Cr. Manley et al., Timing of volcanism in the Sierra Nevada of California: Evidence for Pliocene delamination of the batholithic root?, GEOLOGY, 28(9), 2000, pp. 811-814
Recent seismic experiments across the southern Sierra Nevada, California, s
how that the range lacks a thick crustal root. Xenolith studies indicate th
at delamination and loss of much of the lower crust may have occurred betwe
en 10 and 3 Ma. We estimate that delamination occurred ca. 3.5 Ma on the ba
sis of a sudden pulse of mafic potassic magmatism within and just east of t
he Sierra Nevada from 4 to 3 Ma. This pulse interrupted the low level of vo
lcanism that had prevailed regionally since 13 Ma. Delamination could have
promoted magmatism via decompression melting, heating of the shallow lithos
phere by upwelling asthenosphere, and foundering of crustal rocks into the
mantle, and could have provided dynamic support to the range. Foundering of
the lower crust may have occurred spontaneously, owing to negative buoyanc
y, or may have been triggered by extension between the Sierra Nevada and De
ath Valley.