DOCSLIB.ORG

Heterogeneous Hadean Crust with Ambient Mantle Affinity Recorded in Detrital Zircons of the Green Sandstone Bed, South Africa

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Heterogeneous Hadean Crust with Ambient Mantle Affinity Recorded in Detrital Zircons of the Green Sandstone Bed, South Africa Heterogeneous Hadean crust with ambient mantle affinity recorded in detrital zircons of the Green Sandstone Bed, South Africa Nadja Drabona,1,2, Benjamin L. Byerlyb,3, Gary R. Byerlyc, Joseph L. Woodend,4, C. Brenhin Kellere, and Donald R. Lowea aDepartment of Geological Sciences, Stanford University, Stanford, CA 94305; bDepartment of Earth Sciences, University of California, Santa Barbara, CA 93106; cDepartment of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803; dPrivate address, Marietta, GA 30064; and eDepartment of Earth Sciences, Dartmouth College, Hanover, NH 03755 Edited by Albrecht W. Hofmann, Max Planck Institute for Chemistry, Mainz, Germany, and approved January 4, 2021 (received for review March 10, 2020) The nature of Earth’s earliest crust and the processes by which it While the crustal rocks in which Hadean zircon formed have formed remain major issues in Precambrian geology. Due to the been lost, the trace and rare earth element (REE) geochemistry of absence of a rock record older than ∼4.02 Ga, the only direct re- these zircons can be used to characterize their parental magma cord of the Hadean is from rare detrital zircon and that largely compositions. Zircon crystallizes as a ubiquitous accessory mineral from a single area: the Jack Hills and Mount Narryer region of in silica-rich, differentiated magmas formed in a number of crustal Western Australia. Here, we report on the geochemistry of environments. Since zircon compositions are influenced by varia- Hadean detrital zircons as old as 4.15 Ga from the newly discov- tions in melt composition, coexisting mineral assemblage, and trace ered Green Sandstone Bed in the Barberton greenstone belt, element partitioning as a function of magmatic processes, temper- South Africa. We demonstrate that the U-Nb-Sc-Yb systematics ature, and pressure (14–17), zircon geochemistry provides valuable of the majority of these Hadean zircons show a mantle affinity constraints on magmatic compositions and processes at the time of as seen in zircon from modern plume-type mantle environments zircon saturation. Consequently, trace element compositions of ig- and do not resemble zircon from modern continental or oceanic arcs. The zircon trace element compositions furthermore suggest neous and detrital zircon are a powerful tool that can be used to magma compositions ranging from higher temperature, primitive track melt evolution of individual magma bodies (18, 19) and EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES to lower temperature, and more evolved tonalite-trondhjemite- changes within a tectono-magmatic system (20) or across an entire granodiorite (TTG)-like magmas that experienced some reworking continent (21). Grimes et al. (16) pioneered the use of zircon trace of hydrated crust. We propose that the Hadean parental magmas of element geochemistry to differentiate modern tectono-magmatic the Green Sandstone Bed zircons formed from remelting of mafic, environments based on differences in source compositions (e.g., mantle-derived crust that experienced some hydrous input during depleted versus undepleted mantle) and magmatic process (flux melting but not from the processes seen in modern arc magmatism. melting in arc settings) by using a family of discrimination diagrams. They used a compilation of ∼5,300 zircons from various crustal Hadean | zircon | early Earth | crustal evolution environments across the globe and found that, despite internal heterogeneity due to petrological processes, bivariate diagrams us- nderstanding the nature of Earth’s earliest crust and con- ing U, Nb, Sc, Yb, Gd, and Ce can be used to distinguish between Ustraining the timing of early continent formation are crucial to modeling the evolution of the geodynamic system and the Significance compositions of Earth’s early atmosphere and hydrosphere. Consensus over the nature of the earliest crust remains elusive. The nature of Earth’s earliest crust is enigmatic due to the lack General models range from those suggesting an onset of continent of a rock record for most of Earth’s first ∼600 My, the Hadean formation (1, 2) and possible formation of arcs in a plate tectonic Eon. Studies have thus turned to scarce sites where Hadean regime similar to that of today (3) shortly following Earths for- detrital zircons have been discovered. The geochemistry of mation to studies suggesting that the earliest crust was overall Hadean detrital zircon from a newly discovered site in South more mafic than modern curst in composition and continents ei- Africa suggests that the parental melts formed from variably ther rare or absent (4–7). Detrital zircons provide the only direct hydrous melting of crust derived from the