Premium
Geochronology of the Proterozoic basement of southwesternmost North America, and the origin and evolution of the Mojave crustal province
Author(s) -
Barth Andrew P.,
Wooden Joseph L.,
Coleman Drew S.,
Fanning C. Mark
Publication year - 2000
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/1999tc001145
Subject(s) - geology , gneiss , proterozoic , metamorphism , terrane , geochemistry , laurentia , allochthon , geochronology , basement , schist , archean , metamorphic facies , metamorphic rock , paleontology , facies , paleozoic , archaeology , tectonics , nappe , history , structural basin
The Proterozoic Baldwin gneiss in the central Transverse Ranges of southern California, a part of the Mojave crustal province, is composed of quartzofeldspathic gneiss and schist, augen and granitic gneiss, trondhjemite gneiss, and minor quartzite, amphibolite, metagabbro, and metapyroxenite. Sensitive high resolution ion microprobe (SHRIMP) data indicate that augen and granitic gneisses comprise a magmatic arc intrusive suite emplaced between 1783 ± 12 and 1675 ± 19 Ma, adjacent to or through thinned Archean crust. High U/Th rims on zircons in most samples suggest an early metamorphic event at ∼1741 Ma, but peak amphibolite facies metamorphism and penetrative, west vergent deformation occurred after 1675 Ma. The Baldwin gneiss is part of a regional allochthon emplaced by west vergent deformation over a Proterozoic shelf‐slope sequence (Joshua Tree terrane). We hypothesize that emplacement of this regional allochthon occurred during a late Early or Middle Proterozoic arc‐continent collision along the western margin of Laurentia.