DOCSLIB.ORG

Alkaline Igneous Rocks of Magnet

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Alkaline Igneous Rocks of Magnet American Mineralogist, Volume 74, pages I I3-13 I, 1989 Alkaline igneousrocks of Magnet Cove, Arkansas: Metasomatizedijolite xenoliths from Diamond Jo quarry M.cnrA,J. K. Fr,onn, Mlr,cor,vr Ross 959 National Center,U.S. GeologicalSurvey, Reston, Viryinia 22092,U.5.4. Ansrucr Ijolite xenoliths occur in garnet-pseudoleucitesyenite that forms part of the outer ring of the Magnet Cove alkaline ring-dike complex. Xenoliths were collected from the Dia- mond Jo quarry located in the southern part of the complex. The xenoliths contain abun- dant diopside and Ti-rich andradite garnets and have been extensively metasomatized. Garnet-pseudoleucitesyenite and nepheline syenite are identified as possible sourcesof the volatile-rich fluids responsiblefor the metasomatismof the ijolite xenoliths. Residual, volatile-rich fluids from the ijolites may have also produced autometasomaticalteration before the ijolites were entrained as xenoliths in the garnet-pseudoleucitesyenite. Non- isotropic hydrogarnet,formed during metasomatism,contains up to 3.5 wto/oF. Aegirine, biotite, and melanite garnet, also formed during metasomatism, contain relatively high amounts of V andlor Ti, indicating that these elementswere transported by the metaso- matic fluids. Mineral compositions and geochemicaldata indicate that the ijolite xenoliths share many characteristicswith the intrusive ijolites that form the inner rings of the Magnet Cove complex. INrnolucrroN then consider the petrogeneticrelationships ofthe ijolite The Magnet Cove complex is an alkaline ring-dike xenoliths to the garnet ijolite and biotite-garnet ijolite complex that crops out in an area of approximately 12 that form the inner rings of the complex. km2 in Hot Spring County, Arkansas. The igneousrocks of the complex intrude deformed Paleozoic sedimentary Gnor,ocv rocks of the Ouachita Mountains. Biotite K-Ar and Rb- The rocks of Magnet Cove are host to numerous min- Sr agesobtained by Zartman (1977) indicate a Cretaceous eral species,and much of the early literature about the age of 95-102 Ma for the complex. Fission-track ages complex dealswith the minerals. The first detailed petro- (Eby, 1987) indicate two periods of igneous activity at graphic study and geologic map of Magnet Cove were Magnet Cove. The mean spheneage for the emplacement made by Williams (1891).Erickson and Blade(1963) re- of the silicaterock units is 101.4 + 1.0 Ma, whereasthe mapped the Magnet Cove complex and presenteda de- carbonatite,which occursin the core of the complex, was tailed lithologic and geochemical study of the igneous emplacedabout 5 m.y. later, as indicated by a mean apa- rocks and the surrounding country rocks. A generalized tite ageof 95.9 + 0.4 Ma. MagnetCove is one of several geologicmap of the complex basedon their detailed map alkaline igneous intrusions in central Arkansas. Morris is given in Figure l. Erickson and Blade (1963) concluded (1987)described this diversesuite ofrocks and discussed that phonolites and trachytes were intruded first, fol- possible petrologic relationships among them. One pur- lowed by jacupirangite and the syenitesofthe outer ring, pose of the current study of the igneousrocks from Mag- then the inner-ring ijolites, and finally carbonatite,which net Cove is to elucidate the relationships among the var- is found in the core of the complex. Erickson and Blade ious rock types and to compare the petrologic evolution (1963) proposedthat the igneousrocks of the Magnet of Magnet Cove to that of the other intrusions of the Cove complex are related by differentiation and fraction- Arkansas alkaline province. al crystallization of a residual, volatile-enriched phono- Metasomatism has played an important role in the pet- lite magma and that this magma was derived by fraction- rogenetichistory of these rocks. All of the samplesfrom al crystallization of an undersaturated olivine basalt the Diamond Jo quarry examinedthus far show extensive magma. replacementof