Geochemical and structural studies of the Lamont seamounts: seamounts as indicators of mantle processes

Fornari, Daniel J.; Perfit, Michael R.; Allan, James F.; Batiza, Rodey; Haymon, Rachel M.; Barone, Angela M.; Ryan, William B. F.; Smith, Terri L.; Simkin, Tom; Luckman, Mary Ann

doi:10.1016/0012-821x(88)90033-7

Cited by 112 publications

(77 citation statements)

References 49 publications

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“…The most likely explanation for the positive Eu anomaly is that it is a characteristic of the mantle source for these basalts. Similar positive Eu anomalies have been observed in some OIB (e.g., Tasmantid Seamounts; Eggins et al, 1991; Lanai, Hawaii; West et al, 1992), and in a few MORB (e.g., Jenner and Hertogen, 1986) and EPR near-axis seamount lavas (e.g., Bender et al, 1984;Fornari et al, 1988).…”

Section: Implications For Morb Sourcesupporting

confidence: 64%

“…Thus, while Site 843 basalts have some unusual geochemical characteristics, they are not distinguishable from either EPR T-MORB or seamount lavas on the basis of many incompatible element enrichments relative to N-MORB. Near-axis seamount lavas are not always geochemically different from MORB, but in some cases the seamount lavas are more primitive (Fornari et al, 1988). The freshest Site 843 rocks have CaO/Al 2 O 3 ratios of 0.76-0.79 (average for all samples is 0.73), which is typical of the global range of MORB (0.7-0.9;Klein and Langmuir, 1987).…”

Section: Are Site 843 Basalts Representative Of the Oceanic Crustmentioning

confidence: 98%

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Geochemistry and Petrology of Basalts from Leg 136, Central Pacific Ocean

King¹,

Waggoner²,

Garcia³

1993

Proceedings of the Ocean Drilling Program

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About 13 m of Cretaceous, tholeiitic basalt, ranging from normal (N-MORB) to transitional (T-MORB) mid-ocean-ridge basalts, was recovered at Ocean Drilling Program Site 843 west of the island of Hawaii. These moderately fractionated, aphyric lavas are probably representative of the oceanic basement on which the Hawaiian Islands were built. Whole-rock samples from parts of the cores exhibiting only slight, low-temperature, seawater alteration were analyzed for major element, trace element, and isotopic composition. The basalts are characterized by enrichment in the high field strength elements relative to N-MORB, by a distinct positive Eu anomaly, and by Ba/Nb and La/Nb ratios that are much lower than those of other crustal or mantle-derived rocks, but their isotope ratios are similar to those of present-day N-MORB from the East Pacific Rise. Hole 843A lavas are isotopically indistinguishable from Hole 843B lavas and are probably derived from the same source at a lower degree of partial melting, as indicated by lower Y/Nb and Zr/Nb ratios and by higher concentrations of light and middle rare earth elements and other incompatible elements relative to Hole 843B lavas. Petrographic and trace-element evidence indicates that the Eu anomaly was the result of neither Plagioclase assimilation nor seawater alteration. The Eu anomaly and the enrichments in Ta, Nb, and possibly U and K relative to N-MORB apparently are characteristic of the mantle source. Age-corrected Nd and Sr isotopic ratios indicate that the source for the lavas recovered at ODP Site 843 was similar to the source for Southeast Pacific MORB. An enriched component within the Cretaceous mantle source of these basalts is suggested by their initial 208 Pb/ 204 Pb-206 Pb/ 204 Pb and ε Nd -Pb/ Pb ratios. The Sr-Pb isotopic trend of Hawaiian post-shield and post-erosional lavas cannot be explained by assimilation of oceanic crust with the isotopic composition of the Site 843 basalts.

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Section: Implications For Morb Sourcesupporting

confidence: 64%

Section: Are Site 843 Basalts Representative Of the Oceanic Crustmentioning

confidence: 98%

Geochemistry and Petrology of Basalts from Leg 136, Central Pacific Ocean

King¹,

Waggoner²,

Garcia³

1993

Proceedings of the Ocean Drilling Program

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“…11.7 ridge-parallel normal faults deform them. Similar large offaxis seamounts, the Lamont Seamounts, have been discovered on the East Pacific Rise near to long-offset transform faults (Fornari et al 1988) , with a magmatically-active nearby ridge segment (Scheirer and Macdonald 1995). This similarity suggests that a long-offset transform fault may play a key role in transferring water from the seafloor to underneath the mantle, promoting melting.…”

Section: Rodrigues Segment (Rs)mentioning

confidence: 61%

Tectonic Background of Four Hydrothermal Fields Along the Central Indian Ridge

Okino

Nakamura

Sato

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Since the discovery of the Kairei hydrothermal field at the southernmost end of the Central Indian Ridge (CIR) in 2000, only four active hydrothermal vent fields have subsequently been discovered. These four hydrothermal fields show remarkable diversity in the chemical compositions of fluids and associated ecosystems. Focused geophysical mapping and rock sampling indicate that different tectonic setting constrains the different hydrothermal activity for each field. Two hydrothermal fields in the southern CIR are located on the axial rift-valley wall. The hydrogen-rich Kairei hydrothermal field at 25 19 0 S is constrained by both basaltic magmatism and detachment faulting that exhume ultramafic rocks on a shallow subsurface, whereas no evidence of ultramafic exposure is recognized in the typical mid-ocean ridge type Edmond hydrothermal field at 23 52 0 S. Two other hydrothermal fields have been newly discovered in the central CIR. The Solitaire field at 19 33 0 S is located about 2.6 km away from the neo-volcanic zone and is likely influenced by intra-plate volcanism. The Dodo field at 18 20 0 S is located at the center of the axial valley floor, where a basaltic sheet-lava flow buries the seafloor. The lava morphology and the existence of an adjacent large off-axis seamount support the idea that excess melt is supplied in this segment. The anomalous magmatism is likely influenced by mantle plume components or by a large-offset transform fault just north of the segment. The large diversity found in the four hydrothermal fields along the CIR provides important insights on the tectonic control of global hydrothermal systems.

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“…These observations suggest that transport of melts from the melting region to the site of olivine crystallization occurs without significant chemical exchange with the surrounding mantle. Finally, lavas recovered from near-axis seamounts record a wider range of magma compositions than are erupted along the adjacent ridge, including both more depleted and more enriched compositions (e.g., Batiza and Vanko, 1984;Fornari et al, 1988;Graham et al, 1988;Hekinian et al, 1989;Karsten et al, 1990;Niu and Batiza, 1997;Reynolds et al, 1992). These findings suggest that the seamount magmas bypass the welldeveloped magma chamber system, which tends to homogenize magmas formed from a heterogeneous source and through a range of melting conditions.…”

mentioning

confidence: 92%