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Ca . 1.7 Ga Magmatism on Southwestern Margin of the Yangtze Block: Response to the Breakup of Columbia
Author(s) -
GENG Yuansheng,
DU Lilin,
KUANG Hongwei,
LIU Yongqing
Publication year - 2020
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.14614
Subject(s) - gabbro , zircon , geology , geochemistry , magmatism , continental crust , crust , mantle (geology) , craton , magma , partial melting , petrology , igneous rock , tectonics , paleontology , volcano
Abstract This paper presents some data of the Jiaopingdu gabbro and Caiyuanzi granite at the southwestern margin of the Yangtze Block, on the geochemical compositions, zircon LA–ICP–MS U–Pb ages and Hf isotopic data. The Jiaopingdu gabbro gives the age of 1721 ± 5 Ma, the Caiyuanzi granite 1732 ± 6 Ma and 1735 ± 4 Ma, and the Wenjiacun porphyry granite 1713 ± 4 Ma, suggesting nearly contemporaneous formation time of the gabbro and granite. The bimodal feature is demonstrated by the gabbro SiO 2 content of 44.64–46.87 wt% and granite 73.81–77.03 wt%. In addition, the granite has high content of SiO 2 and Na 2 O + K 2 O, low content of Al 2 O 3 and CaO, enriched in REEs (except Eu) and Zr, Nb, Ga and Y, depleted in Sr, implying it belongs to A‐type granite geochemistry and origin of within‐plate environment. The zircon ∊ Hf ( t ) of the granite and gabbro is at the range of 2–6, which is near the 2.0 Ga evolution line of the crust, implying the parent magma of the gabbro being derived from the depleted mantle and a small amount of crustal material, and the parent magma of the granite from partial melting of the juvenile crust and some ancient crustal material at the same time. Compared with 1.8–1.7 Ga magmatism during breakup of other cratons in the world, we can deduce that the Columbia has initially broken since ca . 1.8 Ga, and some continental marginal or intra‐continental rifts occurred at ca . 1.73 Ga.