1,721,253 research outputs found
Multibeam bathymetry processed data (Reson SeaBat 7125 working area dataset) of AUV ABYSS during cruise with RV POSEIDON POS510, Kolumbo Seamount
No full textSwath sonar bathymetry data of the AUV ABYSS (GEOMAR) was recorded during RV POSEIDON cruise POS510 in March 2017 for the project "ANYDROS: Rifting and Hydrothermal Activity in the Cyclades Back-arc Basin". Chief Scientist was Prof. Mark Hannington from GEOMAR Helmholtz Centre for Ocean Research Kiel. The cruise took place between 2017-03-06 and 2017-03-29 in the Mediterranean Sea near Santorini, Greece. The cruise report is available under the following url: https://oceanrep.geomar.de/id/eprint/44466
The data was acquired during seven AUV dives at Kolumbo Seamount (NE of Santorini Island) by AUV ABYSS using a Kongsberg RESON Seabat 7125 Multibeam system run with a frequency of 200 kHz. Data were manually edited for false measurements in the software Qimera. No further artificial sound velocity profiles were used during processing. The data of the individual dives was combined, gridded at 2m resolution and the midpoints exported as txt-file with Latitude and Longitude provided in WGS84 datum and depth with negative values
Chemostratigraphy and Alteration Geochemistry of the Lundberg and Engine House Volcanogenic Massive Sulfide Mineralization, Buchans, Central Newfoundland
No full textThe world-class Buchans Mining Camp hosts a number of high-grade, low-tonnage volcanogenic massive sulfide (VMS) deposits. The Lundberg and Engine House zones form the lower-grade stockwork to the Lucky Strike deposit and have yet to be mined. A detailed study of the Lundberg and Engine House zones was conducted to establish the stratigraphic setting of the deposits, to determine the petrology of the host volcanic rocks and distribution of alteration facies, and to characterize the mineralization with the goal of improving exploration for polymetallic massive sulfide deposits in the Buchans camp
Intrabasinal Sediments and Tectonostratigraphy of the N.E. Lau Basin: Contributions to Extensional Models of Back-Arc Basins
No full textSediment deposited in back-arc basins preserves a record of the extensional, volcanic and tectonic history of the arc-backarc systems. Back-arc sedimentation is of particular interest as seafloor massive sulfide deposits may be preserved in back-arc basin sediments.
The study of back-arc sedimentation using acoustic data, such as high-resolution sub-bottom profiling data (Parasound) and seismic reflection data, can be a much more cost effective approach than analysis of sediments recovered from drill cores. In this study, we use these two acoustic datasets to build a facies model of sedimentation in the northeast Lau Basin, an actively opening back-arc basin in the southwest Pacific Ocean. Using 830 km of Parasound and 730 km of seismic lines along 4 transects of the Lau Basin, we constructed one of the most detailed models of sedimentation in a back-arc basin to date. Parasound data show distinct echoes with sub-bottom reflections indicative of a high proportion of hemipelagic sediment, whereas the indistinct echoes with few to no sub-bottom reflections indicate a higher proportion of coarse, bedded, volcaniclastic turbidites. Hyperbolic echoes are associated with regions of rugged or uneven terrain characterized by exposed, rough basement or deposits formed by contour currents, turbidity currents, slumps or slides. These relationships form the basis of an echo-facies legend developed for typical back-arc basin sediments. The echo-facies observed in the Parasound, and confirmed by deeper-penetrating seismic reflection data, provide important insights into the sedimentary processes involved in back-arc sedimentation. We observed mass transport deposits (MTDs) in all of the sub-basins and slope deposits within and on the flanks of active rifts (e.g., the Fonualei Rift and Spreading Centre, FRSC), suggesting a direct correlation between MTDs and zones of active rifting. We observed an overall increase in sediment thickness toward the Tofua Arc which suggests it is the main sediment source, but local variations in sediment thickness suggest significant input from local intrabasinal seamounts. The uppermost echo-facies in over 60% of the sub-basins in the study area is dominated by hemipelagic material, which suggests an abrupt transition in the dominant sediment source from volcaniclastic to hemipelagic at around 0.3 Ma, when a period of volcanic quiescence from the Tofua Arc began. The study shows that a near complete record of basin evolution can be constructed using geophysical and acoustic methods and that this work may help to locate future drill sites where in situ data can be collected
Chemostratigraphy and Alteration Geochemistry of the Lundberg and Engine House Volcanogenic Massive Sulfide Mineralization, Buchans, Central Newfoundland
