Geochronology, geochemistry and Nd, Sr and Pb isotopes of syn-orogenic granodiorites and granites (Damara orogen, Namibia) – arc-related plutonism or melting of mafic crustal sources?

Highlights • Geochemical data from high-T granodiorites and granites imply lower crustal amphibolite melting. • New U-Pb zircon ages imply syn-orogenic intrusion • New Sr-Nd-Pb isotope data imply ancient crustal sources and constrain AFC processes Abstract: The Gawib pluton (Damara Belt, Namibia) consists of two main intrusive rock types; magnesian, calc-alkaline, mostly metaluminous hornblende- and titanite-bearing granodiorites and magnesian to ferroan, metaluminous to slightly peraluminous calc-alkaline granites. Uranium-Pb zircon data obtained on the granodiorites gave concordant ages of 548.5 ± 5.6 Ma indicating that the pluton belongs to the early syn-orogenic magmatism in the Damara orogen. Major and trace element variations indicate that fractional crystallization was the major rock-forming mechanism for the granodiorites. In the absence of high-precision geochronological data, the granites may represent more advanced fractionation products of the granodiorites although distinct Ba-Sr-Rb relationships preclude a direct derivation of the granites from the exposed granodiorites. If the granites originated by extensive fractional crystallization from similar granodiorites, they can only be derived from high-Ba, high-Sr, low-Rb granodiorites. Crustal contamination was also important in the petrogenesis of both rock types (granodiorites: ε Nd(init.): -7 to -13; 87Sr/86Sr(init.): 0.708-0.713; granites: ε Nd(init): -14 to -18; 87Sr/86Sr(init.): 0.712-0.726). In contrast to the granodiorites, the granites show more radiogenic 87Sr/86Sr ratios and less radiogenic ε Nd values indicating different contaminants for both rock types. ε Nd vs. MgO relationships imply some genetic link to isotopically unevolved quartz diorites similar to those observed at the Palmental complex. This pluton, however, is located c. 80 km NE from the Gawib pluton and probably cannot be viewed as the direct source of the Gawib granodiorites. If such a relationship is allowed, the granodiorites must be viewed as hybrid rocks containing a juvenile component because they were derived from unevolved quartz diorites by fractional crystallization. In addition, AFC processe have also played a role implying that the granodiorites contain also a reprocessed crustal component. Alternatively, comparison with experimentally derived melts imply that the granodiorites are generated by dehydration melting of a mafic, amphibole-bearing lower crustal source. Chemical parameters of the granodiorites compared to experimental results indicate high temperatures of c. 1040 °C. Zirconium saturation temperatures obtained on the most primitive samples gave c. 830 °C whereas apatite saturation temperatures obtained on the same samples give temperatures of c. 960-980 °C; the latter seems to be a more reliable temperature estimate. Interpretation of geochemical and isotope data from the complex suggest that the early synorogenic Pan-African igneous activity in this part of the Damara Belt was a high-temperature intra-crustal event. In contrast to igneous processes along active continental margins that produce also intermediate plutons with calc-alkaline affinities, this igneous event was not a major crust-forming episode and the granodiorites represent mostly reprocessed crustal material

From pole to pole : 33 years of physical oceanography onboard R/V Polarstern

Measuring temperature and salinity profiles in the world's oceans is crucial to understanding ocean dynamics and its influence on the heat budget, the water cycle, the marine environment and on our climate. Since 1983 the German research vessel and icebreaker Polarstern has been the platform of numerous CTD (conductivity, temperature, depth instrument) deployments in the Arctic and the Antarctic. We report on a unique data collection spanning 33 years of polar CTD data. In total 131 data sets (1 data set per cruise leg) containing data from 10 063 CTD casts are now freely available at doi: 10.1594/PANGAEA.860066. During this long period five CTD types with different characteristics and accuracies have been used. Therefore the instruments and processing procedures (sensor calibration, data validation, etc.) are described in detail. This compilation is special not only with regard to the quantity but also the quality of the data -the latter indicated for each data set using defined quality codes. The complete data collection includes a number of repeated sections for which the quality code can be used to investigate and evaluate long-term changes. Beginning with 2010, the salinity measurements presented here are of the highest quality possible in this field owing to the introduction of the OPTIMARE Precision Salinometer.Peer reviewe

Novel, multi-platform acoustic and optical sensors and data services developed in the NeXOS project

The European Union FP7 project “Next generation, Cost- effective, Compact, Multifunctional Web Enabled Ocean Sensor Systems Empowering Marine, Maritime and Fisheries Management” (NeXOS, 2013-2017) focused on innovative approaches for two classes of insitu observations, acoustic and optical. Two types of innovative passive acoustic sensors were developed - one having a single detector with increased dynamic range and internal processing to reduce communication requirements and the other having an array of four such sensors providing directional capabilities. The optical sensors developed were Matrix fluorescence sensors, a minifluo fluorescence sensor, flow-through cavity absorption sensors, and sensors for monitoring the carbon system. Additionally, optical sensors for chlorophyll-a and dissolved oxygen were adapted for use in fisheries. The sensors were modified to enable plug-and-play capabilities on basis of the Open Geospatial Consortium (OCG) PUCK protocol embedded in the internal software of the sensor. This protocol ensures that measured data are accompanied by metadata describing the sensor and its history. The OGC Sensor Web Enablement (SWE) and the Sensor Observation Service (SOS) web server make data from the NeXOS sensors available in real-time to the end- users. The final demonstrations took place during summer of 2017 in the Northeast Atlantic, Central Atlantic and the Mediterranean. This manuscript presents the main outcomes of the project.Le projet FP7 de l'Union européenne «Systèmes de capteurs océaniques compatibles avec le Web de nouvelle génération, rentables, compacts et multifonctionnels permettant une gestion marine, maritime et des pêches» (NeXOS, 2013-2017) s'est concentré sur des approches innovantes pour deux classes d'observations in situ, acoustiques et optiques. . Deux types de capteurs acoustiques passifs innovants ont été développés - l'un ayant un seul détecteur avec une plage dynamique accrue et un traitement interne pour réduire les exigences de communication et l'autre ayant un réseau de quatre capteurs offrant des capacités directionnelles. Les capteurs optiques développés étaient des capteurs de fluorescence Matrix, un capteur de fluorescence minifluo, des capteurs d'absorption à cavité traversante et des capteurs pour surveiller le système de carbone. De plus, des capteurs optiques pour la chlorophylle-a et l'oxygène dissous ont été adaptés pour une utilisation dans les pêcheries. Les capteurs ont été modifiés pour permettre des capacités plug-and-play sur la base du protocole PUCK d'Open Geospatial Consortium (OCG) intégré dans le logiciel interne du capteur. Ce protocole garantit que les données mesurées sont accompagnées de métadonnées décrivant le capteur et son historique. Le logiciel OGC Sensor Web Enablement (SWE) et le serveur Web Sensor Observation Service (SOS) mettent les données des capteurs NeXOS à la disposition des utilisateurs finaux en temps réel. Les dernières manifestations ont eu lieu au cours de l'été 2017 dans l'Atlantique Nord-Est, l'Atlantique Centre et la Méditerranée. Ce manuscrit présente les principaux résultats du projet