Las Cabras volcano, Michoacan-Guanajuato Volcanic Field, Mexico: Topographic, climatic, and shallow magmatic controls on scoria cone eruptions
Por:
Guilbaud, Marie-Noelle, Hernandez-Jimenez, Athziri, SIEBE, CLAUS, Salinas, Sergio
Publicada:
1 ago 2021
Categoría:
Geology
Resumen:
Scoria cones are abundant in most volcanic fields on Earth, such as the
Michoacan-Guanajuato Volcanic Field, in the central-western sector of
the Trans-Mexican Volcanic Belt. However, there are few in-depth studies
on their eruptive style and controlling factors, despite of their
diversity in shape and composition which implies a wide range of
hazards. Here, we present results of morphologic, stratigraphic,
sedimentary, petrographic, and geochemical studies of the prominent Las
Cabras scoria cone located west of the Zacapu lacustrine basin in the
center of the Michoacan-Guanajuato Volcanic Field. This basaltic
andesitic to andesitic volcano formed between 27 and 26 kyrs BP on the
steep slopes (>10 degrees) of the lava shield of El Tule volcano. Over
time, its dominant eruptive style changed from Strombolian to effusive.
Initial explosive activity built a 170-m-high scoria cone and deposited
thick tephra fallout on the surrounding sloping terrain. Structures in
the deposits indicate that early friable fine-grained tephra underwent
significant erosion due to syn-eruptive heavy rain coupled with the
sloping nature of the underlying ground. This erosion generated lahars
that very likely reached the Zacapu lake based on the pre-eruptive
topography. As the explosivity dropped, lava was emitted from the base
of the cone first to the S and SE, forming a thick, viscous lobe that
filled a pre-existing E-W valley. The flow direction then deviated to
the N and NE, to form thinner, less-viscous lobes fed from the vent by
an open-channel. The lavas are covered by hummocks made of agglutinates
and bombs that indicate that the eruption terminated by catastrophic
collapse of the SE sector of the cone, possibly triggered by the
intrusion of magma within the cone, which destabilized its downslope
segment. The sudden flank failure was potentially associated with a late
effusive event and the hummocks may have been carried away by the lava
surge. Whole-rock chemical variations and crystal disequilibrium
textures point toward a complex magma feeding system, involving mixing
and mingling between different magma batches. This study shows that the
formation of scoria cones on a terrain with a marked slope (>10 degrees)
has profound impacts on the eruption dynamics and related hazards due to
its effect on cone stability and ash erosion. It also evidences the
erosive effect of syn-eruptive rain on fine-grained tephra, especially
when deposited on a slope. Finally, it reveals the complex magmatic
processes that may occur in the shallow plumbing system of monogenetic
andesitic volcanoes, which could be particularly important in inland
areas of continental arcs.
Filiaciones:
Guilbaud, Marie-Noelle:
Univ Nacl Autonoma Mexico, Inst Geofis, Dept Vulcanol, Ciudad Univ, Mexico City 04510, DF, Mexico
Hernandez-Jimenez, Athziri:
Univ Nacl Autonoma Mexico, Fac Ciencias, Ciudad Univ, Mexico City 04510, DF, Mexico
SIEBE, CLAUS:
Univ Nacl Autonoma Mexico, Inst Geofis, Dept Vulcanol, Ciudad Univ, Mexico City 04510, DF, Mexico
Salinas, Sergio:
Univ Nacl Autonoma Mexico, Div Ingn Ciencias Tierra, Fac Ingn, Ciudad Univ, Mexico City 04510, DF, Mexico
gold, All Open Access; Gold
|