DOCSLIB.ORG

Appendix 3 Thin Section Descriptions of Basement Chips

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Appendix 3 Thin Section Descriptions of Basement Chips Appendix 3 Thin section descriptions of basement chips Mason Geoscience Pty Ltd Petrological Serv~cesfor the Minerals Exploration and Mining Industry ABN 64 140 231 481 ACN 063 539 686 Postal: PO Box 78 Glenside SA 5065 Australia Delivery: 141 Yarrabee Rd Greenhill SA 5140 Australia Ph: +61-8-8390-1507 Fax: +61-8-8390-1194 e-mail: [email protected] Petrographic Descriptions for Six Aircore Rock Samples from the Andrew Young Project, Northern Territory REPORT # 3076 CLIENT Mithril Resources Ltd ORDER NO Memo, P. Hill, 7 April 2005 CONTACT Mr Peter Hill REPORT BY Dr Douglas R Mason SIGNED for Mason Geoscience Pty Ltd DATE 21 April 2005 Petrographic Descriptions for Six Aircore Rock Samples from the Andrew Young Project, Northern Territory SUMMARY 1. Rock Samples A suite of 6 aircore rock samples from the Andrew Young Project (Northern Territory) has been studied using routine optical petrographic methods. 2. Brief Results A summary of rock names and mineralogy is provided in TABLE 1. Primary rock types - Intrusive igneous rocks are represented in all samples of the suite. - Two-pyroxene-biotite micro-diorite (AYAC04) is composed of plagioclase, orthopyroxene, clinopyroxene, biotite, and minor opaques and apatite. It represents the least-fractionated magma in the igneous rocks of this suite. It formed from a somewhat fractionated, K-rich, andesitic magma that may have a tholeiitic magmatic association. The fine grain size suggests that this rock formed in a relatively small intrusive body, or possibly the quickly-cooled margin of a larger intrusion. - Hornblende-biotite diorites (AYAC07, AYAC08) formed as coarse-grained rocks composed of plagioclase, pyroxene, hornblende, biotite, and minor quartz, K-feldspar, opaques and apatite. Early-formed pyroxene was completely replaced by deuteric actinolite. These rocks possibly represent cumulates from magma similar to that of AYAC04. - Mesocratic to felsic granitoids are represented by (from least-fractionated to most-fractionated) hornblende-biotite-pyroxene quartz monzodiorite (AYAC02), hornblende-biotite granodiorite (AYACOI), biotite monzogranite (AYACOG), and syenogranite ?dykelet (AYAC08). Through this sequence of rock types, quartz and K-feldspar increase and the ferromagnesian minerals decrease in abundance with pyroxene and then amphibole leaving the assemblage. - Genetic relationships are difficult to determine from a limited number of small aircore samples. However, the fine grain size, uniform mineral distribution and clean intergranular texture of the two- pyroxene-biotite micro-diorite is interpreted to indicate that this rock crystallised from a high-K andesitic magma of possible tholeiitic association. In the mesocratic to felsic granitoids, gradational mineralogical changes suggest that they are genetically related, but some petrographic observations suggest that these rocks may have formed by disequilibrium magma mingling processes: grain shapes tend to be subhedral to anhedral, inequigranular textures are common, large quartz and plagioclase grains are present in AYACOI, strong and complex compositional zoning is observed in large plagioclase prisms where present, poikilitic textures are commonly developed between K-feldspar and quartz, and a coarse felsic granitoid xenolith is present in AYACO6. The varied rock types and their textures, together with the indistinctly zoned aeromagnetic anomalies within ovoid intrusive bodies, allows the interpretation that these intrusions represent magma mingling zones that formed by uprise of variably mingled mafic and felsic magmas from deeper magma chambers. Examples of this phenomenon are discussed in the literature (eg MacColl 1964; Vernon