DOCSLIB.ORG

Nonexplosive and Explosive Magma/Wet-Sediment Interaction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nonexplosive and Explosive Magma/Wet-Sediment Interaction Journal of Volcanology and Geothermal Research 181 (2009) 155–172 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas Kenneth S. Befus a,⁎, Richard E. Hanson a, Daniel P. Miggins b, John A. Breyer a, Arthur B. Busbey a a Department of Geology, Texas Christian University, Box 298830, Fort Worth, TX 76129, USA b U.S. Geological Survey, Denver Federal Center, Box 25046, Denver, CO 80225, USA article info abstract Article history: Eocene intrusion of alkaline basaltic to trachyandesitic magmas into unlithified, Upper Cretaceous Received 16 June 2008 (Maastrichtian) to Eocene fluvial strata in part of the Trans-Pecos igneous province in West Texas produced Accepted 22 December 2008 an array of features recording both nonexplosive and explosive magma/wet-sediment interaction. Intrusive Available online 13 January 2009 complexes with 40Ar/39Ar dates of ~47–46 Ma consist of coherent basalt, peperite, and disrupted sediment. Two of the complexes cutting Cretaceous strata contain masses of conglomerate derived from Eocene fluvial Keywords: deposits that, at the onset of intrusive activity, would have been N400–500 m above the present level of phreatomagmatism peperite exposure. These intrusive complexes are inferred to be remnants of diatremes that fed maar volcanoes during diatreme an early stage of magmatism in this part of the Trans-Pecos province. Disrupted Cretaceous strata along Trans-Pecos Texas diatreme margins record collapse of conduit walls during and after subsurface phreatomagmatic explosions. 40Ar/39Ar geochronology Eocene conglomerate slumped downward from higher levels during vent excavation. Coherent to pillowed basaltic intrusions emplaced at the close of explosive activity formed peperite within the conglomerate, within disrupted Cretaceous strata in the conduit walls, and within inferred remnants of the phreatomag- matic slurry that filled the vents during explosive volcanism. A younger series of intrusions with 40Ar/39Ar dates of ~42 Ma underwent nonexplosive interaction with Upper Cretaceous to Paleocene mud and sand. Dikes and sills show fluidal, billowed, quenched margins against the host strata, recording development of surface instabilities between magma and groundwater-rich sediment. Accentuation of billowed margins resulted in propagation of intrusive pillows into the adjacent sediment. More intense disruption and mingling of quenched magma with sediment locally produced fluidal and blocky peperite, but sufficient volumes of pore fluid were not heated rapidly enough to generate phreatomagmatic explosions. This work suggests that Trans-Pecos Texas may be an important locale for the study of subvolcanic phreato- magmatic processes and associated phenomena. Eocene intrusions in the study area underwent complex interactions with wet sediment at shallow levels beneath the surface in strata as old as Maastrichtian, which must have remained unlithified and rich in pore water for ~20–25 Ma. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Little previous work has been carried out on physical interactions between these intrusions and their host sedimentary sequences. Trans-Pecos Texas contains large volumes of Cenozoic igneous Here we describe mafic to intermediate Eocene intrusions that rock emplaced during arc magmatism and subsequent Basin-and- exhibit a spectrum of features formed when magma penetrated Range extension (Fig. 1; Henry et al., 1991; White et al., 2006). unlithified fluvial strata ranging in age from Cretaceous to Eocene. Widespread felsic extrusive units in the province have received most Nonexplosive interaction between magma and sediment rich in pore attention from volcanologists, but mafic to intermediate rocks are water led to formation of intrusive pillows and different types of also common and include abundant hypabyssal intrusions (e.g., peperite. Explosive interactions produced complex diatremes Maxwell et al., 1967; Henry and McDowell, 1986; Henry et al., 1989). inferred to represent the conduits of small phreatomagmatic volcanoes now eroded away. Such features are of interest because they shed light on processes occurring in the subsurface prior to and during explosive hydrovolcanism, at levels not accessible by direct ⁎ Corresponding author. observation of active maars and tuff rings. Also, they may provide E-mail address: [email protected] (K.S. Befus). constraints on paleohydrological and paleoclimatic conditions 0377-0273/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2008.12.017 156 K.S. Befus et al. / Journal of Volcanology and Geothermal Research 181 (2009) 155–172 Fig. 1. Extent of Cenozoic igneous rocks in Trans-Pecos Texas, modified from Barker (1977). Study area indicated by star. Area of Big Bend National Park is indicated by dark grey shading (green in color version). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) during the evolution of sedimentary and volcanic sequences in non- ~48–46 Ma (Henry and McDowell, 1986; Henry et al., 1986, 1989; marine depositional settings. Miggins et al., 2006). These early phases of magmatism preceded emplacement of voluminous felsic rocks throughout the province 2. Geological framework beginning at ~38 Ma (Henry and McDowell, 1986). Henry et al. (1991) inferred that subduction-related magmatism within the province gave Initial stages of Cenozoic igneous activity in the Trans-Pecos way to Basin-and-Range extensional magmatism at ~31 Ma. More province define the eastern edge of the Cordilleran magmatic arc recently, White et al. (2006) suggested that much of the Cenozoic (Barker, 1987; Price et al., 1987; Gilmer et al., 2003). A felsic stock in magmatism prior to ~27 Ma in Trans-Pecos Texas was related to roll- the western part of the province was emplaced in the Paleocene at back or break-off of the subducted slab, followed by lithosphere ~64 Ma (Gilmer et al., 2003), but the oldest known Cenozoic igneous delamination during initial stages of continental rifting. Igneous rocks rocks elsewhere in the region are Eocene and have isotopic dates of emplaced throughout the Cenozoic in the Trans-Pecos province, Fig. 2. Geologic map of study area. General geology after Horton (2006). Thickness of dikes not to scale. Boundary of Big Bend National Park is indicated; rest of area lies within privately owned Pitcock Rosillos Ranch. K.S. Befus et al. / Journal of Volcanology and Geothermal Research 181 (2009) 155–172 157 including those emplaced during early stages of arc-related magma- Table 1 tism, are characterized by alkaline, partly silica-undersaturated Chemical analyses and CIPW norms of dikes (A9b, A10a, D10), Cottonwood Wash intrusion (C15), and other discordant intrusions (A2, B6, C8) compositions (Barker, 1987; Price et al., 1987). In this paper we focus on Eocene hypabyssal intrusions present on Sample the southern flank of the Rosillos Mountains in the southeastern part A9b A10a D10 C15 A2 B6 C8 of the Trans-Pecos province, adjacent to and partly within Big Bend SiO2 48.28 48.26 56.01 53.16 45.62 48.16 41.14 National Park (Fig. 2). The study area is partly covered by Plio– TiO2 2.32 2.29 1.64 2.14 3.94 2.95 4.40 Pleistocene alluvial fan deposits shed from the Oligocene Rosillos Al2O3 18.54 18.50 17.37 17.55 17.00 18.56 18.72 FeO 11.52 11.83 8.53 9.77 11.67 11.47 15.18 Mountains quartz syenite laccolith. Cretaceous and Paleocene fluvial MnO 0.28 0.25 0.15 0.19 0.26 0.15 0.53 strata exposed beneath the fan deposits are assigned to the Aguja, MgO 3.18 4.46 1.90 2.43 4.87 3.68 4.37 Javelina, and Black Peaks Formations (Fig. 3; Horton, 2006), following CaO 8.89 7.11 4.74 6.14 10.83 9.42 10.02 the terminology of Maxwell et al. (1967) and Lehman (1988, 1991). Na2O 5.78 6.07 5.32 5.00 3.29 4.00 3.80 The Aguja Formation contains restricted outcrops of near-vent K2O 0.11 0.15 3.50 2.59 1.10 1.08 0.26 P2O5 1.10 1.09 0.83 1.02 1.42 0.52 1.58 Cretaceous intraplate basaltic phreatomagmatic deposits (Breyer LOI 7.27 7.24 1.54 2.21 3.59 2.48 7.92 et al., 2007), but there is no other evidence for local volcanism Suma 91.05 90.98 97.42 95.74 95.52 95.65 89.60 until the Eocene. The Javelina Formation and succeeding units Zr 323 319 480 325 197 202 201 were deposited within the intermontane Tornillo basin, which was Nb 48 46 60 47 33 25 35 Y38414338352733 delimited by regions that underwent uplift during latest Cretaceous Q ––––––– to Paleogene Laramide deformation (Lehman, 1991). Vertebrate or 0.65 0.89 20.68 15.31 6.50 6.38 1.54 fossils generally provide good age control on stratigraphic units ab 36.22 37.64 45.02 41.79 24.39 28.62 19.80 within the Tornillo basin (Fig. 3; Lehman,1985; Schiebout et al.,1987; an 24.32 22.79 13.18 17.79 28.37 29.50 33.25 – Lehman, 1991; Lehman and Coulson, 2002). ne 6.87 7.44 0.28 1.87 2.83 6.69 fi di 10.69 4.51 4.18 1.10 13.29 11.59 5.19 Ma c to intermediate intrusions in the study area include a series hy ––1.08 ––– – of east–northeast-trending, generally subvertical dikes (Fig. 2), as well ol 13.80 18.84 10.08 12.34 13.05 12.94 19.54 as less common sills and inclined sheets. Two discordant intrusive mt 3.36 3.32 2.38 3.10 5.71 4.27 6.39 masses with complex internal makeup occur in the southwestern part il 4.41 4.35 3.11 4.06 7.48 5.60 8.36 ap 2.54 2.52 1.93 2.36 3.30 1.21 3.65 of the study area (“western intrusive complexes” in Fig.
