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Walvis Ridge, a time-transgressive series of ridges, oceanic plateau, seamounts, guyots, and two active volcanic islands extending SW from the coast of Namibia, records the evolution of the Tristan-Gough-Walvis Ridge (TGW) hotspot and the opening of the South Atlantic since ~135 Ma. However, much of our current understanding of the interplay between geodynamic cycles, tectonism, and mantle plume generation along the TGW hotspot track is based upon a limited number of dredged rock samples. Here, we present preliminary whole rock major and trace element geochemistry and shipboard physical properties data from Site U1578, located on a Center track guyot in the Guyot Province. The 302 m of igneous section recovered from Site U1578 provides an extraordinary, > 1 Myr record of plume magmatism, submarine volcanism, and geochemical evolution. The chemical stratigraphy of core from Site U1578 provides important new perspectives on submarine volcanism, magma flux, and the transition between continental tholeiitic basalts of the Etendeka flood basalt province and alkaline lavas of the Guyot Province. Core from U1578 records the longest sequence of pillow, sheet, and massive lava flows in the TGW system. Eleven (of 12 total) lithologic flow units record shifts in major and trace element geochemistry and episodic cycles of recharge and fractional crystallization. Preliminary XRF and ICP-MS analyses indicate a dominantly pyroxenite source and document the shift between high TiO2 (>3.5 wt. %) to low TiO2 (<3.5 wt. %) alkaline basalts. Site U1578 core samples from the Guyot Province have lower Nb/Y and Zr/Nb compared to Walvis Ridge sites drilled closer to the African continent (Frio Ridge at Site U1575 and Valdivia Bank at Sites U1576 and U1577), coincident with a transition from plume-ridge interaction to intraplate magmatism with time. This shift resulted in a thicker lithospheric lid and thus deeper and lower degrees of melting, preferentially sampling the enriched plume component. Additionally, shipboard natural gamma radiation (NGR) and magnetic susceptibility (MS) measurements correlate well with observed lithologic characteristics and new ICP-MS and XRF analyses. A 100 m zone of high NGR values neatly overlaps high K2O, and olivine cumulate layers correlate to higher MS and higher concentrations of Cr and Ni. 

Abstract The past ∼200 million years of Earth's geomagnetic field behavior have been recorded within oceanic basalts, many of which are only accessible via scientific ocean drilling. Obtaining the best possible paleomagnetic measurements from such valuable samples requires an a priori understanding of their magnetic mineralogies when choosing the most appropriate protocol for stepwise demagnetization experiments (either alternating field or thermal). Here, we present a quick, and non‐destructive method that utilizes the amplitude‐dependence of magnetic susceptibility to screen submarine basalts prior to choosing a demagnetization protocol, whenever conducting a pilot study or other detailed rock‐magnetic characterization is not possible. We demonstrate this method using samples acquired during International Ocean Discovery Program Expedition 391. Our approach is rooted in the observation that amplitude‐dependent magnetic susceptibility is observed in basalt samples whose dominant magnetic carrier is multidomain titanomagnetite (∼TM_60–65, (Ti_0.60–0.65Fe_0.35–0.40)Fe₂O₄). Samples with low Ti contents within titanomagnetite or samples that have experienced a high degree of oxidative weathering do not display appreciable amplitude dependence. Due to their low Curie temperatures, basalts that possess amplitude‐dependence should ideally be demagnetized either using alternating fields or via finely‐spaced thermal demagnetization heating steps below 300°C. Our screening method can enhance the success rate of paleomagnetic studies of oceanic basalt samples. 

