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Ca. 1.7 Ga Magmatism on Southwestern Margin of the Yangtze Block: Response to the Breakup of Columbia
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2020-12-09 , DOI: 10.1111/1755-6724.14614
Yuansheng GENG 1 , Lilin DU 1 , Hongwei KUANG 1 , Yongqing LIU 1
Affiliation  

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 SiO2 content of 44.64–46.87 wt% and granite 73.81–77.03 wt%. In addition, the granite has high content of SiO2 and Na2O + K2O, low content of Al2O3 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.

中文翻译:

钙 1.7扬子地块西南缘的Ga岩浆作用:对哥伦比亚破裂的反应

本文介绍了扬子地块西南缘的焦坪渡辉长岩和菜园子花岗岩的一些数据,包括地球化学组成,锆石LA-ICP-MS U-Pb年龄和Hf同位素数据。焦坪渡辉长岩的年龄为1721±5 Ma,菜园子花岗岩的年龄为1732±6 Ma和1735±4 Ma,而文家村斑岩花岗岩的年龄为1713±4 Ma,表明辉长岩和花岗岩的形成时间接近同期。双峰特征由辉长岩SiO 2含量为44.64–46.87 wt%和花岗岩73.81–77.03 wt%证实。另外,该花岗岩具有高含量的SiO 2和Na 2 O + K 2 O,低含量的Al 2 O 3CaO富含REE(Eu除外),Zr,Nb,Ga和Y富含Sr,表明它属于A型花岗岩地球化学和板内环境的起源。花岗岩和辉长岩的锆石Hft)处于2–6的范围内,接近地壳的2.0 Ga演化线,这意味着辉长岩的母岩浆来自贫化的地幔和少量地壳物质和花岗岩的母岩浆同时来自幼年地壳和某些古老地壳物质的部分融化。与世界其他克拉通解体过程中1.8-1.7嘎岩浆活动相比,我们可以推断,哥伦比亚已经初步打破以来CA。1.8 Ga和一些大陆边缘或帧内大陆裂谷发生在CA。1.73 Ga。
更新日期:2020-12-29
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