ALBERT

Description: Die FS SONNE-Reise SO-232 ist Teil des multidisziplinären Projekts SLIP (Suspec-ted Large Igneous Province), dass vom das vom Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (AWI) und vom Helmholtz-Zentrum für Ozeanforschung Kiel (GEOMAR) gemeinsam durchgeführt wird. Während SO-232 wurden reflexionsseismische Vermessungen (AWI), bathymetrische Kartierungen (AWI, GEOMAR) und Hartgesteinsbeprobungen (GEOMAR) am Mozambiquerücken im Südwest-Indik durchgeführt (Abb. 1). Damit soll ein besseres Verständnis der Entstehung des Mozambiquerückens im Verlauf der Öffnung des Südozeans sowie des Zusammenhangs zwischen vulkanisch-tektonischen Aktivitäten und sich verän-dernden Tiefseeströmungsmustern erreicht werden. Dieser Beitrag befasst sich mit den geologischen Arbeiten von SO-232, die Geophysik wird von Fischer und Uen-zelmann-Neben, AWI vorgestellt. Der Mozambiquerücken ist ein submarines Plateau, dass nach dem Aufbruch des Superkontinents Gondwana und der Öffnung des Südozeans vor möglicherweise ca. 120 - 140 Mill. Jahren entstand (König und Jokat 2010). Allerdings werden drei völlig unterschiedliche Modelle für seine Bildung diskutiert. Demnach ist der Mozambique-rücken entweder (1) ein kontinentales Fragment, das nach dem Aufbruch von Gondwana in der Ozeankruste verblieben ist, oder (2) eine eigenständige Mikroplatte oder (3) eine ozeanischen Flutbasaltprovinz, die durch großvolumigen Magmatismus entstand. Ein Ziel von SO-232 ist es, Alter und Zusammensetzung der magmati-schen Gesteine des Mozambiquerückens zu charakterisieren, um damit Natur, Ur-sprung und zeitliche und räumliche Entwicklung des Mozambiquerückens zu rekon-struieren. Dies ist z.B. wichtig für die Rekonstruktion der globalen Plattentektonik und für das Verständnis magmatischer Großereignisse. Auch hat die Bildung ozeanischer Plateaus Auswirkungen auf die Ozeanzirkulation und damit auf das Klima. Weiterhin soll die Zusammensetzung der Mantelquelle unter dem Mozambiquerü-cken charakterisiert werden, um neue Erkenntnisse über den Ursprung der "Dupal-Anomalie" (Hart 1984) zu gewinnen. Die Dupal-Anomalie, die nach den Geochemi-kern Dupré und Allègre benannt ist, ist ein bis zu 60° breiter Bereich, der sich in der südlichen Hemisphäre um die Erde erstreckt und geochemisch stark angereicherte Signaturen in Intraplattenvulkaniten aufweist (radiogene Sr- und unradiogene Nd-Isotopenverhältnisse sowie hohes ∆7/4 und ∆8/4). Der Mozambiquerücken befindet sich im Gebiet dieser Anomalie, deren Ursprung kontrovers diskutiert wird. Eine mögliche Erklärung könnten Fragmente unterer kontinentaler Kruste sein (Escrig et al. 2004, Hanan et al. 2004), die infolge des Gondwana-Aufbruchs durch Delaminati-on in den oberen Mantel gelangten oder sich innerhalb der ozeanischen Lithosphäre befinden. Eventuelle kontinentale Teile des Mozambiquerückens könnten ein solches Fragment sein. Alternativ werden für die Dupal-Anomalie tiefe Mantelquellen disku-tiert. Neue Erkenntnisse über diese globale Anomalie in der Zusammensetzung des Erdmantels sind u.a. grundlegend für ein besseres Verständnis von Mantelprozes-sen, die die Funktionsweise des "Systems Erde" maßgeblich beeinflussen. Während SO-232 wurden 59 Dredgezüge durchgeführt, von denen 35 massive magmatische Gesteine und 16 Vulkaniklastika erbrachten (Abb. 1). Damit wurde das magmatische Basement des Mozambiquerückens erstmals erfolgreich umfassend beprobt. Weiterhin lieferten die Dredgen Sedimente, Mangankrusten und Benthos-fauna, die Kooperationspartnern zur Verfügung gestellt werden. Nahezu alle magma-tischen Proben sind vulkanisch oder subvulkanisch, was die Hypothese stützt, dass der Mozambiquerücken vulkanischen Ursprungs ist und eine Flutbasaltprovinz reprä-sentieren könnte. Nur ein Block am Nordostrand des Rückens hat eindeutig eine kontinentale Affinität und ist wahrscheinlich ein Splitter kontinentaler Kruste. Bemer-kenswerterweise befinden sich nahezu überall auf dem Rücken kleine Vulkankegel, die sicherlich nicht 〉100 Mill. Jahre Sedimentation und Tektonik überstehen können und daher auf eine Reaktivierung des Vulkanismus nach Bildung des eigentlichen Rückens hindeuten. Die magmatischen Proben werden in den kommenden ca. 2 Jahren umfassend geo-chemisch analysiert (u.a. Haupt- und Spurenelemente, Sr-Nd-Pb-Hf-Isotopenverhältnisse). Petrographie und Hauptelementzusammensetzung werden genutzt, um die Gesteine zu klassifizieren, auf Ihre Eignung für die weitere Analytik zu überprüfen und die Magmenentwicklung zu rekonstruieren. Spurenelementdaten dienen u.a. als Indikatoren für Aufschmelzgrade bei der Magmenproduktion und können Hinweise auf eine mögliche Krustenkontamination sowie die chemische Zu-sammensetzung der Magmenquelle liefern. Die Verhältnisse radiogener Isotopen geben Informationen über die Entwicklung der Magmenquellen des Mozambiquerü-ckens. Weiterhin soll anhand von 40Ar/39Ar-Altersdatierungen festgestellt werden, wann der Rücken entstand, wie lange der Magmatismus andauerte und ob er durch ein einzelnes Großereignis oder in mehreren Phasen vulkanischer Aktivität entstand. Einen ersten Satz von Hauptelementdaten der SO-232-Proben haben wir kurz vor Einreichen dieser Zusammenfassung erhalten. Mit einer Ausnahme sind alle bisher analysierten Proben Basalte, Trachybasalte und basaltische Andesite mit SiO2-Gehalten zwischen 47 und 53 Gew. % (Abb. 2). Die Entwicklung dieser Laven wurde somit kaum durch krustale Prozesse beeinflusst und die weitere Analytik wird es uns daher erlauben, ihre Mantelquellen zu identifizieren. Wir erwarten, auf dem Sonne-Statusseminar weitere Daten präsentieren zu können, die u.a. erste Informationen über Schmelztiefen und Aufschmelzgrad sowie Mantelquellen liefern werden.

