DOCSLIB.ORG

Isotopic Composition of Oligocene Mafic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Isotopic Composition of Oligocene Mafic JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 96, NO. B8, PAGES 13,593-13,608,JULY 30, 1991 IsotopicComposition of OligoceneMafic VolcanicRocks in the Northern Rio GrandeRift: Evidencefor Contributionsof AncientIntraplate andSubduction Magmatism to Evolutionof the Lithosphere CLARK M. JOHNSON Departmentof Geologyand Geophysics,University of Wisconsin,Madison REN A. THOMPSON U.S. Geological Survey,Denver, Colorado Mafic lavas eruptedduring initiation of regional extensionat 26 Ma in the northernRio Granderift werederived from at leasttwo isotopicallydistinct mantle sources. One is characterizedby 87Sr/86Sr= 0.70495,•md -- -4,2ø6pb/2ø4pb = 18.2, and the other by 87Sr/86Sr = 0.7044, •Nd -- 0, 2ø6pb/2ø4pb= 18.2. The 1OW-Smdvalue source (MANTLE 1) is interpretedto largelyreflect the isotopiccompositions of the lithosphericmantle in the region. Isotopiccompositions of Cenozoicmafic lavasand Proterozoicrocks areused to constrainmodels for evolutionof thelithosphere. The low 8Ndvalues of theMANTLE 1 componentwere probablyproduced by evolution of a light rare earth element-enrichedupper mantle or inputof low-sNd material. during development of thelithosphere in theEarly Proterozoic. The 8Nd values and2ø6pb/2ø4pb ratios •n evolvedrocks are as low as-7 and 17.3,respectively, indicating interaction with lowercrust that had •Na -< -12 and 2ø6pb/2ø4pb _<17.0. Initial87Sr/86Sr ratios both increase and decrease slightly in evolved rocks, indicatinginteraction with lower crust that had Sr isotoperatios that were generallysimilar to thoseof themantle. The 8Nd value of themodern lithospheric mantle beneath the northernRio Grande rift is >18 units lower than the projectedmodern values of the asthenospheric mantlefrom which the Proterozoic crust was originally derived. The higher-ema value source (MANTLE 2) may reflect mixing of asthenosphereand lithospherecomponents. The mantle sourcefor most late Cenozoicmafic lavasin the northernRio Granderift regionlies at 2ø7pb/2ø4pbratios that are signifi- cantlyhigher than the 2ø6pb/2ø4pb- 2ø7pb/2ø4pb array defined by Proterozoiccrust in the region. Althoughthe crustalarray is alsodisplaced to higher2øTpb/2ø4pb ratios as comparedto the northern hemisphereoceanic mantle a•ray, indicating incorporationof Archean Pb during crust formation, the stillhigher 2øTpb/2ø4pb ratios in theRio Granderift mantlesource is interpretedto reflectcontinued input of ArcheanPb into the developingEarly Proterozoiclithospheric mantle after crust formation. These relations are strong evidence that the lithosphere became stabilized shortly after the major crust formation eventsin the Early Proterozoic. INTRODUCTION (Figure 1) preservesthe largestvolume of early rift (26 Ma) Rift-related volcanism in the northern Rio Grande rift is volcanic rocks in the northern Rio Grande rift. These lavas largely basaltic in composition, in contrast to prerift provide an importantand previouslypoorly known view magmatismin the region, which was dominatedby inter- of volcanism that occurredduring inception of the Rio mediate- to silicic-compositionash flow tuffs and related Grande rift. lavas [Steven, 1975; Lipman and Mehnert, 1975]. Most We reportSr, Nd, andPb isotopedata for earlyrift mafic studies of rift-related volcanic rocks in the northern Rio lavas of the Hinsdale Formationthat are exposedat San Granderift have concentratedon relatively youngvolcanic Luis Hills. These data bear on mantle sources of volcanism fields that formed significantlyafter initiationof extension. associatedwith inceptionof rifting andmodels for develop- Theseinclude the TaosPlateau, Rayton-Clayton, and Ocate ment of the lithosphericmantle. Compositionalvariations