Per. Mineral. (2003), 72, SPECIAL ISSUE: Miocene to Recent... , 41-52 http://go.to/permin An InternationalJournal of =; PERIODICO di MINERALOGIA MINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY, established in 1930 ORE DEPOSITS, PETROLOGY, VOLCANOLOGY and applied topics on Environment, Arclweometrv and Cultural Heritage CHAPTER 2 Ore deposits, industrial minerals and geothermal resources ANDREA DINI* CNR, Istituto di Geoscienze e Georisorse, Via Moruzzi, 1, 56124, Pisa, Italy 2. 1 HISTORICAL PERSPECTIVE grew to become the great economic resource of Populonia, drawing increasingly on the rich Together with Sardinia, Tuscany is the main mineral deposits of the Island of Elba often mining region of Italy, where almost three mentioned in ancient texts (Diodorus Siculus, millennia of exploitation yielded significant apocryphal writings of Aristotle). productions of iron, pyrite, base metals, silver, After the fall of the Roman Empire, the ore antimony, mercury, gold as well as industrial deposits of Elba Island and «Colline minerals and super-heated steam (Fig. 1 ). In Metallifere» (Massa Marittima area) fell in addition to its economic relevance, the Tuscan total oblivion for centuries. It was only in metallogenic province remains of primary Middle Age (XI-XIV century) and Renaissance scientific importance due to the occurrence of time (XVI-XVIII century) that mining activity diverse hydrothermal deposits associated with flourished again in Tuscany, particularly in the volcano-sedimentary, intrusive, metamorphic Ag-Cu (-Fe) district of «Massa Metallorum» and geothermal environments of pre- Alpine (now Massa Marittima in Southern Tuscany), and Alpine ages (Lattanzi et al., 1994 and but also in the Fe district of Elba Island. During reference therein). the XIX century, exploration and exploitation There are few indirect archaeological of ore deposits in Tuscany took advantage by evidences indicating that exploitation of iron the production of the first geological maps and ores from Elba, Cu-Pb-Ag ores from genetic studies of mineralogists and geologists Temperino and Massa Marittima, and tin ores from Italian and European Universities. After from Monte Valerio was possibly the Unification of Italy all mines became a accomplished since the VIII-VII century B.C state property and were granted in concession until the Roman period. However, the to different mining companies, up to 1990's, archeometallurgical products and rare furnaces found along the coasts of the Elba Island and when the last pyrite mine in southern Tuscany (Cam piano) shut down. Tuscany (e.g. Populonia) indicate that · extensive reduction of iron and copper minerals Today, the mining industry in Tuscany is was accomplished in the Roman period (Ill facing the typical problems of most European century B.C.). Especially the iron industry regions, and extraction is currently limited to ornamental stones, building materials and a few industrial minerals such as raw ceramic * E-mail: [email protected] material. 42 A. DIN! 2.2 METALLOGENY past century, earlier scientists considered the Late-Alpine intrusions as the sources of heat The metallogeny of Tuscany is rather and metals (e.g. Lotti, 1929). More recently, complex, and several aspects still await a new epigenetic models have been proposed definite answer. (Marinelli, 1983; Dechomets, 1985), according According to Lattanzi et al. (1994), three main to which the intrusions acted as heat sources metallogenic epochs seem to be relatively well and promoted the circulation of hydrothermal established in Tuscany: (i) a Lower-Middle fluids, although the source(s) of the fluids Palaeozoic stage, leading to the formation of themselves and dissolved metals should be protores/preconcentrations of metals (e.g. the looked for elsewhere. Thus Marinelli (1983) Ag-Pb- Zn Bottino deposit and the Hg Levigliani suggested that Fe could derive from deposit in the Apuane Alps) strictly related to the metasomatic reactions taking place at the Ordovician calcalkaline magmatism; (ii) an peripheral portions of the intrusive bodies: Upper Palaeozoic -Triassic Fe (and Ba) event, chloride-rich metamorphic and/or connate possibly related to a pre-Tethyan aborted rift, that waters would have been enriched in Fe through is documented in various areas, such as Elba reaction with magmatic biotite. On the other Island, Southern Tuscany and Apuane Alps; (iii) hand, Dechomets ( 1985) proposes that an Alpine event, well documented both in hydrothermal fluids of dominant marine origin Apuane Alps and in Southern Tuscany (e.g. the scavenged Fe from host rocks. The authors epithermal Hg-Sb-Au deposits, the Cu-Pb-Zn favouring the second genetic model sulfide ore bodies), characterized by («syngenetic/hydrothermal-metamorphic») hydrothermal systems