Geochemistry of paleozoic basalts from the Juchatengo complex of southern Mexico: tectonic implications |
| |
| Authors: | J M Grajales-Nishimura E Centeno-Garcia J D Keppie J Dostal |
| |
| Institution: | a Instituto de Geología, Universidad Nacional Autónoma de México, 04510, México D.F., Mexico;b Department of Geology, St. Mary’s University, Halifax, Nova Scotia, Canada, B3H 3C3 |
| |
| Abstract: | Analyses of Lower Permian or older basalts and associated dykes of the Juchatengo sequence indicate that they are rift tholeiites that formed in a continental rift or back-arc tectonic setting. Age constraints include a Middle Permian fossil recovered from the tectonically overlying sediments and a cross-cutting, post-tectonic pluton dated by K/Ar on hornblende at 282±6 Ma. A location adjacent to the Oaxacan Complex or other old continental crust is suggested by (1) an  Ndi isotopic value of −8.95 and a TDM age of 1487 Ma in the overlying sediments, which are similar to the Oaxacan Complex; (2) enrichment of incompatible elements in the lavas, suggesting old crustal contamination; and (3) the presence of Permian–Triassic calc-alkaline plutons that stitch the Juchatengo–Oaxaca boundary. The possible tectonic models depend on the age of the Juchatengo basalts, which requires future geochronological work. If the Juchatengo basalts are Permo-Carboniferous, they could have formed near the eastern edge of a back-arc basin: the contemporaneous arc would have rifted away to the west. Eastward migration of the arc magmatism indicated by the Permian–Triassic calc-alkaline plutonism may reflect shallowing of the dip of the subduction zone, which probably also produced the deformation of the Juchatengo sequence. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
