The Mud Tank carbonatite complex, central Australia —an example of metasomatism at mid-crustal levels
Abstract
The Mud Tank carbonatite complex comprises a series of lenses emplaced about 730 Ma ago along a 5 km segment of a ductile shear zone. Each lens consists of a carbonate core surrounded by mica-rich zones, emplaced into granitoid cataclasites, mafic granulites and rare lenses of aluminous rocks. Xenoliths of all sizes abound in the complex. Inclusions of unfoliated mafic granulites lack hypersthene, contain albitic plagioclase and Na-rich taramite to hastingsite amphiboles, and are enriched in Si, Na and Ba and depleted in Fe, Zr and Pb relative to similar granulites in the country rocks. Alkali-syenite inclusions contain riebeckite and aegirine. The complex contains magnesio-katophorite to magnesio-arfvedsonite amphibole, with late riebeckite and ferri-winchite, abundant phlogopitic mica and sparse acmitic pyroxene. Mineral thermobarometry suggests original emplacement at>650°C, 0.5 Gpa under high water and fluorine fugacities. Present configuration of the and entrainment of parts of the metasomatic aureole along shear zones. of abundant detrital magnetite, apatite and zircon drew attention to these bodies more than 40 years ago. A carbonatitic origin, first proposed by Crohn and Gellatly (1969), has been supported by aeromagnetic interpretation (Tipper 1966), preliminary geochemistry (Gellatly 1969), geochronology (Black and Gulson 1978) and stable isotope studies (Wilson 1979). Crohn and Moore (1984) reviewed earlier work, and concluded that alkali metasomatism typical of carbonatite complexes did not occur around the Mud Tank complex. We demonstrate that such metasomatism is present, but of unusual character.
- Publication:
-
Contributions to Mineralogy and Petrology
- Pub Date:
- January 1992
- DOI:
- 10.1007/BF00283322
- Bibcode:
- 1992CoMP..109..326C