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The Uyaijah Ring Structure, Kingdom of Saudi Arabia

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The Uyaijah Ring Structure, Kingdom of Saudi Arabia The Uyaijah Ring Structure, Kingdom of Saudi Arabia G E 0 L 0 G I C A L S U R V E Y P R 0 FE S S I 0 N A L P A P E R 7 7 4-E Prepared in cooperotion with the Saudi Arabian Ministry of Petroleum and Mineral Resources The Uyaijah Ring Structure, Kingdom of Saudi Arabia By F. C. W DODGE SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 774-E Prepared in cooperation with the Saudi Arabian Ministry of Petroleum and Mineral Resources A study of the petrology, structure, and geochemistry of the plutonic roots ofa Precambrian epicontinental caldera UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Dodge, Franklin C. 1934- The Uyaijah ring structure, Kingdom of Saudi Arabia. (Shorter Contributions to General Geology) (Geological Survey Professional Paper 774-E) Bibliography: p. E15-El7. 1. Intrusions (Geology)-Saudi Arabia. 2. Rocks, Igneous. 3. Petrology-Saudi Arabia. I. Saudi Arabia. Wizarat al-Batrul wa-al-Tharway al-Ma'diniyah. II. Title. III. Series. IV. Series: United States. Geological Survey. Professional Paper 774-E. QE611.5.S33D62 551.8'8 78-32113 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-03148-5 CONTENTS Page 1\bstract ------------------------------------------------------------------------------ E1 Introduction -------------------------------------------------------------------------- 1 Regionalsetting ---------------------------------------------------------------------- 1 Rock types of the Uyaijah ring structure ------------------------------------------------ 3 ~etamorphicrocks ---------------------------------------------------------------- 3 Granodiorite of 1\11\reyef, the host batholith ---------------------------------------- 5 Granite of Jabal Thaaban, the core stock -------------------------------------------- 6 Leuogranite of Jabali\bu Khurg, the ring dike -------------------------------------- 7 Late dike rocks -------------------------------------------------------------------- 9 ~uartzveins ---------------------------------------------------------------------- 10 Structure and emplacement of the intrusive rocks ---------------------------------------- 10 Chemistry and evolution of the intrusive rocks ------------------------------------------ 12 Summary ______________________________________________________________________________ 15 Referencescited ________________________________________________________________________ 15 ILLUSTRATIONS Page PLATE 1. Geologic map of part of the Uyaijah ring structure, Buhairan-1\bu Khurg area, Kingdom of Saudi 1\rabia ____________ In pocket FIGURE 1. ~ap of the 1\rabian Peninsula showing the east edge of the 1\rabian Shield---------------------------------------- E2 2. Photomosaic of the region of the 1\rabian Shield bounded by 22" 30' and 23°00' N. lat and 44°00' and 45°00' E. long____ 2 3. Ternary diagram showing modes of rock types in circular masses ------------------------------------------------ 3 4. Simplified geologic map of the Uyaijah ring structure------------------------------------------------------------ 4 5. Ternary diagrams showing modes of individual plutonic rock samples -------------------------------------------- 6 6. Sketch showing primary foliations in the granodiorite of 1\11\reyef ---------------------------------------------- 11 7. Ternary diagram showing norms of analyzed plutonic rock samples ---------------------------------------------- 12 8. Graph showing major-element oxide contents of plutonic rocks____________________________________________________ 12 9. Graph showing minor-element contents of plutonic rocks -------------------------------------------------------- 13 10. Graphs showing chondrite-norrnalized rare-earth elements of igneous rocks -------------------------------------- 14 11. Schematic section showing development of the Uyaijah ring structure -------------------------------------------- 15 TABLES Page TABLE 1. 1\nalytical data on preintrusive schist and siliceous hornfels ---------------------------------------------------- E5 2. 1\nalytical data on granodiorite of 1\11\reyef -------------------------------------------------------------------- 6 3. 1\nalytical data on granite of Jabal Thaaban -------------------------------------------------------------------- 7 4. 1\nalytical data on altered granite of Jabal Thaaban ------------------------------------------------------------ 8 5. 1\nalytical data on leucogranite of Jabali\bu Khurg____________________________________________________________ 8 6. 