2. Geological background
2.1. The Mediterranean area
The geological complexity observed in the Mediterranean area is mainly the result of a composite paleogeographical and geodynamical evolu9on due to the rela9ve movements between African and European plates (Fig. 1).
Fig. 1: Simplified tectonic map of the Mediterranean region (Pla:, 2007)
The geotectonic processes involving this area can be schema9cally divided into four main phases:
1. Opening Oceanic phase (Middle Jurassic -‐ Upper Jurassic); 2. Transi9on phase (Lower Cretaceous);
3. Oceanic convergence phase (Late Cretaceous -‐ Middle Eocene); 4. Con9nental collision phase (from Late Eocene).
The first two phases are responsible for the forma9on of different oceanic and con9nental domains that will be involved during the convergence and collisional phases. The convergence started in the Late Cretaceous had as a major effect the forma9on of important orogenic belts all around the Mediterranean area (PlaQ, 2007 and references therein).
2.2. The Apennines
The Apennines are a mountain range along approximately 1200 km through the Italian peninsula, drawing an arc from north to south with the convex side facing the Adria9c Sea.
The Colle di Cadibona in Liguria forms the northern end, while the Aspromonte gives the southern end, across the StreQo di Messina to Calabria. The width extension of the Apennines varies from a minimum of 30 km to a maximum of 250 km. The Appennines are usually subdivided in two zones: the Northern and the Southern Apennines characterised by different deforma9on styles, exten9on rate and orienta9on (PlaQ, 2007). These two sectors are joined in correspondence of an important lithospheric discon9nuity represented by Ortona-‐Roccamonfina line (Di Bucci & Tozzi, 1991). The Northern Apennines have an extension of more than 500 km, from Liguria to Abruzzo, and is separated from the Alps by the Sestri-‐Voltaggio line (Scholle, 1970; Crispini & Capponi, 2007). They have a predominant NW-‐SE structural direc9on and the tectonic style is dominated by thrust with both duplex structures and imbricate fans. The building structure can be defined as a thrust-‐and-‐fold belt, consis9ng of sets of strongly deformed superimposed tectonic units. The Southern Apennines includes Abruzzo, Molise and Campania, and has a predominant NE-‐SW direc9on. The tectonic style is dominated by large-‐scale duplex (Cello & Mazzoli, 1998).
The Apennine chain has been formed as a result to the convergence and collision between the African and European plates. The convergence started in the Late Cretaceous caused the collision (from the Eocene) between Sardinia-‐Corsica Massif and Adria, two microplates belonging to the European and African domains respec9vely. During the convergence the Apennines area experienced a series of kinema9c processes (subduc9on, back-‐arc basin opening, strike-‐slip faul9ng and lateral extrusion of lithospheric blocks). The convergence produced a W-‐dipping subduc9on of the Adria microplate below Sardinia-‐ Corsica block with the opening of back-‐arc basins (Provençal Basin; Southern Tyrrhenian Basin) (Fig. 2).
Fig. 2: Present-‐day tectonic framework and deep structure of the central Mediterranean region (Faccenna et al., 2007)
Different sectors of the orogenic chain have undergone these processes in different 9mes due to eastward subduc9on zone retreat and slab rollback. For these reasons, both the compressional (crustal thickening and stacking of tectonic units) that the extensional phases (back-‐arc basin opening of the western Mediterranean) migrated through 9me from west to east (Faccenna et al., 2007 and references therein). Related to the extensional phase occurred the magma9sm involving different sources and capable of producing the complexity of the Italian magma9sm (Serri et al., 2001).
2.3. Tuscany
Tuscany is located in the inner part of the Northern Apennines. In this area 4 different paleogeographic domains crop out, from top to boQom as follows:
1. Ligurian Domain: characterized by oceanic rocks (Jurassic) and their sedimentary cover (Cretaceous-‐Eocene).
2. Sub-‐Ligurian Domain: it represent the transi9on zone between the oceanic crust (Ligurian Domain) and con9nental crust (Tuscan Domain), covered by terrigenous turbidi9c sediments (Late Cretaceous -‐ Oligocene).
