MAGM-1: Arcos Magmáticos Fanerozoicos

Total Page：16

File Type：pdf, Size：1020Kb

MAGM-1: Arcos magmáticos fanerozoicos Miocene to recent geological evolution of the Lazufre segment in the Andean volcanic arc José Antonio Naranjo1, Francisco Hevia1, Victor Villa1, Cristian Ramirez1. (1) Geología Regional, Servicio Nacional de Geología y Minería The Lazufre bulging zone (25°16S, 68°29W), with 47 km by 40 km, NE oriented intumescence in the area of the Pleistocene- Holocene Azufre, Cordón del Azufre, Bayo and Lastarria volcanic complexes, has been a major focus of study over the past few decades. Since 1998, InSar interferometric analysis has shown structural deformation, likely a result of an active magmatic and hydrothermal system. Our new mapping provides clues about the causes and possible consequences of this deformation, based on the reinterpretation of important structures or regional lineaments. The bulge is located upon the hanging-wall of Pedernales- Arizaro NE-SW trending Middle Miocene major thrust fault. The footwall of this fault was previously affected by a major explosive activity producing the Los Colorados caldera at ~9.4-9.8 Ma, the source of the homonymous 115-185 km3 ignimbrite. Conjugated at ~30° to the Pedernales-Arizaro thrust, the Imilac-Salina del Fraile oblique, slightly dextral strike-slip fault, constitutes a major structure in the area, which favored the opening of tectonic spaces, parallel to the Los Colorados caldera-Lazufre bulge alignment. Notably, since the Late Pliocene, volcanism has been concentrated in the Lazufre intumescence, including extrusion of ~120 km3 total lava volume. The lava accumulation rate estimated since Late Pliocene to the present at Lazufre bulging zone area is approximately one third lower than the rate estimated for the generation of the Los Colorados caldera. The migration of volcanic activity from this Miocene caldera area to the northwestern Lazufre bulging zone could be the consequence of local strain field variations which opened tectonic space that favored magmatic ascent and storage. Este trabajo es parte del programa regular de cartografía del SERNAGEOMIN y contó con el financiamiento del Plan Nacional de Geología-PNG. This work is part of the SERNAGEOMIN’s regular mapping program and was supported by the National Plan of Geology-PNG. 863.

Copy Link

Recommended publications

Full-Text PDF (Final Published Version)
Pritchard, M. E., de Silva, S. L., Michelfelder, G., Zandt, G., McNutt, S. R., Gottsmann, J., West, M. E., Blundy, J., Christensen, D. H., Finnegan, N. J., Minaya, E., Sparks, R. S. J., Sunagua, M., Unsworth, M. J., Alvizuri, C., Comeau, M. J., del Potro, R., Díaz, D., Diez, M., ... Ward, K. M. (2018). Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes. Geosphere, 14(3), 954-982. https://doi.org/10.1130/GES01578.1 Publisher's PDF, also known as Version of record License (if available): CC BY-NC Link to published version (if available): 10.1130/GES01578.1 Link to publication record in Explore Bristol Research PDF-document This is the final published version of the article (version of record). It first appeared online via Geo Science World at https://doi.org/10.1130/GES01578.1 . Please refer to any applicable terms of use of the publisher. University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes GEOSPHERE; v. 14, no. 3 M.E. Pritchard1,2, S.L. de Silva3, G. Michelfelder4, G. Zandt5, S.R. McNutt6, J. Gottsmann2, M.E. West7, J. Blundy2, D.H.
