Deducing the source and composition of rare earth mineralising fluids in carbonatites: insights from isotopic (C, O, 87Sr/86Sr) data from Kangankunde, Malawi

This is the final version of the article. Available from Springer Verlag via the DOI in this record.Carbonatites host some of the largest and highest grade rare earth element (REE) deposits but the composition and source of their REE-mineralising fluids remains enigmatic. Using C, O and 87Sr/86Sr isotope data together with major and trace element compositions for the REE-rich Kangankunde carbonatite (Malawi), we show that the commonly observed, dark brown, Fe-rich carbonatite that hosts REE minerals in many carbonatites is decoupled from the REE mineral assemblage. REE-rich ferroan dolomite carbonatites, containing 8–15 wt% REE2O3, comprise assemblages of monazite-(Ce), strontianite and baryte forming hexagonal pseudomorphs after probable burbankite. The 87Sr/86Sr values (0.70302–0.70307) affirm a carbonatitic origin for these pseudomorph-forming fluids. Carbon and oxygen isotope ratios of strontianite, representing the REE mineral assemblage, indicate equilibrium between these assemblages and a carbonatite-derived, deuteric fluid between 250 and 400 °C (δ18O + 3 to + 5‰VSMOW and δ13C − 3.5 to − 3.2‰VPDB). In contrast, dolomite in the same samples has similar δ13C values but much higher δ18O, corresponding to increasing degrees of exchange with low-temperature fluids (< 125 °C), causing exsolution of Fe oxides resulting in the dark colour of these rocks. REE-rich quartz rocks, which occur outside of the intrusion, have similar δ18O and 87Sr/86Sr to those of the main complex, indicating both are carbonatite-derived and, locally, REE mineralisation can extend up to 1.5 km away from the intrusion. Early, REE-poor apatite-bearing dolomite carbonatite (beforsite: δ18O + 7.7 to + 10.3‰ and δ13C −5.2 to −6.0‰; 87Sr/86Sr 0.70296–0.70298) is not directly linked with the REE mineralisation.This project was funded by the UK Natural Environment Research Council (NERC) SoS RARE project (NE/M011429/1) and by NIGL (NERC Isotope Geoscience Laboratory) Project number 20135

Affirming and reaffirming Indigenous presence: contemporary Aboriginal and Torres Strait Islander community, public and institutional architecture in Australia

The design of specific buildings to house Australian Aboriginal and Torres Strait Islander cultural artefacts, artworks, activities or organisations, has become important in Australian architecture since the 1960s. A growing number of buildings—and new architectural types—have been devised to support, display and safeguard Indigenous cultures and to accommodate Indigenous organisations that have become more prevalent since self-determination. These new public, institutional and community building typologies provide an architecture that often speaks to the both the Indigenous and non-Indigenous population. This chapter examines a number of different types of Indigenous institutional, public and community buildings, surveying architectural precedents within the genres of keeping houses and cultural centres, museums, art centres, educational and health projects. Some of Australia’s leading architects, Indigenous and non-Indigenous, have contributed to these works, seeking to create architecture that better fits the needs of Indigenous users, to participate in the recognition of the unjust treatment of Indigenous Australians, and to dignify contemporary Indigenous cultures through architectural excellence. Public, institutional and community buildings that cater to and purport to represent or make visible Indigenous communities have developed their own typologies during the twentieth century and continue to do so. The need for Indigenous input for buildings to function according to needs and expectations, and to reconcile decades of exclusion and racism still poses challenges for policy makers and architects alike. Evidence-based design that demonstrates improved health and wellbeing and educational outcomes in culturally appropriate buildings is occurring, but integration between research and design is needed, along with greater post-occupancy evaluation, and a commitment to learn from designs and their effect on Indigenous peoples and communities. Architecture and placemaking that celebrates cultural identity, fits with Indigenous socio-spatial and cultural needs, and is devised by or with Indigenous peoples, is an important aspect of making Indigenous cultures visible and demonstrating Indigenous resistance and resilience in contemporary Australia