DOCSLIB.ORG

Correlations Between Dikes of the Monument Swarm, Central Oregon, and Picture Gorge Basalt Flows

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Correlations Between Dikes of the Monument Swarm, Central Oregon, and Picture Gorge Basalt Flows Correlations between Dikes of the Monument Swarm, Central Oregon, and Picture Gorge Basalt Flows JONATHAN S. FRUCHTER* Center for Volcanology, University of Oregon, Eugene, Oregon 97403 STUART F. BALDWIN ABSTRACT INTRODUCTION Samples from 39 dikes and 11 other intrusive bodies of the Monument Dike Swarm Monument dike swarm in central Oregon were analyzed by in- strumental neutron activation analysis. All but two of the dikes This study of the Monument dike swarm (Waters, 1961; Wilcox have distinctive trace element compositions that clearly identify and Fisher, 1966; Figs. 1 and 2 here) is based on intensive sampling them as possible sources for the basalt flows at the Picture Gorge of the dikes and irregular sills mapped by Wilcox and Fisher (1966) type section and equivalent or stratigraphically lower flows else- near Kimberly and Monument as well as of scattered specimens ob- where in the region. The correlations are supported by tained from dikes in other areas now considered part of the paleomagnetic polarity measurements and by major element Monument swarm. Thayer (1957) included dikes located in the Al- analyses of nine of the samples. Key words: geochemistry, stratig- drich Mountains, and other dikes have been located by Thayer, raphy, trace element analyses, lava, intrusion, igneous rocks, chem- P. T. Robinson, and us (a list of sample locations is in the Society's ical analysis, volcanology. repository1). The dike swarm was considered a source for basalt of the Co- lumbia River Group as early as 1901 (Merriam, 1901). Because of its proximity, it has generally been regarded as the source of the Picture Gorge Basalt, although little evidence has been provided to clearly exclude other units of the Columbia River Group. To clarify this problem, the composition and natural remanent magnetism (NRM) of many of these dikes and other related intrusive bodies were studied in order to correlate them with known flow se- quences. Abundances of certain trace elements prove especially use- ful in providing characteristic "fingerprints" for the main chemical types (Osawa and Goles, 1970; Nathan and Fruchter, 1974). Chemical Types in the Columbia River Group The chemical and informal stratigraphic nomenclature proposed by Wright and others (1973) and amplified by Nathan and Fruch- ter (1974) is used in this paper. Wright and others (1973) defined several chemical types of Columbia River Basalt on the basis of major element composition and related them in a general way to several informal stratigraphic units they devised. Nathan and Fruchter (1974) showed that chemical types princi- pally associated with the lower, middle, and upper Yakima strati- graphic units of Wright and others (1973) can be clearly distin- guished from Picture Gorge types, using the elements La, Sm, Th, Fe, Sc, and Cr. High-Mg and low-Mg Picture Gorge chemical types are distinguished by well-defined differences in Cr and La. Sm and Fe are also useful in distinguishing high- and low-Mg Picture Gorge types, but the smaller separation of their ranges renders them slightly less diagnostic. Results Compositions of 50 samples from dikes and other intrusive bodies are given in Table 1. Table 2 lists major element analyses of nine representative dikes. In Figure 3, assignments are illustrated by comparing La and Cr contents of the dikes with those of the known chemical types re- 1 Copies of GSA supplementary material 75-7 may be ordered from Documents Sec- * Present address: Battelle, Pacific Northwest Laboratories, Richland, Washington retary, Geological Society of America, 3300 Penrose Place, Boulder, Colorado 80301, 99352. USA. Geological Society of America Bulletin, v. 86, p. 514-516, 3 figs., April 1975, Doc. no. 50409. 