DOCSLIB.ORG

Microlite Orientation in Obsidian Flow Measured by Synchrotron X-Ray Diffraction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Microlite Orientation in Obsidian Flow Measured by Synchrotron X-Ray Diffraction Contributions to Mineralogy and Petrology _#####################_ https://doi.org/10.1007/s00410-018-1479-9 Revised Proof ORIGINAL PAPER Microlite orientation in obsidian flow measured by synchrotron X-ray diffraction Michael Manga1 · Marco Voltolini2 · Hans‑Rudolf Wenk1 Received: 16 April 2018 / Accepted: 31 May 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Clinopyroxene and plagioclase (andesine) microlites in an obsidian flow from Glass Mountain (NE California, USA) display strong alignment. Synchrotron X-ray diffraction, coupled with Rietveld analysis, was used to quantify crystallographic- preferred orientation (CPO). Clinopyroxene, with a rod-shaped morphology, shows a strong alignment of [001] in the flow direction and (010) aligned parallel to the inferred flow plane. Andesine, with a platy morphology, displays an alignment of (010) platelets in the flow plane. Some pole densities exceed 90 multiples of random distribution. Applying a model of rigid ellipsoidal inclusions in a viscous matrix, the local pure shear strains are between 2 and 3. Keywords Obsidian · Microlite alignment · Texture analysis · Crystal-preferred orientation, Strain estimates Introduction (e.g., Manga 1998; Castro et al. 2004). Because microlites are small, however, it is not usually possible to determine Obsidian in natural lava flows preserves a number of tex- crystallographic orientation, and microlites with diameters tural features that record its eruption and emplacement (e.g., smaller than about 1 µm cannot be characterized. Here, we Smith 2002). Structural features range from folds and layer- use synchrotron X-ray diffraction and scanning electron ing at centimeter-to-decameter scales (Fink 1983; Manley microscopy to investigate two rhyolitic obsidian samples and Fink 1987; Castro and Cashman 1999), to deformed from the Glass Mountain lava flow, Medicine Lake Volcano, bubbles at the micrometer-to-millimeter scale (e.g., Rust Northern California. et al. 2003; Gardner et al. 2017) and aligned elongated Synchrotron hard X-ray diffraction proved to be a very micrometer-sized crystallites at the smallest scales (Manga useful method for texture analysis in a broad range of differ- 1998; Castro et al. 2002). Together, these textures provide ent materials from metals (e.g., Wu et al. 2010) to complex information about flow, fragmentation, and solidification clays (e.g., Wenk et al. 2010), slates (e.g., Haerinck et al. processes. 2015), and serpentinite (e.g., Soda and Wenk 2014). This Microlites are oriented by flow, and their orientation dis- is a first application of the method to volcanic rocks. Con- tribution thus offers an opportunity to determine the type of trary to optical microscopy referred to above that describes flow and strain experienced by the melt prior to quenching the shape-preferred orientation (SPO) of particles, X-ray (e.g., Castro et al. 2002; Befus et al. 2014, 2015). Quanti- texture analysis provides a quantitative description of the tative information, including the relationship between size crystallographic orientation distribution of clinopyroxene and orientation, can be obtained with optical microscopy and plagioclase, averaging over crystallite volumes, not over crystallite numbers. The analysis is by no means trivial in the case of obsidian, since crystallites contribute less than Communicated by Timothy L. Grove. 2% of the volume and diffraction from those crystals is weak * Hans-Rudolf Wenk compared to scattering from the amorphous glass. Never- [email protected] theless, results for SPO and CPO are comparable and can be used to estimate local strain patterns based on Jeffery’s 1 Department of Earth and Planetary Science, University (1922) solution for the motion of rigid ellipsoidal inclusions of California, Berkeley, CA 94720, USA in a viscous matrix. 2 Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Vol.:(0123456789)1 3 _####_ Page 2 of 12 Contributions to Mineralogy and Petrology _#####################_ Revised Proof Experimental Sample 2 was also analyzed with a JEOL SEM at the Engineering Department of the University of Trento, Italy, Samples to identify the phases and determine their morphology. Back-scattered images, again parallel and perpendicular The two samples investigated are obsid- to the flow direction, are shown in Fig. 3. Pyroxenes are ian fragments from Glass Mountain, CA, USA easily recognized, with high contrast. They are prismatic (41°36′15.5″N/121°28′34.5″W). This ~ 1 km3 compo- needles with a pseudohexagonal cross section, roughly sitionally zoned flow erupted about 1070 AD and is the 2–10 µm long and 0.1–2 µm in diameter. Contrast for pla- youngest eruption at the Medicine Lake shield volcano gioclase is weak because of a similar chemical compo- (Grove et al. 1997, Donnelly-Nolan et al. 2016). Optical sition as the glass matrix. Some crystals are marked in