In the Hercynian Canigo Massif exist a basic-acid volcanism interbeded between the azoic metasediments characteristics of lower Paleozoic subsident bassins. It define a low grade metamorphosed volcanic sequence of toleiitic-calc-alkaline affinity. The more basic toleiitic terms are located at the lower part of the metasedimentary sequence ("Canaveilles Group"), and they are constitute by meta-andesitic basalts and meta-andesitic terms that appear essentilly how flow-laves. Pyroclastic beds formed by meta-ignimbritic andesitic flow-laves and rhyodacitic meta-tuffs and rhyolitic meta-ash of calc-alkaline affinity are located at the top of metasedimentary sequence. A geochemical and petrologic polarity is show by the metavolcanic serie into the metasedimentary Canaveilles Croup. These volcanism is characterized by an important subductive component and geochemical anomalies ascribed to continental settings. It is relationed with the ouverture of a marginal subsident bassin or a continental back-arc bassin