Australia: The Land Where Time Began

A biography of the Australian continent 

Yilgarn Craton – Structure of Detrital Zircon Within about 3 Ga Metasedimentary Rocks: Elucidation of Hadean Source Terranes by Analysis of Principal Components

In this paper Thern & Nelson present the results of a multivariate approach they employed using a similarity matrix that had been derived from >5,500 U-Pb zircon analyses to investigate the complex and overlapping detrital zircon age structure within metasedimentary rocks of about 3 Ga from the Yilgarn Craton, Western Australia. They grouped detrital zircon analyses by their ²⁰⁷Pb/²⁰⁶Pb dates by the use of a robust chi-square grouping method which produced 74 age groups that were Yilgarn-wide from a pool of >3,500 analyses and that had been correlated between different sedimentary rocks. Then principal component analysis (PCA) was used on a calculated similarity matrix of >65 samples containing these age groups. The main age populations of the detrital zircons in the about 3 Ga metasedimentary rocks were indicated by PCA to have been derived from the Narryer and Yarlarweelor Gneiss Complexes. Age structure differences between those of >3.9 Ga zircon populations within the Mt Alfred metasedimentary rocks from those Mt. Narryer, Jack Hills and Maynard Hills localities are explained best by them being derived from 2 terranes of Hadean age which were amalgamated about 3.7 Ga.

Sources & Further reading  

Thern, E. R. and D. R. Nelson (2012). "Detrital zircon age structure within ca. 3 Ga metasedimentary rocks, Yilgarn Craton: Elucidation of Hadean source terranes by principal component analysis." Precambrian Research 214–215(0): 28-43.