primary magmatic minerals by secondary Exposuresof fresh rocks are scarcewithin the complex. phases.In this paper, which is the first ofa serieson the However, the opening of the Diamond Jo quarry in the Magnet Cove complex, we describeboth the primary and latter part ofthe l9th century to supply stone ballast for secondarymineral assemblagesfound in ijolite xenoliths the Hot Springs Railroad exposedmuch fresh unweath- from the garnet-pseudoleucitesyenite that forms part of ered rock. This quarry, which is located in the southern the outer syenite ring of the Magnet Cove complex. We part of the complex and within the outer syenitering (Fig. 0003-004x/89/ol024r I 3$02.00 I t3 rt4 FLOHR AND ROSS: METASOMATIZED IJOLITE XENOLITHS ffilacupirangite E '":;:;;i,'p he Ii ne f,l carnet-paeudo- leucite syeniie ffiPnonolirE, Trachyte Ifl carnet-biotite melteigita El Garnet ijotite Q eiorite-sarnet iiolite N rine-grainea ijolite I Carbonatite n Metagediments Fig. 1. Generalizedgeologic map of the Magnet Cove alkaline igneous complex, Hot Spring County, Arkansas, after Erickson and Blade (1963). The Diamond Jo quarry (solid triangle) is the sampling site of the ijolite xenoliths describedin this paper. The open and solid circles mark, respectively,the approximate sampling locations ofgarnet ijolites99423/7 and 85-13B-RSS;tfe open and solid squaresmark, respectively,the approximate sampling locations of biotite-garnet ijolites 99423/6 and 85- I 6-RSS. l), was mapped in detail by Owens and Howard (1989), Wrror,B-nocK coMPosrrroNs oF and a simplified version of part of their map is shown in M,LcnBr CovB rror,rrps Figure 2. The two rock types exposed on the walls of the Whole-rock major-, minor-, and trace-element com- quarry (originally are nepheline syenite mapped by Erick- positionsof ijolite xenoliths 5-DJ7, l-166, and l-143 son and Blade, 1963, as nepheline syenite pegmatite) and (Tables l, 2) reflect the modal diversity of the ijolite xe- garnet-pseudoleucite syenite. The contact between these nolith suite (Table 3). Included in Tables I and 2 are garnet-pseudoleu- two rock types is relatively sharp. The analysesofa garnetijolite and a biotite-garnet ijolite from cite syenite contains abundant xenoliths ofijolite, ranging the inner-ring ijolite for preliminary comparison with the from a few millimeters to 3 m in diameter. Xenoliths of ijolite xenoliths. Major- and minor-element composi- Stanley shale, now metamorphosed to hornfels, are also tions ofseveral additional ijolites from the inner ring are found within garnet-pseudoleucite the syenite. Prelimi- reportedby Erickson and Blade (1963, rheir Table l7). nary petrographic and electron-microprobe data from the Descriptions by Erickson and Blade indicate that these given Diamond Jo syenites and ijolite xenoliths were by samplesare similar to the inner-ring ijolites included in Ross (1984) (1985a, and Flohr and Ross 1985b). this study. Overall, the inner-ring ijolites are slightly more Mrrrrors oF ANALYSTs magnesianand contain significantly less F and CO, than the ijolite xenoliths. Mineral compositions were obtained by using an automated Of the three analyzedijolite xenoliths, l-143 contains AnL-sruqr electron microprobe operating at 15 kV with a beam the highest abundanceof clinopyroxene plus garnet and current of 0. I pA using either an 8- or 9-spectrometerconfigu- Fe, in Al, ration. Correction procedures of Bence and Albee (1968) and is enriched in Ti, and Ca and depleted Si, and alpha-factor modifications of Albee and Ray (1970) were used. Na comparedwith samplesl-166 and 5-DJ7. Xenolith During analysis of cancrinite and natrolite, the electron beam l-143 is alsoenriched in V, Y, andZr, comparedto sam- was rasteredover an area of 4 pm'?in order to minimize loss of ples 5-DJ7 and l-166. These are trace elementscom- Na due to mobilization. Data collection procedureswere out- monly found in notable concentrations in garnets from lined by McGee (1983, 1985),and backgroundswere calculated alkaline igneous rocks (e.g., Deer et al., 1982 and this using an interpolation routine