The Material Composition, Metamorphism And Deformation Of Huanan Lift In Eastern Heilongjiang Province

Huanan Lift, as the important part of Jiamusi block (JB), is situated in the eastern Heilongjiang province and in the middle segment of JB. To the north of it is Sanjiang basin and to the south of it is Boli basin. It is near to Wandashan terrane bordered with Tongjiang-Dangbi fault belt in the east and near to Khanka block bordered with Dunhua-Mishan fault belt in the southeast. In the west, the margin of HL is controlled by Jia-Yi fault belt.Since many years ago, the researches about the eastern Heilongjiang focus on the property and tectonic evolution of JB, but HL, as the biggest geological unit of outcropped metamorphic basement has never been done systemic and detailed work. Considering about the special tectonic position of HL in JB, and the development of entire metamorphic lithologic association, we choose"the material composition, metamorphism and deformation of Huanan Lift in eastern Heilongjiang"as the theme topic in order to open out the metamorphism and tectonic evolution of HL. from this research, then we can get better understood the evolution of JB.The research about JB has been lasting from 1926, until 1980s, the research about metamorphic rocks has been developed fast. Researchers carried on studies about the metamorphic facies, metamorphic facies system that correlated with the tectonic setting and tectonic evolution. They also carried on researches about petrologic origin and isotope geochronology. They achieved opinions about JB as follows: JB is the microblock which divided from the north china plate (Xu etc, 1986); the block is the residual of blocks　 divided from Jihei block (Ren, 1988, 1990) and the granite-greenstone belt (Zhao etc, 1986, 1996; Liu, 1988, 1991). In 1990s, through studies on metamorphic rocks of originic Heilongjiang group, Cao (1992), Zhang (1992) and Li (1999) discovered that in the Heilongjiang Group there existed rocks with the combination of dismembered ophiolite suite and low T and high P metamorphic mineral—sodium amphibole, they also found fadiolarian chert (Zhang, 1992)and chitinozoa fossil-beared phyllite (Li, 1999)in the rocks, which appearance proved that the originic Heilongjiang group is not normal metamorphic strata but the tectonic mélange having the the property of collision belt. It is the accretionary complex developed during the collision between JB and adjacent block or between its interior microblocks. (Zhang, 1992; Li, 1999; Cao, 1992). So far, the views about the property and the ascription of JB began to unify.From the research work, we find that there are three rock series: outcropped in HL, these three rock series have different lithological association, metamorphism and deformation. haMajiajie group and Heilongjiang mélange, the former worker considered that these three groups are Precambrian metamorphic rocks, with the middle-late proterozoic granitoid giness(Wang et.). The dominant materiral compositions of HL,Xingdong group and Heilongjiang group, is distributing widely, when Majiajie group is only distributing in Majiajie and Shuangyazi village in the form of NE belt. By now the view about xingdongqun and heilongjiang group has been unanimous, but there are still some questions which have not been solved including the relationship between Xingdong group and Majiajie group, and the outcropped rocks of Heilongjiang group is apparently different from　 the Heilongjiang melange in Luobei, Yilan, Mudanjiang, they are all located in the suture zone between JB and Songnen Block (SB). There are no blueschist facies rocks outcroped in HL, and the strike-slip direction is almostly NS, when NE in the other regions. All these diffrences make us to do the research work in this region, and then we can get know about the tectonic evolution of this zone.In order to solve these questions mentioned above, we did field work in Huanan and circumjacent regions form July to September, 2006 on the basis of collecting and analyzing the former works. We saw out these three suits of metamorphic rocks, including the lithological assosiation, the symbol, and then we collected the spicemens to test, and do the systemic research about questions above using the methods of structual gelogy, litholigy, isotope chronology and genetic mineralogy.From the field and librory work, especially the entailed material identification, we get the information about the litholigical symbiosis maturial compositions, we identify the metamorphic facies, by the garnent-biotite geothermometers and geobarometers, we estimate the P and T of Xingdong group and Heiljiang melange, then discuss the tectonic evolution of HL combinating with the other geological datas.The post reserah works show that, the outcropped metamorphic rock series in HL consist of Xingdong group, Majiajie group and Heilongjiang melange, the metamorphic condition of Xingdong group is 590℃,0.4-0.5 Gpar,whiich metamorphic facies is amphibole facies. Mashan group and Xingdong group consist the basement of JB.. Majiajie Group is a suit of contact metamorphic rocks, which protoliths may be from sediments of　 Xingdong or Mashan Group that experienced the process of weathering and denudating. The time of contact metamorphism is about 270-250Ma.The rocks system which was named Heilongjiang Group before is a suit of mélange in fact and its metamorphic extent is greenschist facies(T 430℃,P 0.2-0.3 Gpar) .Until now we didn't find any H-P and L-T metamorphic materials, sucn as blueschist and crossite. Its strike of foliation is almost south-north trend, From comparing Heilongjiang mélange in Mudanjiang, Yilan and Luobei regions, we found that their attitude are not consistent, all these information show that the northeastern-trending faults control the extensive outcrops of blueschists. According to muscovite 40Ar/39Ar age 154.7±0.7Ma(Ye,1994)和166～175Ma(Li,1999),we can infer that the NE-trending structure happened in middle-late Jurassic..