DOCSLIB.ORG

Magnetic Properties of Neogene Regional Dikes from East Iceland

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Magnetic Properties of Neogene Regional Dikes from East Iceland ISSN: 1402-1757 ISBN 978-91-7439-XXX-X Se i listan och fyll i siffror där kryssen är LICENTIATE T H E SI S Per ErikssonPer Magnetic Properties of Neogene Regional East from Dikes Iceland with Special Reference to Magma Flow Department of Chemical Engineering and Geosciences Division of Applied Geophysics Magnetic Properties of Neogene Regional ISSN: 1402-1757 ISBN 978-91-7439-191-6 Dikes from East Iceland with Special Luleå University of Technology 2010 Reference to Magma Flow Per Eriksson SWEDISH STUDIES ON ICELANDIC GEOLOGY Dissertation presented to the Faculty in Candidacy for the Degree of Licentiate of Technology at the Division of Applied Geophysics Department of Chemical Engineering and Geosciences at Luleå University of Techonology Sweden Magnetic properties of Neogene regional dikes from east Iceland with special reference to magma flow Examinans Per I. Eriksson Thesis Supervisors Examinator Discutant Prof. Sten-Åke Elming Prof. Sten-Åke Elming Dr. Håkan Mattsson Dr. Morten S. Riishuus Dr. Freysteinn Sigmundsson November 2010 Printed by Universitetstryckeriet, Luleå 2010 ISSN: 1402-1757 ISBN 978-91-7439-191-6 Luleå 2010 www.ltu.se THESIS SUMMARY This thesis deals with rock magnetic measurements on Neogene dikes from the eastern fjords of Iceland. A vast amount of dikes generally striking north-north-east occur as swarms in the glacially eroded lava pile. They are considered as the underlying extensions of fissure swarms in active volcanic systems which like the dike swarms converge at central volcanoes. The dike swarms and associated central volcanoes are uncovered by ca. 1500 m of glacial erosion, leaving the upper parts of these igneous units bare. Two research papers have been prepared based on field studies and measurements of rock magnetism on carefully chosen occurrences of Icelandic dikes in order to test contradicting models of dike origin. The manuscripts are included in the thesis. The first is a detail study of a single composite dike, with a core of fine grained quartz-porphyry surrounded by dolerite margins. The core of the dike was sampled in three locations, separated by ∼12 km and measured for magnetic remanence and anisotropy of magnetic susceptibility. Magma flow direction in this dike was interpreted using the mirror imbrication of the minor susceptibility axes from each margin of the quartz-porphyry core of the dike. The flow regime in all three locations showed a marked flow component from north to south, supported by field evidence in the form of parabolically aligned enclaves, and shear folds. Statistical procedures of bootstrapping was utilized to define the flow and handle imbrication in both the vertical and horizontal plane thus defining direction and inclination of flow. The main contribution of this paper was to prove that anisotropy of magnetic susceptibility used to infer flow direction may give consistent and reliable results, and to present new ways (to use old techniques) to define magma flow directions. The same technique used to infer flow in paper one has sub-sequentially been applied to a far larger set of mafic dikes, extending northeast from the exhumed Álftafjörður central volcano. The second paper documents that the flow regimes from the mafic dikes showed a predominantly horizontal flow from the central volcano, supporting tectonic models that suggest shallow magma chambers to be the source of the dikes. The thesis further discusses the results from these studies in comparison to other studies on Icelandic dikes where the magma flow is determined by the direction of the major susceptibility axis. TABLE OF CONTENTS 1 Preface 2 2 Introduction 3 3 General Geology of Iceland 5 3.1Tectonics................................ 7 3.2Bedrock................................. 7 3.3DikeFormation............................. 9 3.4ErosionalDepth............................. 10 4 The Aims of the Study 13 4.1 Methods . ............................ 13 4.2Samplecollection............................ 14 5 Theory on Rock Magnetic Properties 16 5.1MagneticPropertiesofOxideMinerals................. 