describedby M. Mangan and J. study). Schnetzlerand Philpotts (1970) also reported that J. McGee (written comm., 1985).A variety of natural and syn- garnet has high distribution coefrcients for the heavy rare- thetic materials were used as standards.Traverses of clinopy- earth elements(HREEs) compared to other common rock- roxeneswere obtained using an ARL-EMx3-channel electron mi- forming minerals. In the ijolite xenoliths, as the abun- croprobe. X-ray single-crystaland powder-diffraction data were garnet from 100/oin obtained on selectedcrystals. Whole-rock analyses were ob- dance of increases 5-DJ7 to an av- - tainedon threeijolite xenoliths(l-166B, 1-143,and 5-DJ7)and erageof 37o/oin I I 4 3, the HREE concentrationincreases two inner-ringijolites (85-13B-RSSand 85-16-RSS)using ana- (Fig. 3). Garnet ijolite 85-I3B-RSS from the inner-ring lytical methodsdescribed by Baedecker(1987). ijolite has REE concentrations(Table 2) and a REE pat- tern similar to those of the ijolite xenoliths, whereasbio- much t Any use of trade names in this report is for descriptive pur- tite-garnetijolite 85-16-RSShas a more fraction- posesonly and does not imply endorsementby the U.S. Geo- ated REE pattern. Ijolites from the Fen complex, Norway logical Survey. (Mitchell and Brunfelt, 1975), Seabrook Lake, Ontario FLOHR AND ROSS: METASOMATIZED IJOLITE XENOLITHS ll5 mssr '2-D J 12 J:1-116 ^'{ffi3^}-5t7+s ^-e.99,11 6-DJ 10 n\ "t. 4-DJ 10 :r"-"?if#ii ;>9'$' TALUS ii;:ii:ili::\-G ,. 2-Dr7 a?,_ 01-DJ7 \_ri_!- Is-DJlO , l;':".o]-', DIAilOND JO OUARRY O CORE SAMPLE I BULK SAMPLE ./ coNTAcr Fig. 2. Geologic map of the Diamond Jo quarry, Magnet Ms, Stanley shale; f, fenite; ns, nepheline syenite xenoliths (?); Cove complex, after Owens and Howard (1989) indicating lo- gi, garnet ijolite xenoliths; ms, metamorphosed Stanley shale cations of all core and bulk samplesof ijolite xenoliths and sy- xenoliths; MCZ, mafic clot zone; CH and TH, crest and toe enitescollected. Samples 84-1-RSS-A and B are grab samples respectively,of highwall.
Load more

Recommended publications
  • Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest
    Chapter 21A. Summary of the Mineral Information Package for the Khanneshin Carbonatite Area of Interest Contribution by Robert D. Tucker, Harvey E. Belkin, Klaus J. Schulz, Stephen G. Peters, and Kim P. Buttleman Abstract The Khanneshin carbonatite is a deeply dissected igneous complex of Quaternary age that rises approximately 700 meters above the flat-lying Neogene sediments of the Registan Desert, Helmand Province, Afghanistan. The complex consists almost exclusively of carbonate-rich intrusive and extrusive igneous rocks, crudely circular in outline, with only three small hypabyssal plugs of leucite phonolite and leucitite outcropping in the southeastern part of the complex. The complex is broadly divisible into a central intrusive vent (or massif), approximately 4 kilometers in diameter, consisting of coarse-grained sövite and brecciated and agglomeratic barite-ankerite alvikite; a thin marginal zone (less than 1 kilometer wide) of outwardly dipping (5°–45°). Neogene sedimentary strata; and a peripheral apron of volcanic and volcaniclastic strata extending another 3–5 kilometers away from the central intrusive massif. Small satellitic intrusions of biotite-calcite carbonatite, no larger than 400 meters in diameter, crop out on the southern and southeastern margin of the central intrusive massif. In the 1970s several teams of Soviet geologists identified prospective areas of interest for uranium, phosphorus, and light rare earth element (LREE) mineralization in four regions of the carbonatite complex. High uranium concentrations are reported in two regions; the greatest concentrations are confined to silicified shear zones in sandy clay approximately 1.1 kilometers southwest of the peripheral part of the central vent. An area of phosphorus enrichment, primarily occurring in apatite, is present in coarse-grained agglomeratic alvikite, with abundant fenite xenoliths, approximately 750 meters south of the periphery of the central vent.