[Show full text]
Chiodi Et Al 2019.Pdf
Journal of South American Earth Sciences 94 (2019) 102213 Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Preliminary conceptual model of the Cerro Blanco caldera-hosted geothermal system (Southern Puna, Argentina): Inferences from T geochemical investigations ∗ A. Chiodia, , F. Tassib,c, W. Báeza, R. Filipovicha, E. Bustosa, M. Glok Gallid, N. Suzañoe, Ma. F. Ahumadaa, J.G. Viramontea, G. Giordanof,g, G. Pecorainoh, O. Vasellib,c a Instituto de Bio y Geociencias del NOA (IBIGEO, UNSa-CONICET), Av. 9 de Julio14, A4405BBA Salta, Argentina b Department of Earth Sciences, University of Florence, Via La Pira 4, 50121 Florence, Italy c CNR-IGG Institute of Geosciences and Earth Resources, Via La Pira 4, 50121 Florence, Italy d Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires (CIFICEN), Pinto 399, 7000, Buenos Aires, Argentina e Universidad Nacional de Jujuy, Argentina f Department of Sciences, University Roma Tre, 00146 Rome, Italy g CNR-IDPA Institute for Dynamics of Environmental Processes, Via M. Bianco, 20131 Milan, Italy h Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Palermo, Via Ugo La Malfa 153, 90146, Palermo, Italy ARTICLE INFO ABSTRACT Keywords: The Cerro Blanco Caldera (CBC) is the youngest collapse caldera system in the Southern Central Andes (Southern Hydrothermal system Puna, Argentina). The CBC is subsiding with at an average velocity of 0.87 cm/year and hosts an active geo- Fluid geochemistry thermal system. A geochemical characterization of emitted fluids was carried out based on the chemical and Geothermal prospection isotopic compositions of fumaroles, and thermal and cold springs discharged in this volcanic area with the aim of Quaternary caldera constructing the first hydrogeochemical conceptual model and preliminary estimate the geothermal potential.
[Show full text]
PLUTONS: Investigating the Relationship Between Pluton Growth and Volcanism in the Central Andes
Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes GEOSPHERE; v. 14, no. 3 M.E. Pritchard1,2, S.L. de Silva3, G. Michelfelder4, G. Zandt5, S.R. McNutt6, J. Gottsmann2, M.E. West7, J. Blundy2, D.H. Christensen7, N.J. Finnegan8, 9 2 10 11 7 12 2 13 2 6 doi:10.1130/GES01578.1 E. Minaya , R.S.J. Sparks , M. Sunagua , M.J. Unsworth , C. Alvizuri , M.J. Comeau , R. del Potro , D. Díaz , M. Diez , A. Farrell , S.T. Henderson1,14, J.A. Jay15, T. Lopez7, D. Legrand16, J.A. Naranjo17, H. McFarlin6, D. Muir18, J.P. Perkins19, Z. Spica20, A. Wilder21, and K.M. Ward22 1 10 figures; 3 tables Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA 2School of Earth Sciences, University of Bristol, BS8 1RJ, United Kingdom 3College of Earth, Ocean, and Atmospheric Science, Oregon State University, Corvallis, Oregon 97331, USA CORRESPONDENCE: pritchard@ cornell .edu 4Department of Geography, Geology and Planning, Missouri State University, 901 S. National Ave, Springfield, Missouri 65897, USA 5Department of Geosciences, The University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721-0001, USA CITATION: Pritchard, M.E., de Silva, S.L., Michel‑ 6School of Geosciences, University of South Florida, 4202 E. Fowler Avenue, Tampa, Florida 33620, USA felder, G., Zandt, G., McNutt, S.R., Gottsmann, 7Geophysical Institute, University
[Show full text]
The Growth of the Central Andes, 22°S–26°S
Downloaded from memoirs.gsapubs.org on January 15, 2015 The Geological Society of America Memoir 212 2015 The growth of the central Andes, 22°S–26°S J. Quade* M.P. Dettinger B. Carrapa P. DeCelles K.E. Murray Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA K.W. Huntington Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA A. Cartwright Mintec, Inc., 3544 East Fort Lowell Road, Tucson, Arizona 85716, USA R.R. Canavan Department of Geology, University of Wyoming, Laramie, Wyoming 82071, USA G. Gehrels Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA M. Clementz Department of Geology, University of Wyoming, Laramie, Wyoming 82071, USA ABSTRACT We synthesize geologic observations with new isotopic evidence for the timing and magnitude of uplift for the central Andes between 22°S and 26°S since the Paleocene. To estimate paleoelevations, we used the stable isotopic composition of carbonates and volcanic glass, combined with another paleoelevation indicator for the central Andes: the distribution of evaporites. Paleoelevation reconstruction using clumped isotope paleothermometry failed due to resetting during burial. The Andes at this latitude rose and broadened eastward in three stages during the Cenozoic. The ﬁ rst, in what is broadly termed the “Incaic” orogeny, ended by the late Eocene, when magmatism and deformation had elevated to ≥4 km the bulk (~50%) of what is now the western and central Andes. The second stage witnessed the gradual building of the easternmost Puna and Eastern Cordillera, starting with deforma- tion as early as 38 Ma, to >3 km by no later than 15 Ma.
