代文军,谢建强,王晓伟.西秦岭早子沟金矿区花岗闪长斑岩地球化学特征及地质意义[J].甘肃地质,2023,(4):23-30
西秦岭早子沟金矿区花岗闪长斑岩地球化学特征及地质意义
Geochemical Characteristics and Geological Significance of Granodiorite Porphyry in Zaozigou Gold Mining Area, West Qinling
  
DOI:
中文关键词:  花岗闪长斑岩  岩石成因  地质意义  早子沟金矿区  西秦岭
英文关键词:granodiorite porphyry  petrogenesis  geological significance  Zaozigou gold mining area  West Qinling Mountains
基金项目:西秦岭地区地质大数据找矿靶区定量预测研究(202202)、甘肃省西秦岭东段金矿大数据找矿靶区定量预测研究(2022CX18)资助
作者单位
代文军 1. 甘肃省地矿局第三勘查院甘肃 兰州 730050 
谢建强 2. 甘肃省地质勘查基金管理中心甘肃 兰州 730000 
王晓伟 3. 甘肃省地质调查院甘肃 兰州 730000 
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中文摘要:
      早子沟金矿区除发育大量的中性岩脉(闪长玢岩、石英闪长玢岩和黑云闪长玢岩)外,还见有较多的中酸性岩脉—花岗闪长斑岩。为了解花岗闪长斑岩的成因及其与成矿关系,对其进行了岩石地球化学的系统 研究。研究表明,样品具有较高的w(SiO2)(65. 02% ~ 67. 31%)、w(Al2O3)(15. 31% ~ 17. 62%)、w(K2O)(3. 24% ~ 3. 86%)和较低的w(MgO)(1. 59% ~ 2. 93%);σ = 0. 56 ~ 1. 88,A/CNK = 0. 94 ~ 1. 08,属高钾钙碱性系列准铝质—过铝质花岗岩类。稀土总量中等(∑REE = 132. 70 × 10-6 ~ 211. 96 × 10-6),相对富集轻稀土,轻重稀土分馏明显(LREE/HREE = 12. 50 ~ 19. 12,LaN/YbN = 18. 62 ~ 40. 65),具弱的铕负异常(δEu = 0. 68 ~ 0. 84);原始地幔标准化分布模式图显示相对富集Rb、K、Th,亏损Ba、Nb、Ti等元素。构造环境判别显示出壳型和壳幔型岩浆弧的特征。结合区域地质背景,认为花岗闪长斑岩形成于俯冲背景下的陆缘弧环境,与三叠纪西秦岭地区碰撞造山导致的陆壳大规模拆离及加厚上地壳的部分熔融有关。花岗闪长斑岩常与中性岩脉伴生在一起或沿同一构造带先后侵位,其成岩时间稍早于中性岩脉,成矿时代与闪长玢岩形成时代基本一致,而稍晚于花岗闪长斑岩。说明花岗闪长斑岩等脉岩沿断裂构造的侵位和扩容,为金矿的含矿流体充填、沉淀富集提供了有利的空间。
英文摘要:
      In addition to the development of a large number of neutral dykes (diorite porphyrite, quartz diorite porphyrite and black cloud diorite porphyrite), there are more acidic dykes-granodiorite porphyry. In order to understand the genesis of granodiorite porphyry and its relationship with mineralization, a systematic study of rock geochemistry was carried out in this study. The results show that the samples have higher w(SiO2)(65. 02% ~ 67. 31%), w(Al2O3)(15. 31% ~ 17. 62%), w(K2O)(3. 24% ~ 3. 86%)and lower w(MgO) (1. 59% ~ 2. 93%); σ= 0. 56 ~ 1. 88, A/CNK = 0. 94 ~ 1. 08, it is a high potassium calcium alkaline series quasi-aluminous-peraluminous granite. The total amount of rare earths is medium(∑REE = 132. 70 × 10-6 ~ 211. 96 × 10-6), relatively rich in light rare earths, and the fractionation of light and light rare earths is obvious(LREE/HREE = 12. 50 ~ 19. 12, LaN/YbN = 18. 62 ~ 40. 65), with a weak negative europium anomaly (δEu = 0. 68 ~ 0. 84); the original mantle standardized distribution pattern shows that the relative enrichment of Rb, K, Th, Ba, Nb, Ti and other elements. The tectonic environment discrimination shows the characteristics of the crust-type and crust-mantle magmatic arcs. In summary and combined with the regional geological background, it is believed that the formation of the granodiorite porphyry in the continental margin arc environment under the subduction background is related to the large-scale detachment of the continental crust and the partial melting of the thickened upper crust caused by the collision orogeny in the western Qinling area of the Triassic. Granodiorite porphyry is often associated with neutral dikes or emplaced successively along the same tectonic zone, and its diagenetic time is slightly earlier than that of neutral dikes, and its metallogenic age is basically the same as that of diorite porphyry, but slightly later than that of granodiorite porphyry. It shows that the emplacement and expansion of granodiorite porphyry and other vein rocks along the fault structure provide a favorable space for the filling of ore-bearing fluids and precipitation enrichment of gold deposits.
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