Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (2): 215-238.DOI: 10.13745/j.esf.sf.2022.1.21

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Origin and gold mineralization significance of Late Triassic syn-tectonic dykes in the Qingchengzi area, Liaodong Peninsula

DONG Xiaoyu1,2(), KONG Ruoyan1,*(), YAN Danping1, QIU Liang1, QIU Junting3   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. Nuclear Industry Team 243, Chifeng 024000, China
    3. Beijing Research Institute of Uranium Geology, Beijing 100029, China
  • Received:2021-09-06 Revised:2021-12-06 Online:2023-03-25 Published:2023-01-05
  • Contact: KONG Ruoyan

Abstract:

The Qingchengzi area is an important gold ore concentration area in the Liaodong Peninsula where Mesozoic magmatism played a key role in gold mineralization. The widely developed Late Triassic granitic dykes, which are closely related to gold veins, are emplaced mainly along the NE-/EW-trending faults around 224-217 Ma and subsequently experienced extensional event. These dykes, as revealed by geochemical analysis, have high Sr (362.00×10-6-1296.85×10-6) and low Y (4.73×10-6-12.30×10-6) and Yb (0.49×10-6-1.05×10-6) contents and high Sr/Y ratios (38-118), showing the characteristics of high-Sr, low-Yb granitoid, while the structural discrimination diagram indicates they are likely syn-collisional granites. Sr-Nd isotopic composition shows that these dykes have high (87Sr/86Sr)i ratios (0.7078-0.7109) and low εNd(t) values (-16.34--15.30) and TDM2 ages of 2323-2237 Ma, indicating they are derived from the melting of thickened lower crust. Meanwhile geochemical analysis indicates a neighboring rock mass, Dixiongshan pluton (211 Ma), is formed in a post-collision extensional environment. Thus we suggest that these dykes might be formed during the tectonic transition from compression to extension in the late stage of continent-continent collision between the North and South China Blocks. In the Qingchengzi area, Late Triassic dykes and gold veins are closely related in emplacement time, space and genesis as they commonly develop in parallel in similar tectonic settings, and some dykes are also gold veins. Multi-stage gold mineralization in the Qingchengzi area includes the main mineralization period, resulted by the Late Triassic compressional tectonics, and the re-enrichment period, resulted by the Early Cretaceous tectono-magmatism. Therefore the widely developed Late Triassic dykes in the Qingchengzi area may be an important indicator for gold deposit prospecting.

Key words: Qingchengzi area, Late Triassic dyke, geochemical characteristics, ore control structure, gold mineralization

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