DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Geology of the Precanibrian rocks of the Jabal Habashi quadrangle, sheet 26F, Kingdom of Saudi Arabia/ with a Geographic map of the Jabal Habashi quadrangle compiled by F. J. Fuller by I/ I/ Peter R. Johnson and Paul L. Williams Open-File Report 85-3 Prepared for the Ministry of Petroleum and Mineral Resources, Deputy Ministry for Mineral Resources, Jiddah, Kingdom of Saudi Arabia This report is preliminary and has not been reviewed jfor conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature, I/ Associates, Limited, 1425 Carrollburg Place SW, ~~ Washington, DC 20024 _2/ U.S. Geological Survey Saudi Arabian Mission, Jiddah. 1985 CONTENTS page ABSTRACT................................................... 1 INTRODUCTION............................................... 2 Location and geography................................. 2 Previous investigations................................ 4 Present work........................................... 4 GEOLOGIC SETTING........................................... 5 PROTEROZOIC LAYERED ROCKS.................................. 8 Introduction........................................... 8 Amphibolite and schist................................. 8 Bu'qaya formation...................................... 9 Qarnayn formation...................................... 10 Sandstone......................................... 10 Conglomerate...................................... 11 Rhyolite.......................................... 11 Basalt............................................ 12 Maraghan formation of the Murdama group................ 12 Sandstone......................................... 13 Marble............................................ 13 Andesite and basalt............................... 14 Hibshi formation....................................... 14 Conglomerate...................................... 16 Sandstone and dacite.............................. 17 Andesite and dacite............................... 18 Sandstone, siltstone, and conglomerate............ 19 Rhyolite.......................................... 20 Basalt............................................ 20 Sedimentary clast conglomerate.................... 21 Sandstone, undivided.............................. 21 Turmus formation....................................... 21 Rhyolite and quartz latite............................. 22 Raha formation......................................... 23 Dacite................................................. 24 Dacite and rhyolite.................................... 24 Jibalah group (?)...................................... 25 Depositional environments of the layered rocks......... 25 PROTEROZOIC INTRUSIVE ROCKS................................ 31 Introduction........................................... 31 Pre-Murdama intrusive rocks............................ 33 Gneissic monzogranite............................. 33 Samirah quartz monzodiorite....................... 34 Laban complex..................................... 34 Gabbro............................................ 36 page Post-Murdama intrusive rocks........................... 36 Metagabbro........................................ 36 Makhul complex.................................... 37 Aydah suite....................................... 38 Quartz monzodiorite.......................... 42 Granodiorite................................. 42 Diorite, quartz monzonite, quartz diorite and trondhjemite............................ 45 Monzodiorite................................. 45 Shuwayman suite................................... 46 Gabbro, diorite, and tonalite..................... 48 Dulaymiyah syenogranite........................... 49 Postkinematic intrusive rocks.......................... 49 Hamrah monzogranite............................... 49 Qutn syenogranite................................. 50 Alkali-feldspar granite suite..................... 53 Alkali-feldspar granite...................... 54 Muscovite-bearing alkali-feldspar granite.... 54 Soda-pyribole-bearing alkali-feldspar granite 57 Alkali-feldspar quartz syenite granophyre.... 57 Aplite............................................ 58 Quartz veins and plugs............................ 58 Dikes............................................. 59 PALEOZOIC ROCKS............................................ 60 Saq Sandstone.......................................... 60 Tabuk Formation........................................ 60 CENOZOIC ROCKS AND DEPOSITS................................ 61 Tertiary to Quaternary volcanic rjocks.................. 61 Basaltic tuff..................................... 61 Alkali-olivine basalt............................. 62 Cinder cones...................................... 