摘要
张家口马道口钼矿床位于华北地台北缘,由于发现时间较短,对该矿床的研究较为薄弱。本文对矿区石英正长斑岩进行LA-ICP-MS锆石U-Pb定年和地球化学特征研究,结果显示,岩石的结晶年龄分别为MK7(132.0±1.2)Ma、MK8(131.4±1.2)Ma、MK9(129.1±1.6)Ma、MK11(131.8±1.3)Ma,形成于早白垩世。在TAS图解中含矿斑岩落入花岗岩区域,不含矿斑岩落入石英二长岩区域,在SiO_(2)-K_(2)O图解中含矿斑岩落入钙碱性区域,不含矿斑岩落入钾玄岩区域。二者稀土元素标准化分布型式上相似,均呈现左倾右平台型分布态势,即轻稀土富集、重稀土分馏不明显,两种岩石均呈现出较为明显Eu负异常。主、微量元素特征表明,矿区上部灰色斑岩和下部肉红色斑岩可能为同源岩浆不同熔融程度所致,岩体具有高温型碰撞造山的强过铝质S型花岗岩的特征,岩石源区可能有重熔的底垫弧火山岩的贡献。石英正长斑岩是早白垩世岩浆活动的产物,其形成与该时期华北克拉通伸展减薄有关。岩石圈伸展减薄,导致软流圈上涌,下地壳发生熔融,为成岩提供了物质来源。
The Madaokou Molybdenum deposit in Zhangjiakou is located at the edge of the North China Platform.Due to the short discovery time,research on the deposit is relatively weak.In this paper,LA-ICP-MS zircon U-Pb dating and geochemical characteristics of the quartz syenite porphyry in the deposit were studied.The results show that the crystallization ages of the rocks are MK7(132.0±1.2)Ma,MK8(131.4±1.2)Ma,MK9(129.1±1.6)Ma,and MK11(131.8±1.3)Ma,which were formed in the Early Cretaceous.In the TAS diagram,ore-bearing porphyry and ore-free porphyry fall into granite and quartz monzonite field,respectively.In the SiO_(2)-K_(2)O diagram,ore-bearing porphyry and ore-free porphyry fall into calc-alkaline and potassium basalt fields.The normalized distribution patterns of rare earth elements are similar,showing a left-to-right platform distribution trend,which LREE enrichment and HREE fractionation is not obvious.Both rocks show obvious negative Eu anomalies.The characteristics of major and trace elements indicate that grey porphyry in the upper part and red porphyry in the lower part may be caused by different melting degrees of homologous magma.The rock mass has the characteristics of S-type granite with strong peraluminous high temperature collisional orogeny.The source area may have been contributed by remelted subduction arc volcanic rocks.The quartz syenite porphyry is the product of the early Cretaceous magmatic activity,and its formation is related to the extension and thinning of the North China Craton during the Early Cretaceous.Stretching and thinning of the lithosphere leads to upwelling of the asthenosphere and melting of the lower crust,providing a source of material for diagenesis.
作者
周吉晨
沈星
贾飞
丁心科
周晨阳
李智亮
吕晨
冯国平
韩佳益
袁新生
ZHOU Jichen;SHEN Xing;JIA Fei;DING Xinke;ZHOU Chenyang;LI Zhiliang;LV Chen;FENG Guoping;HAN Jiayi;YUAN Xinsheng(Zhejiang Jiuhe Geological Ecological Environment Planning and Design Co.,LTD.,Huzhou,Zhejiang,313000;Research(Innovation)Center for Disaster Prevention and Ecological Environment Restoration,Huzhou,Zhejiang,313000;Hebei GEO University,Shijiazhuang,Hebei,050030)
出处
《浙江国土资源》
2023年第S1期27-40,共14页
Zhejiang Land & Resources
