Sasso di Castro, Futa Pass - Raticosa Pass area, Firenzuola, Metropolitan City of Florence, Tuscany, Italyi

Regional Level Types
Sasso di Castro	- not defined -
Futa Pass - Raticosa Pass area	Mountain Area
Firenzuola	Commune
Metropolitan City of Florence	Province
Tuscany	Region
Italy	- not defined -

Ophiolite body at Sasso di Castro (1276 m), a mountain located to the west of the Regional Road SR 65 (formerly State Road SS 65), 4 km NNE of Futa Pass.

The Sasso di Castro ophiolite is a huge olistolith within the chaotic complex (Late Cretaceous) of the external Liguride unit. The ophiolite consists of massive basalts cut by few dykes and overlain by pillow basalts which grade up into pillow basalt breccia covered by red cherts. The whole sequence was affected by ocean-floor metamorphism under static conditions from lower amphibolite to zeolite facies. As opposed to other occurrences in the Northern Apennines, the Sasso di Castro plagiogranites (trondhjemites and very scarce diorites) occur as two small stock-like bodies intruded in the lower part (massive basalt) of the effusive complex. The largest intrusion produced a small thermometamorphic aureole whose hornfelses reached lower amphibolite facies. The thermal effect was associated with fragmentation of the wall-rock and locally also with plastic deformation. Chemical exchange between the host massive basalts and the intruded plagiogranite body has been recognized. The plagiogranites, particularly the trondhjemites, have extremely low K₂O ( (>50) ratio.

A crushed stone quarry was opened in the ophiolite body to the west of the Regional Road SR 65 between km 48 and km 49 (coordinates 44.1231 N, 11.2876 E). This quarry is well-known for the occurrence of hyaline datolite crystals in hydrothermal veins crosscutting pillow basalt. In mineral collections this occurrence is often indicated as Futa Pass or Futa Pass quarry.

Furthermore, in the Sasso di Castro ophiolite the occurrence of andradite crystals and titanite has been reported from serpentinites and trondhjemites, respectively.



At the eastern foot of Sasso di Castro, within the Late Cretaceous chaotic complex, a limestone quarry (also known as Covigliaio or Boschetto quarry - coordinates 44.1310 N, 11.3032 E) was opened at "Il Boschetto", to the west of km 50 of the Regional Road SR 65, between the previously mentioned quarry and the village of Covigliaio. This quarry yielded yellowish scalenohedral calcite crystals, sometimes found in the form of butterfly twins.

Other Regions, Features and Areas containing this locality

References