Abstract

SOTO, Daniel  and  ALVARADO, Guillermo E. Costa Rican peperites. Rev. Geol. Amér. Central [online]. 2012, n.47, pp.55-68. ISSN 0256-7024.

This paper describes petrographically and genetically, a number of peperites, as examples of spatial and temporal coexistence of magmatism and sedimentation in Costa Rica. The cases are presented in basic igneous complexes (ophiolites), mixtures varying from incomplete (megablocks of radiolarite with diabase in the Nicoya Complex) to complete mixes in various stages of Maastrichtian-Paleocene (Golfito Formation) or Paleocene pelagic limestones with basalts (Quepos Subcomplex or Tulín Formation) to form brechoid and pillowed peperites. Within the Oligo-Miocene arc, there are examples extended along the Talamanca range and its foothills, as well as Sarapiquí’s plains represented for brechoid and bulbous (fluidal) peperites in latiandesitic lavas (Pacacua Formation) or brechoid peperitic pipes in ignimbrites (Mata de Limón Member) or possible brechoid peperites in lavas in the Crucitas mining prospect (Cureña Formation), or simple brechoid peperites in andesitic flow (Pacacua Formation, in Talamanca) or as hydroclastic breccias with fragments of dacitic composition in lava flow deposits of Carbonal Guanacaste, just between the beaches Cabuyal and Naranjo. All these rocks represented proximal equivalents of the explosive, effusive and subvolcanic volcanism (endogenous domes and criptodomes) and his concomitance with the fluvial sedimentation. In Quaternary period, we have a sample in the base of Tiribí Formation in contact with Palmares Lacustrine. Also this paper included possible and potential cases. It hopes that the description and interpretation of this type of rocks helps to its identification in other regions of Costa Rica and Central America in general, as well as a potential source for the exploration of valuable metals.

Keywords : Peperites; hydroclastic breccias; criptodomes; volcanism; sedimentation; Costa Rica.

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