In recent years, several gold occurrences of possible economic interest have been discovered in the Paleozoic basement of SE Sardinia (Sb-W Gerrei district) where Au-bearing As-Sb-W and base metal ores are hosted in greenschist facies metamorphic rocks. Studies performed in selected areas of the district (Monte Ollasteddu, Baccu Locci, Brecca) evidenced a strong structural control for the gold mineralization, which is hosted in mesothermal quartz-sulfide veins, stockworks and lenses, associated to late-Hercynian brittle and brittle to ductile shear zones, extensional fractures and antiform folds. These structures developed in an extensional regime related to the collapse of the deca-kilometric Flumendosa Antiform, the most important regional tectonic feature of the area. In these areas, structural and mineralogical data indicate repeated mineralizing events, related to an evolving tectonic framework. At the district scale, a generalized paragenetic sequence is: 1) white qtz ± sch + aspy I + py, followed by 2) microcristalline qtz ± ank/cal ± aspy II ± Pb-Zn-Cu-Sb sulfides ± native Au. The gold occurrences from the Gerrei district may be classified as mesozonal-epizonal orogenic gold type: geological and structural data suggest the general framework of a single metallogenic event during the late-Hercynian orogenic phases. The timing of the As-Sb-W-Au mineralization (Late Carboniferous-Early Permian) and the overall metallogenic evolution of the Gerrei district may be compared with other areas along the Hercynian Chain of SW Europe, and, in particular, with the districts of French Central Massif.
Caratteri giacimentologici e controlli strutturali nelle mineralizzazioni idrotermali tardo-erciniche ad As-Sb-W-Au del basamento metamorfico paleozoico della Sardegna Sud-orientale
FUNEDDA, ANTONIO LUCA;NAITZA, STEFANO;
2005-01-01
Abstract
In recent years, several gold occurrences of possible economic interest have been discovered in the Paleozoic basement of SE Sardinia (Sb-W Gerrei district) where Au-bearing As-Sb-W and base metal ores are hosted in greenschist facies metamorphic rocks. Studies performed in selected areas of the district (Monte Ollasteddu, Baccu Locci, Brecca) evidenced a strong structural control for the gold mineralization, which is hosted in mesothermal quartz-sulfide veins, stockworks and lenses, associated to late-Hercynian brittle and brittle to ductile shear zones, extensional fractures and antiform folds. These structures developed in an extensional regime related to the collapse of the deca-kilometric Flumendosa Antiform, the most important regional tectonic feature of the area. In these areas, structural and mineralogical data indicate repeated mineralizing events, related to an evolving tectonic framework. At the district scale, a generalized paragenetic sequence is: 1) white qtz ± sch + aspy I + py, followed by 2) microcristalline qtz ± ank/cal ± aspy II ± Pb-Zn-Cu-Sb sulfides ± native Au. The gold occurrences from the Gerrei district may be classified as mesozonal-epizonal orogenic gold type: geological and structural data suggest the general framework of a single metallogenic event during the late-Hercynian orogenic phases. The timing of the As-Sb-W-Au mineralization (Late Carboniferous-Early Permian) and the overall metallogenic evolution of the Gerrei district may be compared with other areas along the Hercynian Chain of SW Europe, and, in particular, with the districts of French Central Massif.
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