17 5.2 Anisotropy of Magnetic Susceptibility . .............. 19 5.3MagmaFlowFabrics.......................... 22 5.4SourcesofError:ADiscussion..................... 27 6 Propagation of Flow in a Single Composite Dike 30 7 Emplacement of the Álftafjörður Dike Swarm 34 8 Comparison Between this Work and Other AMS Studies 37 9 Perspectives of Future Work 40 10 Sammanfattning av Avhandlingen på Svenska 44 11 Acknowledgements 46 Thesis Bibliography 47 Appendices I Appendix – Paper 1 In review for Journal of Volcanology and Geothermal Research II Appendix – Paper 2 To be submitted to Journal of Structural Geology III Appendix – Tables Tables A–D containing data used in thesis PREFACE HE work here presented commenced in June in the year 2007 and finished Tin November in the year of 2010. The work that underlies and merits this dissertation has been carried out at the Nordic Volcanological Center at the Institute of Earth Sciences, University of Iceland, Reykjavík, where I have been employed as a research fellow for some time. Much of the ideas for the research presented here originate at this institute whereas the expertise on and laboratory facilities for the magnetic techniques used have been supplied from Luleå University of Technology in Sweden, where this study was originally initiated. The process of understanding not only the complicated theory of rock magnetism, demagnetization techniques, the stability of the magnetic remanence and the subtle yet profound difference between study of remanence and of susceptibility with all the problematic non-simplicity of the latter field has been a time-consuming and sometimes frustrating work. Nevertheless, I am pleased to present this thesis and of the underlying work and I may contently say that my understanding of both the nature of rock magnetism and its uses within geology as well as the nature of scientific inquiry itself has broadened. During the study many questions has been raised, not only regarding methods used but also on epistemology. I hope that this thesis will not only be valuable to geologists interested in dike propagation in volcanic systems but also to geology students using anisotropy of magnetic susceptibility for the historical oversight on the matter. Per Eriksson, Hortlax November 2010 2 MAGNETIC PROPERTIES OF NEOGENE REGIONAL DIKES FROM EAST ICELAND WITH SPECIAL REFERENCE TO MAGMA FLOW Figure 1 – View of the north side of Fáskrúðsfjörður in east Iceland close to the fjord inlet. This plate illustrates the fjord landscape of east Iceland, carved out by glacial erosion since the onset of glaciations since the Plio-Pleistocene (Geirsdóttir, 1990; Geirsdóttier and Eiríksson, 1994; Geirsdóttir et al., 2007; Eiríksson, 2008). The gentle dip of the lava pile toward the paleo-rift axis caused by burial, loading and subsequent transportation by the extensive rifting is evident (Pálmason, 1986). The dikes visible in the mountain sides represent the downward continuation of the fissure swarms stretching from central volcanoes and neatly converge to a density maximum in the middle of the figure, note also that the density of dikes diminish with altitude (Bodvarsson and Walker, 1964; Helgason and Zentilli, 1985). INTRODUCTION HE aims of this study has been to test models of and to quantify fossilized Tflow directions in dikes using anisotropy of magnetic susceptibility (AMS) measurements, and to increase the knowledge on the mode of emplacement of dikes in the crust. The origin of dikes in the volcanic systems of Iceland is currently debated. Models explaining the origins of regional dike swarms as processes related to shallow magma chambers situated under central volcanoes have been proposed (Gudmundsson, 1983; Sigurdsson and Sparks, 1978; Sigurdsson, 1987; Buck et al., 3 2006; Paquet et al., 2007). Models explaining the origin of regional dikes from deep magma reservoirs has also been proposed (Gudmundsson, 1990, 1995). A combination of the two models were laid out by Walker (1992). These models differ among other things in which mode the propagation of flow in the dikes take. One method applied to obtain magma flow directions in dikes, and thus possibly constrain these