Discussions on Mafic-Ultramafic Rocks and Eclogites in Dabie Orogen, Central China
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P588.242 P588.3

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    Abstract:

    On the bases of recent researches and recent references, this paper mainly discusses the origin and evolution of mafic-ultramafic rocks and eclogites occurring in high pressure-ultrahigh pressure metamorphic belt, Dabie orogen. Systematic studies of petrology and geochemistry indicate that the mafic-ultramafic rocks in this region can be divided into two types. The mafic-ultra-mafkites of the first type, with similar geological characteristics and Sm-Nd age, are represented by Zhujiapu, Renjiawan and Tongjiachong gabbro intrusions in the northern Dabie erogenic belt, which are possibly associated with basaltic magmas from the island arc or continental mantle e-volved from the collision between the North China and Yangtze blocks. On the contrary, those of the second type with different rock-forming ages and environments are almost of the Precam-brian, derived from either continental mantle slices such as Naobozhai harzburgites or the differentiation of basaltic magmas in layered intrusions such as the Maowu and Bixiling peridotites. E-clogites in the Dabie HP-UHP metamorphic belt are not dominantly originated from their country rocks but produced from complicated protoliths with various isotopic ages. However, the fact that their metamorphic ages are concentrated in the Indosinian (197~246 Ma) suggests that all these eclogites experienced the same tectonic event of subduction-collision between the North China and Yangtze blocks. The evaluated formation depths (32. 05 - 32. 11 km) of coesite-bearing eclogites presented by Lu et al. (1998), we believe, are more reasonable than previous data of over 100 km in interpreting the exhumation of HP-UHP metamorphic rocks.

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Kuang Shaoping, Ling Wenli, Zhang Benren.1999. Discussions on Mafic-Ultramafic Rocks and Eclogites in Dabie Orogen, Central China[J]. Geological Review,45(6):584-595.

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