514 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/86/4/514/3443944/i0016-7606-86-4-514.pdf by guest on 26 September 2021 CORRELATIONS BETWEEN DIKES OF MONUMENT SWARM AND PICTURE GORGE BASALT FLOWS 515 Figure 2. Map of area of comprehensive sampling in Monument dike swarm between towns of Kimberly and Monument, Oregon. (R) indicates reverse polarity. TABLE 1. ANALYSES OF SAMPLES FROM MONUMENT DIKE SWARM, CENTRAL OREGON* lated to the Picture Gorge stratigraphic sequence. These two trace Sample* Fe Sc Cr Co La Sm Lu Na Hf Th La/Sm elements show the greatest differences in abundances between the («) (*) Picture Gorge and Yakima types. All other compositional data confirm those assignments (see Table 1 and Nathan and Fruchter, D-1 8.5 45 173 40 8.2 4.3 0.52 1.9 D-2 8.1 46 172 39 8.6 4.5 0.45 2.22 1.9 1974). D-3A 8.2 43 173 40 7.5 3.6 0.47 2.20 2.1 D-3B 8.2 45 171 40 7.3 3.7 0.48 2.0 As a precaution against the possibility that trace element data D-4 7.8 37 179 43 5.5 2.9 0.36 2.01 1.9 were not sufficient to make valid identifications, major element D-5 10.4 44 56 40 10.2 4.4 0.70 2.25 2.3 D-6A 10.1 43 28 35 11.4 4.6 0.71 2.26 2.3 analyses were done on nine of the samples (Table 2). The analyses D-6B 10.1 43 30 35 11.1 4.0 0.66 2.23 2.5 D-7A 8.4 42 198 44 6.6 3.6 0.44 2.18 2.1 confirmed the assignments made on the basis of trace elements; D-7B 8.2 40 191 44 6.5 3.4 0.40 2.09 1.9 they fit well within the compositional boundaries for Picture Gorge D-8 8.0 39 176 44 6.3 3.2 0.41 1.98 2.0 D-9 8.4 36 127 35 7.2 3.9 1.8 chemical types defined by Wright and others (1973). D-10 10.0 44 33 39 10.5 4.4 0.67 2.23 2.4 D-12 7.9 41 163 39 7.5 3.0 0.43 1.99 2.5 D-13 10.1 42 58 40 10.3 4.4 0.62 2.22 2.3 DISCUSSION OF CHEMICAL RESULTS D-14 10.8 45 <30 46 11.2 4.6 0.69 2.21 2.4 D-15 8.8 40 164 42 6.9 3.6 0.51 1.9 D-16 6.5 34 241 46 2.5 1.6 0.33 1.50 1.6 D-17 6.3 34 231 44 2.5 1.5 0.29 1.45 1.7 All but two dikes have compositions identifying them as belong- D-18 8.1 43 116 37 9.5 4.0 0.56 2.3 ing to either high- or low-Mg Picture Gorge chemical types. The D-19 7.6 41 155 42 6.1 2.8 0.45 1.80 2.2 D-20 8.3 43 86 38 8.3 3.8 0.51 2.19 2.2 possibility that a few Yakima-type dikes may exist in the swarm is 0-21 8.8 45 179 42 8.3 4.0 0.51 2.24 2.1 D-23 8.4 40 181 43 6.3 3.5 0.39 1.8 not precluded, but such dikes certainly constitute no more than a D-24 8.3 42 171 41 8.5 4.0 0.47 1.9 minor component of the swarm. D-25 8.3 43 77 40 8.6 3.7 0.49 2.06 2 8 1.0 2.3 D-26 9.2 43 105 42 9.5 4.1 0.57 2.13 3 0 1.3 2.3 The total range of composition of flows at and near the type sec- D-27 8.0 41 80 8.1 3.6 0.45 2.07 2 6 2.3 D-28 11.0 46 30 36 11.6 0.70 1.6 tion of the Picture Gorge Basalt is found in the dikes, suggesting D-29 8.6 42 168 46 7.5 3.6 0.44 2.07 2 5 0.6 2.1 that these Picture Gorge flows could all have originated in the D-30 9.0 47 163 43 7.7 3.7 0.50 2.17 2 4 0.9 2.1 D-31 8.9 44 187 44 8.4 3.6 0.47 2.01 2 6 0.8 2.1 Monument swarm. D-32 10.1 44 30 41 10.4 4.3 0.71 