triggered by both regional acknowledge the importance of the Alpine metamorphism and magmatism. tectono-magmatic event in reworking the iron One of the most debated themes is the origin ores, but believe that, at least as protores, they of iron-bearing deposits occurring in Tuscany were formed in sedimentary and/or (barite-iron oxide-pyrite deposits of Apuane hydrothermal sedimentary environments of Alps, pyrite deposits of Southern Tuscany and Triassic and/or Palaeozoic age (Deschamps et the iron ores of Elba Island). Total production al., 1983; Tanelli and Lattanzi, 1983; Zuffardi, from the three districts may be estimated in the 1990). According to these authors, the Late­ order of 150 million tons ore: the Apuane Alpine extensional tectonics, metamorphism, deposits yielded about 0.5 million tons of magmatism and related hydrothermalism pyrite + Fe oxides, whereas more than 80 would be responsible for the more or less million tons of high-grade mineral concentrate remobilisation and metamorphism of the metal were obtained by exploitation of several pyrite preconcentrations. deposits in Southern Tuscany (Niccioleta, Gavorrano, Boccheggiano, etc.), and not less 2.3 THE FE DEPOSITS OF ELBA ISLAND than 60 million tons Fe ore have been extracted from Elba deposits from ancient times up to As shown in figure 1 and 2, the Fe deposits nowadays. A number of hypotheses have been of Elba Island are restricted to a relatively put forward in the last two centuries in order to narrow belt extending NS along the eastern explain the genesis of Tuscan Fe deposits. coast of the Island (see Tanelli et al., 2001 and They can be grouped in two basic genetic reference therein). The ore bodies, even at the models (Tanelli and Lattanzi, 1986): (i) scale of individual deposit, occur in variable «plutonistic epigenetic», and (ii) settings, from stratiform to pod-like or vein­ «syngenetic/hydrothermal-metamorphic». type, although the first appears to be dominant According to the first model, ore genesis is a (Zuffardi, 1990). Stratiform Fe bodies, either or direct consequence of the intrusion of the Late­ not associated with veins and/or irregular Alpine granitic plutons. In the first half of the masses, are «strata-bound», at least in the wider Ore deposits, industria/minerals and geothermal resources 43 S A Larderello field \ IEN B � \ ..- \ __ ). -- �- ..........- • 4.;. -t* \ "Cu-Pb-Zn-(Ag) : _. _. I -- "'\ '0 \ zone" ..- 1 � r:ilfnpigltg_ _. .tJ '-</)-:(> 11 Ca'mbia o \ -- l 1 D .,!_,1 1 � , 4 Niq:ioleta• , • 1 v-- \ _. Botro I ,... _....�- 1 �--1 \ "Hg 1 ai Marmi / zone" I _. _. \ • / li -- Q \ ,{, L/":J\:: . - • ·-- --·-.". 1 Torniella 1 \ �v� � � / ih Marina -- \-+_. / .A.1 : 1 Gavorrano 1 I "7\� ·' '*�� i}t t _. 1 l )( / ' 1 ( //�Monte _1 GROSSETO /\' i:f * A1Terranera --1- / \ Amiata • 1 / -�-···/ Elba I ( I \ / / f'1e Id .c4po Calamita � , N 1\ / / I\ *A / � / X \ "Fe oxide , r"N 1 / , zone" / *' \ **' \ * *' "Sb - Au \ zone" J11rm!ecn:r/rJ "pyrite zone" 0 30km LEGENDA Intrusive rocks of Tuscan Magmatic Province 0 Cu-Pb-Zn-(Ag) ore Volcanic rocks of Tuscan Magmatic Province * Sb-Au ore A Fe-oxides ore * Hg ore • Pyrite ore � Raw ceramic material Fig. I -Major deposits and mineral belts of Southern Tuscany (modified after Tanelli and Lattanzi, 1983). meaning of the word. In fact they are Hematite (± pyrite, limonite) ores from Rio predominantly hosted by Palaeozoic-Triassic Albano up to Rio Marina mining area are formations belonging to Tuscan Domain neither directly associated with intrusive bodies (Complex I, II and Ill; see Part Ill, Chap. 1). (plutons, dykes) nor with skarn bodies of 44 A. DIN! Geological setting of the Eastern part of the Island of Elba. modified from PERRIN ( 1974): - Yll: intrusive Eastern Elba Quartz monzonite. - Lower Tuscan Units: T0 = basement of the Ca- lamita Unit; T1 =carbonatic cover of the Calamita Unit; T2 = Ortano Unit; T3 =Unit of"Schists and Crystalline Limestones"; T4 = Rio Marina Unit. - Upper Tuscan Units: T5a and T5b = Limestone Units. Ligurian Units: S = interlayered serpentine; L1 - Ophiolites; L2 = Helminthoides bearing !lysch. - Iron Deposit: I a Ginevro; I b = Stagnone; I c = Sassi Neri; 2 = Calamita; 3a = Terra Nera; 3b = Ortano; 4 = Valle Giove; 5a Bacino: 5b = Vigneria; 6a = Zuccoletto; 6b = Rialbano; 6c = Monte Calendozio; 7a = Valle di Catone: 7b = Rossetto; 7c = Le Conche, 7d = Fornacelle. Fig. 2-Geological setting and location of Fe ore deposits of Elba Island (modified after Deschamps et al., 1983). presumable magmatic affiliation. However, Rio Marina is especially famous worldwide for mineralogical, textural and fluid inclusion its beautiful crystals of hematite (variety analyses of hematite+adularia assemblage from «oligisto» = glaze iron) and pyrite. Hematite Valle Giove stopes