Evolution of a pluton-porphyry-skarn system: the Temperino-Lanzi mine (Campiglia Marittima, Tuscany)

The Campiglia Marittima Fe-Cu-Zn-Pb(-Ag) skarn deposit is of small size (∼ 50 kt of base metals) and medium/low-grade (1.4% Cu; 3.8% Zn; 2.0% Pb) with modest economic interest but its geological characteristics (e.g., spatial association with magmatic rocks, textural features of primary silicate minerals, ore bodies shape, etc) make it an ideal site to study skarn- and ore-forming processes. The present PhD thesis contributes to the debate on processes of skarn formation providing detailed field data integrated with petrographic, mineralogical and geochemical-isotopic data of the Campiglia Marittima magmatic-hydrothermal system. This locality offers also the opportunity to study the tridimensional shape of the geological bodies, thanks to past underground mining activities (during almost three millennia of ore exploitation), with additional data derived from about 25 km of drillholes. The results of this PhD work led to a deep review of the classical Campiglia Marittima exoskarn model and suggest an alternative holistic model for the development of skarn and ore bodies in the regional-local tectono-magmatic setting. The magmatic-hydrothermal and ore temporal sequence, together with a unifying tectonic-magmatic-metasomatic model proposed for Campiglia Marittima area can be used elsewhere as a guide in defining possible targets for ore and geothermal exploration. In addition to the scientific purposes, the results of this thesis have been and will be made availble also for tourists and laymen with no significant geological background by means of specific publications, conferences and mineralogical exhibitions, in the framework of a fruitful cooperation between the Dipartimento di Scienze della Terra (University of Pisa), the Istituto di Geoscienze e Georisorse of Pisa (CNR) and the Parchi Val di Cornia S.p.A., that manages the Parco Archeominerario di San Silvestro

Reverse telescoping in a distal skarn system (Campiglia Marittima, Italy)

The Campiglia Marittima Fe-Cu-Zn-Pb(-Ag) skarn deposit has long been regarded as a reference example of an exoskarn showing a symmetric outward mineralogical zoning of both skarn and ore minerals with respect to an axial mafic porphyry dike. Detailed field and underground mapping, along with three-dimensional reconstruction of the geometries of skarn and magmatic bodies, integrated with new petrographic, mineralogical and geochemical data, argue against this model. The shapes of the skarn bodies and the growth versors of skarn minerals in particular, are ascribed to the focusing of metasomatic fluids in sigmoid-shaped volumes of fractured host marble. After skarn formation, a mafic magma was emplaced, forming dikelets and filling residual pockets in the skarn. Field evidence and geochemical data show that the "hot" mafic magma interacted with the previously formed Zn-Pb(-Ag) skarn, triggering textural reworking and chemical redistribution of Zn-Pb sulfides as well as contributing to a late Fe-Cu mineralization. Campiglia Marittima skarn-ore system behaved at odd: a telescoping process is recorded, yet in a reverse way

Timescale of a magmatic-hydrothermal system revealed by 40Ar-39Ar geochronology: the Mio-Pliocene Campiglia Marittima system (Tuscany, Italy)

Petrology and timing of magmatic-hydrothermal systems and the linkage between plutonic and volcanic domains are central topics in geosciences, because of broad implications for natural hazards and exploitation of natural resources. We investigated by the 40Ar-39Ar method the timescale of a well-characterized natural example, the Mio-Pliocene Campiglia Marittima magmatic-hydrothermal system (Tuscany, Italy). 40Ar-39Ar data from pristine and homogeneous trioctahedral micas and sanidine from the plutonic-hydrothermal-subvolcanic-volcanic sequence (from the Botro ai Marmi Granite to the San Vincenzo Rhyolite) record crystallization ages and define a temporal sequence lasting 973 ± 43 ka, starting from 5.409 ± 0.043 Ma. K-feldspar from mafic and felsic porphyries, unlike micas, are affected by submillimetre, micropore laden, alteration domains consisting of secondary K-feldspar and albite, and yielded staircase-shaped age spectra, compatible with a ternary mixing. Results document that the San Vincenzo Rhyolite consists of two diachronous batches, the first emplaced at 5.0024 ± 0.0062 Ma, closely following emplacement of mafic porphyries, the second at 4.4359 ± 0.0045 Ma. Bulk of hydrothermal deposits, consisting of skarns and associated Zn-Pb(-Ag) mineralization predating Fe-Cu ore, formed within the first ~ 400-ka lifetime of the whole sequence and was closely followed by the first eruption which should have run out most of the ore-forming potential of the system