2.00 2 7 2.4 Dike samples D-16 and D-17 (Table 1) are compositionally un- D-33 10.2 44 30 40 10.6 4.4 0.67 1.92 3 0 1.4 2.4 D-34 9.7 44 75 43 11.3 4.5 0.62 2.15 3 2 1.7 2.5 like any of the chemical types associated with the Columbia River D-35 8.9 44 198 47 6.7 3.7 0.41 2.11 2 3 1.8 D-36 8.5 44 152 43 7.2 3.4 0.45 2.05 2 4 0.9 2.1 D-37 11.0 45 <30 39 11.7 4.8 0.74 2.17 3 9 1.6 2.4 TABLE 2. XRF MAJOR ELEMENT ANALYSES OF SAMPLES FROM MONUMENT D-38 10.9 44 <30 40 10.8 4.7 0.73 1.85 2 8 1.2 2.3 DIKE SWARM, CENTRAL OREGON D-39 9.7 42 <30 41 13.8 5.3 0.66 2.27 4 4 1.9 2.6 1-1 8.7 42 158 41 8.5 2.0 4.3 0.42 D-3 D-6 0-8 D-14 D-16 D-18 D-26 D-35 D-37 1-2 8.6 39 156 45 6.2 3.4 0.37 1.8 1-3 8.9 42 163 43 7.6 4.0 0.38 1.9 1-4 8.7 41 173 44 7.5 3.8 0.46 2.0 Si02 50.85 51.89 48.10 50.89 47.67 50.74 50.71 47.90 50.36 1-5 8.3 41 193 45 6.3 3.3 0.38 1.9 TiO; 1.54 2.16 1.53 2.23 0.79 1.48 1.58 1.55 1.90 1-7 8.4 42 181 43 6.7 3.7 0.40 1.8 Al 2O3 14.93 13.66 15.78 13.39 17.57 15.34 14.53 15.62 13.37 1-8 8.2 39 187 43 6.0 3.4 0.40 1.8 MgO 6.12 4.33 7.17 4.41 9.12 6.06 5.46 6.74 4.59 1-9 8.2 39 196 45 5.7 3.1 0.37 1.8 FeiOs* 11.94 15.20 12.04 15.90 9.46 11.92 13.03 11.90 16.87 I-10A 8.4 41 186 44 7.1 3.7 0.41 1.9 MnO 0.22 0.25 0.19 0.25 0.15 0.19 0.30 0.19 0.24 r-ios 8.7 42 188 45 7.1 3.8 0.42 1.9 CaO 10.72 8.92 10.89 9.05 12.57 10.60 9.80 10.46 8.08 i-n 8.2 46 116 39 8.1 3.8 0.47 2.08 2 0 0.8 2.1 Na20 2.96 3.05 2.67 2.98 2.02 2.79 2.87 2.84 2.92 K20 0.66 0.86 0.48 0.85 0.15 0.65 0.78 0.48 0.72 Note: Relative errors: 1 a = 1 percent Na; 3 percent Fe, Sc, Cr, Co, La, Sm, Lu, P20< 0.24 0.38 0.22 0.35 0.06 0.20 0.23 0.24 0.33 Hf; 5 percent Th.
Load more

Recommended publications
  • The Origin of the Columbia River Flood Basalt Province: Plume Versus Nonplume Models
    The Origin of the Columbia River Flood Basalt Province: Plume versus Nonplume Models Peter R. Hooper1, Victor E. Camp2, Stephen P. Reidel3 and Martin E. Ross4 1 Dept of Geology, Washington State University, Pullman, WA 99164 and Open University, Milton Keynes, MK7 6AA, U.K. 2 Dept of Geological Sciences, San Diego State University, San Diego, CA 92182 3 Washington State University Tri-Cities, Richland, Washington 99352 4 Dept of Earth and Environmental Sciences, Northeastern University, 360 Huntington Av., Boston, MA 02115 ABSTRACT As a contribution to the plume-nonplume debate we review the tectonic setting in which huge volumes of monotonous tholeiite of the Columbia River flood basalt province of the Pacific Northwest, USA, were erupted. We record the time-scale and the locations of these eruptions, estimates of individual eruption volumes, and discuss the mechanisms of sheet- flow emplacement, all of which bear on the ultimate origin of the province. An exceptionally large chemical and isotopic data base is used to identify the various mantle sources of the basalt and their subsequent evolution in large lower crustal magma chambers. We conclude by discussing the available data in light of the various deep mantle plume and shallow mantle models recently advocated for the origin of this flood basalt province and we argue that the mantle plume model best explains such an exceptionally large volume of tholeiitic basalt erupted over an unusually short period and within such a restricted area. 1 INTRODUCTION Advocates of mantle plumes have long considered continental flood basalt provinces to be one of the most obvious expressions of plume activity (Campbell and Griffiths, 1990; Richards et al., 1989).
