Two samples from the Uluguru granulite complex yield garnet Sm-Nd ages of 633 ± 7 and 618 ± 16 Ma, similar to previously published hornblende 40Ar-39Ar and K-Ar ages. The similarity of the Sm-Nd to the K-Ar age suggests that the closure temperature of garnet to Nd diffusion is similar to that of hornblende to Ar diffusion. Assuming that published zircon U-Pb ages of about 700 Ma date peak granulite-facies metamorphism, a mean post-metamorphic cooling rate of 2–3°C/Ma can be calculated for the time interval 700 to 630 Ma. Such slow cooling rates imply thermal relaxation with a thickness length-scale greater than the thickness of average continental crust. This, in turn, implies that the thermal perturbation responsible for metamorphism was preceded by regional crustal thickening probably in a collisional orogen.
@article{20150915164155-363703,
author = "Maboko, M. A. H. and Nakamura, E.",
title = "Sm-Nd garnet ages from the Uluguru granulite complex of Eastern Tanzania: further evidence for post-metamorphic slow cooling in the Mozambique belt",
journal = "Precambran Research",
year = "1995",
volume = "74",
pages = "195-202",
doi = "10.1016/0301-9268(95)00008-S",
}
caption | ID | rowname | stone | ||
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Table 1. Sm-Nd data pub | 20190905142040-489994 | Nd_(Maboko,1995) | 5 | ||