3. Tuscan Domain: it is divided into two subunits. The Internal Tuscan sub-‐ Domain (Tuscan Nappe) is composed of non-‐metamorphic rocks and/or very low grade (anchizone metamorphism), consis9ng of evaporites (Upper Triassic) followed by carbonate-‐siliceous sequence (Early Jurassic – Early Cretaceous), and a clayey and turbidi9c succession (Cretaceous -‐ late Oligocene). The External Tuscan sub-‐Domain (e.g., Autoctono Apuano, Mon9 Pisani and Mon9ciano-‐Roccastrada Units) show similar stra9graphic sequence but was metamorphosed in greenschist facies condi9ons. This stra9graphic sequence overlies a Paleozoic basement composed of phyllite-‐quartzite and micaschist (Silurian -‐ Devonian), sandstone and phyllite (Middle-‐Late Carboniferous – Early Permian) and meta-‐conglomerates, quartzi9es and phyllite (Verrucano; Middle-‐ Early Triassic).
4. Umbria-‐Marche Domain: it is formed by con9nental deposits overlying a Permian – Triassic basement. The sedimentary sequence begins with evaporites (Upper Triassic) followed by a sequence of carbonate rocks (Early Jurassic -‐ Eocene), and terrigeneous sequence (Eocene -‐ Pliocene) (Decandia et al., 2001 and references therein).
During the Neogene an extensional phase affected the Tuscany area. This area can be divided into two por9ons separated by the Livorno-‐Sillaro line and according to their extension rate. The Livorno-‐Sillaro is the main strike-‐slip fault of the Northern Apennines and is SW-‐NE oriented.
The opening of the Northern Tyrrhenian Basin is the principal evidence of ac9ve extension since Early – Middle Miocene. Various authors dis9nguish two (Carmignani et al., 1994) or three (Decandia et al., 2001) different extensional events, but both are in agreement with an early stage (D1 for Carmignani et al., 1994; D1 and D2 for Decandia et al., 2001) characterized by low-‐angle extensional faults. The faults cause the omission of parts of the Tuscan Nappe stra9graphic sequence. This structural characteris9c is commonly known as "Serie RidoQa". This early extensional stage produced an extension rate exceeding 120% during Late Oligocene -‐ Late Tortonian (Carmignani et al., 1994). The extensional late phase (D2 for Carmignani et al., 1994; D3 for Decandia et al., 2001) is characterized by high-‐angle normal faults oriented NNW-‐SSE and N-‐S. The horst and graben structures developed during this second phase and are cut by strike-‐slip faul9ng oriented SW-‐NE (e.g., Livorno-‐Sillaro
Line). The es9ma9on of the extensional rate does not exceed 10% (Carmignani et al., 1994) (Fig. 3).
Fig. 3: Structural-‐geological sketch map of Northern Apennines (Decandia et al., 2001)
Some authors propose that the compressional tectonics in Northern Appennines con9nue un9l Pliocene or Pleistocene 9mes also with mul9ple compression-‐extension transi9ons (Finei et al., 2001; Bonini & Sani, 2002; Musumeci et al., 2008). Boccalei et al., (2011) propose a superposi9on of a shallow extensional stress field with a deeper level compression.
The thinning of the con9nental crust reaches a minimum (about 25 km depth) at the border of the Tyrrhenian Sea in Southern Tuscany (PlaQ, 2007 and references therein). This thinning produced mantle doming beneath the Southern Tuscany, which is the cause of a high heat flow, as demonstrated by the presence of numerous geothermal fields (e.g., Larderello-‐Travale, M. Amiata) and magma9sm (Tuscan Magma9c Province -‐ TMP).
Another important geophysical feature is the presence in the upper mantle of an area with low seismic velocity interpreted as tectonic slice of upper crust within the mantle (crustal doubling) or as par9ally molten mantle material (e.g., metasoma9c veins) (Peccerillo & Dona9, 2003; Peccerillo, 2005).
2.3.1. The Tuscan Magma=c Province (TMP)
igneous rocks in a certain region showing spa9al and temporal rela9onships. Subsequently, Washington (1906), in order to emphasize this concept, used the term comagma9c, to indicate a common origin for magma9c rocks of a certain region. The defini9on that is commonly used for the Tuscan Magma9c Province (TMP) provides only temporal and spa9al rela9ons, but not gene9c. In the TMP all the igneous rocks are grouped in the inner part of Northern Appennines chain emplaced aler the con9nental collision began.
