40Ar/39Ar dating of basaltic rocks and the pitfalls of plagioclase alteration

Jiang, Qiang; Jourdan, Fred; Olierook, Hugo K.H.; Merle, Renaud; Vérati, Chrystèle; Mayers, Celia

doi:10.1016/j.gca.2021.08.016

Cited by 23 publications

(6 citation statements)

References 79 publications

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“…The K/Ca ratio ranges from 0.0009 in the oldest sample (KM1609‐D11‐1 = 117.20 Ma) to 0.0459 in the youngest sample (KM1609‐D3‐12 = 52.19 Ma) with the exception of one sample that has exceptionally high K/Ca ratio of 0.3180 (KM1609‐D10‐9 = 65.01 Ma). This increase in K relative to Ca in the plagioclases (which probably did not originally vary much among samples) likely reflects a progressive addition of K during sericitization (Jiang et al., 2021; Verati & Jourdan, 2013) over tens of millions of years resulting in increasingly lower 40 Ar/ 39 Ar ages. Prolonged fluid flow has been demonstrated by other studies (Fisher & Becker, 2000; Stein & Stein, 1994) and our results further demonstrate the long period over which oceanic crust remains permeable and can undergo alteration.…”

Section: Resultsmentioning

confidence: 94%

“…All ages younger than 83.7 Ma (the end of the CNS) are interpreted as an alteration age because EB's oceanic crust was entirely formed during the CNS, and all samples that are younger than this age cutoff also show signs of alteration or discordance in their degassing patterns. This includes disturbed age spectra that may or may not yield an age plateau due to alteration or 39 Ar or 37 Ca recoil (Schaen et al., 2021) or variable K/Ca patterns and age spectra in plagioclase analyses likely due to partial sericitization (Jiang et al., 2021; Verati & Jourdan, 2013). Some plagioclase samples appear to yield reliable age spectra with age plateaus containing more than 50% of the released 39 Ar (K) (e.g., KM1609‐D10‐09 or D07‐01) but are too young for the region as mentioned above (Figures 4c and 4d), or have ages conflicting with other samples collected at the same dredge location (e.g., KM1609‐D7; Table 1).…”

Section: Resultsmentioning

confidence: 99%

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Rapid Formation of the Ellice and Osbourn Basins and Ontong Java Nui Breakup Kinematics

Davidson

Koppers

Konter

2023

Geochem Geophys Geosyst

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Breakup of the proposed greater Ontong Java Nui large igneous province during the Cretaceous Normal Superchron can be constrained by the opening of the Ellice Basin (EB) separating the Ontong Java and Manihiki Plateaus and the Osbourn Basin separating the Manihiki and Hikurangi Plateaus. Dating of recovered dredged samples using plagioclase 40Ar/39Ar and zircon U/Pb geochronology methods indicates that spreading was well underway in the EB by 118 Ma with full spreading rates up to 3X faster than any observed today of 30–45 cm/yr and spreading likely continued until 112‐108 Ma. Ellice Basin samples show diverse geochemical affinities ranging from mid‐ocean ridge basalt (MORB) or Ontong Java‐like to more enriched OIB‐like. Pb and Nd isotopes from six samples contain varying influences from Pacific MORB and possibly Ontong Java. The geochemistry shows a lack of a clear mantle plume influence despite EB's close temporal and spatial relationship to Ontong Java, while some data resemble the Louisville Seamounts. This compositional diversity complements morphological differences among dredge sites and shows that both in situ MORB and younger overprinted features related to the nearby Tuvalu Seamounts were sampled. 40Ar/39Ar geochronology confirms the age of International Ocean Discovery Program Site U1365 near the Osbourn Trough (OT) to be 102.60 ± 0.26 Ma (2σ, n = 18). This age constrains the timing of a spreading reorientation event observed in the OB to coincide with a global plate reorganization event around 105 Ma and estimates the cessation of spreading at the OT to 96 Ma.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Rapid Formation of the Ellice and Osbourn Basins and Ontong Java Nui Breakup Kinematics

Davidson

Koppers

Konter

2023

Geochem Geophys Geosyst

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“…6), consisting of 42% of 39 Ar released, followed by an extended high temperature/excess Ar recoil pattern. The remaining plagioclase separates (n = 7) were marred by multiple excess Ar domains, coupled with low-degree sericitization that resulted in discordant age spectrums (e.g., Jiang et al, 2021). In total, three samples produced age determinations with plateau ages containing at least 40% of the 39 Ar argon released (Table 1).…”