Load more

Recommended publications
  • Field Geology and Petrologic Investigation of the Strawberry Volcanics, Northeast Oregon
    Portland State University PDXScholar Dissertations and Theses Dissertations and Theses Winter 2-24-2016 Field Geology and Petrologic Investigation of the Strawberry Volcanics, Northeast Oregon Arron Richard Steiner Portland State University Follow this and additional works at: https://pdxscholar.library.pdx.edu/open_access_etds Part of the Geology Commons, and the Volcanology Commons Let us know how access to this document benefits ou.y Recommended Citation Steiner, Arron Richard, "Field Geology and Petrologic Investigation of the Strawberry Volcanics, Northeast Oregon" (2016). Dissertations and Theses. Paper 2712. https://doi.org/10.15760/etd.2708 This Dissertation is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. Field Geology and Petrologic Investigation of the Strawberry Volcanics, Northeast Oregon by Arron Richard Steiner A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Sciences and Resources: Geology Dissertation Committee: Martin J. Streck, Chair Michael L. Cummings Jonathan Fink John A.Wolff Dirk Iwata-Reuyl Portland State University 2016 © 2015 Arron Richard Steiner i ABSTRACT The Strawberry Volcanics of Northeast Oregon are a group of geochemically related lavas with a diverse chemical range (basalt to rhyolite) that erupted between 16.2 and 12.5 Ma and co-erupted with the large, (~200,000 km3) Middle Miocene tholeiitic lavas of the Columbia River Basalt Group (CRBG), which erupted near and geographically surround the Strawberry Volcanics. The rhyolitic lavas of the Strawberry Volcanics produced the oldest 40Ar/39Ar ages measured in this study with ages ranging from 16.2 Ma to 14.6 Ma, and have an estimated total erupted volume of 100 km3.
    [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]
  • Oaks of the Chihuahuan Desert Region
    International Oaks by Michael Martin Melendrez Los Lunas, New Mexico resented below are 23 species of white oak, six of black • oak, and two intermediate or golden oaks, found in the southwestern United States (primarily New Mexico, Ari­ zona, and western Texas). These nutnbers tnay be disputed by some oaks students. Differences of opinion exist as to the true boundaries of the Chihuahuan Desert the potential hybrid sta­ tus of sotne of the oaks, and their delineation. Also new oaks not previously known to occur in the area are continually dis­ covered. Counting the additional oaks found in the adjacent Mexican State of Chihuahua, there are n1ore than 60 species. The Chihuahuan Desert Region is truly The Land o.fOaks. The production nursery industry of our area has started, on a small scale, the introduction of oaks with a limited species selec­ tion. Unfortunately the southern live oak (Quercus virginiana) usually is the first one to be grown and sold, and it is commonly promoted as the best oak for the desert cit­ ies of the Southwest. The species of oak na­ < Guy & Edith Sternberg tive to this arid part of Author ,\1/ichae/ i\1/elendrez standing below Q. ari zonica the country are 1nuch in Catwalk Can• l'0 /1, Gila National Forest. New Mexico. contd. on pg. 22 International Gales • • • contd. from pg. 21 better adapted here, and thus tnake bet­ ter choices for shade trees than the southern live oak. • At our nursery production progran1 in Los Lunas, New Mexico, at 4,900 feet el­ evation and USDA Zone 6b, the native oaks outperform the southern live oak in speed of growth, heat tolerance in a con­ tainer, and over-wintering success.
