3 research outputs found
Seismotectonics Characterization of Mexico
Mexico is an active Seismotectonic Region in the most part of North American continental plate and has 2 types of seismicity interplate and intraplate There are in the hierarchical structure 3 Seismotectonic Provinces North Western Western and Eastern Centre Inside they exist 11 Seismotectonic Units where the Seismogenic Zones are defined The last mentioned are segmented Western Province has the highest level and where the contact of the converging plates take plac
Geological and geochemical constraints on the early evolution of the Panama Arc
The Panama Arc formed following subduction initiation along the southwestern margin of the
Caribbean Oceanic Plateau in the Late Cretaceous. Evidence for the arc initiation upon the
oceanic plateau basement is preserved in uplifted segments of the forearc basement across
southern Central America. Despite subduction initiation being one of the most significant
processes of the plate tectonic cycle, it remains the most poorly understood, and the unique
geological record of Panama and nearby Costa Rica and Colombia provides a valuable
opportunity to investigate magmatic and tectonic processes in a nascent subduction zone.
This study uses field observations, biostratigraphic dating, whole-rock geochemistry and Nd
isotope geochemistry to investigate the nature of the plateau basement and the first
magmatic products of subduction initiation across a ca. 650 km transect from western
Panama to northwest Colombia.
New results reveal that the oceanic plateau across this region is
lithostratigraphically and geochemically heterogeneous. Similar to the bulk of the Caribbean
Oceanic Plateau, the studied plateau sequences were sourced from a heterogeneous
mantle plume likely associated with the initiation of the Galapagos hotspot in the Late
Cretaceous. Earlier magmatic phases of the oceanic plateau in Panama and nearby
Colombia are possible, but remain poorly documented in the studied area. In addition, this
study provides a new insight into subduction initiation along the oceanic plateau with the
recognition of two compositionally distinct ‘proto-arc’ groups. An early proto-arc magmatic
phase includes sequences of pillow basalts, basaltic dykes and gabbroic intrusions that
were formed from a plume-like source and are geochemically transitional between plateau
and mature arc sequences. The second proto-arc phase is represented by basaltic dykes,
locally crosscutting plateau and early proto-arc sequences, which have more depleted
geochemical signature, and were produced from a MORB-like source with variable slab
input. These proto-arc groups are separated from the plateau by a regional limestone
formation that indicates cessation of plateau magmatism ca. 5-10 Myr prior to subduction
initiation in the Campanian (ca. 72-73 Ma). Existing geochronological data and new results
indicate that the establishment of a mature arc from the onset of supra-subduction
magmatism took less than ca. 4 Myr.
Overall, this study shows that igneous complexes of Panama and Colombia represent a
novel record of subduction initiation which does not follow previous models of plume induced subduction initiation in Central America or spontaneous subduction initiation along
the Izu-Bonin-Mariana Arc system. New and previous regional constraints suggest instead ii
that subduction initiation in Panama most likely occurred due to propagation of an east- to
north-facing subduction zone along the southern margin of the oceanic plateau during its
collision with the South American continent