Time-space focused intrusion of genetically unrelated arc magmas in the early Paleozoic Ross-Delamerian Orogen (Morozumi Range, Antarctica)

The growth of continental crust in accretionary orogenic belts takes place through repeated cycles of subduction– accretion of rock units fromcontinental and oceanic magmatic arcs, supra-subduction zone backarcs and forearcs loaded with continent-derived materials. An ancient example relevant to magmatic arc accretion models is represented by the remnants of the Cambrian–Ordovician Ross Orogen in the Morozumi Range, Victoria Land (Antarctica). There, late Neoproterozoic phyllites host an intrusive complex which preserves a remarkably uncommon record of genetically unrelated magma pulses emplaced under a variable stress regime in a short time span: (1) a dominant K-feldspar–phyric granite, (2) fine-grained dioritic stocks and dykes, (3) a peraluminous granite; and (4) a tonalitic–granodioritic dyke swarm. Laserprobe U–Pb zircon dates cluster at late Cambrian times for all these units, yet they carry differential cargoes of relict cores. Unique geochemical– isotopic signatures for both the less evolved magmas (diorite and dyke tonalite) and the most acidic ones (granite and peraluminous granite) indicate that each one of them originated from distinct sources at depth. Additionally, field relationships and chemical evolutionary trends testify for a variety of shallow level open-system processes, such as magma mingling/mixing between diorite and main granite magmas, as well as progressive incorporation of the host schists by the dyke tonalite magma. In summary, crustal growth in the Morozumi intrusive complex was contributed by fresh mantle magma issuing from the metasomatised mantle wedge, while the production of othermelts did recycle different crustal portions/layers: the main granite derived fromGrenville-age granulitic lower crust; the peraluminous granite from late Proterozoic upper crust, and the tonalite magmas derived from subduction erosion-enriched subarc mantle and evolved by ingestion of local metasedimentary rocks. Overall, the Morozumi intrusive complex yields evidence for emplacement in the same site at the same time of magmas issuing fromdifferent sources that are usually found at a different depth in the arc lithospheric section. A likely scenario to activate this specific mechanism of melt production is a subduction zone affected by subduction erosion

Intestinal microbiota sustains inflammation and autoimmunity induced by hypomorphic RAG defects

Omenn syndrome (OS) is caused by hypomorphic Rag mutations and characterized by a profound immunodeficiency associated with autoimmune-like manifestations. Both in humans and mice, OS is mediated by oligoclonal activated T and B cells. The role of microbial signals in disease pathogenesis is debated. Here, we show that Rag2R229Q knock-in mice developed an inflammatory bowel disease affecting both the small bowel and colon. Lymphocytes were sufficient for disease induction, as intestinal CD4 T cells with a Th1/Th17 phenotype reproduced the pathological picture when transplanted into immunocompromised hosts. Moreover, oral tolerance was impaired in Rag2R229Q mice, and transfer of wild-type (WT) regulatory T cells ameliorated bowel inflammation. Mucosal immunoglobulin A (IgA) deficiency in the gut resulted in enhanced absorption of microbial products and altered composition of commensal communities. The Rag2R229Q microbiota further contributed to the immunopathology because its transplant into WT recipients promoted Th1/Th17 immune response. Consistently, long-term dosing of broad-spectrum antibiotics (ABXs) in Rag2R229Q mice ameliorated intestinal and systemic autoimmunity by diminishing the frequency of mucosal and circulating gut-tropic CCR9+ Th1 and Th17 T cells. Remarkably, serum hyper-IgE, a hallmark of the disease, was also normalized by ABX treatment. These results indicate that intestinal microbes may play a critical role in the distinctive immune dysregulation of OS

