Hematite and Mn oxide (U-Th)/He dates from the Buckskin-Rawhide detachment system, western Arizona: Gaining insights into hematite (U-Th)/He systematics

Clicks: 3
ID: 295086
2014
Free PDF
Article Quality & Performance Metrics
Overall Quality
Not rated
Combines reader engagement with the AI quality analysis. This article has not been analysed, so there is no overall score — reader engagement is measured and shown alongside.
AI Quality Assessment
Not analyzed
Readership in this journal
Emerging

Ranked #2,110 of 8,486 articles by views in american journal of science

Most read Least read

Bar heights use a square-root scale. Only the 120 most-read articles are drawn; the journal has 8,486 in total.

Mint this article as an NFT
Not yet minted

Create a permanent, verifiable on-chain record of this article on the Scimatic Network. The NFT is held in your Journament account, and you can withdraw it to your own wallet at any time.

5 SUSD one-off · no wallet required
Sign in to mint
Abstract
In this paper, we use several analytical methods in an effort to better understand the systematics of the (U-Th)/He chronometer in hematite and manganese oxides. ^4^He diffusion data from a polycrystalline hematite sample is consistent with diffusion from hematite crystals with a range of sizes similar to those directly observed in sample material. Combined with a compilation of hematite He diffusion data from previous studies, this supports the interpretation that in general crystal size is a primary control on He retentivity in hematite. ^4^He/^3^He diffusion data from a single fragment of a larger hematite crystal imply the presence of multiple diffusion domains smaller than the observed size of the crystal fragment, which may be related to cracks, inclusions, or other internal features, as well as higher concentrations of ^4^He in smaller domains. We use kinetic values determined in this and other studies and measurements of hematite crystal size in each dated sample to estimate approximate closure temperatures for each sample, most of which range from 140 to 240 °C. Relationships between minor element and parent nuclide concentrations and (U-Th)/He dates measured in aliquots of some analyzed hematite samples suggest that, in some cases, U and Th are concentrated in interstitial phases other than hematite. We identify two processes responsible for much of the dispersion in hematite dates from single samples. Removal of U- and Th-rich interstitial phases from analyzed material during sample preparation or analysis leaves behind unsupported ^4^He implanted in hematite crystals. This removal results in apparent (U-Th)/He dates artificially older than the time of hematite He closure. A smaller source of dispersion that is likely to still be significant in some samples can be attributed to the high He diffusivities of observed interstitial phases, which do not retain implanted He. (U-Th)/He dating of hematite from upper and lower-plate rocks in the Buckskin and Rawhide detachment fault system of western Arizona yields ages that coincide with the timing of rapid extension along the detachment fault. Comparisons of estimated hematite closure temperatures and hematite sample ages to data from other studies of the Buckskin-Rawhide detachment system lead us to conclude that hematite dates record rapid cooling that followed detachment zone mineralization. Mn oxide (U-Th)/He dates are interpreted as formation ages of minerals formed by hydrothermal fluids that circulated through upper-plate rocks after cessation of extension along the detachment fault. Overall, we find that (U-Th)/He dating of hematite and Mn oxide minerals are promising methods for obtaining temporal information about the formation and cooling of these common secondary phases.
Reference Key
openalex_W2313420325 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors N. S. Evenson, Peter W. Reiners, J.E. Spencer, David L. Shuster
Journal american journal of science
Year 2014
DOI
10.2475/10.2014.01
URL
https://ajs.scholasticahq.com/article/65658.pdf
Keywords Keywords not found

Citations

No citations found. To add a citation, contact the admin at info@scimatic.org

Comments

No comments yet. Be the first to comment on this article.