et al. 1988; Collins 1998). Hoatson and Stewart (2001, p.16) suggest that magma mingling was important in the Andrew Young Hills intrusion of their study. The observed rock types in the present suite do not appear to represent a layered mafic- ultramafic intrusion. Mason Geoscience Pty Ltd Report #3076 Mithril Resources Ltd Alteration - Selective alteration of pyroxene by actinolite and plagioclase by trace epidote is observed in some samples. These modifications of the primary mineralogy are considered to have formed in response to deuteric alteration during final cooling. - Lack of metamorphic effects suggests that these rocks have not been modified by a significant metamorphic event. Mason Geoscience Pty Ltd Report #3076 Mithril Resources Ltd TABLE 1: SUMMARY OF ROCK NAMES AND MINERALOGY SAMPLE ROCK NAME MINERALOGY* Primary** Alteration Veins Weathering AYACOI Weakly weathered, hornblende-biotite Pla, Kf, qtz, hbl, bio, Cla granodiorite opq, apa, zir AYAC02 Hornblende-biotite-pyroxene quartz Pla, qtz, Kf, cpx, hbl, monzodiorite bio, opq, apa, zir AYAC04 Two-pyroxene-biotite micro-diorite Pla, opx, cpx, bio, opq, - qtz, spa AYACO6 Partly weathered, xenolithic biotite monzogranite: Biotite monzogranite Kf, pla, qtz, bio, opq, - Cla apa, zir Felsic granitoid xenolith Pla, hbl, Kf, qtz Cla AYAC07 Partly weathered, hornblende-biotite Pla, bio, hbl, qtz, opq, Act, epi Cla diorite a Pa AYAC08 Partly weathered, hornblende-biotite Pla, hbl, bio, qtz, Kf, Act, epi Cla quartz diorite OPq, aPa Partly weathered, micro-biotite Qtz, Kf, pla, bio, opq Epi Cla, goe monzogranite Syenogranite ?dykelet in micro-biotite Kf, qtz, pla, bio, opq, Epi Cla, goe monzogranite SPn NOTES *: Minerals are listed in each paragenesis according to approximate decreasing abundance. **: Only primary minerals currently present in the rock are listed. Others may have been present, but are altered Mineral abbreviations Act = actinolite; apa = apatite; bio = biotite; cla = undifferentiated clays (possibly ?illitic); cpx = clinopyroxene (augite); epi = epidote; goe = goethite; hbl = hornblende; Kf = K-feldspar (microcline); opq = undifferentiated opaques (mainly ?Fe-Ti oxides); opx = orthopyroxene (hypersthene); pla = plagioclase; qtz = quartz; spn = sphene; zir = zircon. Mason Geoscience Pty Ltd Report #3076 Mithril Resources Ltd 1 INTRODUCTION A suite of 6 aircore rock samples was provided by Mr Peter Hill (Mithril Resources Ltd, Dulwich, South Australia) during a visit to Mason Geoscience on 7 April 2005. Background information was provided, indicating that the samples originate from the Andrew Young Project in the Northern Territory. An aircore drilling program had tested a large circular magnetic anomaly near the Andrew Young Hills. The body does not crop out and there are no other drill holes in the area. It is thought that the body might be a compositionally zoned gabbroic intrusion. The drill hole locations were indicated on a magnetic image of the area, and photocopied excerpts were provided from Hoatson and Stewart (2001). Particular requests were to prepare a thin section and petrographic description for each sample, using brief descriptions where repetition of rock types occurs. Excerpts from this report were provided by email to Mr Hill on 20 April 2005. This report contains the full results of this work. 2 METHODS At Mason Geoscience Pty Ltd conventional transmitted polarised light microscopy was used to prepare the routine petrographic descriptions. Paragenetic stages of development of each rock are indicated in the mineral modal list, where each mineral is assigned to a numerical paragenesis (paragenesis 1 is earliest; paragenesis 2 overprints 1; paragenesis 3 overprints both 2 and 1; etc). The paragenetic stages display relative timing within each sample, and are not meant to be directly equated between samples although this may be correct for some samples. Igneous rock types were classified according to the IUGS scheme (Streckeisen 1976). 