The amphibolite-facies metamorphosed mafic rocks from the Maxianshan area, Qilian block, NW China: A record of early Neoproterozoic arc magmatism

Tung, Kuo An; Yang, Haw‐Ching; Liu, Dun Yi; Zhang, Jian Xin; Yang, Huai Jen; Shau, Yen Hong; Tseng, Chin Chung

doi:10.1016/j.jseaes.2011.12.006

Cited by 87 publications

(32 citation statements)

References 28 publications

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“…For example, our interpreted cross section shows an unconformity at the base of the Neoproterozoic strata, which is consistent with the fi eld relationship in the region where Archean to Paleoproterozoic crystalline rocks are intruded by 750-1190 Ma plutons and are overlain by Neoproterozoic strata (Guo et al, 1999;Wan et al, 2001Wan et al, , 2003H. Wang et al, 2007;Tung et al, 2012). However, the same feature could be interpreted as a thrust fault separating two styles of deformation above and below.…”

Section: Refl Ectors In the Upper Crustsupporting

confidence: 82%

“…The current lack of fi eld checks for these sections makes this estimate speculative. Van der Woerd et al (2001) estimated ~9-12 km of shortening across the Danghe Nan Shan thrust, a southernmost thrust in the Qilian Shan thrust belt. Their estimate was obtained by extrapolating the Holocene slip rates of the fault over a time span of 8 m.y.…”

Section: Fig 8amentioning

confidence: 99%

“…As Archean to Mesoproterozoic metamorphic basement rocks intruded by 750-1190 Ma orthogneiss are present along the edges of Xining and Lanzhou Basins near our seismic-refl ection profi le (Guo et al, 1999;Wan et al, 2001Wan et al, , 2003H. Wang et al, 2007;Tung et al, 2012), we project these rocks onto the seismic profi le according to their strike, stratigraphic thickness, and structural positions where the information is available.…”

Section: Seismic-reflection Profilementioning

confidence: 99%

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Tectonic development of the northeastern Tibetan Plateau as constrained by high-resolution deep seismic-reflection data

et al. 2013

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A 180-km-long, high-resolution seismic-refl ection survey that imaged the entire crust and the uppermost mantle lithosphere was conducted across the northeastern Tibetan Plateau. This work had three aims: (1) to examine whether the left-slip Haiyuan and Tianjing faults defi ning the margin of NE Tibet are crustal-or lithospheric-scale structures, (2) to determine whether seismic fabrics are consistent with middle-and/ or lower-crustal channel fl ow, and (3) to establish the minimum amount of Cenozoic shortening strain in the region. Analysis of our newly obtained seismic-refl ection data suggests that the left-slip Haiyuan and Tianjing faults have multiple strands and cut through the upper and middle crust. The faults likely terminate at a low-angle detachment shear zone in the lower crust, because the fl at Moho directly below the projected traces of the faults is continuous. The seismic image displays subvertical zones of highly refl ective sequences containing parallel and subhorizontal refl ectors that are truncated by seismically transparent regions with irregular shape. The transparent regions in the middle crust are traceable to the seismically transparent lower crust and are interpreted as early Paleozoic plutons emplaced during the construction of the Qilian arc in the region. The presence of the undisturbed subvertical contacts between zones of highly refl ective and seismically transparent regions rules out the occurrence of channel fl ow in the middle crust, as this process would require through-going subhorizontal refl ectors bounding the channel above and below. The lack of continuous refl ectors longer than a few kilometers in the lower crust makes a laminar mode of channel fl ow unfavorable, but lateral lower-crustal fl ow could have occurred via small-scale ductile deformation involving folding (less than a few kilometers in wavelength and amplitude). Integrating surface geology and the seismic data, we fi nd that the upper crust along a segment of the seismic surveying line experienced up to 46% crustal shortening postdating the Cretaceous and is thus interpreted as entirely accumulated in the Cenozoic. If the estimated shortening strain is representative across northeastern Tibet, its magnitude is suffi cient to explain the current elevation of the region without an appeal for additional contributing factors such as channel fl ow and/or a thermal event in the upper mantle.

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Section: Refl Ectors In the Upper Crustsupporting

confidence: 82%

Section: Fig 8amentioning

confidence: 99%

Section: Seismic-reflection Profilementioning

confidence: 99%

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Tectonic development of the northeastern Tibetan Plateau as constrained by high-resolution deep seismic-reflection data

et al. 2013

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“…Regarding the tectonic setting of the QB in the Neoproterozoic, numerous studies have noted the extensive occurrences of arc‐ or collision‐type granitoids (e.g., Chen et al, ; Gehrels et al, ; Guo, Zhao, et al, ; Liu, Wang, & Shi, ; Tung et al, ; Wan et al, ; Wan et al, ) and arc‐type, mafic‐ultramafic rocks (Liu, Xiao, Yuan, & Yan, ; Tseng et al, ; Tung et al, ; Zhang et al, ). Sedimentology and geochemistry of the QB basement metasedimentary rocks (Guo, Zhang, et al, ; Wan et al, ) suggest that the QB formed at an active continental margin.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the affinity and Precambrian tectonic evolution of the QB is not well resolved. Previous studies considered the QB to have rifted from North China (Qiu, ; Zuo & Liu, ), whereas recent studies have focused on the QB being a detached fragment of the Yangtze Block (YB; Guo et al, ; Tseng et al, ; Tung et al, , ; Wan et al, ; Wan, Yang, Xu, & Wu, ; Xu et al, ; Zhang, Jin, et al, ). Tung et al () indicate that the QB may have been a part of the Sibao Orogeny during the Neoproterozoic.…”