    [Show full text]
  • Regional Dike Swarm Emplacement of Silicic Arc Magma in the Peninsular Ranges Batholith
    REGIONAL DIKE SWARM EMPLACEMENT OF SILICIC ARC MAGMA IN THE PENINSULAR RANGES BATHOLITH: THE SAN MARCOS DIKE SWARM (SMDS) OF NORTHERN BAJA CALIFORNIA Phil FARQUHARSON (presenter), David L. KIMBROUGH, and R. Gordon GASTIL, Department of Geological Sciences, San Diego State University Rancho San Marcos A densely intruded, northwest-striking, predominantly silicic regional dike The SMDS occurs entirely within the western province of the PRB, which is charac- swarm is exposed over an approximately 100 km-long segment in the terized by gabbro-tonalite-granodiorite plutons with primitive island arc geochemical west-central portion of the Cretaceous Peninsular Ranges batholith (PRB) affinities (DePaolo, 1981; Silver & Chappell, 1988; Todd et al., 1988, 1994), and in northern Baja California. Dike compositions range from basalt to rhyo- Rancho El Campito U/Pb zircon ages of 120-100 Ma. The extent of the swarm is shown schematically lite and are locally strongly bimodal. The swarm is intruded into two main N on the Gastil et al. (1975) 1:250 000 map of Baja California. units; 1) Triassic-Jurassic (?) turbidite flysch and 2) older, presumably pre- The swarm is intruded into two main units; 1) Triassic-Jurassic(?) turbidite flysch of 120 Ma batholithic rocks. Cross-cutting field relationships and a prelimi- the Rancho Vallecitos Formation (Reed, 1993) that is correlated to Julian Schist and nary U-Pb zircon age of 120±1 Ma clearly establish the swarm as an inte- Middle Jurassic Bedford Canyon Formation north of the border, and 2) older, pre- gral feature in the magmatic evolution of the PRB. Surprisingly, despite Agua Blanca Fault sumably pre-120 Ma batholithic rocks for which little data is currently available.
    [Show full text]
  • Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington
    Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington Scientific Investigations Report 2017–5022–N U.S. Department of the Interior U.S. Geological Survey Cover. Palouse Falls, Washington. The Palouse River originates in Idaho and flows westward before it enters the Snake River near Lyons Ferry, Washington. About 10 kilometers north of this confluence, the river has eroded through the Wanapum Basalt and upper portion of the Grande Ronde Basalt to produce Palouse Falls, where the river drops 60 meters (198 feet) into the plunge pool below. The river’s course was created during the cataclysmic Missoula floods of the Pleistocene as ice dams along the Clark Fork River in Idaho periodically broke and reformed. These events released water from Glacial Lake Missoula, with the resulting floods into Washington creating the Channeled Scablands and Glacial Lake Lewis. Palouse Falls was created by headward erosion of these floodwaters as they spilled over the basalt into the Snake River. After the last of the floodwaters receded, the Palouse River began to follow the scabland channel it resides in today. Photograph by Stephen P. Reidel. Field-Trip Guide to the Vents, Dikes, Stratigraphy, and Structure of the Columbia River Basalt Group, Eastern Oregon and Southeastern Washington By Victor E. Camp, Stephen P. Reidel, Martin E. Ross, Richard J. Brown, and Stephen Self Scientific Investigations Report 2017–5022–N U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S.
