WHEN DID PLATE TECTONICS BEGIN ON PLANET EARTH?
CONTENTS 1 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 2 A TRACE ELEMENT PERSPECTIVE ON ARCHEAN CRUST FORMATION AND ON THE PRESENCE OR ABSENCE OF ARCHEAN SUBDUCTION 3 AN OVERVIEW OF THE LITHOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF THE MESOARCHEAN (CA 3075 MA) IVISAARTOQ GREENSTONE BELT, SOUTHERN WEST GREENLAND 4 STRATIGRAPHY, GEOCHEMISTRY, AND DEPOSITIONAL ENVIRONMENTS OF MESOARCHEAN SEDIMENTARY UNITS IN WESTERN SUPERIOR PROVINCE: IMPLICATIONS FOR GENERATION OF EARLY CRUST PHILIP FRALICK, PETE HOLLINGS, AND DAVID KING 5 CHARACTERISTIC THERMAL REGIMES OF PLATE TECTONICS AND THEIR METAMORPHIC IMPRINT THROUGHOUT EARTH HISTORY: WHEN DID EARTH FIRST ADOPT A PLATE TECTONICS MODE OF BEHAVIOR? 6 EVIDENCE FOR MODERN-STYLE SUBDUCTION TO 3 1 GA: A PLATEAU–ADAKITE–GOLD (DIAMOND) ASSOCIATION MANTLE GEODYNAMIC CONSTRAINTS 7 EFFECTS OF A WARMER MANTLE ON THE CHARACTERISTICS OF ARCHEAN PASSIVE MARGINS 8 TECTONICS OF EARLY EARTH: SOME GEODYNAMIC CONSIDERATIONS 9 THE LATE ARCHEAN ABITIBI-OPATICA TERRANE, SUPERIOR PROVINCE: A MODIFIED OCEANIC PLATEAU 10 WHEN DID PLATE TECTONICS BEGIN? EVIDENCE FROM THE OROGENIC RECORD 11 SEISMIC IMAGES OF PALEOPROTEROZOIC MICROPLATE BOUNDARIES IN THE FENNOSCANDIAN SHIELD 12 PLATE TECTONICS ON EARLY EARTH? WEIGHING THE PALEOMAGNETIC EVIDENCE 13 MODERN-STYLE PLATE TECTONICS BEGAN IN NEOPROTEROZOIC TIME: AN ALTERNATIVE INTERPRETATION OF EARTH’S TECTONIC HISTORY 14 WHEN DID PLATE TECTONICS BEGIN? EVIDENCE FROM THE GEOLOGIC RECORD 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 ABSTRACT CONSIDERABLE GEOCHEMICAL EVIDENCE SUPPORTS INITIATION OF PLATE TECTONICS ON EARTH SHORTLY AFTER THE END OF THE HADEAN NB/TH AND TH/U OF MA? C-ULTRAMA? C ROCKS FROM THE DEPLETED UPPER MANTLE BEGAN TO CHANGE FROM 7 TO 18 2 AND 4 2 TO 2 6 (RESPECTIVELY) AT 3 6 GA THIS SIGNALS THE APPEARANCE OF SUBDUCTION-ALTERED SLABS IN GENERAL MANTLE CIRCULATION FROM SUBDUCTION INITIATED BY 3 9 GA JUVENILE CRUSTAL ROCKS BEGAN TO SHOW DERIVATION FROM PROGRESSIVELY DEPLETED MANTLE WITH TYPICAL IGNEOUS ?ND:?HF = 1:2 AFTER 3 6 GA CRATONS WITH STABLE MANTLE KEELS THAT HAVE SUBDUCTION IMPRINTS BEGAN TO APPEAR BY AT LEAST 3 5 GA THESE CHANGES ALL SUGGEST THAT EXTRACTION OF CONTINENTAL CRUST BY PLATE TECTONIC PROCESSES WAS PROGRESSIVELY DEPLETING THE MANTLE FROM 3 6 GA ONWARDS NEO- ARCHEAN SUBDUCTION APPEARS LARGELY ANALOGOUS TO PRESENT SUBDUCTION EXCEPT IN BEING ABLE TO PRODUCE LARGE CRATONS WITH THICK MANTLE KEELS THE EARLIEST EOARCHEAN JUVENILE ROCKS AND HADEAN ZIRCONS HAVE ISOTOPIC COMPOSITIONS THAT RE? ECT THE INTEGRATED EFFECTS OF SEPARATION OF AN EARLY ENRICHED RESERVOIR AND FRACTIONATION OF CA-SILICATE AND MG-SIL- ICATE PEROVSKITE FROM THE TERRESTRIAL MAGMA OCEANS ASSOCIATED WITH EARTH ACCRETION AND MOON FORMATION, SUPERPOSED ON SUBSEQUENT CRUSTAL PROCESSES HADEAN ZIRCONS MOST LIKELY WERE DERIVED FROM A CONTINENT-ABSENT, MA? C TO ULTRAMA? C PROTOCRUST THAT WAS