• 责任者：Guan Yili (State Key Laboratory of Isotope Geochemistry ; Guangzhou Institute of Geochemistry ; CAS ; Guangzhou 510640 ; China) ; Yuan Chao
• 刊名：Geotectonica et Metallogenia
• 出版年：2013
• 卷期：37(4)
• 关键词：I型花岗岩 ; I-type granite ; 大陆构造 ; continental tectonics ; 华南地区 ; South China
• 页码：p.698-720
• 图表：12 illus., 2 tables, 202 refs.
• 分类号：0801
• issnNo：ISSN1001-1552
• isbnNo：CN44-1595/P

     The early Paleozoic intracontinental orogenic belt in the eastern South China Block is characterized by not only intensive deformation and metamorphism, but also extensive granitic magmatism. Granites in the eastern South China Block are predorninately peraluminous S-type granites, and I-type granites are rare. Uncertainties remain for the petrogenesis of the I-type granitic intrusions in the area, especially the role of the mantle. Two representative granodioritic plutons in southeastern Yangtze Block, namely, the Banshanpu and Hongxiaqiao plutons were selected for LA-ICP-MS zircon dating and geochemistry analysis. The results indicated that the Banshanpu and Hongxiaqiao plutons were emplaced at 432.4~2.6 Ma and 434.3i2.7 Ma respectively, right on the peak time （434 Ma） of the early Paleozoic magmatism in South China Block. The Banshanpu pluton has high K20 （2.71%-3.46 %） and AI203 （15.17%-15.59%） contents with high Sr/Y（34-47） ratios, similar to adakitic rocks. The low eNd（t） （-7.5--6.9） values, high 87Sr/86Sri （0.7130-0.7169） ratio and old tDM2 （ 1729-- 1776 Ma） indicate an origination of thickened Paleoproterozoic lower crust. In contrasting, the Hongxiaqiao pluton has relatively low SiO2 （64.40%-65.42%） content, higher TiO2 （0.58%-0.63%）, Fe203（4.48%-4.79%）, CaO （3.34%~4.39%）, MgO （2.55%~3.06%） and Y （14.56~10-6-17.82x10 6） contents and lower Sr/Y （20-24） ratios. Sr-Nd isotopes （87Sr/86Sri =0.7142-0.7149, eNd（t）=--7.7----7.3） of the Hongxiaqiao pluton are similar to those of the Banshanpu pluton, suggesting a similar source（s）. Unlike S-type granites, petrogenesis of I-type granite requires extra heat to fuse the lower crust source. The post-orogenic collapse after intracontinental peak-metamorphism （444 Ma） led to the upwelling of the asthenosphere, which provided enough heat for partial melting of the source rocks, but the asthenosphere did not provide material for the granitic rocks. It is most likely that the upwelling of asthenosphere created the early Paleozoic intracontinental orogenic belt in Southern China Block.