fields (Figure 1) [Stormer, 1972a, 1972b; Lipman and and isotopic compositionsindicate that many San Luis Mehnert, 1979; O'Neill and Mehnert, 1988], as well as Hills magmasinteracted with lower crust,as hasbeen pro- lavas exposed at Los Mogotes volcano, in the Tusas posedfor otherlavas in the region. Detailedconsideration Mountains, and near Amalia (Figure 1)[Lipman and of chemical and petrologic characteristicsof the lavas, Mehnert, 1975; Lipman et al., 1986]. Early rift lavas are however, allows identification of primitive, uncontami- exposedonly on intrarift horstsand on the flanks of the rift natedcompositions that can be usedto determineisotopic in the SanJuan and Latir volcanicfields (Figure 1) [Lipman compositionsof the mantle. The data define two mantle and Mehnert, 1975, 1979; Thompsonet al., 1986; Lipman sourceregions, at leastone of which is interpretedto reflect et al., 1986]. Late Cenozoic basaltic lavas in northern the lithosphericmantle that had beenenriched in light rare Coloradoare temporallycorrelative with rift-relatedvolca- earth elements(LREE) during stabilizationand growth of nic rocksbut were eruptedsignificantly outside the Rio the lithospherein the Proterozoic. Grande depression[Larson et al., 1975]. San Luis Hills GEOLOGY AND PETROLOGY OF SAN LUIS HILLS LAVAS Copyright1991 by the AmericanGeophysical Union. San Luis Hills are the surface expressionof a major Papernumber 91JB00342. intrarift horst within the northern Rio Grande rift that is 0148-0227/91/91 JB-00342505.00 largelyburied beneath late Cenozoicsedimentary and vol- 13,593 13,594 JOHNSONAND THOMPSON:ISOTOPIC COMPOSITION OF MAFIC VOLCANICROCKS 400 ] I•'SUITE 1i A ' i ß SUITE ,.3 ß ß I- m [ I ,,,,..."', ' , ..................... • LATIR m ',,, .•. LOS ß -....... ,ooJ ,,,,,,, . mTAOS '•"•', -,,, ,.•' -" xl.•.AMALIA ............. © '-... © ,SAN LUIS o.... •*.,,,, ....•...... :•": ...... :..... :...... :..... :-*'--: .....:...... :..... •...... HILLS " B COLORADO .340• TAOS- ALKALIC NEW MEXICO ..•_.. 280 ......... ........-,i;,' HILLSSANLUIS •, 220 e•" ,...... © .................................. • // ............. PROTEROZOIC BASEMENT 160ß1 -,- .•- - •/•'.•.•.;-",a,, ,,.•"•/ / AMALIA•F ............... ............ MID-CENOZOIC ! '• ..'_.•.' ? ./ . ............. CALDERAS • I I I I I 100 1_-:,'-..-".•; ß i ...... •!" ............... ß ................... o 5o IOOKM :1',, ' ............•-X' •os - •.o.[,,•,• Fig. 1. Generalized map of the northern Rio Grande rift region 4.0i-- " ß.......... ß ß ß --ß LOS ß MOGOTE$ß ß ß ß ß . ß ß ß 48 52 56 60 64 showing major Cenozoic volcanic areas, including San Luis Hills, the subjectof this report. SJVF, San Juanvolcanic field; TPVF, Taos wf%SiO 2 Plateau volcanic field; TBM, Timber Mountain and Brushy Moun- 400 • C tain; AL, Amalia lavas; LVF, Latir volcanic field; R-CVF, Rayton- = Clayton volcanic field; OVF, Ocate volcanic field; LM, Los Mogotes LOSMOGOTES • volcano. ,.300i ß ' ''' AMALIA canic rocks [Kleinkopf et al., 1970]. Other surfaceexpo- (• ...........-=/•'-...- -• i .... suresinclude Timber Mountain and BrushyMountain (Fig- ure 1) [Thompsonet al., 1986]. Early rift lavas (26.4-25.7 E200 Ma) of the lower Hinsdale Formation, the subject of this '-.•L.C... report, overlie intermediate-compositionlavas at San Luis 1O0 '"'•<.::... '- TAOS Hills that are temporally correlativewith precalderalavas of the Latir volcanic field [Thompson et al., this issue]. Silicic volcanic rocks are conspicuouslymissing from San 0 ß ß ß ß ß , ß , ß ß Luis Hills, in contrastto volcanic sectionsexposed on the 80 120 160 200 240 2•0 320 flanks of the rift in the San Juan and Latir volcanic fields. pprn Zr Particularly notable is the absence of the Amalia Tuff, Fig. 2. Chemicalvariation diagrams (a) Cr-SiO2, (b) Zr-SiO2, and which eruptedfrom the Questacaldera of the Latir volcanic (c) Cr-Zr. Symbols shown for lower Hinsdale Formation lavas field contemporaneouswith initiation of regional extension exposedat San Luis Hills, the subjectof this report;outlines for other lavasin the northernrift region also shown. The samesymbols and at 26 Ma [Lipman et al., 1986; Hagstrum and Lipman, outlinesused for Figures3, 4, 5, 6, 7, and 10. Data from Dungan et 1986]. These relations, in addition to the general lack of al. [1986],Johnsonand Lipman [1988], Thompsonet al. [this issue], Los Pinos Formation age sedimentary rocks at San Luis andM. Dungan(unpublished data, 1988). Asterisk,estimated SiO 2 Hills [Thompsonand Machett, 1989], suggestthat the horst contentfor suite 3 sample205. was a topographichigh during early evolutionof the north- em Rio Grande rift. the San Juan volcanic field [Lipman and Mehnert, 1975]. Early rift lavas at San Luis Hills are divided into four Suite 2 lavas contain 10-15 vol % phenocrystsof plagio- suitesbased on petrographiccharacteristics, chemical com- clase and subordinate clinopyroxene and minor olivine, positions,and stratigraphicposition. Suites 1-4 representa have slightly higher alkali contentsthan suite 1 rocks, at a general sequencefrom oldest to youngest. Suite 1 lavas given SiO2 content, and are trachybasaltsand trachyande- occur at the base of the sectionand representN60 vol % of sites. Suite 2 lavas are notable for their very high Rb and the lavas exposed at San Luis Hills. They erupted from Th contents,up to 120 and 14 ppm, respectively,as com- multiple centers and are characterizedby up to 20 vol % pared to most Hinsdale Formation lavas in the region [Lip- phenocrystsof olivine and clinopyroxene[Thompson et al., man et al., 1973]. The high Rb and Th contents,however, this issue]. These lavas are transitional between tholeiite are similar to those of precalderalavas of the nearby Latir and alkali basalts,as determinedby Na20+K20-SiO 2 varia- volcanic field [Johnsonand Lipman, 1988]. Suite 3 lavas tions, and are similar to other Hinsdale Formation lavas are tholeiitic basalts and andesites.
Load more

Recommended publications
  • Baylor Geological Studies
    BAYLORGEOLOGICA L STUDIES PAUL N. DOLLIVER Creative thinking is more important than elaborate FRANK PH.D. PROFESSOR OF GEOLOGY BAYLOR UNIVERSITY 1929-1934 Objectives of Geological Training at Baylor The training of a geologist in a university covers but a few years; his education continues throughout his active life. The purposes of train­ ing geologists at Baylor University are to provide a sound basis of understanding and to foster a truly geological point of view, both of which are essential for continued professional growth. The staff considers geology to be unique among sciences since it is primarily a field science. All geologic research in­ cluding that done in laboratories must be firmly supported by field observations. The student is encouraged to develop an inquiring ob­ jective attitude and to examine critically all geological concepts and principles. The development of a mature and professional attitude toward geology and geological research is a principal concern of the department. Frontis. Sunset over the Canadian River from near the abandoned settlement of Old Tascosa, Texas. The rampart-like cliffs on the horizon first inspired the name "Llano Estacado" (Palisaded Plain) among Coronado's men. THE BAYLOR UNIVERSITY PRESS WACO, TEXAS BAYLOR GEOLOGICAL STUDIES BULLETIN NO. 42 Cenozoic Evolution of the Canadian River Basin Paul N. DoUiver BAYLOR UNIVERSITY Department of Geology Waco, Texas Spring 1984 Baylor Geological Studies EDITORIAL STAFF Jean M. Spencer Jenness, M.S., Editor environmental and medical geology O. T. Ph.D., Advisor, Cartographic Editor what have you Peter M. Allen, Ph.D. urban and environmental geology, hydrology Harold H. Beaver, Ph.D.
