Sm nd dating garnet Yahoo sex chat room usa

In understanding metamorphic rocks, Lu–Hf can still provide information of origin.In cases where zircon phase is absent or very low in abundance, such as eclogite with cumulate protolith, kyanite and orthopyroxene eclogites can be candidate for Hf analysis.Although the overall rare-earth element concentration is low is the two eclogites, Lu/Hf ratios is high, therefore enabling concentration determination of Lu and Hf.

The samples belong to the metamorphic core complex, Valhalla, British Columbia, and the mid-crustal magmatic arc exposure of the Salinian terrane, California.In one amphibolite, P-T studies indicate a single stage of metamorphism with final equilibration at ˜600°C and 8 9 kbar.The Sm-Nd isotopic compositions of plagioclase, apatite, hornblende, and garnet define a precise, 8-point isochron of 128±3 Ma (MSWD=1.2) interpreted as mineral growth at the metamorphic peak.The Salinian sample, on the other hand, yields indistinguishable core (78.2±2.7 Ma) and bulk (77.9±2.9 Ma) ages, as expected from its fast cooling history, which can be constrained by the results of earlier studies.The Sm-Nd decay system in garnet has relatively high closure temperature (usually 650°C); therefore, the technique developed in this paper fills an important gap in thermochronology, since the commonly used thermochronometers are applicable only at lower temperatures.

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