1\nalytical data on late dike rocks______________________________________________________________________________ 9 7. Selected elemental ratios ofigenous rocks of the Uyaijah ring structure ------------------------------------------ 14 Ill SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY THE UYAIJAH RING STRUCTURE, KINGDOM OF SAUDI ARABIA By F. C. W. DODGE ABSTRACT are sources for the anomalous metal content (Dodge, The Precambrian Uyaijah ring structure is one of several 1973; Dodge and Helaby, 1975). batholithic masses in the eastern part of the Arabian Shield. A cen­ Field and analytical data collected during and fol­ tral core stock and a ring dike have been intruded into the circular lowing studies of mineralization are presented in this batholith, their form being controlled by the .-early developed pri­ report. Analyses of major-element oxides were carried mary foliation of the batholith. Analyses for major-element oxides and trace-element data indi­ out in U.S. Geological Survey Analytical Laboratories, cate that the central core stock resulted by continous differentiation Washington, D.C., using a method described by Shapiro of the batholithic magma with fractional crystallization and re­ and Brannock (1962) supplemented by atomic absorp­ moval of hornblende. In contrast, the chemical data suggest that tion. 'IWenty-eight elements were determined by in­ the ring dike crystallized from magma of ternary minimum compo­ strumental neutron activation analysis using the U.S. sition from which great amounts of feldspar were removed. Although related extrusive volcanic rocks are not exposed in the Geological Survey's Denver TRIGA reactor, following general region, the ring structure is believed to be the plutonic procedures described by Gordon and others (1968) and analog of an epicontinental caldera. Hertogen and Gijbels (1971). Modal analyses were done in U.S. Geological Survey laboratories, Jeddah, Saudi INTRODUCTION Arabia, by counting a minimum of 1,000 points on ap­ propriate sized grids superimposed on large stained The Uyaijah ring structure is part of a large igneous rock slabs (Jackson and Ross, 1956; L~niz and others, complex in central Saudi Arabia near the eastern edge 1964). Bulk rock densities were determined in Jeddah of the Arabian Shield (fig. 1). The structure consists of laboratories, using a large Westphal or a Jolly balance. metamorphic rocks and a large granodiorite batholith This study was done by the U.S. Geological Survey in that have been intruded by a core-forming granite accordance with an agreement with the Ministry of stock and later by a circular leucogranite ring dike. Petroleum and Mineral Resources, Kingdom of Saudi The entire assemblage of intrusive rocks is part of a Arabia. major Precambrian magmatic sequence of calc-alka­ line plutonic rocks abundant in the northeastern part REGIONAL SETTING of the Arabian Shield (Greenwood and Brown, 1973). Units of the ring structure are part of a great The region of the Arabian Shield bounded by 22° 30' number of granodiorite to granite plutonic bodies that and 23° N. lat and 44° and 45° E. long (fig. 2) is under­ commonly occur as nearly circular intrusive masses lain by Precambrian calc-alkaline plutonic and pre­ or as ring complexes and form the youngest major Pre­ plutonic metamorphic rocks that have been intruded cambrian group of igneous rocks of the Arabian Shield by a variety of felsic and mafic dikes and by quartz and (Fleck and others, 1976). Similar ring complexes occur carbonate-rich veins. A thin veneer of Quaternary sur­ to the west in Sudan (Vail, 1972; Neary and others, ficial debris consisting of wadi sediments, eolian dune 1976), forming an igneous province of more than 3 x sands, poorly sorted pediment materials, and talus 106 km2 . blankets much of the area. The Uyaijah ring structure has received consider­ Jackson and others (1963), Whitlow (1968a, b), and able attention because of the discovery of anomalous Lacombe and Letalenet (1970) have mapped the amounts of tungsten and molybdenum in wadi sedi­ metamorphic rocks in the region as parts of the Hala­ ments in the general area (Whitlow, 1968a, b, 1971; ban or Murdama Formations, both redesignated as Theobald, 1971; Theobald and Allcott, 1975; Flanigan groups by Schmidt and others (1973). The Halaban and Andreasen, 1975). Locally mineralized metamor­ Group is a widespread sequence of dominantly phic rocks and late molybdenite-bearing quartz veins metavolcanic rocks; the Murdama Group is a sequence El E2 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY \ I \ I / / / 0 1000 KILOMETERS FIGURE 1.-Map of the Arabian Peninsula showing the east edge of the Arabian Shield. The region of the shield bounded by 22°30' and 23° N. !at and 44° and 45° E. long (heavily shaded) is shown in figure 2. FIGURE 2.-Photomosaic of the region of
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