    [Show full text]
  • Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado by Peter W
    Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado By Peter W. Lipman Pamphlet to accompany Geologic Investigations Series I–2799 dacite Ceobolla Creek Tuff Nelson Mountain Tuff, rhyolite Rat Creek Tuff, dacite Cebolla Creek Tuff Rat Creek Tuff, rhyolite Wheeler Geologic Monument (Half Moon Pass quadrangle) provides exceptional exposures of three outflow tuff sheets erupted from the San Luis caldera complex. Lowest sheet is Rat Creek Tuff, which is nonwelded throughout but grades upward from light-tan rhyolite (~74% SiO2) into pale brown dacite (~66% SiO2) that contains sparse dark-brown andesitic scoria. Distinctive hornblende-rich middle Cebolla Creek Tuff contains basal surge beds, overlain by vitrophyre of uniform mafic dacite that becomes less welded upward. Uppermost Nelson Mountain Tuff consists of nonwelded to weakly welded, crystal-poor rhyolite, which grades upward to a densely welded caprock of crystal-rich dacite (~68% SiO2). White arrows show contacts between outflow units. 2006 U.S. Department of the Interior U.S. Geological Survey CONTENTS Geologic setting . 1 Volcanism . 1 Structure . 2 Methods of study . 3 Description of map units . 4 Surficial deposits . 4 Glacial deposits . 4 Postcaldera volcanic rocks . 4 Hinsdale Formation . 4 Los Pinos Formation . 5 Oligocene volcanic rocks . 5 Rocks of the Creede Caldera cycle . 5 Creede Formation . 5 Fisher Dacite . 5 Snowshoe Mountain Tuff . 6 Rocks of the San Luis caldera complex . 7 Rocks of the Nelson Mountain caldera cycle . 7 Rocks of the Cebolla Creek caldera cycle . 9 Rocks of the Rat Creek caldera cycle . 10 Lava flows premonitory(?) to San Luis caldera complex . .11 Rocks of the South River caldera cycle .
    [Show full text]
  • Stratigraphic Correlation Chart for Western Colorado and Northwestern New Mexico
    New Mexico Geological Society Guidebook, 32nd Field Conference, Western Slope Colorado, 1981 75 STRATIGRAPHIC CORRELATION CHART FOR WESTERN COLORADO AND NORTHWESTERN NEW MEXICO M. E. MacLACHLAN U.S. Geological Survey Denver, Colorado 80225 INTRODUCTION De Chelly Sandstone (or De Chelly Sandstone Member of the The stratigraphic nomenclature applied in various parts of west- Cutler Formation) of the west side of the basin is thought to ern Colorado, northwestern New Mexico, and a small part of east- correlate with the Glorieta Sandstone of the south side of the central Utah is summarized in the accompanying chart (fig. 1). The basin. locations of the areas, indicated by letters, are shown on the index map (fig. 2). Sources of information used in compiling the chart are Cols. B.-C. shown by numbers in brackets beneath the headings for the col- Age determinations on the Hinsdale Formation in parts of the umns. The numbers are keyed to references in an accompanying volcanic field range from 4.7 to 23.4 m.y. on basalts and 4.8 to list. Ages where known are shown by numbers in parentheses in 22.4 m.y. on rhyolites (Lipman, 1975, p. 6, p. 90-100). millions of years after the rock name or in parentheses on the line The early intermediate-composition volcanics and related rocks separating two chronostratigraphic units. include several named units of limited areal extent, but of simi- No Quaternary rocks nor small igneous bodies, such as dikes, lar age and petrology—the West Elk Breccia at Powderhorn; the have been included on this chart.