microscopy reveals a layered structure with layers 2–5 mm Fig. 3. They are larger than pyroxenes and have a platelet in thickness (Fig. 1a). Some layers are more uniform than morphology (see also Fig. 2). They range in size from 2 others. At higher magnification, a strong alignment of to 25 µm long to 2–5 µm wide. The chemical composi- needle-shaped microlites is apparent (Fig. 1b). Locally, tions of the phases were analyzed with an EDAX EDS there is distorted flow around larger inclusions of magnet- system (Fig. 4; Table 1). The pyroxene is identified as fer- ite (Fig. 1c) and fragments of plagioclase (Fig. 1d). rous intermediate augite/pigeonite (Ca0.18, Mg0.43, Fe0.36, In this study, we focus on homogeneous layers in two Na0.03) SiO3, plagioclase as calcic andesine (Ca0.40 Na0.52 samples. In sample 1, microlites are almost exclusively K0.08)(Si0.72, Al0.28)O8, and glass as high in SiO2 (> 70%) clinopyroxene (Fig. 1b). Sample 2 is a mixture of pla- with significant aluminum, potassium, and sodium. gioclase and clinopyroxene microlites. Views of sample 2 with plane polarizers (Fig. 2a, c) and crossed polarizers Hard X‑ray synchrotron diffraction (Fig. 2b, d), both parallel to the flow direction (Fig. 2a, b) and perpendicular to the flow direction (Fig. 2c, d), show Samples for the X-ray diffraction experiment were ~ 0.7 mm- the morphology and the strong alignment of microlites. thick slabs with the flow plane perpendicular to the slab Clinopyroxenes are needles aligned in the flow direction surface. The diffraction measurements were carried out at and plagioclase microlites are platelets aligned in the flow beamline 11-ID-C at the Advanced Photon Source (APS) of plane. Plagioclase platelets are typically larger in size than Argonne National Laboratory. Experiments were performed clinopyroxene needles which is most obvious with crossed in transmission geometry. A beam of X-rays (λ = 0.10738 Å), polarizers. 0.5 mm in diameter, irradiates the sample, and diffraction patterns were recorded by a Mar345 image plate detector Fig. 1 Optical micrographs of obsidian in sample O1. Plane polarized light. a Structure with compositional layering (Os2a), b detail of layering with microlites, c microlites around an inclusion of magnetite, and d inclusion of plagioclase. In c, the curves show streamlines for pure shear around a spherical and rigid inclusion 1 3 Contributions to Mineralogy and Petrology _#####################_ Page 3 of 12 _####_ Revised Proof Fig. 2 Optical micrographs of obsidian in sample O2, a, b parallel to the flow direction and c, d perpendicular to the flow direction;a, c are plane polarized light and b, d crossed polarizers. Microlites are andes- ine (And) and clinopyroxene needles (lines in a and dots in c). In the upper right corner of a and c, an enlarged segment is displayed (3450 × 3450 pixels) placed about 2 m behind the sample. First, instrumental parameters such as sample detector Exposure time was 900 s. High energy maximizes sample distance, detector orientation, and Caglioti parameters defin- penetration. The beam size was chosen to give a sufficiently ing the diffraction resolution were refined from diffraction 3 large sample volume (~ 0.2 mm ) to be representative of a data collected for a CeO 2 standard. These instrument param- single flow layer. The diffraction images display Debye rings eters were then applied to each of the four obsidian sample that have intensity variations as a function of the azimuth data sets. because of preferred orientation of crystallites (Fig. 5). A The Rietveld refinement requires as input the crystallo- dark broad ring is due to scattering from glass and sharp graphic characterization of the composing phases. For clino- rings are scattering from crystallites. pyroxene, the C2/c structure was used (Clark et al. 1969, # The sample slab was mounted on a goniometer and was 1000035). For the texture analysis of monoclinic crystals in rotated around a horizontal axis perpendicular to the flow MAUD, the first setting (z monoclinic axis) has to be applied plane and the incident X-ray beam. The sample was tilted in (Matthies and Wenk 2009), but results are shown in the more 15° increments to seven positions (− 45°, − 30°, − 15°, 0°, conventional second setting (y monoclinic axis). For plagio- 15°, 30°, and 45°) to obtain a good coverage of orientation clase andesine, I 1 was used which had to be converted to P 1 space for texture analysis. This results in seven diffraction (Fitzgerald et al. 1986, #9001030). The glass phase, giving images for each data set. The flow layers are perpendicular to rise to the diffuse diffraction peaks at Q ~ 1.6 and 4.3 Å−1 the tilt axis to avoid overlapping of layers at high tilt angles. (Q = 2π/d), is more difficult to describe. For some refine- For both samples, diffraction images were recorded for two ments, a nanocrystalline form of tetragonal α (low) cristo- layers (O11, O12, O22, and O25). balite (Hosemann et al. 1991, spacegroup P4 1212) was used, which was first applied to silica glass by Le Bail (1995) and Rietveld analysis later by Lutterotti et al.
