georefid:2000-015677SEDIS 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=2000-0156771997-01-01publicationgeorefid:2000-015677Gendler, T. S.Russian Academy of Sciences, Schmidt Joint Institute of Physics of the Earth, Moscow, Russian FederationauthorKrasnov, S. G.Institute for Geology and Mineral Resources of the Ocean, Russian FederationauthorPechersky, D. M.authorStepanova, T. V.authorTsel'movich, V. A.authorSharonova, Z. V.authorSholpo, L. E.authorKhaliulina, E. A.authorMAIK, Nauka/Interperiodica Publishing, Birmingham, AL, United StatespublisherdocumentHardcopyIzvestiya - Russian Academy of Sciences. Physics of the Solid Earth33 (2)89-112Sulfide ores of a massive deposit drilled by holes 856H and 856G, Ocean Drilling Project Leg 139 (Juan de Fuca Ridge), are studied by magnetic mineralogy, optical and electron microscopy, Mossbauer spectroscopy, X-ray diffraction, and microprobe analysis. The collection studied consists of 26 samples. The following iron-bearing minerals are recognized monoclinic and hexagonal primary pyrrhotite; sphalerite and chalcopyrite, formed from solutions at temperatures above 350 degrees C; secondary hexagonal pyrrhotite of lambda and intermediate types, pyrite, and marcasite, formed after primary pyrrhotite; and magnetite formed mostly after pyrite at a temperature below 350 degrees C. Both the pyrrhotite and the magnetite exhibit unusual features. Primary monoclinic pyrrhotite is partly disordered and shows high blocking temperatures (340-360 degrees C), whereas intermediate hexagonal pyrrhotite is partly ordered and thereby has remanent magnetization with blocking temperatures of 100-260 degrees C. Magnetite does not contain Mg, Mn, Ni, or other admixtures and is not oxidized; however, it is deficient in Fe and has lower Curie points (520-540 degrees C). This probably reflects specific features of its formation in a water environment. Diagrams are plotted that show the variation of sulfide phase concentrations along the hole 856H section and suggest a nonmonotonic, multistage process of crystallization of sulfide minerals involved in the orebody formation. The results obtained provide a deeper insight into the genesis of such rocks, both recent and ancient.completedEconomic geology, geology of ore depositsOceanographycrystallizationEast Pacificelectron microscopy datagenesisJuan de Fuca RidgeLeg 139Leg 169magnetic mineralsmagnetic propertiesmagnetitemagnetizationmarcasitemassive depositsmassive sulfide depositsmetal oresMossbauer spectraNorth PacificNortheast PacificOcean Drilling ProgramODP Site 856ore bodiesoxidesPacific OceanpaleomagnetismpyritepyrrhotitespectrasulfidesX-ray diffraction dataurn:org.iodp:exp:139urnlargerWorkCitationcampaignurn:org.iodp:exp:169urnlargerWorkCitationcampaignurn:org.iodp:exp:139:site:856urnlargerWorkCitationstudyurn:org.iodp:exp:139urnlargerWorkCitationcampaignurn:org.iodp:exp:169:site:856urnlargerWorkCitationstudyurn:org.iodp:exp:169urnlargerWorkCitationcampaignEnglishgeoscientificInformation-128.4500-127.000040.560048.2800