    [Show full text]
  • Giant Radiating Mafic Dyke Swarm of the Emeishan Large Igneous Province: Identifying the Mantle Plume Centre
    doi: 10.1111/ter.12154 Giant radiating mafic dyke swarm of the Emeishan Large Igneous Province: Identifying the mantle plume centre Hongbo Li,1,2 Zhaochong Zhang,1 Richard Ernst,3,4 Linsu L€u,2 M. Santosh,1 Dongyang Zhang1 and Zhiguo Cheng1 1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China; 2Geologi- cal Museum of China, Beijing 100034, China; 3Department of Earth Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada; 4Ernst Geosciences, 43 Margrave Avenue, Ottawa, ON K1T 3Y2, Canada ABSTRACT In many continental large igneous provinces, giant radiating and recognized six dyke sub-swarms, forming an overall dyke swarms are typically interpreted to result from the arri- radiating dyke swarm and converging in the Yongren area, val of a mantle plume at the base of the lithosphere. Mafic Yunnan province. This location coincides with the maximum dyke swarms in the Emeishan large igneous province (ELIP) pre-eruptive domal uplift, and is close to the locations of have not received much attention prior to this study. We high-temperature picrites. Our study suggests that the Yon- show that the geochemical characteristics and geochronologi- gren area may represent the mantle plume centre during the cal data of the mafic dykes are broadly similar to those of peak of Emeishan magmatism. the spatially associated lavas, suggesting they were derived from a common parental magma. Based on the regional geo- Terra Nova, 27, 247–257, 2015 logical data and our field observations, we mapped the spa- tial distribution patterns of mafic dyke swarms in the ELIP, ridge by a continent (Gower and swarms and their distributions pro- Introduction Krogh, 2002), edge-driven enhanced vide an opportunity to further test Large igneous provinces (LIPs) are mantle convection (King and Ander- the plume model for the ELIP.
    [Show full text]
  • Instability of the Southern Canadian Shield During the Late Proterozoic 2 3 Kalin T
    1 Instability of the southern Canadian Shield during the late Proterozoic 2 3 Kalin T. McDannella,b*, Peter K. Zeitlera, and David A. Schneiderc 4 5 aDepartment of Earth and Environmental Sciences, Lehigh University, 1 W. Packer Ave. Bethlehem PA, 18015 USA 6 7 bGeological Survey of Canada, Natural Resources Canada, 3303 – 33 St NW Calgary AB, T2L 2A7 Canada 8 9 cDepartment of Earth & Environmental Sciences, University of Ottawa, 25 Templeton Ave., Ottawa ON, K1N 6N5 10 Canada 11 12 *corresponding author: [email protected]; [email protected] 13 14 ABSTRACT 15 Cratons are generally considered to comprise lithosphere that has remained tectonically 16 quiescent for billions of years. Direct evidence for stability is mainly founded in the Phanerozoic 17 sedimentary record and low-temperature thermochronology, but for extensive parts of Canada, 18 earlier stability has been inferred due to the lack of an extensive rock record in both time and 19 space. We used 40Ar/39Ar multi-diffusion domain (MDD) analysis of K-feldspar to constrain 20 cratonic thermal histories across an intermediate (~150-350°C) temperature range in an attempt 21 to link published high-temperature geochronology that resolves the timing of orogenesis and 22 metamorphism with lower-temperature data suited for upper-crustal burial and unroofing 23 histories. This work is focused on understanding the transition from Archean-Paleoproterozoic 24 crustal growth to later intervals of stability, and how uninterrupted that record is throughout 25 Earth’s Proterozoic “Middle Age.” Intermediate-temperature thermal histories of cratonic rocks 26 at well-constrained localities within the southern Canadian Shield of North America challenge 27 the stability worldview because our data indicate that these rocks were at elevated temperatures 28 in the Proterozoic.
