Steven B Shirey

 
 

The Archean Eon (2500 myr to nearly 4000 myr before the present) was a time when the continental crust was first differentiated and stabilized. It marked the transition to modern-style plate tectonics and was perhaps the most important period for the formation of Earth’s mineral wealth (e.g. gold, nickel, copper, uranium, platinum, chromium, and diamonds).

This USGS map depicts the ages of the last tectonothermal event that the crust of the Earth has experienced. Archean crust is shown in orange. While not a large percentage of the crust by volume, Archean crust occupies a central position as a nucleus for continental growth and as a site for the production of mineral resources.

Shirey SB and Richardson SH, 2011, Start of the Wilson Cycle at 3 Ga shown by diamonds from subcontinental mantle. Science 333, 434-436.

Shirey, S.B., Kamber, B.S., Whitehouse, M.J., Mueller, P.A., and Basu, A.R., 2008, A review of the isotopic and trace element evidence for mantle and crustal processes in the Hadean and Archean: Implications for the onset of plate tectonic subduction, in Condie, K., and Pease, V., eds., When Did Plate Tectonics Begin on Earth?, Volume 440: Boulder, CO, Geological Society of America Special Paper, p. 1-29.

Wilson, A.H., Shirey, S.B., and Carlson, R.W., 2003, Archean ultra-depleted komatiites formed by hydrous melting of cratonic mantle: Nature, v. 423, p. 858-861.

Shirey, S.B., Carlson, R.W., Richardson, S.H., Menzies, A., Gurney, J.J., Pearson, D.G., Harris, J.W., and Wiechert, U., 2001, Archean emplacement of eclogitic components into the lithospheric mantle during formation of the Kaapvaal Craton: Geophysical Research Letters, v. 28, p. 2509-2512.

Pearson, D.G., Snyder, G.A., Shirey, S.B., Taylor, L.A., Carlson, R.W., and Sobolev, N.V., 1995, Archaean Re-Os age for Siberian eclogites and constraints on Archaean tectonics: Nature, v. 374, p. 711-713.

Schiotte, L., Hansen, B.T., Shirey, S.B., and Bridgwater, D., 1993, Petrological and whole rock isotopic characteristics of tectonically juxtaposed Archaean gneisses in the Okak area of the Nain Province, Labrador; relevance for terrane models: Precambrian Research, v. 63, p. 293-323.

Barrie, C.T., and Shirey, S.B., 1991, Nd- and Sr-isotope systematics for the Kamiskotia-Montcalm area; implications for the formation of late Archean crust in the western Abitibi Subprovince, Canada: Canadian Journal of Earth Sciences, v. 28, p. 58-76.

Bedard, L.P., Stern, R.A., Hanson, G.N., and Shirey, S.B., 1990, Petrogenesis of mantle-derived, LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids) in southwestern Superior Province; discussion and reply: Canadian Journal of Earth Sciences, v. 27, p. 1135-1137.

Walker, R.J., Shirey, S.B., Hanson, G.N., Rajamani, V., and Horan, M.F., 1989, Re-Os, Rb-Sr, and O isotopic systematics of the Archean Kolar schist belt, Karnataka, India: Geochimica et Cosmochimica Acta, v. 53, p. 3005-3013.

Stern, R.A., Hanson, G.N., and Shirey, S.B., 1989, Petrogenesis of mantle-derived, LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids) in southwestern Superior Province: Canadian Journal of Earth Sciences, v. 26, p. 1688-1712.

Rajamani, V., Shirey, S.B., and Hanson, G.N., 1989, Fe-rich Archean tholeiites derived from melt-enriched mantle sources; evidence from the Kolar schist belt, South India: Journal of Geology, v. 97, p. 487-501.

Lambert, D.D., Morgan, J.W., Walker, R.J., Shirey, S.B., Carlson, R.W., Zientek, M.L., and Koski, M.S., 1989, Rhenium-osmium and samarium-neodymium isotopic systematics of the Stillwater Complex: Science, v. 244, p. 1169-1174.

Walker, R.J., Shirey, S.B., and Stecher, O., 1988, Comparative Re-Os, Sm-Nd and Rb-Sr isotope and trace element systematics for Archean komatiite flows from Munro Township, Abitibi Belt, Ontario: Earth and Planetary Science Letters, v. 87, p. 1-12.