No full textThe world-class Buchans Mining Camp hosts a number of high-grade, low-tonnage volcanogenic massive sulfide (VMS) deposits. The Lundberg and Engine House zones form the lower-grade stockwork to the Lucky Strike deposit and have yet to be mined. A detailed study of the Lundberg and Engine House zones was conducted to establish the stratigraphic setting of the deposits, to determine the petrology of the host volcanic rocks and distribution of alteration facies, and to characterize the mineralization with the goal of improving exploration for polymetallic massive sulfide deposits in the Buchans camp
Volcanism in Modern Back-arc Regimes and Their Implications for Ancient Greenstone Belts
No full textGreenstone belts are dominated by volcanic rocks with lithogeochemical characteristics that reflect a range of possible geodynamic settings. Many analogies with modern tectonic settings have been suggested. Increasing exploration and comprehensive sampling of volcanic rocks in modern oceans provides the unique opportunity to characterize different melt sources from intraoceanic settings. This thesis examines geochemical data from more than 2850 submarine mafic and more than 2200 submarine felsic volcanic rocks, representing a wide range of settings. The results show significant geochemical variability spanning the full range of compositions of volcanic rocks found in ancient greenstone belts. This diversity reflects complex rift and spreading regimes, variations in crustal thickness, dry melting versus wet melting, mantle mixing and crustal contamination. Highly variable melting conditions are thought to be related to mantle heterogeneities, complex mantle flow regimes and short-lived tectonic domains, such as those caused by diffuse spreading, multiple overlapping spreading centers and microplate breakouts.
Systematic differences in the volcanic rocks are revealed by a combination of principal components analysis and unsupervised hierarchical clustering. Rocks from most arc-backarc systems have strongly depleted mantle signatures and well-known subduction-related chemistry. This contrasts with rocks in Archean greenstone belts, which show no, or at least weaker, subduction-related chemistry and stronger mantle enrichment resulting from a less-depleted mantle, less wet-melting, and variable crustal contamination. The geochemistry of the modern volcanic rocks reflects lower mantle temperatures, thinner crust and subduction-related processes of present-day settings. However, rocks that are geochemically identical to those in Archean greenstone belts occur in many modern back-arc basins, such as the Lau Basin. Crustal growth and area-age relationships in the Lau Basin are similar to observed ages and compositions of volcanic assemblages in greenstone belts, such as the Blake River Group of the Abitibi Greenstone Belt. Such settings are recognized as favorable locations for volcanogenic massive sulfide (VMS) deposits, and therefore the particular geochemical signatures of the volcanic rocks are important for enhanced area selection in base and precious metal exploration
Trace Element Geochemistry of Volcanogenic Massive Sulfide Deposits in Archean Greenstone Belts: Implications for Metal Endowment and Geodynamic Settings
No full textThe Neoarchean greenstone belts of the Canadian Superior Province host world-class Au and base metal (Cu-Zn-Pb) massive sulfide deposits with distinct geological features, including a wide range of different host rocks and crustal settings. The range of settings is reflected in the trace metal signatures of their ores. This study examines the trace element geochemistry of pyrite from 55 different Archean volcanogenic massive sulfide (VMS) deposits in Canada to test the relationship to their host rocks, the deposit sizes and their grades. The database includes 258 samples of pyrite from 47 deposits in the Abitibi Greenstone Belt (AGB), together with 30 samples from 8 deposits in the Western Superior (Sturgeon Lake, Uchi, Benny, and Manitouwadge belts) and 45 samples from 6 deposits in the Slave Province (Hackett River, Amooga Booga, and High Lake belts). We used statistical methods to characterize the trace element geochemistry of pyrite in grab samples from the deposits, as well as larger samples representing many thousand of tonnes of ore from monthly concentrates. The study focused on pyrite mineral separates comparing samples from different deposits and different ore types within individual deposits. The analysis shows the trace element geochemistry of pyrite is a useful fingerprint of the different mineralizing systems, with trace element enrichments and depletions reflecting different source rocks, inferred temperatures of ore formation, and the scales of the hydrothermal systems. A comparison of the Abitibi samples to other deposits in the Superior Province shows distinct trace element signatures between primitive and more evolved crustal settings of different age. Similar results are found among 102 samples of pyrite from 30 deposits in Proterozoic and Phanerozoic belts across Canada.
