Comments on “Composition and depth of origin of primary mid-ocean ridge basalts” by D.C. Presnall and J.D. Hoover

Presnall and Hoover (1984), in their evaluation of the nature of primary mid-ocean ridge basalts (MORBs), concluded that earlier data suggesting many of the most primitive MORBs are derived from high-MgO (picritic) magmas are not valid. In reaching this conclusion, Presnall and Hoover (1984) ignore several important considerations regarding 1. analytical uncertainties, 2. TiO₂abundances in MORBs, 3. least-squares calculations, 4. complex models of magmatic evolution and 5. enstatite saturation. I briefly discuss these points below.     

Changes in the patterns of contact between anglophones and francophones in Quebec

When Britain assumed responsibility for the French Colonies in North America (1763) the French (francophones) were concentrated in the St. Lawrence Lowlands. Subsequent settlements by British and American colonists (anglophones) were guided by government policy, economic opportunities, and political events. The outcome was a mixture of anglophone settlers initially, as intended, developing around the lowland French but subsequently evolving to a peripheral location. Crowded conditions forced the francophones to move into this peripheral area as well. Through these processes a cultural zone of transition evolved between Quebec and her neighbouring provinces. Contact between the two ethnic groups within this zone, however, has not led to integration but moreso to a cultural division. In this situation it has been generally the francophone who has accommodated to the anglophone for required social and vocational interaction. Through the application of the index of language intensity assessment of the impact of recent sociopolitical policies upon this traditional pattern has been made. In the past decade anglophones have been leaving Quebec at an accelerated rate. Those remaining have an opportunity to increase the processes of interaction and integration with the francophone society and, it is theorized, will do so if a negative attitude among the youth toward a future in the province can be overcome.     

Determination of Horizontal Aquifer Anisotropy with Three Wells

Existing methods for the determination of horizontal aquifer anisotropy by means of pumping tests require a minimum of four wells, one for water withdrawal and three for drawdown observations. This paper shows how the same methods can be used to determine anisotropy with as few as three wells, if at least two of them can be pumped in sequence. A field example is included. A method of analyzing data from more wells than the above minimum, by least squares, is also described.     

Advancing the understanding of variations of Arctic sea ice optical and thermal behaviors through an international research and mobility project

In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy ba...     

An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials

Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site...     

“All the World's a Stage”: A GIS Framework for Recreating Personal Time‐Space from Qualitative and Quantitative Sources

This article presents a methodological model for the study of the space‐time patterns of everyday life. The framework utilizes a wide range of qualitative and quantitative sources to create two environmental stages, social and built, which place and contextualize the daily mobilities of individuals as they traverse urban environments. Additionally, this study outlines a procedure to fully integrate narrative sources in a GIS. By placing qualitative sources, such as narratives, within a stage‐based GIS, researchers can begin to tell rich spatial stories about the lived experiences of segregation, social interaction, and environmental exposure. The article concludes with a case study utilizing the diary of a postal clerk to outline the wide applicability of this model for space‐time GIS research.     

Liquidus Equilibria in the System K2O-Na2O-Al2O3-SiO2-F2O-1-H2O to 100 MPa: I. Silicate-Fluoride Liquid Immiscibility in Anhydrous Systems

Liquidus relations in the four-component system Na₂O–Al₂O₃–SiO₂–F₂O_–1were studied at 0· 1 and 100 MPa to define the locationof fluoride–silicate liquid immiscibility and outlinedifferentiation paths of fluorine-bearing silicic magmas. Thefluoride–silicate liquid immiscibility spans the silica–albite–cryoliteand silica–topaz–cryolite ternaries and the haplogranite-cryolitebinary at greater than 960°C and 0· 1–100 MPa.With increasing Al₂O₃ in the system and increasing aluminum/alkalication ratio, the two-liquid gap contracts and migrates fromthe silica liquidus to the cryolite liquidus. The gap does notextend to subaluminous and peraluminous melt compositions. Forall alkali feldspar–quartz-bearing systems, the miscibilitygap remains located on the cryolite liquidus and is thus inaccessibleto differentiating granitic and rhyolitic melts. In peralkalinesystems, the magmatic differentiation is terminated at the albite–quartz–cryoliteeutectic at 770°C, 100 MPa, 5 wt % F and cation Al/Na =0· 75. The addition of topaz, however, significantlylowers melting temperatures and allows strong fluorine enrichmentin subaluminous compositions. At 100 MPa, the binary topaz–cryoliteeutectic is located at 770°C, 39 wt % F, cation Al/Na 0·95, and the ternary quartz–topaz–cryolite eutecticis found at 740°C, 32 wt % F, 30 wt % SiO₂ and cation Al/Na 0· 95. Such location of both eutectics enables fractionationpaths of subaluminous quartz-saturated systems to produce fluorine-rich,SiO₂-depleted and nepheline-normative residual liquids. KEY WORDS: silicate melt; granite; rhyolite; fluorine; liquid immiscibility