摘要
陕西凤县庙沟金矿位于秦岭造山带中段之商丹断裂带西段南缘,是陕西省新一轮找矿突破战略行动的重要进展与典型案例之一。区内地层发育齐全,岩浆活动和构造作用强烈,构成一较典型的金矿化密集区带。尤其是闪长玢岩脉分布范围广,局部见有明显的矿化蚀变现象,与矿体空间关系密切。为厘清庙沟金矿的成矿物质来源、流体性质及成矿时代,阐明其成矿作用机制,在系统梳理庙沟金矿区成矿地质特征的基础上,开展了岩(矿)石稀土、微量元素及H-O-S同位素分析,并对矿区闪长玢岩脉进行了锆石U-Pb定年。岩(矿)石稀土和微量元素分析结果显示:庙沟金矿区闪长玢岩脉稀土总量为99.45×10^(-6)~121.44×10^(-6),轻稀土含量为90.60×10^(-6)~112.26×10^(-6),重稀土含量为8.85×10^(-6)~10.12×10^(-6),δEu值为0.91×10^(-6)~0.99×10^(-6),δCe值为0.93×10^(-6)~0.94×10^(-6)。金矿石样品稀土总量为46.88×10^(-6)~121.44×10^(-6),轻稀土含量为41.60×10^(-6)~184.34×10^(-6),重稀土含量为5.28×10^(-6)~21.17×10^(-6);δEu值为0.57×10^(-6)~1.49×10^(-6),δCe值为0.85×10^(-6)~0.98×10^(-6)。H-O-S同位素分析结果显示:δD_(V-SMOW)值为-96‰~-59‰,δ^(18)Ofluid值为7.3‰~10.3‰,δ^(34)S值为4.15‰~11.88‰。岩(矿)石稀土、微量元素及H-O-S同位素特征表明:庙沟金矿成矿物质大部分来自岩浆,少部分来自围岩地层,成矿流体为多来源,可能主体为岩浆水。闪长玢岩的锆石U-Pb谐和年龄为(220.7±1.0)Ma,加权平均年龄为(219.8±2.1)Ma,庙沟金矿可能形成于晚三叠世,该时期强烈的脆—韧性剪切变形运动和岩浆活动与金矿化蚀变关系密切,可能提供了成矿热源和矿质来源,使早古生代罗汉寺岩群中的硅质和矿质强烈活化、迁移,并富集于NW-SE向脆—韧性剪切变形的多组裂隙中。晚三叠世构造变形—岩浆活动—成矿富集作用事件的意义重大。
The Matigou-Miaogou gold deposit,situated in Fengxian,Shaanxi Province,within the West Qinling region of China,is positioned at the southern margin of the western Shangdan fault zone,centrally located in the Qinling orogenic belt.This deposit represents a quintessential example within Shaanxi Province’s recent strategic initiatives aimed at advancing ore prospecting breakthroughs.The geological strata in this region span from the Paleoproterozoic to the Quaternary periods.Owing to multiple episodes of rifting,contraction,and amalgamation since the Proterozoic era,the exposed strata have experienced varying degrees of deformation,resulting in the formation of near east-west trending complex folds and faults.During the Triassic period,the region experienced intense magmatic activity,characterized by frequent magma intrusions that were often accompanied by multi-stage mineralization.Consequently,this area constitutes a significant structural zone for gold and nonferrous polymetallic mineralization.Notably,the diorite-porphyrite distribution within the mine area is extensive,with evident mineralization and alteration phenomena observable in certain sections,which are spatially closely associated with the ore bodies.This study conducts a preliminary investigation into the metallogenic epoch and mechanisms of the Miaogou gold deposit through a comprehensive analysis of the regional metallogenic background,geological characteristics,rare earth and trace element compositions of rocks(ores),H-O-S isotopic data,and zircon U-Pb dating of diorite-porphyrite veins in the Miaogou gold mine area.In this region,the diorite porphyrite exhibits total rare earth element(ΣREE)concent rations ranging from 99.45×10^(-6)to 121.44×10^(-6),with light rare earth element(LREE)concent rations between 90.60×10^(-6)and 112.26×10^(-6),and heavy rare earth element(HREE)concent rations from 8.85×10^(-6)to 10.12×10^(-6).The europium anomaly(δEu)values range from 0.91×10^(-6)to 0.99×10^(-6),while the cerium anomaly(δCe)values range from 0.93×10^(-6)to 0.94×10^(-6).For the ore samples,ΣREE content varies between 46.88×10^(-6)and 121.44×10^(-6),LREE content ranges from 41.60×10^(-6)to 184.34×10^(-6),and HREE content spans from 5.28×10^(-6)to 21.17×10^(-6).TheδEu values for the ores range from 0.57×10^(-6)to 1.49×10^(-6),and δCe value s range from 0.85×10^(-6)to 0.98×10^(-6).Additionally,the δD_(V-SMOW) values range from- 96‰to-59‰,and theδ18 Ofluid values range from 7.3‰to 10.3‰,and the value of δ^(34)S is from 4.15‰to 11.88‰.The zircon U-Pb concordant age of the diorite porphyrite is determined to be(220.7±1.0)Ma,with a weighted average age of(219.8±2.1)Ma.The findings indicate that the majority of the metallogenic materials at the Miaogou gold mine are derived from magmatic sources,with a minor contribution from the surrounding rock strata.The metallogenic fluids are of multiple origins,predominantly consisting of magmatic water.It is posited that the Miaogou gold mine was formed during the Late Triassic period.During this epoch,significant brittle-ductile shear deformation and magmatic activity were intimately associated with gold mineralization and alteration processes.These geological phenomena likely provided the necessary thermal energy and mineral sources,facilitating the activation,migration,and enrichment of siliceous materials and minerals within the early Paleozoic Luohansi rock group.These materials subsequently concentrated within the multi-fissures oriented in the west-north-east-south direction,associated with brittle-ductile shear deformation.The tectonic deformation,magmatic activity,and ore-forming enrichment events of the Late Indosinian period hold substantial significance.The Miaogou gold deposit is thus interpreted as a product of extensive and intense deformation,metamorphic-magmatic activity,and fluid interactions governed by the brittle-ductile shear zones during the Late Triassic.
作者
杜建华
朱德鹏
何虎军
杨兴科
张少华
豆浪浪
晁会霞
DU Jianhua;ZHU Depeng;HE Hujun;YANG Xingke;ZHANG Shaohua;DOU Langlang;CHAO Huixia(Shaanxi Geology and Mining Three Geological Team Co.,Ltd.,Baoji 721000,Shaanxi,China;Key Laboratory of Mineral Resources Exploration and Testing Research,Baoji 721000,Shaanxi,China;School of Earth Science and Resources,Chang’an University,Xi’an 710054,Shaanxi,China;Key Laboratory of Western China’s Mineral Resources and Geological Engineering,Ministry of Education,Chang’an University,Xi’an 710054,Shaanxi,China)
出处
《黄金科学技术》
北大核心
2026年第1期20-39,共20页
Gold Science and Technology
基金
陕西地矿集团有限公司科研青年专项资金项目(编号:KYQ202302)
陕西地矿集团有限公司科研专项资金项目(编号:KY202212)
陕西省地勘基金(编号:61201203100)
陕西省自然科学基金(编号:2023-JC-YB-261)联合资助。
