scholarly journals Sulfur isotope evidence of geochemical zonation of the Samoan mantle plume

2021 ◽  
Author(s):  
James Dottin ◽  
Jabrane Labidi ◽  
Matthew Jackson ◽  
James Farquhar
Keyword(s):  
Mantle Plume ◽  
Sulfur Isotope ◽  
Full Range ◽  
Primitive Mantle ◽  
Isotope Evidence ◽  
The Individual ◽  
Different Origins ◽  
Prior Hypothesis ◽  
Sulfur Isotope Data ◽  
S Isotope

<p>The radiogenic Pb isotope compositions of basalts from the Samoan hotspot suggest various mantle endmembers contribute compositionally distinct material to lavas erupted at different islands [1]. Basalts from the Samoan islands sample contributions from all of the classical mantle endmembers, including extreme EM II and high <sup>3</sup>He/<sup>4</sup>He components, as well as dilute contributions from the HIMU, EM I, and DM components. Here, we present multiple sulfur isotope data on sulfide extracted from subaerial and submarine whole rocks associated with several Samoan volcanoes—Malumalu, Malutut, Upolu, Savaii, and Tutuila—that sample the full range of geochemical heterogeneity at Samoa and allow for an assessment of the S-isotope compositions associated with the different mantle components sampled by the Samoan hotspot. We observe variable S concentrations (10-1000 ppm) and δ<sup>34</sup>S values (-0.29‰ to +4.84‰ ± 0.3, 2σ). The variable S concentrations likely reflect weathering, sulfide segregation and degassing processes. The range in δ<sup>34</sup>S reflects mixing between the primitive mantle and recycled components, and isotope fractionations associated with degassing. The majority of samples reveal Δ<sup>33</sup>S within uncertainty of Δ<sup>33</sup>S=0 ‰ ± 0.008, suggesting Δ<sup>33</sup>S is relatively well mixed within the Samoan mantle plume. Important exceptions to this observation include: (1) a negative Δ<sup>33</sup>S (-0.018‰ ±0.008, 2σ) from a rejuvenated basalt on Upolu island (associated with a diluted EM I component) and (2) a previously documented small (but resolvable) Δ<sup>33</sup>S values (up to +0.027±0.016) associated with the Vai Trend (associated with a diluted HIMU component) [2]. The variability we observed in Δ<sup>33</sup>S is interpreted to reflect contributions of sulfur of different origins and likely multiple crustal protoliths. Δ<sup>36</sup>S vs. Δ<sup>33</sup>S relationships suggest all recycled S is of post-Archean origin. The heterogeneous S isotope values and distinct isotopic compositions associated with the various compositional trends confirms a prior hypothesis; unique crustal materials are heterogeneously delivered to the Samoan mantle plume and compositionally influence the individual groups of islands.</p><p>[1] Jackson et al. (2014), <em>Nature; </em>[2] Dottin et al. (2020), <em>EPSL</em></p>

scholarly journals Sulfur isotope evidence for a geochemical zonation of the Samoan mantle plume

2021 ◽  
Author(s):  
James W. Dottin ◽  
Jabrane Labidi ◽  
Matthew G. Jackson ◽  
James Farquhar
Keyword(s):  
Mantle Plume ◽  
Sulfur Isotope ◽  
Isotope Evidence

Employee Surveys and Sensing

2020 ◽  
Keyword(s):  
Organizational Performance ◽  
Employee Engagement ◽  
Computational Linguistics ◽  
Full Range ◽  
Organization Culture ◽  
Employee Survey ◽  
Passive Data ◽  
Individual Contributions ◽  
Action Taking ◽  
The Individual

This volume comprises 27 chapters focused on the design and execution of employee survey programs. These chapters reflect the latest advances in technology and analytics and a pervasive emphasis on driving organizational performance and effectiveness. The individual chapters represent the full range of survey-related topics, including design, administration, analysis, feedback, and action-taking. The latest methodological trends and capabilities are discussed including computational linguistics, applications of artificial intelligence, and the use of qualitative methods such as focus groups. Extending beyond traditional employee surveys, contributions include the role of passive data collection as an alternative or supplement in a comprehensive employee listening system. Unique contextual factors are discussed including the use of surveys in a unionized environment. Individual contributions also reflect increasing stakeholder concerns for the protection of privacy among other ethical considerations. Finally, significant clarifications to the literature are provided on the use of surveys for measuring organization culture, strategic climate, and employee engagement.

