3. Wochenbericht L'ATALANTE ATA_IFMGEOMAR/1

L'Atalante 2007/8 Abschnitt 1 Vom 03.12. - 03.01.2008 findet der erste Abschnitt der L'Atalante-Expedition 2007/2008 unter der Fahrtleitung von Dr. Sven Petersen statt. Dieser Abschnitt beginnt in Toulon (Frankreich) und endet in Recife (Brasilien). Wissenschaftliches Programm: Dieser Fahrtabschnitt dient der Fortsetzung der Zeitreihenuntersuchungen im Rahmen des DFG SPP 1144 „Vom Mantel zum Ozean“, die in 2004 im Logatchev-Hydrothermalfeld (14°45'N, 45°W am Mittelatlantischen Rücken) mit der Expedition M60/3 begonnen haben und mit Fahrten in 2005 (M64/2) und Anfang 2007(MSM04/3) fortgesetzt wurde. Während dieses Fahrtabschnittes sollen die Ursachen für zeitliche und räumliche Variation in der Fluidtemperatur und –zusammensetzung und die Auswirkungen auf die assoziierte Fauna sowie ozeanographische Aspekte untersucht werden. Um den Einfluss physikalisch-geochemischer Parameter auf die hydrothermale Aktivität zu untersuchen sollen Langzeituntersuchungen der lokalen Seismizität, der Deformation des Meeresboden sowie des lokalen Wärmestroms vorgenommen werden. Die Auswirkungen werden durch gezielte Probenahme der hydrothermalen Plumewolke, der Ventfluide und der assoziierten Makro- und Mikrofauna untersucht. Hochauflösende vertikale geochemische Gradienten sollen in Bakterienmatten gemessen und mit der mikrobiellen Aktivität und den geophysikalischen und hydrographischen Daten korreliert werden. Hauptarbeitsgerät für diese Untersuchungen wird das neue ROV Kiel 6000 des IFM-GEOMAR sein. Um die langfristigen Variationen der hydrothermalen Aktivität im Logatchev Feld zu bestimmen, soll durch einen verankerten CTD-Profiler die bodennahe (bis 1000 m) Hydrographie und das Strömungsfeld für einen Zeitraum von ca. 1 Jahr bestimmt werden. Diese Daten sind für die Ziele des SPP von besonderer Bedeutung, da Abschätzungen des Wärme- und Massentransfers vom Mantel in den Ozean ohne diese Daten nicht möglich sind. Das Aussetzen einer Reihe von OBS-Instrumenten (Projekt Hydroplumb im Rahmen des SPP 1144; PI: Dr. I. Grevemeyer, IFM-GEOMAR) dient der langfristigen Aufzeichnung der regionalen Seismizität, die für die Interpretation der Variabilität der hydrothermalen Aktivität von großer Bedeutung ist. Atalante (HYDROMAR V) (04.12. 2007 – 02.01 2008) 3. Wochenbericht vom 18. bis 24. Dezember 200

Merian Expedition MSM03/2 (HYDROMAR IV) Fort de France – Fort de France 8.11.-30.11.2006

Merian 3/2 Die 3. Forschnugsfahrt des neuen deutschen Forschungsschiffs Maria S. Merian fand vom 08.11. bis 30. 11. 2006 unter der Fahrtleitung von Dr. S. Petersen statt

1. Wochenbericht M86/4

FS Meteor Reise M86, Fahrtabschnitt 4 Dubrovnik – Palma de Mallorca 1. Wochenbericht, 05.02.-11.02.201

TYMAS "Tyrrhenische Massivsulfide", Messina - Messina, 06.07. - 17.07.2006

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Sea-floor tectonics and submarine hydrothermal systems

