U–Pb geochronology of baddeleyite from the Belleview metadiabase: Age and geotectonic implications for the Negaunee Iron Formation, Michigan

Pietrzak-Renaud, Natalie J.; Davis, Don W.

doi:10.1016/j.precamres.2014.05.018

Cited by 17 publications

(5 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, supposedly age-diagnostic sedimentary textures, like stromatolite fabrics, have lost favour among Precambrian biostratigraphers as body fossil records have gained in popularity and abundance. Although simple leiospheres and other microscopic organic remains are known from Archean sedimentary rocks (Javaux et al, 2010), the oldest biostratigraphically significant fossils are macroscopic organic-walled forms known from Paleoproterozoic rocks (Han and Runnegar, 1992;Javaux and Lepot, 2018), now dated to c. 1870 Ma (Fralick et al, 2002;Schneider et al, 2002;Pietrzak-Renaud and Davis, 2014). These simple coils and spirals, similar in appearance to Grypania spiralis (e.g., Walter et al, 1976;Sharma and Shukla, 2009), are not diagnostically eukaryotic in affinity.…”

Section: Palaeontological Constraintsmentioning

confidence: 99%

A template for an improved rock-based subdivision of the pre-Cryogenian timescale

Shields

Strachan

Porter

et al. 2021

JGS

View full text Add to dashboard Cite

The geological time scale before 720 Ma uses rounded absolute ages rather than specific events recorded in rocks to subdivide time. This has led increasingly to mismatches between subdivisions and the features for which they were named. Here we review the formal processes that led to the current time scale, outline rock-based concepts that could be used to subdivide pre-Cryogenian time and propose revisions. An appraisal of the Precambrian rock record confirms that purely chronostratigraphic subdivision would require only modest deviation from current chronometric boundaries, removal of which could be expedited by establishing event-based concepts and provisional, approximate ages for eon-, era- and period-level subdivisions. Our review leads to the following conclusions: 1) the current informal four-fold Archean subdivision should be simplified to a tripartite scheme, pending more detailed analysis, and 2) an improved rock-based Proterozoic Eon might comprise a Paleoproterozoic Era with three periods (early Paleoproterozoic or Skourian, Rhyacian, Orosirian), Mesoproterozoic Era with four periods (Statherian, Calymmian, Ectasian, Stenian) and a Neoproterozoic Era with four periods (pre-Tonian or Kleisian, Tonian, Cryogenian and Ediacaran). These proposals stem from a wide community and could be used to guide future development of the pre-Cryogenian timescale by international bodies.

show abstract

Section: Palaeontological Constraintsmentioning

confidence: 99%

A template for an improved rock-based subdivision of the pre-Cryogenian timescale

Shields

Strachan

Porter

et al. 2021

JGS

View full text Add to dashboard Cite

show abstract

“…Although regional geologists have already adopted more active tectonic frameworks for the IFs of the Superior region (e.g., Fralick et al., 2002; 2017; Hoffman, 1987; Schneider et al., 2002), transgressive continental margin shelf environments (aka. “transgressive passive margins”) are still discussed in recent literature for “Superior” style and ∼1.88 Ga IFs (Cawood & Hawkesworth, 2015; Craddock, et al., 2018; Egglseder, et al., 2017; Groves & Santosh, 2020; Hiatt et al., 2015; Konhauser et al., 2017; Lechte & Wallace, 2015; Pietrzak‐Renaud & Davis, 2014; Pufahl et al., 2014; Raye et al., 2015; Rodrigues et al., 2019; Schröder & Warke, 2016). Regardless of the choice of exact tectonic setting, be it localized tectonics, extensional tectonism across the Superior Craton or accretionary tectonics related the amalgamation of Laurentia (e.g., Heaman et al., 2009; Whitmeyer & Karlstrom, 2007), here evidence is presented that highlights the dynamic nature of Superior style IFs and supports the conclusion that massive IFs across the GOE span a diversity of tectonic settings.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

A New Depositional Framework for Massive Iron Formations After the Great Oxidation Event