    [Show full text]
  • Nd, Pb and Sr Isotopic Data from the Napak Carbonatite-Nephelinite Centre, Eastern Uganda: an Example of Open-System Crystal Fractionation
    Contrib Mineral Petrol (1994) 115:356-366 Contributions tO Mineralogy and Petrology Springer-Verlag 1994 Nd, Pb and Sr isotopic data from the Napak carbonatite-nephelinite centre, eastern Uganda: an example of open-system crystal fractionation Antonio Simonetti and Keith Bell Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, Ottawa, Ontario K1S 5B6, Canada Received June 30, 1992 / Accepted May 25, 1993 Abstract. Nd, Pb and Sr isotopic data from nephelinite magmas cannot be in equilibrium with a lherzolitic mantle lavas from the Tertiary nephelinite-carbonatite complex source (Bultitude and Green 1968, 1971; Allen et al. 1975; of Napak, eastern Uganda, show large isotopic variations Merrill and Wyllie 1975), but are probably the products of that can only be attributed to open-system behaviour. small ( < 5%) degrees of partial melting of a carbonated Possible explanations of the data include mixing between (high C02/H20 ratio) peridotite or pyrolite at high pres- nephelinitic melts derived from an isotopically heterogen- sures (Brey and Green 1977; Brey 1978; Olafsson and eous mantle, or interaction between a HIMU melt and Eggler 1983; Wallace and Green 1988). Experimental re- mafic granulites. In both models crystal fractionation, sults are consistent with derivation of a primary involving olivine and clinopyroxene, played an important nephelinitic liquid from an amphibole peridotite at pres- role. Major element chemistry, textural evidence and iso- sures of 20 to 25 kbar (Olafsson and Eggler 1983; Eggler topic data from clinopyroxene phenocrysts from the ol- 1989). ivine-bearing nephelinites, suggest that the pyroxenes did The eastern branch of the East African Rift Valley not crystallize from their host liquids.
    [Show full text]
  • Mineralogy, Geochemistry and Petrology of a Pyrochlore-Bearing Carbonatite at Seabrook Lake, Ontario
    Mineralogy, Geochemistry and Petrology of a Pyrochlore-bearing Carbonatite at Seabrook Lake, Ontario by Myron John Osateriko B.Sc, University of British Columbia, 1965 A Thesis Submitted in Partial Fulfilment ' of the Requirements for the Degree of MASTER OF SCIENCE in the Department of GEOLOGY We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April, 1967 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that th3 Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Depa rtment The University of British Columbia Vancouver 8, Canada i ABSTRACT The Seabrook Lake carbonatite complex is one of the smallest of nine known carbonatite complexes in central Ontario. The complex, which is one-half square mile in area and pear- shaped in plan, consists of fenitized granite and breccia, mafic breccia, ijolite and related breccia, and carbonatite. The bulbous northern part of the complex consists of a plug-like core of carbonatite surrounded by mafic breccia and carbonatite dykes. The narrow southern part consists of ijolite and related breccia. Enveloping all of these rocks.is a fenitized aureole which grades outward to unaltered granite that underlies much of the surrounding area. The carbonatite is composed of calcite with the following minor mineral, in decreasing order of abundance: goethite, microcline, magnesioriebeckite-riebeckite, magnetite-ulvospinel, apatite, hematite, pyrite, albite, biotite, chlorite, pyrochlore, brookite, sphene, ferroan dolomite (ankerite?), aegirine, chalcopyrite, wollastonite and quartz.
