Impact Factor:4.02
DOI number:10.1061/j.lithos.2020.105891
Affiliation of Author(s):地信院
Teaching and Research Group:地质资源系
Journal:Lithos
Place of Publication:NORWAY
Funded by:深地研发2018YFC0603902；中国地调局1212011121116 & 1212011085372
Key Words:Fractional crystallization Intraplate orogeny I-type granitoids Sr–Nd isotopes Zircon U–Pb dating
Abstract:The Early Paleozoic Wuyi–Yunkai orogeny in the South China Block (SCB) remains enigmatic. A geochemical and geochronological investigation was carried out for the four poorly-studied granitoid intrusions (i.e., Hongxiaqiao, Xuehuading, Baimashan and Wanyangshan granitoids) in Hunan Province, and within the SCB, to determine their petrogenesis and give enlightening insights into the tectonic evolution of the Wuyi–Yunkai Orogen. The Hongxiaqiao, Xuehuading and Baimashan granitoids have lower SiO2 contents, and total alkali (Na2O + K2O) and A/CNK values, but higher Fe2O3 T, MgO and TiO2 contents, compared with those of the Wanyangshan granitoid. All the studied granitoids are strongly depleted in Ba, Nb, Zr, Ti, and HREEs, but are enriched in Rb, Th, U, K, and LREEs, with significant negative Eu anomalies, particularly in the Wanyangshan granitoid. Bulk-rock geochemical compositions indicate that the Hongxiaqiao, Xuehuading and Baimashan granitoids are metaluminous–weakly peraluminous I-type granitoids, whereas the Wanyangshan granitoid is peraluminous and moderately fractionated S-type granitoid. Zircon LA-ICP-MS U–Pb dating results indicate that the Hongxiaqiao, Xuehuading, Baimashan and Wanyangshan granitoids were intruded at 451 ± 1 Ma (MSWD = 1.8), 412 ± 1 Ma (MSWD = 2.4), 415 ± 1 Ma (MSWD = 3.0) and 445 ± 1 Ma (MSWD = 3.9), respectively. The I-type granitoids have variable initial 87Sr/86Sr values of 0.71160–0.72362, high εNd(t) values (−6.5 to −8.1), and young T2DM ages of 1717–1894 Ma. In contrast, the S-type granitoid has consistent initial 87Sr/86Sr values of 0.71448–0.71887, slightly lower εNd(t) values (−9.8 to −10.3), and older T2DM ages (1977–2015 Ma), which suggests that they were derived from partial melting of different Paleoproterozoic basement rocks, without significant crustal contamination. The older Hongxiaqiao and Wanyangshan granitoids were formed in a compressional setting, whereas the younger Xuehuading and Baimashan granitoids were generated in a post-orogenic extensional setting. Integrated with geological evidence, we proposed that the Early Paleozoic Wuyi–Yunkai orogeny in the SCB resulted from intraplate orogenesis triggered by far-field tectonic response to the assembly of the northern East Gondwana, rather than from oceanic subduction–collision.
Indexed by:Article
Document Code:105891
Discipline:Natural Science
First-Level Discipline:Geology
Volume:380-381
Translation or Not:no
Included Journals:SCI