Crustal structure of the Arteaga Complex, Michoacan, southern Mexico, from gravity and magnetics

Abstract

The Arteaga region, Michoacan, southern Mexico is one of the few areas with basement outcrops in the Guerrero terrane. The Zihuatanejo subterrane is characterized by Late Jurassic-Early Cretaceous island-arc volcanosedimentary sequences that rest unconformably on metamorphosed rocks of the Arteaga Complex, of possible Triassic-Jurassic age. Gravity and total field magnetic measurements were taken along two SW -NE profiles across the metamorphic and igneous complex. Spectral analysis is used to estimate depths to the Moho and major crustal interfaces. The crustal thickness increases to theN and NE away from the margin and is in the order of 28-32 km. The metamorphic complex has an average thickness of 15 km. In the southern sector near Arteaga, the uppermost metamorphic units present a lower density contrast possibly due to regional alteration. The granitic and granodioritic batholith has a thickness of up to 8 km in the SE sector. The gravity and magnetic models are consistent with proposals that the Arteaga Complex constitutes the basement of the Zihuatanejo subterrane.