[Show full text]
Oligo-Holocene Evolution of the Southern Part of the Central Andes: Volcanism and Tectonic
O EOL GIC G A D D A E D C E I H C I L E O S F u n 2 d 6 la serena octubre 2015 ada en 19 Oligo-Holocene evolution of the southern part of the Central Andes: volcanism and tectonic José Antonio Naranjo1*, Víctor Villa1, Cristián Ramírez1 and Carlos Pérez de Arce2 (1) Departamento de Geología Regional, Servicio Nacional de Geología y Minería, Av. Santa María 0104, Providencia, Santiago. (2) Laboratorio de Geocronología, Servicio Nacional de Geología y Minería, Tiltil 1993, Ñuñoa, Santiago. *Email: [email protected] Abstract: The complex evolution of the southern Central deformation. The main purpose of this work is to further Andes Volcanic Zone (SCAVZ) in Chile, between 25º and our understanding of the key processes involved in the 27º30’ S, has been elucidated based on comprehensive development of the Andean orogen and volcanic arc, in the mapping over recent years. Several volcanic pulses, SCAVZ, through new insights of the evolutionary stages. including volcanic complexes, calderas and ignimbrites, have been identified and their timing and kinematic constrained. As a result, nine Lower Miocene to Pleistocene ignimbrites units have been mapped and their Volcano-ignimbrite units probable caldera source identified, and the volcanoes have been grouped into six Lower Miocene to Holocene Volcanoes chronostratigraphic units. In addition, two main thrust systems of NE-SW and NS orientations are recognized. Based on geochronologic data, relative erosion rates, The first, located in the Precordillera, was active between stratigraphic relationships and geographic distributions, 25-10 Ma and extends over 200 km to the NE through the hundreds of volcanoes in the area have been grouped into Pedernales-Arizaro thrust fault.
[Show full text]
Originally Published As: Schnurr, WBW, Trumbull, RB
Originally published as: Schnurr, W. B. W., Trumbull, R. B., Clavero, J., Hahne, K., Siebel, W., Gardeweg, M. (2007): Twenty-five million years of felsic magmatism in the southern Central Volcanic Zone of the Andes: geochemistry and magma genesis of ignimbrites from 25-27°S, 67-72°W. - Journal of Volcanology and Geothermal Research, 166, 1, 17-46, DOI: 10.1016/j.jvolgeores.2007.06.005. Twenty-five million years of silicic volcanism in the southern Central Volcanic Zone of the Andes: geochemistry and magma genesis of ignimbrites from 25-27°S, 67-72°W W.B.W. Schnurr1, R.B. Trumbull2*, J. Clavero3, K. Hahne2, W. Siebel4, M. Gardeweg5 1 Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin, Germany 2 GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany 3 Servicio Nacional de Geología y Minería, Santiago, Chile 4 Institut für Geowissenschaften, Universität Tübingen, 72074 Tübingen, Germany 5 Aurum Consultores Servicios Geológicos y Mineros Ltda., Santiago, Chile Abstract Silicic volcanism in the Andean Central Volcanic Zone (CVZ) produced one of the world’s largest Neogene ignimbrite provinces. The largest and best known CVZ ignimbrites are located on the Altiplano-Puna plateau north of 24 °S. Their compositions and huge erupted volumes suggest an origin by large-scale crustal melting, and present-day geophysical anomalies in this region suggest still active zones of partial melting in the middle crust. Farther south in the CVZ, the Cerro Galán complex erupted ignimbrites in the late Miocene and Pliocene that are quite similar in volume and composition to those from north of 24 °S and they have a similar origin.
