaboratory uncertainties and the effects of bulk composition. When experiments on enriched peridotite are filtered from the database, the best fit to the solidus between 0 and 10 GPa is given by T(°C) = aP2 + bP + c where a = −5.104, b = 132.899, and c = 1120.661 and P is in gigapascals. Compared to previous models, the solidus in this parameterization is at lower temperature between 2 and 6 GPa, with the largest differences near 4 GPa, where it is 30°–60°C cooler. Consideration of experimental constraints on the peridotite solidus and of a theoretical model of melting in a simple analogue system suggests that a key variable affecting peridotite solidus temperature is the near‐solidus liquid alkali concentration. The effect of alkalis on the solidus increases with bulk concentration in the peridotite but decreases with bulk partition coefficient. Thus small bulk concentrations of K can have a significant influence on the peridotite solidus, and the effect of Na diminishes with increasing pressure, as it becomes more compatible in the solidus residua. Mg # =100 × MgO/(MgO + FeO) variations are subordinate to alkali variations in controlling solidus temperature at lower pressures but may increase in relative importance as alkalis become more compatible in peridotite residua with increasing pressure. Increased clinopyroxene mode has the effect of making Na more compatible in residual solids and so diminishes the solidus‐lowering tendencies of alkalis. As a consequence, experiments performed on a range of peridotite compositions may not reflect the likely effect of variable mantle composition on solidus temperature if they do not match the appropriate correlation between alkali content and clinopyroxene mode.
We present melt and mineral compositions from nominally anhydrous partial melting experiments at 2–3 GPa on a quartz eclogite composition (G2) similar to average oceanic crust. Near-solidus partial ...melts at 3 GPa, determined with melt traps of vitreous carbon spheres, have 55–57 wt % SiO2, rather less silica than the dacitic compositions that are generally assumed for near-solidus eclogite partial melts. At 2 GPa, equivalent near-solidus partial melts are less silicic (≤52 wt % SiO2). The 3 GPa near-solidus partial melts (up to melt fractions of ∼3%) are saturated in rutile and have 5·7–6·7 wt % TiO2. The G2 composition is K2O-poor (0·03 wt %), but a modified composition with 0·26 wt % K2O (G2K) produces dacitic near-solidus melts with 61–64 wt % SiO2. Rutile saturation for G2K extends to higher melt fraction (∼13%) and occurs at lower TiO2 melt contents (3·3 wt %) than for G2. These results can be understood in terms of a simplified thermodynamic model in which alkalis increase the SiO2 content of liquids saturated in quartz, which in turn diminishes the TiO2 concentrations required to maintain rutile saturation. Additionally, the mode of residual garnet and generation of silicic liquids by partial melting of anhydrous eclogite are linked, as garnet is required to mass-balance formation of appreciable SiO2-rich melt. Partitioning of Na between clinopyroxene and melt shows significant increases with pressure, but only modest shifts with changing temperature. In contrast, partitioning of Ti between cpx and melt, as well as between cpx and garnet, shows pronounced dependence on temperature for compositions relevant to anhydrous partial melting of eclogite. Mixtures between partial melts of eclogite and primitive picritic Hawaiian magmas are similar to magnesian, SiO2-rich compositions inferred from melt inclusions from the Koolau volcano. However, in detail, no eclogitic partial melt has been identified that is capable of explaining all of the compositional features of the exotic Koolau component. Based on phase compositions in our experiments, the calculated density of near-solidus eclogite is 3440 kg/m3, notably less than commonly assumed. Therefore, the excess temperature required for a plume to support a given proportion of eclogite in the upper mantle may be less than previously assumed.
Carbon is an essential element for life, but its behavior during Earth's accretion is not well understood. Carbonaceous grains in meteoritic and cometary materials suggest that irreversible ...sublimation, and not condensation, governs carbon acquisition by terrestrial worlds. Through astronomical observations and modeling, we show that the sublimation front of carbon carriers in the solar nebula, or the soot line, moved inward quickly so that carbon-rich ingredients would be available for accretion at 1 astronomical unit after the first million years. On the other hand, geological constraints firmly establish a severe carbon deficit in Earth, requiring the destruction of inherited carbonaceous organics in the majority of its building blocks. The carbon-poor nature of Earth thus implies carbon loss in its precursor material through sublimation within the first million years.
Purpose
Periprosthetic joint infections (PJIs) represent a devastating consequence of total joint arthroplasty. The European Knee Associates (EKA), the American Association of Hip and Knee Surgeons ...(AAHKS) International Committee, and the Arthroplasty Society in Asia (ASIA) board members were interested in quantifying differences in arthroplasty surgeons’ use of various PJI prevention measures to provide clinical recommendations to reduce PJI incidence.
Methods
A prospective Microsoft Forms online survey was distributed among EKA, AAHKS International Committee, and ASIA members and their affiliated arthroplasty surgeons. The survey consisted of 20 single and multiple response questions focused on PJI prevention strategies at three perioperative periods: preoperatively, intraoperatively, and postoperatively.
