Temporal changes in the lead isotopic composition of red clays; comparison with ferromanganese crust records

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doi: 10.1016/S0009-2541(01)00406-5
Author(s): Godfrey, L. V.
Author Affiliation(s): Primary:
Cornell University, Department of Geological Sciences, Ithaca, NY, United States
Volume Title: Chemical Geology
Source: Chemical Geology, 185(3-4), p.241-254. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. Includes appendices. 51 refs.; illus., incl. 2 tables, sketch map
Summary: A record of changes in Pb and Sr isotopic composition of two cores (DSDP 86 576A and LL44 GPC3) from the red clay region of the central North Pacific has been determined for the past 60-65 million years. The isotope records of the eolian silicate fraction of the red clays reflect the change in source area as the core sites migrated under different wind systems. The Sr isotope compositions of eolian silicate material are consistent with Asian loess and North American arc volcanism that has been recognized from mineralogical studies. The silicate-bound eolian Pb isotopic compositions similarly reflect Asian loess and arc volcanism. The isotope records of three ferromanganese crusts from similar locations in the central Pacific are similar to the eolian component of red clays, but offset to less radiogenic values. This may be due to two mechanisms: (1) Pb that can be removed from eolian material by seawater is much less radiogenic, or less likely (2) hydrothermal Pb can be transported further away from venting sites through particle exchange with seawater, despite hydrothermal venting acting as a net sink of oceanic Pb. The temporal changes in Pb isotopes in the ferromanganese crusts, bulk red clays and eolian silicates are similar although offset from each other suggesting that eolian deposition is an important source of Pb to seawater and to ferromanganese crusts. This contrasts with the Atlantic and Southern Ocean where more intense deep water flow leads to isotopic gradients in FeMn crusts that do not reflect surface water conditions immediately above the crust. A mechanism is proposed which accounts for Pacific deepwater Pb being isotopically influenced by eolian deposition. Abstract Copyright (2002) Elsevier, B.V.
Year of Publication: 2002
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 06 Petrology, Sedimentary; Alkaline earth metals; Asia; Cenozoic; Clastic sediments; Clay; Cores; DSDP Site 576; Deep Sea Drilling Project; Ferromanganese crusts; IPOD; Isotope ratios; Isotopes; Lead; Leg 86; Loess; Marine sediments; Metals; North America; North Pacific; Oligocene; Pacific Ocean; Paleo-oceanography; Paleocene; Paleogene; Pb-206/Pb-204; Pb-207/Pb-204; Pb-208/Pb-204; Provenance; Radioactive isotopes; Red clay; Sediments; Sr-87/Sr-86; Stable isotopes; Strontium; Temporal distribution; Tertiary; Time factor; Volcanism; Wind transport
Coordinates: N301954 N301954 W1574954 W1574954
N322121 N322122 E1641633 E1641632
Record ID: 2002043380
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands