Isotopic and Trace Element Composition of Basalts from Sites 556-559 and 561-564: Constraints on Some Processes Affecting Their Composition

Jenner, G.A.; Hertogen, J.; Sachtleben, Th.; Schminke, H.-U.

doi:10.2973/dsdp.proc.82.126.1985

Cited by 5 publications

(1 citation statement)

References 22 publications

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“…North of the Hayes Transform, basalts show increasing enrichments in (La/Sm) cn ratios as the Azores region is approached. Such variation in basalt geochemistry along with Sr-Nd-Pb isotopic evidence indicates depleted upper mantle south of the Hayes Transform and both depleted and enriched upper mantle north of the Hayes Transform (Schilling, 1975;White and Schilling, 1978;Schilling et al, 1983;Hamelin et al, 1984;Bougault et al, 1985;Drake et al, 1985;Dupré et al, 1985;Hertogen et al, 1985;Jenner et al, 1985;Rideout and Schilling, 1985;Weaver et al, 1985;Smith, 1994). Spidergrams (Fig.…”

Section: Trace-and Rare-earth-element Geochemistrymentioning

confidence: 93%

Geochemistry of basaltic rocks from the TAG hydrothermal mound (26°08'N), Mid-Atlantic Ridge

Smith¹,

Humphris²

1998

Proceedings of the Ocean Drilling Program

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Variably altered basalts, hydrothermal clays, and metabasaltic clasts were recovered during the Ocean Drilling Program (ODP) Leg 158 from the TransAtlantic Geotraverse (TAG) hydrothermal mound at 26°08′N, 44°49′W, on the Mid-Atlantic Ridge. These basaltic samples exhibit whole-rock chemical changes resulting from hydrothermal alteration of mid-ocean ridge basalt (MORB) at the edges of the TAG mound and within the stockwork zone. Relatively unaltered basalts are used to constrain the petrogenetic history of the magmas in the TAG region. The whole-rock compositions of basalts have relatively narrow ranges of Mg-numbers of 62.6-64.5, olivine compositions (Fo 85.8 −Fo 86.3), and (La/Sm) cn ratios of 0.66−0.73, but rather variable CaO/Al 2 O 3 ratios of 0.70−0.77 and Na 2 O contents of 2.29−2.73 wt%. These Leg 158 basaltic whole-rock compositions have major-, trace-, and rare-earth-element characteristics similar to the glasses from this region. Fractional crystallization modeling using pseudoternary projections and liquid lines of descent calculations indicate that the Leg 158 basalts have probably undergone moderate pressure fractionation of olivine, then olivine + plagioclase at 4 to 6 kb, followed by rapid ascent from the upper mantle with very short crustal residence times. Multiple parental melt compositions are indicated by partial melting and fractional crystallization models. Maximum extents of partial melting in the upper mantle are estimated to be between ~11% and ~25% which is a larger variation than near the Kane Transform (MARK) area at ~10 to ~15%. The maximum extents of partial melting along the Mid-Atlantic Ridge show an overall decline from the Azores hotspot region (38°N) to the region south of the Hayes Transform (33°N), the TAG region (26°N), and Mid-Atlantic Ridge near the Kane Transform (MARK) area (23°N). Melt production and accumulation processes along the TAG segment, however, provide variability on the local scale.

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Section: Trace-and Rare-earth-element Geochemistrymentioning

confidence: 93%

Geochemistry of basaltic rocks from the TAG hydrothermal mound (26°08'N), Mid-Atlantic Ridge

Smith¹,

Humphris²

1998

Proceedings of the Ocean Drilling Program

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Oceanic ridge crest processes

Rona¹

1987

Reviews of Geophysics

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Oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth, atmospheric and biologic sciences. This deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere, hydrosphere, atmosphere and biosphere, and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data. These techniques include crustal drilling with borehole logging (Deep Sea Drilling Project reports), high‐resolution bathymetry (Sea Beam, etc.), side‐scan sonar (SeaMARC I and II, GLORIA, etc.), imagery with video and photography, multichannel seismics, determination of water column properties (CTD with rosette sampler, etc.), and submersible applications.

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(Table 1) Sr and Nd isotopic compositions of basalts from DSDP Leg 82 Holes

Jenner,

Hertogen,

Sachtleben

et al. 1985

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Isotopic and Trace Element Composition of Basalts from Sites 556-559 and 561-564: Constraints on Some Processes Affecting Their Composition

Cited by 5 publications

References 22 publications

Geochemistry of basaltic rocks from the TAG hydrothermal mound (26°08'N), Mid-Atlantic Ridge

Geochemistry of basaltic rocks from the TAG hydrothermal mound (26°08'N), Mid-Atlantic Ridge

Oceanic ridge crest processes

(Table 1) Sr and Nd isotopic compositions of basalts from DSDP Leg 82 Holes

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