Mantle-derived magmas and magmatic Ni-Cu-(PGE) deposits

Magmatic Fe-Ni-Cu ± platinum-group element (PGE) sulfide deposits form when mantle-derived mafic and ultramafic magmas become saturated in sulfide and segregate immiscible sulfide liquid, commonly following interaction with crustal rocks. Although the metal contents of primary magmas influence ore compositions, they do not control ore genesis because the metals partition strongly into the sulfide liquid and because most magmas capable of segregating sulfide liquid contain sufficient abundances of ore metals. More important controls are the temperature, viscosity, volatile content, and mode of emplacement of the magma, which control the dynamics of magma emplacement and the degree of interaction with crust. By this measure, high-temperature, low-viscosity komatiites and tholeiitic picrites are most capable of forming Ni-Cu-(PGE) deposits, whereas lower-temperature, volatile-rich alkali picrites and basalts have less potential. In most deposits, ore formation is linked directly to incorporation of S-rich country rocks and only indirectly to contamination by granitic crust. However, the geochemical signature of contamination is easily recognized and is a useful exploration guide because it identifies magmas that had the capacity to incorporate crustal material. Several aspects of the ore-forming process remain poorly understood, including the control of mantle melting processes on the PGE contents of mafic-ultramafic magmas, the mechanisms by which sulfur is transferred from wall rocks to ores (bulk assimilation, incongruent melting, and/or devolatilization), the distances and processes by which dense sulfide melts are transported from where they form to where they become concentrated (as finely-dispersed droplets, as segregated layers, or by deformation-driven injection of massive sulfide accumulations), and the dynamic processes that increase the metal contents of the ores

Class III Obese Women's Preferences and Concerns for Cesarean Skin Incision: A Multicenter Survey

Objective This study aims to assess class III obese women's preferences and concerns regarding cesarean delivery (CD) skin incisions. Study Design Through the National Perinatal Research Consortium (NPRC), women with body mass index ≥ 40 kg/m2 at the time of enrollment completed an anonymous survey in English or Spanish. We evaluated seven domains of preferences and concerns about the cesarean skin incision. Results We surveyed 546 women at five NPRC sites. Median age (interquartile range) was 29 (25, 35) years; 364 (66%) were parous and 161 (30%) had a prior CD. Women self-identified race/ethnicity as White (31%), non-Hispanic Black (31%), Hispanic (31%), other (6%), and not reported (1%). A total of 542 women (99%) rated both delivering the baby in the best possible condition and decreasing incision opening/infection risk as important. Women were less likely to rate other domains as important (all p < 0.001), including: having least pain possible, n = 521 (95%); decreasing the risk of complications in the next pregnancy, n = 490 (90%); decreasing interference with breastfeeding, n = 474 (87%); decreasing operative time, n = 388 (71%); and having the least visible incision, n = 369 (68%). Conclusion Women with class III obesity prioritize immediate maternal and fetal safety regarding CD skin incision over other concerns including cosmetic outcome

Mathematical modeling of thermomechanical erosion beneath Proterozoic komatiitic basaltic sinuous rilles in the Cape Smith Belt, New Québec, Canada

Virtually all of the economic Ni-Cu-(platinum group element (PGE)) mineralization in the central part of the Cape Smith Belt of New Québec is hosted by thick olivine cumulate units in the Katinniq Member of the Raglan Formation at the base of the 1. 9 G

Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites

Several methods have been developed to assess the thermal state of the mantle below oceanic ridges, islands, and plateaus, on the basis of the petrology and geochemistry of erupted lavas. One leads to the conclusion that mantle potential temperature (i.e., TP) of ambient mantle below oceanic ridges is 1430°C, the same as Hawaii. Another has ridges with a large range in ambient mantle potential temperature (i.e., TP = 1300–1570°C), comparable in some cases to hot spots (Klein and Langmuir, 1987; Langmuir et al., 1992). A third has uniformly low temperatures for ambient mantle below ridges, ∼1300°C, with localized 250°C anomalies associated with mantle plumes. All methods involve assumptions and uncertainties that we critically evaluate. A new evaluation is made of parental magma compositions that would crystallize olivines with the maximum forsterite contents observed in lava flows. These are generally in good agreement with primary magma compositions calculated using the mass balance method of Herzberg and O'Hara (2002), and differences reflect the well-known effects of fractional crystallization. Results of primary magma compositions we obtain for mid-ocean ridge basalts and various oceanic islands and plateaus generally favor the third type of model but with ambient mantle potential temperatures in the range 1280–1400°C and thermal anomalies that can be 200–300°C above this background. Our results are consistent with the plume model

Sulfide-silicate textures in magmatic Ni-Cu-PGE sulfide ore deposits: Disseminated and net-textured ores

A large proportion of ores in magmatic sulfide deposits consist of mixtures of cumulus silicate minerals, sulfide liquid, and silicate melt, with characteristic textural relationships that provide essential clues to their origin. Within silicate-sulfide cumulates, there is a range of sulfide abundance in magmatic-textured silicate-sulfide ores between ores with up to about five modal percent sulfides, called "disseminated ores," and "net-textured" (or "matrix") ores containing about 30 to 70 modal percent sulfide forming continuous networks enclosing cumulus silicates. Disseminated ores in cumulates have various textural types relating to the presence or absence of trapped interstitial silicate melt and (rarely) vapor bubbles. Spherical or oblate spherical globules with smooth menisci, as in the Black Swan disseminated ores, are associated with silicate-filled cavities interpreted as amygdales or segregation vesicles. More irregular globules lacking internal differentiation and having partially facetted margins are interpreted as entrainment of previously segregated, partially solidified sulfide. There is a textural continuum between various types of disseminated and net-textured ores, intermediate types commonly taking the form of "patchy net-textured ores" containing sulfide-rich and sulfide-poor domains at centimeter to decimeter scale. These textures are ascribed primarily to the process of sulfide percolation, itself triggered by the process of competitive wetting whereby the silicate melt preferentially wets silicate crystal surfaces. The process is self-reinforcing as sulfide migration causes sulfide networks to grow by coalescence, with a larger rise height and hence a greater gravitational driving force for percolation and silicate melt displacement. Many of the textural variants catalogued here, including poikilitic or leopard-textured ores, can be explained in these terms. Additional complexity is added by factors such as the presence of oikocrysts and segregation of sulfide liquid during strain-rate dependent thixotropic behavior of partially consolidated cumulates. Integrated textural and geochemical studies are critical to full understanding of ore-forming systems

Assessment of proliferation of squamous, Barrett's and gastric mucosa in patients with columnar lined Barrett's oesophagus.

There is no satisfactory biomarker yet available for predicting the likelihood of premalignant changes or carcinoma developing in Barrett's or columnar lined oesophagus. In this study we have evaluated the proliferation of squamous epithelium, columnar epithelium from columnar lined oesophagus and gastric columnar epithelium from 23 Barrett's patients using positive immunoreactivity with the mouse monoclonal antibody Ki67 (which recognises an antigen associated with proliferative cells) with a view to using this parameter as a biomarker. Squamous epithelium had significantly higher Ki67 immunostaining as compared with columnar epithelium from columnar lined oesophagus (when examining the tissue with greater than 15% cells staining positive for Ki67, Fisher's exact test p = 0.004) but there was no difference found between the epithelium from the columnar lined oesophagus and gastric columnar epithelium. There was no correlation between histological inflammation and Ki67 immunoreactivity of Barrett's mucosa, and the Ki67 immunostaining of two patients with dysplasia was no different from the rest of the group. There was, however, a significant correlation between the Ki67 immunoreactivity of columnar epithelium from columnar lined oesophagus and columnar epithelium from the stomach (correlation coefficient = 0.44, p = 0.03) suggesting that epithelium from columnar lined oesophagus behaves in a similar fashion to gastric epithelium