    [Show full text]
  • Geology of the Cluggerfluorite Deposit
    Revista Brasileira de Geociências 17(3): 288-294, setembro de 1987 GEOLOGY OF THE CLUGGE RFLUORITE DEPOSIT. MATO PRETO. PARANÁ. BRAZIL ROBERT E. JENK INS n- ABSTRACT The Mato Preto fluorite deposite are located in the Ribeira River valley 80 km NNE from Curitiba, Paraná, Brazil. They consist of three known orebodies and numerous minar occurrences wi­ thin an area of about 15 km ê. Clugger, the largest dcposit, is a hydrothermnl replacemcnt and fracture-fil­ ling type in a brecciated and sheared contact zone among carbonatitc, nephellne syenitc, phonolite, and tin­ guaite of the Cretaceous-Paleocene age Mato Preto Igneous Complex. Fluorite occurs LS four subparallel but coalescing ore lenses which forro envelopes about dikes of phonolite-tinguaite and have strlke lengths of 250 m, aggregate thickness up to 80 m, and extend to at least 120 m in depth . Dikes and Ienses strike N50-55E and dip steeply to the northwest. Fluorite forms matrix replacemcnts and crosscutting veins in premineral and intermineral breccias adjacent to dikes. Fluorite mineralizatioo has been introduced in at least two pulses and is associated with barite-celestlre, apatite, rare earth minerais, and sulfides. Late explosive venting of the system has formed pipes of volcanic breccia with crackle breccia in ore adjacent. Fluorite along breakage planes is recrystallized into monomineralic veinlets. Mineralization is associated with fracture controlled epidote aJteration, but major silicification apparently predates ore. The c1ugger deposit was probably fonne d at low pressures and temperatures, possibly within a vent of a now-eroded Mato Preto volcano. RESUMO Os depósitos de Iluorita de Mato Preto situam-se no vale do Rio Ribeira, 80 km a NNE de Curitiba,Paraná.
    [Show full text]
  • Petrography and Engineering Properties of Igneous Rocks
    ENGINEERil~G MONOGRAPHS No. I United States Department of the Interior BUREAU OF RECLAMATION PETROGRAPIIY AND ENGINEERING· PROPER11ES OF IGNEOUS ROCKS hy Rit~bard C. 1\lielenz Denver, Colorado October 1948 95 cents (R.evised September 1961) United States Department of the Interior STEWART L. UDALL, Secretacy Bureau of Reclamation FLOYD E. DOMINY, Commissioner G~T BLOODGOOD, Assistant Commissioner and Chief Engineer Engineering Monograph No. 1 PETROGRAPHY AND ENGINEERING PROPERTIRES ·OF IGNEOUS RO<;:KS by Richard C. Mielenz Revised 1959. by William Y. Holland Head. Petrographic Laboratory Section Chemical Engineering Laboratory Branch Commissioner's Office. Denver Technical Infortnation Branch Denver Federal Center Denver, Colorado ENGINEERING MONOGRAPHS are published in limited editions for the technical staff of the Bureau of Reclamation and interested technical circles in Government and private agencies. Their purpose is to record devel­ opments, innovations, .and progress in the engineering and scientific techniques and practices that are employed in the planning, design, construction, and operation of Rec­ lamation structures and equipment. Copies 'may be obtained from the Bureau of Recla- · mation, Denver Federal Center, Denver, Colon.do, and Washington, D. C. Excavation and concreting of altered zones in rhyolite dike in the spillway foundation. Davis Damsite. Arizona-Nevada. Fl'ontispiece CONTENTS Page Introduction . 1 General Basis of Classification of Rocks . 1 Relation of the Petrographic Character to the Engineering Properties of Rocks . 3 Engineering J?roperties of Igneous Rocks ................................ :. 4 Plutonic Rocks . 4 Hypabyssal Rocks . 6 Volcanic Rocks..... 7 Application of Petrography to Engineering Problems of the Bureau of Reclamation . 8 A Mineralogic and Textural Classification of Igneous Rocks .
