From Sink to Source: Using Stream Sediment Geochemistry for Element Concentration Maps for Indonesia

The energy transition has seen the demand for low-carbon technologies increase. As such, there is a growing need for Energy Critical Elements (ECEs) which are used prominently in these low-carbon technologies (e.g., wind turbines, electric cars) for both energy generation and storage. Whilst recent research has focused on the potential global distribution of mineral resources (Dushyantha et al., 2020), the key ECEs (e.g., Cu, Nd, Dy, Li, Co, Ni, and Ag) are produced from limited sources. For example, 70% of global cobalt is produced from the Democratic Republic of Congo (e.g., Sun et al., 2019). The UK Government ‘Resilience for the Future’ Critical Minerals Strategy (2023) highlights the importance of collaborating with international partners and ensuring a sustainable pipeline of these resources from the source to the final production of low-carbon technologies. One area that could be key for diversifying the pipeline of ECEs is Indonesia, which has an enormous unmapped geological potential for ECE enrichment (Wang et al., 2023).

Indonesia has an intricate tectonic framework that has undergone multiple phases of subduction, arc-formation, and collision between a series of separate continental fragments that separated from the supercontinent Gondwana during the Phanerozoic era (Hall, 2012). These fragments then moved northward until they sequentially amalgamated to form modern-day Indonesia. During this, certain regions along the margins of these fragments, for example near the remains of the ancient volcanic arcs (e.g., Webb et al., 2020), have become enriched in mineral resources (Zaw et al., 2014). These areas have the potential to host deposits of ECEs, including a) volcanic arc related Cu-Au porphyry skarn deposits, epithermal deposits, and Au, Ag, Pb, and Zn, b) mafic to ultramafic rock related chromite, Rare Earth Elements (REEs), and Ni, c) intraplate sedimentary exhalative deposits (SEDEX), and d) granitic intrusion related volcanic massive sulphides (VMS) alongside W, Sn, Pb, Cu, Au, Pb, and Zn. Even though Indonesia has known occurrences of base metal deposits typically associated with ECEs, such as copper and gold, it is noteworthy that it reports some of the lowest documented reserves of ECEs.

To gain a deeper insight into the regional distribution of potential ECE accumulations in Indonesia, this project will utilise stream sediment geochemistry data to create maps that pinpoint areas of high ECE potential (e.g., Eskdale et al., 2023). The data for this stream sediment geochemistry will primarily be sourced from existing literature, but to enhance and verify the precision of the maps in regions with limited data, a field season will be conducted to collect additional stream sediment samples. Subsequently, this geochemical dataset will be interrogated in both ESRI ArcGIS and ioGAS to generate maps highlighting the concentration of elements. These maps will reveal regions with elevated ECE content in stream sediments, thereby indicating the likely presence of ore bodies in the surrounding geological formations. If successful, this workflow will be further developed such that the generated models of enrichment can be applied elsewhere (e.g., North Africa), especially those that have similarly complex geological histories.

The primary objectives of this PhD project are:

1. Curate a Stream Sediment Geochemical Database: Compile existing published data on stream sediment geochemistry and perform additional geochemical analysis on stream sediment samples.

2. Identify Data Gaps: Utilise ArcGIS to generate distribution maps of geochemical data. Use this to identify regions lacking sufficient data and plan targeted field campaigns to collect missing data.

3. Modelling Geochemical Signatures for ECE Concentration Maps: Use ioGAS to develop predictive models based on geochemical signatures and generate concentration maps for Economically Critical Elements (ECEs) from these models.

4. Model Validation through Host Rock Analysis: Analyse potential host rocks as indicated in the ECE concentration maps to verify the accuracy of the models and refine them if necessary.


This project will combine data science, fieldwork, and geochemistry to address a time-critical global issue.

A Stream Sediment Geochemistry Database will be compiled by collecting relevant stream sediment geochemistry data from peer-reviewed literature and official reports, focusing on Indonesian regions. Training will be given on data handling to ensure the data’s quality, geographical relevance, and temporal significance. The data will then be standardised by normalising data formats, units, and metadata to create a consistent, uniform dataset.

Geographic Information System (GIS) software will be used to integrate geological data from the Geological Data and Research Center (GDRC) with the stream sediment geochemistry data from the database. Maps will be created to illustrate how geological boundaries interact with element anomalies. Contour maps will be developed from the database to generate element heat maps, highlighting areas with potential element enrichment within host rocks.

ioGAS-64 will be used for prospectivity analysis of Element Concentrate Element (ECE) anomalies. Training will be provided for data handling, including techniques like Principal Component Analysis, and statistical tools like K-means clustering.