Results
Three hundred and ninety-four arthroplasty surgeons from 6 different continents completed the survey.
Preoperative
: (A) PJI Risk Stratification: 40.6% routinely set thresholds (e.g., BMI, HgbA1C) to be met to qualify for surgery, 36.5% only review past medical history; 9.1% use machine learning to personalize PJI risk; (B) BMI limit: 36% no limit; 15.4% BMI < 35; 30.9% BMI < 40; 17.2% BMI < 45; (C) Nutritional status: 55.3% do not screen; among those who screen their patients (44.7%), albumin is the single most used marker (86.3%); (D) Hyperglycemia/Diabetes: 83.3% check this comorbidity; 88.1% use HgbA1C as single best screening test; (E) MRSA nasal colonization: 63.7% do not test; 28.9% test all patients; 7.4% test selectively.
Intraoperative
: (A) Antibiotic prophylaxis in high-risk patients: 43.4% use single antibiotic for 24 h; 21.3% use double antibiotic for 24 h; 14.2% use single/double antibiotic for 7 days postoperatively; (B) Skin-cleansing: 68.7% at home (45.6% chlorhexidine sponge; 11.9% clippers); (C) Intraoperative skin disinfection: 46.9% single chlorhexidine; 25% double chlorhexidine–povidone-iodine;15.4% single povidone-iodine; (D) Tranexamic acid (TXA) to reduce bleeding/SSI: 96% yes (51% double IV dose, 35.2% single IV dose, 23.6% intra-articular injection); (E) Surgical suction drain: 52% do not use drains; 19.7% use a drain < 24 h; (F) Intra-articular lavage: 64.9% use only saline; 28.1% use dilute povidone-iodine; (G) Antibiotic local delivery to prevent PJI: 82.4% use antibiotic-added cement.
Postoperative
: (A) Routine monitoring of PJI serologic markers: 42% only in symptomatic patients; 34.2% do not; 20.8% in all patients; (B) Serologic markers to rule in/out PJI: 95.9% CRP; 71% SEDRATE; 60.6% WBC; (C) Synovial fluid test to rule in/out PJI: 79.6% culture/sensitivity; 69.5% WBC count; 31.4% CRP.
Conclusions
This survey demonstrated that notable differences still exist in the application of PJI preventive measures across different geographic areas: Optimizing the patient preoperatively and applying multimodal intraoperative strategies represent newer, clinically relevant steps in the effort to reduce the burden of PJI. More uniform guidelines still need to be produced from international scientific societies in order facilitate a more comprehensive approach to this devastating complication.
Level of evidence
IV.
Graphical abstract
The H2O storage capacity of nominally anhydrous minerals or rocks is the concentration of water that can be sequestered in the mineral(s) without stabilizing a hydrous fluid or melt. The storage ...capacity of the upper mantle is considerably greater than generally appreciated, as recent studies show that H2O uptake in olivine is 3 times that originally inferred by Kohlstedt et al. D.L. Kohlstedt, H. Keppler, D.C. Rubie, Solubility of water in the a, b and g phases of (Mg,Fe)2SiO4, Contrib. Mineral. Petrol. 123 1996 345- 357. and, at least at low pressure, pyroxene stores considerably more H2O than olivine. Consequently, H2O has smaller influence on small degree melting than inferred previously. Combining data on the storage capacity of olivine with constraints on partition coefficients between olivine, pyroxene, and garnet, we estimate that the storage capacity of the upper mantle just above the 410 km discontinuity is > 0.4 wt.%. Owing to the increasing mode of garnet at the expense of pyroxene, there is likely to be a local maximum in storage capacity between 350 and 400 km, and a local minimum just above the onset of wadsleyite stability. Although published data suggest that the storage capacity of wadsleyite diminishes with increasing temperature, the storage capacity of the transition zone likely is considerable because Fe-bearing wadsleyite has a larger storage capacity than Mg2SiO4. Peridotite upwelling from the transition zone will undergo partial melting above the 410 km discontinuity only if it has more H2O than the local storage capacity (i.e., > 0.4 wt.%), and the dehydrated residue cannot be drier than this unless it melts further under conditions where the storage capacity is less. Because residues of partial melting at 410 km have much more H2O than the 50-200 ppm H2O in the average upper mantle, they cannot be principal sources for the upper mantle. If hydrous melting occurs at 410 km, further upwelling of the residual peridotite will result in continued melting throughout the upper mantle, unless the storage capacity increases with decreasing depth. The partition coefficient of H2O between wadsleyite and olivine is 5, which is less extreme than previously assumed. Consequently, the effect of H2O on the depth and thickness of the 410 discontinuity may not be pronounced and typical (10 km) discontinuity thickness can be reconciled with up to 400 ppm H2O.
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