Archean Plate Tectonics Isotopic Evidence from Samples of

Archean Plate Tectonics: Isotopic Evidence from Samples of the Lithospheric Mantle to the Upper Crust Steven B Shirey Department of Terrestrial Magnetism Carnegie Institution of Washington

DEPTH ISOTOPIC DATA Pb-Pb Array for MORB-OIB CRUSTAL EVIDENCE Sialic rocks with juvenile isotopes Enriched Os in wet komatiites O isotopes in magmatic zircon INFERENCE OCEANIC SLAB RECYCLING OCEANIC ARCS WITH START OF CONTINENTAL ARCS EARLY RELATIVELY COOL MAGMATISM MANTLE LITHOSPHERE EVIDENCE Low-T O isotopes in eclogites C & N isotopes in diamond + Os isotopes in sulfide inclusions MIF sulfur in sulfide inclusions SUBDUCTION IMPRINT EVIDENT

Current mantle heterogeneity, especially the Pb-Pb array for MORB-OIB supports Paleoarchean mantle recycling. (Davies, JGR 1984) (Hart & Gaetani, CMP 2006)

(Davies, EPSL 2002)

(Davies, EPSL 2002)

Nd and Hf isotope data on Archean crustal rocks used to require separation on an early crustal component. This is no longer the case. (Vervoort & Blichert-Toft, GCA 2001)

An Early Depleted Reservoir (EDR) has been proposed for the Earth. All Archean crust would come from this reservoir. (Boyet & Carlson, Science, 2005)

EDR of Boyet & Carlson (Bennett, Treatise on Geochemistry, 2004; with additions)

(Bennett, Treatise on Geochemistry, 2004)

EDR of Boyet & Carlson (Bennett, Treatise on Geochemistry, 2004; with additions)

EDR of Boyet & Carlson CRUSTAL EVOLUTION (Harrison et al, Science, 2004; with additions)

Isotopic heterogeneity mantle 4. 3 Ga reservoir (Kamber et al, CMP 2003; with additions)

(Valley et al, CMP, 2005)

(modified from Stachel et al, Elements, 2005)

Peridotite Re-Os shows the cratonic lithosphere is Archean (Carlson et al, 1998 -2002; James and Fouch, 2002) Most sulfide inclusions are late Archean (Shirey et al. , GRL, 2001)

Re, trace elements and oxygen correlate with eclogite groups

Oxygen, Re-Os and REE allow eclogites to be placed into an Archean oceanic lithosphere section

Re-Os whole rock systematics give a scattered Archean age Same for other localities and some other isotope systems (e. g. Nd, Pb)

U-Pb age on zircon supports Re-Os age

(modified from original fig by Schmitz et al, 2004)

Diamond Stable Isotopes (separate symbols are E-Types & fibrous diamonds)

MIF Sulfur (Mojsis et al. , GCA, 2003) (Farquhar et al. , Science, 2000) An Archean tracer of surficial sulfur

Sulfide inclusions in Orapa diamonds have surface S J. Farquhar et al. , Science 298, 2369 -2372 (2002)

Eclogitic Sulfides incident light Peridotitic Sulfides incident light 20 μm SE SE CL transmitted

Panda pipe, Slave Craton Age = 3520± 170 Ma (Isoplot model 1 MSWD = 0. 46) Os. IR = 0. 1093± 0. 0001 (Westerlund, Shirey, Richardson, Carlson, Harris, Gurney, CMP, 2006 in press)

Archean (3. 5 Ga) example Cenozoic example Mixing of subduction fluids with peridotite in the mantle wedge (Westerlund, Shirey, Richardson, Carlson, Harris, Gurney, CMP in press) (Widom, Kepezhinskas, and Defant, Chemical Geology, 2003)

DEPTH ISOTOPIC DATA Pb-Pb Array for MORB-OIB CRUSTAL EVIDENCE Sialic rocks with juvenile isotopes Enriched Os in wet komatiites O isotopes in magmatic zircon INFERENCE OCEANIC SLAB RECYCLING OCEANIC ARCS WITH START OF CONTINENTAL ARCS EARLY RELATIVELY COOL MAGMATISM MANTLE LITHOSPHERE EVIDENCE Low-T O isotopes in eclogites C & N isotopes in diamond + Os isotopes in sulfide inclusions MIF sulfur in sulfide inclusions SUBDUCTION IMPRINT EVIDENT