地学前缘 ›› 2023, Vol. 30 ›› Issue (2): 215-238.DOI: 10.13745/j.esf.sf.2022.1.21

• 构造-岩浆作用与大地构造背景 • 上一篇    下一篇

辽东半岛青城子地区晚三叠世构造岩脉成因及其金成矿意义

董小宇1,2(), 孔若颜1,*(), 颜丹平1, 邱亮1, 邱骏挺3   

  1. 1.中国地质大学(北京) 地球科学与资源学院, 北京 100083
    2.核工业二四三大队, 内蒙古 赤峰 024000
    3.核工业北京地质研究院, 北京 100029
  • 收稿日期:2021-09-06 修回日期:2021-12-06 出版日期:2023-03-25 发布日期:2023-01-05
  • 通讯作者: 孔若颜
  • 作者简介:董小宇(1996—),男,硕士研究生,助理工程师,构造地质学专业。E-mail: dongxy4216@163.com
  • 基金资助:
    国家重点研发计划项目“华北克拉通成矿系统的深部过程与成矿机理”的专题项目”(2016YFC0600100);“辽东地区中生代构造与控矿规律”(2016YFC0600102-03)

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

摘要:

青城子地区作为辽东半岛重要的金矿集区,其金成矿与中生代岩浆作用关系极为密切。区内广泛发育有与金矿脉密切相关的中生代晚三叠世花岗质岩脉,脉体主要沿NE和EW向断裂构造在224~217 Ma侵位,随后经历了伸展构造作用改造。岩石地球化学分析显示岩脉具有高Sr((362.00~1 296.85)×10-6)、低Y((4.73~12.30)×10-6)、低Yb((0.49~1.05)×10-6),以及较高Sr/Y值(38~118)等高Sr低Yb花岗岩特征,在构造判别图解中多位于同碰撞区域。Sr-Nd同位素组成特征显示岩脉(87Sr/86Sr)i值高(0.707 8~0.710 9),εNd(t)值低(-16.34~-15.30),二阶段模式年龄较为古老( T D M 2=2 323~2 237 Ma),指示其形成于加厚古老下地壳的部分熔融。同时,侵位时间稍晚于岩脉的弟兄山岩体(211 Ma)的地球化学特征指示其形成于后碰撞伸展环境。因此,我们认为区内晚三叠世岩脉可能形成于华北-华南板块陆-陆碰撞末期挤压-伸展转换这一构造背景。青城子地区晚三叠世岩脉与金矿脉在时间、空间及成因上关系密切,二者多平行产出,构造背景相同,部分岩脉即是矿脉。青城子地区金矿主成矿期可能为晚三叠世,在早白垩世构造-岩浆作用的改造下矿化再富集,具多期矿化的特征,区域内成群发育的晚三叠世岩脉可作为重要的找矿标志。

关键词: 青城子地区, 晚三叠世岩脉, 地球化学特征, 控矿构造, 金成矿作用

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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