The outcrop area of TMP rocks can be confined between the Sardinia-‐Corsica block to west, the 41°N parallel to south (one of the principal lithospheric discon9nuity), and the Ancona-‐Anzio line to east. The TMP is characterized by a suite of magma9c rocks, from intrusive to effusive and from felsic to mafic that had been emplaced since about 14 Ma. According to the eastward subduc9on zone retreat the age of magma9c rocks is gradually younger proceeding from W (Sisco, 14 Ma) to E (e.g., Monte Amiata, 0.3-‐0.2 Ma; Torre Alfina, 0.88 Ma) (Innocen9 et al., 1992).
According to Innocen9 et al., (1992), they can be divided, on the basis of the temporal and spa9al distribu9on, into 4 dis9nct phases:
Phase 1: The emplacement of the lamproi9c magmas at Sisco in northeastern Corsica (the oldest and the most westernmost magma9c rocks of TMP). These rocks are interpreted as the first products related to post-‐collisional extensional phase that affects the inner part of the Apennines.
Phase 2: it took place between 7.3 and 6.2 Ma and it includes the Montecristo pluton (about 7.1 Ma), the Vercelli seamount (about 7.2 Ma), the western magma9c complex at Elba Island (about 8 to 6.85 Ma) and the first period of ac9vity of the composite Capraia volcano (about 7.6 -‐ 7 Ma) (Innocen9 et al., 1992).
Phase 3: it is documented by the Porto Azzurro pluton (about 5.9 Ma), Giglio (about 5 Ma), Campiglia Mariima and San Vincenzo Rhyolites (about 5.7 -‐ 4.3 Ma), Castel di Pietra hidden intrusion (about 4.3 Ma), Monteverdi (about 3.8 Ma) and Roccastrada (about 2.5 to 2.2 Ma). This phase also included the Orcia9co (about 4.1 Ma) and Monteca9ni Val di Cecina (about 4.1 Ma) lamproites, the second period of ac9vity of Capraia (about 4.6 -‐ 3.5 Ma) and the volcanic rocks of Tolfa district (about 4.2 -‐ 1.8 Ma) (Innocen9 et al., 1992).
Phase 4: it took place between 1.3 Ma and 0.3 -‐ 0.2 Ma. It include Radicofani (about 1.3 Ma), Mon9 Cimini (about 1.3 to 0.94 Ma), Torre Alfina (about 0.88 Ma) and Monte Amiata (about 0.3 -‐ 0.2 Ma) (Barberi et al., 1967; Innocen9 et al., 1992; Dini et al., 2002; Peccerillo & Dona9, 2003; Perugini & Poli, 2003; Rocchi et al., 2003; Fig. 4).
Fig. 4: LocaLon map for the Tuscan MagmaLc Province. Also reported are the younger potassic– ultrapotassic volcanic rocks of the Roman MagmaLc Province (Dini et al., 2002)
The TMP is a complex magma9c province with magma9c rocks ranging from felsic (granites and peraluminous rhyolites) to intermediate and mafic rocks (high-‐K calcalkaline, shoshoni9c, alkaline potassic and ultrapotassic lamproi9c). For these reasons, the TMP is not a comagma9c province because the variability observed cannot be explained through differen9a9on processes from a unique original magma type. Moreover, it should be emphasized that almost all magma9c rocks recorded mixing processes between two end-‐ members: a crustal-‐anatec9c magma and a mantle-‐derived magma (Peccerillo & Dona9, 2003 and references therein).
The felsic rocks, generated by processes of crustal anatexis, as indicated by the petrological, geochemical and isotopic data, can be lava flows (San Vincenzo, Roccastrada, Monte Amiata and Mon9 Cimini), plutonic bodies (Elba Island, Montecristo, Giglio, Gavorrano, Campiglia Mariima, seamounts in the Tyrrhenian Sea and hidden intrusions) and, more rarely, pyroclas9c rocks (Mon9 Cimini and Tolfa). For all the felsic rocks of the TMP the petrographic (including the presence of mafic), geochemical and isotopic data (disequilibrium among phenocrysts, between phenocrysts and groundmass and varia9on of the 87Sr/86Sr ra9o) are in agreement with a mixing between crustal anatec9c melt and
mantle-‐derived mafic magmas (Peccerillo & Dona9, 2003 and references therein). Only the acid rocks of Roccastrada, show high and not very variable 87Sr/86Sr ra9o (about 0.718 –
0.720) and low 143Nd/144Nd ra9o (about 0.51222), peralluminous minerals (e.g., cordierite)
and absence of mafic enclaves. These data suggest for Roccastrada rhyolites a genesis from only con9nental crustal materials by par9al fusion of probably metapelites (Peccerillo & Dona9, 2003 and references therein). The geochemical models on the mel9ng of gneiss with similar composi9ons to rocks in the Tuscan metamorphic basement can explain the genesis of the anatec9c melt (Fig. 5).
