The Age of Mineral Deposits in the Permian Volcanites of Trentino-Alto Adige (Northern Italy) Francesco Bakos, Aldo Brondi, and Giuliano Perna Introduction The Permian volcanites which constitute the porphyric platform of the Adige Valley*, about 4000 km2 wide, are cut by several hydrothermal veins**. These mineralizations are known from a minerogenetic and typo-logic standpoint through numerous and important studies carried out by several authors***. Only for some of these deposits the age has been ascertained. Chronologic attribution for many others is stili lacking. The better knowledge finally acquired on the stratigraphy of the central part of the volcanic platform, where the most important mineral concentrations occur, allowed to obtain new data on the spatial and chro-nological relationship betvveen volcanites and the included mineral deposits. Stratigraphy The Permian volcanites of Trentino-Alto Adige overlie directly the metamorphic basement. Only locally a thin conglomeratic layer, made up mostly of metamorphic debris, separates the above mentioned formations. In the northern part the volcanites come in oontact with the Ivigna Paleozoic granite. In the southern part on the contrary a similar direct contact with the contemporaneous Cima d'Asta granite is lacking. The volcanites may be subdivided in three main groups: a lower group (about 1000 m thick), very heterogeneous and mostly constituted by latite--andesitic and latitic lavas and tuffs, by rhyodacitic ignimbrites and lavas and by conglomerates, volcanic sandstones and siltstones (TQ in Fig. 1); a middle group, with an average thickness ranging from 500 to 900 m of wery large and homogeneous layers of rhyodacitic ignimbrites and of local and irregular intercalations of volcanic sandstones and siltstones (Q4—Qt in Fig. 1); an upper group, more than 1000 m thick, made of very * The series of Permian volcanites of this region is widely illustrated in the legend of Fig. 1, to which M. N a r d i n contributed. ** It exists also, as it will appear later, a sedimentary mineral deposit in the "Scisti di Tregiovo" (Tregiovo Shales). *** See in bibliography the most important works. Explanation of Figure 1 8—9 Fifth group ol mineral deposits (type 2) 7 Ladinian dikes Bell. Bellerophon Formation AvG Val Gardena sandstones with local conglomeratic levels containing porphyry debris at their base Rl Rhyolitic ignimbrites brlck-red in colour and with local vitrophyres at their base (V) T2 Rhyolltlc tuffaceous ignimbrites greenish-grey in colour, sometimes very compact in the basal or central portion and with sporadic ignimbritic debris of the R2 facies. Local intensive reworking traces at the top of the levels, sometimes with sandy or clayey beds M Tregiovo shales, formation made of shales, partially calcareous, with frequent lacustrine carbonaceous facies mostly at the base of T2. They occur sometimes at the top of T3 and T4 or constitute local interbedding among the basal layers of some rhyolitic layers . 6 Fourth group of mineral deposits (type 1) K2 Rhyolitic ignimbrites violet-red in colour with euhedral phenocrystals. They are mostly whitened because of hydrothermal-pneumatolitic autometamorphism. Sub-volcanic facies are frequent. Vitrophyric facies at their base (V) T, Tuffaceous rhyolitic ignimbrites. Mostly ignimbritic at their base with fragmental or spheroldic bodies of the same nature as the matrix. They are tuffaceous in the middle parts, and sandy-conglomeratic with Intensive reworking and with lacustrine beds in the upper parts R3D Rhyolitic domes with great pink feldspars with resorption borders. They are genetically correlated with the rhyolitic eomplex R3 R3L Rhyolitic lavas R3 R3 Rhyolitic ignimbrites violet-pink in colour, highly whitened because of hydro- thermal-pneumatolitic autometamorphism. Vitrophyric facies at their base (V) T4 Volcanic breccias, and conglomerates, sandstones and siltstones derived from erosion and reworking of underlying Q3, Q2, and chiefly Qt ignimbrites. At the basal part of the complex tuffaceous-conglomeratic levels frequently occur 5 Erosion 4 Third group of mineral deposits (type 1) 3 Volcano-tectonic rocks Q1 Quartzlatitic and rhyodacitic ignimbrites dark-grey in colour with violescent or reddish shading Ts Conglomeratic tuffs with both lava and tuff inclusions derived from the basal complex TQ. This level represents a contemporaneous phase of the basal volcanic system with the effusions of the