GEOCHEMISTRY AND RADIOMETRIC REINTERPRETATION OF THE METABASITES OF THE ARQUIA COMPLEX
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Universidad Industrial de Santander
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El Complejo Arquía aflora como una franja alargada, estrecha y discontinua de esquistos anfibólicos y sericíticos, cuarcitas y neises, junto a anfibolitas y metagabros asociados a cuerpos ultramáficos, se localiza entre las fallas Cauca Almaguer y Silvia Pijao, en la zona de colisión de basamento metamórfico de la Cordillera Central y oceánico de la Cordillera Occidental de Colombia, siendo considerado como parte de un “melange” conformado por franjas de bloques discontinuos y delgados que involucra retazos de corteza continental y corteza oceánica, entre las Fallas San Jerónimo y Cauca - Almaguer. El análisis geoquímico se hizo sobre metabasitas del Complejo Arquía (Esquistos de Sabaletas, Esquistos Anfibólicos del río Cauca, Secuencia Metamórfica de Buesaco, Grupo Bugalagrande, Complejo Rosario, Complejo Bolo Azul, Esquistos de Lisboa - Palestina y Metagabro de Santa Rosa), que corresponden a protolitos afines con basaltos toleíticos subalcalinos ricos en Mg de tipo N-MORB, variando la SiO2 entre 44,24% y 53,49wt%, el álcalis vs SiO2 entre 0,03% a 0,09wt%, la relación Nb/Y entre 0,05 y 0,15 y el #Mg entre 45,03 a 72,34.
Las edades del Complejo Arquía se agrupan principalmente en dos intervalos: 100 a 113 Ma y 203 a 229 Ma. Las edades entre 100 y 113 Ma corresponden a datos radiométricos obtenidos mediante el método K/Ar, que coinciden con el inicio del Arco Barroso – Sabanalarga que afectó la zona de sutura y las dos cortezas, siendo interpretadas como posibles edades de calentamiento. Las edades entre 203 y 229 Ma se obtuvieron por el método Ar-Ar y se interpretan como la posible edad de metamorfismo, concordantes con la edad de metamorfismo del Complejo Cajamarca, que es el basamento de la Cordillera Central de Colombia.
The Arquia Complex appears as a strip elongated, narrow and discontinuous, consisting in amphibole - sericite schist, quartzites and gneisses alongside amphibolites and metagabbros associated with ultramafic rocks. There is located between the Cauca Almaguer and Silvia Pijao Faults, in the collision zone of metamorphic basement of the Cordillera Central and oceanic basement of the Cordillera Occidental of Colombia. The Arquia Complex has been considered as part of a “melange” which is formed for strips thins discontinuous blocks involving continental and oceanic crust parts between Cauca almaguer and San Jerónimo Faults. Geochemical analysis was performed on Arquia Complex metabasites (Sabaletas schist, Cauca river amphibole schist, Buesaco metamorphic sequence, Bugalagrande Group, Rosario Complex, Bolo azul Complex, Lisboa – Palestina schist and Santa Rosa metagabbro), corresponding to subalkaline tholeiitic basalts protolites type N-MORB with high magnesium, SiO2 between 44,24% and 53,49wt%, alkalis vs SiO2 0,03%- 0,09wt%, with Nb/Y=0,05-0,15 ratios and #Mg=45,03 – 72,34. The Arquia Complex ages are grouped into the two ranges: 100-113 Ma and 203-229 Ma. The first range (100-113 Ma) corresponded with radiometric ages obtained by K/Ar method, and coincide with the start stage of the Barroso- Sabanalarga Arc, affecting the suture zone and the two crusts, being interpreted as heating ages. The second range include ages between 203 – 229 Ma, obtained by Ar/Ar, and are interpreted as metamorphic age. These data are consistent with the age of metamorphism of the Cajamarca Complex, being this the basement of the Cordillera Central of Colombia.
The Arquia Complex appears as a strip elongated, narrow and discontinuous, consisting in amphibole - sericite schist, quartzites and gneisses alongside amphibolites and metagabbros associated with ultramafic rocks. There is located between the Cauca Almaguer and Silvia Pijao Faults, in the collision zone of metamorphic basement of the Cordillera Central and oceanic basement of the Cordillera Occidental of Colombia. The Arquia Complex has been considered as part of a “melange” which is formed for strips thins discontinuous blocks involving continental and oceanic crust parts between Cauca almaguer and San Jerónimo Faults. Geochemical analysis was performed on Arquia Complex metabasites (Sabaletas schist, Cauca river amphibole schist, Buesaco metamorphic sequence, Bugalagrande Group, Rosario Complex, Bolo azul Complex, Lisboa – Palestina schist and Santa Rosa metagabbro), corresponding to subalkaline tholeiitic basalts protolites type N-MORB with high magnesium, SiO2 between 44,24% and 53,49wt%, alkalis vs SiO2 0,03%- 0,09wt%, with Nb/Y=0,05-0,15 ratios and #Mg=45,03 – 72,34. The Arquia Complex ages are grouped into the two ranges: 100-113 Ma and 203-229 Ma. The first range (100-113 Ma) corresponded with radiometric ages obtained by K/Ar method, and coincide with the start stage of the Barroso- Sabanalarga Arc, affecting the suture zone and the two crusts, being interpreted as heating ages. The second range include ages between 203 – 229 Ma, obtained by Ar/Ar, and are interpreted as metamorphic age. These data are consistent with the age of metamorphism of the Cajamarca Complex, being this the basement of the Cordillera Central of Colombia.
Keywords
Arquia Complex, Age, Geochemistry, Complejo Arquía, Arquía, geoquímica, edad