Transitional adakite-like to calc-alkaline magmas in a continental extensional setting at La Paz Au-Cu skarn deposits, Mesa Central, Mexico: metallogenic implications

  • Porfirio J. Pinto-Linares Instituto Potosino de Investigación Cientí fi ca y Tecnologica, División Geociencias Aplicadas, Camino a la Presa San José 2055, Col. Lomas 4ª Sección, 78216, San Luis Potosí, S.L.P., Mexico.
  • Gilles Levresse Programa de Geofluidos, Centro de Geociencias Universidad Nacional Autónoma de México, Campus Juriquilla, Blvd. Villas del Mesón s/n, 76230 Querétaro, Qro., Mexico.
  • Jordi Tritlla Programa de Geofluidos, Centro de Geociencias Universidad Nacional Autónoma de México, Campus Juriquilla, Blvd. Villas del Mesón s/n, 76230 Querétaro, Qro., Mexico.
  • Víctor A. Valencia Department of Geosciences, University of Arizona, 1040 East Fourth Street, Room 510, Tucson, Arizona 85721-0077, USA.
  • José M. Torres-Aguilera Universidad Autónoma de San Luis Potosí, Depto. Ciencias de la Tierra, Dr. Manuel Nava 8, 78290 San Luis Potosí, S.L.P., Mexico.
  • Manuel González Negociación Minera Santa María de la Paz y Anexas, S.A. de C.V., 78830 Villa de La Paz, S.L.P., Mexico.
  • David Estrada Negociación Minera Santa María de la Paz y Anexas, S.A. de C.V., 78830 Villa de La Paz, S.L.P., Mexico.
Keywords: Adakite-like, Au-Cu skarn, U-Pb, geochronology, geochemistry, La Paz, Mesa Central, Mexico.

Abstract

The granodiorite intrusions with associated Cu-Au skarn mineralization of La Paz district are located in the east part of the Mesa Central of Mexico. The skarn developed at the contact between a middle Cretaceous calc-argillaceous sedimentary sequence and the magmatic intrusions. A Ag-Pb-Zn vein system postdates the intrusive-skarn assemblage. Two well defined fault systems (N-S and E-W) divide the La Paz district. The N-S Dolores fault, with a normal vertical displacement estimated between 500 to 1000 m, separates the western Au-Cu skarn zone from the eastern hydrothermal Ag-Pb-Zn vein system. This fault is considered to be part of the Taxco-San Miguel de Allende fault system. The U-Pb dating of the intrusives at the La Paz district clearly indicates a single emplacement event dated at ca. 37 Ma (monocrystal zircon age). This age probably represents the last post-Laramide orogenic mineralizing event known to occur in the Sierra de Catorce district. Also, four calculated discordant ages suggest the presence of greenvilian basement underneath a a thick crust (35-45 km).

The chemistry of the intrusive show a certain variability in composition, but they mostly belong to the high-K calc-alkaline magmatic series. Major and trace elements relationships for the intrusives show a chemical evolution from the adakite to the island arc fields, and from mineralized to barren intrusives, repectively. They also suggest the importance of crustal delamination processes, and the necessity of deep cortical drains to transfer oxidized magmas and metals to surface.

Published
2018-01-22
Section
Articles