Dicchi e skarn di Campiglia Marittima: assetto geometrico, processi geochimici e cronologia relativa

La formazione degli skarn e le loro relazioni con rocce magmatiche rappresentano un argomento di primario interesse geologico in quanto a queste rocce sono spesso associati i principali giacimenti minerari per l’estrazione di Cu, Fe, Pb, Zn, Ag, Sn e Mo. In questo quadro, il presente lavoro di tesi ha lo scopo di contribuire alla conoscenza del chimismo e dei processi di messa in posto delle rocce magmatiche di Campiglia Marittima e degli skarn associati a queste manifestazioni. L’area oggetto di studio è situata nella parte occidentale della regione delle Colline Metallifere (Toscana meridionale) nei pressi di Campiglia Marittima. In questa zona affiorano, oltre a un plutone felsico, dicchi ignei porfirici associati a skarn e mineralizzazioni a solfuri, coltivate a partire dall’epoca etrusca e, in maniera più o meno continua, fino al 1976 per l’estrazione di Cu, Fe, Pb, Zn e Ag. L’assetto geometrico e strutturale dei corpi ignei e di skarn è estremamente variabile nello spazio, per cui la ricostruzione si è basata su un rilevamento geologico di dettaglio sia in superficie che in alcuni dei livelli ancora accessibili del complesso minerario del Temperino. Inoltre, i dati del rilevamento sono stati integrati con dati cartografici di superficie, con dati planimetrico-cartografici di sottosuolo e con log di perforazioni provenienti da archivi geologico-minerari. E’ stato così possibile ricostruire un modello “tridimensionale” dei corpi geologici investigati, che tenesse conto anche delle variazioni geometriche di questi corpi in profondità. In parallelo alla raccolta di questi dati geologici, sono state effettuate analisi petrografiche (microscopia ottica e SEM-EDS), mineralogiche (SEM-EDS e XRD) e geochimiche-isotopiche (XRF, ICP-MS e TIMS). Questo ulteriore set di dati ha fornito vincoli fondamentali per la comprensione del contributo e dell’origine dei fluidi metasomatizzanti di origine profonda e delle relazioni geochimiche tra composizione dei magmi, formazione degli skarn e alterazione idrotermale delle rocce ignee. L’integrazione dei dati geometrico-strutturali, geochimici e di cronologia relativa dei corpi ignei e degli skarn di Campiglia Marittima ha permesso di risolvere le relazioni esistenti fra questi oggetti geologici, portando alla formulazione di un nuovo modello geometrico-temporale-geochimico

Lateral extrusion of a thermally weakened pluton overburden (Campiglia Marittima, Tuscany)

The ascent and emplacement of magmas in the upper crust modify the local pre-existing thermal and rheological settings. Such changes have important effects in producing anomalous structures, mass extrusion, rock fracturing, and in some conditions, hydrothermal mineralizations. In the Campiglia Marittima area, detailed field mapping led to the reconstruction of a local deformation history that overlaps, chronologically and spatially, with regional extension. This local deformation was triggered at the Mioceneâ\u80\u93Pliocene boundary by the intrusion of a monzogranitic pluton beneath a carbonate sedimentary sequence. The emplacement of the pluton produced a perturbation in the rheological behaviour of the carbonate host rocks, producing transient ductile conditions in the very shallow crust. The carbonate rocks were thermally weakened and flowed laterally, accumulating downslope of the pluton roof, mainly toward the east. As the thermal anomaly was decaying, the brittleâ\u80\u93ductile boundary moved progressively back towards the pluton, and large tension gash-shaped volumes of fractured marble were generated. These fractured volumes were exploited by rising hydrothermal fluids generating sigmoidal skarn bodies and ore shoots. This work presents the Campiglia Marittima case study as a prime example of structural interference between regional extensional structures and local, lateral mass extrusion in a transient ductile rheological regime triggered by pluton emplacement

