Aportes al conocimiento del Magmatismo de la Cordillera Central de Colombia en su Flanco Oriental: Área geotérmica de San Diego, Samaná, Caldas

Abstract

Five plutonic bodies were characterized in the San Diego geothermal area, whose chemical characteristics position four units (Florencia Stock, Sonsón Batholith, Samaná Complex and Samaná Alaskite) in the field of granites type I, and the Gneissic Intrusive as granite type S. All have chemical signatures of Rb, Y and Nb typical of subduction environment granitoids, calcoalcaline series and magnesium type. The U-Pb data by LA-ICP-MS in zircons showed ages of 132.8±2.6 my for the Samaná Alaskite, 129.8±9.7 my for the Samaná Igneous Complex, 54.6±4.4 my for the Florencia Stock and 47±11 my for the Sonsón Batholith. Nine andesitic porphyritic bodies (Pl+Anf) of which five were recognized in this work, are expressed some of them with evident domic forms and vitreous matrices. These porphyritic bodies present a greater degree of hydrothermal alteration (phyllic and argillic), especially in the Puente Linda sector, structurally controlled, with the presence of oriented breccias (EW) along the Samaná River. All of these bodies with adakitic signatures (Sr between 335.31 and 1160.25 ppm) have positive anomaly EuN/√(SmN*GdN) from 1.34 to 2.07. The Puente Linda porphyry (Pl + Qz + Anf ± Cb ± K ± Dck) has superimposed the greater alteration in extension and degree; U-Pb dating in zircons, showed an age of 2.1±1.9 Ma. On the other hand, five dacite bodies (Qz + Pl + Anf) were equally recognized and characterized, whose geochemistry contrasted with that of other intrusions, with negative anomalies EuN/√(SmN*GdN) from 0.18 to 0.64. Finally, two volcanic structures, San Diego dome (Qz + Pl + Bt) and El Escondido volcano domes (Pl + Anf) are recognized as evidence of recent volcanic activity; Ar-Ar dating recorded a Plateau age of 89±4.4 Ka for San Diego and 153.7±38.2 Ka for El Escondido.