摘要
榆树沟山金矿床位于北祁连造山带西段,是祁连成矿带内新发现的一个中型金矿床,矿床类型为岩浆期后热液型金矿,该金矿形成与花岗闪长斑岩脉热液蚀变关系密切。为了查明花岗闪长斑岩脉的成岩时代、源区性质和构造背景,开展了锆石U-Pb定年、Hf同位素和全岩地球化学研究工作。结果表明:花岗闪长斑岩脉的岩性为蚀变花岗闪长斑岩,侵入于阴沟群地层内构造破碎带中。该岩脉LA-ICP-MS锆石UPb年龄为(423.5±3.5)~(422.8±3.4)Ma,指示岩浆侵位时代为晚志留世。岩石具有低TFe2O3(1.57%~2.43%)和MgO(0.91%~1.43%)含量,高Al2O3(15.66%~17.20%)含量和A/CNK值(1.10~1.29),属于钙碱性准铝质系列岩石。岩石富集Rb、Ba、Sr和轻稀土元素,亏损Nb、Ta和Y、Yb等元素,具有高Sr含量(289×10^(-6)~486×10^(-6))和Sr/Y比值(65.1~95.3),低Y(4.11×10^(-6)~5.48×10^(-6))和Yb(0.38×10^(-6)~0.49×10^(-6)),与埃达克岩的地球化学特征相似。该岩体结晶锆石ε_(Hf)(t)为正值(+7.50~+11.0),二阶段模式年龄(TDM2)为0.86~0.67 Ga,推测岩石起源于新元古代新生地壳物质的部分熔融。结合区域地质背景,初步认为榆树沟山矿区花岗闪长斑岩脉形成于祁连山造山带碰撞后伸展环境,晚志留世强烈陆内伸展作用诱发造山带新元古代新生洋壳发生部分熔融,形成埃达克质岩浆,沿断裂带形成了花岗闪长斑岩。
Yushugoushan gold deposit is located in the western part of the north Qilian orogenic belt,it is a newly discovered medium-sized gold deposit.It belongs to post-magmatic hydrothermal gold deposit.The formation of the gold deposit is closely related to the hydrothermal alteration of the granodiorite porphyry veins.In order to confirm the intrusive age,lithogenesis and magma source characteristic of the granodiorite porphyry veins,the study of LA-ICP-MS zircon U-Pb isotopic dating,Hf isotope and whole-rock geochemical were carried out.The results show that the lithology of granodiorite porphyry veins is altered granodiorite porphyry,which intrudes into the structural fracture zone in the Yingou Group strata.The LA-ICP-MS zircon U-Pb age of granodiorite porphyrys obtained is(423.5±3.5)~(422.8±3.4)Ma,indicating that the magma emplacement age is Late Silurian.The major elements of granodiorite porphyrys are characterized by low TFe2O3(1.57%~2.43%),MgO(0.91%~1.43%)contents and A/CNK values(1.10~1.29),suggesting the granodiorite porphyrys belongs to the calcalkaline and peraluminous series rock.They are relatively enriched such as Rb,Ba,Sr and light rare earth elements,and depleted Nb,Ta and Y,Yb,it is characterized by high Sr content(289×10^(-6)~486×10^(-6))and Sr/Y ratio(65.1~95.3),low content of Y(4.11×10^(-6)~5.48×10^(-6))and Yb(0.38×10^(-6)~0.49×10^(-6)),this likely indicates adakitic granite.In-situ Hf isotope analysis of zircon shows that theε_(Hf)(t)values range from 7.50 to 11.0,and Hf two-stage model age is 0.86 Ga to 0.67 Ga,suggesting that the major rock is the product of partial melting of juvenile crust derived from the Neoproterozoic depleted mantle.Combined with the regional geological background,it is preliminarily considered that the Yushugoushan granodiorite porphyry veins is formed the post collision extension stageintracontinental extension,during the Late Silurian,strong intracontinental extension induced the partial melting of the Neoproterozoic juvenile crust in the orogenic belt,and formed adakitic magma.In the process of its continuous upwelling and evolution,the Yushugoushan granodiorite porphyry dyke were formed.
作者
杨彦
黄增保
郭小刚
许延龙
颜华
YANG Yan;HUANG Zengbao;GUO Xiaogang;XU Yanlong;YAN Hua(Gansu Provincial Mineral Resource and Reserve Evaluation Center,Lanzhou 730000,Gansu,China;Geological Survey of Gansu Province,Lanzhou 730000,Gansu,China;Geoscience Big Data Engineering Research Center of Gansu Province,Lanzhou 730000,Gansu,China;Baiyin Mineral Exploration Institute of Gansu Nonferrous Metal Geological Exploration Bureau,Baiyin 730900,Gansu,China)
出处
《黄金科学技术》
CSCD
北大核心
2024年第3期387-399,共13页
Gold Science and Technology
基金
甘肃省自然基金项目“甘肃北山罗雅楚山地区沉积—变质型铁矿成矿规律与隐伏矿床预测”(编号:22JR5RA820)
甘肃省重点人才项目“敦煌地块东南缘构造—岩浆作用与金矿关系研究预测”(编号:甘资人函[2022]49号)联合资助。