District-scale variations in pyrite chemistry mainly reflect host rock and correlate different bulk Cu/(Cu+Zn) grade ratios of the deposits. Pyrite samples from Cu-rich deposits are enriched in Cu, Bi, Co, Ni, Se, Te and Mo; whereas pyrite samples from Zn-rich deposits are enriched in Pb, Ag, Cd, In, Ga, Sn, As, Sb, Hg and Tl. The same patterns are observed in Cu-rich versus Zn-rich zones of individual deposits. Statistical analyses reveal pyrite samples from VMS deposits in the AGB that are associated with primitive mafic-ultramafic tholeiitic rocks (e.g., Potter-Doal and Genex from Timmins, and East Sullivan and Dunraine from Val d'Or camps) are enriched in Cu (>5000 ppm), Co (>1500 ppm), Se (>4000 ppm), and Ni (>250 ppm), whereas pyrite from deposits associated with tholeiitic to calc-alkaline felsic rocks (e.g., Abcourt-Barvue from the Amos-Barraute camp) are commonly enriched in Pb, Ag, Au, Cd, In, Sn, As, Sb, Hg, Tl (10s to 100s of ppm). These variations closely match primary trace element abundances in unaltered volcanic rocks compiled from over 4000 high-quality analyses of samples from the Superior Province. Whole-rock data for rhyolite confirm high concentrations of Pb, Ag, Bi, Te, Cd, In, Ga, Sn, Hg, and Tl compared to basalt and komatiite, which have higher Cu, Co, Ni, and Se.
The variation in trace element concentrations in pyrite is remarkably consistent for different deposits. We note that randomly sampled pyrite from almost any part of a deposit with a bulk enrichment in a particular element shows notable enrichment in that element compared to pyrite from other deposits. Pyrite from a deposit with a bulk enrichment in Te, for example (Quemont in the Noranda camp), will almost certainly contain more Te than pyrite from other Te-poor deposits. We test this observation among 47 deposits for 15 different elements.
Pyrite samples from Au-rich VMS deposits (e.g., Horne, Quemont, Bousquet #2, and Dumagami) have anomalous Au (>6 ppm) and Te (>70 ppm). Co-enrichment in other elements such as Bi, Se, In and Sn may reflect a common felsic magmatic source. Other trace element enrichments appear to reflect the scale of the hydrothermal system (e.g., depth and extent of leaching). For example, pyrite samples from several large-tonnage deposits (Kidd Creek, Horne #5 Zone, and Geco) have high Sn concentrations (from 450 to 15000 ppm) possibly reflecting the large volumes of felsic rock from which the Sn was extracted. In other deposits, co-enrichment of Sn with Bi (>100 ppm) and In (>10 ppm) suggest a magmatic contribution to the ore fluids Principal Components Analysis (PCA) combined with hierarchal clustering confirms systematic trace element variability in pyrite from deposits with different host rocks and bulk Cu/(Cu+Zn) ratios. However, pyrite from deposits in different terranes seems to record major differences in the crustal compositions of those terranes. For example, pyrite samples from bimodal-felsic deposits show the same trace element signatures (i.e., enrichments in Ag, As, Sb, and Hg) in the AGB and in the Western Superior. In contrast, pyrite samples from deposits in the Slave craton tend to show a distinct enrichment in Pb, U and Th that may be related to the more mature and thicker crust in the Slave compared to the AGB. Other deposit types (magmatic Cu vein deposits, orogenic Au deposits) also show dramatically different pyrite compositions. Pyrite concentrates from magmatic Cu vein deposits in Chibougamau are enriched in Cu, Co, Ni, Te, As, Sb compared to VMS in the AGB, and samples from orogenic Au deposits in Timmins and Val d'Or are enriched in Au and Mo and depleted in Pb, Bi, As, and Sb compared to VMS. These differences highlight the potential application of the trace element signatures of pyrite during exploration for different deposit types in the same region.
