Geochronological constraints on the tectonic history of the Peninsular Ranges Batholith of Alta and Baja California: Tectonic implications for western Mexico

作者：Amabel Ortega‐Rivera · 发表于：Geological Society of America eBooks · 年份：2003 · DOI：10.1130/0-8137-2374-4.297 · 被引用次数：82 · 研究领域：Geological and Geochemical Analysis、Geochemistry and Geologic Mapping、Geological and Tectonic Studies in Latin America

A compilation of existing age data and new age determinations (U/Pb zircon, 4 0 Ar/ 3 9 Ar step-heating, K/Ar, Rb/Sr, and apatite fission-track dates) for the Peninsular Ranges batholith of Alta and Baja California provides geochronological constraints on the tectonic history of the Peninsular Ranges batholith and tectonic implications for western Mexico. The plutons of the Peninsular Ranges batholith ofAlta and Baja California between the 28°N and 34°N parallels were emplaced from west to east between ca. 140 to 80 Ma (U/Pb zircon dates) and display 4 0 Ar/ 3 9 Ar hornblende and biotite plateau dates that range from 118 to 83 Ma and 116 to 80 Ma, respectively, and biotite K/Ar dates as young as 65 Ma. Rapid cooling is indicated by the small differences in U/Pb zircon and cogenetic 4 0 Ar/ 3 9 Ar dates. Mineral pairs having mainly concordant dates yield 4 0 Ar/ 3 9 Ar cooling ages that also systematically decrease from southwest to northeast. Also, monotonic eastward younging of ages across various plutons was found as was previously reported for the Sierra San Pedro Martir pluton. This systematic regional and local eastward younging may be explained by the systematic tilting of pluton-sized crustal blocks containing individual plutons. The northeastward decrease in ages across the Peninsular Ranges batholith and across some of its plutons is therefore attributed to regional eastward migration of granitic intrusion foci combined with rapid differential exhumation histories an...