Abstract Young mafic lavas from the East African Western Rift record melting of subcontinental lithospheric mantle that was metasomatically modified by multiple tectonic events. We report new isotope data from monogenetic cinder cones near Bufumbira, Uganda, in the Virunga Volcanic Field:⁸⁷Sr/⁸⁶Sr = 0.7059–0.7079,ε_Nd = −6.5 to −1.3,ε_Hf = −6.3 to +0.9,²⁰⁸Pb/²⁰⁴Pb = 40.1–40.7,²⁰⁷Pb/²⁰⁴Pb = 15.68–15.75, and²⁰⁶Pb/²⁰⁴Pb = 19.27–19.45. Olivine phenocrysts from the Bufumbira lavas have³He/⁴He = 6.0–7.4R_A. The isotopic data, in conjunction with major and trace element systematics, indicate that primitive Bufumbira magmas are derived from two different metasomatized lithospheric source domains. Melts generated by lower degrees of melting record greater contributions from ∼1 to 2 Ga isotopically enriched garnet‐amphibole‐phlogopite pyroxenite veins within the lithosphere. As melting progresses, these vein melts become increasingly diluted by melts that originate near the lithosphere/asthenosphere boundary, shifting the isotopic compositions toward the common lithospheric mantle (CLM) proposed by Furman and Graham (1999,https://doi.org/10.1016/s0024-4937(99)00031-6). This ∼450–500 Ma source domain appears to underlie all Western Rift volcanic provinces and is characterized by⁸⁷Sr/⁸⁶Sr ∼ 0.705,ε_Nd∼ 0,ε_Hf∼ +1 to +3,²⁰⁶Pb/²⁰⁴Pb ∼ 19.0–19.2,²⁰⁸Pb/²⁰⁴Pb ∼ 39.7, and³He/⁴He ∼ 7R_A. Basal portions of the dense subcontinental lithospheric mantle may become gravitationally unstable and founder into underlying warmer asthenosphere, exposing surfaces where melting of locally heterogeneous veins produces small‐volume, alkaline mafic melts. Mafic lavas from all Western Rift volcanic provinces record mixing between the CLM and locally variable metasomatized source domains, suggesting this style of melt generation is fundamental to the development of magma‐poor rifts. 

This Research Full Paper presents a qualitative interview study on the effectiveness of a computing identity development listserv. The demand for diverse computing careers increases, yet African Americans continue to participate and succeed in computing fields proportionately less than their White and Asian counterparts. An individual’s computing identity can influence their performance and willingness to participate. The African American PhDs in Computer Science Listserv is an email listserv created to increase and maintain members’ sense of belonging, self-efficacy, and resilience in computing. Semistructured interviews of graduate student, faculty, and industry professional members were conducted to investigate how effective the listserv was at increasing and maintaining computing identity. Findings include decision making processes for joining, duration and dosage of interaction members partake, maintenance of computing resilience, members’ self-reflection, willingness to seek help, and attitudes towards computing. Recommendations were made about the listserv and if other African Americans in computing should join. Findings can be used to develop new approaches to supporting the computing identities of underrepresented groups. This paper is in conjunction with other papers in an extended case study on resilient identity development in African American computer scientists. 

This Research Full Paper presents a qualitative interview and descriptive study on computing resilient identity development of African Americans who have earned a Ph.D. in a computing field. Low sense of belonging and self-efficacy contributes to low participation and performance of African Americans have lower participation and performance in computing as compared to their White and Asian counterparts. Computing identity including sense of belonging and self-efficacy contributes to this deficit. To increase African American successful representation in computing, resilience is explored to identify the support systems, challenges, and coping processes of African Americans who have earned a Ph.D. in computing. Indepth, semi-structured interviews of African American post-docs, faculty, and industry researchers in computing fields were implemented. Interviews were audio recorded and transcribed. Transcriptions were analyzed with a hybrid inductive-deductive qualitative content analysis. Surveys were employed to document participants’ work resilience and personality to supplement the qualitative data. Results include the resilient identity development of participants by reciting background information, challenges and support systems in their respective employment, and how they react to such stressors and supports, and the productive they are while persevering. Findings from this work can be used to improve academia and industry conditions for African American professionals and to identify resources that were suggested to be pivotal in participants’ resilient identity development within the computing field. This paper is in conjunction with other papers in an extended case study on resilient identity development in African American computer scientists.