    [Show full text]
  • Cenozoic Thermal, Mechanical and Tectonic Evolution of the Rio Grande Rift
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 91, NO. B6, PAGES 6263-6276, MAY 10, 1986 Cenozoic Thermal, Mechanical and Tectonic Evolution of the Rio Grande Rift PAUL MORGAN1 Departmentof Geosciences,Purdue University,West Lafayette, Indiana WILLIAM R. SEAGER Departmentof Earth Sciences,New Mexico State University,Las Cruces MATTHEW P. GOLOMBEK Jet PropulsionLaboratory, CaliforniaInstitute of Technology,Pasadena Careful documentationof the Cenozoicgeologic history of the Rio Grande rift in New Mexico reveals a complexsequence of events.At least two phasesof extensionhave been identified.An early phase of extensionbegan in the mid-Oligocene(about 30 Ma) and may have continuedto the early Miocene (about 18 Ma). This phaseof extensionwas characterizedby local high-strainextension events (locally, 50-100%,regionally, 30-50%), low-anglefaulting, and the developmentof broad, relativelyshallow basins, all indicatingan approximatelyNE-SW •-25ø extensiondirection, consistent with the regionalstress field at that time.Extension events were not synchronousduring early phase extension and were often temporally and spatiallyassociated with major magmatism.A late phaseof extensionoccurred primarily in the late Miocene(10-5 Ma) with minor extensioncontinuing to the present.It was characterizedby apparently synchronous,high-angle faulting givinglarge verticalstrains with relativelyminor lateral strain (5-20%) whichproduced the moderuRio Granderift morphology.Extension direction was approximatelyE-W, consistentwith the contemporaryregional stress field. Late phasegraben or half-grabenbasins cut and often obscureearly phasebroad basins.Early phase extensionalstyle and basin formation indicate a ductilelithosphere, and this extensionoccurred during the climax of Paleogenemagmatic activity in this zone.Late phaseextensional style indicates a more brittle lithosphere,and this extensionfollowed a middle Miocenelull in volcanism.Regional uplift of about1 km appearsto haveaccompanied late phase extension, andrelatively minor volcanism has continued to thepresent.
    [Show full text]
  • Long-Term Volumetric Eruption Rates and Magma Budgets
    Article Geochemistry 3 Volume 7, Number 1 Geophysics XX Month 2006 GeosystemsG XXXXXX, doi:10.1029/2005GC001002 G ISSN: 1525-2027 AN ELECTRONIC JOURNAL OF THE EARTH SCIENCES Published by AGU and the Geochemical Society 1 Long-term volumetric eruption rates and magma budgets 2 Scott M. White 3 Department of Geological Sciences, University of South Carolina, 700 Sumter Street, Columbia, South Carolina 29208, 4 USA ([email protected]) 5 Joy A. Crisp 6 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA 7 ([email protected]) 8 Frank J. Spera 9 Department of Earth Science, University of California, Santa Barbara, Santa Barbara, California 93106, USA 10 ([email protected]) 11 [1] A global compilation of 170 time-averaged volumetric volcanic output rates (Qe) is evaluated in terms 12 of composition and petrotectonic setting to advance the understanding of long-term rates of magma 13 generation and eruption on Earth. Repose periods between successive eruptions at a given site and 4 14 intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>10 years) data 15 were available. More silicic compositions, rhyolites and andesites, have a more limited range of eruption À1 3 16 rates than basalts. Even when high Qe values contributed by flood basalts (9 ± 2 Â 10 km /yr) are 17 removed, there is a trend in decreasing average Qe with lava composition from basaltic eruptions (2.6 ± À2 3 À3 3 À3 3 18 1.0 Â 10 km /yr) to andesites (2.3 ± 0.8 Â 10 km /yr) and rhyolites (4.0 ± 1.4 Â 10 km /yr).
    [Show full text]
  • Facts and Hypotheses Regarding the Miocene–Holocene Jemez Lineament, New Mexico, Arizona and Colorado Fraser Goff and Shari A
    New Mexico Geological Society Downloaded from: https://nmgs.nmt.edu/publications/guidebooks/72 Facts and hypotheses regarding the Miocene–Holocene Jemez Lineament, New Mexico, Arizona and Colorado Fraser Goff and Shari A. Kelley, 2021, pp. 101-116 in: Geology of the Mount Taylor area, Frey, Bonnie A.; Kelley, Shari A.; Zeigler, Kate E.; McLemore, Virginia T.; Goff, Fraser; Ulmer-Scholle, Dana S., New Mexico Geological Society 72nd Annual Fall Field Conference Guidebook, 310 p. This is one of many related papers that were included in the 2021 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, Color Plates, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States.
