期刊
CHEMICAL GEOLOGY
卷 409, 期 -, 页码 99-111出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.chemgeo.2015.04.021
关键词
Monazite; U-Pb; Petrochronology; Trace elements; Ultrahigh pressure; Norway
资金
- NSF [EAR-1050043, EAR-1219942, EAR-0911485]
- University of California, Santa Barbara
Monazite U-Pb and trace-element data were gathered from six high-to ultrahigh-pressure (UHP) samples from the Western Gneiss Region, Norway, using LASS (laser-ablation split-stream ICP-MS) to investigate variations in monazite composition during high-pressure metamorphism. The UHP monazites were found to contain up to 7600 ppm Sr, 110 ppm non-radiogenic Pb, relatively weak negative Eu anomalies, and Y concentrations as low as 500 ppm. Amphibolite-facies monazite that rims the UHP monazite in one sample contains Y concentrations up to 1.6 wt.%, Sr as low as 13 ppm, and no detectable non-radiogenic Pb. The UHP monazite composition (high Sr-Pb) is interpreted to result from growth in the absence of feldspar, possibly aided by increased compatibility of Sr-Pb-Eu2+ in the monazite crystal structure at high pressure. Sr in monazite as a proxy for feldspar stability may be a useful tool not only in studying high-pressure metamorphism, but also in determining timescales of melting and crystallization, when the amount of feldspar changes over time. (C) 2015 Elsevier B.V. All rights reserved.
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