Effects of submarine alteration on K-Ar dating of deep-sea igneous rocks

Seidemann, David E.

doi:10.1130/0016-7606(1977)88<1660:eosaok>2.0.co;2

Cited by 36 publications

(12 citation statements)

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“…Second, most samples are abundantly vesiculated, which indicates that outgassing occurred upon eruption. And, finally, the samples do not contain significant amounts of (altered) glass and/or olivine, which are potential sources of remaining excess argon in submarine basalts [Dalrymple and Moore, 1968;Seidemann, 1977Seidemann, , 1978. As a result, we may use an atmospheric 40 Ar/ 36 Ar value of 295.5 for the calculation of the 40 Ar/ 39 Ar plateau ages, as is confirmed in the 40 Ar/ 36 Ar intercepts calculated from the isochrons.…”

Section: Methodsmentioning

confidence: 99%

Short‐lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

Koppers

Staudigel

Pringle

et al. 2003

Geochem Geophys Geosyst

223

280

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[1] South Pacific intraplate volcanoes have been active since the Early Cretaceous. Their HIMU-EMI-EMII mantle sources can be traced back into the West Pacific Seamount Province (WPSP) using plate tectonic reconstructions, implying that these distinctive components are enduring features within the Earth's mantle for, at least, the last 120 Myr. These correlations are eminent on the scale of the WPSP and the South Pacific Thermal and Isotopic Anomaly (SOPITA), but the evolution of single hot spots emerges notably more complicated. Hot spots in the WPSP and SOPITA mantle regions typically display intermittent volcanic activity, longevities shorter than 40 Myr, superposition of hot spot volcanism, and motion relative to other hot spots. In this review, we use 40 Ar/ 39 Ar seamount ages and Sr-Nd-Pb isotopic signatures to map out Cretaceous volcanism in the WPSP and to characterize its evolution with respect to the currently active hot spots in the SOPITA region. Our plate tectonic reconstructions indicate cessation of volcanism during the Cretaceous for the Typhoon and Japanese hot spots; whereas the currently active Samoan, Society, Pitcairn and Marquesas hot spots lack long-lived counterparts in the WPSP. These hot spots may have become active during the last 20 Myr only. The other WPSP seamount trails can be only ''indirectly'' reconciled with hot spots in the SOPITA region. Complex age distributions in the Magellan, Anewetak, Ralik and Ratak seamount trails would necessitate the superposition of multiple volcanic trails generated by the Macdonald, Rurutu and Rarotonga hot spots during the Cretaceous; whereas HIMU-type seamounts in the Southern Wake seamount trail would require 350-500 km of hot spot motion over the last 100 Myr following its origination along the Mangaia-Rurutu ''hotline'' in the Cook-Austral Islands. These observations, however, violate all assumptions of the classical Wilson-Morgan hot spot hypothesis, indicating that long-lived, deep and fixed mantle plumes cannot explain the intraplate volcanism of the South Pacific region. We argue that the observed short-lived and discontinuous intraplate volcanism has been produced by another type of hot spot-related volcanism, as opposed to the strong and continuous Hawaiian-type hot spots. Our results also indicate that other geological processes (plate tension, hotlines, faulting, wetspots, self-propagating volcanoes) may act in conjunction with hot spot volcanism in the South Pacific. In all these scenarios, intraplate volcanism has to be controlled by ''broad-scale'' events giving rise to multiple closely-spaced mantle plumelets, each with a distinct isotopic signature, but only briefly active and stable over geological time. It seems most likely that these plumelets originate and dissipate at very shallow mantle depths, where they may shoot off as thin plumes from the top of a ''superplume'' that is present in the South Pacific mantle. The absence of clear age progressions in most

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Section: Methodsmentioning

confidence: 99%

Short‐lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

Koppers

Staudigel

Pringle

et al. 2003

Geochem Geophys Geosyst

223

280

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“…The former effect can result in discordant (young) ages whereby the latter effect can result in anomalously old ages [ Sinton and Duncan , 1998]. Submarine igneous rocks in particular, present problems due to effects associated with hydrothermal alteration and submarine weathering [e.g., Dalrymple and Moore , 1968; Funkhauser et al , 1968; Dymond , 1970; Seidemann , 1977; McDougall and Harrison , 1999].…”

Section: Problems With the Current Sw Pacific Paradigmmentioning

confidence: 99%

New SW Pacific tectonic model: Cyclical intraoceanic magmatic arc construction and near‐coeval emplacement along the Australia‐Pacific margin in the Cenozoic

Whattam

Malpas²,

Ali³

et al. 2008

Geochem Geophys Geosyst

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[1] Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55-50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous-Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40-34 Ma and in Northland, New Zealand, around 24-21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65-60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59-58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous-Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N-S) along the entire eastern margin of the Australian Plate. These ''infant arc'' ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc-Australian Plate collision. Subduction inception was the result of subsidence of older MORB-like lithosphere generated within an extensive ''back arc basin'' to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back-thrust beneath each ophiolite during its emplacement.

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“…Other complications encountered in applying the K-^r technique to the dating of submarine volcanic rocks may arise from the fact that glassy submarine lavas may contain excess 40Ar, due to the retention of mantle-derived Ar in magma erupted under high hydrostatic pressure [e.g., Dalrymple and Moore, 1968;Dalrymple and Lanphere, 1969;Dymond, 1970;Aumento, 1971]. Metasomatic addition of K, derived from seawater, to grain surfaces [Melson and Thompson, 1973;Seidemann, 1977] may lead to erroneously young K-Ar age determinations. [1981a].…”

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confidence: 99%

Evolution of the Walvis Ridge‐Rio Grande Rise Hot Spot System: Implications for African and South American Plate motions over plumes

O’Connor¹,

Duncan²

1990

J. Geophys. Res.

380

212

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Crystallization ages of volcanic rocks, dredged or drilled from the Walvis Ridge (ten sites) and the Rio Grande Rise (one site), have been determined by the 40Ar/39Ar incremental heating technique. The fundamentally age‐progressive distribution of these basement ages suggests a common hot spot source for volcanism on the island of Tristan da Cunha, along the Walvis Ridge and Rio Grande Rise, and for the formation of the continental flood basalts located in Namibia (Africa) and Brazil (South America). The Walvis Ridge‐Rio Grande Rise volcanic system evolved along a section of the South Atlantic spreading‐axis, as the African and South American plates migrated apart, astride, or in close proximity to, an upwelling plume. Reconstructions of the spatial relationship between the spreading‐axis, the Tristan hot spot, and the evolving Walvis Ridge‐Rio Grande Rise volcanic feature show that, at about 70 Ma, the spreading‐axis began to migrate westward, away from the hot spot. The resulting transition to intraplate hot spot volcanism along the Walvis Ridge (and associated termination of Rio Grande Rise formation) also involved a northward migration of previously formed African seafloor over the hot spot. Rotation parameters for African motion over fixed hot spots (i.e., absolute motion) have been recalculated such that the predicted trail of the Tristan hot spot agrees with the distribution of radiometric and fossil basement ages along the Walvis Ridge. African absolute motion has been extended to the South and North American plates, by the addition of relative motion reconstruction poles.

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Effects of submarine alteration on K-Ar dating of deep-sea igneous rocks

Cited by 36 publications

References 0 publications

Short‐lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

Short‐lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism?

New SW Pacific tectonic model: Cyclical intraoceanic magmatic arc construction and near‐coeval emplacement along the Australia‐Pacific margin in the Cenozoic

Evolution of the Walvis Ridge‐Rio Grande Rise Hot Spot System: Implications for African and South American Plate motions over plumes

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