Trace element signatures of pyrite in grab samples compared favourably to much larger bulk samples from the same deposits (e.g., monthly concentrates and mine tailings) giving some confidence that the much smaller samples can provide a reliable first-order fingerprint of the deposits as a whole. LA-ICP-MS analyses of individual pyrite grains also agreed well with bulk analyses of pyrite over a wide range of trace element concentrations (10s to 100s of ppm)
RV POSEIDON Fahrtbericht / Cruise Report POS494/2, HIERROSEIS Leg 2: Assessment of the Ongoing Magmatic-Hydrothermal Discharge of the El Hierro Submarine Volcano, Canary Islands by the Submersible JAGO, Valverde – Las Palmas (Spain), 07.02.16-15.02.16
No full textRV POSEIDON Fahrtbericht / Cruise Report POS510 - ANYDROS: Rifting and Hydrothermal Activity in the Cyclades Back-arc Basin, Catania (Italy) – Heraklion (Greece) 06.03.-29.03.2017
Get PDFSpuren- und kritisches Metallverhalten in massiven Sulfidvorkommen am Meeresboden: Eine mineralogische und geochemische Bewertung
Get PDFActively-forming modern seafloor massive sulfide (SMS) deposits are analogous to ancient volcanogenic-hosted massive sulfide (VMS) deposits which are major sources of Zn, Cu, Pb, Ag, and Au, and significant sources for Co, Sn, Se, Mn, Cd, In, Bi, Te, and Sb. Growing interest in the mining potential of major, trace, and critical metals in SMS deposits has not taken into account sub-seafloor mineralogical characterization which is crucial to the metal budgets. The majority of SMS samples are from the surface or very shallow-subsurface and trace element concentrations are not representative of the entire sub-seafloor deposit. A three-part approach in this thesis investigated the distribution and mineralogical residence of trace elements in sub-seafloor submarine hydrothermal systems, in order to understand metal budgets and determine whether the behaviour and residence of trace elements can be systematically predicted.Aktive Massivsulfidvorkommen vom Meeresboden (SMS) gelten als moderne Analoga zu den sogenannten Vulkanit-gebundenen Massivsulfidvorkommen der Erdgeschichte, die wichtige Quellen für die Metalle Zn, Cu, Pb, Ag und Au sind sowie signifikante Mengen an Co, Sn, Se, Mn, Cd, In, Bi, Te und Sb enthalten. Das wachsende Interesse an dem Rohstoffpotential der rezenten Vorkommen in Bezug auf Haupt-, Spuren- und kritischen Metallen hat die mineralogischen Eigenschaften der unterhalb des Meeresbodens liegenden Zonen nicht berücksichtigt. Dabei sind diese Bereiche für die Abschätzung des Rohstoffpotentials wesentlich. Der bei Weitem größte Teil der modernen Massivsulfidproben stammt von der Meeresbodenoberfläche oder den Bereichen knapp darunter und ihre Metallgehalte sind für die tieferen Bereiche nicht repräsentativ. Durch einen dreiteiligen Ansatz soll in dieser Doktorarbeit die Verteilung und die mineralogische Kontrolle der Spurenelementzusammensetzung in den tieferen Bereichen rezenter Hydrothermalsysteme untersucht werden, um die Metallbudgets zu verstehen und um das Verhalten und das Vorkommen der Spurenmetalle in diesen Vorkommen systematisch vorherzusagen
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