Description: The Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous (König and Jokat, 2010). The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin (Gohl et al., 2011). High-resolution seismic reflection data gathered during Sonne expedition SO232 reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intrabasement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic for eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge (Uenzelmann-Neben et al., 1999; Sager et al., 2013; Pietsch and Uenzelmann-Neben, 2015). We observe evidence for widespread post-sedimentary magmatic activity that we suggest to correlate with a Neogene southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ~131 and ~125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.

Description: The Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous. The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin. High-resolution seismic reflection data reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intra-basement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic of eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge. We observe evidence for widespread post-sedimentary magmatic activity that we correlate with a southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ~131 Ma and ~125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.

Description: The SO-232 cruise took place in April-May 2014 at the Mozambique Ridge, a presumably 120-140 Ma-old submarine volcanic plateau located in the SW Indian Ocean. The major goal of this multi-disciplinary project is to better understand the formation of the Mozambique Ridge, in relation to the opening of the South Atlantic Ocean and the break-up of the Gondwana supercontinent. Three different models have been proposed for the origin for this plateau: 1) a continental fragment formed during the break-up of Gondwana, 2) an independent microplate, or 3) an oceanic Large Igneous Province (LIP). Our studies aim to characterize age and geochemical composition of magmatic sam-ples in order to reconstruct the nature, origin, and spatial and temporal evolution of the plateau. The rock sampling mainly yielded basaltic lava (SiO2 = 47-52 wt. %) indicating a volcanic origin of the plateau. Bathymetry data show small cones scattered on the plateau, which represent the latest stage of volcanism. The samples form tight correlations with fluid-immobile trace elements ratios such as Nb/Yb and Th/Yb. Most of the samples have relatively flat REE pattern. A few, however, show steeper Heavy REE patterns, indicating a more enriched source or lower degrees of mantle melting. The REE patterns are consistent with a LIP origin of the plateau basement and a less voluminous, younger phase of volcanism. Sr and Nd isotope ratios extend from present-day South Indian mid-ocean-ridge basalts (MORB) and ocean island basalts (OIB) to slightly more enriched values. Prelim-inary age correction improves the Sr-Nd isotope correlation, and thus superimposed alteration effects can be excluded. On the uragonenic Pb isotope diagram, the samples extend to higher Δ7/4 than the South West Indian array and overlap the South Atlantic MORB field. This observation implies that initial opening of the SW-Indian Ocean was rather influenced by South Atlantic than Indian MORB mantle.