ambient mantle and record of Earth’s first 500 million years of history. The most sig- show little evidence for an origin in arc-like settings. These nificant source of Hadean zircons are Archean sedimentary rocks results suggest that crust derived from ambient mantle played in the Jack Hills and Mount Narryer region in Western Australia. an important role during crust formation in the Hadean. Isolated Hadean zircons have also been found in a dozen other locations worldwide (8, 9). Of these locations, the Green Sand- Author contributions: N.D. and D.R.L. designed research; N.D., B.L.B., and G.R.B. per- stone Bed (GSB) in the Barberton greenstone belt, South Africa, formed research; N.D. and J.L.W. analyzed data; C.B.K. did zircon saturation modeling, stands out with a total of 33 Hadean zircons discovered to date and N.D. wrote the paper. (10) (Datasets S1 and S2 and SI Appendix,Fig.S1). The GSB is The authors declare no competing interest. dated by the S6 spherule layer that lies 2 m below the GSB and has This article is a PNAS Direct Submission. a depositional age of ∼3.31 Ga (11). The detrital zircons in the Published under the PNAS license. GSB show a major age peak at 3.38 Ga and include a significant 1To whom correspondence may be addressed. Email: [email protected]. number of zircons older than the oldest known igneous rocks and 2Present address: Department of Earth and Planetary Sciences, Harvard University, strata in the 3.55 to 3.22 Ga Barberton greenstone belt (10). In Cambridge, MA 02138. total, 0.5% of the analyzed zircons from the GSB are Hadean in age 3Present address: Enterprise Services, Thermo Fisher Scientific, Waltham, MA 02451. (10). Throughout its geological history, the GSB has experienced 4Retired author. only lower greenschist-grade metamorphism (12, 13) and remains This article contains supporting information online at https://www.pnas.org/lookup/suppl/ essentially unsheared. As a result, it contains well-preserved primary doi:10.1073/pnas.2004370118/-/DCSupplemental. mineral grains. Published February 18, 2021. PNAS 2021 Vol. 118 No. 8 e2004370118 https://doi.org/10.1073/pnas.2004370118 | 1of9 Downloaded by guest on September 26, 2021 different tectono-magmatic settings, even if the crust experienced the zircons formed by simple fractionation from a single magma subsequent reworking within the same crustal setting. composition (SI Appendix,Fig.S3). In this study, we use the geochemistry of GSB Hadean zircons Besides these general characteristics, there is an apparent to characterize the compositions and possible sources of their clustering in the data. The U/Yb data show a separation of the parental magmas, highlight similarities and differences to zircon zircon compositions into two groups (here termed as Group I and from Phanerozoic tectono-magmatic settings, and compare the Group II) that, based on a PCA and bivariate plots, also translates results to the geochemistry of Hadean zircons from the Jack Hills to general differences in other trace element ratios (Figs. 2 and 3 to make broader inferences about the nature of Hadean crust and and Dataset S3). It is important to note that due to the low ultimately determine whether they originated from an arc or a number of zircons, it is difficult to evaluate if these groups rep- relatively undepleted mantle environment. resent distinct source magmas or what is actually a continuum of compositions. However, discussing these as separate composi- Geochemistry of Hadean Zircons tional types of zircons makes it easier to compare and contrast the Zircon texture and geochemistry have long been used to differ- different possible processes or sources that could produce the entiate igneous from metamorphic zircon (22). Hadean zircons observed variations. Zircons of Group I (5 zircons with 11 analy- from the GSB show oscillatory and sector zoning typical of igne- ses) shows less spread in its compositional averages with lower ± ± ous zircon (10) (Fig. 1 and SI Appendix,Fig.S2). A total of five U/Yb (0.15 0.015), higher Th/U (0.91 0.16), higher Gd/Yb ± ± ± zircons show igneous cores with recrystallization rims indicative of (0.09 0.01), lower Nb/Yb (0.01 0.01), lower Nb/Sc (0.29 ± ± metamorphic overgrowth. These rims were not analyzed for this 0.06), higher Ti (8.6 3.3 ppm), and elevated Sc/Yb (0.08 0.04). study. None of the Hadean zircons found to date display a spongy In contrast, Group II (10 zircons with 16 analyses) shows a wider ± ± texture indicative of fluid-dominated recrystallization. In Phaner- spread with elevated U/Yb (0.61 0.61), lower Th/U (0.54 ± ± ozoic zircon, a Th/U ratio <0.1 serves as an indicator for meta- 0.21), lower Gd/Yb (0.05 0.02), lower Ti (5.1 3.8 ppm), higher Nb/Yb (0.04 ± 0.04), higher Nb/Sc (1.0 ± 0.02), and lower Sc/Yb morphic zircon (22). In the GSB zircons, Th/U ratios vary from ± 0.18 to 1.15, supporting a primary igneous origin. Similarly, GSB (0.05 0.02). There is some variability in the geochemical com- position between different spots on the same grain.
