Evaluation of the Possible Diagenetic Origin of Azurite Suns from the Malbunka Mine, Northern Territory, Australia

Event Center A & B

Unusual azurite “suns” from the Malbunka Copper Mine, Australia have carbon and oxygen isotope values consistent with formation under diagenetic conditions different from the conditions that azurite is commonly believed to form. Carbon isotope values suggest formation from diagenetic basin carbonate, and not marine limestone or atmospheric carbon, a more common genesis environment. Oxygen isotope values were used with established paleo thermometry equations, indicating the azurite disks formed at temperatures above ambient surface temperatures. These temperatures cannot be explained by a volcanic heat source, leaving deep formation as the probable environment. The formation of the azurite at 5 to 16⁰C above ambient surface temperatures would correlate to a depth of 0.3 to 1.6 km within the Amadeus basin. Morphological comparison of azurite disks with Ediacaran fossils suggests that these are not fossil replacements, despite rough similarities, as the azurite disks do not have bilateral symmetry. The evidence suggests that the Malbunka azurite disks formed in a unique environment, quite different than the textbook interpretation as a surface weathering product.