A natural laboratory for critical metals investigations in the Mourne Mountains granites

This is the final version. Available from the Royal Irish Academy via the DOI in this record.Certain metals that are vital for many modern technologies occur naturally in the Mourne Mountains Complex of County Down, Northern Ireland. These include niobium, tantalum and the rare earth elements. Using the Tellus geochemistry data and the results of more detailed sampling we have investigated their geological sources in granite bedrock and their dispersion in stream sediments. From this research, an exploration methodology has emerged that can assist in the search for critical metals globally. Planned follow-on studies include investigations of the environmental fate of these metals and the potentially toxic elements with which they are naturally associated.Department of Enterprise, Trade and Investmen

Integrated Object-Based Image Analysis for semi-automated geological lineament detection in Southwest England

This is the final version. Available on open access from Elsevier via the DOI in this record.Regional lineament detection for mapping of geological structure can provide crucial information for mineral exploration. Manual methods of lineament detection are time consuming, subjective and unreliable. The use of semi-automated methods reduces the subjectivity through applying a standardised method of searching. Object-Based Image Analysis (OBIA) has become a mainstream technique for classification of landcover, however, the use of OBIA methods for lineament detection is still relatively under-utilised. The Southwest England region is covered by high-resolution airborne geophysics and LiDAR data that provide an excellent opportunity to demonstrate the power of OBIA methods for lineament detection. Herein, two complementary but stand-alone OBIA methods for lineament detection are presented which both enable semi-automatic regional lineament mapping. Furthermore, these methods have been developed to integrate multiple datasets to create a composite lineament network. The top-down method uses threshold segmentation and sub-levels to create objects, whereas the bottom-up method segments the whole image before merging objects and refining these through a border assessment. Overall lineament lengths are longest when using the top-down method which also provides detailed metadata on the source dataset of the lineament. The bottom-up method is more objective and computationally efficient and only requires user knowledge to classify lineaments into major and minor groups. Both OBIA methods create a similar network of lineaments indicating that semi-automatic techniques are robust and consistent. The integration of multiple datasets from different types of spatial data to create a comprehensive, composite lineament network is an important development and demonstrates the suitability of OBIA methods for enhancing lineament detection.British Geological Survey (BGS)Natural Environment Research Council (NERC

Mechanisms for concentrating critical metals in granitic complexes: insights from the Mourne Mountains, Northern Ireland

This is the final version. Available from The Geological Society via the DOI in this record. The Tellus stream sediment and deep soil geochemistry data sets for Northern Ireland were used to locate four types of critical metals anomalies in granite bedrocks of the Mourne Mountains. A curvi-linear array of Nb, REE, Th and U soil anomalies across the eastern Mourne Mountains correlated with late-stage and eutectic temperature minerals in the roof zone of the most peralkaline F- and volatile-rich granite body, remobilized on micron to millimetre scales. Li, Be, B, As, Sn, Mn3+ and Ce4+ partitioned into pockets of late-stage heterogeneously distributed F-rich silicic residual melts and relatively oxidizing halide-rich magmatic fluids, resulting in drusy mineral and hydrothermal assemblages. Isolated soil anomalies correlated with amorphous Mn3+- and Ce4+-rich masses infilling drusy cavities, which resulted from short-distance percolation of small volumes of late-stage magmatic fluids. A significant As plume in stream sediments emanated from a greisen that hosted multiple critical and base metals including Sn, from reactions between large volumes of magmatic As + halide-rich fluids and mafic silicate + diverse accessory minerals on the metre- to kilometre-scale along geological structures. Diverse, small-scale REE anomalies in the soil data along structural features in the western Mournes correlate with vein mineralization resulting from episodic migration of hydrous fluids of variable composition, probably with a much smaller magmatic component than elsewhere. The regional geochemical dataset proved useful to develop a multi-stage model for enrichment of critical metals in the Mourne Mountains granites, which is analogous to the petrogenesis of some of the igneous-hosted economic deposits of critical metals.Department of Enterprise, Trade and InvestmentGeological Survey of Northern Irelan