As is good known, the populace is most 4.6 billion years old. No rocks exist, however, that are older than most 3.8 billion years. Influenza A virus subtype H5N1 sedimentary stone department inwards the Jack Hills of western Australia, to a greater extent than than 3 billion years old, contains within it zircons that were eroded from rocks every bit quondam every bit most 4.3 billion years, making these zircons, called Jack Hills zircons, the oldest recorded geological textile on the planet.
In 2007 too 2008, 2 inquiry papers reported inwards the mag Nature that a suite of zircons from the Jack Hills included diamonds, requiring a radical revision of early on populace history. The papers posited that the diamonds formed, somehow, earlier the oldest zircons — that is, earlier 4.3 billion years agone — too and then were recycled repeatedly over a menses of 1.2 billion years during which they were periodically incorporated into the zircons yesteryear an unidentified process.
Now a squad of 3 researchers, 2 of whom are at the University of California, Riverside, has discovered using electron microscopy that the diamonds inwards inquiry are non diamonds at all but broken fragments of a diamond-polishing chemical compound that got embedded when the zircon specimen was prepared for analysis yesteryear the authors of the Nature papers.
“The diamonds are non indigenous to the zircons,” said Harry Green, a inquiry geophysicist too a distinguished professor of the Graduate Division at UC Riverside, who was involved inwards the research. “They are contamination. This, combined amongst the lack of diamonds inwards whatsoever other samples of Jack Hills zircons, strongly suggests that in that place are no indigenous diamonds inwards the Jack Hills zircons.”
“It occurred to us that a long-term history of diamond recycling amongst intermittent trapping into zircons would probable larn out to a greater extent than or less kind of microstructural tape at the interface betwixt the diamonds too zircon,” said Larissa Dobrzhinetskaya, a professional person researcher inwards the Department of populace Sciences at UCR too the commencement writer of the inquiry paper. “We reasoned that high-resolution electron microscopy of the textile should hold out able to distinguish whether the diamonds are indeed what they convey been believed to be.”
Using an intensive search amongst high-resolution secondary-electron imaging too transmission electron microscopy, the inquiry squad confirmed the presence of diamonds inwards the Jack Hills zircon samples they examined but could readily seat them every bit broken fragments of diamond glue that the master authors had used to shine the zircons for examination. They every bit good observed quartz, graphite, apatite, rutile, atomic reveal 26 oxides, feldspars too other low-pressure minerals unremarkably included into zircon inwards granitic rocks.
“In other words, they are contamination from polishing amongst diamond glue that was mechanically injected into silicate inclusions during polishing” Green said.
The inquiry was supported yesteryear a grant from the National Science Foundation.
Green too Dobrzhinetskaya were joined inwards the inquiry yesteryear Richard Wirth at the Helmholtz Centre Potsdam, Germany.
Dobrzhinetskaya too Green planned the inquiry project; Dobrzhinetskaya led the project; she too Wirth did the electron microscopy.