The lower portion of the Paleoproterozoic Northern Liaohe Group, Liaoning, northeast China, comprises metavolcanics (tuff-dominated) and metasediments (mostly arkoses and dolostones) that host stratiform-strata bound Fe(Cu) sulfides and Ca(Ba) sulfates. The ore-bearing sequence consists of, in ascending order, pyroclastic rocks, terrigenous clastics, and carbonates, all of which have been metamorphosed to greenschist amphibolite grade. Extensive albite-rich breccias are present at the base of the succession and as pipes crosscutting a variety of lithologic units in the Lieryu Formation. The geometry, geochemistry, and associated structures of these albite-rich rocks suggest that they are metamorphosed salt domes.The sulfide-sulfate Fe(Cu) ores occur in a transitional zone between tuffs and dolomitic carbonates, with those in the upper cycle being economically more important. The sulfides were precipitated at two sites: around venting centers as breccias, lenses, and veins; and as stratiform pyrite-chalcopyrite associated with anhydrite that is distal to the salt domes. Within each mining district the proximal ores are associated with brecciated, albite- and tourmaline-rich rocks. The sulfides in the proximal ores have delta 34 S values of 8.9 to 12.7 per mil, whereas the distal ores have delta 34 S values of 2.6 to 8.8 per mil for the sulfides and 7.9 to 19.0 per mil for the anhydrite; suggesting a sulfate-dominated sulfur source, with the pyrite delta 34 S variations arising mainly from decreasing temperatures away from the centers of the deposits.The origin of the deposits is best described by a model in which sulfate-carbonate rocks were deposited in peripheral sinks during salt diapirism. The salt domes then acted as focuses for subsequent hydrothermal venting and were the centers of sulfide mineralization. The sulfides precipitated during interaction of the reduced, metal-bearing hydrothermal fluids with the in situ sulfates that were the major source of the sulfur.
Research Article| August 01, 2000 Sm-Nd dating of the giant Sullivan Pb-Zn-Ag deposit, British Columbia Shao-Yong Jiang; Shao-Yong Jiang 1State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China Search for other works by this author on: GSW Google Scholar John F. Slack; John F. Slack 2U.S. Geological Survey, National Center, MS 954, Reston, Virginia 20192, USA Search for other works by this author on: GSW Google Scholar Martin R. Palmer Martin R. Palmer 3T.H. Huxley School, Imperial College, Prince Consort Road, London SW7 2BP, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Shao-Yong Jiang 1State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China John F. Slack 2U.S. Geological Survey, National Center, MS 954, Reston, Virginia 20192, USA Martin R. Palmer 3T.H. Huxley School, Imperial College, Prince Consort Road, London SW7 2BP, UK Publisher: Geological Society of America Received: 11 Jan 2000 Revision Received: 19 May 2000 Accepted: 23 May 2000 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (8): 751–754. https://doi.org/10.1130/0091-7613(2000)28<751:SDOTGS>2.0.CO;2 Article history Received: 11 Jan 2000 Revision Received: 19 May 2000 Accepted: 23 May 2000 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Shao-Yong Jiang, John F. Slack, Martin R. Palmer; Sm-Nd dating of the giant Sullivan Pb-Zn-Ag deposit, British Columbia. Geology 2000;; 28 (8): 751–754. doi: https://doi.org/10.1130/0091-7613(2000)28<751:SDOTGS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We report here Sm and Nd isotope data for hydrothermal tourmalinites and sulfide ores from the giant Sullivan Pb-Zn-Ag deposit, which occurs in the lower part of the Mesoproterozoic Purcell (Belt) Supergroup. Whole-rock samples of quartz-tourmaline tourmalinite from the footwall alteration pipe yield a Sm-Nd isochron age of 1470 ± 59 Ma, recording synsedimentary B metasomatism of clastic sediments during early evolution of the Sullivan hydrothermal system. Data for variably altered (chloritized and/or albitized) tourmalinites from the hanging wall of the deposit, which are believed to have formed originally ca. 1470 Ma, define a younger 1076 ± 77 Ma isochron because of resetting of Sm and Nd isotopes during Grenvillian metamorphism. HCl leachates of bedded Pb-Zn ore yield a Sm-Nd isochron age of 1451 ± 46 Ma, which is consistent with syngenetic-exhalative mineralization ca. 1470 Ma; this age could also reflect a slightly younger, epigenetic hydrothermal event. Results obtained for the Sullivan deposit indicate that the Sm-Nd geochronometer has the potential to directly date mineralization and alteration in stratabound sulfide deposits that are not amenable to dating by other isotope methods. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The carbon dioxide content of the atmosphere [measured as the partial pressure of CO2 (pCO2)] affects the content of the surface ocean, which in turn affects seawater pH. The boron isotope composition (delta11B) of contemporaneous planktonic foraminifera that calcified their tests at different water depths can be used to reconstruct the pH-depth profile of ancient seawater. Construction of a pH profile for the middle Eocene tropical Pacific Ocean shows that atmospheric pCO2 was probably similar to modern concentrations or slightly higher.