Load more

Recommended publications
  • Timeline of Natural History
    Timeline of natural history This timeline of natural history summarizes significant geological and Life timeline Ice Ages biological events from the formation of the 0 — Primates Quater nary Flowers ←Earliest apes Earth to the arrival of modern humans. P Birds h Mammals – Plants Dinosaurs Times are listed in millions of years, or Karo o a n ← Andean Tetrapoda megaanni (Ma). -50 0 — e Arthropods Molluscs r ←Cambrian explosion o ← Cryoge nian Ediacara biota – z ←Earliest animals o ←Earliest plants i Multicellular -1000 — c Contents life ←Sexual reproduction Dating of the Geologic record – P r The earliest Solar System -1500 — o t Precambrian Supereon – e r Eukaryotes Hadean Eon o -2000 — z o Archean Eon i Huron ian – c Eoarchean Era ←Oxygen crisis Paleoarchean Era -2500 — ←Atmospheric oxygen Mesoarchean Era – Photosynthesis Neoarchean Era Pong ola Proterozoic Eon -3000 — A r Paleoproterozoic Era c – h Siderian Period e a Rhyacian Period -3500 — n ←Earliest oxygen Orosirian Period Single-celled – life Statherian Period -4000 — ←Earliest life Mesoproterozoic Era H Calymmian Period a water – d e Ectasian Period a ←Earliest water Stenian Period -4500 — n ←Earth (−4540) (million years ago) Clickable Neoproterozoic Era ( Tonian Period Cryogenian Period Ediacaran Period Phanerozoic Eon Paleozoic Era Cambrian Period Ordovician Period Silurian Period Devonian Period Carboniferous Period Permian Period Mesozoic Era Triassic Period Jurassic Period Cretaceous Period Cenozoic Era Paleogene Period Neogene Period Quaternary Period Etymology of period names References See also External links Dating of the Geologic record The Geologic record is the strata (layers) of rock in the planet's crust and the science of geology is much concerned with the age and origin of all rocks to determine the history and formation of Earth and to understand the forces that have acted upon it.
    [Show full text]
  • The Geologic Time Scale Is the Eon
    Exploring Geologic Time Poster Illustrated Teacher's Guide #35-1145 Paper #35-1146 Laminated Background Geologic Time Scale Basics The history of the Earth covers a vast expanse of time, so scientists divide it into smaller sections that are associ- ated with particular events that have occurred in the past.The approximate time range of each time span is shown on the poster.The largest time span of the geologic time scale is the eon. It is an indefinitely long period of time that contains at least two eras. Geologic time is divided into two eons.The more ancient eon is called the Precambrian, and the more recent is the Phanerozoic. Each eon is subdivided into smaller spans called eras.The Precambrian eon is divided from most ancient into the Hadean era, Archean era, and Proterozoic era. See Figure 1. Precambrian Eon Proterozoic Era 2500 - 550 million years ago Archaean Era 3800 - 2500 million years ago Hadean Era 4600 - 3800 million years ago Figure 1. Eras of the Precambrian Eon Single-celled and simple multicelled organisms first developed during the Precambrian eon. There are many fos- sils from this time because the sea-dwelling creatures were trapped in sediments and preserved. The Phanerozoic eon is subdivided into three eras – the Paleozoic era, Mesozoic era, and Cenozoic era. An era is often divided into several smaller time spans called periods. For example, the Paleozoic era is divided into the Cambrian, Ordovician, Silurian, Devonian, Carboniferous,and Permian periods. Paleozoic Era Permian Period 300 - 250 million years ago Carboniferous Period 350 - 300 million years ago Devonian Period 400 - 350 million years ago Silurian Period 450 - 400 million years ago Ordovician Period 500 - 450 million years ago Cambrian Period 550 - 500 million years ago Figure 2.
    [Show full text]
  • Soils in the Geologic Record
    in the Geologic Record 2021 Soils Planner Natural Resources Conservation Service Words From the Deputy Chief Soils are essential for life on Earth. They are the source of nutrients for plants, the medium that stores and releases water to plants, and the material in which plants anchor to the Earth’s surface. Soils filter pollutants and thereby purify water, store atmospheric carbon and thereby reduce greenhouse gasses, and support structures and thereby provide the foundation on which civilization erects buildings and constructs roads. Given the vast On February 2, 2020, the USDA, Natural importance of soil, it’s no wonder that the U.S. Government has Resources Conservation Service (NRCS) an agency, NRCS, devoted to preserving this essential resource. welcomed Dr. Luis “Louie” Tupas as the NRCS Deputy Chief for Soil Science and Resource Less widely recognized than the value of soil in maintaining Assessment. Dr. Tupas brings knowledge and experience of global change and climate impacts life is the importance of the knowledge gained from soils in the on agriculture, forestry, and other landscapes to the geologic record. Fossil soils, or “paleosols,” help us understand NRCS. He has been with USDA since 2004. the history of the Earth. This planner focuses on these soils in the geologic record. It provides examples of how paleosols can retain Dr. Tupas, a career member of the Senior Executive Service since 2014, served as the Deputy Director information about climates and ecosystems of the prehistoric for Bioenergy, Climate, and Environment, the Acting past. By understanding this deep history, we can obtain a better Deputy Director for Food Science and Nutrition, and understanding of modern climate, current biodiversity, and the Director for International Programs at USDA, ongoing soil formation and destruction.
    [Show full text]
  • Using Volcaniclastic Rocks to Constrain Sedimentation Ages
    Using volcaniclastic rocks to constrain sedimentation ages: To what extent are volcanism and sedimentation synchronous? Camille Rossignol, Erwan Hallot, Sylvie Bourquin, Marc Poujol, Marc Jolivet, Pierre Pellenard, Céline Ducassou, Thierry Nalpas, Gloria Heilbronn, Jianxin Yu, et al. To cite this version: Camille Rossignol, Erwan Hallot, Sylvie Bourquin, Marc Poujol, Marc Jolivet, et al.. Using vol- caniclastic rocks to constrain sedimentation ages: To what extent are volcanism and sedimentation synchronous?. Sedimentary Geology, Elsevier, 2019, 381, pp.46-64. 10.1016/j.sedgeo.2018.12.010. insu-01968102 HAL Id: insu-01968102 https://hal-insu.archives-ouvertes.fr/insu-01968102 Submitted on 2 Jan 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Accepted Manuscript Using volcaniclastic rocks to constrain sedimentation ages: To what extent are volcanism and sedimentation synchronous? Camille Rossignol, Erwan Hallot, Sylvie Bourquin, Marc Poujol, Marc Jolivet, Pierre Pellenard, Céline Ducassou, Thierry Nalpas, Gloria Heilbronn, Jianxin Yu, Marie-Pierre
    [Show full text]
  • Eoarchean Crustal Evolution of the Jack Hills Zircon Source and Loss of Hadean Crust
    Available online at www.sciencedirect.com ScienceDirect Geochimica et Cosmochimica Acta 146 (2014) 27–42 www.elsevier.com/locate/gca Eoarchean crustal evolution of the Jack Hills zircon source and loss of Hadean crust Elizabeth A. Bell ⇑, T. Mark Harrison, Issaku E. Kohl, Edward D. Young Dept. of Earth, Planetary, and Space Sciences, UCLA, United States Received 10 March 2014; accepted in revised form 18 September 2014; available online 30 September 2014 Abstract Given the global dearth of Hadean (>4 Ga) rocks, 4.4–4.0 Ga detrital zircons from Jack Hills, Narryer Gneiss Complex (Yilgarn Craton, Western Australia) constitute our best archive of early terrestrial materials. Previous Lu–Hf investigations of these zircons suggested that felsic (low Lu/Hf) crust formation began by 4.4 to 4.5 Ga and continued for several hundred million years with evidence of the least radiogenic Hf component persisting until at least 4 Ga. However, evidence for the involvement of Hadean materials in later crustal evolution is sparse, and even in the detrital Jack Hills zircon population, the most unradiogenic, ancient isotopic signals have not been definitively identified in the younger (<3.9 Ga) rock and zircon record. Here we show Lu–Hf data from <4 Ga Jack Hills detrital zircons that document a significant and previously unknown transition in Yilgarn Craton crustal evolution between 3.9 and 3.7 Ga. The zircon source region evolved largely by internal reworking through the period 4.0–3.8 Ga, and the most ancient and unradiogenic components of the crust are mostly missing from the record after 4 Ga.
    [Show full text]
  • Convective Isolation of Hadean Mantle Reservoirs Through Archean Time
    Convective isolation of Hadean mantle reservoirs through Archean time Jonas Tuscha,1, Carsten Münkera, Eric Hasenstaba, Mike Jansena, Chris S. Mariena, Florian Kurzweila, Martin J. Van Kranendonkb,c, Hugh Smithiesd, Wolfgang Maiere, and Dieter Garbe-Schönbergf aInstitut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany; bSchool of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW 2052, Australia; cAustralian Center for Astrobiology, The University of New South Wales, Kensington, NSW 2052, Australia; dDepartment of Mines, Industry Regulations and Safety, Geological Survey of Western Australia, East Perth, WA 6004, Australia; eSchool of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, United Kingdom; and fInstitut für Geowissenschaften, Universität zu Kiel, 24118 Kiel, Germany Edited by Richard W. Carlson, Carnegie Institution for Science, Washington, DC, and approved November 18, 2020 (received for review June 19, 2020) Although Earth has a convecting mantle, ancient mantle reservoirs anomalies in Eoarchean rocks was interpreted as evidence that that formed within the first 100 Ma of Earth’s history (Hadean these rocks lacked a late veneer component (5). Conversely, the Eon) appear to have been preserved through geologic time. Evi- presence of some late accreted material is required to explain the dence for this is based on small anomalies of isotopes such as elevated abundances of highly siderophile elements (HSEs) in 182W, 142Nd, and 129Xe that are decay products of short-lived nu- Earth’s modern silicate mantle (9). Notably, some Archean rocks clide systems. Studies of such short-lived isotopes have typically with apparent pre-late veneer like 182W isotope excesses were focused on geological units with a limited age range and therefore shown to display HSE concentrations that are indistinguishable only provide snapshots of regional mantle heterogeneities.
    [Show full text]
  • Geologic Time Lesson Guide Lesson Guide | Description
    Geologic Time Lesson Guide Lesson Guide | Description Instructor: Dr. Michael T. Lewchuk Grade Level: 6 - 12 Subject: Earth & Physical Science Students will investigate the subdivisions of the Geologic Time Scale. Wonder How: Have you ever wondered how scientists and geologists know how old something is? Goal: Students will gather data and use ratios that will help them create a scale model of Geological time using simple materials found at home. Lesson Guide | Lesson Guide Agenda Lesson Guide Agenda: v Vocabulary v Materials List v Geologic Time Scale v Activity Instructions v Challenge! v Additional Resources v Oklahoma Academic Standards Lesson Guide | Vocabulary Eon – An Eon is the fundamental division of time in Geology. The Earth’s 4.6-billion- year history is divided into four Eons: Hadean, Archean, Proterozoic and Phanerozoic. Precambrian Supereon – This is the combination of the Hadean, Archean and Proterozoic Eons. It is subdivided based on the physical properties of the Earth’s surface and atmosphere. Hadean Eon – The Hadean is the oldest Eon. It is generally described as the time when the Earth was so hot that it was all, or mostly all, molten liquid. Archean Eon – The Archean Eon is generally described as the time when solid rock existed on the surface of the Earth, but little or no free oxygen existed in the atmosphere. Proterozoic Eon – The Proterozoic is generally considered the Eon when free oxygen began to appear in the atmosphere. Microscopic life developed during the Proterozoic. Lesson Guide | Vocabulary Phanerozoic Eon – The Phanerozoic Eon is the most recent Eon in geologic history.
    [Show full text]
  • The World Turns Over: Hadean–Archean Crust–Mantle Evolution
    Lithos 189 (2014) 2–15 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Review paper The world turns over: Hadean–Archean crust–mantle evolution W.L. Griffin a,⁎, E.A. Belousova a,C.O'Neilla, Suzanne Y. O'Reilly a,V.Malkovetsa,b,N.J.Pearsona, S. Spetsius a,c,S.A.Wilded a ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS) and GEMOC, Dept. Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia b VS Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia c Scientific Investigation Geology Enterprise, ALROSA Co Ltd, Mirny, Russia d ARC Centre of Excellence for Core to Crust Fluid Systems, Dept of Applied Geology, Curtin University, G.P.O. Box U1987, Perth 6845, WA, Australia article info abstract Article history: We integrate an updated worldwide compilation of U/Pb, Hf-isotope and trace-element data on zircon, and Re–Os Received 13 April 2013 model ages on sulfides and alloys in mantle-derived rocks and xenocrysts, to examine patterns of crustal evolution Accepted 19 August 2013 and crust–mantle interaction from 4.5 Ga to 2.4 Ga ago. The data suggest that during the period from 4.5 Ga to ca Available online 3 September 2013 3.4 Ga, Earth's crust was essentially stagnant and dominantly maficincomposition.Zirconcrystallizedmainly from intermediate melts, probably generated both by magmatic differentiation and by impact melting. This quies- Keywords: – Archean cent state was broken by pulses of juvenile magmatic activity at ca 4.2 Ga, 3.8 Ga and 3.3 3.4 Ga, which may Hadean represent mantle overturns or plume episodes.
    [Show full text]
  • Temporal Variation in Relative Zircon Abundance Throughout Earth History
    Letter Geochemical Perspectives Letters magma crystallisation, crust production, and even crustal composition (Condie et al., 2009; Cawood et al., 2013; Parman, 2015; Lee et al., 2016). However, quantity of zircon is not a direct substitute for quantity of magma or crust. Instead, zircon © 2017 European Association of Geochemistry abundance in the igneous record is a function of magma composition, which is both spatially and temporally heterogeneous. Moreover, due to the high closure temperatures of the U-Th/Pb and U-series systems, ages from these geochro- Temporal variation in relative zircon nometers exclusively date zircon crystallisation (Schoene, 2014), which need not abundance throughout Earth history coincide with the crystallisation of other silicate minerals. The temperature Tsat at which zircon saturates in an igneous magma can C.B. Keller1,2,3*, P. Boehnke4,5, B. Schoene3 be accurately predicted by an empirical equation of the form Zr a zircon = ln + bM + c T Zr sat melt Abstract doi: 10.7185/geochemlet.1721 where a, b, and c are constants, [Zr] is zirconium concentration, and M is a Zircon is the preeminent chronometer of deep time on Earth, informing models of crustal compositional measure of magma polymerisation defined on a molar basis as growth and providing our only direct window into the Hadean Eon. However, the quantity of zircon crystallised per unit mass of magma is highly variable, complicating interpreta- Na + K + 2 Ca tion of the terrestrial zircon record. Here we combine zircon saturation simulations with a M = dataset of ~52,000 igneous whole rock geochemical analyses to quantify secular variation in Al ∗ Si relative zircon abundance throughout Earth history.
    [Show full text]
  • The Geochronology and Geochemistry of Zircon As Evidence for the Reconcentration of REE in the Triassic Period in the Chungju Area, South Korea
    minerals Article The Geochronology and Geochemistry of Zircon as Evidence for the Reconcentration of REE in the Triassic Period in the Chungju Area, South Korea Sang-Gun No 1,* and Maeng-Eon Park 2 1 Mineral Resources Development Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea 2 Department of Earth Environmental Science, Pukyong National University, Busan 48513, Korea; [email protected] * Correspondence: [email protected]; Tel.: +82-10-9348-7807 Received: 1 November 2019; Accepted: 2 January 2020; Published: 5 January 2020 Abstract: The Chungju rare-earth element (REE) deposit is located in the central part of the Okcheon Metamorphic Belt (OMB) in the Southern Korean Peninsula and research on REE mineralization in the Gyemyeongsan Formation has been continuous since the first report in 1989. The genesis of the REE mineralization that occurred in the Gyemyeongsan Formation has been reported by previous researchers; theories include the fractional crystallization of alkali magma, magmatic hydrothermal alteration, and recurrent mineralization during metamorphism. In the Gyemyeongsan Formation, we discovered an allanite-rich vein that displays the paragenetic relationship of quartz, allanite, and zircon, and we investigated the chemistry and chronology of zircon obtained from this vein. We analyzed the zircon’s chemistry with an electron probe X-ray micro analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The grain size of the zircon is as large as 50 µm and has an inherited core (up to 15 µm) and micrometer-sized sector zoning (up to several micrometers in size). In a previous study, the zircon ages were not obtained because the grain size was too small to analyze.
    [Show full text]
  • Paleoarchean Bedrock Lithologies Across the Makhonjwa Mountains Of
    Geoscience Frontiers 9 (2018) 603e665 HOSTED BY Contents lists available at ScienceDirect China University of Geosciences (Beijing) Geoscience Frontiers journal homepage: www.elsevier.com/locate/gsf Research Paper Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data reveal early plate tectonic genes flanking subduction margins Maarten de Wit a,*, Harald Furnes b, Scott MacLennan a,c, Moctar Doucouré a,d, Blair Schoene c, Ute Weckmann e, Uma Martinez a,f, Sam Bowring g a AEON-ESSRI (Africa Earth Observatory Network-Earth Stewardship Science Research Institute), Nelson Mandela University, Port Elizabeth, South Africa b Department of Earth Science & Centre for Geobiology, University of Bergen, Norway c Department of Geosciences, Princeton University, Guyot Hall, Princeton, NJ, USA d Department of Geosciences, Nelson Mandela University, Port Elizabeth, South Africa e Department Geophysics, GFZ - German Research Centre for Geosciences, Helmholtz Centre, Telegrafenberg, 14473 Potsdam, Germany f GISCAPETOWN, Cape Town, South Africa g Earth, Atmosphere and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA article info abstract Article history: The Makhonjwa Mountains, traditionally referred to as the Barberton Greenstone Belt, retain an iconic Received 12 June 2017 Paleoarchean archive against which numerical models of early earth geodynamics can be tested. We Received in revised form present new geologic and structural maps, geochemical plots, geo- and thermo-chronology, and 2 October 2017 geophysical data from seven silicic, mafic to ultramafic complexes separated by major shear systems across Accepted 5 October 2017 the southern Makhonjwa Mountains. All reveal signs of modern oceanic back-arc crust and subduction- Available online 31 October 2017 related processes.
    [Show full text]
  • The Archean Geology of Montana
    THE ARCHEAN GEOLOGY OF MONTANA David W. Mogk,1 Paul A. Mueller,2 and Darrell J. Henry3 1Department of Earth Sciences, Montana State University, Bozeman, Montana 2Department of Geological Sciences, University of Florida, Gainesville, Florida 3Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana ABSTRACT in a subduction tectonic setting. Jackson (2005) char- acterized cratons as areas of thick, stable continental The Archean rocks in the northern Wyoming crust that have experienced little deformation over Province of Montana provide fundamental evidence long (Ga) periods of time. In the Wyoming Province, related to the evolution of the early Earth. This exten- the process of cratonization included the establishment sive record provides insight into some of the major, of a thick tectosphere (subcontinental mantle litho- unanswered questions of Earth history and Earth-sys- sphere). The thick, stable crust–lithosphere system tem processes: Crustal genesis—when and how did permitted deposition of mature, passive-margin-type the continental crust separate from the mantle? Crustal sediments immediately prior to and during a period of evolution—to what extent are Earth materials cycled tectonic quiescence from 3.1 to 2.9 Ga. These compo- from mantle to crust and back again? Continental sitionally mature sediments, together with subordinate growth—how do continents grow, vertically through mafi c rocks that could have been basaltic fl ows, char- magmatic accretion of plutons and volcanic rocks, acterize this period. A second major magmatic event laterally through tectonic accretion of crustal blocks generated the Beartooth–Bighorn magmatic zone assembled at continental margins, or both? Structural at ~2.9–2.8 Ga.
    [Show full text]