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Title:: Metamorphic Characteristics and Tectonic Significance of Amphibolite of Guanghua Group in Tonghua Area of Jilin, China

Author(s):: ZHONG Ding-ding; ZHENG Chang-qing; LU Xiao-ping; ZHOU Xi-wen; XU Jiu-lei; ZHOU Xiao; SU Xun-xin; 1. College of Earth Sciences, Jilin University, Changchun 130061, Jilin, China; 2. Nuclear Industry Geological Bureau of Jilin Province, Changchun 130062, Jilin, China; 3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; 4. Geological Museum of Heilongjiang Province, Harbin 150090, Heilongjiang, China

Keywords:: amphibolite; metamorphism; phase equilibrium modeling; P-T path; Guanghua Group; island arc basalt; North China Craton; Jilin

Abstract:: There is a set of amphibolite from Shuangmiao Formation of Guanghua Group in Tonghua area of Jilin, which is located in the northern margin of North China Craton. The amphibolite is one of the major metamorphic rocks consisting of Precambrian metamorphic basement. The original rock of amphibolite mainly belongs to subalkaline basalt, which maybe form in the island-arc setting. The amphibolites undergo three stages of metamorphism, including prograde, peak and retrograde stages. Mineral assemblage at prograde stage is Gt₁+Hbl₁+Pl₁(the value of An is 13-16)+Q, and the pressure and temperature are 4.7-5.2 kbar and 544 ℃-555 ℃; mineral assemblage at peak stage is Gt₂+Hbl₂+Pl₂(the value of An is 28-31) +Ilm₂+Bt₂+Q, and the pressure and temperature are 8.1-8.8 kbar and 655 ℃-673 ℃; mineral assemblage at retrograde stage is Gt₃+Chl+Ath+Hbl₃+Bt₃+Ilm₃+Pl₃(the value of An is 16-18)+Q, and the pressure and temperature are 7.9-8.3 kbar and 546 ℃-557 ℃.The metamorphic evolution process of amphibolite shows the counterclockwise P-T path, which is characterized by near-isobar cooling (IBC) processes. It is suggested that there is a tectonic evolution from ArcheanPaleoproterozoic proto-ocean to collision of orogeny, and then orogenic taper, and the last magmatic undergrowth in Tonghua area of Jilin, China