Slide 1: Role of Oligocene Volcanism in the geological setting of Au-Ag-Cu-Pb-Zn mineralization at the Plomosas District
Role of Oligocene Volcanism in the geological setting of Au-Ag-Cu-Pb-Zn mineralization at the Plomosas District, San Marcial Area, Southwestern Sierra Madre Occidental, Sinaloa, Mexico Paula Montoya-Lopera*, Gilles Levresse, Marcio Fonseca, Luis Coto, Marlen Salgado, Javier Villegas, Miguel Díaz, Fr
Slide 2: San Marcial location
San Marcial North America location Plomosas and San Marcial area • Mined since 18th century • Contains more than two long live hydrothermal breccia system • Hy breccias width varies from 1 to 15 m for over 1 km long and 1 km deep • Structural controlled by NW crust faults • Historical production of
Slide 3: Terrain Guerrero Suture
Terrain Guerrero Suture Centeno, 2017
Slide 4: Strain and Laramide magmatism at North of Mexico
Strain and Laramide magmatism at North of Mexico Tayoltita - San Dimas Causita - Mala Noche V V V V V V V V Silicic ignim V V V Silicic ignimbrites V V V (Second ign V (Second ignimbrite flareup) V V V ~25-24 Ma V ~24 Ma V V V V V V o o o o o o o o Polimictic c o Polimictic conglomerate v o o o o o
Slide 5: Oligocene extension
Oligocene extension Extensional basins 29-12 Ma Sinaloa and Nayarit extension begins in the late Oligocene, causing an angular unconformity between the Oligocene (32-29 Ma) and early Miocene (24-20 Ma) ignimbritic sequences Ferrari et al., 2002, Tectonics Ferrari et al., 2013, Geosphere Duque et al.
Slide 6: Magmatism and ore deposit development
Magmatism and ore deposit development Montoya-Lopera et al., 2019, 2020a, b, 2024, 2025
Slide 7: Local geology
Local geology Plomosas San Marcial Montoya-Lopera et al., 2025 (LA-ICP-MS U/Pb zircon Ages)
Slide 8: Lithogeochemistry
Lithogeochemistry Immobile elements Felsic Basic Late Oligocene Plomosas Early Oligocene Jurassic vol. seq. San Marcial Locking North (4 Acid Assays data)
Slide 9: San Marcial mineralization distribution
San Marcial mineralization distribution W E Plomosas Pb Zn As San Marcial Ag Cu Mo
Slide 10: Plomosas hydrotermal breccia
Plomosas hydrotermal breccia Amethyst Aca Qz Cpy Aca Gn Sp2 Sp1 Stage 1 Stage 2 Transition zone Stage 3 (Pb-Zn main event) (Cu high grade) (Ag high grade)
Slide 11: San Marcial Ag high grade tectonic hydrothermal breccia
San Marcial Ag high grade tectonic hydrothermal breccia • High angle Hy bx • Tilted East • Oligocene ( ~27 Ma) • Source by (andesitic porphyry int.) • Stage 3 (pre/ore/close bx) • Well-preserved high-grade Ag system • Almost 5 different Ag events • Green mineral main alt paragenesis (Mg Chl-Ep-Tur-T
Slide 12: Ore telescoping breccia (epithermal clasts)
Ore telescoping breccia SM – 212 (epithermal clasts) SMS 22-16 119.30 – 119.42 m 62603 Ag 3584 ppm Au 0.253 ppm Cu 0.049% Py 5 mm Qz Sp1 Ca Chl Aca Gn Chl FeOx Gn Fl Sp1 Ag high grade in clasts Ccp Py Pb: Cpy-Sp1-Gn-Sp2-Aca SEM (AMICS) 1.5 µm 1 mm Micro scanning (PRL)
Slide 13: Ore telescoping breccia (massive sulphide clasts)