models, is anisotropy of magnetic susceptibility measurements from dike margins. AMS defines an average of the spatial distribution of magnetic minerals, given that absence of magnetic interactions (Tarling and Hrouda, 1993; Cañón-Tapia, 1996, 2001). Ideally, AMS measures the magnetic mineral fabric, in itself imposed by the chain silicate mineral fabric and thus reflecting the silicate fabric (Hargraves et al., 1991). When magma flows in a dike it acts like an laminar flow trough a pipe conduit (Blanchard et al., 1979; Coward, 1980; Philpotts and Philpotts, 2007). At the margins of the dike simple shear stress regimes form alignment of minerals and vesicles in a pattern (Gay, 1968; Ghosh and Ramberg, 1976; Shelley, 1985), enabling absolute flow direction to be discerned. This thesis will treat the geology of Iceland, then shortly describe the underlying reasons for this study. The justification is followed by a theory section where the theoretical background and method of the sampling and analytical work is presented, some methodological remarks are also made. The major results from the two manuscripts are then presented followed by a discussion comparing this work with other modern works that apply AMS to study propagation of Neogene dikes in Iceland. Future prospects for research is also discussed. The discussion
Load more

Recommended publications
  • On Fluid Flow and Mineral Alteration in Fractured Caprock of Magmatic Hydrothennal Systems
    LBNL~,44804 Preprint ERNEST ORLANDO LAWRENCE BERKELEY NATIONAL LABORATORY On Fluid Flow and Mineral Alteration in Fractured Caprock of Magmatic Hydrothennal Systems Tianfu Xu and Karsten Pruess Earth Sciences Division February 2000 Submitted to Journal ofGeophysical Research ..;, ' '., --" c. - /" .. DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. LBNL-44804 On Fluid Flow and Mineral Alteration in Fractured Caprock of Magmatic Hydrothermal Systems Tianfu Xu and Karsten Pruess Earth Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720. Submitted to Journal o/Geophysical Research February 2000 . This work was supported by the Laboratory Directed Research and Development Program of the Ernest Orlando Lawrence Berkeley National Laboratory, and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Geothermal and Wind Technologies, of the U.S.
    [Show full text]
  • A Review of Feldspar Alteration and Its Geological Significance in Sedimentary Basins from Shallow Aquifers to Deep Hydrocarbon
    Originally published as: Yuan, G., Cao, Y., Schulz, H.-M., Hao, F., Gluyas, J., Liu, K., Yang, T., Wang, Y., Xi, K., Li, F. (2019): A review of feldspar alteration and its geological significance in sedimentary basins: From shallow aquifers to deep hydrocarbon reservoirs. - Earth-Science Reviews, 191, pp. 114—140. DOI: http://doi.org/10.1016/j.earscirev.2019.02.004 Earth-Science Reviews 191 (2019) 114–140 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev A review of feldspar alteration and its geological significance in sedimentary basins: From shallow aquifers to deep hydrocarbon reservoirs T ⁎ ⁎ Guanghui Yuana,b, , Yingchang Caoa,b, , Hans-Martin Schulzc, Fang Haoa, Jon Gluyasd, Keyu Liua, Tian Yanga, Yanzhong Wanga, Kelai Xia, Fulai Lia a Key laboratory of Deep Oil and Gas, School of Geosciences, China University of Petroleum, Qingdao, Shandong 266580, China b Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China c GFZ German Research Centre for Geosciences, Section 4.3, Organic Geochemistry, Telegrafenberg, D-14473 Potsdam, Germany d Department of Earth Sciences, Durham University, Durham DH1 3LE, UK ARTICLE INFO ABSTRACT Keywords: The feldspar group is one of the most common types of minerals in the earth's crust. Feldspar alteration (in- Feldspar alteration cluding the whole processes of feldspar dissolution, transfer of released solutes, and secondary mineral pre- Dissolution mechanisms cipitation) is ubiquitous and important in fields including resources and environmental sciences. This paper Rate law provides a critical review of feldspar alteration and its geological significance in shallow aquifers to deep hy- Organic-inorganic interaction drocarbon reservoirs, as assessed from peer-reviewed paper in the literature.
