Nd isotopic composition of cratonic rocks in the southern Death Valley region: Evidence for a substantial Archean source component in Mojavia

Thirty Early Proterozoic intermediate to silicic metasedimentary and metaigneous rocks in the southern Death Valley region and vicinity show ϵ_Nd values of −1.6 to −6.3 at 1.7 Ga and Nd model ages of 2.1 to 2.6 Ga. These cratonic rocks thus reveal an older signature than so far reported for Nd province 1 of the western United States; as much as 30%–40% of their mass may be Archean crustal material. The Archean component was introduced in the form of sedimentary detritus that was probably subducted and mixed with juvenile material at a convergent margin. Three younger Precambrian rocks associated with the cratonic rocks also have a Nd isotopic composition of province 1 type.