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RESEARCH PROGRAM

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Keywords
STRUCTURAL GEOLOGY; ORE GEOLOGY; ENGINEERING GEOLOGY; SARDINIA

Deformation, hydrothermal circulation and minerogenesis in an evolving orogen : the Hercynian basement of central-southern Sardinia.

Università degli Studi di Siena
Abstract
In the nappe zone of the Sardinian segment of the south-European Hercynian chain up to now the lithostratigraphic and structural frame is very defined, where a polyphasic tectonic evolution has been recognized from collisional to extensiona phases. The metamorphic rocks moreover host important ore deposits, with not yet exploited gold mineralizations. To investigate in details remain still the P T t evolution and the role of tectonics in development of ore deposits, as the ssignificance of hydrothermal circulation and minerogenesis.
In order to overwhelm this gap, and therefore to link the data from the sardinian basement with those described from numerous authors in the European Hercynian chain, we need to integrate structural and stratigraphic geologic studies with the modern techniques of: three-dimensional restoration of deformed areas, isotopic analysis, microstucture analisys and investigations on fluid inclusions. That implies an accurate definition of the age of compressive and extensional phases in the various tectonic units units that constitute the "nappe zone" of the chain.
In Sardinia, studies about the relationships between structural geology and ore deposits development still do not exist. The areas that seem particularly important for the attainment of results, are those of the Sarrabus-Gerrei area, comprised between the Flumendosa river and the plateau of Quirra, where a section of the tectonic nappe stack is well exposed; in this area thick >>>

Principal Investigator
Luigi CARMIGNANI Università degli Studi di SIENA
Research Objectives
The present research program focus on the study of the Hercynian basement of Sardinia emerging, in detail in central-southern sardinia ("nappe zone"), where a tectonic nappe stack is recognized and documents the poliphasic evolution during the hercynian orogeny, with development of polyphase metamorphisms. This basement also hosts ore deposits, different for genesis, geometries and typology, and sometimes with important economic implications. The deepening of the up to now acquired data, illustrated in the following paragraph 2.2, is proposed to overwhelm the currently existing knowledge difference between this segment and the rest of the south-European Hercynian chain, in particular P, T, t paths investigations. The attainment of such goal will be pursued with typical methods of the structural geology, and of the ore geology. In order to attain it, the classic methods of geology (structural-geological mapping, cartography, reconstruction of the litostratigrafiche successions, recognization of ore bodies, etc.) will be paired with investigations based on new technologies (see paragraph 2.3) as isotopic analysis, radiometric dating, microfabric investigations and the applications computerized methods for the three-dimensional reconstruction of the rock bodies.
It is proposed to integrate structural geology and ore deposits investigations. Online with how much it is happening to world-wide level, where the relationships between deformative structures and >>>

Timescale
24 months
National and international background
Sardinia is a part of the south-European Hercynian chain, than extends from an "external zone" (SW Sardinia, Sulcis-Iglesiente), to a "nappe zone" (central and southern Sardinia), structured in tectonic units emplaced during the collisional phases, and an "axial zone" in the northern Sardinia (Anglona-Gallura) (Carmignani et al.. 1994, Carmignani et al. 2001b, with references). Barrovian type metamorphism is recognized, increasing from the external zone to that axial zone, linked with the collision of the Armorican microplate and the northern margin of the Gondwana during the lower Carboniferous. The correlation between the Hercynian metamorphic basement of Sardinia and of southern France has been evidenced for a long time (Arthaud 1970, Matte 1986, and bibliography), and generally is accepted from all the authors.
The study of the European Hercynian chain stongly developed around years ' 70 and ' 90, to continuation of the full affirmation of the plate tectonic theory and consequent abandonment of the completely ensialic interpretation of its formation. In particular in Sardinia, that years has coincided with a geologic, structural and stratigraphic effort, that it has supplied data for a homogenous interpretation of the tectonic evolution of the hercynian chain in the framework of the south-European hercynian chain (Carmignani et al. 2001a with bibliography, Matte 1986). In the last years this interest has taken new vigor, as new technologies allow the study of the >>>