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The Earliest Piece of the Earth (created 2005)

Zircons Are Forever A Cool Early Earth The Earliest Piece of the Earth

John Valley - Home Page

Early Earth & Zircon Research - UW-Madison (March 2014)

References

Peck WHValley JWWilde SA, and Graham CM (2000) Ion microprobe Evidence for Pre-4.4 Ga Continental Crust and Low Temperature Water/Rock Interaction. Geol. Soc. Am. Abstr, vol 32, no. 7, p. 376.

 Wilde SA, Valley JW, Peck WH and Graham CM (2001) Evidence from Detrital Zircons for the Existence of Continental Crust and Oceans on the Earth 4.4 Gyr Ago. Nature. 409: 175-178.

 Peck WH, Valley JW, Wilde SA, and Graham CM (2001) Oxygen isotope ratios and rare earth elements in 3.3 to 4.4 Ga zircons: Ion microprobe evidence for high d18continental crust and oceans in the Early Archean. Geochimica et Cosmochimica Acta, vo. 64, no 22, pp 4215-4229

Valley JW, Peck WH, King EM, Wilde SA (2002) A Cool Early Earth, Geology. 30: 351-354.

 Cavosie AJ, Wilde SA, Liu D, Valley JW, Weiblen PW (2004) Internal zoning and U-Th-Pb chemistry of the jack Hills detrital zircons: a mineral record of early Archean to mesoproterozoic magmatism. Precambrian Research, 135:231-279.

 Valley JW (2003) Oxygen Isotopes in Zircon. Reviews in Mineralogy and Geochemistry: v. 53, 2003, Chapter 13, pp. 343-385.

 Cavosie AJ, Valley JW, Wilde SA, and EIMF (2005) Magmatic d18O in 4400-3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean.

 Valley JW (2005) A Cool Early Earth? Scientific American, October 2005, 58-65.

 Valley JW, Lackey JS, Cavosie AJ, Clechenko CC, Spicuzza MJ, Basei MAS, Bindeman IN, Ferreira VP, Sial AN, King EM, Peck WH, Sinha AK, Wei CS (2005) 4.4 billion years of crustal maturation: oxygen isotopes in magmatic zircon. Contr. Mineral. Petrol. DOI 10.1007/s00410-005-0025-8.


      1. Outcrop photographs of the Jack Hills, Western Australia showing the outcrops where the 4.4Ga zircon sample was collected from interlayered red quartzites and metaconglomerate. (SA Wilde, unpublished photographs)
     
photo, Australian landscape
photo, Australian landscape
outcrop
outcrop

     

photo,Valley, Cavosie, Wiled

2a. Outcrop of the oldest known sample of the Earth, a 4.4 Ga detrital zircon (sample W74) in the Jack Hills metaconglomerate, Eranondoo Hill, Jack Hills, Western Australia. From l to r: John Valley, University of Wisconsin-Madison; Aaron Cavosie, University of Wisconsin-Madison; Simon Wilde, Curtin University.

     

photo, two vehicles

2b. Dirt track leading to Eranondoo Hill, site of 4.4 Ga zircon discovery, Jack Hills, Western Australia.

photo, flat tire

2c. Hazards of fieldwork in the outback.


     

photo, cookhouse interior

3a. Geologists study maps in the cookhouse. Mileura Station, Western Australia.

 

photo, building with bales

3b. Bales of wool, Mileura Station, Western Australia.

 
     

photo, buildings in Australia

4a. Sheep shearer's quarters, Mileura, Station, Western Australia.

photo, kangaroo in field

4b. South of theJack Hills, Western Australia.

photo, sunset, Australia

4c. Mileura Station, Western Australia.

 

     
5. Cathodoluminescence image of the oldest known material from the Earth, a single crystal of zircon from the Jack Hills metaconglomerate, Western Australia. Concentric, magmatic growth zoning is shown about the crystal core. The crystallization age of 4.40Ga was determined by ion microprobe. A high oxygen isotope ratio of +7.4 was measured in the core of this grain with a second ion microprobe. (JW Valley, unpbd image) crystal of zircon

     
U-Pb Concordia 6. U-Pb Concordia showing age of 4.404 at better than 99% concordance. (Wilde et al. 2001)

     
     
Surface 2 of zircon W74/2-36 8. Surface 2 of zircon W74/2-36. The U-Pb age of 4.4 billion years was determined by ion microprobe from the spot shown.

     
9. Cathodoluminescence image of surface 1 of zircon W74/2-36. Concentric, magmatic growth zoning is shown about the crystal core. The crystallization age of 4.40Ga was determined by ion microprobe from surface 2. A high oxygen isotope ratio of +7.4 was measured in the core of this grain with a second ion microprobe. (Wilde et al. 2001) surface 1 of zircon

     
surface 2 of zircon 10. Cathodoluminescence image of surface 2 of zircon W74/2-36. Concentric, magmatic growth zoning is shown about the crystal core. Eight ion microprobe pits are shown. The crystallization age of 4.40Ga was determined from the leftmost spot. A high oxygen isotope ratio of +7.4 was measured in the core of this grain with a second ion microprobe. (Wilde et al. 2001)

     
11. Cathodoluminescence image of surface 2 of zircon W74/2-36. Concentric, magmatic growth zoning is shown about the crystal core. The crystallization age of 4.40Ga (4004+-4Ma) was determined by ion microprobe. A high oxygen isotope ratio of +7.4 was measured in the core of this grain with a second ion microprobe. (Wilde et al. 2001) surface 2 of zircon

     
microprobe image with title of paper 12. (Peck et al. 2000, 2001)

     
     
graphic showing U-Pb Concordia for zircons 14. U-Pb Concordia for zircons from sample W74 with ages from 3.3 to 4.4 Ga. (Peck et al. 2000, 2001)