3 PETROGRAPHIC DESCRIPTIONS The petrographic descriptions are provided in the following pages. Mason Geoscience Pty Ltd Report #3076 Mithril Resources Ltd SAMPLE : AYACOI (Andrew Young Hills, Northern Territory) SECTION NO : AYACOI HAND SPECIMEN: The aircore rock fragment represents a massive, fine- to medium-grained crystalline rock of mesocratic appearance, with scattered large equant quartz grains. ROCK NAME : Weakly weathered, hornblende-biotite granodiorite PETROGRAPHY : A visual estimate of the modal mineral abundances gives the following: I Vol % Origin I Plagioclase lgneous 1 K-feldspar (microcline) lgneous 1 Quartz lgneous 1 Hornblende lgneous 1 Biotite lgneous 1 Opaques (mainly ?Fe-Ti oxides) lgneous 1 Apatite lgneous 1 Zircon lgneous 1 Clays Weathering 2 In thin section, this sample displays a massive inequigranular granitoid texture, modified only by weak selective weathering. Plagioclase is abundant, forming small randomly oriented subhedral twinned prisms -0.5 mm long, and uncommon larger blocky twinned prisms -1-2 mm in size. The plagioclase is quite fresh. K-feldspar is moderately abundant, forming anhedral angular grains scattered through the rock, in granular relationship with similarly sized clear quartz grains. Well-developed 'tartan' twinning in the K-feldspar confirms it is microcline. Larger optically continuous pools of K-feldspar enclose small ovoid grains of optically continuous quartz. Large anhedral grains of polycrystalline quartz are sparsely scattered through the rock. Hornblende is present in significant amount as anhedral pleochroic green grains mostly -0.4-0.6 mm in size. Biotite occurs in comparable amount, forming randomly oriented platy flakes pleochroic from reddish tan brown to very pale yellow (ie relatively reduced composition). Opaques occur in minor amount as equant to anhedral or lobate grains. They most likely are Fe-Ti
Load more

Recommended publications
  • Petrogenesis of Highly Fractionated I-Type Peraluminous Granites: La Pedriza Pluton (Spanish Central System)
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by EPrints Complutense Geologica Acta, Vol.8, Nº 2, June 2010, 131-149 DOI: 10.1344/105.000001527 Available online at www.geologica-acta.com Petrogenesis of highly fractionated I-type peraluminous granites: La Pedriza pluton (Spanish Central System) 1 1 CECILIA PÉREZ-SOBA and CARLOS VILLASECA 1 Department of Petrology and Geochemistry, Universidad Complutense de Madrid- Instituto de Geología Económica (C.S.I.C.) c/ José Antonio Novais, 2, 28040 Madrid, Spain. Pérez-Soba E.mail: [email protected] ABSTRACT The La Pedriza pluton stands out as the most extensively fractionated granite (Rb < 629; Sr < 2 and Ba < 2 ppm) of the Spanish Central System Batholith. These granites show a strong enrichment in some rare metal contents (Nb = 44, Y = 136, Yb = 10.7, U = 17, Ta = 7, Sc = 15 ppm). The petrography and geochemistry (including Sr- Nd isotopes) reveal that the pluton is composed of at least four units. These are classified as I-type peraluminous leucogranites (A/CNK=1.03-1.17), P-poor (P2O5<0.2 wt%) and Na2O-rich (< 4.24 wt%) exhibiting differences in their HFSE and REE contents and εNd compositions. Moreover, the units of the La Pedriza granite display different trends of fractional crystallization. REE spectra of the two most fractionated units suggest the involvement of a fluorine-rich melt in the last stages favouring the crystallization of xenotime and niobotantalates. Intermediate meta-igneous granulite protoliths are proposed as source rocks. The most evolved units of the La Pedriza pluton show chemical features convergent to A-type granites; these are explained by extensive fractional crystallization of a P-poor, I-type granite magma.
