Elizabeth M. King

A cool early Earth

No known rocks have survived from the first 500 m.y. of Earth history, but studies of single zircons suggest that some continental crust formed as early as 4.4 Ga, 160 m.y. after accretion of the Earth, and that surface temperatures were low enough for liquid water. Surface temperatures are inferred from high d 18 O values of zircons. The range of d 18 O values is constant throughout the Archean (4.4‐2.6 Ga), suggesting uniformity of processes and conditions. The hypothesis of a cool early Earth suggests long intervals of relatively temperate surface conditions from 4.4 to 4.0 Ga that were conducive to liquidwater oceans and possibly life. Meteorite impacts during this period may have been less frequent than previously thought.

Hydrothermal alteration of oxygen isotope ratios in quartz phenocrysts, Kidd Creek mine, Ontario: Magmatic values are preserved in zircon

Zircons from rhyolites hosting the Kidd Creek volcanogenic massive sulfide deposit preserve magmatic oxygen isotope ratios (δ 18 O = 5.4‰ ± 0.3‰, n = 11) that are indistinguishable from average values of other plutonic and volcanic rocks of the Superior Province. Oxygen isotope ratios of petrographically pristine, primary quartz phenocrysts, however, are greatly elevated in δ 18 O and heterogeneous (δ 18 O = 14.2‰ to 16.1‰). Such phenocrysts are not a good monitor of magmatic processes. The presence of healed microcracks in quartz phenocrysts, as seen in cathodoluminescence images, and the variability of quartz oxygen isotope ratios suggest that recrystallization is the process of δ 18 O elevation. In contrast to the variability of quartz, the δ 18 O zircon values do not vary regardless of the degree of magnetic susceptibility. The δ 18 O values of zircon are interpreted to reflect the primitive, magmatic oxygen, consistent with the rhyolite geochemistry, for magmas derived by partial melting of a tholeiitic source. Our data show that the δ 18 O values of quartz and whole rock at Kidd Creek are a good monitor of hydrothermal exchange and are 5‰ higher than the magmatic value that is preserved in zircon due to its refractory nature.

Digital literacies for the disengaged: creating after school contexts to support boys' game‐based literacy skills

Purpose – This paper aims to reviews the structure and format of an after school incubator program that leverages online games for literacy learning, particularly for adolescent males. It also aims to describe its dual function as both quasi‐natural context and design experiment laboratory and to discuss some early findings that illustrate the kinds of literacy practices the authors are beginning to see within their homegrown community to date.Design/methodology/approach – For the past year, the authors have been engaging game‐loving boys in digital and print literacy practices, not by playing matchmaker between them and those game communities that engage in such practices naturally, but by growing such a community of their own. Following the lead of other games‐based educational programs and known characteristics of game‐related indigenous online communities, the design encourages distributed expertise and collective intelligence in place of standardization and peer‐to‐peer learning in the form of modeli...

Empirical determination of oxygen isotope fractionation factors for titanite with respect to Zircon and Quartz

Abstract Measurements of oxygen isotope fractionations between coexisting igneous titanite (Ttn) and zircon (Zrc) have been used to formulate a self-consistent, empirical calibration of equilibrium oxygen isotope partitioning: 1000 ln α( Zrc − Ttn )=1.02×10 6 /( T 2 ) This calibration is based on the average measured Δ(Zrc-Igneous Ttn) = 1.2 ± 0.3‰ (n = 27 rocks) and a closure temperature of titanite to oxygen diffusion of approximately 650°C. The average measured fractionation between zircon and metamorphic titanite is 2.1 ± 0.4‰ (n = 5 rocks). These results show that Δ(Zrc-Ttn) can be used to distinguish igneous vs. metamorphic (or hydrothermal) titanite. The new zircon-titanite fractionation has been combined with published experimental and empirical data to provide a new quartz-titanite fractionation curve: 1000 ln α( Qtz − Ttn )=3.57×10 6 /(T 2 ) This new calibration is consistent with Δ(Qtz-Igneous Ttn) data from coexisting mineral pairs in granitic rocks. Modeling diffusional exchange of oxygen during cooling in a typical granitic rock, using the new calibration, results in the same Δ(Qtz-Igneous Ttn) as measured (4.5 ± 0.43‰, n = 25 rocks). Both measured Δ(Zrc-Igneous Ttn) and Δ(Qtz-Igneous Ttn) differ from fractionations calculated using the semiempirical increment method. The consistency of empirical Δ(Zrc-Igneous Ttn) in a range of geologic environments allows the calculation of a more accurate fractionation factor for titanite.

