吉中地区范家屯组变沉积岩碎屑锆石年代学与Hf同位素示踪

——对古亚洲洋东段闭合的约束

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关键词：范家屯组；碎屑锆石；U-Pb年代学；地球化学；物源分析；古亚洲洋闭合doi：10.13278/j.cnki.jjuese.20250235

文献标志码：A

Abstract：The Fanjiatun Formation in central Jilin，situated on the northern margin of the North China craton，represents a key geological unit for constraining the closure of the eastern Paleo-Asian Ocean. Systematic petrography， detrital zircon U-Pb geochronology，Lu - Hf isotopes，and whole-rock geochemical analyses were performed on its metasedimentary rocks. The youngest detrital zircon population yields a weighted mean age of （ 233.6±5.0 ）Ma（ N=11 ），constraining the maximum depositional age to not earlier than the Late Triassic. Whole-rock geochemistry （Al2O3/TiO2=24.65- 63.69，avg.37.84） and elemental ratios （La/Sc，Th/Sc， Cr/Th ， Eu/Eu* ）indicate felsic to intermediate upper-crustal sources. Detrital zircon age spectra and predominantly positive values indicate provenance mainly from the Northeastern block and the northern margin of the North China craton. Tectonic discrimination parameters together with time-series variations in zircon trace elements reveal a transition from compressional orogenesis to extensional stabilization in the study area，and suggest that Paleozoic to Early Mesozoic crustal evolution was characterized by three episodes of thinning and two of thickening，closely coupled with the late subduction-closure regime of the eastern Paleo-Asian Ocean.

Key words： Fanjiatun Formation; detrital zircon; U-Pb ages；geochemistry； provenance analysis; closure of the Paleo-Asian Ocean

0 引言

中国东北地区显生宙构造演化以古亚洲洋构造域与环太平洋构造域的复合叠加为特征，这一区域在古生代时期主要受到古亚洲洋构造域的影响，在中生代以后受环太平洋构造域和蒙古一鄂霍茨克构造域的叠加与改造作用[1-4]。（剩余36725字）