Eyster

Brengman

Nichols

et al. 2021

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Abundant global oxygen is crucial for macroscopic life on Earth today, yet the tempos and triggers of ancient oxygenation are unknown. Iron formations (originally defined as rocks with >15 wt. % iron; James, 1954) hold important clues to the early evolution of Earth's atmosphere and biosphere, yet questions about their genesis remain. In particular: (a) are all massive iron formations (IFs) deposited in broadly similar depositional and geochemical settings; and (b) what drives their episodic deposition? The purpose of this work is to assess these questions with a case study coupling facies-based sedimentological and stratigraphic approaches for the ∼1.88 Ga Gogebic Range exposed near Lake Superior, USA (Michigan-Wisconsin), one of a few preserved post-Great Oxidation Event (GOE) massive iron deposits.Massive IFs (∼10 6 Gigatons) occur only in the Precambrian (e.g., Bekker et al., 2014;Konhauser et al., 2017). When examining the geologic record, the largest volumes of preserved IFs span the Late Archean to

show abstract

“…An additional possible source of discordance in baddeleyite U-Pb TIMS analysis is the incorporation of zircon overgrowths (which are subjected to Pb loss; Davidson and van Breeman, 1988;Rioux et al, 2010;Pietrzak-Renaud and Davis, 2014) or surrounding common-Pb-bearing phases in the extracted volume. This is not an issue in FIB-TIMS as such features can be removed using the FIB instrument prior to U-Pb analysis (Fig.…”

Section: Isotopic Heterogeneity In Phalaborwa Baddeleyitementioning

confidence: 99%

Highly accurate dating of micrometre-scale baddeleyite domains through combined focused ion beam extraction and U–Pb thermal ionization mass spectrometry (FIB-TIMS)

et al. 2020

View full text Add to dashboard Cite

Abstract. Baddeleyite is a powerful chronometer of mafic magmatic and meteorite impact processes. Precise and accurate U–Pb ages can be determined from single grains by isotope dilution thermal ionization mass spectrometry (ID-TIMS), but this requires disaggregation of the host rock for grain isolation and dissolution. As a result, the technique is rarely applied to precious samples with limited availability (such as lunar, Martian, and asteroidal meteorites and returned samples) or samples containing small baddeleyite grains that cannot readily be isolated by conventional mineral separation techniques. Here, we use focused ion beam (FIB) techniques, utilizing both Xe+ plasma and Ga+ ion sources, to liberate baddeleyite subdomains directly, allowing their extraction for ID-TIMS dating. We have analysed the U–Pb isotope systematics of domains ranging between 200 and 10 µm in length and from 5 to ≤0.1 µg in mass. In total, six domains of Phalaborwa baddeleyite extracted using a Xe+ plasma FIB (pFIB) yield a weighted mean 207Pb∕206Pb age of 2060.1±2.5 Ma (0.12 %; all uncertainties 2σ), within uncertainty of reference values. The smallest extracted domain (ca. 10×15×10 µm) yields an internal 207Pb∕206Pb age uncertainty of ±0.37 %. Comparable control on cutting is achieved using a Ga+-source FIB instrument, though the slower speed of cutting limits potential application to larger grains. While the U–Pb data are between 0.5 % and 13.6 % discordant, the extent of discordance does not correlate with the ratio of material to ion-milled surface area, and results generate an accurate upper-intercept age in U–Pb concordia space of 2060.20±0.91 Ma (0.044 %). Thus, we confirm the natural U–Pb variation and discordance within the Phalaborwa baddeleyite population observed with other geochronological techniques. Our results demonstrate the FIB-TIMS technique to be a powerful tool for highly accurate in situ 207Pb∕206Pb (and potentially U–Pb in concordant materials) age analysis, allowing dating of a wide variety of targets and processes newly accessible to geochronology.

show abstract

U–Pb geochronology of baddeleyite from the Belleview metadiabase: Age and geotectonic implications for the Negaunee Iron Formation, Michigan

Cited by 17 publications

References 20 publications

A template for an improved rock-based subdivision of the pre-Cryogenian timescale

A template for an improved rock-based subdivision of the pre-Cryogenian timescale

A New Depositional Framework for Massive Iron Formations After the Great Oxidation Event

Highly accurate dating of micrometre-scale baddeleyite domains through combined focused ion beam extraction and U–Pb thermal ionization mass spectrometry (FIB-TIMS)

Contact Info

Product

Resources

About