Contrasting coronas: microscale fluid variation deduced from monazite breakdown products in altered metavolcanic rocks associated with the Grängesberg apatite-iron oxide ore, Bergslagen, Sweden

Three different types of secondary coronas developed around monazite-(Ce) were discovered in altered metavolcanic rocks closely associated with the Palaeoproterozoic apatite-iron oxide ore deposit Grängesberg, Sweden. All three reaction include fluorapatite that is either rimmed by allanite-(Ce), REE-fluorocarbonate(s), or hingganite-(Y). The latter mineral has not been previously observed among monazite breakdown products. A unique feature described their spatial proximity to each other, exceeding a few hundreds micrometres. We infer observed, strongly contrasting assemblages highlight presence heterogeneous fluid mediated these microscale decomposition reactions. Thus, it emphasized metasomatic variability natural systems may often be too large predicted and reproduced experimentally.