Collected stream sediment samples will be analysed using X-ray Fluorescence (XRF) to identify major and minor elements, with a specific focus on ECEs and associated elements. Host rocks will be analysed both geochemically (via XRF) and through Scanning Electron Microscopy with Electron Dispersive Spectrometry (SEM-EDS) to create in-situ element concentration maps. Reflected light microscopy will be used to validate SEM-EDS results.

The student will be trained in planning and executing fieldwork campaigns in remote areas. This will include instruction on engaging with local stakeholders and collecting samples to add to the databases and maps of potential ECE-bearing host rock concentrations. This training includes remote sensing techniques to plan safe access routes and locate areas with potential exposures

Project Timeline

Year 1

Year 1 Objectives:
• Assemble geochemical database of stream sediment from Indonesia using published literature, GDRC maps, and SEARG legacy data.
• Review literature on tectonics, volcanism, magmatism, and mineral resources in Indonesia.
• Spatial analysis using ArcGIS to identify potential source areas for ECEs and to identify regions lacking data.

Year 2

Year 2 Objectives:
• Use the ArcGIS maps to plan a 30-day field expedition around Indonesia.
• Sample areas otherwise lacking stream sediment geochemical data and target potential host rocks for ECEs in identified source halos.
• Detailed geochemical analysis of collected samples (e.g., XRF, SEM-EDS)
• Complete ArcGIS maps using the new data.
• Share research findings with the wider community through a national conference (e.g., MDSG)

Year 3

Year 3 Objectives:

• Utilize ioGAS for stream sediment geochemistry modelling.
• Identify regions with potential ECE enrichment.
• Validate ioGAS model by analysing the potential host rocks from the field season (e.g., SEM-EDS, reflected light microscopy)
• Present refined models and findings at an international conference (e.g., EGU)

Year 3.5

The final 6 months of the project will focus on finalising the writing of the thesis, as well as finishing off any papers in progress.

& Skills

The student will receive rigorous training in the field of Southeast Asian geology from leading experts in areas such as tectonic history, volcanism, magmatism, the potential for metallogenesis, and stream sediment geochemistry. The student will also undergo extensive field training, which includes operating in tropical environments and mastering sampling techniques, particularly in areas where bedrock is susceptible to heavy weathering.

Computational skills will involve learning effective database generation, using ArcGIS ioGAS to not only enhance the student’s statistical abilities but also equip them with the means to handle large datasets effectively. There will also be in-depth training in geochemical techniques, including XRF and SEM-EDS.

The training will extend beyond technical skills to encompass essential transferable skills. These will include project management, scientific writing, and presentation skills through Heriot-Watt University’s Postgraduate Researcher Development Programme. The student will also be encouraged to participate in national and international conferences and publish their findings in peer-reviewed journal articles. Given the broad societal implications of the subject, the training will also include guidance on public engagement and the effective dissemination of scientific knowledge to diverse audiences. The student will also have access to BGS resources for the entirety of this project, including training from experts at the BGS/NERC centres.

References & further reading

Dushyantha, N., Batapola, N., Ilankoon, I.M.S.K., Rohitha, S., Premasiri, R., Abeysinghe, B., Ratnayake, N. and Dissanayake, K., 2020. The story of rare earth elements (REEs): Occurrences, global distribution, genesis, geology, mineralogy and global production. Ore Geology Reviews, 122, p.103521.

Eskdale, A., Johnson, S.C. and Gough, A., 2023. The applicability of G-BASE stream sediment geochemistry as a combined geological mapping, and prospective exploration tool for As-Co-Cu-Ni mineralisation across Cumbria, UK. Journal of Geochemical Exploration, 253, p.107297.

Hall, R., 2012. Late Jurassic–Cenozoic reconstructions of the Indonesian region and the Indian Ocean. Tectonophysics, 570, pp.1-41.

Sun, X., Hao, H., Liu, Z., Zhao, F. and Song, J., 2019. Tracing global cobalt flow: 1995–2015. Resources, Conservation and Recycling, 149, pp.45-55.

UK Critical Minerals Strategy: https://www.gov.uk/government/publications/uk-critical-mineral-strategy

Wang, D., Lin, F., Shi, M., Wang, H. and Yang, X., 2023. Geological setting, tectonic evolution and spatio-temporal distributions of main mineral resources in South East Asia: A comprehensive review. Solid Earth Sciences.

Webb, M., White, L.T., Manning, C.J., Jost, B.M. and Tiranda, H., 2020. Isotopic mapping reveals the location of crustal fragments along a long-lived convergent plate boundary. Lithos, 372, p.105687.

Zaw, K., Meffre, S., Lai, C.K., Burrett, C., Santosh, M., Graham, I., Manaka, T., Salam, A., Kamvong, T. and Cromie, P., 2014. Tectonics and metallogeny of mainland Southeast Asia—a review and contribution. Gondwana Research, 26(1), pp.5-30.

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