IC30

Heavy mineral enrichments in beach deposits, known as ‘placers’, are common along many of the world’s coasts. Besides the economic importance of heavy minerals, such as gold, iron and other metals, they also serve as tracers for hydrodynamic and sedimentological conditions in coastal areas (Pupienis, 2011). Their nearly triple immersed weight per volume and generally finer grain sizes compared to particles of quartz and feldspar make it harder for littoral transport systems to mobilize and move such particles under normal conditions (Komar, 2007). Heavy mineral enrichments therefore represent lag deposits of high-energy events, e.g. storms, and processes.

Within this project, special focus is laid on magnetic minerals as placer deposits. Magnetic mineral enrichments are widespread as ‘ironsands’ or ‘black sand’ deposits on the northwest coast of New Zealand and well-studied because of their economic importance for the local titanium and ore industry (Badesab, 2012). However, New Zealand’s east coast of the North Island is only hardly examined for heavy mineral enrichments because of lower magnetic mineral contents and therefore less profitability. Layers of black sands are also found in beach sands in northern Europe at the North and Baltic Sea. The heavy mineral concentrations are similar to New Zealand’s northeast coast. Both coastal areas furthermore experienced a wide range of storm events in the past. Hence, this project aims at investigating the magnetic heavy mineral enrichment processes at the northeastern coast of New Zealand in comparison to the North and Baltic Sea of northern Europe with regard to high-energy events, especially storms. New sediment cores from beach sands will be collected at the northeast coast of New Zealand and North and Baltic Sea for the project. The cores will build the basis for high-resolution magnetic and stratigraphy analysis. The aim is to establish a magnetic stratigraphy along and across the shoreline. Understanding the spatial and temporal distribution of such placer deposits along the beaches will help to evaluate the impact, scale, sediment budget and recurrence time of specific high-energy event types. In a following step, heavy mineral enrichments in beach sands should be modelled. Beach erosion is thought to be the key condition under which thin layers or lens of black sands are formed (Komar, 2007). The acquired model should give answers to the questions, first, if storm events in the coastal areas of New Zealand and North and Baltic Sea are able to erode the beach sediments and second, if they are powerful enough to form the observed concentrations of heavy minerals in those coastal areas.


Pupienis, D., Buynevich, I. V. and Bitinas, A. (2011). Distribution and significance of heavy-mineral concentrations along the southeast Baltic Sea coast. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 1984-1988. Szczecin, Poland, ISSN 0749-0208.

Komar, P. D. (2007). Chapter 1 The Entrainment, Transport and Sorting of Heavy Minerals by Waves and Currents, In: Maria A. Mange and David T. Wright, Editor(s), Developments in Sedimentology. Elsevier, Volume 58, Pages 3-48, ISSN 0070-4571, ISBN 9780444517531.

Badesab, F., Dobeneck, T. von, Bryan, K. R., Müller, H., Briggs, R. M., Frederichs, T. and Kwoll, E. (2012). Formation of magnetite-enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand. Geochem. Geophys. Geosyst., 13, Q06012, doi:10.1029/2012GC004125.