    [Show full text]
  • U.S. DEPARTMENT of the INTERIOR U.S.GEOLOGICAL SURVEY ALK.BIB a Selected Bibliography of Alkaline Igneous Rocks and Related Mine
    U.S. DEPARTMENT OF THE INTERIOR U.S.GEOLOGICAL SURVEY ALK.BIB A selected bibliography of alkaline igneous rocks and related mineral deposits, with an emphasis on western North America compiled by Felix E. Mutschler, D. Chad Johnson, and Thomas C. Mooney Open-File Report 94-624 1994 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. INTRODUCTION This bibliography contains 3,406 references on alkaline igneous rocks and related mineral deposits compiled in conjunction with ongoing studies of alkaline igneous rocks, metallogeny, and tectonics in western North America. Much of the literature on these topics is not readily recovered by searches of current bibliographies and computerized reference systems. We hope that by making this bibliography available, it will help other workers to access this occasionally hard to find literature. The bibliography is available in two formats: (1) paper hardcopy and (2) Apple Macintosh computer-readable 3.5 inch double density diskette. The computer-readable version of the bibliography is a 725 KB WORD (version 5.0) document. Individual literature citations are arranged alphabetically by author(s) and the order of items in each citation follows the standard U.S. Geological Survey format. Version 3.4 1 February 1994 BIBLIOGRAPHY Abbott, J. G., Gordey, S. P., and Tempelman-Kluit, D. J., 1986, Setting of stratiform, sediment- hosted lead-zinc deposits in Yukon and northeastern British Columbia, in Morin, J.
    [Show full text]
  • Flow Fabric Determination of Two Mesoproterozoic Midcontinent Rift Dike Swarms, Northeastern Minnesota
    FLOW FABRIC DETERMINATION OF TWO MESOPROTEROZOIC MIDCONTINENT RIFT DIKE SWARMS, NORTHEASTERN MINNESOTA A thesis submitted to the Kent State University Graduate College in partial fulfillment of the requirements for the degree of Master of Science by Elizabeth May Fein May, 2009 Thesis written by Elizabeth May Fein B.A., Oberlin College, 2003 M.S., Kent State University, 2009 Approved by ___________________________________, Advisor Daniel Holm ___________________________________, Chair, Department of Geology Daniel Holm ___________________________________, Dean, College of Arts and Sciences Timothy Moerland ii DEPARTMENT OF GEOLOGY THESIS APPROVAL FORM This thesis, entitled Flow fabric determination of two Mesoproterozoic midcontinent rift dike swarms, northeastern Minnesota has been submitted by Elizabeth Fein in partial fulfillment of the requirements for the Master of Science in Geology. The undersigned member’s of the student’s thesis committee have read this thesis and indicated their approval or disapproval of the same. Approval Date Disapproval Date _______________________________ _______________________________ Daniel Holm Daniel Holm _______________________________ _______________________________ Donald Palmer Donald Palmer _______________________________ _______________________________ David Schneider David Schneider iii Table of Contents List of Figures…………………………………………………………………………....v List of Tables…………………………………………………………………………….vi Acknowledgements…………………………………………………………………….vii Abstract ………………………………………………………………………………….1 1. Introduction
    [Show full text]
  • Ignimbrite Calderas, Regional Dike Swarms, and the Transition from Arc to Rift in the Southern Rocky Mountains
    Research Paper GEOSPHERE Magmato-tectonic links: Ignimbrite calderas, regional dike swarms, and the transition from arc to rift in the Southern Rocky Mountains 1, 2, GEOSPHERE, v. 15, no. 6 Peter W. Lipman * and Matthew J. Zimmerer * 1U.S. Geological Survey, Menlo Park, California 94025, USA 2New Mexico Bureau of Geology and Mineral Resources, Socorro, New Mexico 87801, USA https://doi.org/10.1130/GES02068.1 18 figures; 3 tables; 1 set of supplemental files ABSTRACT active for at least an additional 9 m.y. Platoro magmatism began to decline at ca. 26 Ma, concurrent with initial basaltic volcanism and regional extension CORRESPONDENCE: [email protected] Radial and linear dike swarms in the eroded roots of volcanoes and along along the Rio Grande rift, but no basalt is known to have erupted proximal rift zones are sensitive structural indicators of conduit and eruption geometry to Platoro caldera prior to ca. 20 Ma, just as silicic activity terminated at this CITATION: Lipman, P.W., and Zimmerer, M.J., 2019, Magmato-tectonic links: Ignimbrite calderas, regional that can record regional paleostress orientations. Compositionally diverse magmatic locus. The large numbers and lengths of the radial andesitic-dacitic dike swarms, and the transition from arc to rift in the dikes and larger intrusions that radiate westward from the polycyclic Platoro dikes, in comparison to the absence of similar features at other calderas of the Southern Rocky Mountains: Geosphere, v. 15, no. 6, caldera complex in the Southern Rocky Mountain volcanic field (southwest- San Juan volcanic locus, may reflect location of the Platoro system peripheral p.