Ore telescoping breccia Micro scanning SM – 209 SMS 22-10 (massive sulphide clasts) 194.55 – 194.65 m (Ag grain as clasts) 55572 Ag 566.6 ppm Au 0.108 ppm Gn Cu 0.020% Sp1 5 mm Sp2 Cpy Py Chl Aca Aca Py Ep Sp Ag high grade Qz FeOx SM: Aca-Py Pb: Cpy-Sp1-Gn-Sp2 SEM (AMICS) 1.5 µm 1 mm Micro scanning
Slide 14: Ore hydrothermal quartz – FeOx breccia
SM – 211 Ore hydrothermal quartz – FeOx breccia SMS 22-16 (primary Aca filling open space) 71.77 – 71.87 m 62490 Ag 252 ppm Au 0.214 ppm Chl Cu 0.0031% FeOx Qz 5 mm Aca Chl Aca Hm Ep Ca Fl Qz Tur Pl 1.5 µm Ag high grade in matrix SEM (AMICS) SM: Hm-Aca 1 mm Qz Micro scanning (PRL)
Slide 15: Hydrothermal crackle calcite > quartz cemented breccia
Hydrothermal Hydrothermal crackle calcite > breccia quartz cemented breccia (primary Aca on Qz thin veins) Ca Chl 5 mm Polymictic volcano- clastic rock Hm Aca Aca Hm SM – 208 Ag high grade SMS 22-10 Ba 119.50 –119.70 m SM: Aca-FeOx 1.5 µm 55420 SEM (AMICS) Ag 117.26 ppm Au 0.0025 ppm 1 mm Cu 0.0038%
Slide 16: Thin calcite vein on host rock
Thin calcite vein on host rock (primary Arg filling thin Ca veins) Ca Chl FeMg Ms 5 mm Ca Arg Py Qz Parallel Ag high grade SM – 219 SMS 22-23 Sp1 M3: Ca-Arg 254.75 – 254.84 m SEM (AMICS) 1.5 µm M2: Sp1-Py2 111066 M1: Py1 Ag 113 ppm Au 0.154 ppm Cu 0.006% 1 mm As 778 ppm
Slide 17: Laramide Cu porphyry
San Marcial area geochronology fertility events Cu porphyry Laramide Montoya-Lopera et al., manuscript
Slide 18: In a regional context
In a regional context Montoya-Lopera et al., manuscript
Slide 19: THANKS
Role of Oligocene Volcanism in the geological setting of Ag-Au-Pb- Zn-Cu mineralization at the Plomosas District, San Marcial Area, South-Western Sierra Madre Occidental, Sinaloa, Mexico THANKS Paula Montoya-Lopera*, Gilles Levresse, Marcio Fonseca, Luis Coto, Marlen Salgado, Javier Villegas, Miguel
Slide 20: Questions?
Questions?
Slide 21: Appendices
Appendices
Slide 22: Lithogeochemistry
Lithogeochemistry Scott Halley Adjunct Professor at CODES/UTAS
Slide 23: Atomic # a Valence
Atomic # a Valence © compositio Symbol o: inatio x or elem ht pereent) ov el nent Oxide pm) in various rs Element Formula Atomic Wt. Formula Wt. 4.003 10 * Royal Soc c Table + TUPAC Periodic Table of the Elements and Is + The Earth Scientist's Periodic Table of the Elements a Their Ions * Michael Da
Slide 24: Lithogeochemistry
Lithogeochemistry Ross Large Emeritus Professor at CODES/UTAS
Slide 25: Fluid inclusion studies
Fluid inclusion studies Montoya-Lopera et al., (manuscript)
Slide 26: LA-ICPMS methods for trace element analysis and imaging
LA-ICPMS methods for trace element analysis and imaging Ivan Belousov (CODES)
Slide 27: San Marcial Ag signature of parallel veins
SM-219 Ag San Marcial Ag signature of parallel veins! 8/07/2025 27
Slide 28: Plomosas mineralization distribution
Plomosas mineralization distribution W E Pathfinders
Slide 29: Plomosas and San Marcial Geological Evolution
Plomosas and San Marcial Geological Evolution Montoya-Lopera et al., manuscript