基于机器学习的大洋玄武岩构造环境判别研究

Tectonic discrimination of oceanic basalt by machine learning

  • 摘要: 玄武岩的地球化学成分与其产出构造环境密切相关,是研究地球深部物质组成与动力学过程的重要岩石。为了判别玄武岩形成的构造环境,前人根据玄武岩的地球化学特征建立了一系列构造判别图,然而这些判别图仅限于二维或三维判别。随着全球玄武岩样品地球化学数据的爆发性增长,这些构造判别图逐渐暴露出其局限性强、准确率较低的缺点。在地学与大数据结合发展的背景下,利用机器学习方法有利于更全面和深入分析数据,建立高准确率和高效率的构造环境判别模型。因此,本文利用GEOROC和PetDB数据库,经过一系列数据下载、处理等步骤,建立了全球现代大洋玄武岩数据集。通过支持向量机(SVM)和随机森林(RF)机器学习算法,训练出高准确率的高维判别模型。本文分析了不同机器学习算法和不同地球化学成分数据集对现代大洋玄武岩构造环境判别的影响,并将各个判别模型应用于蛇绿岩数据当中,探讨机器学习模型在判别古老大洋岩石圈(蛇绿岩)形成构造环境下的应用前景。这项工作为大洋玄武岩形成的构造环境判别提供了更高维度的判别手段,是大数据时代下机器学习如何在地球科学领域应用的一次有益尝试。

     

    Abstract: The geochemical composition of basalt is closely related to the tectonic setting of the formation, thus basalt is an important window for viewing the deep Earth and the composition and geodynamic processes. To discriminate the tectonic setting of basalt formation, although a series of tectonic discrimination diagrams have been established based on the geochemical characteristics of basalt, those discrimination diagrams are limited to two-dimensional or three-dimensional data. With the explosive growth of global geochemical data of basalt, these discrimination diagrams show gradually the shortcomings of being local and inaccurate. Therefore, using machine learning methods is beneficial to analyze data multi-dimensionally and comprehensively, and to establish accurate and efficient discriminant models. A global modern oceanic basalt dataset was established by using GEOROC and PetDB databases through a series of steps from data downloading, training, and analyzing. The dataset was trained by the support vector machine (SVM) and random forest (RF) machine learning algorithms and a high-accuracy and high-dimensional discrimination model was built. In addition, the accuracies of different machine-learning algorithms training were analyzed against different geochemical composition datasets of modern oceanic basalt, and the discrimination models were applied to ophiolitic basalt to explore the application of machine learning models for ancient oceanic basalt. This work provided a higher-dimensional approach to discriminate oceanic basalt, and a successful attempt of using machine learning in earth science in the era of the big data.

     

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