Coupled Fe and S isotope evidence for Archean microbial Fe(III) and sulfate reduction

Geology ◽  
2006 ◽  
Vol 34 (3) ◽  
pp. 153 ◽  
Author(s):  
Corey Archer ◽  
Derek Vance
Keyword(s):  
Sulfate Reduction ◽  
Isotope Evidence ◽  
S Isotope

scholarly journals Facing the Future: A Blueprint for a Resilient and Equitable Society: Connecting the Functional Building Blocks

2018 ◽  
Vol 2 (1) ◽  
pp. 1-37
Author(s):  
F. Bocken ◽  
E. Brennan ◽  
N. Claessens ◽  
D. Claeys ◽  
S. Debeaussaert ◽  
...  
Keyword(s):  
Political Representation ◽  
Full Range ◽  
Building Blocks ◽  
Bank Loans ◽  
Ageing Population ◽  
Individual Level ◽  
The Future ◽  
Range Of Functions ◽  
The Individual ◽  
The Unemployed

Abstract Contemporary society is plagued by a number of issues and inconsistencies on both an environmental and a socio-economic level. Reliance on bank loans forces debtors to seek means to repay their debts, thus facilitating the current boundless economic growth in which long-term, environmental considerations typically come second. On the individual level, since virtually nothing is free, everyone has to ensure his or her own livelihood, mostly in the form of wage labour. For fear of poverty, the unemployed must adjust to the needs of the job market and risk not being able to fully explore their potential. Other socio-economic groups also face stigmatisation, and inequality is rampant as a result of the pervasive market-based pricing mechanisms. In view of these issues, it seems unjustified to accept these terms and conditions in the future, especially since the West has to cater to its ageing population and the ensuing pressure this will exert on welfare systems. Therefore, as a transdisciplinary team assisted by various experts and armed with insights from a wide <target target-type="page-num" id="p-2"/>variety of sources, we propose an alternative model of society based on the values of fairness, inclusion and transparency, with the goal of developing a representative systems map for a future, resilient and equitable society. The exact workings of this society are captured by several building blocks, which together endeavour to cover the full range of functions and responsibilities associated with society today, and jointly promote democratisation while guaranteeing equal political representation for all members of society.

scholarly journals Individual differences in the perception of probability

2021 ◽  
Vol 17 (4) ◽  
pp. e1008871
Author(s):  
Mel W. Khaw ◽  
Luminita Stevens ◽  
Michael Woodford
Keyword(s):  
Extreme Values ◽  
Full Range ◽  
Response Speed ◽  
Probability Estimation ◽  
Behavioral Differences ◽  
Extensive Experience ◽  
Individual Level ◽  
Pooled Data ◽  
The Rich ◽  
The Individual

In recent studies of humans estimating non-stationary probabilities, estimates appear to be unbiased on average, across the full range of probability values to be estimated. This finding is surprising given that experiments measuring probability estimation in other contexts have often identified conservatism: individuals tend to overestimate low probability events and underestimate high probability events. In other contexts, repulsive biases have also been documented, with individuals producing judgments that tend toward extreme values instead. Using extensive data from a probability estimation task that produces unbiased performance on average, we find substantial biases at the individual level; we document the coexistence of both conservative and repulsive biases in the same experimental context. Individual biases persist despite extensive experience with the task, and are also correlated with other behavioral differences, such as individual variation in response speed and adjustment rates. We conclude that the rich computational demands of our task give rise to a variety of behavioral patterns, and that the apparent unbiasedness of the pooled data is an artifact of the aggregation of heterogeneous biases.

On the volcanic architecture, petrology and geodynamic setting of the 3.48 Ga Barberton komatiite suite, South Africa

2021 ◽  
Author(s):  
E.G. Grosch ◽  
J. Slama
Keyword(s):  
South Africa ◽  
Mantle Plume ◽  
Source Region ◽  
Crustal Contamination ◽  
Primitive Mantle ◽  
Geochemical Data ◽  
Geodynamic Setting ◽  
Crustal Material ◽  
Type Section ◽  
Formation Type

Abstract This study presents new field and petrological observations combined with geochemical data on a range of komatiitic to tholeiitic volcanic rocks from the ca. 3.48 Ga mid-lower Komati Formation type-section of the Barberton Greenstone Belt, South Africa. A range of mafic-ultramafic rocks is identified across a 1.44 km profile, leading to the proposition of a new preliminary volcanic architecture for the mid-lower Komati Formation type-section. Major, trace and rare earth element (REE) data in conjunction with Lu-Hf isotopic constraints indicate that the tholeiites, newly recognized high-magnesium basalts, basaltic komatiites and komatiites in the volcanic sequence have a primitive mantle signature with no geochemical affinity to Archaean or modern-day supra-subduction zone boninites. The whole rock initial εHf values of spinifex and massive komatiite flows in the lowermost part of the Komati type-section are negative, ranging between -1.9 and -3.1, whereas the second overlying spinifex and massive flow unit records positive initial εHf values between +0.5 and +4.7. A new geodynamic model involving crustal contamination of the mafic-ultramafic lavas is proposed for the Barberton mid-lower Komati Formation type-section, involving mantle plume-crust interaction. The new observations and data indicate that the komatiites erupted as a result of a mantle plume from a hot (&gt;1 600oC) mid-Archaean mantle, in which the earliest volcanic flows were variably affected by crustal contamination during their ascent and eruption. The possibility of incorporation of lower crustal material and/or recycled crust residing in the mantle source region cannot be excluded. This indicates that modern-style plate tectonic processes, such as subduction, may not have been a requirement for the formation of the 3.48 Ga Barberton komatiite suite, with implications for the hydration state, geodynamic processes and secular thermal evolution of the Archaean mantle.

Sign in / Sign up

Export Citation Format

Share Document