Load more

Recommended publications
  • Degassing and Microlite Crystallization During Pre-Climactic Events of the 1991 Eruption of Mt. Pinatubo, Philippines
    Bull Volcanol (1999) 60:355–380 Q Springer-Verlag 1999 ORIGINAL PAPER J. E. Hammer 7 K. V. Cashman 7 R. P. Hoblitt S. Newman Degassing and microlite crystallization during pre-climactic events of the 1991 eruption of Mt. Pinatubo, Philippines Received: 4 December 1997 / Accepted: 13 September 1998 Abstract Dacite tephras produced by the 1991 pre-cli- determine rates of crystal nucleation and growth using mactic eruptive sequence at Mt. Pinatubo display ex- repose interval as the time available for crystallization. treme heterogeneity in vesicularity, ranging in clast Shape and size analysis suggests that crystallization density from 700 to 2580 kg m–3. Observations of the 13 proceeded in response to lessening degrees of feldspar surge-producing blasts that preceded the climactic plin- supersaturation as repose interval durations increased. ian event include radar-defined estimates of column We thus propose that during repose intervals, a plug of heights and seismically defined eruptive and intra-erup- highly viscous magma formed due to the collapse of ve- tive durations. A comparison of the characteristics of sicular magma that had exsolved volatiles during the erupted material, including microlite textures, chemical previous explosive event. If plug thickness grew pro- compositions, and H2O contents, with eruptive parame- portionally to the square root of time, and if magma ters suggests that devolatilization-induced crystalliza- pressurization increased during the eruptive sequence, tion of the magma occurred to a varying extent prior to the frequency of eruptive pulses may have been modu- at least nine of the explosive events. Although volatile lated by degassing of magma within the conduit.
    [Show full text]
  • Geochemistry of Sideromelane and Felsic Glass Shards in Pleistocene Ash Layers at Sites 953, 954, and 9561
    Weaver, P.P.E., Schmincke, H.-U., Firth, J.V., and Duffield, W. (Eds.), 1998 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 157 25. GEOCHEMISTRY OF SIDEROMELANE AND FELSIC GLASS SHARDS IN PLEISTOCENE ASH LAYERS AT SITES 953, 954, AND 9561 Andrey A. Gurenko2 and Hans-Ulrich Schmincke2 ABSTRACT Sideromelane and felsic glass shards from unconsolidated Pleistocene volcaniclastic sediments drilled at Sites 953, 954, and 956 are thought to have derived from submarine and subaerial volcanic eruptions on Gran Canaria (Sites 953 and 954) and Tenerife (Sites 954 and 956). We analyzed these glasses by electron microprobe for major elements and sulfur, chlorine, and fluorine. Sideromelane glasses represent a spectrum from alkali basalt through basanite, hawaiite, mugearite, and tephrite to nephelinite. Felsic glasses have compositions similar to benmoreite, trachyte, and phonolite. Vesiculated mafic and felsic glass shards, which are characterized by low S and Cl concentrations (0.01−0.06 wt% S and 0.01–0.04 wt% Cl), are interpreted to have formed by pyroclastic activity on land or in shallow water and appeared to have been strongly degassed. Vesicle-free blocky glass shards having 0.05−0.13 wt% S are likely to have resulted from submarine eruptions at moderate water depths and represent undegassed or slightly degassed magmas. Cl concentrations range from 0.01 to 0.33 wt% and increase with increasing MgO, suggesting that Cl behaves as an incompatible element during magma crystallization. Concentrations of fluorine (0.04− 0.34 wt% F) are likely to represent undegassed values, and the variations in F/K ratios between 0.02 and 0.24 are believed to reflect those of parental magmas and of the mantle source.