The mafic rocks with MgO > 4 wt% form small plutonic bodies, lava flows and enclaves in felsic rocks. The high values of Ni, Cr and Mg# with the presence, in some outcrops, of ultramafic xenoliths point to a mantle-‐derived magmas. The TMP mafic rocks are characterized by a highly variable geochemical and isotopic composi9on that indicates strong heterogeneity in the mantle sources (Peccerillo & Dona9, 2003). These rocks iden9fy a con9nuous trend between potassic rocks with lamproi9c affinity, ultrapotassic calcalkaline and shoshoni9c rocks. Lamproi9c rocks have been found in Monteca9ni Val di Cecina, Orcia9co, Torre Alfina and Sisco. The lamproi9c magma are characterized by low CaO, Al2O3
and Na2O and high K2O. Other important characteris9cs are the rela9vely high SiO2 content
with silica oversatura9on and the geochemical fingerprint with typical values of crustal materials rather than mantle ones. Capraia and Radicofani show the lowest concentra9ons of incompa9ble elements but the extreme value of the 87Sr/86Sr (Capraia, 0.708 -‐ 0.709;
Radicofani, 0.713 -‐ 0.716). These data suggest a genesis by a metasoma9zed mantle source rocks due to contribu9on of upper crust materials (subduc9on). Experimental studies suggest origin by mel9ng of superficial mantle perido9tes depleted in clinopyroxene (e.g., residual harzburgite) and enriched in a K-‐rich phase, such as phlogopite (Peccerillo & Dona9, 2003 and references therein).
Fig. 5: IniLal 143Nd/144Nd vs 87Sr/86Sr plot for Tuscan MagmaLc Province samples
(modified aVer Dini et al., 2002).
Calcalkaline and shoshoni9c rocks show lower enrichment in K2O and incompa9ble
elements and higher amounts of CaO, Na2O and Al2O3 than lamproi9c but the trends of
incompa9ble elements are similar. Also, for these rocks has been hypothized par9al mel9ng of mantle metasoma9zed rocks with probably lherzoli9c composi9on. In this case the metasoma9sm was less intense.
The petrogenesis of the TMP rocks can be divided into three main stages:
1. Subduc9on of upper crust with different degree of metasoma9c processes. These processes yielded a highly heterogeneous and anomalous mantle with geochemical fingerprint similar to the upper crust;
2. Mafic magma genesis (calcalkalinic, shoshoni9c and lamproi9c) from par9al mel9ng of heterogeneous mantle with geochemical and isotopic crustal signature;
3. Injec9on of mafic magmas in the con9nental crust with crustal anatexis and mixing between felsic and mafic magmas.
The 9me when the metasoma9c processes developed is s9ll debated. Different authors aQribute such processes to the last subduc9on during the Apennines orogenesis further authors hypothised Hercynian or older event. Isotopic data and the strong crustal signature of mafic magmas indicate the Appennines event more probable (Peccerillo & Dona9, 2003).
2.4. Campiglia MariDma area
Campiglia Mariima area is located in the Southern Tuscany at the centre, both spa9ally and temporally of the TMP. In this area forma9ons belonging to the Ligurian, Sub-‐Ligurian and Tuscan Domains, as well as Pliocenic magma9c rocks crop out. Spa9ally associated to the magma9c rocks are present different skarns and ore deposits (Fig. 6).
2.4.1. Structural seDng
The Campiglia Mariima area is characterized by a N-‐S trending horst bounded by high-‐ angle extensional faults and strike-‐slip faults. In this area widely the carbona9c forma9ons of Tuscan Nappe (Early Jurassic – Early Cretaceous) crop out bordered by forma9ons belonging to the Ligurian and Sub-‐Ligurian Domains, to the west and by clayey and turbidi9c successions of the Tuscan Nappe (Cretaceous -‐ late Oligocene) to the east (Fig. 6).
Fig. 6: SchemaLc geological map of the Campiglia MapariXma area. Stars indicate the main ore bodies (modified aVer Da Mommio et al., 2010).
