Mineralogy, chemistry, and fluid-aided evolution of the Pea Ridge Fe oxide-(Y + REE) deposit, southeast Missouri, USA

The Kiruna-type Pea Ridge iron oxide-apatite (IOA) deposit is hosted by a sequence of 1.47 Ga rhyolite tuffs of the St. Francois Mountains, southeast Missouri, USA. It consists of a series of altered zones composed mainly of amphibole, magnetite, hematite, and quartz, together with the presence of several rare earth element (Y + REE)-rich breccia pipes. In many cases, the fluorapatite within these zones is rich in inclusions of monazite, iron oxide, and quartz inclusions, plus minor xenotime. Monazite and minor xenotime are also found intergrown as inclusions in the fluorapatite, as well as in surrounding recrystallized magnetite and hematite in the magnetite ore. Monazite and xenotime typically occur as inclusions within both oxides. Monazite-(Ce) and xenotime-(Y) are both relatively poor (