TTE44

Relación magmática entre el cráter Navidad y Volcán Lonquimay, Zona …

ABSTRACT

The Lonquimay Volcanic Complex (LVC) is part of the Southern Andes Volcanic

Zone (SAVZ) and is made up of the Lonquimay stratovolcano (2,865 m.a.s.l) and a chain

of minor adventitious centers located along a fissure with NE-SW orientation called

Cordón Fisural Oriental (CFO), which records part of the historical eruptions of the CVL,

where the last eruptive activity associated with this cord corresponds to the one recorded on

December 25, 1988, which gave rise to Navidad cone.

In order to establish the magmatic relationship between the Navidad cone and

Lonquimay volcano, samples of the most recent lava flows from both volcanic edifices

were used for petrographic description and mineral chemistry analysis of the Lonquimay 5

and Navidad cone units. In addition, a geochemical analysis of major elements in rocks of

the Navidad cone and Lonquimay volcano was carried out. With the results obtained,

classification diagrams were made and clinopyroxene-liquid and two pyroxenes

thermobarometers were applied, according to the mineral phases analyzed.

According to the major element analysis, there is evidence of fractional crystallization

of plagioclase, olivine and clinopyroxene, where this process mainly controls magmatic

differentiation in the LVC. Likewise, the presence of reabsorption and decomposition

textures suggest a secondary role in the generation of magmas by the mixing of different

magmas.

Finally, the magmatic relationship between the Navidad cone and Lonquimay volcano

is established, because both edifices share similar mineralogy and textural characteristics,

suggesting that both are fed by the same storage zone at deep levels. However, according to

what was obtained, the magma ascent continues towards different magmatic chambers for

each volcanic edifice, where the Navidad cone would be associated to a storage zone at a

depth between 5 to 25 km and temperatures between 1019 - 1068°C, connected by dykes

and/or fissures and strongly controlled by the tectonics of the area. Thus, the interpretations

presented in this work would provide new background for the LVC.