Ultra-depleted, shallow cratonic mantle beneath West Greenland: dunitic xenoliths from Ubekendt Ejland

Dunitic xenoliths from late Palaeogene, alkaline basalt flows on Ubekendt Ejland, West Greenland contain olivine with 100 × Mg/(Mg + Fe), or Mg#, between 92.0 and 93.7. Orthopyroxene has very low Al₂O₃ and CaO contents (0.024–1.639 and 0.062–0.275 wt%, respectively). Spinel has 100 × Cr/(Cr + Al), or Cr#, between 46.98 and 95.67. Clinopyroxene is absent. The osmium isotopic composition of olivine and spinel mineral separates shows a considerable span of ¹⁸⁷Os/¹⁸⁸Os values. The most unradiogenic ¹⁸⁷Os/¹⁸⁸Os value of 0.1046 corresponds to a Re-depletion age of ca. 3.3 Gy, while the most radiogenic value of 0.1336 is higher than present-day chondrite. The Os isotopic composition of the xenoliths is consistent with their origin as restites from a melt extraction event in the Archaean, followed by one or more subsequent metasomatic event(s). The high Cr# in spinel and low modal pyroxene of the Ubekendt Ejland xenoliths are similar to values of some highly depleted mantle peridotites from arc settings. However, highly depleted, arc-related peridotites have higher Cr# in spinel for a given proportion of modal olivine, compared to cratonic xenolith suites from Greenland, which instead form coherent trends with abyssal peridotites, dredged from modern mid-ocean ridges. This suggests that depleted cratonic harzburgites and dunites from shallow lithospheric mantle represent the residue from dry melting in the Archaean.     

Talking whilst walking: a geographical archaeology of knowledge

This paper explores how understandings of the knowledge and lives of individuals can be gained through making geographical context more explicit within qualitative research methods. The paper will focus on 'conversations in place'. More particularly, it will suggest that conversations held whilst walking through a place have the potential to generate a collage of collaborative knowledge. Drawing on the work of Casey, the paper builds upon the notion of the 'constitutive co-ingredience' of place and human identity, and, through using documentary and empirical examples, will argue that 'talking whilst walking' can harness place as an active trigger to prompt knowledge recollection and production.     

Time-stilled space-slowed: how boredom matters

This paper aims to fold the increased attention to issues of materiality in social and cultural geography into the more recent attunement to questions of affect. The vehicle for this aim is a discussion of the complex ways in which boredom, and bodies bored, compose time–space. Somewhat surprisingly, and in stark contrast to its experiential ubiquity, boredom has rarely been discussed within the social sciences. The paper therefore performs a geography of how boredom matters by way of a series of examples of the taking place of boredom drawn from research on music and everyday life. Rather than discuss boredom through the critical concepts that underpin the thesis of disenchantment, such as alienation or anomie, I argue that boredom takes place as a suspension of a body's capacities to affect and be affected forged through an incapacity in habit. Through this discussion I argue that the ‘new materialisms' that increasingly populate social and cultural geography struggle to discern the affectivity of profane social-life and, importantly, cannot conceive of the risk of depletion that boredom, via its connection to meaninglessness and indifference, exemplifies. However, attuning to the movement-from that always accompanies boredom discloses the immanent presence of intensities that on-go even as boredom stills and slows time–space. Based on the ambiguity of boredom that results, the conclusion draws on the ‘not-yet' materialism of Ernst Bloch [The Principle of Hope (vols. 1–3) (N. Plaice, S. Plaice, P. Knight, Trans.), Blackwell, Oxford, 1986] to disclose an image of process-matter that draws on Bennett's [The Enchantment of Modern Life. Attachments, Crossings and Ethics, Princeton University Press, Princeton and Oxford, 2001] concept of an ‘enchanted materialism' but retains a sense of process as incorporating both plentitude and depletion. The basis to this form of affective materialism is the event of hope.     

Influence of salinity on atrazine toxicity to a Chesapeake Bay copepod (Eurytemora affinis) and fish (Cyprinodon variegatus)

The objective of this study was to determine the influence of a range of salinities (5%., 15%., and 25%.) on the acute toxicity of atrazine to nauplii of the copepodEurytemora affinis and larvae of the sheepshead minnow,Cyprinodon variegatus. Ninety-six-hour LC50 values for the copepod were 0.5 mg 1^?1, 2.6 mg 1^?1, and 13.2 mg 1^?1 at salimities of 5%., 15%. and 25%. respectively. A comparison of LC50 values between adjacent salinities showed a statistical difference between 15%. and 25%. but not between 5%. and 15%.. Atrazine was more toxic toE. affinis at the lowest salinity. The 96-h LC50s for the sheepshead minnow were 16.2 mg 1^?1, 2.3 mg 1^?1, and 2.0 mg 1^?1 at salinities of 5%., 15%., and 25%., respectively. There was a statistical difference between LC50 values at 5%. and 15%. but not between 15%. and 25%.. In contrast toE. affinis results, atrazine was more toxic toC. variegatus at the highest salinity. The toxicity data from these species suggest that development of estuarine water quality criteria is warranted.     

Disaster management and the military

The increasing range and occurrence of disasters has generated global concern. At the same time, the end of the Cold War has resulted in a re-orientation of military thinking. As the role of the military is being redefined, one focus has been upon the potential contribution of disaster relief. In this paper, the complexity of disasters is examined and then the military capability is discussed and illustrated.