Mihai N Ducea

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[1] Eclogites are commonly believed to be highly susceptible to delamination and sinking into the mantle from lower crustal metamorphic environments. We discuss the production of a specific class of eclogitic rocks that formed in conjunction with the production of the Sierra Nevada batholith. These high-density eclogitic rocks, however, formed by(More)
Xenoliths hosted by Cenozoic volcanic flows and plugs from the Central Sierra Nevada and Eastern Sierra Nevada, Owens Valley, and Inyo Mountains were studied for petrography and thermobarometry. The Central Sierra Nevada suite consists of abundant lower crustal feldspathic granulites, garnet clinopyroxenites, and mantle-derived peridotites and garnet(More)
Seismic data provide images of crust-mantle interactions during ongoing removal of the dense batholithic root beneath the southern Sierra Nevada mountains in California. The removal appears to have initiated between 10 and 3 Myr ago with a Rayleigh-Taylor-type instability, but with a pronounced asymmetric flow into a mantle downwelling (drip) beneath the(More)
The Pamir mountains are an outstanding example of extreme crustal shortening during continental collision that may have been accommodated by formation of a thick crust—much thicker than is currently thought—and/or by continental subduction. We present new petrologic data and radiometric ages from xenoliths in Miocene volcanic rocks in the southeastern Pamir(More)
[1] Garnet pyroxenites are the most common deep lithospheric xenolith assemblages found in Miocene volcanic rocks that erupted through the central part of the Sierra Nevada batholith. Elemental concentrations and isotope ratios are used to argue that the Sierra Nevada granitoids and the pyroxenite xenoliths are the melts and the residues/cumulates,(More)
Ganguly and Tirone [Meteorit. Planet. Sci. 36 (2001) 167^175] recently presented a method of determining the cooling rates of rocks from the difference between the core and bulk ages of a crystal, as determined by a single decay system. Here we present the first application of the method using the core and bulk ages of garnet single crystals, according to(More)
We present evidence for a thick ( 100 km) sequence of cogenetic rocks which make up the root of the Sierra Nevada batholith of California. The Sierran magmatism produced tonalitic and granodioritic magmas which reside in the Sierra Nevada upperto midcrust, as well as deep eclogite facies crust/upper mantle ma®c±ultrama®c cumulates. Samples of the(More)
[1] Xenoliths from Pali (Oahu, Hawaii) include samples of the mantle lithosphere underlying Koolau shield volcano. Most such xenoliths are spinel peridotites, the remainder being plagioclase-spinel peridotites, and garnet-free pyroxenites. Clinopyroxene separates from Pali peridotite xenoliths have relatively depleted Sr/Sr (0.70309–0.70346) and Nd/Nd(More)
Global compilations indicate that the geochemistry of arc magmatism is sensitive to Moho depth. Magmatic products are prevalent throughout the history of Cordilleran orogenesis and can be employed to constrain the timing of changes in crustal thickness as well as the magnitude of those changes. We investigate temporal variations in crustal thickness in the(More)
Drăguşanu and Tanaka (1999) provide intriguing new chemical and isotopic analyses of amphibolites and gneisses from the Cumpăna Group, the oldest lithostratigraphic unit in the Getic-Supragetic unit of the South Carpathians (Balintoni 1975; Pana 1994). Ten amphibolite whole-rock data points form a linear trend in a plot of measured Nd/Nd against Sm/Nd(More)