Zircon LA-ICP-MS U-Pb) analysis yields an age of 220.6 +/- 2.0Ma for the ultramafic rocks from Hongqiling, Jilin Province, NE China, indicating that these rocks were formed during Late Indochina stage. The rocks are characterized by low SiO(2) (43.22% similar to 44.48%), K(2)O (0.10% similar to 0.17%) and Na(2)O (0.15% similar to 2.13%) contents, high MgO(29.23% similar to 30.38%) and Mg(#) values (83 similar to 84), enrichment in LREE ((La/Yb)(N) = 1.95 similar to 2.61), large ion lithophile elements (LILEs, Rb and Sr) and Pb, depletion in the high field strength elements (HFSEs), such as NI), Ta, Zr and Ti, without significant Eu anomalies. In addition, the ultramafic rocks have low initial (87)Sr/(86)Sr ratios (0.70394 similar to 0.70408), positive epsilon(Nd)(t) (7.2 similar to 8.1) and epsilon(Hf)(t) values (9.6 similar to 14.4). Based on the above discussions, we proposed that the studied ultramafic rocks were derived from a depleted lithospheric mantle (garnet-lherzolite) source which was metasomatized by the fluid from the dehydration of the subducted oceanic (Paleo-Asian Ocean) sediments. When the primary magma ascent, obvious fractionation of olivine and clinopyroxene took place, significant crustal contamination, however, did not occur. Otherwise, tectonic and geodynamic investigation indicate that the studied ultramafic rocks were formed in a post-orogenic extensional setting after the collision between the Jiamusi block and North China Craton (NNC).

Publication name	ACTA PETROLOGICA SINICA　Volume:27 　Issue:6 　Pages:1594-1606 　Published:JUN 2011
Author(s)	Feng GuangYing; Liu Shen; Feng CaiXia; Jia DaCheng; Zhong Hong; Yu XiaoFei; Qi YouQiang; Wang Tao
Corresponding author	LIU Shen   fengguangying198@163.com,liushen@vip.gyig.ac.cn  Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Peoples R China

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