[Show full text]
Miocene to Holocene Geological Evolution of the Lazufre Segment in the Andean Volcanic Arc GEOSPHERE; V
Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Miocene to Holocene geological evolution of the Lazufre segment in the Andean volcanic arc GEOSPHERE; v. 15, no. 1 José A. Naranjo, Francisco Hevia, Víctor Villa, and Cristián A. Ramírez https://doi.org/10.1130/GES01352.1 Departamento de Geología Regional, Servicio Nacional de Geología y Minería, Av. Santa María #0104, Providencia, Santiago 7520405, Chile 6 figures; 2 tables ABSTRACT during the period of March 2003–May 2005, and they proposed that the great CORRESPONDENCE: est deformation could have a magmatic origin between 7 and 15 km deep, jose .naranjo@ sernageomin.cl The Lazufre bulging zone, in the area of the Pleistocene–Holocene Azufre, whereas a surface source related to hydrothermal fluids could have caused Cordón del Azufre, Bayo, and Lastarria volcanic complexes, has been a major only minor deformations detected during this same period. Later, for the pe CITATION: Naranjo, J.A., Hevia, F., Villa, V., and Ramírez, C.A., 2019, Miocene to Holocene geolog‑ focus of study over the past few decades. Since 1998, interferometric synthetic riod 2003–2006, Ruch et al. (2008, 2009) found that the deformation south of ical evolution of the Lazufre segment in the Andean aperture radar (InSar) analysis has shown structural deformation, likely a re- Lastarria volcanic complex affected an elongated area of 45 km by 55 km (1400 volcanic arc: Geosphere, v. 15, no. 1, p. 47–59, sult of an active magmatic and hydrothermal system. Our new mapping pro- km2) with a rise of up to ~3 cm/year.
[Show full text]
Miocene to Holocene Geological Evolution of the Lazufre Segment in the Andean Volcanic Arc GEOSPHERE; V
Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Miocene to Holocene geological evolution of the Lazufre segment in the Andean volcanic arc GEOSPHERE; v. 15, no. 1 José A. Naranjo, Francisco Hevia, Víctor Villa, and Cristián A. Ramírez https://doi.org/10.1130/GES01352.1 Departamento de Geología Regional, Servicio Nacional de Geología y Minería, Av. Santa María #0104, Providencia, Santiago 7520405, Chile 6 figures; 2 tables ABSTRACT during the period of March 2003–May 2005, and they proposed that the great CORRESPONDENCE: est deformation could have a magmatic origin between 7 and 15 km deep, jose .naranjo@ sernageomin.cl The Lazufre bulging zone, in the area of the Pleistocene–Holocene Azufre, whereas a surface source related to hydrothermal fluids could have caused Cordón del Azufre, Bayo, and Lastarria volcanic complexes, has been a major only minor deformations detected during this same period. Later, for the pe CITATION: Naranjo, J.A., Hevia, F., Villa, V., and Ramírez, C.A., 2019, Miocene to Holocene geolog‑ focus of study over the past few decades. Since 1998, interferometric synthetic riod 2003–2006, Ruch et al. (2008, 2009) found that the deformation south of ical evolution of the Lazufre segment in the Andean aperture radar (InSar) analysis has shown structural deformation, likely a re- Lastarria volcanic complex affected an elongated area of 45 km by 55 km (1400 volcanic arc: Geosphere, v. 15, no. 1, p. 47–59, sult of an active magmatic and hydrothermal system. Our new mapping pro- km2) with a rise of up to ~3 cm/year.
