Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early geodynamo

Weiss, B. P.; Maloof, Adam C.; Tailby, Nicholas D.; Ramezani, Jahandar; Fu, R. R.; Hanus, Veronica; Trail, Dustin; Watson, E. Bruce; Harrison, T. Mark; Bowring, Samuel A.; Kirschvink, Joseph L.; Swanson‐Hysell, Nicholas L.; Coe, Robert S.

doi:10.1016/j.epsl.2015.07.067

Cited by 46 publications

(46 citation statements)

References 51 publications

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“…This alternate approach would produce a mean very similar to that originally reported by Weiss et al (2015) but with a much smaller confidence interval. We chose not to follow this approach since Fig.…”

supporting

confidence: 55%

“…Note: The first column gives the site name, the second column gives the number of directions, the third and fifth columns give the statistics that test for uniform distribution in declination and exponential distribution in inclination, respectively, around the mean, the fourth and sixth columns show whether a Fisher distribution can be rejected with 95% confidence based on each statistic (i.e., Mu and Me exceed critical values of 1.207 and 1.094, respectively). Using measurements from Weiss et al (2015). Note that the EHJH5, EHJH6, and EHJH7 values differ from those reported by Bono et al (2016).…”

Section: Fig S2contrasting

confidence: 38%

“…Sampling localities for individual cobbles sampled by Tarduno and Cottrell (2013) Dunn et al (2005), site 152 by Grange et al (2010), and from sites 01JH36, 01JH54, 01JH65, and W74 by Cavosie et al (2004). The positions of the three EHJH sites plotted differ by ~200 m from those in Weiss et al (2015) Fig. 1 due to a minor datum conversion error in the latter study.…”

Section: Fig S2mentioning

confidence: 99%

“…Table S3 with the following identification numbers: Bangemall sills (blue circles) = 1-11, Bangemall dyke (light blue circle) = 12, Yilgarn dykes (green circles) = 13-16; Jack Hills dyke = 17, Glenayle and Prenti dykes (purple circles) = 18-28. Stars show mean poles for all Warakurna rocks (orange) and mean pole for just Bangemall sills (blue) [the latter was used as the Warakurna mean direction in Weiss et al (2015)]. The Jack Hills dike VGP is at the edge of the population of Warakurna VGPs likely due to secular variation.…”

mentioning

confidence: 99%

“…These consist of clast high temperature (HT) directions from EHJH5 and clast and matrix HT directions from EHJH6 and EHJH7. Following Weiss et al (2015), we use the HT mean direction inferred for each clast that yielded multiple intra-clast specimens for EHJH5, while we considered each intra-clast specimen as a direction due to the small total number of specimens measured for EHJH7 (although using the clast means would not meaningfully change the results). Because a quantile-quantile test (Tauxe, 2010) shows that the EHJH6 directions are collectively non-Fisherian (Table S1), we calculate a mean direction…”

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confidence: 99%

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Reply to Comment on “Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early dynamo”

Weiss

Maloof

Harrison

et al. 2016

Earth and Planetary Science Letters

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supporting

confidence: 55%

Section: Fig S2contrasting

confidence: 38%

Section: Fig S2mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Reply to Comment on “Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early dynamo”

Weiss

Maloof

Harrison

et al. 2016

Earth and Planetary Science Letters

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Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

Lima

Weiss

2016

Geochem. Geophys. Geosyst.

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Useful paleomagnetic information is expected to be recorded by samples with moments up to three orders of magnitude below the detection limit of standard superconducting rock magnetometers. Such samples are now detectable using recently developed magnetic microscopes, which map the magnetic fields above room‐temperature samples with unprecedented spatial resolutions and field sensitivities. However, realizing this potential requires the development of techniques for retrieving sample moments from magnetic microscopy data. With this goal, we developed a technique for uniquely obtaining the net magnetic moment of geological samples from magnetic microscopy maps of unresolved or nearly unresolved magnetization. This technique is particularly powerful for analyzing small, weakly magnetized samples such as meteoritic chondrules and terrestrial silicate crystals like zircons. We validated this technique by applying it to field maps generated from synthetic sources and also to field maps measured using a superconducting quantum interference device (SQUID) microscope above geological samples with moments down to 10−15 Am2. For the most magnetic rock samples, the net moments estimated from the SQUID microscope data are within error of independent moment measurements acquired using lower sensitivity standard rock magnetometers. In addition to its superior moment sensitivity, SQUID microscope net moment magnetometry also enables the identification and isolation of magnetic contamination and background sources, which is critical for improving accuracy in paleomagnetic studies of weakly magnetic samples.

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Aluminum in zircon as evidence for peraluminous and metaluminous melts from the Hadean to present

Trail

Tailby

Wang

et al. 2017

Geochem Geophys Geosyst

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Zircon structurally accommodates a range of trace impurities into its lattice, a feature which is used extensively to investigate the evolution of silicate magmas. One key compositional boundary of magmas is defined by whether the molar ratio of Al2O3/(CaO + Na2O + K2O) is larger or smaller than unity. Here we report ∼800 Al in zircon concentrations from 19 different rocks from the Lachlan Fold Belt (southeastern Australia), New England (USA), and Arunachal leucogranites (eastern Himalaya) with Al2O3/(CaO + Na2O + K2O) whole rock values that range from 0.88 to 1.6. Zircons from peraluminous rocks yield an average Al concentration of ∼10 ppm, which distinguishes them from crystals found in metaluminous rocks (∼1.3 ppm). This difference is related to the materials involved in the melting, assimilation, and/or magma differentiation processes; for example, magmas that assimilate Al‐rich material such as metapelites are expected to produce melts with elevated alumina activities, and thus zircons with high Al concentrations. These observations are applied to the Archean and Hadean Jack Hills detrital zircon record. Detrital Archean zircons, with ages from about 3.30 to 3.75 Ga, yield Al in zircon concentrations consistent with origins in peraluminous rocks in ∼8% of the cases (n = 236). A single zircon from the pre‐3.9 Ga age group (n = 39) contains elevated Al contents, which suggests that metaluminous crustal rocks were more common than peraluminous rocks in the Hadean. Weathered material assimilated into these Hadean source melts was not dominated by Al‐rich source material.

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Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early geodynamo

Cited by 46 publications

References 51 publications

Reply to Comment on “Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early dynamo”

Reply to Comment on “Pervasive remagnetization of detrital zircon host rocks in the Jack Hills, Western Australia and implications for records of the early dynamo”

Ultra-high sensitivity moment magnetometry of geological samples using magnetic microscopy

Aluminum in zircon as evidence for peraluminous and metaluminous melts from the Hadean to present

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