Geochemistry and petrogenesis of Permian granitoids in the northwestern margin of the North China Craton: insights from the Dongshengmiao pluton, Inner Mongolia

As a pivotal junction between the North China and Tarim cratons, the Alxa Terrane provides an ideal window to constrain the final closure of the middle segment of the Paleo-Asian Ocean (PAO). This study carried out petrological, whole-rock geochemical, and zircon U-Pb-Hf isotopic investigations on four major granitic plutonic complexes in the Alxa Terrane. The Bayan Nuru and Yabulai plutonic complexes are I-type granitoids that yield crystallization ages of 281-268 Ma and 277-270 Ma, respectively, with negative zircon ε Hf (t) values (−11.5 to −3.2), primarily sourced from the Neoproterozoic rocks in the region. The Nuergai granitoids yield crystallization ages of 281-268 Ma and show I-type affinities and positive zircon ε Hf (t) values (+1.6 to +6.4), indicating an origin related to magma mixing. Emplaced at ca. 241 Ma, the Oliji granitoids display varying zircon ε Hf (t) values from −0.9 to +11.5, which necessitate a predominant source of mantle-derived materials. A compilation of zircon ε Hf (t) and whole-rock ε Nd (t) values of the magmatic rocks in the Alxa Terrane illustrates a decreasing trend from the Late Carboniferous to the Early Permian and an increasing trend during Middle Permian to Triassic time. The marked shift with a large variation of zircon ε Hf (t) and whole-rock ε Nd (t) values at 280-265 Ma indicates a tectonic switch from subduction to post-collision tectonic regimes in the Alxa Terrane, marking the final closure of the middle segment of the PAO. Comparable isotope variations are also identified from 260 to 245 Ma magmatic counterparts on the northern margin of the North China Craton, hence suggesting a progressively eastward closure of the PAO.

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“…Zhang et al, 2013;W. Zhang et al, 2013;Dan et al, 2014a;Lin et al, 2014;Hu et al, 2015;Wang et al, 2015b).…”

Section: Permian Granitoidsunclassified

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

et al. 2017

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“…280 Ma, Tong et al ., ). These rocks have all been linked to a post‐collisional extensional setting (Ling et al ., ; Zhang et al ., ; Chen et al ., ; Hu et al ., ; Tong et al ., ; Zhang et al ., ). Corresponding ages are very common in the detrital zircons of all three of our samples supporting the importance of this activity in the NCC.…”

Section: Discussionmentioning

confidence: 99%

LA‐ICP‐MS U–Pb geochronology of zircons from granitoids and modern river sands in Guyang, North China Craton and their tectonic significance

et al. 2016

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The Palaeo‐Asian Ocean (PAO) was located between Siberia and the North China Craton (NCC). The time of its closure, as well as the crustal architecture of the surrounding region, are still uncertain. In this paper, we address these problems using LA‐ICP‐MS U‐Pb ages of zircon grains in three magmatic rocks and three river sand samples of the Guyang area at the northern margin of the NCC. The magmatic rocks yield early Carboniferous crystallization ages of 340.3 ± 7.5 Ma, 331.7 ± 2.3 Ma and 341.1 ± 1.9 Ma for the main granitic pluton, a granodiorite dyke and a diorite enclave, respectively. They were the product of subduction of the PAO underneath the NCC. The detrital zircon U‐Pb ages in the river sand samples are dominated by two groups at 2550–2400 and 290–260 Ma, with subordinate groups at 2700–2600, 2000–1800 and 320–300 Ma, dispersed Early Palaeoproterozoic grains and a minor but important group of Cretaceous grains in sands of the Aibugai River. These results, combined with previous geochronological data, permit a re‐assessment of the tectonic evolution of the northern margin of the NCC. The events at ~2.5 Ga reflect major crustal reworking and cratonization of the northern margin of the NCC, which then became a stable platform lasting until the Carboniferous. The period between 2.0 and 1.8 Ga was characterized by major collisions related to formation of the Khondalite Belt and the Trans‐North China Orogen. In the Carboniferous, subduction of the PAO underneath the northern margin of the NCC developed a zoned distribution of magmatic rocks. The PAO is now constrained to have closed in the Early Permian by the collision of the NCC and Siberia. The youngest group of Cretaceous zircons reflects magmatic events related to lithosphere thinning beneath the Eastern Block of the NCC. Copyright © 2016 John Wiley & Sons, Ltd.

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“…1b), and it is close to the Southern Orogenic Belt and the Ondor Sum-Jizhong-Yanji suture. In the late Paleozoic, this area underwent a strong tectonic magmatic activity and a large amount of granitoids with some coeval mafic-ultramafic rocks formed a huge magmatic rock belt extending from Dongshengmiao to Taibus Banner along the northern margin of the NCC (Hu et al, 2015). In the Uradzhongqi area, the basement is dominated by the Archean gneisses, which are covered by the late Paleoproterozoic low-grade metamorphic rift sequences of the Bayan Obo group.…”

Section: Geological Settingmentioning

confidence: 99%

“…1c). On one hand, some researchers proposed a model of underplating of basaltic magma in a post-collisional extensional regime to account for the petrogenesis of the Permian rocks (Hong, 1994;Shi et al, 2004;Zhang et al, 2008;Luo et al, 2010;Xu et al, 2014;Hu et al, 2015). On the other hand, others proposed that they were island-arc volcanics produced by the subduction of the Paleo-Asian Ocean Miao et al, 2007;Zhang et al, 2009;Ma et al, 2013;Wang et al, 2015).…”

Section: Introductionmentioning

confidence: 97%

Elemental and Sr–Nd isotopic geochemistry of the Uradzhongqi magmatic complex in western Inner Mongolia, China: A record of early Permian post-collisional magmatism

Qiao

Zhong

et al. 2017

Journal of Asian Earth Sciences

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Geochemistry and petrogenesis of Permian granitoids in the northwestern margin of the North China Craton: insights from the Dongshengmiao pluton, Inner Mongolia

Cited by 20 publications

References 62 publications

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

Geochronology and geochemistry of Permian to Early Triassic granitoids in the Alxa Terrane: Constraints on the final closure of the Paleo-Asian Ocean

LA‐ICP‐MS U–Pb geochronology of zircons from granitoids and modern river sands in Guyang, North China Craton and their tectonic significance

Elemental and Sr–Nd isotopic geochemistry of the Uradzhongqi magmatic complex in western Inner Mongolia, China: A record of early Permian post-collisional magmatism

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