Publication Date:
2018-03-30
Description:
Magmatism and faulting operate and interact in continental rifts at a variety
of scales. The East African Rift, an example of an active magmatic continental
rift, provides the ideal location to study the interplay between these
two mechanisms. Previous work has shown that the distribution of volcanic
vents and the shape of volcanic fields are linked to their tectonic environment
and their magmatic system. In order to distinguish the impact of each mechanism,
we analyzed four distinct volcanic fields located in the Main Ethiopian
Rift; three of them (Debre Zeyit, Wonji, and Kone) are located within the rift
valley, and one (Akaki) lies on the western rift shoulder. The elongation and
shape of each field were analyzed based on their vent distribution using three
statistical methods: the principal component analysis, the vent-to-vent distance,
and the two-dimensional, symmetric Gaussian kernel density estimation
method. The results of these analyses show that the elongations of the
fields increase from the western shoulder toward the rift axis and are inversely
proportional to their angular dispersion. In addition, we observed that none
of the analyzed fields have elongation that parallels either the trends of the
youngest faults or the volcano alignments. Dike intrusions inferred from the
alignment analysis of volcanic centers that are located within the rift axis tend
to parallel the orientation of the recent active faults. This parallelism, however,
decreases from the rift axis toward the rift shoulder, which has a lower strain
rate and shows a larger number of preexisting fault orientations. Our results
suggest that the shape of volcanic fields in the Main Ethiopian Rift is controlled
mainly by large crustal structures and/or by the lithosphere-asthenosphere–
boundary geometry. Diking is principally controlled by the location
of the field within the rift zone; intrusions within the rift zone are controlled
mostly by the state of stress and strain rate; while intrusions on the rift shoulder
are controlled mostly by the presence of preexisting fractures.
This study provides a combination of statistical analyses and geological
observations to study and differentiate the mechanisms involved in the formation
of volcanic fields on Earth and, potentially, other planets.
Description:
Published
Description:
706–720
Description:
7T. Struttura della Terra e geodinamica
Description:
1V. Storia eruttiva
Description:
2V. Struttura e sistema di alimentazione dei vulcani
Description:
JCR Journal
Keywords:
COntinental rift, deformation, structure, volcanism
;
Volcanic field shape in continental rifts, magma emplacement and deformation
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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