    [Show full text]
  • Alkalic-Type Epithermal Gold Deposit Model
    Alkalic-Type Epithermal Gold Deposit Model Chapter R of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–R U.S. Department of the Interior U.S. Geological Survey Cover. Photographs of alkalic-type epithermal gold deposits and ores. Upper left: Cripple Creek, Colorado—One of the largest alkalic-type epithermal gold deposits in the world showing the Cresson open pit looking southwest. Note the green funnel-shaped area along the pit wall is lamprophyre of the Cresson Pipe, a common alkaline rock type in these deposits. The Cresson Pipe was mined by historic underground methods and produced some of the richest ores in the district. The holes that are visible along several benches in the pit (bottom portion of photograph) are historic underground mine levels. (Photograph by Karen Kelley, USGS, April, 2002). Upper right: High-grade gold ore from the Porgera deposit in Papua New Guinea showing native gold intergrown with gold-silver telluride minerals (silvery) and pyrite. (Photograph by Jeremy Richards, University of Alberta, Canada, 2013, used with permission). Lower left: Mayflower Mine, Montana—High-grade hessite, petzite, benleonardite, and coloradoite in limestone. (Photograph by Paul Spry, Iowa State University, 1995, used with permission). Lower right: View of north rim of Navilawa Caldera, which hosts the Banana Creek prospect, Fiji, from the portal of the Tuvatu prospect. (Photograph by Paul Spry, Iowa State University, 2007, used with permission). Alkalic-Type Epithermal Gold Deposit Model By Karen D. Kelley, Paul G. Spry, Virginia T. McLemore, David L. Fey, and Eric D. Anderson Chapter R of Mineral Deposit Models for Resource Assessment Scientific Investigations Report 2010–5070–R U.S.
    [Show full text]
  • Analogues for Radioactive Waste For~1S •
    PNL-2776 UC-70 3 3679 00049 3611 ,. NATURALLY OCCURRING GLASSES: ANALOGUES FOR RADIOACTIVE WASTE FOR~1S • Rodney C. Ewing Richard F. Haaker Department of Geology University of New Mexico Albuquerque, ~ew Mexico 87131 April 1979 Prepared for the U.S. Department of Energy under Contract EY-76-C-06-1830 Pacifi c i'lorthwest Laboratory Richland, Washington 99352 TABLE OF CONTENTS List of Tables. i i List of Figures iii Acknowledgements. Introduction. 3 Natural Glasses 5 Volcanic Glasses 9 Physical Properties 10 Compos i ti on . 10 Age Distributions 10 Alteration. 27 Devitrification 29 Hydration 32 Tekti tes. 37 Physical Properties 38 Composition . 38 Age Distributions . 38 Alteration, Hydration 44 and Devitrification Lunar Glasses 44 Summary . 49 Applications to Radioactive Waste Disposal. 51 Recommenda ti ons 59 References 61 Glossary 65 i LIST OF TABLES 1. Petrographic Properties of Natural Glasses 6 2. Average Densities of Natural Glasses 11 3. Density of Crystalline Rock and Corresponding Glass 11 4. Glass and Glassy Rocks: Compressibility 12 5. Glass and Glassy Rocks: Elastic Constants 13 6. Glass: Effect of Temperature on Elastic Constants 13 7. Strength of Hollow Cylinders of Glass Under External 14 Hydrostatic Pressure 8. Shearing Strength Under High Confining Pressure 14 9. Conductivity of Glass 15 10. Viscosity of Miscellaneous Glasses 16 11. Typical Compositions for Volcanic Glasses 18 12. Selected Physical Properties of Tektites 39 13. Elastic Constants 40 14. Average Composition of Tektites 41 15. K-Ar and Fission-Track Ages of Tektite Strewn Fields 42 16. Microprobe Analyses of Various Apollo 11 Glasses 46 17.
