Editing Zircon (section)

==Radiometric dating==
[[File:Zircon grain (CL-SEM imaging).tiff|thumb|SEM-CL image of Zircon grain showing zonations and poly-cycles (core-rim structure)]]
Zircon has played an important role during the evolution of [[radiometric dating]]. Zircons contain trace amounts of [[uranium]] and [[thorium]] (from 10 [[Parts per million|ppm]] up to 1 wt%)<ref name="Jackson-2019" /> and can be dated using several modern analytical techniques. Because zircons can survive geologic processes like [[erosion]], transport, and even high-grade [[metamorphism]], they contain a rich and varied record of geological processes. Currently, zircons are typically dated by [[uranium-lead dating|uranium-lead]] (U-Pb), [[fission track dating|fission-track]], and U+Th/He techniques. Imaging the cathodoluminescence emission from fast electrons can be used as a prescreening tool for high-resolution [[Secondary ion mass spectrometry|secondary-ion mass spectrometry]] (SIMS) to image the zonation pattern and identify regions of interest for isotope analysis. This is done using an integrated cathodoluminescence and scanning electron microscope.<ref>{{Cite web|url=http://request.delmic.com/zircon-application-note |title=Zircons – Application Note |website=DELMIC |language=en |access-date=2017-02-10}}</ref> [[Detrital zircon geochronology|Zircons in sedimentary rock]] can identify the sediment source.<ref>{{cite journal |last1=Cawood |first1=P.A. |last2=Hawkesworth |first2=C.J. |last3=Dhuime |first3=B. |title=Detrital zircon record and tectonic setting |journal=Geology |date=October 2012 |volume=40 |issue=10 |pages=875–878 |doi=10.1130/G32945.1 |bibcode=2012Geo....40..875C|doi-access=free|hdl=10023/3575 |hdl-access=free }}</ref>

Zircons from [[Jack Hills]] in the [[Narryer Gneiss terrane]], [[Yilgarn craton]], [[Western Australia]], have yielded [[uranium-lead dating|U-Pb]] ages up to 4.404 billion years,<ref name="Wilde">{{cite journal |doi=10.1038/35051550 |pmid=11196637|title=Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago |journal=Nature |volume=409|issue=6817|pages=175–178|year=2001|last1=Wilde|first1=Simon A.|last2=Valley|first2=John W. |last3=Peck |first3=William H.|last4=Graham|first4=Colin M.|bibcode=2001Natur.409..175W|s2cid=4319774}}</ref> interpreted to be the age of crystallization, making them the [[oldest rock|oldest minerals]] so far dated on Earth. In addition, the [[oxygen]] [[isotope|isotopic]] compositions of some of these zircons have been interpreted to indicate that more than 4.3 billion years ago there was already liquid water on the surface of the Earth.<ref name="Wilde" /><ref>{{cite journal |doi=10.1038/35051557 |pmid=11196638 |title=Oxygen-isotope evidence from ancient zircons for liquid water at the Earth's surface 4,300 Myr ago |journal=Nature |volume=409|issue=6817|pages=178–181|year=2001|last1=Mojzsis|first1=Stephen J. |last2=Harrison |first2=T. Mark |last3=Pidgeon|first3=Robert T.|bibcode=2001Natur.409..178M |s2cid=2819082}}</ref><ref>{{Cite journal |last1=Valley |first1=JW |last2=Peck |first2=WH |last3=King |first3=EM |last4=Wilde |first4=SA |date=2002 |title=A cool early Earth |journal=Geology |volume=30 |issue=4 |pages=351–354|doi=10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2 |bibcode=2002Geo....30..351V }}</ref><ref>{{Cite journal |last1=Valley |first1=JW |last2=Lackey |first2=JS |last3=Cavosie |first3=AJ |date=2005 |title=4.4 billion years of crustal maturation: Oxygen isotopes in magmatic zircon. |journal=Contributions to Mineralogy and Petrology |volume=150 |pages=561–580|doi=10.1007/s00410-005-0025-8 |s2cid=53118854 }}</ref> This interpretation is supported by additional trace element data,<ref>{{cite journal|doi=10.1016/j.epsl.2008.05.032|title=Lithium in Jack Hills zircons: Evidence for extensive weathering of Earth's earliest crust|journal=Earth and Planetary Science Letters|volume=272|issue=3–4|pages=666–676 |year=2008 |last1=Ushikubo|first1=Takayuki|last2=Kita|first2=Noriko T.|last3=Cavosie|first3=Aaron J. |last4=Wilde |first4=Simon A.|last5=Rudnick|first5=Roberta L.|last6=Valley|first6=John W.|bibcode=2008E&PSL.272..666U}}</ref><ref>{{cite news |url=http://www.physorg.com/news132583481.html|title=Ancient mineral shows early Earth climate tough on continents |publisher=Physorg.com |date=June 13, 2008}}</ref> but is also the subject of debate.<ref>{{cite journal |doi=10.1016/j.epsl.2006.01.054 |title=Re-evaluation of the origin and evolution of >4.2 Ga zircons from the Jack Hills metasedimentary rocks|journal=Earth and Planetary Science Letters|volume=244|issue=1–2|pages=218–233 |year=2006 |last1=Nemchin |first1=A.|last2=Pidgeon |first2=R.|last3=Whitehouse|first3=M.|bibcode=2006E&PSL.244..218N}}</ref><ref>{{cite journal |doi=10.1016/j.epsl.2005.04.028 |title=Magmatic δ<sup>18</sup>O in 4400–3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean |journal=Earth and Planetary Science Letters|volume=235|issue=3–4|pages=663–681|year=2005|last1=Cavosie|first1=A.J.|last2=Valley|first2=J.W.|last3=Wilde|first3=S.A.|bibcode=2005E&PSL.235..663C}}</ref><ref>{{Cite journal |last1=Valley |first1=JW |last2=Cavosie |first2=AJ |last3=Ushikobo |first3=T |last4=Reinhardt |last5=Lawrence |first5=DF |last6=Larson |first6=DJ |last7=Clifton |first7=PH |last8=Kelly |first8=TF |last9=Wilde |first9=SA |last10=Moser |first10=DE |last11=Spicuzza |first11=MJ |date=2014 |title=Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography |journal=Nature Geoscience |volume=7 |issue=3 |pages=219–223|doi=10.1038/ngeo2075 |bibcode=2014NatGe...7..219V }}</ref> In 2015, "remains of [[Biotic material|biotic life]]" were found in 4.1-billion-year-old rocks in the Jack Hills of Western Australia.<ref name="AP-20151019">{{cite news|last=Borenstein|first=Seth|title=Hints of life on what was thought to be desolate early Earth|url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |date=19 October 2015|work=[[Excite (web portal)|Excite]]|location=Yonkers, NY|publisher=[[Mindspark Interactive Network]]|agency=[[Associated Press]]|url-status=dead|archive-url=https://web.archive.org/web/20151023200248/http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |archive-date=23 October 2015|access-date=8 October 2018}}</ref><ref name="PNAS-20151014-pdf">{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnke|first2=Patrick|last3=Harrison|first3=T. Mark|last4=Mao|first4=Wendy L.|author-link4=Wendy Mao |year=2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon|journal=Proceedings of the National Academy of Sciences |volume=112|issue=47|pages=14518–14521 |bibcode=2015PNAS..11214518B |doi=10.1073/pnas.1517557112 |pmc=4664351 |pmid=26483481|doi-access=free}}</ref> According to one of the researchers, "If [[life]] arose relatively quickly on [[Earth]] ... then it could be common in the [[universe]]."<ref name="AP-20151019" />