    [Show full text]
  • Geophysical Study of the San Juan Mountains Batholith Complex, Southwestern Colorado
    Geophysical study of the San Juan Mountains batholith complex, southwestern Colorado Benjamin J. Drenth1,*, G. Randy Keller1, and Ren A. Thompson2 1ConocoPhillips School of Geology and Geophysics, 100 E. Boyd Street, University of Oklahoma, Norman, Oklahoma 73019, USA 2U.S. Geological Survey, MS 980, Federal Center, Denver, Colorado 80225, USA ABSTRACT contrast of the complex. Models show that coincident with the San Juan Mountains (Fig. 3). the thickness of the batholith complex var- This anomaly has been interpreted as the mani- One of the largest and most pronounced ies laterally to a signifi cant degree, with the festation of a low-density, upper crustal granitic gravity lows over North America is over the greatest thickness (~20 km) under the west- batholith complex that represents the plutonic rugged San Juan Mountains of southwest- ern SJVF, and lesser thicknesses (<10 km) roots of the SJVF (Plouff and Pakiser , 1972). ern Colorado (USA). The mountain range is under the eastern SJVF. The largest group of Whereas this interpretation remains essentially coincident with the San Juan volcanic fi eld nested calderas on the surface of the SJVF, unchallenged, new gravity data processing tech- (SJVF), the largest erosional remnant of a the central caldera cluster, is not correlated niques, digital elevation data, and constraints widespread mid-Cenozoic volcanic fi eld that with the thickest part of the batholith com- from seismic refraction studies (Prodehl and spanned much of the southern Rocky Moun- plex. This result is consistent with petrologic Pakiser , 1980) enable reassessment and improve- tains. A buried, low-density silicic batholith interpretations from recent studies that the ment of the previous model.
    [Show full text]
  • Miocene Stratigraphic Relations and Problems Between the Abiquiu, Los Pinos, and Tesuque Formations Near Ojo Caliente, Northern Espanola Basin S
    New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/35 Miocene stratigraphic relations and problems between the Abiquiu, Los Pinos, and Tesuque Formations near Ojo Caliente, northern Espanola Basin S. Judson May, 1984, pp. 129-135 in: Rio Grande Rift (Northern New Mexico), Baldridge, W. S.; Dickerson, P. W.; Riecker, R. E.; Zidek, J.; [eds.], New Mexico Geological Society 35th Annual Fall Field Conference Guidebook, 379 p. This is one of many related papers that were included in the 1984 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks.
    [Show full text]
  • Petrology and Physiographic Evolution of the Oeate Volcanic Field, North-Central New Mexico A
    Petrology and Physiographic Evolution of the Oeate Volcanic Field, North-Central New Mexico A. The Ocate Volcanic Field Description of Vdlcanic Vents and the Geochrondlogy, Petrography, and Whole-Rock Chemistry of Associated Flows B. Late Cenozoic Physiographic Evolution of the Ocate Volcanic Field U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1478 Petrology and Physiographic Evolution of the Ocate Volcanic Field, North-Central New Mexico A. The Ocate Volcanic Field Description of Volcanic Vents and the Geochronology, Petrography, and Whole-Rock Chemistry of Associated Flows By J. MICHAEL O'NEILL and HARALD H. MEHNERT B. Late Cenozoic Physiographic Evolution of the Ocate Volcanic Field By J. MICHAEL O'NEILL U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 147 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1988 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging-in-Publication Data Petrology and physiographic evolution of the Ocate volcanic field, north-central New Mexico. (U.S. Geological Survey professional paper ; 1478-A.B) Bibliography: p. Supt. of Docs, no.: I 19.16:1778A,B Contents: Pt. A. The Ocate volcanic field description of volcanic vents and the geochronology, petrography, and whole-rock chemistry of associated flows / by J. Michael O'Neill and Harald H. Mehnert Pt. B. Late Cenozoic physiographic evolution of the Ocate volcanic field / by J. Michael O'Neill. 1. Volcanic ash, tuff, etc. Sangre de Cristo Mountains (Colo. and N.M.) 2. Volcanic ash, tuff, etc. New Mexico. 3. Geology, Stratigraphic Cenozoic. I. O'Neill, J. Michael. Ocate volcanic field description of volcanic vents and the geochronology, petrography, and whole-rock chemistry of associated flows.
