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The growth interval of garnet in the UHP eclogites from the Dabie orogen, China

Cheng Hao, Jeffrey D. Vervoort, Li Xianhua, Zhang Chao, Li Qiuli and Zheng Shu
The growth interval of garnet in the UHP eclogites from the Dabie orogen, China
American Mineralogist (August 2011) 96 (8-9): 1300-1307


Zircon inclusions, extracted from garnet from an ultrahigh-pressure eclogite in the eastern part of the Dabie orogen, were investigated with high spatial resolution U-Pb geochronology. The unzoned zircon rims have garnet and omphacite inclusions and show weak cathodoluminescence, low-Th/U ratios (0.02-0.18), flat high rare-earth elements patterns, and an absence of Eu anomalies, which suggest metamorphic growth in the presence of garnet and in the absence of feldspar. Dispersed concordia U-Pb ages, ranging from 205.1+ or -3.3 to 255.3+ or -6.1 Ma, defined a weighted mean (super 206) Pb/ (super 238) U age of 223+ or -8 Ma (mean square of weighted deviation, MSWD=38), which is significantly younger than the Lu-Hf garnet-whole rock age of 242.2+ or -2.6 Ma. The U-Pb age probability distribution indicates two age populations at ca. 241 and ca. 216 Ma. The zircon rims, with younger ages, are distinguished from those with older ages by the occurrence of garnet and omphacite inclusions. Well-preserved prograde major- and trace-element zoning in garnet and the significant contribution of older garnet cores in bulk isotopic digestion suggest that the Lu-Hf age mostly reflects an early phase of garnet growth likely at amphibolite facies conditions. The new Lu-Hf age combined with the U-Pb ages of the zircon inclusions in garnet suggest that garnet growth was sustained over a time interval of approximately 25 m.y.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 96
Serial Issue: 8-9
Title: The growth interval of garnet in the UHP eclogites from the Dabie orogen, China
Affiliation: Tongji University, Laboratory of Marine Geology, Shanghai, China
Pages: 1300-1307
Published: 201108
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 49
Accession Number: 2011-076472
Categories: Igneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N30°00'00" - N32°00'00", E114°00'00" - E117°00'00"
Secondary Affiliation: Washington State University, USA, United StatesChinese Academy of Sciences, Institute of Geology and Geophysics, CHN, ChinaChina University of Geosciences, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201142
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