    [Show full text]
  • Magma Emplacement and Deformation in Rhyolitic Dykes: Insight Into Magmatic Outgassing
    MAGMA EMPLACEMENT AND DEFORMATION IN RHYOLITIC DYKES: INSIGHT INTO MAGMATIC OUTGASSING Presented for the degree of Ph.D. by Ellen Marie McGowan MGeol (The University of Leicester, 2011) Initial submission January 2016 Final submission September 2016 Lancaster Environment Centre, Lancaster University Declaration I, Ellen Marie McGowan, hereby declare that the content of this thesis is the result of my own work, and that no part of the work has been submitted in substantially the same form for the award of a higher degree elsewhere. This thesis is dedicated to Nan-Nar, who sadly passed away in 2015. Nan, you taught our family the importance and meaning of love, we love you. Abstract Exposed rhyolitic dykes at eroded volcanoes arguably provide in situ records of conduit processes during rhyolitic eruptions, thus bridging the gap between surface and sub-surface processes. This study involved micro- to macro-scale analysis of the textures and water content within shallow (emplacement depths <500 m) rhyolitic dykes at two Icelandic central volcanoes. It is demonstrated that dyke propagation commenced with the intrusion of gas- charged currents that were laden with particles, and that the distribution of intruded particles and degree of magmatic overpressure required for dyke propagation were governed by the country rock permeability and strength, with pre-existing fractures playing a pivotal governing role. During this stage of dyke evolution significant amounts of exsolved gas may have escaped. Furthermore, during later magma emplacement within the dyke interiors, particles that were intruded and deposited during the initial phase were sometimes preserved at the dyke margins, forming dyke- marginal external tuffisite veins, which would have been capable of facilitating persistent outgassing during dyke growth.
    [Show full text]
  • Pre-Eruptive Magma Mixing and Crystal Transfer Revealed By
    1 Pre-Eruptive Magma Mixing and Crystal Transfer Revealed by 2 Phenocryst and Microlite Compositions in Basaltic Andesite from the 3 2008 Eruption of Kasatochi Island Volcano – REVISION #2 4 5 Owen K. Neill1a, Jessica F. Larsen2, Pavel E. Izbekov2, Christopher J. Nye3 6 7 1Peter M. Hooper GeoAnalytical Laboratory, School of the Environment, Washington 8 State University, P.O. Box 642812, Pullman, WA 99164-2812 9 [email protected] 10 aCorresponding author. 11 12 2Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, 13 AK 99775 14 [email protected], [email protected] 15 16 3Alaska Volcano Observatory, State of Alaska, Division of Geological and Geophysical 17 Surveys, 3354 College Road, Fairbanks, AK 99709 18 [email protected] 19 20 21 ABSTRACT 22 The 7-8 August, 2008 eruption of Kasatochi Island volcano, located in the central 23 Aleutians Islands, Alaska, produced abundant, compositionally heterogeneous basaltic 24 andesite (52-55 wt% SiO2) that has been interpreted to result from pre-eruptive magma 25 mixing. The basaltic andesite contains two populations of plagioclase phenocrysts. The 26 first, volumetrically dominant population consists of oscillatory-zoned phenocrysts with 27 an overall normal zonation trend towards comparatively sodic rims (An55-65), interrupted 28 by dissolution features and spikes in calcium content (up to ~An85). The second 29 population consists of phenocrysts with highly calcic compositions (~An90). These 30 phenocrysts contain sharp decreases in calcium content close to their rims (reaching as 1 31 low as ~An60), but are otherwise texturally and compositionally homogeneous. 32 Groundmass plagioclase microlites are generally much more calcic than rims of the first 33 phenocryst population, with more than 50% of measured microlites containing >An80.
