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Metamorphic evolution and geochronology of the tectonic melange of the Dongbatu and Mogutai Blocks, middle Dunhuang orogenic belt, northwestern China

Hao Y. C. Wang, Qian W. L. Zhang, Lu Junsheng, Chen Hongxu, Liu Jiahui, Hui C. G. Zhang, Van Tho Pham, Tao Peng and Wu Chunming
Metamorphic evolution and geochronology of the tectonic melange of the Dongbatu and Mogutai Blocks, middle Dunhuang orogenic belt, northwestern China
Geosphere (Boulder, CO) (April 2018) 14 (2): 883-906

Abstract

Mafic granulite and amphibolite in the Dongbatu and Mogutai blocks, middle Dunhuang orogenic belt, northwest China, southernmost Central Asian orogenic belt, occur as lenses within the matrix of metapelite and marble, exhibiting typical block-in-matrix fabrics of tectonic melange. Three stages of metamorphic mineral assemblages were identified in these lenses. Clockwise metamorphic pressure-temperature (P-T) paths were obtained through geothermobarometry and thermodynamic pseudosection modeling, passing from 656 degrees C and 10.9 kbar through 830 degrees C and 16.5 kbar to 657 degrees C and 4.9 kbar for the mafic granulite, and from 564-645 degrees C and 3.2-9.6 kbar through 634-727 degrees C and 6.1-14.2 kbar to 615-664 degrees C and 3.2-4.2 kbar for the amphibolites, respectively. Metamorphic peak P-T conditions in the metapelitic country rocks were estimated to be 635-675 degrees C and 6.0-6.9 kbar. The metamorphic peak of the mafic granulite approaches the high P-T facies series, indicative of a subduction zone. Secondary-ion mass spectrometry and laser ablation-inductively coupled plasma-mass spectrometry U-Pb dating of metamorphic zircons suggests that the metamorphic event occurred between ca. 420 and 372 Ma. These data further certify that the subduction of the continental margin and subsequent uplift of the Dunhuang orogenic belt represent a long-lived tectono-metamorphic event in the Paleozoic.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 14
Serial Issue: 2
Title: Metamorphic evolution and geochronology of the tectonic melange of the Dongbatu and Mogutai Blocks, middle Dunhuang orogenic belt, northwestern China
Affiliation: Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, China
Pages: 883-906
Published: 201804
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 97
Accession Number: 2018-037262
Categories: Igneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N40°04'00" - N40°12'00", E95°34'60" - E96°10'00"
Secondary Affiliation: University of Chinese Academy of Sciences, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201820
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