    [Show full text]
  • Petrography, Geochemistry, and Alteration of Country Rocks from the Bosumtwi Impact Structure, Ghana
    Meteoritics & Planetary Science 42, Nr 4/5, 513–540 (2007) Abstract available online at http://meteoritics.org Petrography, geochemistry, and alteration of country rocks from the Bosumtwi impact structure, Ghana Forson KARIKARI1*, Ludovic FERRIÈRE1, Christian KOEBERL1, Wolf Uwe REIMOLD2, and Dieter MADER1 1Center for Earth Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria 2Museum of Natural History (Mineralogy), Humboldt University, Invalidenstrasse 43, D-10115 Berlin, Germany *Corresponding author. E-mail: [email protected] (Received 27 October 2006; revision accepted 18 January 2007) Abstract–Samples of the country rocks that likely constituted the target rocks at the 1.07 Myr old Bosumtwi impact structure in Ghana, West Africa, collected outside of the crater rim in the northern and southern parts of the structure, were studied for their petrographic characteristics and analyzed for their major- and trace-element compositions. The country rocks, mainly meta-graywacke, shale, and phyllite of the Early Proterozoic Birimian Supergroup and some granites of similar age, are characterized by two generations of alteration. A pre-impact hydrothermal alteration, often along shear zones, is characterized by new growth of secondary minerals, such as chlorite, sericite, sulfides, and quartz, or replacement of some primary minerals, such as plagioclase and biotite, by secondary sericite and chlorite. A late, argillic alteration, mostly associated with the suevites, is characterized by alteration of the melt/glass clasts in the groundmass of suevites to phyllosilicates. Suevite, which occurs in restricted locations to the north and to the south-southwest of the crater rim, contains melt fragments, diaplectic quartz glass, ballen quartz, and clasts derived from the full variety of target rocks.
    [Show full text]
  • Ontong Java and Kerguelen Plateaux: Cretaceous Icelands?
    Journal of the Geological Society, London, Vol. 152, 1995, pp. 1047-1052, 4 figs. Printed in Northern Ireland Ontong Java and Kerguelen Plateaux: Cretaceous Icelands? M. F. COFFIN & L.M. GAHAGAN Institute for Geophysics, The University of Texas at Austin, 8701 North Mopac Expressway, Austin, Texas 78759-8397, USA Abstract: Together with Iceland, the two giant oceanic plateaux, Ontong Java in the western Pacific and Kerguelen/Broken Ridge in the Indian Ocean, are accumulations of mafic igneous rock which were not formed by 'normal' seafloor spreading. We compare published geochronological, crustal structure, and subsidence results with tectonic fabric highlighted in new satellite-derived free-air gravity data from the three igneous provinces, and conclude that existing evidence weighs lightly against the Ontong Java and Kerguelen plateaux originating at a seafloor spreading centre. Keywords: Iceland, Ontong Java Plateau, Kerguelen Plateau, plumes, hot spots. The two giant oceanic plateaux, Ontong Java in the western Age constraints Pacific, and Kerguelen in the south-central Indian Ocean (Fig. 1), and Iceland are among the best-studied examples of The vast bulk of crust in the ocean basins is dated using large-scale mafic magmatism not resulting solely from magnetic anomalies created by the interplay between the 'normal' seafloor spreading. Analogues on the continents, seafloor spreading process and the alternating polarity of the continental flood basalts, are demonstrably not created by Earth's magnetic field. Mesozoic and Cenozoic marine seafloor spreading, although controversy persists as to magnetic anomalies, summarized globally by Cande et al. whether or not lithospheric extension must precede their (1989), are most commonly tied to geological time through emplacement.
    [Show full text]
  • Origin of the High Elevated Pyrenean Peneplain Julien Babault, Jean Van Den Driessche, Stéphane Bonnet, Sébastien Castelltort, Alain Crave
    Origin of the high elevated Pyrenean peneplain Julien Babault, Jean van den Driessche, Stéphane Bonnet, Sébastien Castelltort, Alain Crave To cite this version: Julien Babault, Jean van den Driessche, Stéphane Bonnet, Sébastien Castelltort, Alain Crave. Origin of the high elevated Pyrenean peneplain. Tectonics, American Geophysical Union (AGU), 2005, 24 (2), art. no. TC2010, 19 p. 10.1029/2004TC001697. hal-00077900 HAL Id: hal-00077900 https://hal.archives-ouvertes.fr/hal-00077900 Submitted on 29 Jun 2016 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. TECTONICS, VOL. 24, TC2010, doi:10.1029/2004TC001697, 2005 Origin of the highly elevated Pyrenean peneplain Julien Babault, Jean Van Den Driessche, and Ste´phane Bonnet Ge´osciences Rennes, UMR CNRS 6118, Universite´ de Rennes 1, Rennes, France Se´bastien Castelltort Department of Earth Sciences, Eidgenossische Technische Hochschule-Zentrum, Zurich, Switzerland Alain Crave Ge´osciences Rennes, UMR CNRS 6118, Universite´ de Rennes 1, Rennes, France Received 9 June 2004; revised 5 December 2004; accepted 13 December 2004; published 19 April 2005. [1] Peneplanation of mountain ranges is generally base level in the penultimate stage of a humid, fluvial considered the result of long-term erosional processes geomorphic cycle.’’ They specify that ‘‘peneplain’’ also that smooth relief and lower elevation near sea level.
