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Metamorphic evolution of the Heilongjiang glaucophanic rocks, NE China : Constraints from the P–T pseudosections in the NCKFMASHTO system
Author(s) -
Li Weimin,
Liu Yongjiang,
Takasu Akira,
Zhao Yingli,
Fazle Kabir Md,
Wen Quanbo,
Liang Chenyue,
Feng Zhiqiang,
Zhang Li
Publication year - 2019
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3455
Subject(s) - glaucophane , geology , phengite , geochemistry , metamorphism , metamorphic rock , epidote , blueschist , subduction , schist , zircon , metamorphic facies , chlorite , petrology , quartz , seismology , geomorphology , paleontology , eclogite , tectonics , facies , structural basin
The glaucophanic rocks, including the garnet‐barroisite schist (09YL10) and glaucophane aegirine‐augite schist (09YL12) from the Heilongjiang Complex exposed in the Yilan area, have been petrographically investigated, in order to contribute to the discussion on the high‐ P/T metamorphism that took place in the suture zone between the Jiamusi and Songliao blocks, NE China. The mineral assemblages of peak metamorphic stage are characterized by garnet (100X Ca < 26) + epidote + barroisite/katophorite + phengite (Si < 6.84 pfu) + chlorite + quartz + rutile + haematite and barroisite/katophorite + glaucophane + aegirine‐augite (Jd < 30) + epidote + phengite (Si < 6.84 pfu) + haematite ± quartz ± chlorite for the investigated samples 09YL10 and 09YL12, respectively. By applying P–T pseudosection modelling in the NCKFMASHTO system, the peak metamorphic conditions yield 550–580°C/1.1–1.3 GPa and 500–550°C/1.1–1.3 GPa, for sample 09YL10 and 09YL12, respectively, indicating the epidote‐amphibolite facies metamorphism. Furthermore, the equilibrium mineral assemblages and the estimated P–T conditions define the Alpine‐type clockwise P–T paths for the Heilongjiang glaucophanic rocks, suggesting isothermal decompression (ITD) and/or slight heating during the beginning of the exhumation process. These P–T paths significantly match to the warm subduction trajectory, indicating the tectonic regimes similar to those of young oceanic slabs subduction zones and subsequent continental orogenic belts. Taking available regional geochronological data into account, we propose that the final subduction/collision between the Jiamusi and Songliao blocks took place in the Jurassic, effected by the Palaeo‐Pacific subduction system, leading to formation of the Heilongjiang glaucophanic rocks and their high‐ P/T metamorphosed pelitic country rocks.