Shirey, S.B., and Hanson, G.N., 1986, Mantle heterogeneity and crustal recycling in Archean granite-greenstone belts; evidence from Nd isotopes and trace elements in the Rainy Lake area, Superior Province, Ontario, Canada: Geochimica et Cosmochimica Acta, v. 50, p. 2631-2651.

Rajamani, V., Shivkumar, K., Hanson, G.N., and Shirey, S.B., 1985, Geochemistry and petrogenesis of amphibolites, Kolar schist belt, South India; evidence for komatiitic magma derived by low percentages of melting of the mantle: Journal of Petrology, v. 26, p. 92-123.

Shirey, S.B., and Hanson, G.N., 1984, Mantle-derived Archaean monzodiorites and trachyandesites: Nature, v. 310, p. 222-224.

Shirey, S.B., 1984, The origin of Archean crust in the Rainy Lake area, Ontario.

Shirey, S.B., and Hanson, G.N., 1983, Granitic rocks and metasediments in Archean crust, Rainy Lake area, Ontario; Nd isotope evidence for mantle-like Sm/ Nd sources, in Ashwal Lewis, D., and Card Kenneth, D., eds., Workshop on a cross section of Archean crust., Volume 83-03: LPI Technical Report: Houston, TX, United States, Lunar and Planetary Institute, p. 83-86.

Relevant publications

Separation of the early enriched reservoir (EER) of Boyet and Carlson leads to creation of depleted mantle in the middle of the current OIB field. Much more depleted mantle starts to emerge perhaps around 2.7 billion years ago, perhaps in response to creation of large volumes of Neoarchean continental crust.

An important focus of Archean work for me has always been the Neoarchean, a critical time when major volumes of crust were produced and the transition to modern plate tectonics may have begun. The best exposed Neoarchean terrane in the world is in the Superior Province (left) of the Canadian Shield where I have ongoing projects on >2685 million year old mantle samples erupted with diamondiferous lamprophyres  and using geoneutrinos from the SNO+ neutrino detector in Sudbury, ON to look at the current distribution of U and Th in the crust. The Wawa lamprophyre project involves Ontario Geological Survey geologists John Ayer and Anne Wilson, Derek Wyman from University of Sydney and DTM postdoc Wendy Nelson. The geoneutrino project involves Roberta Rudnick and William McDonough from the University of Maryland and Steve Dye from Hawaii Pacific University.

Terrane map of the Superior Province from John Percival, reproduced from a figure in Pease et al (2008). The Wawa area is shown by the red star.

Field shots of mantle xenoliths in lamprophyric magma. Note the high proportion of xenoliths in some outcrops and the degree of rounding of some xenoliths.

The 2.90 to 2.65 Gyr old Michipicoten greenstone belt contains abundant 2.685 Gyr old lamprophyre dikes that host diamonds and ultramafic xenoliths. These dikes are the oldest diamond bearing rocks on Earth and one of the oldest xenolith suites. Note that many of these xenoliths are websteritic and that the degree of recrystallization is significant. We are using the Re-Os system and PGE in an attempt to see through the recrystallization.

The lamprophyres all have elevated initial Os isotopic compositions at circa 2.7 Ga showing that they are from subduction-enriched wedge mantle. Modern lamprophyres from the Mexican Volcanic Belt (MVB; Lassiter and Luhr, 2001) extrapolated to the Archean (purple) show a similar extent of enrichment. The four xenoliths analyzed have very dissimilar compositions. Xenolith 4, with an initial isotopic composition like the lamprophyres is probably a xenolith inherited from the enriched mantle wedge. Xenoliths 1 and 2 have compositions like 2.7 Ga komatiites (Puchtel et al., 2004; Gangopadhyay et al., 2005) or peridotitic xenoliths from Kirkland Lake (Pearson et al., 1995). These likely represent ultramafic rocks that are samples of, or are equilibrated with, the 2.7 Ga mantle added to the Neoarchean crust as it differentiated and stabilized. Xenolith 3 has a lower initial Os isotopic composition and a much higher Os abundance typical of mantle peridotite. Its composition is significantly lower than 2.7 chondritic mantle and equal to or lower than the composition of 2.9 to 3.0 Ga chondritic mantle.

Re-Os isotopic data on a preliminary suite of websterites and lamprophyres. Both lamprophyres and xenoliths have very low Re/Os that makes them ideal for using Os initial ratios for petrogenesis. From Shirey et al. Fall 2009 AGU.

Current Work in the Superior Province

Archean mantle evolution traces global Earth evolution and crustal growth