    [Show full text]
  • Paleomagnetism Geochronology Geochemistry Proterozoic Mafic Dike
    ISBN 0-7794-8963-2 THESE TERMS GOVERN YOUR USE OF THIS DOCUMENT Your use of this Ontario Geological Survey document (the “Content”) is governed by the terms set out on this page (“Terms of Use”). By downloading this Content, you (the “User”) have accepted, and have agreed to be bound by, the Terms of Use. Content: This Content is offered by the Province of Ontario’s Ministry of Northern Development and Mines (MNDM) as a public service, on an “as-is” basis. Recommendations and statements of opinion expressed in the Content are those of the author or authors and are not to be construed as statement of government policy. You are solely responsible for your use of the Content. You should not rely on the Content for legal advice nor as authoritative in your particular circumstances. Users should verify the accuracy and applicability of any Content before acting on it. MNDM does not guarantee, or make any warranty express or implied, that the Content is current, accurate, complete or reliable. MNDM is not responsible for any damage however caused, which results, directly or indirectly, from your use of the Content. MNDM assumes no legal liability or responsibility for the Content whatsoever. Links to Other Web Sites: This Content may contain links, to Web sites that are not operated by MNDM. Linked Web sites may not be available in French. MNDM neither endorses nor assumes any responsibility for the safety, accuracy or availability of linked Web sites or the information contained on them. The linked Web sites, their operation and content are the responsibility of the person or entity for which they were created or maintained (the “Owner”).
    [Show full text]
  • Reshuffling the Columbia River Basalt Chronology—Picture Gorge Basalt, the Earliest- and Longest-Erupting Formation Emily B
    https://doi.org/10.1130/G47122.1 Manuscript received 17 April 2019 Revised manuscript received 3 December 2019 Manuscript accepted 5 December 2019 © 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Reshuffling the Columbia River Basalt chronology—Picture Gorge Basalt, the earliest- and longest-erupting formation Emily B. Cahoon1*, Martin J. Streck1*, Anthony A.P. Koppers2 and Daniel P. Miggins2 1 Department of Geology, Portland State University, P.O. Box 751, Portland, Oregon 97207-0751, USA 2 College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331-5503, USA ABSTRACT divided into formations based on geographic The Columbia River Basalt Group (CRBG) is the world’s youngest continental flood basalt location of vents, geochemistry, and timing of province, presumably sourced from the deep-seated plume that currently resides underneath eruptions (Camp and Ross, 2004) and include Yellowstone National Park in the northwestern United States. The earliest-erupted basalts Steens, Imnaha, Grande Ronde, and Picture from this province aid in understanding and modeling plume impingement and the subsequent Gorge Basalts (e.g., Reidel et al., 2013). While evolution of basaltic volcanism. We explore the Picture Gorge Basalt (PGB) formation of the several models have been proposed for CRBG CRBG, and discuss the location and geochemical significance in a temporal context of early magmatism, many researchers support that the CRBG magmatism. We report new ARGUS-VI multicollector 40Ar/39Ar incremental heating flood basalts are sourced from the Yellowstone ages from known PGB localities and additional outcrops that we can geochemically classify mantle plume (e.g., Geist and Richards, 1993; as PGB.
