georefid:2005-008990SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=2005-0089902002-01-01publicationgeorefid:2005-008990Franklin, James M.Franklin Geosciences, Ottawa, ON, CanadaauthorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyIn: Anonymous, Geological Society of America, 2002 annual meeting34 (6)444-445Mineralizing processes at seafloor hydrothermal sites are directly observed and measured, reducing uncertainties inherent in interpretation of ancient, deformed and metamorphosed ore-bearing districts. The best example is volcanogenic massive sulfide (VMS) deposits. For these, seawater is down-drawn regionally to cool shallow crustal-level subvolcanic intrusions; these provide heat and drive convective circulation beneath caps which inhibit cross-stratal fluid migration. Trapped fluids reach approximately 400C and react with their enclosing strata, imparting a unique mineralogical imprint on the latter and releasing metals to the fluid. Fluids discharge in convective upwelling zones or along caldera- or rift-margin extensional faults. Near-seafloor reactions form distinct alteration pipes. Fluids discharge on or near the seafloor, where rapid cooling induces massive precipitation. Seafloor research contributes as follows: Magma-chamber petrochemical processes are unique to these environments, as shown by the specific occurrence of andesite (Galapagos VMS site). Identification of such petrochemically-unique units helps refine the land-based search in frontier areas. The ODP drill program (Legs 139 & 169; hole 504B) contributed to our knowledge of the reaction zone attributes; Site 857 at Middle Valley provided unequivocal mineralogical and compositional measures that now are applied in ancient sequences. Subseafloor alteration pipes establish sectoral and temporal variations in discharge-zone mineral and chemical attributes(Galapagos, TAG); these provide useable guides to ore in ancient pipes. The volcanological characteristics of caldera (Axial) and rift-related (Endeavour, EPR) synvolcanic faults provide a template for understanding similar preserved sequences. Finally, studies of vent fluids provide knowledge of metal speciation and predict characteristics such as gold contents (Axial, Lau, Havre Trough), sub-seafloor depositional and zone-refining attributes (ODP:TAG & Middle Valley), and far-field vectors from plume fallout. As research extends to new environments (arcs and backarcs) and to greater sub-seafloor depths (proposed TAG and other ODP sites) we will develop new, quantitative exploration guides that will be applied in searching for increasingly scarce mineral resources.completedEconomic geology, general, depositsalterationAtlantic Oceanback-arc basinsbasinschemical reactionscoolingdischargeDSDP Site 504East Pacific Ocean Islandsextension faultsfaultsGalapagos IslandsintrusionsLeg 139Leg 169magma chambersmagmasmassive depositsmassive sulfide depositsmeasurementmetal oresMid-Atlantic RidgeMiddle Valleymineral explorationmineral resourcesmineralizationNorth AtlanticobservationsOcean Drilling Programocean floorsprecipitationprocessesquantitative analysisresearchsea waterTAG hydrothermal fieldtemperatureupwellingvariationsurn:org.iodp:exp:139urnlargerWorkCitationcampaignurn:org.iodp:exp:169urnlargerWorkCitationcampaignurn:org.iodp:exp:111:site:504urnlargerWorkCitationstudyurn:org.iodp:exp:111urnlargerWorkCitationcampaignurn:org.iodp:exp:137:site:504urnlargerWorkCitationstudyurn:org.iodp:exp:137urnlargerWorkCitationcampaignurn:org.iodp:exp:140:site:504urnlargerWorkCitationstudyurn:org.iodp:exp:140urnlargerWorkCitationcampaignurn:org.iodp:exp:148:site:504urnlargerWorkCitationstudyurn:org.iodp:exp:148urnlargerWorkCitationcampaignEnglishgeoscientificInformation-128.4500-44.4900-1.300048.2800Galapagos IslandsTAG hydrothermal field