Description: The Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous (König and Jokat, 2010). The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin (Gohl et al., 2011). High-resolution seismic reflection data gathered during Sonne expedition SO232 reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intrabasement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic for eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge (Uenzelmann-Neben et al., 1999; Sager et al., 2013; Pietsch and Uenzelmann-Neben, 2015). We observe evidence for widespread post-sedimentary magmatic activity that we suggest to correlate with a Neogene southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ~131 and ~125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.

Description: The Mozambique Ridge (MOZR) is one of several bathymetric highs formed in the South African gateway shortly after the breakup of the supercontinent Gondwana. Two major models have been proposed for its formation - volcanic plateau and continental raft. In order to gain new insights into the genesis of the Mozambique Ridge, R/V SONNE cruise SO232 carried out bathymetric mapping, seismic reflection studies and comprehensive rock sampling of the igneous plateau basement. In this study, geochemical data are presented for 51 dredged samples, confirming the volcanic origin of at least the upper (exposed) part of the plateau. The samples have DUPAL-like geochemical compositions with high initial 87Sr/86Sr (0.7024–0.7050), low initial 143Nd/144Nd (0.5123–0.5128) and low initial 176Hf/177Hf (0.2827–0.2831), and elevated initial 207Pb/204Pb and 208Pb/204Pb at a given 206Pb/204Pb (Δ7/4 = 2–16; Δ8/4 = 13–167). The geochemistry, however, is not consistent with exclusive derivation from an Indian MORB-type mantle source and requires a large contribution from at least two components. Ratios of fluid-immobile incompatible elements suggest the addition of an OIB-type mantle to the ambient upper mantle. The MOZR shares similar isotopic compositions similar to mixtures of sub-continental lithospheric mantle end members but also to long-lived, mantle-plume-related volcanic structures such as the Walvis Ridge, Discovery Seamounts and Shona hotspot track in the South Atlantic Ocean, which have been proposed to ascend from the African Large Low Shear Velocity Province (LLSVP), a possible source for DUPAL-type mantle located at the core-mantle boundary. Interestingly, the MOZR also overlaps compositionally with the nearby Karoo-Vestfjella Continental Flood Basalt province after filtering for the effect of interaction with the continental lithosphere. This geochemical similarity suggests that both volcanic provinces may be derived from a common deep source. Since a continuous hotspot track connecting the Karoo with the MOZR has not been found, there is some question about derivation of both provinces from the same plume. In conclusion, two possible models arise: (1) formation by a second mantle upwelling (blob or mantle plume), possibly reflecting a pulsating plume, or (2) melting of subcontinental lithospheric material transferred by channelized flow to the mid-ocean ridge shortly after continental break-up. Based on geological, geophysical and geochemical observations from this study and recent published literature, the mantle-plume model is favored.

