Nd- and Pb-isotopic variations through the upper oceanic crust in DSDP/ODP Hole 504B, Costa Rica Rift

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doi: 10.1016/S0012-821X(01)00349-1
Author(s): Pedersen, Rolf B.; Furnes, Harald
Author Affiliation(s): Primary:
University of Bergen, Department of Geology, Bergen, Norway
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 189(3-4), p.221-235. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 50 refs.; illus., incl. 2 tables, sketch map
Summary: The DSDP/ODP Hole 504B, drilled in the 5.9 Ma southern flank of the Costa Rica Rift, represents the deepest section through modern ocean floor basaltic basement. The hole penetrates a 570 m thick volcanic zone, a 210 m thick transition zone of volcanic rocks and dykes, and 1056 m of dykes. A representative selection of these basalt types has been investigated with respect to Nd and Pb isotopes. The εNd of the basalts varies from 7.62 to 11.16. This range in the Nd-isotope composition represents about 67% of the total range reported for Pacific MORB. The Pb-isotope composition also shows significant variation, with 206Pb/204Pb varying from 17.90 to 18.82. The isotopic data show that a small volume of enriched mantle existed in the source. The large ranges in isotopic composition in a single drill hole demonstrate the importance of small-scale mantle heterogeneities in the petrogenesis of MORB. Fractional melting and extraction of small magma batches by channelled flow, and small, short-lived crustal magma reservoirs, with limited potential for mixing of the mantle derived magmas, are favored by these isotopic data. Abstract Copyright (2001) Elsevier, B.V.
Year of Publication: 2001
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Basalts; Cocos Plate; Costa Rica Rift; Crust; DSDP Site 504; Deep Sea Drilling Project; Dikes; East Pacific; Galapagos Rift; Geochemistry; HIMU; IPOD; Igneous rocks; Intrusions; Isotope ratios; Isotopes; Lead; Leg 111; Leg 137; Leg 140; Leg 148; Leg 69; Leg 70; Leg 83; Leg 92; Metals; Mid-ocean ridge basalts; Nazca Plate; Nd-144/Nd-143; Neodymium; Ocean Drilling Program; Oceanic crust; Pacific Ocean; Pb-206/Pb-204; Plate boundaries; Plate tectonics; Radioactive isotopes; Rare earths; Rift zones; Sea-floor spreading; Spreading centers; Stable isotopes; Upper crust; Volcanic rocks
Coordinates: N011335 N011338 W0834348 W0834357
Record ID: 2001062120
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands