The Electrical Structure of the Slave Craton
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Preliminary Geologic Map of the Baird Mountains and Part of the Selawik Quadrangles, Alaska By
preliminary Geologic Map of the Baird Mountains and part of the Selawik Quadrangles, Alaska by S.M. Karl, J.A. Dumoulin, Inyo Ellersieck, A.G. Harris, and J.M. Schmidt Open-File Report 89-551 This map is preliminary and has not been reviewed for conformity with the North American stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Table Contents ~ntroduction.......................................... 1 Stratigraphic Framework .................................1 Structural Framework ....................................4 Acknowledgments .......................................6 Unit Descriptions ......................................6 Kc ............................................. 6 KJm .............................................6 JPe .............................................7 ~zb................ '. ... ., ,....................... 8 Mzg ............................................10 MzPzi ..........................................10 MZPZ~.......................................... 11 PMC ............................................12 PD1 ............................................12 Mk0 ............................................12 M1 .............................................13 MDue ...........................................14 Mlt ............................................15 Mk .............................................15 MD1 ............................................16 MDe ............................................16 MD~........................................... -
GY 112 Lecture Notes D
GY 112 Lecture Notes D. Haywick (2006) 1 GY 112 Lecture Notes Archean Geology Lecture Goals: A) Time frame (the Archean and earlier) B) Rocks and tectonic elements (shield/platform/craton) C) Tectonics and paleogeography Textbook reference: Levin 7th edition (2003), Chapter 6; Levin 8th edition (2006), Chapter 8 A) Time frame Up until comparatively recently (start of the 20th century), most geologists focused their discussion of geological time on two eons; the “Precambrian” and the Phanerozoic. We now officially recognize 4 eons and the Precambrian is just used as a come-all term for all time before the Phanerozoic: Eon Time Phanerozoic 550 MA to 0 MA Proterozoic 2.5 GA to 550 MA Archean 3.96 GA to 2.5 GA Hadean 4.6 GA to 3.96 GA The “youngest” of these two new eons, the Archean, was first introduced by field geologists working in areas where very old rocks cropped out. One of these geologists was Sir William Logan (pictured at left; ess.nrcan.gc.ca ) one of the most respected geologists working with the Geological Survey of Canada. His study area was the Canadian Shield. Logan was able to identify two major types of rocks; 1) layered sedimentary and volcanic rocks and 2) highly metamorphosed granitic gneisses (see image at the top of the next page from http://www.trailcanada.com/images/canadian-shield.jpg). Logan found evidence that the gneisses mostly underlayed the layered rocks and hence, they had to be older than the layered rocks. The layered rocks were known to be Proterozoic in age. -
The Late Tectonic Evolution of the Slave Craton and Formation of Its Tectosphere
The Late Tectonic Evolution of the Slave Craton and Formation of its Tectosphere W.J. Davis, W. Bleeker, K. MacLachlan, Jones, A.G. and Snyder, D. An outstanding question in Archean tectonics is the relationship between thick, depleted lithospheric keels that presently underlie the cratons and the overlying crustal section. Evidence for Archean diamonds and Re-Os model ages of cratonic peridotites argue for the development of stable lithospheric mantle early in a cratons history, at least in part synchronous with crust formation or stabilisation (Pearson 1999). The late tectonic evolution of cratons is complex and involves extensive magmatism, deformation, and metamorphism that significantly post-date the timing of crust formation. Many of these tectonic events are difficult to reconcile with early development of thick tectosphere and suggest that crust-mantle coupling and stabilization occurred late in the orogenic development of cratons. Over the past decade the Slave craton in northwestern Laurentia, has emerged as a major diamondiferous craton. The extensive and well documented geological record of the Slave craton, provides a new crustal perspective on the development of diamond-bearing tectosphere. In this contribution we describe the late tectonic evolution of the Slave craton based on field and geochronological studies, supplemented by geochronological data from lower crustal xenoliths to argue that stabilisation of the cratonic root, certainly to depths of 200 km, was most likely a late feature of the craton. Geological Background The Slave is a small craton bounded by Paleoproterozic orogenic belts on its east and west. The craton is characterized throughout its central and western part by a Mesoarchean basement (4.0 -2.9Ga) referred to as the Central Slave Basement Complex (CSBC; Bleeker et al 1999), and its cover sequence, with isotopically juvenile (<2.85 Ga?) but undefined basement in the east (Thorpe et al 1992; Davis& Hegner, 1992; Davis et al. -
Northwestern Superior Craton Margin, Manitoba: an Overview of Archean
GS-7 Northwestern Superior craton margin, Manitoba: an overview of Archean and Proterozoic episodes of crustal growth, erosion and orogenesis (parts of NTS 54D and 64A) by R.P. Hartlaub1, C.O. Böhm, L.M. Heaman2, and A. Simonetti2 Hartlaub, R.P., Böhm, C.O., Heaman, L.M. and Simonetti, A. 2005: Northwestern Superior craton margin, Manitoba: an overview of Archean and Proterozoic episodes of crustal growth, erosion, and orogenesis (parts of NTS 54D and 64A); in Report of Activities 2005, Manitoba Industry, Economic Development and Mines, Manitoba Geological Survey, p. 54–60. Summary xenocrystic zircon, and in the The northwestern margin of the Superior Province in isotopic signature of Neoarchean Manitoba represents a dynamic boundary zone with good granite bodies (Böhm et al., 2000; potential for magmatic, sedimentary-hosted, and structur- Hartlaub et al., in press). The ALCC extends along the ally controlled mineral deposits. The region has a history Superior margin for at least 50 km, and may have a com- that commences in the early Archean with the formation mon history with other early Archean crustal fragments of the Assean Lake Crustal Complex. This fragment of in northern Quebec and Greenland (Hartlaub et al., in early to middle Archean crust was likely accreted to the press). Superior Province between 2.7 and 2.6 Ga, a major period South of the ALCC, the Split Lake Block repre- of Superior Province amalgamation. Sediments derived sents a variably retrogressed and shear zone–bounded from this amalgamation process were deposited at granulite terrain that is dominated by plutonic rocks and numerous locations along the northwestern margin of mafic granulite (Hartlaub et al., 2003, 2004). -
Part 629 – Glossary of Landform and Geologic Terms
Title 430 – National Soil Survey Handbook Part 629 – Glossary of Landform and Geologic Terms Subpart A – General Information 629.0 Definition and Purpose This glossary provides the NCSS soil survey program, soil scientists, and natural resource specialists with landform, geologic, and related terms and their definitions to— (1) Improve soil landscape description with a standard, single source landform and geologic glossary. (2) Enhance geomorphic content and clarity of soil map unit descriptions by use of accurate, defined terms. (3) Establish consistent geomorphic term usage in soil science and the National Cooperative Soil Survey (NCSS). (4) Provide standard geomorphic definitions for databases and soil survey technical publications. (5) Train soil scientists and related professionals in soils as landscape and geomorphic entities. 629.1 Responsibilities This glossary serves as the official NCSS reference for landform, geologic, and related terms. The staff of the National Soil Survey Center, located in Lincoln, NE, is responsible for maintaining and updating this glossary. Soil Science Division staff and NCSS participants are encouraged to propose additions and changes to the glossary for use in pedon descriptions, soil map unit descriptions, and soil survey publications. The Glossary of Geology (GG, 2005) serves as a major source for many glossary terms. The American Geologic Institute (AGI) granted the USDA Natural Resources Conservation Service (formerly the Soil Conservation Service) permission (in letters dated September 11, 1985, and September 22, 1993) to use existing definitions. Sources of, and modifications to, original definitions are explained immediately below. 629.2 Definitions A. Reference Codes Sources from which definitions were taken, whole or in part, are identified by a code (e.g., GG) following each definition. -
Pan-African Orogeny 1
Encyclopedia 0f Geology (2004), vol. 1, Elsevier, Amsterdam AFRICA/Pan-African Orogeny 1 Contents Pan-African Orogeny North African Phanerozoic Rift Valley Within the Pan-African domains, two broad types of Pan-African Orogeny orogenic or mobile belts can be distinguished. One type consists predominantly of Neoproterozoic supracrustal and magmatic assemblages, many of juvenile (mantle- A Kröner, Universität Mainz, Mainz, Germany R J Stern, University of Texas-Dallas, Richardson derived) origin, with structural and metamorphic his- TX, USA tories that are similar to those in Phanerozoic collision and accretion belts. These belts expose upper to middle O 2005, Elsevier Ltd. All Rights Reserved. crustal levels and contain diagnostic features such as ophiolites, subduction- or collision-related granitoids, lntroduction island-arc or passive continental margin assemblages as well as exotic terranes that permit reconstruction of The term 'Pan-African' was coined by WQ Kennedy in their evolution in Phanerozoic-style plate tectonic scen- 1964 on the basis of an assessment of available Rb-Sr arios. Such belts include the Arabian-Nubian shield of and K-Ar ages in Africa. The Pan-African was inter- Arabia and north-east Africa (Figure 2), the Damara- preted as a tectono-thermal event, some 500 Ma ago, Kaoko-Gariep Belt and Lufilian Arc of south-central during which a number of mobile belts formed, sur- and south-western Africa, the West Congo Belt of rounding older cratons. The concept was then extended Angola and Congo Republic, the Trans-Sahara Belt of to the Gondwana continents (Figure 1) although West Africa, and the Rokelide and Mauretanian belts regional names were proposed such as Brasiliano along the western Part of the West African Craton for South America, Adelaidean for Australia, and (Figure 1). -
Formerly Swaziland)
GeoJournal of Tourism and Geosites Year XI, vol. 22, no. 2, 2018, p.535-547 ISSN 2065-0817, E-ISSN 2065-1198 DOI 10.30892/gtg.22222-309 GEOSITES AS A POTENTIAL FOR THE DEVELOPMENT OF TOURISM – OVERVIEW OF RELEVANT SITES IN ESWATINI (FORMERLY SWAZILAND) Thomas SCHLÜTER* Department of Geography, Environmental Science and Planning, University of Swaziland, P.B. 4, Kwaluseni, Eswatini, e-mail: [email protected] Andreas SCHUMANN Department of Geology and Petroleum Studies, Makerere University, Kampala, Uganda, e-mail: [email protected] Citation: Schlüter, T., & Schumann, A. (2018). GEOSITES AS A POTENTIAL FOR THE DEVELOPMENT OF TOURISM – OVERVIEW OF RELEVANT SITES IN ESWATINI (FORMERLY SWAZILAND). GeoJournal of Tourism and Geosites. 22(2), 535–547. https://doi.org/10.30892/gtg.22222-309 Abstract: Despite being one of the smallest countries in Africa, the Kingdom of Eswatini (formerly Swaziland) is characterized by many locations, which are due to their geoscientific significance to be termed as geosites, and which are here in an overview presented and briefly explained. Each of them can be assigned to a specific scientific approach, e.g. as a landscape, a geological, a geomorphologic, an archaeological (prehistoric) or a mining heritage site. Eswatini yields remarkable landscapes like the Mahamba Gorge and the Sibebe Monolith, it exhibits worldwide one of the largest in granite formed caves (Gobholo), and possibly the oldest dated rocks in Africa (Piggs Peak gneisses), as well as beautiful and scientifically relevant rock painting sites (Nsangwini, Sandlane and Hholoshini) and three abandoned mines in the Barberton Greenstone Belt (Forbes, Ngwenya and Bulembu). -
Timothy O. Nesheim
Timothy O. Nesheim Introduction Superior Craton Kimberlites Beneath eastern North Dakota lays the Superior Craton and the To date, over a hundred kimberlites have been discovered across potential for continued diamond exploration as well as diamond the Superior Craton, more than half of which were discovered mine development. The Superior Craton is a large piece of Earth’s within the past 15 years. Most of these kimberlites occur as crust that has been tectonically stable for over 2.5 billion years. clusters within the Canadian provinces of Ontario and Quebec The long duration of tectonic stability has allowed the underlying (figs. 1 and 2). Moorhead et al. (2000) noted that the average mantle to cool enough to develop the necessary temperature and distance between kimberlite fields/clusters across the Canadian pressure conditions to form diamonds at depths of more than 50 Shield is similar to the typical global average distance of 250 miles miles below the surface. Diamonds are transported to the surface (400 km) between large kimberlite fields. Globally, only 14% through kimberlitic eruptions, which are volcanic eruptions that of kimberlites are diamondiferous (contain diamonds), most in originate tens of miles below the surface and typically erupt concentrations too low for commercial mining. The percentage along zones of weakness in Earth’s crust such as faults and of diamondiferous Superior kimberlites appears to be higher than fractures. The resulting eruption commonly forms a pipe-shaped the global average, including 1) the Attawapiskat cluster – 16 of 18 geologic feature called a kimberlite. Kimberlites typically occur kimberlites (89%) are diamondiferous and so far one kimberlite in groups referred to as either fields or clusters. -
Geologic Time – Part I - Practice Questions and Answers Revised October 2007
Geologic Time – Part I - Practice Questions and Answers Revised October 2007 1. The study of the spatial and temporal relationships between bodies of rock is called ____________________. 2. The geological time scale is the ____________ framework in which geologists view Earth history. 3. Both _________________ and absolute scales are included in the geological time scale. 4. Beds represent a depositional event. They are _________ 1 cm in thickness. 5. Laminations are similar to beds but are ___________ 1 cm in thickness. 6. The idea that most beds are laid down horizontally or nearly so is called the (a) Principle of Original Continuity (b) Principle of Fossil Succession (c) Principle of Cross-Cutting Relationships (d) Principle of Original Horizontality (e) Principle of Superposition 7. The idea that beds extend laterally in three dimensions until they thin to zero thickness is called the (a) Principle of Cross-Cutting Relationships (b) Principle of Original Horizontality (c) Principle of Original Continuity (d) Principle of Fossil Succession (e) Principle of Superposition 8. The idea that younger beds are deposited on top of older beds is called the (a) Principle of Original Horizontality (b) Principle of Fossil Succession (c) Principle of Cross-Cutting Relationships (d) Principle of Original Continuity (e) Principle of Superposition 9. The idea that a dike transecting bedding must be younger than the bedding it crosses is called the (a) Principle of Original Horizontality (b) Principle of Original Continuity (c) Principle of Fossil Succession (d) Principle of Cross-Cutting Relationships (e) Principle of Superposition 10. The idea that fossil content will change upward within a formation is called the (a) Principle of Cross-Cutting Relationships (b) Principle of Original Horizontality (c) Principle of Fossil Succession (d) Principle of Original Continuity (e) Principle of Superposition 11. -
Geology of the Eoarchean, >3.95 Ga, Nulliak Supracrustal
ÔØ ÅÒÙ×Ö ÔØ Geology of the Eoarchean, > 3.95 Ga, Nulliak supracrustal rocks in the Saglek Block, northern Labrador, Canada: The oldest geological evidence for plate tectonics Tsuyoshi Komiya, Shinji Yamamoto, Shogo Aoki, Yusuke Sawaki, Akira Ishikawa, Takayuki Tashiro, Keiko Koshida, Masanori Shimojo, Kazumasa Aoki, Kenneth D. Collerson PII: S0040-1951(15)00269-3 DOI: doi: 10.1016/j.tecto.2015.05.003 Reference: TECTO 126618 To appear in: Tectonophysics Received date: 30 December 2014 Revised date: 30 April 2015 Accepted date: 17 May 2015 Please cite this article as: Komiya, Tsuyoshi, Yamamoto, Shinji, Aoki, Shogo, Sawaki, Yusuke, Ishikawa, Akira, Tashiro, Takayuki, Koshida, Keiko, Shimojo, Masanori, Aoki, Kazumasa, Collerson, Kenneth D., Geology of the Eoarchean, > 3.95 Ga, Nulliak supracrustal rocks in the Saglek Block, northern Labrador, Canada: The oldest geological evidence for plate tectonics, Tectonophysics (2015), doi: 10.1016/j.tecto.2015.05.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT Geology of the Eoarchean, >3.95 Ga, Nulliak supracrustal rocks in the Saglek Block, northern Labrador, Canada: The oldest geological evidence for plate tectonics Tsuyoshi Komiya1*, Shinji Yamamoto1, Shogo Aoki1, Yusuke Sawaki2, Akira Ishikawa1, Takayuki Tashiro1, Keiko Koshida1, Masanori Shimojo1, Kazumasa Aoki1 and Kenneth D. -
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. -
Komatiites, Kimberlites and Boninites. Nicholas Arndt
Komatiites, kimberlites and boninites. Nicholas Arndt To cite this version: Nicholas Arndt. Komatiites, kimberlites and boninites.. Journal of Geophysical Research, American Geophysical Union, 2003, 108, pp.B6 2293. 10.1029/2002JB002157. hal-00097430 HAL Id: hal-00097430 https://hal.archives-ouvertes.fr/hal-00097430 Submitted on 11 Jan 2021 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. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B6, 2293, doi:10.1029/2002JB002157, 2003 Komatiites, kimberlites, and boninites Nicholas Arndt Laboratoire de Ge´odynamique des Chaıˆnes Alpines, Universite´ de Grenoble, Grenoble, France Received 16 August 2002; revised 21 January 2003; accepted 26 February 2003; published 6 June 2003. [1] When the mantle melts, it produces ultramafic magma if the site of melting is unusually deep, the degree of melting is unusually high, or the source is refractory. For such melting to happen, the source must be unusually hot or very rich in volatiles. Differing conditions produce a spectrum of ultramafic magma types. Komatiites form by high degrees of melting, at great depths, of an essentially anhydrous source. Barberton- type komatiites are moderately high degree melts from a particularly hot and deep source; Munro-type komatiites are very high degree melts of a slightly cooler source.