    [Show full text]
  • Alkaline Rock Complexes in the Wet Mountains Area, Custer and Fremont Counties, Colorado
    Alkaline Rock Complexes in the Wet Mountains Area, Custer and Fremont Counties, Colorado GEOLOGICAL SURVEY PROFESSIONAL PAPER 1269 Alkaline Rock Complexes in the Wet Mountains Area, Custer and Fremont Counties, Colorado By THEODORE J. ARMBRUSTMACHER GEOLOGICAL SURVEY PROFESSIONAL PAPER 1269 Geology and petrology of rocks of the McClure Mountain Complex, Gem Park Complex, and complex at Democrat Creek and associated alkaline rocks UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 UNITED STATES DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Armbrustmacher, Theodore J., 1946- Alkaline Rock complexes in the Wet Mountains area, Custer and Fremont Counties, Colorado. (Geological Survey Professional Paper 1269) Bibliography: 33 p. Supt. of Docs. No.: 119.16:1269 1. Alkalic igneous rocks. 2. Petrology Colorado Wet Mountains. I. Title. II. Series. QE462.A4A76 552'.3 82-600104 AACR2 CONTENTS Abstract ............................. 1 Ages of the complexes ..................... 14 Introduction ........................... 1 Geochemistry ........................... 15 Acknowledgments ........................ 1 Major elements ....................... 15 Geologic setting ......................... 2 Mafic-ultramafic rocks ................. 15 McClure Mountain Complex .................. 2 Leucocratic rocks ................... 16 Mafic-ultramafic rocks ................... 2 Mafic nepheline-clinopyroxene rocks ......... 19 Layered series ....................
    [Show full text]
  • Sr-Rich Apatite from the Dangzishan Leucitite-Ijolite Xenoliths (Heilongjiang Province): Mineralogy and Mantle-Fluid Metasomatism
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Springer - Publisher Connector Article Geology January 2011 Vol.56 No.1: 53–63 doi: 10.1007/s11434-010-4228-7 SPECIAL TOPICS: Sr-rich apatite from the Dangzishan leucitite-ijolite xenoliths (Heilongjiang Province): Mineralogy and mantle-fluid metasomatism ZHANG WenLan1*, SHAO JiAn2, WANG RuCheng1, XU XiSheng1, CHE XuDong1 & YANG YueHeng3 1 State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; 2 School of Earth and Space Sciences, Peking University, Beijing 100871, China; 3 State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Received April 28, 2010; accepted August 19, 2010 Abundant apatite grains with elevated SrO content were found in leucitite-ijolite xenoliths in the Dangzi Mountain, Heilongjiang Province. Morphological and mineralogical associations, and compositional analysis of the Sr-rich apatite, were carried out using an electron microprobe. Two principal types of apatite were distinguished. One type occurs as short-prismatic crystals with Sr-rich rims, while another type with acicular or finely columnar shapes constitutes Sr-rich apatite element maps and systematic quantitative analysis of apatite revealed great variations in SrO content (0.42%–26.79%). The calculated structural formula of the measured Sr-rich apatite is: (Ca3.15–4.963Sr0.019–1.510Ba0.00–0.030Na0.006–0.108REE0.106–0.153) (P2.84–3.028Si0.009–0.094)O12(F0.675–1.079, Cl0.000–0.256, OH0.084–0.297). Mineralogical textures of apatite implied a replacement mechanism for the Sr-rich apatite.
    [Show full text]
  • By Thomas P. Miller Open-File Report This Report Is Preliminary and Has
    454 UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PETROLOGY OF THE PLUTONIC ROCKS OF WEST-CENTRAL ALASKA By Thomas P. Miller Open-file report This report is preliminary and has not been edited or reviewed for conformity with Geological Survey standards GEOLOGY BKANCB TiSCHlUCAL DATA FILE ACKNOWLEDGMENTS This study was part of the U* S* Geological Survey's regional geologic mapping program in Alaska under the direction of William W* Patton, Jr., to whom I am indebted for many helpful discussions and criticisms* Professor Robert H* Corapton was my principal advisor during the study and I offer my sincere thanks for his many suggestions and helpful discussions* Professors William C* Luth and Richard H* Jahns read the manuscript in preliminary form and offered constructive suggestions* I thank Kenneth F. Fox, Jr., for many worthwhile discussions concerning the problems of alkaline rocks* Finally, I am especially grateful to my wife, Shirla, for her encouragement and inspiration throughout the course of this study* iii CONTENTS Page ACKNOWLEDGMENTS ...................... iii LIST OF TABLES ...................... vi LIST OF ILLUSTRATIONS ................... vii ABSTRACT ......................... ix INTRODUCTION ....................... 