    [Show full text]
  • Joshua Tree U.S
    National Park Service Joshua Tree U.S. Department of the Interior Joshua Tree National Park Geology Tour Road an 18-mile motor tour This is your guide through some of the most fascinating landscape in Joshua Tree National Park. The numbers appearing in the left margin correspond with markers along the tour route. Mileage starts at the intersection of Geology Tour Road and the main park road. The 16 stops along the 18-mile tour will require approximately two hours and will return you to this point. Soft sand and steep grades make it a challenging trip. Recreational vehicles are not recommended, but two- wheel sedans and trucks may access the route as far as Squaw Tank, marker number 9. After Squaw Tank the road gets rougher and is only recommended for White Tank 4-wheel-drive vehicles. Monzogranite and Pinto Gneiss Lost Horse Valley Please help us protect this natural environment so that others may enjoy it as you have. Geology and the The face of Earth at any one time represents only a exposed two rock bodies originally formed deep below Park fleeting phase of a very long and dynamic history. Earth’s surface: the 1.7-billion-year-old Pinto gneiss Geologic change goes on all around us, all the time. and the 85-million-year-old White Tank monzogranite, The way the landscape looks today is a result of the which intruded the gneiss as molten magma. geologic processes that have occurred throughout most of Earth’s 4.5-billion-year past. Many other geologic events occurred in this area, however the rock record has been lost through The landscape we see today in Joshua Tree National erosion.
    [Show full text]
  • Using Δ O of Zircon to Determine the Magmatic Evolution and Degrees Of
    Using 18O of zircon to determine the magmatic evolution and degrees of contamination in Peggy’s Cove monzogranite, Halifax pluton, Nova Scotia Kendra Murray Senior Integrative Exercise March 9, 2007 Submitted in partial fulfillment of the requirements for a Bachelor of Arts degree from Carleton College, Northfield, Minnesota Table of Contents Abstract Introduction……………………………………………………………………...... 1 Geologic Setting………………………………………………………………....... 5 Halifax Pluton Analytical Methods……………………………………………………………….. 13 Petrography……………………………………………………………………….. 14 Igneous Textures Cathodoluminescence Results……………………………………………………………………………... 17 Whole Rock Geochemistry 18O Zircon Discussion…………………………………………………………………………. 26 Oxygen Isotopes Implications for Post-magmatic Isotope Exchange Conclusions………………………………………………………………………... 34 Acknowledgements……………………………………………………………...... 35 References Cited………………………………………………………………….. 36 Using 18O of zircon to determine the magmatic evolution and degrees of contamination in Peggy’s Cove monzogranite, Halifax pluton, Nova Scotia Kendra Murray Carleton College Senior Integrative Exercise March 9, 2007 Advisors: Cameron Davidson, Carleton College Jade Star Lackey, The College of Wooster Abstract The Halifax pluton is the largest discrete granitoid body of the Late Devonian peraluminous South Mountain batholith complex associated with the Acadian Orogeny. We report the first 18O values in zircon from the Peggy’s Cove monzogranite, a unit on the outer edge of the Halifax pluton, which vary from 7.71-8.26‰. Small, but systematic E-W regional variation in 18O values suggests heterogeneous magmatic contamination, and field observations of meter-scale enclaves agree with a model of magma mingling and heterogeneous mixing. These data agree with previous whole rock and isotope studies that indicate a dominantly sedimentary source rock for the South Mountain batholith. The data also show that the monzogranite is not in isotopic equilibrium with zircon, perhaps due to late-stage isotopic exchange with a high 18O reservoir.