Not just a dollhouse: what The Sims2 can teach us about women's IT learning

Purpose – The purpose of this paper is to describe how a popular computer game, The Sims2, engages players in computing practices that are foundational to information technology (IT) fluency, and to draw implications for engaging young people, particularly girls and women, in computer‐related learning.Design/methodology/approach – The analysis is framed within a conceptual perspective on learning as a process of acquiring situated understandings through participation in meaningful activity. The paper draws on two years of work with girls developing IT fluency through playing and modding The Sims. It also draws on interviews with adult women who are highly engaged in creating Sims content.Findings – The paper identifies a set of practices inherent in Sims game play that are foundational to IT fluency: managing complex systems; cheating and glitching; tinkering with tools; and making, manipulating, and reasoning with spatial representations.Practical implications – The paper suggests how existing practices ...

Oxygen isotope trends of granitic magmatism in the Great Basin: Location of the Precambrian craton boundary as reflected in zircons

The δ 18 O values of magmas in the Great Basin help to decipher the tectonic assembly of North America and to determine the magmatic source and potentially the composition of the crust at depth. Igneous zircons from Precambrian, Jurassic, Cretaceous, and Tertiary intrusive bodies of the northern Great Basin best preserve the rec ord of magmatic oxygen isotope ratios. The variation of δ 18 O values in zircon with age reconciles previous differences in interpretation based on δ 18 O WR and radiogenic isotope data. The new δ 18 O Zrc data support the results of previous radiogenic isotope studies documenting the increased availability of crustal and sedimentary components to magmas in the Cretaceous during the Sevier orogeny and a return to a larger proportion of mantle-derived components in the Tertiary during Basin and Range extension. In the Great Basin, δ 18 O Zrc values also vary systematically with crustal structure as determined by radiogenic isotope systematics. Plutons emplaced east of the 87 Sr/ 86 Sr i = 0.706 isopleth have higher δ 18 O Zrc values than plutons intruded west of the 0.706 line. However, analyses of δ 18 O values in quartz do not show the bimodal distinction across the 0.706 line owing to subsolidus alteration. On the basis of δ 18 O Zrc , plutons intruding the Walker Lane belt are indistinguishable from other plutons emplaced west of the 0.706 line despite significant tectonic displacement and rotation of the belt. The difference in δ 18 O values across the 0.706 line reflects the involvement of high-δ 18 O Precambrian and Paleozoic sedimentary rocks of the continental margin and Precambrian craton in magmas intruded east of the 0.706 line, whereas magmas west of the 0.706 line are dominated by lower-δ 18 O rocks derived from juvenile volcanic arcs. Crustal boundaries and discontinuities in the Great Basin determined by radiogenic isotope systems agree with discontinuities observed in δ 18 O Zrc values; this agreement indicates that the 0.706 line marks a geochronologic and compositional discontinuity in the basement rocks.

A Cross Case Analysis of Two Out-of-School Programs Based on Virtual Worlds

There is renewed interest in out-of-school programs for informal learning as a way to complement or supplement formal classrooms. Compelling evidence of learning in the context of virtual worlds is emerging, but few empirically detailed comparisons of programs based on such technologies exist. This article presents a crosscase analysis conducted on two out-of-school programs based on virtual environments involving Global Kid’s “I Dig Science” situated in the virtual platform Teen Second Life and Games, Learning & Society Program’s “Casual Learning Lab” based on the massively multiplayer online game World of Warcraft. Ethnographic methods were used for data collection across both in-game and face-to-face contexts at both sites with virtual and face-to-face data collection techniques used in combination. Analysis involved a code set of eleven a priori themes based on the shared goals of each program, resulting in 44 codes total. In this paper, the authors detail contrasts between the two programs in terms of argumentation, problem-solving, information literacy, and workplace skills, highlighting differences between the two programs in terms of their contrasting “locus of intentionality” (designer versus participant) and concluding with a set of “petite generalizations” in the form of design heuristics for future virtual worlds based programs. DOI: 10.4018/jgcms.2012010102 26 International Journal of Gaming and Computer-Mediated Simulations, 4(1), 25-54, January-March 2012 Copyright

Promoting multicultural literacies through game-based embodiment: a case study of counselor education students and the role-playing game Oblivion

Purpose – This study aims to build on Gee’s (2003) earlier question exploring specifically the learning processes associated with broadening cultural empathy and exploring personal bias through gameplay in the role-playing game, Oblivion. Design/methodology/approach – Methodology for this case study (Stake, 1995) was informed by narrative (Reissman, 2001) methods that focused on collecting descriptions of the unique experiences of participants while being engaged in gameplay and their personal reflections synthesizing game-based engagement and course content. “Narrative research offers the possibility of exploring nuances and interrelationships among aspects of experience that the reader might better understand other related situations” (Josselson, p. 239). Our study focused on using narrative research methods to examine embodiment within the fictional world of the game as an experiential participatory-learning experience. Findings – All participants indicated that the most salient learning experiences of...