In the Campiglia Mariima area were recognized two deforma9on phases, a first strike-‐ slip phase (D1) followed by a extensional phase (D2) (Acocella et al., 2000).
Along the western border of the Campiglia Mariima horst the D1 phase is characterized by N-‐S right-‐lateral strike-‐slip fault system due to simple shearing. The same kinema9cs has also affected the eastern border characterized by a NW-‐SE system of right-‐lateral faults.
These structures are here interpreted as P shear fractures of the main N-‐S systems of the western border.
The same areas on both borders were reac9vated during the D2 event as normal faults (Acocella et al., 2000). The D2 event also produced the bedding observed in the western border near the Botro ai Marmi monzogranite outcrop.
The wester border connects the deeper forma9ons of the Tuscan Nappe (Early Jurassic – Early Cretaceous) with the forma9ons of the overlying Ligurian and sub-‐Ligurian Domains while the Eastern border is characterize by the connec9on with the shallower forma9ons of the Tuscan Nappe (Cretaceous-‐Eocene). In both cases a ver9cal displacement of several thousand meters was es9mated (Acocella et al., 2000).
2.4.2. Magma=c rocks
The magma9c rocks of Campiglia Mariima show high variability (from intrusive to effusive and from acid to mafic) but a thorough descrip9on is s9ll lacking.
Botro ai Marmi pluton
The first magma9c event in the Campiglia Mariima area was the emplacement of a monzogranite pluton that crop out near the Botro ai Marmi valley with a K/Ar age of 5.7±0.16 Ma (Borsi et al., 1967). The Botro ai Marmi pluton emplaced in Rhae9an plauorm carbonates (Calcare Re9co Fm., Tuscan Nappe) and the morphology of the pluton roof is N-‐S elongated as indicated by explora9on wells (Stella, 1955; internal mining report) and geophysical data (Aquater, 1994). The pluton produced a N-‐S elongated contact aureole in the carbonate host rock forma9ons of the Tuscan Nappe (Calcare Re9co and Calcare Massiccio, Upper Triassic – Lower Jurassic) with an extension of about 5 km length, 1.5 km width and 300 m thickness (Rodolico, 1931; Giannini, 1955). The folia9on forms a NE-‐SW to N-‐S trending an9formal structure that culminates at Botro ai Marmi valley. Also the strata in the carbona9c rocks systema9cally plunge outward with respect to the main axial folia9on an9cline. Secondary an9cline and syncline folia9on in the marble were observed. The shape of the contact aureole is interpreted as another evidence of N-‐S elonga9on of the buried plutonic body (Acocella et al., 2000; Rossei et al., 2000).
The primary paragenesis of Botro ai Marmi monzogranite consist of quartz, K-‐feldspar, plagioclase, bio9te with accessory minerals 9tanite, apa9te, zircon and, tourmaline. However, such assemblages are rarely preserved (Rodolico, 1945; Barberi et al., 1967) due to an intense hydrothermal altera9on. The hydrothermal altera9on produced a rock with very high K2O (up to 10 wt%) and low Ca, Fe and S. Mineralogically, the K-‐altera9on is tes9fied by
secondary K-‐feldspar aler plagioclase while phlogopite replaced bio9te (LaQanzi et al., 2001). The contact with the host-‐rock is characterized by metasoma9c rocks (Barberi et al., 1967).
Campiglia MariDma porphyri=c rocks
The Campiglia Mariima porphyri9c rocks crop out discon9nuously for about 8 km between Campiglia Mariima and Castagneto Carducci (Giannini, 1955; Barberi et al., 1967; Fig. 6).
The Campiglia Mariima porphyri9c rocks are s9ll poorly studied and different authors describe 2 or 3 different types. In this frame of this study we tried to clarify some field, petrographic, chemical and isotopic features (chapters 6 and 7).
Mafic porphyry
The mafic porphyry is also known with the name of “porfido augi9co” (Rodolico, 1931; Giannini, 1955; Bertolani, 1958), “porfido augi9co-‐quarzifero” (Stella, 1955), “porfido monzoni9co femico” (Barberi et al., 1967) and/or “porfido verde” (miners; Corsini et al., 1980). This rock is strictly spa9ally associated to the skarn bodies exploited in the Temperino mine (Barberi et al., 1967; Corsini et al., 1980). The northern extension of this porphyry was encountered during drilling at depth of -‐418 m below sea level (drillhole 4, Soc. Monteca9ni, internal mining report).
