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Title: Lead isotopic studies of the Samail ophiolite, Oman

Abstract

The isotopic composition of Pb and the concentrations of U, Th, and Pb have been determined for samples from various lithologic units and massive sulfides of the Samail ophiolite. The observed /sup 206/Pb//sup 204/Pb ratios range from 17.90 to 19.06, /sup 207/Pb//sup 204/Pb ratios from 15.43 to 15.63, and /sup 208/Pb//sup 204/Pb from 37.66 to 38.78. In Pb isotopic evolution diagrams, the initial Pb isotopic compositions of most of the samples from the Samail ophiolite plot within the field of oceanic basalt, clearly distinct from island arc data, and define some of the least radiogenic Pb observed from oceanic rocks. Lead data from the Samail are compatible with a model involving magma generation from an oceanic mantle source and formation of the ophiolite at an oceanic spreading center. U--Th--Pb isotopic systematics demonstrate that vertical heterogeneity in the oceanic crust can be created through differential concentration of U, Th, and Pb during crystal fractionation and alteration at, or near, the spreading ridge. Calcite form amygdules in the ophiolite basalt has similar Pb isotopic composition to the igneous rocks, suggesting precipitation of the calcite from seawater which contained Pb derived mostly from the oceanic crust. Lead isotopic data on Fe--Cu sulfides aremore » also similar to the results from the igneous suite suggesting that the source of the sulfides is predominently from the oceanic crust. Lead data from serpentinized peridotite and a galena sample from below the ophiolite suggest that part of the serpentinization process and the formation of galena could involve addition of radiogenic Pb from either a continental source or from oceanic sediments.« less

Authors:
;
Publication Date:
Research Org.:
Department of Geological Sciences, University of California, Santa Barbara, Santa Barbara, California 93106
OSTI Identifier:
6353998
Resource Type:
Journal Article
Journal Name:
J. Geophys. Res.; (United States)
Additional Journal Information:
Journal Volume: 86:B4
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; OCEANIC CRUST; PETROGENESIS; OMAN; ARABIAN SEA; EARTH MANTLE; IGNEOUS ROCKS; ISOTOPE RATIO; LEAD 204; LEAD 206; LEAD 207; LEAD 208; MAGMA; SEA-FLOOR SPREADING; SULFIDES; THORIUM; URANIUM; ACTINIDES; ALPHA DECAY RADIOISOTOPES; ASIA; CHALCOGENIDES; EARTH CRUST; ELEMENTS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; HEAVY NUCLEI; HOURS LIVING RADIOISOTOPES; INDIAN OCEAN; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; LEAD ISOTOPES; METALS; MIDDLE EAST; NUCLEI; RADIOISOTOPES; ROCKS; SEAS; SECONDS LIVING RADIOISOTOPES; STABLE ISOTOPES; SULFUR COMPOUNDS; SURFACE WATERS; YEARS LIVING RADIOISOTOPES; 580100* - Geology & Hydrology- (-1989)

Citation Formats

Chen, J H, and Pallister, J S. Lead isotopic studies of the Samail ophiolite, Oman. United States: N. p., 1981. Web. doi:10.1029/JB086iB04p02699.
Chen, J H, & Pallister, J S. Lead isotopic studies of the Samail ophiolite, Oman. United States. https://doi.org/10.1029/JB086iB04p02699
Chen, J H, and Pallister, J S. 1981. "Lead isotopic studies of the Samail ophiolite, Oman". United States. https://doi.org/10.1029/JB086iB04p02699.
@article{osti_6353998,
title = {Lead isotopic studies of the Samail ophiolite, Oman},
author = {Chen, J H and Pallister, J S},
abstractNote = {The isotopic composition of Pb and the concentrations of U, Th, and Pb have been determined for samples from various lithologic units and massive sulfides of the Samail ophiolite. The observed /sup 206/Pb//sup 204/Pb ratios range from 17.90 to 19.06, /sup 207/Pb//sup 204/Pb ratios from 15.43 to 15.63, and /sup 208/Pb//sup 204/Pb from 37.66 to 38.78. In Pb isotopic evolution diagrams, the initial Pb isotopic compositions of most of the samples from the Samail ophiolite plot within the field of oceanic basalt, clearly distinct from island arc data, and define some of the least radiogenic Pb observed from oceanic rocks. Lead data from the Samail are compatible with a model involving magma generation from an oceanic mantle source and formation of the ophiolite at an oceanic spreading center. U--Th--Pb isotopic systematics demonstrate that vertical heterogeneity in the oceanic crust can be created through differential concentration of U, Th, and Pb during crystal fractionation and alteration at, or near, the spreading ridge. Calcite form amygdules in the ophiolite basalt has similar Pb isotopic composition to the igneous rocks, suggesting precipitation of the calcite from seawater which contained Pb derived mostly from the oceanic crust. Lead isotopic data on Fe--Cu sulfides are also similar to the results from the igneous suite suggesting that the source of the sulfides is predominently from the oceanic crust. Lead data from serpentinized peridotite and a galena sample from below the ophiolite suggest that part of the serpentinization process and the formation of galena could involve addition of radiogenic Pb from either a continental source or from oceanic sediments.},
doi = {10.1029/JB086iB04p02699},
url = {https://www.osti.gov/biblio/6353998}, journal = {J. Geophys. Res.; (United States)},
number = ,
volume = 86:B4,
place = {United States},
year = {Fri Apr 10 00:00:00 EST 1981},
month = {Fri Apr 10 00:00:00 EST 1981}
}