1 GENERAL REMARKS .................... -1 PREVIOUS WORK ..................... 3 PHYSIOGRAPHY ..................... 5 PLUTONIC ROCKS ...................... 7 CLASSIFICATION ..................... 9 ANALYTICAL DATA .................... 11 GEOLOGIC SETTING AND AGE OF THE PLUTONIC ROCKS .... 12 MID-CRETACEOUS
    [Show full text]
  • Rocks of Augusta, Rockingham Highland, and Bath Counties, Virginia
    COMMONWEALTH OF VIRGINIA DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT DIVISION OF MINERAL RESOURCES FIELD TRIP TO THE IGNEOUS ROCKS OF AUGUSTA, ROCKINGHAM HIGHLAND, AND BATH COUNTIES, VIRGINIA ROBERT W. JOHNSON, JR. CHARLES MILTON, AND JOHN M. DENNISON INFORMATION CIRCUI.AR I 6 VIRGINIA DIVISION OF MINERAL RESOURCES Jomes L. Colver Commissioner of Minerol Resources ond Stote Geologist CHARLOTTESVILLE, VIRGINIA 't971 COMMONWEALTH OF VIRGINIA DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT DIVISION OF MINERAL RESOURCES FIELD TRIP TO THE IGNEOUS ROCKS OF AUGUSTA, ROCKINGHAM, HIGHLAND, AND BATH COUNTIES, VIRGINIA ROBERT W. JOHNSON, JR. CHARLES MILTON, AND JOHN M. DENNISON INFORMATION CIRCULA,R I 6 VIRGINIA DIVISION OF MINERAL RESOURCES Jomes L. Colver Commissioner of Minerol Resources ond Stoie Geologisl CHARLOTTESVILLE, VI RGINIA 1971 CoMMoNWEALTH or VIncrr.rr.l DnrAnt1vrsNr or Puncnesss AND Suppl,y RTCHMoND !97L Portions of this publication may be quoted if credit is given to the Virginia Division of Mineral Resources. It is recomrnended that reference to this repor."t be made in the following form: Johnson, R, W., Jr., Milton, Charles, and Dennison, J. M., 1971, Field trip to the igneous rocks of Augusta, Rockingham, I{ighland, and Bath counties, Virginia: Virginia Division of Mineral Resources Information Circ. 16, 68 p. DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT Richmond, Virginia MARVIN M. SumnnLAND, Director Culnlps A. CnnrsropHERsEN, DeputA Director A. S. RlcnAL, JR., E*ecutiae Assi,stant BOARD Wrllrlu H. KrNc, Burkeville, Chuirman Wrr,r,rAu H. Sraxn,q.cEN, Alexandria, Vi,ce Chairman D. HnNny ALMoND, Richmond Ml.ron T. BENToN, Suffolk Josnps C. Canrnn, Jn., Richmond Aoor,r' U.
    [Show full text]
  • Major, Trace, and Rare-Earth Element Geochemistry of Nb-V Rich
    minerals Article Major, Trace, and Rare-Earth Element Geochemistry of Nb-V Rich Andradite-Schorlomite-Morimotoite Garnet from Ambadungar-Saidivasan Alkaline Carbonatite Complex, India: Implication for the Role of Hydrothermal Fluid-Induced Metasomatism Amiya K. Samal 1 , Rajesh K. Srivastava 1,* and Dewashish Upadhyay 2 1 Centre of Advanced Study in Geology, Banaras Hindu University, Varanasi 221005, India; [email protected] 2 Department of Geology and Geophysics, Indian Institute of Technology (IIT), Kharagpur 721 302, India; [email protected] * Correspondence: [email protected] or [email protected] Abstract: In situ major, trace and rare-earth element composition of Ti-rich garnets from Ambadungar- Saidivasan alkaline carbonatite complex (ASACC) are presented to constrain its likely genesis. The garnets are characterized by high andradite (42.7–57.3), schorolomite (22.0–31.0), and morimotoite (15.6–26.5) end members. No distinct chemical zonation is noticed except for minor variations in Ti content. The garnets are enriched in LREE (average 731 ppm) and relatively depleted in HREE Citation: Samal, A.K.; Srivastava, (average 186 ppm) and show an M-type first tetrad that leads to a convex upward pattern between R.K.; Upadhyay, D. Major, Trace, and Ce and Gd. Mildly positive to no Eu anomalies are observed (Eu/Eu* = 1.06–1.17). The REE patterns Rare-Earth Element Geochemistry of (LaN/YbN = 1.11–2.11) are similar to those of garnets from skarn deposits. The presence of tetrad Nb-V Rich Andradite-Schorlomite- effect in the LREE pattern suggests an active role of metasomatic processes involving hydrothermal Morimotoite Garnet from fluids during the growth of the garnets.
