Vecchia Miniera bauxite outcrop (Casamaina Mine), Lucoli, L'Aquila Province, Abruzzo, Italyi

Regional Level Types
Vecchia Miniera bauxite outcrop (Casamaina Mine)	Mine
Lucoli	Commune
L'Aquila Province	Province
Abruzzo	Region
Italy	- not defined -

Outcrop located in the NW sector of the Campo Felice plateau and mined in the period 1955-1975.

It consists of a bauxitic body of lenticular shape below a limestone hangingwall; the footwall contact is covered by debris and waste. The maximum thickness of the bauxite layer is 10 m, while its length is about 25 m. The bauxite texture is matrix-supported, with the oolites and clasts displaying
various degrees of rounding (from roughly fragmental to oolitic-pisolitic) and a medium-to-low sorting degree. On the top of the ore horizon, the hangingwall starts with an ochre to reddish pelitic level, which is covered by nodular-brecciated carbonates.

Bauxite mainly consists of böhmite, hematite, anatase, and rutile. Another common phase is gibbsite. Other minor hydroxides are goethite and lepidocrocite. An ubiquitous clay mineral is kaolinite. Accessory minerals are calcite and illite. The texture of the ore is mainly matrix-supported, and only locally grain-supported. The structure is generally oolitic and seldom oolitic-conglomeratic with rare pisolites. The oolites have a moderate compositional heterogeneity: part of them (from 50 up to 70%) are hematitic, and reddish brown to black. In addition, in many cases bauxite pebbles occur as rounded clasts embedded in a whitish clayey matrix. The oolites have a high degree of textural complexity, and in many cases, they are characterised by concentric textures, with bands of Fe oxides alternated with layers of Al hydroxides or böhmite rims grown upon hematite-rich cores. The matrix of the bauxite samples is mainly kaolinitic, finely inter-mixed with böhmite and/or Fe oxy-hydroxides. Both the oolites and the matrix enclose a wide range of fine-grained (diameter < 30 μm) heavy minerals such as REE phosphates (monazite and xenotime), ilmenite, baddeleyite, rutile, and zircon. These phases exhibit smooth to angular surfaces and broken crystal forms, which highlight a certain degree of transport and thus their detrital origin. REEs authigenic minerals, such as fluoro-carbonate (parisite) and florencite-like phases, were also detected in cavities of the rocks. The florencite-like phases show high Ce (Ce₂O₃ average value = 25.72 wt.%, 1.07 a.p.f.u. Ce), and minor La (average La₂O₃ content = 12.20 wt.%, 0.51 a.p.f.u. La) and Nd amounts (Nd₂O₃ average value = 7.98 wt-%, 0.32 a.p.f.u. Nd). Concerning the chemistry of the florencite-like phases, it must be highlighted that a significant LREE (light rare earth elements) excess and a slight Al deficiency have been detected in the Abruzzo samples, in comparison with the classical florencite.

References

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