Assessing the preservation and provenance of Sr and Nd isotopic signatures in Cretaceous volcanic ash beds

Hannon, Jeffrey S.; Huff, Warren D.

doi:10.1016/j.lithos.2019.07.012

Cited by 4 publications

(5 citation statements)

References 56 publications

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“…Although it is possible that some grains may be detrital, few of them are rounded and previous analysis of the mineralogy of the bentonites we sampled showed the complete absence of detrital quartz and feldspar [15]. Zircon autocrysts, antecrysts and xenocrysts are also present throughout our different zircon populations.…”

Section: Introductionmentioning

confidence: 69%

“…Trace element signatures can be reliably traced to relative variations in crustal thickness and juvenility, whereas zircons provide a robust age distribution to track specific basement associations. The absence of detrital quartz or feldspar grains found in the bentonite beds sampled [15] is key to the magmatic origin of the grains we analyzed. Even in the case of analysis of only one bentonite bed within a particular formation (for example, one bed from the Cloverly) containing only a relatively small zircon population (35 grains), useful data bearing on magmatic provenance can be obtained.…”

Section: Discussionmentioning

confidence: 96%

“…Zircons were separated from four bentonite beds within the Campanian (84-72 Ma) Pierre Shale collected south of the Black Hills in South Dakota [15] and a total of 73 grains were analyzed at single spots in grain interiors excluding grain cores seen in cathodoluminescence. Nearly all these analyses have Campanian ages (Figure 4D).…”

Section: Bentonite U-pb Zircon Agesmentioning

confidence: 99%

“…The migration of magmatism across the suture zone and into Laurentian crust led to magmatism centered within thick Precambrian crust where a sub-lithospheric crustal reservoir developed, homogenizing whole rock 87 Sr/ 86 Sr and developing enhanced levels of differentiation (high Eu anomaly and Zr/TiO 2 ; [11,15,59]). This was likely a mixingassimilation-homogenization-storage (MASH) zone, as magma pooled at the Moho and began a long period of supra-subduction calc-alkaline pluton formation.…”

Section: Zircon Autocrysts Antecrysts and Xenocrysts And Migrating Magmatismmentioning

confidence: 99%

“…Within the zircon populations we analyzed, zircon age data in bentonites from all six formations we sampled are in accord with biostratigraphically-constrained ages [13,14]; these are autocrystic zircons that can be assigned to eruption of ash. There are also older zircons that are unlikely to be detrital in origin based on mineralogical characterization [15]: these can be xenocrysts, recording the ages of basement source rocks, assimilated country rocks, or older (unrelated) plutons through which younger magma was intruded and antecrysts that track early stages of magma crystallization related to the eruptions of ash that produced the bentonite beds.…”

Section: Introductionmentioning

confidence: 99%

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Tracking 40 Million Years of Migrating Magmatism across the Idaho Batholith Using Zircon U-Pb Ages and Hf Isotopes from Cretaceous Bentonites

et al. 2021

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Cretaceous strata preserved in Wyoming contain numerous large bentonite deposits formed from the felsic ash of volcanic eruptions, mainly derived from Idaho batholith magmatism. These bentonites preserve a near-continuous 40 m.y. chronology of volcanism and their whole-rock and mineral chemistry has been used to document igneous processes and reconstruct the history of Idaho magmatism as emplacement migrated across the Laurentian margin. Using LA-ICP-MS, we analyzed the U-Pb ages and Hf isotopic compositions of nearly 700 zircon grains from 44 bentonite beds from the Bighorn Basin, Wyoming. Zircon populations contain magmatic autocrysts and antecrysts which can be linked to the main pulses of the Idaho batholith and xenocrysts ranging from approx. 250 Ma to 1.84 Ga from country rocks and basement source terranes. Initial εHf compositions of Phanerozoic zircons are diverse, with compositions ranging from −26 to nearly +12. Based on temporal trends in zircon ages and geochemistry, four distinct periods of plutonic emplacement are recognized during the Mid- to Late Cretaceous that follow plutonic emplacement across the Laurentian suture zone in western Idaho and into western Montana with the onset of Farallon slab shallowing. Our data demonstrate the utility of using zircons in preserved tephra to track the regional-scale evolution of convergent margins related to terrane accretion and the spatial migration of magmatism related to changes in subduction dynamics.

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Section: Introductionmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 96%

Section: Bentonite U-pb Zircon Agesmentioning

confidence: 99%

Section: Zircon Autocrysts Antecrysts and Xenocrysts And Migrating Magmatismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tracking 40 Million Years of Migrating Magmatism across the Idaho Batholith Using Zircon U-Pb Ages and Hf Isotopes from Cretaceous Bentonites

et al. 2021

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Tectono‐magmatic division of the Late Ordovician (Sandbian) volcanism at the south‐western margin of Baltica using immobile trace elements: Relations to the plate movements in the Iapetus Palaeo‐Ocean

et al. 2019

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Immobile trace elements in K‐bentonites indicate three volcanic stages during the Sandbian Stage of the Late Ordovician: Early Grefsen is characterised by high‐Ti source magmas alternating with a few high‐Zr layers. Middle Grefsen is characterised by overall low‐Ti source magmas with multiple high‐Zr layers alternating with less frequent low‐Zr layers. Late Grefsen to Early Katian is characterised by a low content of all studied immobile trace elements (Ti, Zr, Nb, and Th). In all K‐bentonites, the Nb/Al2O3 ratio indicates subalkaline volcanism dominated by rhyolites. In the Early Grefsen stage, andesites and dacites occur. The TiO2/Al2O3 versus Zr/Al2O3 discrimination diagram suggests low‐ and high‐temperature magmatism. Low‐temperature magmatism may have occurred during subduction of water‐rich oceanic sediments in the frontal arc of Avalonia and high‐temperature magmatism during the overriding of a mid‐ocean ridge or hot spot. The coeval end of the volcanic record in Avalonia and Baltica may indicate the collision of Avalonia with a hypothetical continental crust within the Iapetus Ocean.

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Using zircon saturation thermometry of source magma in strongly altered volcanic ashes

Kiipli

2022

Acta Geochim

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Assessing the preservation and provenance of Sr and Nd isotopic signatures in Cretaceous volcanic ash beds

Cited by 4 publications

References 56 publications

Tracking 40 Million Years of Migrating Magmatism across the Idaho Batholith Using Zircon U-Pb Ages and Hf Isotopes from Cretaceous Bentonites

Tracking 40 Million Years of Migrating Magmatism across the Idaho Batholith Using Zircon U-Pb Ages and Hf Isotopes from Cretaceous Bentonites

Tectono‐magmatic division of the Late Ordovician (Sandbian) volcanism at the south‐western margin of Baltica using immobile trace elements: Relations to the plate movements in the Iapetus Palaeo‐Ocean

Using zircon saturation thermometry of source magma in strongly altered volcanic ashes

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