期刊
INTERNATIONAL JOURNAL OF EARTH SCIENCES
卷 104, 期 1, 页码 27-44出版社
SPRINGER
DOI: 10.1007/s00531-014-1056-z
关键词
South Qinling; Neoproterozoic; Mafic dike; Geochemistry; Zircon age
资金
- Natural Science Foundation of China [41202140, 41372072]
- National Basic Research Program of China [2012CB416606]
- MOE Key Laboratory of Nuclear Resources and Environment, East China Institute of Technology [NRE1201]
Neoproterozoic volcanic-sedimentary sequences of the southern Qinling belt, central China, were intruded by voluminous mafic dikes. secondary ion mass spectrometry zircon U-Pb dating indicates that these dikes were emplaced at 650.8 +/- 5.2 Ma, coeval with mafic rocks occurring at the northern margin of the Yangtze block. The dikes are characterized by enrichment of large ion lithophile elements, high Ti contents (up to 3.73 wt%) and Nb/Ta ratios between 14.5 and 19.6, suggesting a mantle source of oceanic island basalt affinity. Initial Sr-87/Sr-86 ratios show positive correlation with SiO2 contents and negative correlation with Zr/Nb ratios, implying that these rocks were affected by crustal contamination during the magma ascend and emplacement process. The dikes have initial epsilon(Nd) values of +0.2 to +3.3, low Pb-206/Pb-204 ratios of 16.96-17.45, and moderate Sr-87/Sr-86 ratios of 0.7043-0.7076, likely pointing to the involvement of an enriched mantle source. The mafic dikes and coeval mafic volcanic equivalents in the South Qinling and the northern Yangtze are hypothesized to be related with the prolonged breakup of the supercontinent Rodinia, suggesting that continental rifting lasted until ca. 650 Ma.
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