    [Show full text]
  • Textures, Water Content and Degassing of Silicic Andesites From
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by HAL-INSU Textures, water content and degassing of silicic andesites from recent plinian and dome-forming eruptions at Mount Pel´eevolcano (Martinique, Lesser Antilles arc) Caroline Martel, Jean-Louis Bourdier, Michel Pichavant, Herv´eTraineau To cite this version: Caroline Martel, Jean-Louis Bourdier, Michel Pichavant, Herv´eTraineau. Textures, water con- tent and degassing of silicic andesites from recent plinian and dome-forming eruptions at Mount Pel´eevolcano (Martinique, Lesser Antilles arc). Journal of Volcanology and Geothermal Re- search, Elsevier, 2000, 96, pp.191-206. <10.1016/S0377-0273(99)00147-X>. <hal-00115128> HAL Id: hal-00115128 https://hal-insu.archives-ouvertes.fr/hal-00115128 Submitted on 7 May 2013 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. Textures, water content and degassing of silicic andesites from recent plinian and dome-forming eruptions at Mount Pelée volcano (Martinique, Lesser Antilles arc) C Martela J.-L Bourdierb M Pichavanta
    [Show full text]
  • Submarine Growth of a Hawaiian Shield Volcano
    SUBMARINE GROWTH OF A HAWAIIAN SHIELD VOLCANO BASED ON VOLCANICLASTICS IN THE HAWAIIAN SCIENTIFIC DRILLING PROJECT 2 CORE A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN GEOLOGY & GEOPHYSICS DECEMBER 2004 By Kate Phillippa Bridges Thesis Committee: Michael O. Garcia, Chairperson Bruce Houghton Thor Thordarson ACKNOWLEDGEMENTS I would like to thank my teachers and colleagues at the University of Hawai'i at Manoa Geology and Geophysics department for their inspiration and encouragement. In particular, I would like to thank Mike Garcia for giving me the opportunity to pursue and complete a Master's degree in volcanology at the University of Hawai'i. In addition, I am very grateful for all the support he has given me throughout the past three years and his sense of humor. Mahalos also to Thor Thordarsen, who always had words of encouragement to accompany his insightful comments on the progress and outcome of this study. Thanks to Bruce Houghton for sound scientific advise and guidance. Finally, muchos mahalos to all my friends for making the journey to Masterhood fun and, of course, to my folks! iii Acknowledgements iii List of figures vii List of tables viii Abstract ix 1. INTRODUCTION 1 1.1 Geological setting 2 1.2 Models for the growth of shield volcanoes 4 1.2.1 Magma supply and stages 4 1.2.2 Deposits 5 1.2.3 Subsidence and collapse ..7 1.3 Hawaiian Scientific Drilling Project 9 1.3.1 Introduction, 9 1.3.2 Basic stratigraphy of the HSDP2 core .11 1.3.3 Introduction to the HSDP2 volcaniclastics 14 1.4 Terminology 21 1.5 Subaqueous fragmentation of basaltic magma 23 1.5.1 Magmatic explosivity 23 1.5.2 Steam explosivity 24 Littoral magma:water interaction Subaqueous magma:water interaction 1.5.3 Passive quenching and autobrecciation of lava ~ 29 1.5.4 Secondary fragmentation of basaltic magma 29 2.
    [Show full text]
  • Smithsonian Contributions to the Earth Sciences • Number 12 Serial Publications of the Smithsonian Institution
    GRANT HEIKEN aSa-$T?-x-7-0087) AN ATLAS OFVOLCANIC N74-25882 ASH (Wasa) -5 p HC ~e CSCL 08P Unclas G3/13 40342 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES • NUMBER 12 SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION The emphasis upon publications as a means of uuiubing ln ,.w0 dg .... a ...... by the first Secretary of the Smithsonian Institution. In his formal plan for the Insti- tution, Joseph Henry articulated a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the Smithsonian imprint, com- mencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Annals of Flight Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Studies in History and Technology In these series, the Institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of profes- sional colleagues at other institutions of learning. These papers report newly acquired facts, synoptic interpretations of data, or original theory in specialized fields. These publications are distributed by mailing lists to libraries, laboratories, and other in- terested institutions and specialists throughout the world. Individual copies may be obtained from the Smithsonian Institution Press as long as stocks are available.
