Abstract

ALVAREZ-ORTIZ, Iris; CRUZ-GAMEZ, Esther María; LASTRA-RIVERO, José F.  and  VELASCO-TAPIA, Fernando. Alterations related to the sulphurous mineralization of the Júcaro and Yagruma deposits, West of Cuba. Min. Geol. [online]. 2019, vol.35, n.3, pp. 270-288. ISSN 1993-8012.

The present work offers new information on the mineral associations, particularities of hydrothermal processes and types of alteration from a comparative study (mineralogical, textural and geochemical) of alterations in rocks from Júcaro and Yagruma deposits (Encrucijada Formation). The diagenetic alteration is related to chlorite, pyrite, calcite, albite, quartz and zeolite, has a regional character and is distributed throughout the Formation, showing a general trend to higher values of Na2O + CaO (adj) and lower in FeOt + MgO (adj), with alteration index (AI) between 18 and 40. The hydrothermal alteration occurs mainly in basalts more related to the Júcaro deposit (stratabound) and to the volcanic sills of diabase and basalts of the Yagruma deposit (conduit zone); the lowest values ​​of Na2O + CaO (adj) and higher are present in FeOt + MgO (adj), with AI between 26 and 52. The study revealed that the hydrothermal alteration is of low intensity with the association of typical minerals described for this process in the VMS (Volcanic-Massive Sulfide): chlorite, calcite, pyrite, quartz, sericite and epidote. It is corroborated that the mineral alterations are similar in both deposits, just in Júcaro chlorite-calcite-pyrite-sericite predominates and chlorite-pyrite-calcite-sericite-epidote-quartz in Yagruma.

Keywords : diagenetic alteration; hydrothermal alteration; Massive volcanogenic sulphides; alteration rates; stratabound formation; Honda Bay.

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