CO-24 X and Dario Barrero L. and Nestor Castro Q. Colombia Institute
Total Page：16
File Type：pdf, Size：1020Kb
CO-24 UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY PROJECT REPORT Colombia Investigations i (IR) CO-24 GEOLOGY AND MINERAL DEPOSITS OF AN AREA IN THE DEPARTMENTS OF ANTIOQUIA AND CALDAS (SUBZONE IIB), COLOMBIA By Tomas Feininger U. S. Geological Survey x and Dario Barrero L. and Nestor Castro Q. Colombia Institute Nacional de Investigaciones Geolo'gico-Mineras with a section on Economic Geology By Robert B. Hall U. S. Geological Survey U. S. Geological Survey OPEN FILE REPORT This report is preliminary and has not been edited or reviewed for conformity with Geological Survey standards or nomenclature Prepared of behalf of the Government of Colombia and the Agency for International Development U. S. Department of State 1973 GEOLOGY AND MINERAL DEPOSITS OF AN AREA IN THE DEPARTMENTS OF ANTIOQUIA AND CALDAS (SUBZONE IIB), COLOMBIA By Tomas Feininger U. S. Geological Survey and Dario Barrero L. and Ne'stor Castro Q. Colombia Institute Nacional de Investigaciones Geoldgico-Mineras with a section on Economic Geology By Robert B. Hall U. S. Geological Survey CONTENTS Page ABSTRACT................................................. 1 INTRODUCTION............................................. 2 Subzone IIB......................................... 4 Physical geography and geomorphology................ 4 Previous investigations............................. 9 Field and laboratory methods........................ 10 Acknowledgments..................................... 13 STRATIFIED ROCKS......................................... 16 Metamorphic rocks................................... 16 Precambrian rocks.............................. 16 Feldspar-quartz gneiss.................... 16 Ainphibo Li Lc ............................... 17 Marble.................................... 18 Ordovician rocks............................... 18 Other Paleozoic (?) metamorphic rocks........... 21 Sericite schist........................... 25 Feldspathic and aluminous gneiss.......... 29 Hornblendic gneiss........................ 33 Quartzitc................................. 35 Marble.................................... 38 Skarn..................................... 42 Gale-silicate gneiss...................... 43 Amphibolite............................... 43 Greenstone................................ 46 Undifferentiated rocks of low metamorphic grade.................................. 47 CONTENTS (cont'd) Page STRATIFIED ROCKS (cont'd) Metamorphism........................................... 48 Regional metamorphism............................. 49 Granulite facies in Precambrian rocks........ 49 Greenschist facies in Ordovician rocks....... 50 Greenschist to upper amphibolite facies in other Paleozoic(?) rocks................... 51 Definition of facies......................... 53 Retrograde metamorphism........................... 64 Thermal metamorphism.............................. 65 Dynamic metamorphism.............................. 68 Stratified felsic and intermediate volcanic rocks east of the Otu fault................................ 69 Porphyritic unit.................................. 70 Aphanitic unit.................................... 70 Cretaceous sedimentary rocks ........................... 71 Shale............................................. 71 Limestone......................................... 75 Conglomerate...................................... 75 Volcanic rocks.................................... 76 Tertiary sedimentary rocks ............................. 77 Alluvium.......................................... 79 Quaternary alluvium.................................... 80 11 CONTENTS (cont'd) Page INTRUSIVE ROCKS................................................ 81 Fol.sic porphyry intrusions onst of the Otu fault.......... 81 Intrusive gneiss.......................................... 82 Ultramafic rocks.......................................... 85 Talc and talc-tremolite rock......................... 85 Serpentinite......................................... 88 Hornblende gabbro at San Francisco........................ 88 Igneous rocks chiefly east of the Otu fault............... 90 Diorite and quartz diorite........................... 90 Amphibole gabbro..................................... 93 Andesite............................................. 94 Adamellite................................................ 95 Southwest of Amalfi.................................. 95 Near Hda. Marta Habana............................... 97 South of Sta. Isabel................................. 99 East of Yali......................................... 101 i West of Caracoli..................................... 102 The Antioquian batholith.................................. 104 Description.......................................... 104 Quartz diorite.................................. 105 Felsic quartz diorite........................... 113 Gabbro.......................................... 114 Form of the batholith........................... 118 Origin............................................... 121 Age................................................. 127 iii CONTENTS (cont'd) INTRUSIVE ROCKS (cont'd) Sonson batholith....................................... 128 Granodiorite at Tres Mundos............................ 130 Quartz monzonite at Aquitania.......................... 131 Dikes and other hypabyssal intrusives.................. 134 Milky quartz........................................... 137 STRUCTURAL GEOLOGY.......................................... 138 Faults................................................. 139 Normal faults..................................... 145 Faults related to the cooling of the Antioquian batholith....................................... 146 Intrusion faults.................................. 148 Wrench faults..................................... 154 Megabreccia............................................ 161 Lineaments............................................. 162 Folds.................................................. 162 Regional folds .................................... 162 Minor folds ....................................... 164 Foliation.............................................. 166 Schistosity....................................... 166 Slip cleavage..................................... 166 Platy flow structure .............................. 167 Catacl.ast ic Loliation. ............................ 167 l,i ncaL i on .............................................. 168 JJoudinage............................................. 168 iv CONTENTS (cont'd) Page GEOLOGIC HISTORY AND CORRELATIONS WITH OUTLYING AREAS......... 170 MINERAL RESOURCES OF IIB by R. B. Hall........................ 180 Gold and silver.......................................... 181 Historical background............................... 181 Relation of silver to gold.......................... 184 Lode mines.......................................... 185 Frontino Gold Mines Ltd........................ 186 El Limon mine .................................. 189 Small lode mines in Zone II.................... 191 Placer mines........................................ 193 Pato Consolidated Gold Dredging Ltd............ 194 La Viborita mine............................... 199 Anori placer district.......................... 203 Other placer districts ......................... 204 Origin of the gold.................................. 205 Gold and silver production in Zone II............... 206 Future of gold mining in Zone II.................... 206 Copper, lead, and zinc................................... 208 Pyrite................................................... 208 Cement raw materials ..................................... 209 ComcMitos do I. Nniv S. A. ............................. 209 Carbonate rock reserves in eastern Antioquia........ 210 Do 1omito................................................. 211 AmaiU.............................................. 211 El Jordan........................................... 213 CONTENTS (cont'd) Page MINERAL RESOURCES OF IIB (cont'd) Carbonate rock for other uses......................... 213 Lightweight aggregate material........................ 214 Clay............................................. 214 Quartz and silica..................................... 215 Canister for silica brick........................ 215 Quartz crystals....................................... 215 Wollastonite.......................................... 216 Andalusite............................................ 217 Andalusite in schists ............................ 217 Placer andalusite at El Bagre.................... 217 Exploitability................................... 218 REFERENCES CITED........................................... 219 ILLUSTRATIONS Figure 1. Index map showing location of Subzone IIB, Colombia...................................... 4a 2. Light tan quartz Lie showing typical fine lamination.................................... 23 3. Feldspathic and aluminous gneiss................ 24 4. Rounded hills of marble......................... 39 5. Base of marble hill undercut by the Rio Alicante. 40 6. The nine units of the metamorphic rocks in IIB and their distribution among the metamorphic facies. 52a VI ILLUSTRATIONS (cont'd) Figure 7. Progressive mineral changes through the three facies in rocks of three broad chemical compositions.................................. 53a 8. Sericitized andalusite porphyroblasts in schist. 56 9. Intrusive gneiss with typical porphyroblastic tex ture....................................... 84 10. Inclusions in