SHRIMP‐RG U‐Pb Zircon Geochronology of Mesoproterozoic Metamorphism and Plutonism in the Southwesternmost United States

Mesoproterozoic intrusive and granulite‐grade metamorphic rocks in southern California have been inferred to be exotic to North America on the basis of perceived chronologic incompatibility with autochthonous cratonal rocks. Ion microprobe geochronology indicates that zircons in granulite‐grade gnei...

Full description

Saved in:
Bibliographic Details
Published in:The Journal of geology 2001-05, Vol.109 (3), p.319-327
Main Authors: Barth, Andrew P., Wooden, Joseph L., Coleman, Drew S.
Format: Article
Language:English
Subjects:
Anorthosite
Crystallization
Garnets
Geochronology
Geological time
Geology
Gneiss
Mesoproterozoic era
Metamorphism
Proterozoic eon
Regions
Rocks
Stone
Zoning
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Mesoproterozoic intrusive and granulite‐grade metamorphic rocks in southern California have been inferred to be exotic to North America on the basis of perceived chronologic incompatibility with autochthonous cratonal rocks. Ion microprobe geochronology indicates that zircons in granulite‐grade gneisses, dated at 1.4 Ga using conventional methods, are composed of 1.68–1.80‐Ga cores and 1.19‐Ga rims. These Early Proterozoic gneisses were metamorphosed at extremely high temperatures and moderate pressures during emplacement of the 1.19‐Ga San Gabriel anorthosite complex. The lack of a 1.4‐Ga metamorphic event suggests that Proterozoic rocks in this region, rather than being exotic to North America, may in fact be a midcrustal window into Mesoproterozoic crustal evolutionary processes in southwestern North America.
ISSN:0022-1376
1537-5269
DOI:10.1086/319975