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Preliminary descriptions of the Zihuatanejo stratigraphy defined the Zihuatanejo Formation and the Las Ollas Complex (Vidal–Serratos, 1986; Talavera–Mendoza and Guerrero–Suástegui, 2000). The former was described as a 1,500 m–thick succession of andesite to dacite lava flows and volcaniclastic turbidites, interpreted to represent an intraoceanic arc (Vidal–Serratos, 1986; Talavera–Mendoza and Guerrero–Suástegui, 2000), capped by Albian limestone (Ixtapa member, Vidal–Serratos, 1986) interstratified with red beds (La Unión member, Vidal–Serratos, 1986) (Figure 2 and Table 1). Additionally, Vidal–Serratos (1986) recognized a succession of conglomerate and sandstone (Posquelite member) at the base of the Zihuatanejo Formation (Figure 2 and Table 1). The conglomerate is composed of clasts of deformed two–mica metagranite, quartzite, and gneiss (Vidal–Serratos, 1991). Similarly, Centeno–García et al. (2003) interpreted the Zihuatanejo Formation as an arc succession composed of andesitic lava flows, tuff and shallow marine volcaniclastic turbidite–like deposits. However, these authors pointed out that these rocks apparently overlie the Albian limestone of the Ixtapa member, and not vice versa as previously proposed. More recently, a main peak age at 85 Ma was reported for detrital zircons from a sandstone of the Zihuatanejo Formation (Talavera–Mendoza et al., 2007), which confirmed that these rocks are younger than the Albian carbonate strata. Previous authors inferred that the Zihuatanejo Formation is thrust over the Las Ollas Complex (Vidal–Serratos, 1986; Talavera–Mendoza, 2000), which consists of quartz–rich metaturbidites, locally containing blocks and slabs of pillow basalt, banded gabbro, amphibolite, chert, limestone, quartzite, tuff and partly to wholly serpentinized ultramafic rocks (Vidal–Serratos, 1986; Talavera–Mendoza, 2000). Talavera–Mendoza (2000) also reported a blueschist paragenesis for these rocks at Puerto Vicente Guerrero (Figure 1a), indicating P–T conditions of 5–7 kbars and 200–330 °C. Based on the block–in–matrix structure, the geochemistry of the mafic blocks and the blue–schist metamorphism, Talavera–Mendoza (2000) interpreted these rocks as the accretionary prism of the Cretaceous Zihuatanejo intraoceanic arc. However, the youngest U–Pb ages of detrital zircons from the Las Ollas metaturbidites are ~376 Ma (Talavera–Mendoza et al., 2007), implying that the Las Ollas Complex is much older than the Cretaceous Zihuatanejo Formation. Similar polideformed greenschist to amphibolite metamorphic rocks, which enclose blocks of pillow basalt, banded gabbro, chert, and limestone, have been grouped into the Arteaga Complex by Centeno–García et al. (1993). This complex is exposed in the Arteaga region, ~60 km NW of study area (Figure 1a), and has been interpreted as an Upper Triassic accretionary prism, constituting the basement of the Zihuatanejo terrane (Centeno–García et al., 1993; Centeno–García et al., 2008).