Lead isotopic studies of the Samail ophiolite, Oman

Journal Article · Fri Apr 10 04:00:00 EST 1981 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB086iB04p02699· OSTI ID:6353998

Chen, J H; Pallister, J S

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.

• Research Organization: Department of Geological Sciences, University of California, Santa Barbara, Santa Barbara, California 93106
• OSTI ID: 6353998
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 86:B4; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
ACTINIDES
ALPHA DECAY RADIOISOTOPES
ARABIAN SEA
ASIA
CHALCOGENIDES
EARTH CRUST
EARTH MANTLE
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INDIAN OCEAN
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LEAD 204
LEAD 206
LEAD 207
LEAD 208
LEAD ISOTOPES
MAGMA
METALS
MIDDLE EAST
NUCLEI
OCEANIC CRUST
OMAN
PETROGENESIS
RADIOISOTOPES
ROCKS
SEA-FLOOR SPREADING
SEAS
SECONDS LIVING RADIOISOTOPES
STABLE ISOTOPES
SULFIDES
SULFUR COMPOUNDS
SURFACE WATERS
THORIUM
URANIUM
YEARS LIVING RADIOISOTOPES