Galapagos hot spot--spreading center system. 2. /sup 87/Sr//sup 86/Sr and large ion lithophile element variations (85 /sup 0/W--101 /sup 0/W)

Journal Article · Fri Dec 10 00:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB087iB13p10838· OSTI ID:6151664

Verma, S P; Schilling, J

Thirty eight samples of basalts dredged from the Galapagos spreading center (GSC) between 85 /sup 0/W and 101.5 /sup 0/W longitudes have been analyzed for K, Rb, Cs, Ba, and Sr contents as well as for /sup 87/Sr//sup 86/Sr ratios. Basalts between 85 /sup 0/W and 89 /sup 0/W segment of the GSC range from 0.7025 to 0.7028 in /sup 87/Sr//sup 86/Sr and those between 95.5 zW and 101.5 /sup 0/W range from 0.7026 to 0.7027. These basalts are characterized by LREE-depleted patterns. Basalts from 89 /sup 0/W to 95.5 /sup 0/W segment having slightly LREE-depleted to LREE-enriched patterns ((La/Sm)/sub E.F./ between 0.8 and 2.4) range from 0.7027 to 0.7031 in /sup 87/Sr//sup 86/Sr. The longitudinal /sup 87/Sr//sup 86/Sr variation shows a maximum at about 92 /sup 0/W, where the GSC is nearest to Darwin Island. The alkali and alkaline earth elements as well as several element ratios also show maxima in their longitudinal profiles, but these occur at about 91 /sup 0/W. The apparent shift of /sup 87/Sr//sup 86/Sr maximum with respect to that of the trace elements may be related to differences in the degree of partial melting. The highest /sup 87/Sr//sup 86/Sr from the GSC is only slightly lower than the highest /sup 87/Sr//sup 86/Sr for tholeiitic basalts from the Galapagos Archipel-ago. Several possible hypotheses have been examined to account for these geochemical and Sr iso-topic variations. In the light of the presently available data, the most promising explanation seems to be a binary mixing of hot spot (or plumetype) material with the source of 'normal' mid-ocean ridge basalts and resulting rift propagation. Both end-members seem to be heterogeneous, and therefore it is at present difficult to put severe constraints on this binary mixing. Nevertheless, the flow pattern of mantle material from the hot spot does not appear to be radial but is preferentially channeled along the 91 /sup 0/W and 92.5 /sup 0/W fracture zones toward the rift.

• Research Organization: Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881
• OSTI ID: 6151664
• Journal Information: J. Geophys. Res.; (United States), Vol. 87:B13
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
HOT SPOTS
CHEMICAL COMPOSITION
PACIFIC OCEAN
BARIUM
BASALT
CESIUM
OCEANIC CRUST
POTASSIUM
RUBIDIUM
SEA-FLOOR SPREADING
STRONTIUM 86
STRONTIUM 87
ALKALI METALS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
BETA DECAY RADIOISOTOPES
EARTH CRUST
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
METALS
NUCLEI
RADIOISOTOPES
ROCKS
SEAS
STABLE ISOTOPES
STRONTIUM ISOTOPES
SURFACE WATERS
VOLCANIC ROCKS
580500* - Oceanography- (1980-1989)