    [Show full text]
  • Chlorophaeite, Sideromelane, and Palagonite from the Columbia River
    360 rHE AMER]CAN MINERALOGIST CHLOROPHAEITE,SIDEROMELANE AND PALAGONITE FROM THE COLUMBIA RIVER PLATEAU Mlnrrx A. Ppecocr* AND Rrcn.qnt E. Fur,r-rn, Uni'aersityof Washington CONTENTS Suuu.q.nv INrnoouctroN Cnlonopue.nrrB Occurrence Hand-specimen Microstudy Chemical composition The identity of chlorophaeite and certain materials described as palagonite Definition SroBnouBt-.tNe Occurrence Hand-specimen Microstudy Chemical composition The nomenclature of basic glasses Further occurrencesof sideromelane P.g.raGor.rtrB Petrographic descriptions The use of the term palagonite RrrpnBNcBs Explem.qtrox or Prern XII SUMMARY The three mineraloids, chlorophaeite, sideromelane and pala- gonite are characteristic of Kainozoic basaltic fields. From a new analysis of chlorophaeite from Oregon and existing analyses of materials from Scotland and India the approximate formula: (Fe,Al)zOg.2(\4g,Fe,Ca)O'4SiOr+10H2Ois derived. It is urged that the definition of chlorophaeite be extended to cover all hydrous, amorphous, pitch-like materials of deuteric origin, some of which have been named palagonite, in basalts and dolerites. An argument is advanced supporting the continued use of t Commonwealth Fund Fellow, at Harvard University from the University of Glaseow. JOURNAL MINERALOGICAL SOCIETY OF AMERICA 361 sideromelane, as distinct from tachylyte, as a specific name for ideal basaltic glass formed under conditions of specially rapid cooling. ft is shown that a chemical and genetic distinction exists between chlorophaeite and palagonite; and that palagonite should properly be restricted to its original significance, namely a gel produced essentially in the hydration of sideromelane by water or water vapor of exotic origin. INTRODUCTION The terms chlorophaeite, sideromelaneand palagonite were all proposed before the petrographic microscope was in common use, and consequently the original descriptions of these materials lack the precision now desirable.
    [Show full text]
  • The Survival of Mafic Magmatic Enclaves and the Timing of Magma Recharge 2 Philipp Ruprecht1, Adam C
    Confidential manuscript submitted to Geophysical Research Letters 1 The Survival of Mafic Magmatic Enclaves and the Timing of Magma Recharge 2 Philipp Ruprecht1, Adam C. Simon2, and Adrian Fiege3 3 1Department of Geological Sciences and Engineering, University of Nevada, Reno, NV, USA. 4 2Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 5 USA. 6 3Department of Earth and Planetary Sciences, American Museum of Natural History, New York, 7 NY, USA. 8 Corresponding author: Philipp Ruprecht ([email protected]) 9 Key Points: 10 •! Common survival times for mafic enclaves in felsic volcanic systems are centuries to 11 millennia extending timescale records from minerals 12 •! Mafic enclaves record only syn-eruptive processes in hot magmatic systems 13 •! Mafic enclaves in plutonic systems may represent recharge histories of 10,000 to 100,000 14 years 15 Confidential manuscript submitted to Geophysical Research Letters 16 Abstract 17 Many intermediate to felsic intrusive and extrusive rocks contain mafic magmatic enclaves that 18 are evidence for magma recharge and mixing. Whether enclaves represent records of pro-longed 19 mixing or syn-eruptive recharge depends on their preservation potential in their intermediate to 20 felsic host magmas. We present a model for enclave consumption where an initial stage of 21 diffusive equilibration loosens the crystal framework in the enclave followed by advective 22 erosion and disaggregation of the loose crystal layer. Using experimental data to constrain the 23 propagation rate of the loosening front leads to enclave “erosion” rates of 10-5 to 10-8 cm/s for 24 subvolcanic magma systems. These rates suggest that under some circumstances, enclave records 25 are restricted to syn-eruptive processes, while in most cases enclave populations represent the 26 recharge history over centuries to millennia.