    [Show full text]
  • 012 28915Ns130715 10
    Nature and Science 2015;13(7) http://www.sciencepub.net/nature GPetrology, Geochemistry and Fractional Modelling Of El-Gidami Neoproterozoic Granitic Rocks, Central Eastern Desert, Egypt. El Mezayen A.M1., Heikal M.A1., Omar, S. A2,. El-Feky M.G2., Lasheen S.R1. 1Geologogy Department, Faculty of Science, Al Azher University, Egypt. 2Nuclear Material Authority, Egypt. [email protected] Abstract: El-Gidami area lies in the Central Eastern Desert of Egypt. This area is composedofamphibolite, oldergranites (OG) and younger granites (YG). The OG is of tonalitic to granodioritic composition with peraluminous nature whereas the Y Ggranitevaries in composition from monzogranite to syenogranite with calc alkaline nature. The OG are enriched in both Sr and Ba but depleted in Rb, whereas the Y Ghave lower Sr and Ba and higher Rb. Both OG and YG are poor in REE. Fractional crystallization and mass balance modeling are used to calculate the amount of sum square of the residuals (∑R2). The calculation has been performed for granodiorite and the younger granite (monzogranite) of Gabal El-Gidami as one separate system, then granodiorite and the younger granite (syenogranite) of Gabal El-Gidami as another separate system that gives a small value of the residuals which indicates a best fit ∑R2 (0.006 &0.007 respectively). [El Mezayen A.M., Heikal M.A., Omar, S. A. El-Feky M.G., Lasheen S.R. Petrology, Geochemistry and Fractional Modelling Of El-Gidami Neoproterozoic Granitic Rocks, Central Eastern Desert, Egypt. Nat Sci 2015;13(7):102-114]. (ISSN: 1545-0740). http://www.sciencepub.net/nature. 12 Key words: El-Gidami, Geochemistry, Fractional modelling and mass balance.
    [Show full text]
  • Geologic Map of the Sandpoint 30' X 60' Quadrangle, Idaho And
    Geologic Map of the Sandpoint 30´ x 60´ Quadrangle, Idaho and Montana, and the Idaho Part of the Chewelah 30´ x 60´ Quadrangle Mapped and Compiled by Reed S. Lewis, Russell F. Burmester, Roy M. Breckenridge, Mark D. McFaddan, and William M. Phillips Idaho Geological Survey Third Floor, Morrill Hall University of Idaho Digital Web Map 189 Moscow, Idaho 83844-3014 2020 Cover photo: View southwest over river delta (Qad) built by the Clark Fork into Lake Pend Oreille. Geologic Map of the Sandpoint 30´ x 60´ Quadrangle, Idaho and Montana, and the Idaho Part of the Chewelah 30´ x 60´ Quadrangle Mapped and Compiled by Reed S. Lewis, Russell F. Burmester, Roy M. Breckenridge, Mark D. McFaddan, and William M. Phillips 2020 INTRODUCTION o Geology depicted on this map is based partly on 48 30' 9 2 7 previous 15´ mapping by Harrison and Jobin (1963, 11 1965) and on unpublished 7 ½´ mapping by F. K. Miller 4 and others. Figures 1, 2, and 3 are index maps showing 10 the area covered by our STATEMAP-supported work 2 and mapping by previous workers. Remapping of 11 3 bedrock in 2003-2008 applied some different unit 7 definitions and contact placements for consistency with 1 M o n t a n a recent mapping to the south. We also made additional 2 subdivisions within the Prichard Formation based on a s h i n g t i o n W 9 6 mapping to the north by Cominco geologists (Michael 8 5 Zientek, written commun., 2003). Overall, the bedrock 9 areas of the eastern part of the map differ little from 48 o Harrison and Jobin (1963, 1965); visual differences are 117 o 116 o attributable to slight changes in placement of contacts 1.
    [Show full text]
  • Precambrian Research Quantifying Rates of Dome-And-Keel Formation in the Barberton Granitoid-Greenstone Belt, South Africa
    Precambrian Research 177 (2010) 199–211 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Quantifying rates of dome-and-keel formation in the Barberton granitoid-greenstone belt, South Africa Cristiano Lana a,∗, Eric Tohver b, Peter Cawood b a Department of Geology, Geography and Environmental Studies, Stellenbosch University, Cnr Ryneveld and Merriman Streets, Geology Building, Private Bag XI, Matieland 7602, Stellenbosch, WC, South Africa b School of Earth and Geographical Sciences, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia article info abstract Article history: The Barberton granitoid-greenstone belt is a classic dome-and-keel province, characterized by kilometer- Received 24 October 2008 scale gneiss domes and elongate keels of largely folded supracrustal rocks. Combined U–Pb SHRIMP data Received in revised form and structural mapping demonstrate that the geometry of the Barberton belt reflects events that occurred 20 November 2009 over ∼30 million year interval, from ca. 3230 and 3203 Ma. Early deformation with NW–SE shortening in Accepted 3 December 2009 the upper crust was accompanied by emplacement of tonalite-trondhjemite-granodiorite TTG magmas at 3234 ± 12 and 3226 ± 9 Ma. Much of the structural grain of the greenstone belt relates to a long episode of post-orogenic extension, with NE-directed extension in the lower crust leading to exhumation of Keywords: Dome-and-keel high-grade gneisses in the southern Barberton terrane. Advective heat transfer during emplacement Barberton of kilometer-scale (TTG) plutons around the margins of the greenstone belt facilitated the infolding of Archean tectonics the relatively denser and colder greenstone sequence.