    [Show full text]
  • Peneplanation and Lithosphere Dynamics in the Pyrenees
    Peneplanation and lithosphere dynamics in the Pyrenees Gemma De Vicente I Bosch, Jean Van den Driessche, Julien Babault, Alexandra Robert, Alberto Carballo, Christian Le Carlier de Veslud, Nicolas Loget, Caroline Prognon, Robert Wyns, Thierry Baudin To cite this version: Gemma De Vicente I Bosch, Jean Van den Driessche, Julien Babault, Alexandra Robert, Al- berto Carballo, et al.. Peneplanation and lithosphere dynamics in the Pyrenees. Comptes Rendus G´eoscience,Elsevier Masson, 2016, From rifting to mountain building: the Pyrenean Belt, 348 (3-4), pp.194-202. <10.1016/j.crte.2015.08.005>. <insu-01241175> HAL Id: insu-01241175 https://hal-insu.archives-ouvertes.fr/insu-01241175 Submitted on 4 Feb 2016 HAL is a multi-disciplinary open access L'archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destin´eeau d´ep^otet `ala diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publi´esou non, lished or not. The documents may come from ´emanant des ´etablissements d'enseignement et de teaching and research institutions in France or recherche fran¸caisou ´etrangers,des laboratoires abroad, or from public or private research centers. publics ou priv´es. Distributed under a Creative Commons Attribution - NonCommercial - NoDerivatives 4.0 International License G Model CRAS2A-3281; No. of Pages 9 C. R. Geoscience xxx (2015) xxx–xxx Contents lists available at ScienceDirect Comptes Rendus Geoscience ww w.sciencedirect.com Tectonics, Tectonophysics Peneplanation
    [Show full text]
  • Effects of Hydrothermal Alteration on the Geomechanics of Degradation at the Bagdad Mine, Arizona
    Effects of Hydrothermal Alteration on the Geomechanics of Degradation at the Bagdad Mine, Arizona Item Type text; Electronic Thesis Authors Coutinho, Paulo Citation Coutinho, Paulo. (2020). Effects of Hydrothermal Alteration on the Geomechanics of Degradation at the Bagdad Mine, Arizona (Master's thesis, University of Arizona, Tucson, USA). Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 05/10/2021 14:56:11 Link to Item http://hdl.handle.net/10150/648603 EFFECTS OF HYDROTHERMAL ALTERATION ON THE GEOMECHANICS OF DEGRADATION AT THE BAGDAD MINE, ARIZONA by Paulo Coutinho ______________________________________________________________________________ Copyright © Paulo Coutinho 2020 A Thesis Submitted to the Faculty of the DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN MINING, GEOLOGICAL, AND GEOPHYSICAL ENGINEERING In the Graduate College THE UNIVERSITY OF ARIZONA 2020 2 3 Acknowledgements I would like to extend my sincere gratitude to my advisors, Dr. John Kemeny and Dr. Isabel Barton, for their crucial role in guiding me through my graduate studies. I would also like to thank my thesis committee members, Mr. Keith Taylor, for his valuable support and enlightening comments. Dr. Sergio Castro Reino for his resources and experience involving rock mass degradation. Furthermore, I would like to thank my coworkers at Freeport McMoRan Inc. for providing me geology and geological engineering knowledge pertaining to the Bagdad deposit, and Call & Nicholas for their constructive criticisms regarding my modeling techniques.
