Ocean crust vein mineral deposition; Rb/Sr ages, U-Th-Pb geochemistry, and duration of circulation at DSDP sites 261, 262 and 516

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doi: 10.1016/0016-7037(86)90224-3
Author(s): Hart, S. R.; Staudigel, H.
Author Affiliation(s): Primary:
Mass. Inst. Technol., Cent. Geoalchemy, Cambridge, MA, United States
Other:
Scripps Inst. Oceanogr., United States
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, 50(12), p.2751-2761. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. 49 refs.; illus. incl. 4 tables
Summary: Leaching techniques using ammonium acetate were applied to celadonite-smectite vein minerals to remove common Sr relative to Rb and radiogenic Sr. This increased the Rb/Sr ratio by 2.3-22 without significantly altering the age of the minerals. 'Circulation' ages in ocean crust were then attempted for a wider range of geographical and geotectonic settings. Ages obtained were: 121.4 + or - 1.6 m.y. (site 261); 105. + or - 2.8 m.y. (site 462A); 69.9 + or - 2.4 m.y. (site 516F). These are 34, 54 and 18 m.y. younger respectively than the age of crust formation at the sites. The younger age at site 462A is related to off-ridge emplacement of a massive sill/flow complex, and at the other sites hydrothermal circulation persisted longer than for normal crust, or was reactivated by off-ridge igneous activity. U, Pb contents and Pb isotopic compositions of celadonites are little changed from their basalt precursors. The Th contents are low in the celadonites which have high alkali/U,Th ratios and low Th/U ratios. Initial Sr isotope ratios of ocean crust vein minerals (smectite, celadonite, zeolite, calcite) are intermediate between those of primary basalts and contemporary sea-water, indicating formation under effective sea-water/rock ratios of 20-200.
Year of Publication: 1986
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 01 Mineralogy and Crystallography; 02 Geochemistry; 03 Geochronology; 05 Petrology, Igneous and Metamorphic; Absolute age; Actinides; Calcite; Carbonates; Celadonite; Clay mineralogy; Clay minerals; Convection; Crust; DSDP Site 261; DSDP Site 462; DSDP Site 516; Dates; Deep Sea Drilling Project; Experimental studies; Framework silicates; Geochemistry; Hydrothermal alteration; IPOD; Ion exchange; Isotopes; Lead; Leg 27; Leg 61; Leg 72; Leg 89; Metals; Metasomatism; Mica group; Minerals; Oceanic crust; Processes; Rb/Sr; Sea water; Sheet silicates; Silicates; Smectite; Thorium; U/Th/Pb; Uranium; Veins; Zeolite group
Coordinates: N071415 N071415 E1650150 E1650150
S125700 S125700 E1175400 E1175400
S301800 S301500 W0352000 W0352400
Record ID: 1987028868
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom