TY - JOUR
T1 - Multiple crustal melting pulses and Hf systematics in zircons
AU - Yu, Peng Peng
AU - Weinberg, Roberto F.
AU - Zheng, Yi
AU - Finch, Melanie A.
N1 - Funding Information:
We thank Vitor Barrote for assistance with Hf isotope reduction. This study is jointly funded by the National Natural Science Foundation of China ( 41902205 , 42022020 , 41872193 and 41972235 ), National Key Research and Development Program of China ( 2021YFC2900300 ), Natural Science Foundation of Guangdong Province ( 2018A030313144 , 2018B030306021 , 2016ZT06N331 and 2018B03031200 ) and the Fundamental Research Funds for the Central Universities, Sun Yat-sen University ( 2021qntd23 ). We thank Dr. Jun Wang for discussions in data treatment.
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/2
Y1 - 2022/2
N2 - This paper focuses on the U–Pb ages and Lu–Hf isotopes in zircons in a long-lived anatectic terrane, to understand both the nature of melting events and controls on Hf-isotope ratios in the zircon record. We focus on rocks from the Wuyi-Yunkai orogeny, South China, that mainly comprises Proterozoic basement rocks that generated numerous granitoids during Early Paleozoic granulite facies metamorphism. We investigate zircons from three anatectic granites and one migmatite. Zircon U–Pb dates for individual samples vary between ~465 and ~410 Ma, covering the duration of the orogeny. U–Pb dates for two samples define three normal distributions with populations spaced by ~15–20 Myr, indicating protracted and pulsed melting events. The inherited pre-orogenic zircon cores yield a wide spread of εHf(435) values (−39.0 to −2.8), whilst all Early Paleozoic, magmatic syn-orogenic cores and rims have a narrower range shifted to higher values ranging between −14.3 and + 5.5 and no systematic variation with the date of the analytical spot. The data suggest that the magmatic syn-orogenic zircons grew from isotopically heterogeneous melts with ~9 to 16 ε units variation for individual samples. The narrower ranges compared to the inherited cores suggest that some magma homogenization must have occurred, and the upward shift of the εHf(435) values is likely due to the influence of non-zircon Hf rather than due to mixing with an external less-evolved magma. Thus, the samples record a ~55 Myr, multi-pulsed melting event, during which heterogeneous crustal magmas had their Hf isotopic composition controlled by inherited zircon dissolution modified by contributions from non-zircon phase.
AB - This paper focuses on the U–Pb ages and Lu–Hf isotopes in zircons in a long-lived anatectic terrane, to understand both the nature of melting events and controls on Hf-isotope ratios in the zircon record. We focus on rocks from the Wuyi-Yunkai orogeny, South China, that mainly comprises Proterozoic basement rocks that generated numerous granitoids during Early Paleozoic granulite facies metamorphism. We investigate zircons from three anatectic granites and one migmatite. Zircon U–Pb dates for individual samples vary between ~465 and ~410 Ma, covering the duration of the orogeny. U–Pb dates for two samples define three normal distributions with populations spaced by ~15–20 Myr, indicating protracted and pulsed melting events. The inherited pre-orogenic zircon cores yield a wide spread of εHf(435) values (−39.0 to −2.8), whilst all Early Paleozoic, magmatic syn-orogenic cores and rims have a narrower range shifted to higher values ranging between −14.3 and + 5.5 and no systematic variation with the date of the analytical spot. The data suggest that the magmatic syn-orogenic zircons grew from isotopically heterogeneous melts with ~9 to 16 ε units variation for individual samples. The narrower ranges compared to the inherited cores suggest that some magma homogenization must have occurred, and the upward shift of the εHf(435) values is likely due to the influence of non-zircon Hf rather than due to mixing with an external less-evolved magma. Thus, the samples record a ~55 Myr, multi-pulsed melting event, during which heterogeneous crustal magmas had their Hf isotopic composition controlled by inherited zircon dissolution modified by contributions from non-zircon phase.
KW - Anatexis
KW - Granite
KW - Hf isotopic heterogeneity
KW - Intraplate orogen
KW - Non-zircon Hf
KW - Pulsed melting
UR - http://www.scopus.com/inward/record.url?scp=85122236275&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2021.106583
DO - 10.1016/j.lithos.2021.106583
M3 - Article
AN - SCOPUS:85122236275
SN - 0024-4937
VL - 410-411
JO - Lithos
JF - Lithos
M1 - 106583
ER -