The mafic porphyry is a porphyry9c rock with phenocrysts of plagioclase (with An 42 core and An 30-‐34 rim), clinopyroxene and bio9te and abundant xenocrysts of sanidine (also up to 5 cm) and quartz in a fine-‐grained groundmass of pyroxene, plagioclase and sanidine. On the basis of petrographical and mineralogical data it was proposed an affinity with the Monte Amiata la9tes (Barberi et al., 1967).
Felsic porphyri9c dykes
The felsic porphyri9c dykes are also know with the name of “porfido grani9co” (Rodolico, 1931; Giannini, 1955; Bertolani, 1958), “porfido quarzifero” (Stella, 1955), “porfido quarzomonzoni9co” (Barberi et al., 1967), “porfido alcalino-‐potassico” (Barberi et al., 1967) and/or “porfido giallo” (miners; Corsini et al., 1980). The felsic porphyries form two different dykes from Valle del Temperino to Valle di Santa Maria. Barberi et al., (1967) dis9nguished two chemical types the “porfido alcalino-‐potassico” cropping out in the southern area and the “porfido quarzomonzoni9co” occurring in the central and northern area. Recently,
another dyke was discovered about two kilometers east of the Temperino mine near Termine Rosso and it is about 1 km in length with a maximum thickness of 30 m (Cerrina Feroni, 2007).
The felsic dykes are characterized by phenocrysts of K-‐feldspar, plagioclase (An 30-‐38), quartz, bio9te and cordierite with mafic inclusions. Quartz and K-‐feldspar occur also in the groundmass. The primary paragenesis has been strongly obliterated by late hydrothermal processes that have produced an intense K-‐altera9on with sericite, “chlorite” and adularia aler plagioclase, cordierite and mafic phases. In some cases, an epidosite zone is usually present at the contact with the skarn (e.g., Loi, 1900; Corsini et al., 1980). Few hydrothermal breccia bodies were observed spa9ally associated to the western dyke (Cava Bianca, internal road limestone quarry near Rocca San Silvestro, Benvenu9 et al., 2004).
The age of 4.30 ± 0.13 Ma (whole rock K-‐Ar da9ng) was determined by Borsi et al., (1967) on one sample collected near the entrance of the Temperino mine (sample C16 of Barberi et al., 1967). This sample shows high K2O content (10.48 wt%) and for this reason the measured
age was considered the lower limit for the metasoma9sm (Barberi et al., 1967). San Vincenzo rhyolites
The San Vincenzo rhyolites cover an area of about 10 km2 from Valle delle Rozze to the
sud, to Torre di Donora9co to the north and they are the most studied magma9c rocks of the Campiglia Mariima area. The San Vincenzo rhyolites are lavas extruded onto Ligurian Domain rocks (Feldstein et al., 1994; Fig. 6).
The rhyolites are porphyri9c rocks with phenocrysts of quartz, alkali feldspar, plagioclase and bio9te with lesser amount of cordierite. The groundmass phases include plagioclase, bio9te with accessory minerals apa9te, monazite, zircon, ilmenite, and epidote. Some samples show mafic inclusion (Feldstein et al., 1994).
Several authors described two different groups characterized by different mineralogical, chemical and isotopic composi9on (Giraud et al., 1986; Ferrara et al., 1989; Pinarelli et al., 1989; Feldstein et al., 1994). Perugini & Poli, (2003) summarized the characteris9cs of the two groups with the name of NMG (not mixed group) and MG (mixed group) and show that these groups crop out in NNE and SSW zones, respec9vely. The difference between the two groups are ascribed to the magma9c history with the interac9on between a mantle-‐derived melt (similar to the K-‐andesite of Capraia Island) with a felsic anatec9c magma. The anactec9c melt is similar to the product of par9al mel9ng (40%) at 0.4-‐0.6 GPa of a Paleozoic garnet micaschist. The NMG represent the anatec9c end-‐member while the MG is the product of the interac9on between the two melts.
Mafic magma batches supplied the magma chamber filled with pure anatec9c melt. During this period a zoned magma chamber developed with an upper zone of felsic anatec9c magma and a lower with the mixing of the anatec9c and mantle-‐derived melts. The erup9ons triggered by mafic batches produced first the emplacement of the NMG group in the NNE part followed by the MG group in the SSE part (Perugini & Poli, 2003).