    [Show full text]
  • Geology of the Central and Northern Parts of the Western Cascade Range in Oregon
    Geology of the Central and Northern Parts of the Western Cascade Range in Oregon GEOLOGICAL SURVEY PROFESSIONAL PAPER 449 Prepared in cooperation with the State of Oregon, Departtnent of Geology and Mineral Industries Geology of the Central and Northern Parts of the Western Cascade Range in Oregon By DALLAS L. PECK, ALLAN B. GRIGGS, HERBERT G: SCHLICKER, FRANCIS G. WELLS, and HOLLIS M. DOLE ·~ GEOLOGICAL SURVEY PROFESSIONAL PAPER 449 Prepared in cooperation with the State of Oregon, Department of Geology and Mineral Industries ,... UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director . -~ The U.S. Geological Survey Library catalog card for this publication appears after page 56. For sale by the Superintendent of Documents,. U.S. Government Printing Office · · ·. Washington, D.C. 20402 CONTENTS Page Page Stratigraphy-Continued 1 Abstract------------------------------------------- Sardine Formation-Continued Introduction ______ --------------------------------- 2 Lithology and petrography-Continued Scope of investigation ______ - ___ - __ -------------- 2 Location, accessibility, and culture __ -------------- 2 Pyroclastic rocks __________ -- __ ---------'-- 33 Physical features ______ --_---_-_- ___ -----_------- 3 Age and correlation ____ - _--- __ -------------- 34 Climate and vegetation ___ --- ___ - ___ -----_------- 4 Troutdale Formation _____ ------------------------ 35 Fieldwork and reliability of the geologic
    [Show full text]
  • Pre-Eruptive Storage Conditions and Eruption Dynamics of a Small Rhyolite Dome: Douglas Knob, Yellowstone Volcanic Field, USA
    Bull Volcanol (2014) 76:808 DOI 10.1007/s00445-014-0808-8 RESEARCH ARTICLE Pre-eruptive storage conditions and eruption dynamics of a small rhyolite dome: Douglas Knob, Yellowstone volcanic field, USA Kenneth S. Befus & Robert W.Zinke & Jacob S. Jordan & Michael Manga & James E. Gardner Received: 14 May 2013 /Accepted: 5 February 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract The properties and processes that control the size, ranging from 0.03 to 0.11 MPa h−1 (∼0.4–1.3 mm s−1 ascent duration, and style of eruption of rhyolite magma are poorly rates). Such slow ascent would allow time for passive constrained because of a paucity of direct observations. Here, degassing at depth in the conduit, thus resulting in an effusive we investigate the small-volume, nonexplosive end-member. eruption. Using calculated melt viscosity, we infer that the In particular, we determine the pre-eruptive storage conditions dike that fed the eruption was 4–8 m in width. Magma flux and eruption dynamics of Douglas Knob, a 0.011-km3 obsid- through this dike, assuming fissure dimensions at the surface ian dome that erupted from a 500-m-long fissure in the represent its geometry at depth, implies an eruption duration Yellowstone volcanic system. To determine pre-eruptive stor- of 17–210 days. That duration is also consistent with the shape age conditions, we analyzed compositions of phenocrysts, of the dome if produced by gravitational spreading, as well as matrix glass, and quartz-hosted glass inclusions by electron the ascent time of magma from its storage depth.
    [Show full text]
  • Pre-Eruptive and Syn-Eruptive Conditions in the Black Butte, California Dacite: Insight Into Crystallization Kinetics in a Silicic Magma System
    Journal of Volcanology and Geothermal Research 160 (2007) 263–284 www.elsevier.com/locate/jvolgeores Pre-eruptive and syn-eruptive conditions in the Black Butte, California dacite: Insight into crystallization kinetics in a silicic magma system Molly C. McCanta a,⁎, Malcolm J. Rutherford a, Julia E. Hammer b a Department of Geological Sciences, Brown University, Box 1846, Providence, RI 02912, USA b Department of Geology and Geophysics, University of Hawaii, 1680 East–West Road, Honolulu, HI 96822, USA Received 7 April 2006; received in revised form 26 August 2006; accepted 3 October 2006 Available online 28 November 2006 Abstract A series of experiments and petrographic analyses have been run to determine the pre-eruption phase equilibria and ascent dynamics of dacitic lavas composing Black Butte, a dome complex on the flank of Mount Shasta, California. Major and trace element analyses indicate that the Black Butte magma shared a common parent with contemporaneously erupted magmas at the Shasta summit. The Black Butte lava phenocryst phase assemblage (20 v.%) consists of amphibole, plagioclase (core An77.5), and Fe–Ti oxides in a fine-grained (b0.5 mm) groundmass of plagioclase, pyroxene, Fe–Ti oxides, amphibole, and cristobalite. The phenocryst assemblage and crystal compositions are reproduced experimentally between 890 °C and 910 °C, ≥300 MPa, X- H2O =1, and oxygen fugacity=NNO+1. This study has quantified the extent of three crystallization processes occurring in the Black Butte dacite that can be used to discern ascent processes. Magma ascent rate was quantified using the widths of amphibole breakdown rims in natural samples, using an experimental calibration of rim development in a similar magma at relevant conditions.
    [Show full text]