Plate 1 Geologic Map of the Yanacocha District Cajamarca, Peru Geologic mapping of the central part of the Yanacocha District conducted prior to 2001: D. Abarca, J. Barreda, R. Bartra, E. Calderón, M. Changanaqui, J. Edwards, J. Escalante, B. Harvey, T. Klein, B. Leach, C. Loayza, A. Longo, S. Myers, R. Pinto, A. Quiroz, M. Rutti, and C. Velasco. This geologic map was completed and compiled as part of an Oregon State University doctoral dissertation (Longo, 2005) Kls Limestone and marls Cajamarca Fm. and Pulluicana-Quillquiñán Groups Quartzite and shales Goyllarisquizga Group Kq Cretaceous Sedimentary Rocks Calipuy Group Volcanic Rocks Atazaico Andesite Lava and Dome Rocks Colorado Pyroclastic and Flow-Dome Sequence Azufre Andesite-Dacite Lava and Dome Rocks San Jose Ignimbrite and Dome Sequence Ted - early hb-bi dacite intrusions Early Quilish-Exaltado Dacite Typ - Yanacocha feldspar porphyry and diatreme breccia Coriwachay Dacite La Quinua Sediments (Pliocene ?) Tl - Tuffaceous Lacustrine Sediments Yanacocha gravels (Pleistocene) Qg - fluvial and glacial deposits Tulx - upper laminated rocks Tcd - Corimayo-Quilish-Punta Negra dacite domes Typq - Tcyd - Tbxh - Yanacocha phreatic-hydrothermal breccia Tnrd - Negritos rhyolite domes Tnri - Negritos rhyolite ignimbrite Tusjd - Upper San Jose px-hb dacite dome rocks Tmsjd - Middle San Jose hb-bi dacite dome rocks Tlsjd - Lower San Jose px-hb dacite dome rocks Tusj - Upper San Jose px-hb dacite spatter ignimbrite Tmsj - Middle San Jose hb-bi andesite-dacite ignimbrite Tlsj - Lower San Jose px-hb andesite-dacite ignimbrite Tmlx - Middle laminated rocks Tuphad - upper px-hb andesite-dacite dome rocks Tupha - upper px-hb andesite-dacite lava dominant rocks Tmmp - hb andesite porpyritic lavas and intrusions Tmmi - Maqui Maqui Ignimbrite (inc. Cori Coshpa tuff) Tllx - Lower laminated rocks Tlphad - lower px-hb andesite dome rocks Tlpha - lower px-hb andesite lava dominant Tpt - Peña de Leon tuff (eastern side) Tcfd - Cerro Fraile pyroclastic sequence Tlalc - Chaupiloma lower andesite lahar sequence Tlalt - Tual lower andesite lahar sequence Tha - Huambo Cancha andesite Tmcv - Minas Congas volcanic rocks (eastern side) Rocks of the Yanacocha Volcanics Stratigraphic Legend Lower Miocene Middle Miocene Upper Miocene altered porphyry rocks and diatremes (no quartz phenocrysts) Yanacocha Lake rhyolite-dacite dome dikes and diatreme Yanacocha quartz dacite porphyry plugs and diatreme and intrusions Unmapped areas fault well located possible fault fault contact ~30m fault contact ~15m prominent circular feature possible contact contact ~30m contact ~15m contact ~5m contact well located Contacts Faults Structural attitudes omitted for clarity (see Longo, 2005) Limits of the argillic and advanced argillic alteration in outcrop Limits of weak argillic and advanced argillic alteration Limits of alteration concealed or buried Yanacocha 6ºS 80ºW Index Map of Acknowledgements Peru 765000E 785000E 9225000N 2 5 9 8 1 4 6 3 7 9240000N 9235000N 9230000N 9225000N 9220000N 9215000N 760000E 765000E 770000E 775000E 780000E 785000E 755000E 0 5 Kilometers Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tcfd Tha Tlalt Tlalt Tlalt Tlalt Tlalt Tlalc Tlalc Tlalc Tlalc Tlalc Tlalc Tlalc Tlalc Tpt Tpt Tpt Tmcv Kls Kls Tpt Kls Kls Kq Kq Ted Ted Ted Tl Tlpha Tlpha Tlpha Tlpha Tlpha Tlpha Tlpha Tlpha Kq Tlphad Tlphad Tlphad Qg Qg Qg Tuphad Tuphad Tmlx Tlsj? Tmsj Tusj Tusj Tlsj Tlsj Kls Tmsj Tmsj Tmsj Tnri Tmmi Tmmi Tmsj Tupha Tuphad Tuphad Tcd Tcd Tupha Tlsjd Tusjd Tmsjd Tuphad Chaquicocha Gold Deposit Outline Cerro Regalado Quilish Tual Chaupiloma Huambo Cancha Cerro Fraile Antibuyoc Cerro Negro El Arco Barranco Tatiana Pachanes Sorpresa China Linda Elita Ocucho Alto Machay Los Pinos Exaltado Cerro Atazaico Hornamo Sugares Maqui Maqui C o Yanacocha Pampa Larga Colorado Graben Pabellon Cori Coshpa Punta Negra Arnacocha Corimayo Carachugo Chaquicocha Azufre Pampa Cerro Negro Negritos La Quinua Graben Pampa Corimayo San Jose Baul Machay Sacsha sur Cajamarca Otuzco Trough Combayo Otuzco Ventanillas de Combayo Quebrada Honda La Quinua Facility Lake district Paquerumi-Huacataz Cerro Collotan Stratacone glacial deposits Kupfertal norte Encajon Tapado Granja Porcon Quecher La Quinua dome C o Canta alta Combayo - place name of locality (see text)