Section: Introductionmentioning

confidence: 99%

Geochronology and petrogenesis of Neoproterozoic S‐type granites from the Qilian Block, north‐west China, and their geological implications

Liu

Ren

et al. 2018

Geological Journal

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Early Neoproterozoic granites rarely outcrop in the Qilian Orogenic Belt (QOB) at the north‐eastern margin of the Qinghai–Tibet Plateau; however, they are vital to understanding the Precambrian evolution of the QOB. Thus, we present an integrated study, comprising petrology, geochronology, and whole‐rock geochemistry of two Early Neoproterozoic granitic plutons (Baihuagou and Yamacha plutons) in the eastern Qilian Block (QB). The results provide three key findings. First, their magma emplacement age is ca. 900 Ma (i.e., 918 Ma for Baihuagou and 910 Ma for Yamacha), and the two plutons have similar high‐K calc‐alkaline, strongly peraluminous characteristics, with slight enrichment in light rare earth elements; weak negative Eu anomalies; enrichment in large‐ion lithophile elements (e.g., K, Th, Ba, and Rb); strong depletion in Ti; and weak depletion in Nb, Ta, and, Sr. These characteristics indicate that the granites from these plutons are S‐type granites. Second, the two‐mica granite and gneissic granite samples may have been formed by partial melting of ancient crustal material (mainly psammitic rocks), with contributions from a meta‐igneous component, under high‐temperature and low‐pressure conditions. Third, new data from this study, combined with previously reported dates, indicate a continental margin arc setting for the QB during the Early Neoproterozoic (ca. 900 Ma).

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Early Paleozoic arc magmatism and metamorphism in the northern Qilian Block, western China: Petrological and geochronological constraints

Peng

Zhang

et al. 2017

Geological Journal

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The Datong–Menyuan Complex, located in the northern margin of the Qilian Block, is composed dominantly of high‐grade metamorphic rocks covered by a Paleozoic–Mesozoic sedimentary sequence. In this study, we present petrographic observation, conventional thermobarometry and P–T pseudosection modelling, whole‐rock major and trace geochemistry, zircons U–Pb dating and Hf isotopic data together, to reveal the relationship between the magmatism and metamorphism along the northern margin of the Qilian Block. The anticlockwise P–T paths of gneiss and amphibolites are obtained using the garnet isopleths thermobaromety combined with phase equilibria modelling. The P–T pseudosection also shows that the gneiss and amphibolite underwent similar retrograde metamorphism with slightly different peak metamorphic conditions at ~720 °C and ~6.4 kbar for the former and ~700 °C and ~7.1 kbar for the latter. This indicates the Datong–Menyuan Complex recorded an amphibolite–granulite‐facies metamorphism. The zircon U–Pb analyses of 3 intrusive rocks including granitic dike, diorite, and granite are dated at ca. 499.8 ± 4.3, 495.9 ± 3.3, and 505.5 ± 3.2 Ma, and 3 representative metamorphic rocks underwent contemporaneous metamorphism at ca. 498.9 ± 4.1, 504.4 ± 3.9, and 499.3 ± 2.9 Ma. Zircon Hf isotopic analyses show that 505‐Ma zircons from the granitoid have positive εHf(t) values ranging from +8.5 to +12.8, indicating a depleted mantle source. Based on the penecontemporaneous magmatic and metamorphic event, we suggest that the southward subduction of the north Qilian Ocean triggered the activity of mantle‐derived magma and coeval metamorphic event. A subsequent compression is attributed to crustal thickening, indicating counter clockwise P–T paths. Combining these data with previous studies, it suggests paired metamorphic belts: the penecontemporaneous high‐temperature metamorphic belt related to an arc along the northern Qilian Block and high‐pressure/low‐temperature metamorphic belt existed in the north Qilian suture.

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The amphibolite-facies metamorphosed mafic rocks from the Maxianshan area, Qilian block, NW China: A record of early Neoproterozoic arc magmatism

Cited by 87 publications

References 28 publications

Tectonic development of the northeastern Tibetan Plateau as constrained by high-resolution deep seismic-reflection data

Tectonic development of the northeastern Tibetan Plateau as constrained by high-resolution deep seismic-reflection data

Geochronology and petrogenesis of Neoproterozoic S‐type granites from the Qilian Block, north‐west China, and their geological implications

Early Paleozoic arc magmatism and metamorphism in the northern Qilian Block, western China: Petrological and geochronological constraints

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