    [Show full text]
  • Petrogenesis of Rare-Metal Granites from Depleted Crustal Sources: an Example from the Cenozoic of Western Utah, U.S.A
    Petrogenesis of rare-metal granites from depleted crustal sources: an example from the Cenozoic of western Utah, U.S.A. ERIC H. CHRISTIANSEN* � Department of Geology, University of Iowa JOHN S. STUCK LESS U.S. Geological Survey . Denver, Colorado MYRA J. FUNKHOUSER-MAROLF and KRISTY H. HOWELL Department of Geology, University of Iowa . Iowa City, Iowa ABSTRACT and the products of incremental episodes of equilibrium crys­ Cenozoic magmatism of the eastern Great Basin, western. tallization (Group 2) accumulated on the walls of the magma U.S.A., produced a number of aluminous anorogenic (A-type) chamber. rhyolites, many of which contain topaz and are rich in U, Be, The genesis of the parental magma probably involved par­ . Rb and F; such rhyolites could be called rare-metal rhyolites. tial melting of granulites in the lower crust as the result of the A small granite pluton tlu!t is chemically and temporally equi�a­ decomposition ofF-rich biotite. From trace element models of lent to these rhyolites is preserved in the Sheeprock Mountall1s batch partial melting, small degrees of melting (2.5 % to 15 %) of west-central Utah. The pluton ranges from biotite mon­ are inferred to be important in the generation of the parental zogranite to biotite-muscovite syenogranite (lUGS). Ilmenite, magma; subsequent strong fractionation occurred in the upper magnetite, apatite, zircon, monazite, fluorite, beryl, and thorite crust. A geochemically anomalous source is not required for are magmatic accessory minerals; in a few specimens topaz and the generation of granites like the Sheeprock granite that are muscovite are post-magmatic accessories.
    [Show full text]
  • The Geology of the Archaean Granitoid - Greenstone Teerane in the Vicinity of Three Sisters, Barberton Greenstone Belt
    THE GEOLOGY OF THE ARCHAEAN GRANITOID - GREENSTONE TEERANE IN THE VICINITY OF THREE SISTERS, BARBERTON GREENSTONE BELT Ernst Alfred Kohler j A thesis submitted to the Faculty of Science, University o f the Witwatersrand, Johannesburg, for the degree o f Doctor o f Philosophy Johannesburg, 1994 ABSTRACT This thesis provides a comprehensive account of the geology of the Archaean granitoid-greenstone terrane centred around Three Sisters in the northeastern sector of the Barberton Mountain Land. The supracrustal succession in the region comprises a diverse variety of altered volcanic and sedimentary rock types that have been correlated with the principal lithostratigraphic units of the Barberton greenstone belt (BGB) as fellows: 1) schistose basic and ultrabasic lithologies correlated with the Theespruit Formation of the Gnverwacht Group are mainly developed in a narrow unit fringing the northern margin of the BGB; 2) ferruginous shale greywacke - banded iron-formation assemblages correlated with the Jheba and Belvue Road Formations constitute the dominant Fig Tree Group imks in the region. A sec «ence or silicic » .-stavolcaniclastic rocks, now altered to a variety of micaceous schists, occurs west, north ar.a northeast of Three Sisters. Viljoen and Viljoen (1970) cc rrela ted these schists ith the Theespruit Formation. In this study, the schists have been assigned'to a new lithostratigraphic unit, referred to as the Bien Venue Formation, which forms the uppermost formation of the Fig Tree Group in the northeastern part of the BGB. Isotopic studies on zircons indicate that the schists have an age of 3256 ± Ma, which is some 200 Ma younger titan the most recent age estimates for the lower portions of the Gnverwacht Group.