The discovery of metal-depositing hot springs on the sea floor, and especially their link to chemosynthetic life, was among the most compelling and significant scientific advances of the twentieth century. More than 300 sites of hydrothermal activity and sea-floor mineralization are known on the ocean floor. About 100 of these are sites of high-temperature venting and polymetallic sulfide deposits. They occur at mid-ocean ridges (65%), in back-arc basins (22%), and on submarine volcanic arcs (12%). Although high-temperature, 350°C, black smoker vents are the most recognizable features of sea-floor hydrothermal activity, a wide range of different styles of mineralization has been found. Different volcanic substrates, including mid-ocean ridge basalt, ultramafic intrusive rocks, and more evolved volcanic suites in both oceanic and continental crust, as well as temperature-dependent solubility controls, account for the main geochemical associations found in the deposits. Although end-member hydrothermal fluids mainly originate in the deep volcanic basement, the presence of sediments and other substrates can have a large effect on the compositions of the vent fluids. In arc and backarc settings, vent fluid compositions are broadly similar to those at mid-ocean ridges, but the arc magmas also supply a number of components to the hydrothermal fluids. The majority of known black smoker vents occur on fast-spreading mid-ocean ridges, but the largest massive sulfide deposits are located at intermediate- and slow-spreading centers, at ridge-axis volcanoes, in deep backarc basins, and in sedimented rifts adjacent to continental margins. The range of deposit sizes in these settings is similar to that of ancient volcanic-associated massive sulfide (VMS) deposits. Detailed mapping, and in some cases drilling, indicates that a number of deposits contain 1 to 5 million tons (Mt) of massive sulfide (e.g., TAG hydrothermal field on the Mid-Atlantic Ridge, deposits of the Galapagos Rift, and at 13°N on the East Pacific Rise). Two sediment-hosted deposits, at Middle Valley on the Juan de Fuca Ridge and in the Atlantis II Deep of the Red Sea, are much larger (up to 15 and 90 Mt, respectively). In the western Pacific, high-temperature hydrothermal systems occur mainly at intraoceanic back-arc spreading centers (e.g., Lau basin, North Fiji basin, Mariana trough) and in arc-related rifts at continental margins (e.g., Okinawa trough). In contrast to the mid-ocean ridges, convergent margin settings are characterized by a range of different crustal thicknesses and compositions, variable heat flow regimes, and diverse magma types. These variations result in major differences in the compositions and isotopic systematics of the hydrothermal fluids and the mineralogy and bulk compositions of the associated mineral deposits. Intraoceanic back-arc basin spreading centers host black smoker vents that, for the most part, are very similar to those on the mid-ocean ridges. However, isotopic data from both the volcanic rocks and the sulfide deposits highlight the importance of subduction recycling in the origin of the magmas and hydrothermal fluids. Back-arc rifts in continental margin settings are typically sediment-filled basins, which derive their sediment load from the adjacent continental shelf. This has an insulating effect that enhances the high heat flow associated with rifting of the continental crust and also helps to preserve the contained sulfide deposits. Large hydrothermal systems have developed where initial rifting of continental crust or locally thickened arc crust has formed large calderalike sea-floor depressions, similar to those that contained major VMS-forming systems in the geologic record. Hydrothermal vents also occur in the summit calderas of submarine volcanoes at the volcanic fronts of arcs. However, this contrasts with the interpreted settings of most ancient VMS deposits, which are considered to have formed mainly during arc rifting. Hydrothermal vents associated with arc volcanoes show clear evidence of the direct input of magmatic volatiles, similar to magmatic-hydrothermal systems in subaerial volcanic arcs. Several compelling examples of submarine epithermal-style mineralization, including gold-base metal veins, have been found on submarine arc volcanoes,and this type of mineralization may be more common than is presently recognized. Mapping and sampling of the sea floor has dramatically improved geodynamic models of different submarine volcanic and tectonic settings and has helped to establish a framework for the characterization of many similar ancient terranes. Deposits forming at convergent margins are considered to be the closest analogs of ancient VMS. However, black smokers on the mid-ocean ridges continue to provide critically important information about metal transport and deposition in sea-floor hydrothermal systems of all types. Ongoing sea-floor exploration in other settings is providing clues to the diversity of mineral deposit types that occur in different environments and the conditions that are favorable for their formation