Convolutional neural networks for mineral prospecting through alteration mapping with remote sensing data

Traditional geological mapping, based on field observations and rock sample analysis, is inefficient for continuous spatial mapping of features like alteration zones. Deep learning models, such as convolutional neural networks (CNNs), have revolutionised remote sensing data analysis by automatically extracting features for classification and regression tasks. CNNs can detect specific mineralogical changes linked to mineralisation by identifying subtle features in remote sensing data. This study uses CNNs with Landsat 8, Landsat 9, and ASTER data to map alteration zones north of Broken Hill, New South Wales, Australia. The model is trained using ground truth data and an automated approach with selective principal component analysis (PCA). We compare CNNs with traditional machine learning models, including k-nearest neighbours, support vector machines, and multilayer perceptron. Results show that ground truth-based training yields more reliable maps, with CNNs slightly outperforming conventional models in capturing spatial patterns. Landsat 9 outperforms Landsat 8 in mapping iron oxide areas using ground truth-trained CNNs, while ASTER data provides the most accurate argillic and propylitic alteration maps. This highlights CNNs' effectiveness in improving geological mapping precision, especially for identifying subtle mineralisation-related alterations.

Remote sensing framework for geological mapping via stacked autoencoders and clustering

Supervised learning methods for geological mapping via remote sensing face limitations due to the scarcity of accurately labelled training data. In contrast, unsupervised learning methods, such as dimensionality reduction and clustering have the ability to uncover patterns and structures in remote sensing data without relying on predefined labels. Dimensionality reduction methods have the potential to play a crucial role in improving the accuracy of geological maps. Although conventional dimensionality reduction methods may struggle with nonlinear data, unsupervised deep learning models such as autoencoders have the ability to model nonlinear relationship in data. Stacked autoencoders feature multiple interconnected layers to capture hierarchical data representations that can be useful for remote sensing data. In this study, we present an unsupervised machine learning framework for processing remote sensing data by utilizing stacked autoencoders for dimensionality reduction and k-means clustering for mapping geological units. We use the Landsat-8, ASTER, and Sentinel-2 datasets of the Mutawintji region in Western New South Wales, Australia to evaluate the framework for geological mapping. We also provide a comparison of stacked autoencoders with principal component analysis and canonical autoencoders. Our results reveal that the framework produces accurate and interpretable geological maps, efficiently discriminating rock units. We find that the stacked autoencoders provide better accuracy when compared to the counterparts. We also find that the generated maps align with prior geological knowledge of the study area while providing novel insights into geological structures.

A review of machine learning in processing remote sensing data for mineral exploration

As a primary step in mineral exploration, a variety of features are mapped such as lithological units, alteration types, structures, and minerals. These features are extracted to aid decision-making in targeting ore deposits. Different types of remote sensing data including satellite optical and radar, airborne, and drone-based data make it possible to overcome problems associated with mapping these important parameters on the field. The rapid increase in the volume of remote sensing data obtained from different platforms has allowed scientists to develop advanced, innovative, and powerful data processing methodologies. Machine learning methods can help in processing a wide range of remote sensing data and in determining the relationship between the reflectance continuum and features of interest. Moreover, these methods are robust in processing spectral and ground truth measurements against noise and uncertainties. In recent years, many studies have been carried out by supplementing geological surveys with remote sensing data, and this area is now considered a hotspot in geoscience research. This paper reviews the implementation and adaptation of some popular and recently established machine learning methods for remote sensing data processing and investigates their applications for exploring different ore deposits. Lastly, the challenges and future directions in this critical interdisciplinary field are discussed.