    [Show full text]
  • Coupled Mineral Alteration and Oil Degradation in Thermal Oil-Water-Feldspar Systems and Implications for Organic-Inorganic Interactions in Hydrocarbon Reservoirs
    Available online at www.sciencedirect.com ScienceDirect Geochimica et Cosmochimica Acta 248 (2019) 61–87 www.elsevier.com/locate/gca Coupled mineral alteration and oil degradation in thermal oil-water-feldspar systems and implications for organic-inorganic interactions in hydrocarbon reservoirs Guanghui Yuan a,b,⇑, Yingchang Cao a,⇑, Nianmin Zan a, Hans-Martin Schulz c Jon Gluyas d, Fang Hao a, Qiang Jin a, Keyu Liu a, Yanzhong Wang a Zhonghong Chen a, Zhenzhen Jia a a Key Laboratory of Deep Oil and Gas, School of Geosciences, China University of Petroleum, Qingdao 266580, China b Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, No. 62, Fuzhou South Road, Qingdao 266071, China c GFZ German Research Centre for Geosciences, Section 4.3, Organic Geochemistry, Telegrafenberg, D-14473 Potsdam, Germany d Department of Earth Sciences, Durham University, Durham DHs 3LE, UK Received 19 January 2018; accepted in revised form 2 January 2019; available online 11 January 2019 Abstract Organic-inorganic interactions after oil charging are critical for determining the ongoing evolution of hydrocarbons and rock quality in water-wet siliciclastic reservoirs. It is the conceptual approach of this study to simulate and decipher these interactions by using quantitative analyses of the interrelated changes of minerals, water, hydrocarbons, gases, and organic acids in heated oil-water-rock systems. The experimental results show that organic-inorganic interactions occur between the organic oil and inorganic feldspar in the presence of water. Water promotes the oil degradation by an extra supply of H+ and OHÀ ions. In the oil-water-rock systems, mutual exchanges of H+ and OHÀ ions among minerals, water, and hydrocarbons probably result in the mutual interactions between oil degradation and mineral alteration, with water serving as a matrix for the ion exchange.
    [Show full text]
  • Pace of Landscape Change and Pediment Development in the Northeastern Sonoran Desert, United States
    Pace of Landscape Change and Pediment Development in the Northeastern Sonoran Desert, United States Phillip H. Larson,* Scott B. Kelley,y Ronald I. Dorn,y and Yeong Bae Seongz *Department of Geography, Minnesota State University ySchool of Geographical Sciences and Urban Planning, Arizona State University zDepartment of Geography Education, Korea University Pediments of the Sonoran Desert in the United States have intrigued physical geographers and geomorpholo- gists for nearly a century. These gently sloping bedrock landforms are a staple of the desert landscape that mil- lions visit each year. Despite the long-lived scientific curiosity, an understanding of the processes operating on the pediment has remained elusive. In this study we revisit the extensive history of pediment research. We then apply geospatial, field, and laboratory cosmogenic 10Be nuclide dating and back-scattered electron micros- copy methods to assess the pace and processes of landscape change on pediment systems abutting the Salt River in Arizona. Our study focuses on the Usery pediments linked to base-level fluctuations (river terraces) of the Salt River. Relict pediment surfaces were reconstructed with dGPS data and kriging methodologies utilized in ArcGIS—based on preserved evidence of ancient pediment surfaces. 10Be ages of Salt River terraces established a chronology of incision events, where calculating the volume between the reconstructed relict pediment and modern surface topography established minimum erosion rates ( 41 mm/ka to 415 mm/ka). Pediment area and length appear to have a positive correlation to erosion rate and» development» of planar pediment surfaces. Field and laboratory observations reveal that pediment systems adjust and stabilize at each Salt River terrace.
    [Show full text]
  • Identification of Hydrothermal Alteration Minerals for Exploring
    remote sensing Article Identification of Hydrothermal Alteration Minerals for Exploring Gold Deposits Based on SVM and PCA Using ASTER Data: A Case Study of Gulong Kai Xu 1,2,3, Xiaofeng Wang 1, Chunfang Kong 1,2,4,* , Ruyi Feng 1, Gang Liu 1 and Chonglong Wu 1,2 1 School of Computer, China University of Geosciences, Wuhan 430074, China; [email protected] (K.X.); [email protected] (X.W.); [email protected] (R.F.); [email protected] (G.L.); [email protected] (C.W.) 2 Innovation Center of Mineral Resources Exploration Engineering Technology in Bedrock Area, Ministry of Natural Resources, Guiyang 550081, China 3 Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education, Wuhan 430074, China 4 National-Local Joint Engineering Laboratory on Digital Preservation and Innovative Technologies for the Culture of Traditional Villages and Towns, Hengyang 421000, China * Correspondence: [email protected]; Tel.: +86-027-6788-3286 Received: 3 December 2019; Accepted: 11 December 2019; Published: 13 December 2019 Abstract: Dayaoshan, as an important metal ore-producing area in China, is faced with the dilemma of resource depletion due to long-term exploitation. In this paper, remote sensing methods are used to circle the favorable metallogenic areas and find new ore points for Gulong. Firstly, vegetation interference was removed by using mixed pixel decomposition method with hyperplane and genetic algorithm (GA) optimization; then, altered mineral distribution information was extracted based on principal component analysis (PCA) and support vector machine (SVM) methods; thirdly, the favorable areas of gold mining in Gulong was delineated by using the ant colony algorithm (ACA) optimization SVM model to remove false altered minerals; and lastly, field surveys verified that the extracted alteration mineralization information is correct and effective.