Section: Ar/ 39 Ar Geochronologymentioning

confidence: 99%

New insights into the age and origin of two small Cretaceous seamount chains proximal to the Northwestern Hawaiian Ridge

et al. 2023

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The Northwestern Hawaiian Ridge is an age-progressive volcanic chain sourced from the Hawaiian mantle plume. Proximal to the Northwestern Hawaiian Ridge are several clusters of smaller seamounts and ridges with limited age constraints and unknown geodynamic origins. This study presents new bathymetric data and 40Ar/39Ar age determinations from lava flow samples recovered by remotely operated vehicle (ROV) from two east–west-trending chains of seamounts that lie north of the Pūhāhonu and Mokumanamana volcanoes. The previously unexplored Naifeh Chain (28°48′N,167°48′W) and Plumeria Chain (25°36′N, 164°35′W) contain five volcanic structures each, including three guyots in the Naifeh Chain. New 40Ar/39Ar age determinations indicate that the Naifeh Chain formed ca. 88 Ma and the Plumeria Chain ca. 85 Ma. The Cretaceous ages, coupled with a perpendicular orientation of the seamounts relative to absolute Pacific plate motion at that time, eliminate either a Miocene Hawaiian volcanic arch or Cretaceous mantle-plume origin. The seamounts lie on oceanic crust that is modeled to be 10–15 Ma older than the corresponding seamounts. Here, two models are put forth to explain the origin of these enigmatic seamount chains as well as the similar nearby Mendelssohn Seamounts. (1) Diffuse lithospheric extension results in the formation of these seamounts until the initiation of the Kula-Pacific spreading center in the north at 84–79 Ma, which alleviates the tension. (2) Shear-driven upwelling of enriched mantle material beneath young oceanic lithosphere results in an age-progressive seamount track that is approximately perpendicular to the spreading ridge. Here we show that all sampled seamounts proximal to the Northwestern Hawaiian Ridge are intraplate in nature, but their formations can be attributed to both plume and plate processes.

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“…However, K-Ar and Rb-Sr systematics can easily be modified by alteration 15 , with previous workers recognising that the K contents of dated phlogopite in the main diatreme complex were "anomalously low" and indicative of partial chloritization 12 . The extensive alteration of K-bearing minerals means they are likely unsuitable as geochronometers for Argyle 16 . Although there is relatively fresh phlogopite in some of the lamproite dykes 17 , dating it with high-precision 40 Ar/ 39 Ar has proved challenging due to the presence of excess radiogenic Ar.…”

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confidence: 99%

Emplacement of the Argyle diamond deposit into an ancient rift zone triggered by supercontinent breakup

Olierook,

Fougerouse,

Doucet

et al. 2023

Nat Commun

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Argyle is the world’s largest source of natural diamonds, yet one of only a few economic deposits hosted in a Paleoproterozoic orogen. The geodynamic triggers responsible for its alkaline ultramafic volcanic host are unknown. Here we show, using U-Pb and (U-Th)/He geochronology of detrital apatite and detrital zircon, and U-Pb dating of hydrothermal titanite, that emplacement of the Argyle lamproite is bracketed between 1311 ± 9 Ma and 1257 ± 15 Ma (2σ), older than previously known. To form the Argyle lamproite diatreme complex, emplacement was likely driven by lithospheric extension related to the breakup of the supercontinent Nuna. Extension facilitated production of low-degree partial melts and their migration through transcrustal corridors in the Paleoproterozoic Halls Creek Orogen, a rheologically-weak rift zone adjacent to the Kimberley Craton. Diamondiferous diatreme emplacement during (super)continental breakup may be prevalent but hitherto under-recognized in rift zones at the edges of ancient continental blocks.

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40Ar/39Ar dating of basaltic rocks and the pitfalls of plagioclase alteration

Cited by 23 publications

References 79 publications

Rapid Formation of the Ellice and Osbourn Basins and Ontong Java Nui Breakup Kinematics

Rapid Formation of the Ellice and Osbourn Basins and Ontong Java Nui Breakup Kinematics

New insights into the age and origin of two small Cretaceous seamount chains proximal to the Northwestern Hawaiian Ridge

Emplacement of the Argyle diamond deposit into an ancient rift zone triggered by supercontinent breakup

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