    [Show full text]
  • Ocean Drilling Program Scientific Results Volume
    Eldholm, O., Thiede, J., Taylor, E., et al., 1989 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 104 19. CHEMICAL STRATIGRAPHY AND PETROLOGY OF THE VORING PLATEAU THOLEIITIC LAVAS AND INTERLAYERED VOLCANICLASTIC SEDIMENTS AT ODP HOLE 642E1 L. G. Viereck,2'3 J. Hertogen,4 L. M. Parson,5 A. C. Morton,6 D. Love,7 and I. L. Gibson7 ABSTRACT During Ocean Drilling Program Leg 104 a 900-m-thick sequence of volcanic rocks was drilled at Hole 642E on the Wring Plateau, Norwegian Sea. This sequence erupted in two series (upper and lower series) upon continental base• ment. The upper series corresponds to the seaward-dipping seismic reflectors and comprises a succession of about 122 flows of transitional oceanic tholeiite composition. They have been subdivided into several formations consisting of flows related to each other by crystal fractionation processes, magma mixing, or both. Major- and trace-element chem• istry indicates affinities to Tertiary plateau lavas of northeast Greenland and to Holocene lavas from shallow transi• tional segments of the Mid-Atlantic Ridge, such as Reykjanes Ridge. The tholeiitic magmas have been derived from a slightly LREE-depleted mantle source. Two tholeiitic dikes that intruded the lower series derive from an extremely de• pleted mantle source. Interlayered volcaniclastic sediments are dominantly ferrobasaltic and more differentiated. They appear to come from a LREE-enriched mantle source, and may have been erupted in close vicinity of the Vriring Pla• teau during hydroclastic eruptions. The two tholeiitic dikes that intruded the lower series as well as some flows at the base of the upper series show evidence of assimilation of continental upper crustal material.
    [Show full text]
  • Icelandic Hyaloclastite Tuffs Petrophysical Properties, Alteration and Geochemical Mobility
    Icelandic Hyaloclastite Tuffs Petrophysical Properties, Alteration and Geochemical Mobility Hjalti Franzson Gudmundur H. Gudfinnsson Julia Frolova Helga M. Helgadóttir Bruce Pauly Anette K. Mortensen Sveinn P. Jakobsson Prepared for National Energy Authority and Reykjavík Energy ÍSOR-2011/064 ICELAND GEOSURVEY Reykjavík: Orkugardur, Grensásvegur 9, 108 Reykjavík, Iceland - Tel.: 528 1500 - Fax: 528 1699 Akureyri: Rangárvellir, P.O. Box 30, 602 Akureyri, Iceland - Tel.: 528 1500 - Fax: 528 1599 [email protected] - www.isor.is Report Project no.: 540105 Icelandic Hyaloclastite Tuffs Petrophysical Properties, Alteration and Geochemical Mobility Hjalti Franzson Gudmundur H. Gudfinnsson Julia Frolova Helga M. Helgadóttir Bruce Pauly Anette K. Mortensen Sveinn P. Jakobsson Prepared for National Energy Authority and Reykjavík Energy ÍSOR-2011/064 December 2011 Key page Report no. Date Distribution ÍSOR-2011/064 December 2011 Open Closed Report name / Main and subheadings Number of copies Icelandic Hyaloclastite Tuffs. Petrophysical Properties, Alteration 7 and Geochemical Mobility Number of pages 103 Authors Project manager Hjalti Franzson, Gudmundur H. Gudfinnsson, Julia Frolova, Hjalti Franzson Helga M. Helgadóttir, Bruce Pauly, Anette K. Mortensen and Sveinn P. Jakobsson Classification of report Project no. 540105 Prepared for National Energy Authority and Reykjavík Energy Cooperators Moscow University, University of California in Davis, Natural History Museum in Iceland Abstract This study attempts to define the properties of hyaloclastite formations which control their petrophysical characteristics during their progressive alteration. It is based on 140 tuffaceous cores from last glaciation to 2–3 m y. The water content shows a progressive increase with alteration to about 12%, which mainly is bound in the smectite and zeolite alteration minerals.