[Show full text]
Accepted Manuscript
Accepted Manuscript A middle miocene (13.5–12Ma) deformational event constrained by volcanism along the puna-eastern cordillera border, NW Argentina Alejandro Aramayo, Silvina Guzmán, Fernando Hongn, Cecilia del Papa, Carolina Montero-López, Masafumi Sudo PII: S0040-1951(17)30073-2 DOI: doi: 10.1016/j.tecto.2017.02.018 Reference: TECTO 127410 To appear in: Tectonophysics Received date: 24 May 2016 Revised date: 6 February 2017 Accepted date: 21 February 2017 Please cite this article as: Alejandro Aramayo, Silvina Guzmán, Fernando Hongn, Cecilia del Papa, Carolina Montero-López, Masafumi Sudo , A middle miocene (13.5–12Ma) deformational event constrained by volcanism along the puna-eastern cordillera border, NW Argentina. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Tecto(2017), doi: 10.1016/j.tecto.2017.02.018 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 A middle miocene (13.5 -12 ma) deformational event constrained by volcanism along the puna- eastern cordillera border, NW Argentina Alejandro Aramayo1, Silvina Guzmán1,2, Fernando Hongn1, Cecilia del Papa3, Carolina Montero-López1, Masafumi Sudo4 1Instituto de Bio y Geociencias del NOA (IBIGEO), CONICET-UNSa, 9 de julio 14, Rosario de Lerma (4405), Salta, Argentina, [email protected], [email protected], [email protected], [email protected] 2Institute of Earth Sciences Jaume Almera, ICTJA-CSIC, Lluis Sole i Sabaris s/n, 08028 Barcelona, Spain.
[Show full text]
Volcanism and Tectonism in the Southern Central Andes: Tempo, Styles, and Relationships GEOSPHERE, V
Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Volcanism and tectonism in the southern Central Andes: Tempo, styles, and relationships GEOSPHERE, v. 14, no. 2, p. XXX–XXX José Antonio Naranjo1, Víctor Villa1, Cristián Ramírez1 and Carlos Pérez de Arce2 1Departamento de Geología Regional, Servicio Nacional de Geología y Minería, Av. Santa María 0104, Providencia, Santiago, Chile doi:10.1130/GES01350.1 2Laboratorio de Geocronología, Servicio Nacional de Geología y Minería, Tiltil 1993, Ñuñoa, Santiago, Chile 8 figures; 1 table; 1 supplemental file CORRESPONDENCE: jose.naranjo@ sernageomin.cl ABSTRACT In this paper, we suggest a new model that integrates the coexistence and contemporaneity of compressive structures and the widespread development CITATION: Naranjo, J.A., Villa, V., Ramírez, C., and Pérez de Arce, C., 2018, Volcanism and tectonism An important objective of volcanic research is to establish a cause-and- of effusive constructional volcanism and explosive caldera volcanism along in the southern Central Andes: Tempo, styles, and effect relationship between the age of fault kinematics and volcanic arc evolu- the Andean Oligo-Miocene volcanic arc. relationships: Geosphere, v. 14, no. 2, p. 626–641, tion based on structural and stratigraphic evidence. The predominant hyper- doi:10.1130/GES01350.1. arid climate in the Central Andes since Miocene times makes it a world-class area for investigating the evolution of a volcanic arc. This region records the INTRODUCTION Science Editor: Raymond M. Russo Guest Associate Editor: Shanaka de Silva complete development of the late Cenozoic Andean volcanic arc. This study focuses on the interpretation of volcanism in the context of recently dated The southern Central Andes Volcanic Zone (SCVZ; e.g., Stern, 2004) be- Received 28 April 2016 tectonic structures along the southern Central Andes Volcanic Zone between tween 25° and 27° S (Fig.
[Show full text]
Oligo-Holocene Evolution of the Southern Part of the Central Andes: Volcanism and Tectonic
Oligo-Holocene evolution of the southern part of the Central Andes: volcanism and tectonic José Antonio Naranjo1*, Víctor Villa1, Cristián Ramírez1 and Carlos Pérez de Arce2 (1) Departamento de Geología Regional, Servicio Nacional de Geología y Minería, Av. Santa María 0104, Providencia, Santiago. (2) Laboratorio de Geocronología, Servicio Nacional de Geología y Minería, Tiltil 1993, Ñuñoa, Santiago. *Email: [email protected] Abstract: The complex evolution of the southern Central deformation. The main purpose of this work is to further Andes Volcanic Zone (SCAVZ) in Chile, between 25º and our understanding of the key processes involved in the 27º30’ S, has been elucidated based on comprehensive development of the Andean orogen and volcanic arc, in the mapping over recent years. Several volcanic pulses, SCAVZ, through new insights of the evolutionary stages. including volcanic complexes, calderas and ignimbrites, have been identified and their timing and kinematic constrained. As a result, nine Lower Miocene to Pleistocene ignimbrites units have been mapped and their Volcano-ignimbrite units probable caldera source identified, and the volcanoes have been grouped into six Lower Miocene to Holocene Volcanoes chronostratigraphic units. In addition, two main thrust systems of NE-SW and NS orientations are recognized. Based on geochronologic data, relative erosion rates, The first, located in the Precordillera, was active between stratigraphic relationships and geographic distributions, 25-10 Ma and extends over 200 km to the NE through the hundreds of volcanoes in the area have been grouped into Pedernales-Arizaro thrust fault. The second system, six Mio-Holocene volcanic chronostratigraphic units located within the volcanic arc, include N-S contractional (Naranjo et al., 2013 a, b, in prep.).
[Show full text]
Late Paleozoic–Early Triassic Magmatism on the Western Margin of Gondwana: Collahuasi Area, Northern Chile ⁎ Francisco Munizaga A, Victor Maksaev A, , C.M
Late Paleozoic–Early Triassic magmatism on the western margin of Gondwana: Collahuasi area, Northern Chile ⁎ Francisco Munizaga a, Victor Maksaev a, , C.M. Fanning b, S. Giglio c, G. Yaxley d, C.C.G. Tassinari e a Departamento de Geología, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile b Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia c Compañía Minera Doña Inés de Collahuasi, SCM, Pedro Lagos 1090, Iquique, Chile d Research School of Earth Sciences, Australian National University, Canberra ACT 0200, Australia e Instituto de Geociencias. Universidade de Sao Paulo, Brazil Abstract The basement in the ‘Altiplano’ high plateau of the Andes of northern Chile mostly consists of late Paleozoic to Early Triassic felsic igneous rocks (Collahuasi Group) that were emplaced and extruded along the western margin of the Gondwana supercontinent. This igneous suite crops out in the Collahuasi area and forms the backbone of most of the high Andes from latitude 20° to 22°S. Rocks of the Collahuasi Group and correlative formations form an extensive belt of volcanic and subvolcanic rocks throughout the main Andes of Chile, the Frontal Cordillera of Argentina (Choiyoi Group or Choiyoi Granite-Rhyolite Province), and the Eastern Cordillera of Peru. Thirteen new SHRIMP U–Pb zircon ages from the Collahuasi area document a bimodal timing for magmatism, with a dominant peak at about 300 Ma and a less significant one at 244 Ma. Copper–Mo porphyry mineralization is related to the younger igneous event. Initial Hf isotopic ratios for the ~300 Ma zircons range from about −2 to +6 indicating that the magmas incorporated components with a significant crustal residence time.
[Show full text]