    [Show full text]
  • Geology, Petrography, Geochemistry, and Geochronology of the Old
    GEOLOGY, PETROGRAPHY, GEOCHEMISTRY AND GEOCHRONOLOGY OF THE OLD GRANITE BATHOLITH BETWEEN QENA AND SAFAGA, EASTERN DESERT, EGYPT . MY. ATTAWIYA*, L . M . NOSSAIR*, A.I. RAGAB** AND S . A . EL DEBEIKY* • Nuclear Materials Authority, Cairo. ** Am Shams University, Cairo. EG9601817 ABSTRACT A suite of tonalite-granodiorite and monzogranite forms a huge old granite batholith between Qena and Safaga, Eastern Desert, Egypt. The batholith was originated from the fractional crystallization of a peraluminous calk-alkaline magma rich in silica and low in potassium. It is developed in an island arc tectonic setting . The rocks forming the batholith are depleted in both U & Th elements . However a gradual increase in these two elements from tonalite to monzogranite was observed . Zircon and sphene are responsible for for U & Th contents in these rocks . Rb/Sr isotopic age determination reported an age of 632.8 ± 4.6 Ma. for these old granitoids. The low initial 87Sr / 86Sr ratio in these rocks suggested there mantle origin or derivation from lower crustal materials with low Rb/Sr ratios and short residence in the crust. INTRODUCTION Along Qena-Safaga asphaltic road, Eastern Desert of Egypt, the old granitoids form a huge batholith covering an area of several hundreds of square kilometers (Fig. 1). These rocks were subjected to several geologic studies; El Gaby and Habib 0) referred to this old granitoids as syn-to late-orogenic calc-alkaline series. Ragab (2) considered these rocks as arc-granitoids from the protocrust of the magmatic arcs in the pre-collision stage. Abdel-Rahman and Martin (3) and Abdel-Rahman (4) mentioned that the old granitoids were developed from the partial melting of the subducted oceanic crust during the early stage of the Pan-African Orogeny.
    [Show full text]
  • Use of Zircon Typology for the Study of Some Granites from the Massif Central, France
    RENDlCQNTI DEUA SOCIET). ITAllANA DI MlNERALOGIA E PETNOLOGIA, 1988, \bI. 4).2. pp. 46H76 Use of zircon typology for the study of some granites from the Massif Central, France BERNARD BARBARlN* Univcrsiti Blaise Pascal et U.A. 10 C.N.R.S., Departement de G~IOIie et Mi~ralogie, " rue Kenler, F·6}O}S Clermont·Ferrand Cedex (France) ABsn.J.cr. - The zircon morpholosy method is • arranged in two main groups: one is of hybrid convenient, reli.ble, and. ec;onomical tool in granite origin, and the other of crusta! origin (DIDIER petrology. 11 gives useful information on the tempenturC', water rontent, .nd chemistry of the magma and LAMEYRE, 1969; DlDIER et al., 1982). In and reasonably precise indications of the nature and many plutons, the largely dominant origin of the material. monzogranite and granocliorite types are Use of the zircon morphology method facilitates commonly K-fe1dspar porphyritic and biodte­ solution of several kinds of regional problems related to the petrology r:i granites in the Massif Central, rich. When these granites are neither France. This method commonly is determinant or hornblende.bearing nor muscovite· or represents an additional constraint in comparing granites cordierite-bearing, petrographic and eJl:poscd in the same llI'ea or eoclaves of granites in geochemical data are often insufficient to granitic hosts. Study of zircons can also provide a general outline of the magmatism in a large granitic arca such compare the closely-spaced units and to define IS the Forez horst, or a definition cl magmatic zoning their origin. The typologic study of zircon in a fragment of the Hercynian chain such as the entire populations is commonly determinant in the Massif Central.