    [Show full text]
  • The Alkaline Volcanic Rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details
    The alkaline volcanic rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars Details Meeting 2016 Fall Meeting Section Planetary Sciences Session Terrestrial Analogs for Planetary Processes: Oceans, Volcanoes, Impacts, and Dunes I Identifier P31E-01 Authors Haberle, C W*, Mars Space Flight Facility, Arizona State University, Tempe, AZ, United States Hughes, S S, Idaho State University, Idaho Falls, ID, United States Kobs-Nawotniak, S E, Department of Geosciences, Idaho State University, Idaho Falls, ID, United States Christensen, P R, Arizona State University, Tempe, AZ, United States Index Sediment transport [4558] Terms Atmospheres [5405] Titan [6281] Venus [6295] Abstract Idaho's Eastern Snake River Plain (ESRP) is host to extensive expressions of basaltic volcanism dominated by non evolved olivine tholeiites (NEOT) with localized occurrences of evolved lavas. Craters of the Moon National Monument (COTM) is a polygenetic lava field comprised of more than 60 lava flows emplaced during 8 eruptive periods spanning the last 15 kyrs. The most recent eruptive period (period A; 2500-2000 yr B.P.) produced flows with total alkali vs. silica classifications spanning basalt to trachyte. Coeval with the emplacement of the COTM period A volcanic pile was the emplacement of the Wapi and Kings Bowl NEOT 70 km SSE of COTM along the Great Rift. Previous investigations have determined a genetic link between these two compositionally distinct volcanic centers where COTM compositions can be generated from NEOT melts through complex ascent paths and variable degrees of fractionation and assimilation of lower-middle crustal materials. The Mars Exploration Rover, Spirit, conducted a robotic investigation of Gusev crater from 2004-2010.
    [Show full text]
  • THE PETROCHEMISTRY of JAKE M: a MARTIAN MUGEARITE. Stolper
    44th Lunar and Planetary Science Conference (2013) 1685.pdf THE PETROCHEMISTRY OF JAKE_M: A MARTIAN MUGEARITE. Stolper, E.M.1, Baker, M.B.1, Fisk, M.2, Gellert, R.3, King, P.L.4, McLennan, S.M.5, Minitti, M.6, Newcombe, M.1, Schmidt, M.E. 7, Treiman, A.H.8, and the MSL Science Team. 1Caltech, Pasadena, CA 91125, 2Oregon State Univ., 3Univ. Guelph, 4Res. School Earth Sci., ANU, 5SUNY, Stony Brook, 6Applied Phys. Lab., Johns Hopkins Univ., 7Brock Univ., 8Lunar & Planet. Inst. Introduction: Rock “Jake_M” (JM; named for JPL The surface of JM was not brushed or abraded prior engineer Jake Matijevic) was the first sample analyzed to analysis, so the APXS analyses probably include by the Alpha Particle X-ray Spectrometer (APXS) in- contributions from surface coatings, including adhering strument on MSL [1]. Although it is an isolated frag- dust, and these are the probable source of the S and Cl ment lacking field context, its dark color and apparently in JM. Experience with MER, however, indicates that fine-grained texture suggested it was a relatively homo- the characteristics of rock compositions are typically geneous igneous rock and thus an appropriate sample to not obscured by surface components, and the levels of S initiate the APXS analytical program. We report here and Cl in JM are lower than virtually all unbrushed the preliminary APXS analyses of JM and a plausible analyses from the Spirit rover and lower than many of interpretation of their significance for petrogenesis. the brushed analyses, so the level of surface contamina- Results: Three spots on JM were analyzed with the tion and alteration are likely relatively minor [5].
    [Show full text]
  • Deep Sea Drilling Project Initial Reports Volume 59
    37. THE GEOCHEMISTRY, MINERALOGY, AND PETROLOGY OF BASALTS FROM THE WEST PHILIPPINE AND PARECE VELA BASINS AND FROM THE PALAU-KYUSHU AND WEST MARIANA RIDGES, DEEP SEA DRILLING PROJECT LEG 59 David P. Mattey, Nicholas G. Marsh, and John Tarney,1 Department of Geological Sciences, University of Birmingham, Birmingham B15 2TT, England INTRODUCTION netic fabric of the Parece Vela Basin suggest a similar origin—the sundering of the Palau-Kyushu Ridge in the Legs 59 and 60 of the International Phase of Oceanic late Oligocene (Karig, 1975). The origin of the West Drilling (IPOD) were designed to study the nature and Philippine Basin is less clear, however, and the age and history of volcanism of the active Mariana arc, its cur- magnetic fabric of this basin remain controversial. Re- rently spreading inter-arc basin (the Mariana Trough), cent studies of rocks dredged from the Mariana Trough and the series of inactive basins and intervening ridges (Hart et al., 1972), the Lau Basin (Hawkins, 1976), and that lie to the west (Fig. 1). The older basins and ridges the Scotia Sea (Saunders and Tarney, 1979) all reveal were drilled during Leg 59 as the first part of a transect that these basins are floored by basalts geochemically of single-bit holes drilled in each major basin and ridge. similar to basalts erupted at mid-ocean ridges. The for- The eastern part of the transect—the technically active mation of active back-arc basins (e.g., the East Scotia region—was drilled during Leg 60. Sea, Barker 1970) in the Mariana Trough (Karig et al., The evolution of island-arc volcanos and magma 1978) is considered by many authors to be the result of genesis associated with lithospheric subduction remain seafloor spreading broadly similar to that associated some of the most complex petrologic problems con- with a mid-ocean ridge (e.g., Karig, 1971).
    [Show full text]
  • 29. Sulfur Isotope Ratios of Leg 126 Igneous Rocks1
    Taylor, B., Fujioka, K., et al., 1992 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 126 29. SULFUR ISOTOPE RATIOS OF LEG 126 IGNEOUS ROCKS1 Peter Torssander2 ABSTRACT Sulfur isotope ratios have been determined in 19 selected igneous rocks from Leg 126. The δ34S of the analyzed rocks ranges from -0.1 o/00 to +19.60 o/oo. The overall variation in sulfur isotope composition of the rocks is caused by varying degrees of seawater alteration. Most of the samples are altered by seawater and only five of them are considered to have maintained their magmatic sulfur isotope composition. These samples are all from the backarc sites and have δ34S values varying from +0.2 o/oo to +1.6 o/oo , of which the high δ34S values suggest that the earliest magmas in the rift are more arc-like in their sulfur isotope composition than the later magmas. The δ34S values from the forearc sites are similar to or heavier than the sulfur isotope composition of the present arc. INTRODUCTION from 0 o/oo to +9 o/00 (Ueda and Sakai, 1984), which could arise from inhomogeneities in the mantle but are more likely a result of contami- Sulfur is a volatile element that can be degassed during the ascent nation from the subducting slab (A. Ueda, pers. comm., 1988). of basaltic magma. Degassing causes sulfur isotope fractionation; the Leg 126 of the Ocean Drilling Program (ODP) drilled seven sites isotopic composition of sulfur in rocks can vary with the concentra- in the backarc and forearc of the Izu-Bonin Arc (Fig.
    [Show full text]
  • The Boring Volcanic Field of the Portland-Vancouver Area, Oregon and Washington: Tectonically Anomalous Forearc Volcanism in an Urban Setting
    Downloaded from fieldguides.gsapubs.org on April 29, 2010 The Geological Society of America Field Guide 15 2009 The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: Tectonically anomalous forearc volcanism in an urban setting Russell C. Evarts U.S. Geological Survey, 345 Middlefi eld Road, Menlo Park, California 94025, USA Richard M. Conrey GeoAnalytical Laboratory, School of Earth and Environmental Sciences, Washington State University, Pullman, Washington 99164, USA Robert J. Fleck Jonathan T. Hagstrum U.S. Geological Survey, 345 Middlefi eld Road, Menlo Park, California 94025, USA ABSTRACT More than 80 small volcanoes are scattered throughout the Portland-Vancouver metropolitan area of northwestern Oregon and southwestern Washington. These vol- canoes constitute the Boring Volcanic Field, which is centered in the Neogene Port- land Basin and merges to the east with coeval volcanic centers of the High Cascade volcanic arc. Although the character of volcanic activity is typical of many mono- genetic volcanic fi elds, its tectonic setting is not, being located in the forearc of the Cascadia subduction system well trenchward of the volcanic-arc axis. The history and petrology of this anomalous volcanic fi eld have been elucidated by a comprehensive program of geologic mapping, geochemistry, 40Ar/39Ar geochronology, and paleomag- netic studies. Volcanism began at 2.6 Ma with eruption of low-K tholeiite and related lavas in the southern part of the Portland Basin. At 1.6 Ma, following a hiatus of ~0.8 m.y., similar lavas erupted a few kilometers to the north, after which volcanism became widely dispersed, compositionally variable, and more or less continuous, with an average recurrence interval of 15,000 yr.
    [Show full text]