LEADER 05134ctm 2200565 i 4500001 ocm07662106 003 OCoLC 005 20240122153501.0 008 810812s1981 xx abf bm 000 0 eng d 035 (Sirsi) o07662106 035 (OCoLC)7662106 040 ERE |beng |erda |cERE |dOCLCQ |dOCLCO |dOCLCF |dOCLCO |dOCLCA |dOCL |dOCLCO |dOCLCQ |dOCL |dOCLCO |dOCLCQ |dOCLCO |dERE |dUtOrBLW 043 n-mx--- 049 EREE 050 4 QE203.C4 |bC3x 100 1 Capps, Richard C., |eauthor. |=^A133167 245 14 The geology of the Rancho El Papalote area, Chihuahua, Mexico / |cby Richard C. Capps. 264 0 |c1981. 300 73 leaves, 3 leaves of plates : |billustrations, maps (some color) ; |c28 cm 336 text |btxt |2rdacontent 337 unmediated |bn |2rdamedia 338 volume |bnc |2rdacarrier 500 Six folded leaves in pocket. 502 |bM.S. |cEast Carolina University |d1981 500 "Presented to the faculty of the Department of Geology ... in partial fulfillment of the requirements for the degree Master of Science in Geology." 520 3 The Rancho El Papalote area is 35 km north of Chihuahua City and includes the base metal mines at Terrazas. The oldest rocks are highly fractured, massive, mid-Cretaceous, biomicrites containing rudistid bioherms, that crop out on ridges and peaks surrounded by volcanic rocks of two different eruptive periods. The oldest volcanics are altered rhyolite and/or dacite flows, flow breccias, and minor lithic tuffs. The flow breccias are thickest around Cerro Choloma which may represent a vent area. A boulder breccia containing limestone and chert clasts occurs along the limestone-older volcanic contact. The younger volcanics are rhyolite ash flows with minor basalt and andesite flows. There are at least five 8 T 86 cooling units. A 44 m.y. (initial 'Sr/° Sr ratio = 0.7048) old vitric-crystal tuff (22-25% phenos; san/qtz = 4 to 5; san comp = Ab₅₆Or₄₀An₃Fe₁) overlies the older volcanics 1 km west of the ranch buildings. The Red Platy, a vitric ash-flow rhyolite (Or₅₄), overlies the 44 m.y. tuff, and it is a distinctive marker bed. A small dike cutting the 44 m.y. tuff may represent a vent for the Red Platy. The three youngest units, vitric tuffs in the eastern part of the area, dip gently to the northeast and are cut by northwest-trending normal faults. The oldest of these ash flows has a basal lithic zone and contains sanidine phenocrysts (3%; Ab₅₆Or₄₀An₃Fe₁ overlying unit has a vesicular base and contains sanidine phenocrysts (6%; Ab₅₆Or₄₀An₄Fe₂). The youngest ash flow 87 86 in this sequence (28 m.y., initial Sr/ Sr ratio = 0.7082) contains sanidine, quartz, and fayalite phenocrysts (san/qtz = 1; phenos = 4%; san comp = Ab₄₈Or₅₀An₁Fe₁). A 37 m.y. old basalt overlying the Red Platy contains distinctive phaneritic, pyroxene-plagioclase xenoliths. To the south the older volcanics are overlain by an andesite flow. At Minas Terrazas, copper deposits occur in skarns near a felsic intrusive. These skarns are mainly andradite and contain small amounts of pyrite and chalcopyrite. A bedrock geochemical reconnaissance indicates base metal, silver and gold anomalies east of Terrazas in the limestones and older volcanics. The results of a biogeochemical reconnaissance also indicate anomalous metal values in some samples of the plants Prosopis juliflora (mesquite), Rhus virens and Rhus microphylla. 504 Includes bibliographical references (leaves 62-65). 650 0 Geology |zMexico |zChihuahua (State) |=^A27650 650 0 Geology, Stratigraphic. |=^A23152 650 0 Mineralogy |zMexico |zChihuahua (Chihuahua : State) |=^A15837 650 7 Geology. |2fast |0(OCoLC)fst00940627 650 7 Geology, Stratigraphic. |2fast |0(OCoLC)fst00940727 650 7 Mineralogy. |2fast |0(OCoLC)fst01022406 651 7 Mexico |zChihuahua (State) |2fast |0(OCoLC)fst01330630 |?UNAUTHORIZED 655 7 dissertations. |2aat |0(CStmoGRI)aatgf300028029 655 7 Academic theses. |2fast |0(OCoLC)fst01726453 655 7 Academic theses. |2lcgft 655 7 Thèses et écrits académiques. |2rvmgf |0(CaQQLa)RVMGF-000001173 700 1 Mauger, Richard L. |q(Richard Leroy), |d1936- |edegree supervisor. |=^A1450473 710 2 East Carolina University. |bDepartment of Geology. |?UNAUTHORIZED 856 40 |zAccess via ScholarShip |uhttp://hdl.handle.net/10342/11627 949 Click on web address |wasis |hjoyner101 949 Click on web address |wasis |hhsl111 994 C0 |bERE 596 1 4 998 185000