    [Show full text]
  • The Rare-Element.Enrighed Monzogranite
    8L7 TTrcC anadian M ineralo gi st Vol. 33,pp. 817-833(1995) THERARE-ELEMENT.ENRIGHED MONZOGRANITE - PEGMATITE - OUARTZVEIN SYSTEMSIN THE PREISSAC-LACORNEBAf,HOLITH. OUEBEC. II. GEOCHEMISTRYAND PETROGENESIS T}IOMAS MI"ILIA, ANTI{ONY E. WILLIAMS-JONES, SCOTTA. WOOD1AND MICHEL BOILY2 Deparfinentof Eanhand Planetary Sciences, McGiIl University,3450 University Street, Montreql, Qucbec H3A 2A7 ABSTRACT The ArcheanPreissac-Iacorne batholith in northwestemQu6bec includes four felsic plutons (Preissac,Moly Hill, Lamotte, Lacorne),which are zonedfrom biotite to muscovitemonzogranite. The l.amotte and Lacorneplutons are associatedspatially with rare-elementpepatites, whereaspegmatites are absentfrom the Moly Hill pluton and do not contain rare-element minerals in the Preissacpluton. The mre-elementpegmatites are zonally distributed from beryl-bearing in the plutons to spodumene-bearingin the county rocks. Molybenite-bearingquartz veins are associatedwith all four plutons, and in the case of the l,amotte andLacorne plutons, occur beyond fhe spodumenepegmatites. Dikes of molybdenite-bearingalbitite occurnort! of the Lacome.pluton.All the plutons are weakly to moderatelyperaluminous (A/CNK: 1.0-1.3) and exhibit a compositional continuumin major- andtrace-element contents from biotite to muscovitenonzogranite. This conpositional continuumextends to the rare-elementpegnatites, indicating that the monzogranitesand pegmatitesare comagmatic.The chemisty of the pegmatitessuggests that the!"utiderwent further evolution from beryl-bearingto spodumene-bearingvarieties.
    [Show full text]
  • Petrology of the Lyngdal Granodiorite (Southern Norway) and the Role of Fractional Crystallization in the Genesis of Proterozoic Rapakivi-Like Granites
    Petrology of the Lyngdal granodiorite (Southern Norway) and the role of fractional crystallization in the genesis of Proterozoic rapakivi-like granites. Michel Bogaerts, Bruno Scaillet, Jean-Paul Liégeois, Jacqueline Vander Auwera To cite this version: Michel Bogaerts, Bruno Scaillet, Jean-Paul Liégeois, Jacqueline Vander Auwera. Petrology of the Lyn- gdal granodiorite (Southern Norway) and the role of fractional crystallization in the genesis of Protero- zoic rapakivi-like granites.. Precambrian Research, Elsevier, 2003, 124, pp.149-184. 10.1016/S0301- 9268(03)00085-8. hal-00069475 HAL Id: hal-00069475 https://hal-insu.archives-ouvertes.fr/hal-00069475 Submitted on 18 May 2006 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Petrology and geochemistry of the Lyngdal granodiorite (Southern Norway) and the role of fractional crystallisation in the genesis of Proterozoic ferro-potassic A-type granites Michel Bogaerts,a, Bruno Scailletb, Jean-Paul Liégeoisc and Jacqueline Vander Auweraa a L.A. Géologie, Pétrologie et Géochimie (B20), Université de Liège, Sart Tilman, Liege 4000, Belgium bISTO-CNRS, 1A rue de la Férollerie, 45071, Orléans cédex 2, France c Isotope Geology, Africa Museum, B-3080, Tervuren, Belgium Abstract In south-western Norway, the Sveconorwegian orogenic thickening (1024–970 Ma) is followed by an important post-collisional magmatism (950–930 Ma), divided in two suites (Vander Auwera et al., 2003): the Anorthosite–Mangerite–Charnockite suite (AMC suite) and the Hornblende–Biotite Granitoids suite (HBG suite).
    [Show full text]