Description: The Mozambique Ridge (120-140 Ma old) is a submarine plateau located in the southwest Indian Ocean. The relationship between plateau formation and the break-up of the Gondwana supercontinent is still unclear. Different models for the origin of this plateau include: 1) a continental fragment split off of Africa or Antarctica during Gondwana break-up and 2) an oceanic Large Igneous Province (LIP) formed by a mantle plume involved in Gondwana break-up. On the R/V SONNE (cruise SO232), we carried out bathymetric mapping, seismic reflection studies and rock sampling of the plateau basement, which confirmed the volcanic nature of at least the upper parts of the plateau. By reconstructing the spatial and temporal evolution in geochemistry of volcanic samples, we hope to gain new insights into the origin of the plateau. The recovered samples are mainly basaltic (SiO2 = 47-52 wt. %). On the Nb/Yb versus Th/Yb diagram, the samples overlap the field for enriched-mid-ocean-ridge basalts (EMORB) and extend towards the field for ocean island basalts (OIB). Most of the samples have relatively flat REE patterns, similar to EMORB or LIP type lavas. Initial Sr-Nd-Hf isotope ratios form tight correlations, excluding late alteration effects. The samples overlap and extend to slightly more radiogenic values than age-corrected SW Indian and South Atlantic MORB and OIB, indicating a two-component mixing between depleted (NMORB source) and enriched (OIB-type) mantle. Similar to some early Kerguelen plateau basalts, some of our samples have low Nd isotope and (Nb/La)n (〈 1) ratios suggesting involvement of continental lithosphere and/or lower crust. On the 206Pb/204Pb versus 207Pb/204Pb isotope diagram, the samples extend to higher Δ7/4 than the South West Indian array, overlapping with Kerguelen lavas. Bathymetric data show numerous small cones scattered on the plateau, which are thought to represent a reactivation of volcanism after formation of the plateau basement. Moreover, seismic refraction data show evidence for a thick oceanic lower crust. Together with our new geochemical data, it favors a LIP origin for the Mozambique Ridge.

Description: The Sino-Tibetan language family is one of the world’s largest and most prominent families, spoken by nearly 1.4 billion people. Despite the importance of the Sino-Tibetan languages, their prehistory remains controversial, with ongoing debate about when and where they originated. To shed light on this debate we develop a database of comparative linguistic data, and apply the linguistic comparative method to identify sound correspondences and establish cognates. We then use phylogenetic methods to infer the relationships among these languages and estimate the age of their origin and homeland. Our findings point to Sino-Tibetan originating with north Chinese millet farmers around 7200 B.P. and suggest a link to the late Cishan and the early Yangshao cultures.

Description: Materials, Vol. 11, Pages 1224: Anisotropy of Transport Properties Correlated to Grain Boundary Density and Quantified Texture in Thick Oriented Ca3Co4O9 Ceramics Materials doi: 10.3390/ma11071224 Authors: Driss Kenfaui Moussa Gomina Jacques Guillaume Noudem Daniel Chateigner The misfit-layered Ca3Co4O9 oxide is being seen as a potential thermoelectric (TE) candidate for high-temperature power generation in air. Given the very small size and low strength exhibited by single crystals, grain-oriented Ca3Co4O9 ceramics are worth elaborating to capitalize on their anisotropy. However, the usual textured pellets are too thin to probe the TE properties along their principal crystallographic directions. In this paper, we report on the anisotropy of TE properties in the 350–860 K range within thick textured Ca3Co4O9 ceramics fabricated by moderately pressing at 1173 K stacks of pellets primarily textured using spark plasma sintering (SPS), spark plasma texturing (SPT), and hot pressing (HP). The texture was quantitatively assessed, and the influent microstructural parameters were identified, particularly the grain boundary density parallel (GBDc) and perpendicular (GBDab) to the mean c*-axis. We found that the edge-free processing fostered material texturing and (a,b) plane grain growth, thereby dropping GBDab and increasing GBDc. This resulted in a resistivity ρab reduction, leading to a marked enhancement in power factor PFab, which reached 520 μW·m−1·K−2 at 800 K for the HP sample. The anisotropy ρc/ρab was substantially promoted as the texture was reinforced and the GBDc/GBDab ratio increased, with ρc/ρab (HP) > ρc/ρab (SPT) > ρc/ρab (SPS). The Seebeck coefficient S also revealed an anisotropic behavior, with a ratio Sc/Sab >1 for the SPS-processed materials. This behavior was reversed (Sc/Sab <1) for the more textured SPT and HP specimens. It therefore resulted in a PF anisotropy PFc/PFab (HP) < PFc/PFab (SPT) < PFc/PFab (SPS). The PFab/PFc ratio attained 13.6 at 800 K for the thick HP sample, which is the largest ratio recorded thus far on undoped Ca3Co4O9 ceramics.