    [Show full text]
  • Alkaline Rocks of Samchampi-Samteran, District Karbi-Anglong, Assam, India
    Alkaline rocks of Samchampi-Samteran, District Karbi-Anglong, Assam, India S NAG 1, S K SENGUPTA 2, R K GAUR 1 and A ABSAR 1 1 Geological Survey of India, Lucknow 226 024, India 2 Geological Survey of India, Guwahati 781 021, India The Samchampi-Samteran alkaline igneous complex (SAC) is a near circular, plug-like body approximately 12 km 2 area and is emplaced into the Precambrian gneissic terrain of the Karbi Anglong district of Assam. The host rocks, which are exposed in immediate vicinity of the intrusion, comprise granite gneiss, migmatite, granodiorite, amphibolite, pegmatite and quartz veins. The SAC is composed of a wide variety of lithologies identified as syenitic fenite, magnetite -4- perovskite • apatite rock, alkali pyroxenite, ijolite-melteigite, carbonatite, nepheline syenite with leucocratic and mesocratic variants, phonolite, volcanic tuff, phosphatic rock and chert breccia. The magnetite -4- perovskite d: apatite rock was generated as a cumulus phase owing to the partitioning of Ti, Fe at a shallow level magma chamber (not evolved DI = O1). The highly alkaline hydrous fluid activity indicated by the presence of strongly alkalic minerals in carbonatites and associated alkaline rocks suggests that the composition of original melt was more alkalic than those now found and represent a silica undersaturated ultramafic rock of carbonated olivine-poor nephelinite which splits with falling temperature into two immiscible fractions--one ultimately crystallises as alkali pyroxenite/ijolite and the other as carbonatite. The spatial distribution of varied lithotypes of SAC and their genetic relationships suggests that the silicate and carbonate melts, produced through liquid immiscibility, during ascent generated into an array of lithotypes and also reaction with the country rocks by alkali emanations produced fenitic aureoles (nephelinisation process).
    [Show full text]
  • Highwood Mountains, Montana
    Bulletin No. 237 Series j ft ?e?criPtlv« Gwl°^ 43 , 90 \ D, Petrography and Mineralogy, 29 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY CHARLES D. WALCOTT, DIRECTOR PETROGRAPHY AND GEOLOGY OF THE IGNEOUS ROCKS OF THE HIGHWOOD MOUNTAINS, MONTANA BY LOUIS VALENTINE PIRSSO1ST WASHINGTON GOVERNMENT PRINTING OFFICE 1905 CONTENTS. Page. Letter of transmittal. .......................^............................ 11 Introduction__._.._._.____..--.-----_--.------..--.---...---- .-.------ 13 Bibliography ___.._______. __.__._____..---.._..-------.--.-..----..-..- 14 Chapter I. Geography and history ........----.-....-..--...-.----..----- 14 Location ..__._.._.._____..---..._------- --------------------. 14 Bibliography .. ...-.-...-..----.-_.._. ...... ....................:...... 15 Topography and geography .......................:.-.------.------.- 15 History................................................................. 16 Chapter II. Geology of the igneous stocks ................................ 20 Introductory ................................................... ------ 20 Highwood Peak stock....-.-.-..........-._.....--...-.---_.-.--._... 20 Character of the border contact.-..-.-.-..-..-.--...-----..-.--.- 22 Middle Peak stock.................................................. 23 Contact phenomena. -..---.......---------. -..-..-..--------.-.-- 23 Endomorphic contact phenomena ..........^..................... 24 East Peak stock....................................................... 24 Shonkin stock ...................... ....-'---.--...--".-...-.---.-.---.-
    [Show full text]