     
15. Optical interferometer image of surface 1 of zircon W74/2-36 after ion microprobe analysis of U-Pb, oxygen isotope ratio and rare earth elements. Five micron deep pits are from REE and oxygen analysis. Shallower pits are from U-Pb. (Peck et al. 2000, 2001) Optical interferometer image of surface 1 of zircon

     
Oxygen isotope analyses of zircons 16. Oxygen isotope analyses of zircons from sample W74 showing clustering of ages and the range of oxygen isotope ratio for each age. Values of d18O above 6.5 ‰ indicate alteration of protoliths by liquid water at low temperatures. The standard data for KIM5 shows the expected values of primitive magmas from the Earth’s mantle. Values higher than this are seen for each time period. (Peck et al. 2000, 2001)

     
17. Rare earth element content in 3.3 to 3.6 Ga zircons from W74. (Peck et al. 2000, 2001) Rare earth element content in 3.3 to 3.6 Ga zircons

     
Rare earth element content in 3.3 to 3.6 Ga zircons 18. Rare earth element content in ~4.0 to 4.15 Ga zircons from W74. (Peck et al. 2000, 2001)

     
19. Back scattered electron (BSE) and cathodoluminescence (CL) images of surface 2 of zircon W74/2-36. Three inclusions of SiO2 (black spots, 10-20 microns in diameter) and 8 ion microprobe pits from U-Pb analysis are seen in BSE. The 4.40 Ga spot is farthest to the left. The CL image shows concentric, magmatic growth zoning. (Peck et al. 2000, 2001) Back scattered electron (BSE) and cathodoluminescence (CL) images of surface 2 of zircon W74/2-36

     
20. U-Pb analyses of surfaces 1 and 2 of zircon W74/2-36. (Peck et al. 2000, 2001) U-Pb analyses of surfaces 1 and 2 of zircon W74/2-36

     
Surface 1 of zircon 21. Surface 1. (Peck et al. 2000, 2001)

     
22. Surface 2. (Peck et al. 2000, 2001) Surface 2 of zircon

 
Order of analysis of ion microprobe analysis of zircon W74/2-36 23. Order of analysis of ion microprobe analysis of zircon W74/2-36. (Peck et al. 2000, 2001)

   

24. Surface 1, REE and oxygen isotope analysis. (Peck et al. 2000, 2001)

Surface 1, REE and oxygen isotope analysis

   
Surface 1, REE and oxygen isotope analysis 25. Surface 1, REE and oxygen isotope analysis. (Peck et al. 2000, 2001)

     
26. Oxygen isotope ratios and U-Pb Concordia for zircons from sample W74. (Peck et al. 2000, 2001) Oxygen isotope ratios and U-Pb Concordia for zircons from sample W74

     
Timeline of the first billion years of Earth history 27. Timeline of the first billion years of Earth history. (Peck et al. 2000, 2001)

28. Timeline of major events in the history of the Earth. No samples of rock are known from the first 500 million years and only a few crystals of zircon have been identified from this era. The oldest zircon provides evidence of continental crust, low surface temperatures, and liquid water that suggest an early Earth that was more similar to the present than previously has been thought. (Andree Valley, Madison, Wisconsin) Timeline of major events in the history of the Earth

graphic described in caption #29

29. Crystallization age (U-Pb) and oxygen isotope ratio (d18O) for Archean magmatic zircons. Distribution of magmatic d18O values does not change throughout the Archean. Most magmas had a primitive d18O value similar to that in the mantle today ("mantle zircon"), but some zircon values are as high as 7.5‰. High-d18O zircons and host magmas resulted from melting of protoliths that were altered by interaction with liquid water at low temperatures near surface of Earth (see text). Timeline (inset, lower right) shows: (1) accretion of the Earth, (2) formation of the Moon and the Earth’s core, (3) minimum age of liquid water based on high d18O zircon, (4) Acasta gneiss, and (5) Isua metasedimentary rocks. (Valley et al. 2002)


histograms 30. Histograms of d18O. A: Olivine from mantle xenoliths and Hawaiian basalts. B: Zircon xenocrysts from kimberlites in S. Africa. C: Zircons from igneous rocks of Superior province, Canada. D: Ion microprobe analyses of single zircons from Jack Hills, Western Australia. The Jack Hills zircons (D) are higher in d18O than the mantle. Such high d18O values indicate that the protolith of granitic magmas experienced low temperature interaction with liquid water in a near surface environment (Valley et al. 2002)

graphic described in caption #31 31. Estimates of meteorite impact rate for first two billion years of Earth history. Two hypotheses are shown: exponential decay of impact rate (dashes, and a cool early Earth/ late heavy bombardment (solid curve, this study). In either model, spikes occurred owing to isolated large impacts. Evidence for liquid water comes from high-d18O zircons (>4.4 Ga to >4.0 Ga) and sedimentary rocks (Isua 3.8-3.6 Ga). The cool early Earth hypothesis (solid curve) suggests that impact rates had dropped precipitously by 4.4 Ga, consistent with relatively cool conditions and liquid water on the surface of the Earth. (Valley et al. 2002)

graphic described in caption #32

32. Artist’s rendering of a Cool Early Earth 4.4 billion years ago. Recent evidence from single crystals of zircon suggests that surface temperatures were relatively low and that liquid water would have formed oceans rather than a thick steam-rich atmosphere (Valley et al. 2002). Such oceans could have promoted the evolution of life. The hypothesis of a Cool Early Earth contrasts with earlier ideas that magma covered the Earth, which lead to the first 500 million years of Earth history being named "Hadean" (hell-like). (Graphic: Andrée Valley and Mary Diman)