    [Show full text]
  • Westward Migrating Ignimbrite Calderas and a Large Radiating Mafic Dike Swarm of Oligocene Age, Central Rio Grande Rift, New
    http://geoinfo.nmt.edu/staff/chamberlin/mrds/Chamberlin_2002_GSA_poster.pdf WESTWARD MIGRATING IGNIMBRITE CALDERAS AND A LARGE RADIATING MAFIC DIKE SWARM OF OLIGOCENE AGE, CENTRAL RIO GRANDE RIFT, NEW MEXICO: SURFACE EXPRESSION OF AN UPPER MANTLE DIAPIR? CHAMBERLIN, Richard M., CHAPIN, Charles E., and McINTOSH, William C., New Mexico Bureau of Geology and Mineral Resources, New Mexico Tech, Socorro NM 87801, [email protected] ABSTRACT: (Chamberlin et al., 2002) A cluster of five large overlapping ignimbrite calderas is moderately well exposed in strongly extended tilted fault-block mountain ranges of the central Rio Grande rift, southwest of Socorro NM. The Socorro-Magdalena caldera cluster (SMCC) is 85 km long and 20-25 km wide. It parallels the southeastern flank of the Colorado Plateau and the WSW-trending San Agustin arm of the rift. Precise 40Ar/ 39Ar ages of sanidines from the rhyolite ignimbrites demonstrate that the distended calderas become progressively younger to the west-southwest. Large volume ignimbrite eruptions occurred at 31.9, 28.7, 27.9, 27.4 and 24.3 Ma. A large satellitic caldera, formed at 28.4 Ma, is located 20 km south of the main overlapping trend. Moderately alkaline to sub-alkaline basaltic andesite and basalt dikes of Oligocene age (31-24 Ma, K-Ar, 40Ar/ 39Ar in progress) form a large semi-continuous radial array that is broadly focused on the SMCC. The Magdalena radial dike swarm (MRDS) fans through 220° of arc from Pie Town clockwise to Acoma, Chupadera, Bingham and Elephant Butte. The maximum radius of the MRDS is 125 km; subswarms of near parallel dikes are commonly 20-75 km long.
    [Show full text]
  • Mill Creek Diabase Dike Swarm, Eastern Arbuckles: a Glimpse of Cambrian Rifting in the Southern Oklahoma Aulacogen
    Cambrian (?) Mill Creek diabase dike swarm, eastern Arbuckles: A Glimpse of Cambrian rifting in the Southern Oklahoma Aulacogen Edward G. Lidiak1, Rodger E. Denison2, and Robert J. Stern3 1Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260. [email protected]. Corresponding author. 215141 Kingstree Drive, Dallas, Texas 75248. [email protected]. 3Department of Geosciences, The University of Texas at Dallas, Box 830688, Richardson, Texas 75083-0688. rjstern@ utdallas.edu. ABSTRACT INTRODUCTION A swarm of Cambrian (?) diabase dikes intrude The Southern Oklahoma Aulacogen (SOA) is a well- the 1390-1365 Ma granitoids of the eastern Arbuck- known transverse structure that trends west-northwest in le Mountains of Oklahoma. The dikes strike predom- the southern North American craton. Exposures within the inantly N60°W parallel to the rifted margin of the SOA reveal faults that record extension and which may Southern Oklahoma Aulacogen and are interpreted as be interpreted as related to its formation. Mesoproterozo- being related to Cambrian opening of that structure. ic basement underlies much of the region and ~1390 Ma The dikes, referred to here as the Mill Creek diabas- gneiss and granodiorite and ~1365 Ma granite are exposed es, are olivine-normative to quartz-normative tholeiitic in the eastern Arbuckle Mountains (Figures 1, 2). Diabase basalts. Their tholeiitic character is further indicated dikes are widespread throughout the core of the eastern Ar- T by high Fe2O3 (total Fe), moderate to high TiO2, low buckles. These dikes are referred to here as the Mill Creek P O , and low Nb/Y ratio. Mg numbers (Mg#) of 52-36 2 5 diabase dike swarm for excellent exposures in Mill Creek are indicative of derivative basaltic liquids which are Quarry (Figures 2, 3), which is here designated as the type consistent with the fine-grained, equigranular mineral locality.
    [Show full text]