    [Show full text]
  • Application of Imaging Spectroscopy for Mineral Exploration in Alaska: a Study Over Porphyry Cu Deposits in the Eastern Alaska Range
    Economic Geology, v. 113, no. 2, pp. 489–510 Application of Imaging Spectroscopy for Mineral Exploration in Alaska: A Study over Porphyry Cu Deposits in the Eastern Alaska Range Garth E. Graham,1,† Raymond F. Kokaly,2 Karen D. Kelley,1 Todd M. Hoefen,2 Michaela R. Johnson,2 and Bernard E. Hubbard3 1 U.S. Geological Survey, PO Box 25046, MS 973, Denver Federal Center, Denver, Colorado 80225 2 U.S. Geological Survey, PO Box 25046, MS 964, Denver Federal Center, Denver, Colorado 80225 3 U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 954, Reston, Virginia 20192 Abstract The U.S. Geological Survey tested the utility of imaging spectroscopy (also referred to as hyperspectral remote sensing) as an aid to regional mineral exploration efforts in remote parts of Alaska. Airborne imaging spectrom- eter data were collected in 2014 over unmined porphyry Cu deposits in the eastern Alaska Range using the HyMap™ sensor. Maps of the distributions of predominant minerals, made by matching reflectance signatures in the remotely sensed data to reference spectra in the shortwave infrared region, do not uniquely discriminate individual rock units. However, they do highlight hydrothermal alteration associated with porphyry deposits and prospects hosted mostly within the Nabesna pluton. In and around porphyry Cu deposits at Orange Hill and Bond Creek, unique spectral signatures are related to variations in chlorite and white mica abundance and their chemi- cal composition. This is best revealed in the longer-wavelength 2,200-nm Al-OH absorption feature positions in pixels spectrally dominated by white mica proximal to porphyry deposits.
    [Show full text]
  • Thin Crust As Evidence for an Inherited Mantle Depletion Supporting the Marion Rise
    Thin Crust as Evidence for an Inherited Mantle Depletion Supporting the Marion Rise Huaiyang Zhou* and Henry JB Dick** *State Key Laboratory of Marine Geology, Tongji University, Shanghai, China **Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA … …… …… …… …… …… …… …… …… …… …… …… …… …… …… ….. … The global ridge system is dominated by oceanic rises reflecting large variations in axial depth associated with mantle hotspots. The little studied Marion Rise is as large as the Icelandic, considering length and depth, but has an axial rift rather than a high nearly its entire length. Uniquely, along the SW Indian Ridge systematic sampling allows direct examination of crustal architecture over its full length. Unlike Iceland, peridotites are extensively exposed high over the rise. This shows for the 1st time that the crust is generally thin, and often missing over a rifted rise. Thus the rise must be largely an isostatic response to ancient melting events that created low-density depleted mantle beneath the ridge rather than thickened crust and/or a large thermal anomaly. The likely origin for the depleted mantle is that emplaced into the African asthenosphere during the Karoo and Madagascar flood basalt events. Following Morgan 1, common wisdom equates oceanic rises to a hot fertile mantle plume producing a flow of plume-derived mantle to the ridge and down the sub-axial asthenospheric channel, resulting in elevated mantle temperature, ridge topography, and thickened igneous crust (the mantle wedge hypothesis, e.g.: 2). Studies of the Reykjanes Ridge support this, with seismic crust thickening from ~6 km near the Gibbs FZ for 1600 km to ~18 km at the Reykjanes Peninsula e.g.: 3.
    [Show full text]