Abstract The Rockeskyll complex in the north, central part of the Quaternary West Eifel volcanic field encapsulates an association of carbonatite, nephelinite and phonolite. The volcanic complex is dominated by three eruptive centres, which are distinct in their magma chemistry and their mode of emplacement. The Auf Dickel diatreme forms one centre and has erupted the only known carbonatite in the West Eifel, along with a broad range of alkaline rock types. Extrusive carbonatitic volcanism is represented by spheroidal autoliths, which preserve an equilibrium assemblage. The diatreme has also erupted xenoliths of calcite-bearing feldspathoidal syenite, phonolite and sanidine and clinopyroxene megacrysts, which are interpreted as fragments of a sub-volcanic complex. The carbonate phase of volcanism has several manifestations; extrusive lapilli, recrystallized ashes and calcite-bearing syenites, fragmented during diatreme emplacement. A petrogenetic link between carbonatites and alkali mafic magmas is confirmed from Sr and Nd isotope systematics, and an upper mantle origin for the felsic rocks is suggested. The chemistry and mineralogy of mantle xenoliths erupted throughout the West Eifel indicate enrichment in those elements incompatible in the mantle. In addition, the evidence from trace element signatures and melts trapped as glasses support interaction between depleted mantle and small volume carbonate and felsic melts. This close association between carbonate and felsic melts in the mantle is mirrored in the surface eruptives of Auf Dickel and at numerous alkaline-carbonatite provinces worldwide.
IODP Expedition 340 successfully drilled a series of sites offshore Montserrat, Martinique and Dominica in the Lesser Antilles from March to April 2012. These are among the few drill sites gathered around volcanic islands, and the first scientific drilling of large and likely tsunamigenic volcanic island-arc landslide deposits. These cores provide evidence and tests of previous hypotheses for the composition and origin of those deposits. Sites U1394, U1399, and U1400 that penetrated landslide deposits recovered exclusively seafloor sediment, comprising mainly turbidites and hemipelagic deposits, and lacked debris avalanche deposits. This supports the concepts that i/ volcanic debris avalanches tend to stop at the slope break, and ii/ widespread and voluminous failures of preexisting low-gradient seafloor sediment can be triggered by initial emplacement of material from the volcano. Offshore Martinique (U1399 and 1400), the landslide deposits comprised blocks of parallel strata that were tilted or microfaulted, sometimes separated by intervals of homogenized sediment (intense shearing), while Site U1394 offshore Montserrat penetrated a flat-lying block of intact strata. The most likely mechanism for generating these large-scale seafloor sediment failures appears to be propagation of a decollement from proximal areas loaded and incised by a volcanic debris avalanche. These results have implications for the magnitude of tsunami generation. Under some conditions, volcanic island landslide deposits composed of mainly seafloor sediment will tend to form smaller magnitude tsunamis than equivalent volumes of subaerial block-rich mass flows rapidly entering water. Expedition 340 also successfully drilled sites to access the undisturbed record of eruption fallout layers intercalated with marine sediment which provide an outstanding high-resolution data set to analyze eruption and landslides cycles, improve understanding of magmatic evolution as well as offshore sedimentation processes.
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