The age determina9on of San Vincenzo rhyolites is the topic of several works that used different analy9cal methods as K/Ar on bio9te (Borsi et al., 1967), fission track on glass (Bigazzi & Ferrara, 1971; Arias et al., 1981), and Rb/Sr on bio9te (Ferrara et al., 1977). The age of 4.38 ± 0.04 Ma was determined with 40Ar/39Ar geochronology on alkali feldspar
(Feldstein et al., 1994).
2.4.3. Metasoma=c bodies and ore deposits
Campiglia Mariima area is characterized by different typologies of metasoma9c rocks and ore bodies. These rocks can be grouped in three units: Campiglia Mariima Fe-‐Cu-‐Zn-‐ Pb(-‐Ag) skarn deposits, Botro ai Marmi metasoma9c rocks, Monte Valerio Sn-‐W-‐As ores (Fig. 6).
Campiglia MariDma Fe-‐Cu-‐Zn-‐Pb(-‐Ag) skarn bodies
Campiglia Mariima skarn bodies crop out over an area of about 12 km2 (Fig. 6). All skarn
bodies are hosted in white marble derived from the thermometamorphism of Calcare Massiccio Fm. (Tuscan Nappe) due to Botro ai Marmi pluton emplacement (e.g., Rodolico, 1931; Acocella et al., 2000). The most common occurrences are represented by Zn-‐Pb(-‐Ag) skarn bodies. In the southern part, two peculiar Cu-‐Zn-‐Pb(-‐Ag) skarn bodies crop out (Earle and Le Marchand), represen9ng the largest ores in the area, exploited in the past by the Temperino mine. The Campiglia Mariima Fe-‐Cu-‐Zn-‐Pb(-‐Ag) skarn consists essen9ally of clinopyroxene (hedenbergite and minor johannsenite) and ilvaite with very minor garnet (Corsini et al., 1980). Mn-‐pyroxenoids are rela9vely scarce (Capitani et al., 2003). Ore mineral assemblages are dominated by sphalerite, galena, chalcopyrite, pyrrho9te, pyrite and magne9te and were ac9vely exploited for Cu, Pb, Zn, and Ag un9l 1979. Campiglia Mariima skarn deposit has been considered as a classical example of exoskarn (e.g., Dill, 2010) in which a “normal” magma9c-‐hydrothermal sequence of events were described (e.g., Rodolico, 1931; Corsini et al., 1980; Fig. 7) similar to many skarn deposits in the world (for a review see Meinert et al., 2005).
Fig. 7: SchemaLc cross-‐secLon of the Temperino mine (modified aVer Corsini et al., 1980) Botro ai Marmi metasoma=c rocks
The Botro ai Marmi metasoma9c rocks occurs about one kilometer west of the Temperino mine in the contact area between Botro ai Marmi pluton and Rhae9an carbonates (Calcare Re9co Fm., Tuscan Nappe). Furthermore, these rocks were crossed by several drillholes also in the southern area always close to the contact with the pluton. Endoskarn veins crosscut the pluton and they are connected with largest masses of exoskarn (up to 8-‐10 meters of thickness; Barberi et al., 1967). The main primary phases are diopside, scapolite, vesuvianite, garnet, wollastonite, and tremolite associated to sulfides (e.g., galena, sphalerite, pyrite, arsenopyrite, bismuthinite), tungstates (scheelite) and oxides (e.g., cassiterite) (Biagioni et al., 2013 and references therein).
Monte Valerio Sn-‐W-‐As ores
The Monte Valerio ore deposit contains cassiterite, pyrite, scheelite, arsenopyrite and bismuthinite, and it is part of a Sn-‐W-‐As-‐Bi belt (Monte Valerio-‐Santa Caterina-‐Campo alle Buche) running along the western side of the buried Botro ai Marmi pluton. In 1876 the mining engineer Fréderique Blanchard discovered a high grade 9n deposit that was exploited for few years only due to its small overall size. The oxidized ore discovered by Blanchard was just the near surface, expression of a large, low-‐grade deposit (∼0.4 wt% of Sn) and it was ac9vely exploited un9l 1946. Several arseniates were also discovered within the oxidized ore por9ons (Dini & Senesi, 2013 and references therein).
