TY - JOUR
T1 - U-Pb and Hf isotopic analysis of zircon in lower crustal xenoliths from the Navajo volcanic field
T2 - 1.4 Ga mafic magmatism and metamorphism beneath the Colorado Plateau
AU - Crowley, James L.
AU - Schmitz, Mark D.
AU - Bowring, Samuel A.
AU - Williams, Michael L.
AU - Karlstrom, Karl E.
PY - 2006/3
Y1 - 2006/3
N2 - Zircon from lower crustal xenoliths erupted in the Navajo volcanic field was analyzed for U-Pb and Lu-Hf isotopic compositions to characterize the lower crust beneath the Colorado Plateau and to determine whether it was affected by ∼1.4 Ga granitic magmatism and metamorphism that profoundly affected the exposed middle crust of southwestern Laurentia. Igneous zircon in felsic xenoliths crystallized at 1.73 and 1.65 Ga, and igneous zircon in mafic xenoliths crystallized at 1.43 Ga. Most igneous zircon has unradiogenic initial Hf isotopic compositions (εHf=+4.1-+7.8) and 1.7-1.6 Ga depleted mantle model ages, consistent with 1.7-1.6 Ga felsic protoliths being derived from "juvenile" Proterozoic crust and 1.4 Ga mafic protoliths having interacted with older crust. Metamorphic zircon grew in four pulses between 1.42 and 1.36 Ga, at least one of which was at granulite facies. Significant variability within and between xenoliths in metamorphic zircon initial Hf isotopic compositions (εHf =-0.7 to +13.6) indicates growth from different aged sources with diverse time-integrated Lu/Hf ratios. These results show a strong link between 1.4 Ga mafic magmatism and granulite facies metamorphism in the lower crust and granitic magmatism and metamorphism in the exposed middle crust.
AB - Zircon from lower crustal xenoliths erupted in the Navajo volcanic field was analyzed for U-Pb and Lu-Hf isotopic compositions to characterize the lower crust beneath the Colorado Plateau and to determine whether it was affected by ∼1.4 Ga granitic magmatism and metamorphism that profoundly affected the exposed middle crust of southwestern Laurentia. Igneous zircon in felsic xenoliths crystallized at 1.73 and 1.65 Ga, and igneous zircon in mafic xenoliths crystallized at 1.43 Ga. Most igneous zircon has unradiogenic initial Hf isotopic compositions (εHf=+4.1-+7.8) and 1.7-1.6 Ga depleted mantle model ages, consistent with 1.7-1.6 Ga felsic protoliths being derived from "juvenile" Proterozoic crust and 1.4 Ga mafic protoliths having interacted with older crust. Metamorphic zircon grew in four pulses between 1.42 and 1.36 Ga, at least one of which was at granulite facies. Significant variability within and between xenoliths in metamorphic zircon initial Hf isotopic compositions (εHf =-0.7 to +13.6) indicates growth from different aged sources with diverse time-integrated Lu/Hf ratios. These results show a strong link between 1.4 Ga mafic magmatism and granulite facies metamorphism in the lower crust and granitic magmatism and metamorphism in the exposed middle crust.
UR - http://www.scopus.com/inward/record.url?scp=33645574521&partnerID=8YFLogxK
U2 - 10.1007/s00410-006-0061-z
DO - 10.1007/s00410-006-0061-z
M3 - Article
AN - SCOPUS:33645574521
SN - 0010-7999
VL - 151
SP - 313
EP - 330
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
IS - 3
ER -