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现代地质 ›› 2025, Vol. 39 ›› Issue (03): 523-540.DOI: 10.19657/j.geoscience.1000-8527.2025.001

• 机器学习与矿物学应用 • 上一篇    下一篇

基于机器学习的黑云母成分判别花岗岩成因类型方法研究

孙玉洁(), 李晓彦, 张超*()   

  1. 大陆动力学国家重点实验室,西北大学地质学系,陕西 西安 70069
  • 出版日期:2025-06-10 发布日期:2025-07-03
  • 通信作者: *张 超,男,教授,1982年出生,主要从事岩石地球化学和实验岩石学研究工作。Email:zhangchao@nwu.edu.cn
  • 作者简介:孙玉洁,女,硕士研究生,2000年出生,主要从事岩石学研究工作。Email:syj243660@outlook.com
  • 基金资助:
    科技部重点研发计划项目(2023YFF0804200)

Machine-learning Based Discrimination of Granite Type Using Biotite Composition

SUN Yujie(), LI Xiaoyan, ZHANG Chao*()   

  1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, Shaanxi 710069, China
  • Published:2025-06-10 Online:2025-07-03

摘要:

花岗岩成因分类方案的合理性和可操作性仍然备受争议。黑云母作为花岗质岩浆结晶分异过程中重要的镁铁质矿物相,其化学成分能够反映岩浆的物理化学条件和演化历程,这为建立花岗岩成因判别指标提供了关键矿物学依据。本文对来自I型、S型和A型花岗岩的1455个黑云母的主量元素数据进行了统计分析,结果表明:I型花岗岩的黑云母SiO2、TiO2、MgO和MnO的含量较高,S型花岗岩的黑云母则较为富含Al2O3和Na2O,A型花岗岩的黑云母FeOT的含量较高。通过黑云母成分估算表明,I型花岗岩形成于相对高温、低压和高氧逸度环境,而S型花岗岩通常形成于相对高压环境,氧逸度和温度均低于I型花岗岩。I型、S型和A型花岗岩中黑云母的F和Cl含量和富集程度也有明显的区别,其中A型花岗岩中的黑云母F和Cl的含量相对最高。黑云母成分具有判别花岗岩成因类型的巨大潜力,但已有的基于黑云母成分的分类模型仍存在较大不确定性。为了进一步提高黑云母成分对于花岗岩类型的识别可靠程度,本研究对比了基于黑云母离子占位数据应用了PCA、t-SNE、UMAP降维机器学习算法和基于决策树的随机森林(RF)、极端随机树(ERT)、梯度提升决策树(GBDT)、极端梯度提升(XGBoost)、轻量梯度提升(LightGBM)和CatBoost机器学习模型算法,对I型、S型和A型花岗岩成因类型进行判别。结果显示,PCA、t-SNE、UMAP降维算法的判别准确率较低,而基于决策树的机器学习模型能够以94.5%以上的准确率对花岗岩类型进行判别。其中,T.Al、T.Fe3+、M.Al、M.Mg和M.Mn等5个阳离子占位是影响机器学习模型分类结果的关键预测因子。基于黑云母成分构建的花岗岩成因类型判别标尺,为解析岩浆源区性质与演化过程提供了定量矿物地球化学约束。

关键词: 黑云母, 机器学习, I型花岗岩, S型花岗岩, A型花岗岩

Abstract:

The chemical composition of biotite can reflect the physical and chemical conditions and evolution process of magma. This study collected the EPMA data of 1455 biotite samples derived from I-type,S-type,and A-type granites to explore their differences and intrinsic association with granite type. The results show that the biotites from I-type granite are relatively rich in SiO2,TiO2,MgO,and MnO,while the biotites from S-type granite are relatively rich in Al2O3 and Na2O,and the biotites from A-type granite are relatively rich in FeOT. Based on the chemistry of biotites from I-type,S-type,and A-type granites,The I-type granite forms in a relatively high temperature,low pressure,and high oxygen fugacity environment. In contrast,the S-type granite usually forms in a relatively high-pressure environment,and the oxygen fugacity and temperature are lower than those of the I-type granite. The F and Cl contents and enrichment extent of biotite from different granite types are also significantly different,with relatively highest F and Cl contents in the biotites from A-type granites. Previous studies have shown that biotite composition has excellent potential to distinguish the genetic types of granites,but the existing classification models based on biotite composition still have significant uncertainty. PCA,t-SNE,UMAP dimensionality reduction methods and decision tree-based random forest (RF),extreme random tree (ERT),gradient boosting decision tree (GBDT),extreme gradient boosting (XGBoost),lightweight gradient boosting (LightGBM)and CatBoost machine learning model algorithms were applied to identify I-type,S-type and A-type granites based on calculated molar proportions of cation assignment in the biotite formula. The results show that PCA,t-SNE,and UMAP dimensionality reduction methods are not ineffective in distinguishing different granite types. In contrast,machine learning models based on decision trees can effectively identify granite types with more than 94.5% accuracy. In the biotite formula,T.Al,T.Fe3+,M.Al,M.Mg,and M.Mn are the five key cation assignments that affect the classification of machine-learning models.

Key words: biotite, machine learning, I-type granite, S-type granite, A-type granite

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