Thallium-rich pyrite ores from the Apuan Alps, Tuscany, Italy:constraints for their origin and environmental concerns

The southern sector of the Apuan Alps (AA) massif, Tuscany, Italy, is characterized by the occurrence of a series of baryte–pyrite–iron oxide orebodies whose Tl-rich nature was recognized only recently. The geochemistry of the pyrite ore was investigated through inductively coupled plasma mass spectrometry. In addition, lead isotope data for selected pyrite ores from AA were collected. Pyrite ores are characterized by a complex geochemistry, with high concentrations of Tl (up to 1100 μg/g) coupled with high As and Sb contents; the Co/Ni ratio is always <1. Geochemical data of pyrite and marcasite ore samples from other mining districts of Tuscany have been collected in order to compare them with those from the AA. These samples usually have very low Tl content (less than 2 μg/g) and high to very high Co/Ni and As/Sb ratios. Only some samples from the Sb–Hg ore deposits showed very high Tl concentrations (up to ~3900 μg/g). Another difference is related to the lead isotope composition, with pyrite ores from AA markedly less radiogenic than those from the other deposits from Tuscany. Geochemical data of pyrite ores from AA give new insights on the genesis of the baryte–pyrite–iron oxide orebodies, relating their formation to low-temperature hydrothermal systems active during early Paleozoic; in addition, these data play a fundamental role in assessing the environmental impact of these deposits

Inside the mine: interactions between hydrosphere, atmosphere, biosphere and the thallium-rich pyrite ores from southern Apuan Alps

Pyrite is the most common sulfide mineral of the Earth’s crust and the main responsible for the production of acid rock drainage (ARD) and acid mine drainage (AMD). Where the geologic, climatic and biologic conditions are those most favourable to the oxidation of pyrite (i.e. circulation of oxygenated water through fine-grained pyrite ores in presence of iron-oxidizers bacteria), the production of acidic waters can pose severe environmental issues. This is the case of the southern Apuan Alps (one of the rainiest area of Italy), where several types of polymetallic sulfide/oxide ore deposits, hosted within highly to moderately permeable metamorphic rocks, have been mined since ancient times and up to the end of the last century. One of the most important of these ore deposits is represented by a series of baryte-pyrite-iron oxide orebodies aligned along a ~10 km SW-NE discontinuous mineralized belt located between Valdicastello Carducci (Pietrasanta, LU) and Fornovolasco (Fabbriche di Vergemoli, LU). Pyrite ores mainly occur as microcrystalline lensoidal masses, often in association with baryte, within the quartz-muscovite-chlorite phyllites of the Paleozoic basement or at the contact between the phyllites and the overlying Triassic dolostones. Only recently it was recognized that the pyrite ores still occurring in large amounts in this mining area, and widely exposed in the abandoned tunnels, is strongly enriched in thallium (typically 200-300 mg/kg and up to 1100 mg/kg). In some specific localities (i.e. Monte Arsiccio mine, Sant’Anna di Stazzema, LU) Tl also occurs as macroscopic Tl-Pb-Sb-As-Hg sulphosalts, emphasizing the exceptional nature of these mineralizations. Thallium is a relatively rare but highly toxic element that is readily transferred, along with other toxic or potentially toxic elements (particularly As, Sb, Pb, Hg, Cd, Zn, etc.), from pyrite ores to the aqueous phase. Indeed the internal waters of these mines may reach extreme concentrations of Tl (typically 500-1000 μg/l and up to 9000 μg/l). The stability of the main Tl species – the Tl+ ion – dissolved in the AMD-contaminated waters over extended intervals of pH and Eh conditions, enhances the dispersion of this element into the environment; indeed it is neither easily precipitated as an insoluble solid phase nor easily adsorbed onto jarosite/ferrihydrite/schwertmannite/goethite precipitating from Fe- and sulphate-rich waters