Decoding magma plumbing and geochemical evolution of active volcanoes of the Central Andes (North Chile) with petrological methods Lascar Lastarria magma plumbing system andesite magmatic differentiation magma mixing geothermobarometry pre eruptive condtions. Magmatisches Fördersystem Andesit magmatische Differenzierung Geothermobarometrie präeruptive Bedingungen