62 Tertiary to Quaternary gabbro.......................... 62 Quaternary surficial deposits.......................... 63 Duricrust......................................... 63 Lag deposits...................................... 63 Alluvial fan deposits............................. 63 Alluvium.......................................... 64 Sabkhah deposits.................................. 64 GEOCHRONOLOGY.............................................. 64 Layered rocks.......................................... 64 Intrusive rocks........................................ 66 STRUCTURE.................................................. 66 Pre-Murdama structures................................. 67 Post-Murdama structures................................ 67 Folds............................................. 67 ii page Fracture cleavage................................. 67 Raha fault zone................................... 68 Transcurrent faults............................... 69 METAMORPHISM............................................... 70 SUMMARY OF GEOLOGIC HISTORY................................ 71 ECONOMIC GEOLOGY........................................... 73 Introduction........................................... 73 Gold................................................... 74 Molybdenum............................................. 78 Tin.................................................... 78 Other metallic mineralization.......................... 79 Pozzolan............................................... 80 DATA STORAGE............................................... 80 REFERENCES CITED........................................... 81 ILLUSTRATIONS Plates are in back pocket Plate 1. Geologic map of the Jabal Habashi quadrangle, sheet 26F, Kingdom of Saudi Arabia. 2. Geographic map of the Jabal Habashi quadrangle. Figure 1. Index map showing the location of the Jabal Habashi quadrangle................................ 3 2. Lower part of the Hibshi formation at Jabal Habashi (photoplate).............................. 15 3. Plot of silica-potash contents of the layered rocks for the Jabal Habashi quadrangle, sheet 26F. 29 4. Simplified map of the Proterozoic intrusive rocks in the Jabal Habashi quadrangle............. 32 5. Quartz- alkali-feldspar- plagioclase (QAP) ternary diagram (Streckeisen, 1976) showing the modal composition of pre-Murdama intrusive rocks in the Jabal Habashi quadrangle................... 35 6a, b, c, d. Quartz- alkali-feldspar- plagioclase (QAP) ternary diagram (Streckeisen, 1976) showing the modal composition of post-Murdama intrusive rocks in the Jabal Habashi quadrangle............. 39 iii page 7a, b, c. Quartz- alkali-feldspar- plagioclase (QAP) ternary diagram (Streckeisen, 1976) showing the modal composition of postkinematic intrusive rocks in the Jabal Habashi quadrangle................... 51 8. Mineral occurrences and ancient workings in the Jabal Habashi quadrangle, sheet 26F............... 75 Table 1. Correlation of map units used in this report with those used on the 1:100,000-scale source maps.............................................. 6 2. Major element analyses and CIPW norms (calculated for analyses normalized to 100 percent, anhydrous), for selected metasedimentary and metavolcanic rocks in the Jabal Habashi quadrangle........................................ 27 3. Descriptive summary of quartz monzodiorite from the post-Murdama Aydah suite, Jabal Habashi quadrangle, sheet 26F............................. 43 4. Descriptive summary of granodiorite from the post-Murdama Aydah suite, Jatoal Habashi quadrangle, sheet 26F......................................... 44 5. Descriptive summary of the post-Murdama Shuwayman monzogranite suite, Jabal Habashi quadrangle, sheet 26F......................................... 47 6. Descriptive summary of the postkinematic alkali-feldspar granite suite, Jabal Habashi quadrangle, sheet 26F............................. 55 7. Radiometric-age determinations for rocks within the Jabal Habashi quadrangle, sheet 26F........... 65 8. Summary of gold occurrences in the Jabal Habashi quadrangle, sheet 26F............................. 76 iv EXPLANATORY NOTES TO THE GEOLOGIC MAP OF THE PRECAMBRIAN ROCKS OF THE JABAL HABASHI QUADRANGLE, SHEET 26F, KINGDOM OF SAUDI ARABIA, WITH^A, GEOGRAPHIC MAP OF THE JABAL HABASHI QUADRANGLE COMPILED BY F. J. FULLER by. Peter R. Johnsonl and Paul L. Williams2 ABSTRACT The Jabal Habashi quadrangle contains formations of Lower Paleozoic and Cenozoic age, unconformably overlying part of the Precambrian Arabian Shield. The Precambrian formations include metamorphosed and strongly deformed volcanic and volcaniclastic rocks and plutons of calc-alkalic, mafic to intermediate composition, dated at about 645 Ma. These are unconformably overlain by the