首页|Early Devonian Post-collisional Granitic Magmatism in the North Qilian Orogenic Belt,Western China:Insights into Lithospheric Delamination and Orogenic Collapse

Early Devonian Post-collisional Granitic Magmatism in the North Qilian Orogenic Belt,Western China:Insights into Lithospheric Delamination and Orogenic Collapse

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Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identified in the North Qilian Orogenic Belt(NQOB).This paper reports an integrated study of petrology,whole-rock geochemistry,Sm-Nd isotope and zircon U-Pb dating,as well as Lu-Hf isotopic data,for two Early Devonian intrusive plutons.The Yongchang and Chijin granites yield zircon U-Pb ages of 394-407 Ma and 414 Ma,respectively.Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals,LREE-enriched patterns with negative Eu anomalies and a negative correlation between P2O5 and SiO2 contents,consistent with geochemical features of Ⅰ-type granitoids.Zircons from the studied granites display negative to weak positive εHf(t)values(-5.7 to 2.1),which agree well with those of negative εNd(t)values(-6.4 to-2.9)for the whole-rock samples,indicating that they were derived from the partial melting of Mesoproterozoic crust.Furthermore,low Sr/Y ratios(1.13-21.28)and high zircon saturation temperatures(745℃to 839℃,with the majority being>800℃)demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source.Taken together,the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during post-collisional extensional collapse.The data obtained in this study,when viewed in conjunction with previous studies,provides more information about the tectonic processes that followed the closure of the North Qilian Ocean.The tectonic transition from continental collision to post-collisional delamination could be constrained to～430 Ma,which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon εHf(t)values for granitoids.A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes(a)continental collision and crustal thickening during ca.455-430 Ma,characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism;(b)post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca.430-390 Ma,provided by coeval high-Mg adakitic magmatism,A-type granites and I-type granitoids with low Sr-Y ratios.

post-collisional magmatismlithospheric delaminationextensional collapseNorth Qilian Orogenic Belt

WANG Qian、ZHAO Xilin、MENG Yuanku、YU Shengyao、LIU Yanan

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College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China

Nanjing Center,China Geological Survey,Nanjing 210016,China

Key Laboratory of Submarine Geosciences and Prospecting Techniques,MOE,Institute for Advanced Ocean Study,College of Marine Geosciences,Ocean University of China,Qingdao,Shandong 266100,China

Sinopec Qingdao Liquefied Natural Gas Co.,Ltd.,Qingdao,Shandong 266400,China

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Natural Science Foundation of Shandong ProvinceTaishan ScholarsNational Natural Science Foundation of China

ZR2022QD055tstp 2023121442372247

2024

10.1111/1755-6724.15149

地质学报(英文版)
中国地质学会

地质学报(英文版)

CSTPCD
影响因子：1.414
ISSN：1000-9515
年,卷(期)：2024.98(2)
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