    [Show full text]
  • Mineral Resource Assessment of the Silver City I°X2° Quadrangle, New Mexico-Arizona
    UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY Mineral resource assessment of the Silver City I°x2° quadrangle, New Mexico-Arizona by D. H. Richter, W. N. Sharp, K. C. Watts, G. L. Raines, B. B. Houser, and D. P. Klein* Open-File Report 83-924 1983 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Denver, Colorado CONTENTS Page Introduction............................................................ 1 Known and possible mineral deposit types................................ 9 Copper............................................................. 9 Porphyry Cu (Mo) deposits..................................... 11 Cu-Zn-Fe replacement deposits................................. 17 Cu-Ag-Au (Pb-Zn) vein deposits................................ 18 Cu vein deposits.............................................. 19 Other deposit types........................................... 20 Resource summary.............................................. 21 Molybdenum......................................................... 22 Porphyry Cu (Mo) deposits..................................... 22 Stockwork Mo deposits......................................... 22 Resource summary.............................................. 24 Zinc and lead...................................................... 24 Zn, Zn-Pb, and Cu-Zn-Fe replacement deposits.................. 26 Zn-Pb (Cu-Ag-Au) vein and replacement deposits................ 28 Pb-Ag (Cu-Zn-Au) vein deposits...............................
    [Show full text]
  • Description of Map Units
    GEOLOGIC MAP OF THE LATIR VOLCANIC FIELD AND ADJACENT AREAS, NORTHERN NEW MEXICO By Peter W. Lipman and John C. Reed, Jr. 1989 DESCRIPTION OF MAP UNITS [Ages for Tertiary igneous rocks are based on potassium-argon (K-Ar) and fission-track (F-T) determinations by H. H. Mehnert and C. W. Naeser (Lipman and others, 1986), except where otherwise noted. Dates on Proterozoic igneous rocks are uranium-lead (U-Pb) determinations on zircon by S. A. Bowring (Bowring and others, 1984, and oral commun., 1985). Volcanic and plutonic rock names are in accord with the IUGS classification system, except that a few volcanic names (such as quartz latite) are used as defined by Lipman (1975) following historic regional usage. The Tertiary igneous rocks, other than the peralkaline rhyolites associated with the Questa caldera, constitute a high-K subalkaline suite similar to those of other Tertiary volcanic fields in the southern Rocky Mountains, but the modifiers called for by some classification schemes have been dropped for brevity: thus, a unit is called andesite, rather than alkali andesite or high-K andesite. Because many units were mapped on the basis of compositional affinities, map symbols were selected to emphasize composition more than geographic identifier: thus, all andesite symbols start with Ta; all quartz latites with Tq, and so forth.] SURFICIAL DEPOSITS ds Mine dumps (Holocene)—In and adjacent to the inactive open pit operation of Union Molycorp. Consist of angular blocks and finer debris, mainly from the Sulphur Gulch pluton Qal Alluvium (Holocene)—Silt, sand, gravel, and peaty material in valley bottoms.
    [Show full text]
  • Nevada, Las Vegas Las Vegas Nevidi.89154
    CENTER FOR VOLCANIC AND TECrONIC STUDIES1 DEPARTMENT OF GEOSCIENCE University of Nevada, Las Vegas Las Vegas Nevidi.89154 Report No. 56 ANNUAL REPORT for the Period 10/1/90 to 9/30/91 Submitted to the Nudlear Waste Project Office State of Nevada December 14, 1991 'Eugene L Smith-Principal hvestigator. Daniel Feuerbach-Research Associate Terry aaumann-Research Associate 0 9210020232 911231 PDR WASTE WM-11 PDR INTRODUCION The annual report of the Center for Volcanic and Tectonic Studies (CVTS) contains a series of papers, maps, reprints and theses that review the progress made by the CVF`S between October 1, 1990 and September 30, 1991. During this period CVIS staff focused on several topics that had direct relevance to volcanic hazards related to the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. These topics included: (1) The role of the mantle in controlling the location and composition of Pliocene- Holocene volcanism. (2) The nature of boundaries between compositionally different mantle domains. These domain boundaries may control the location of surface faults and volcanism. (3) The detailed geology of the Pliocene volcanic cones in Crater Flat (4) The detailed geology of bedrock to the east of Crater Flat on Yucca Mountain. (5) The structural controls and emplacement mechansims of Pliocene/Quaternary basaltic volcanic centers and dikes. (6) The study of young felsic volcanism in the southern Basin and Range. (7) Estimating the probability of disruption of the proposed repository by volcanic eruption (this topic is being studied by Dr. C Ho-UNLV). Activities CV1S presented papers at several professional meetings including (a) The Geological Society of America Cordilleran Section Meeting in San Francisco- March 25-27, 1991.
    [Show full text]