Chaves is in the extreme north of Portugal, bounded on the north by Galicia (Spain), on the east by the municipalities of Vinhais and Valpaços, on the south by the municipality of Vila Pouca de Aguiar and on the west by the municipalities of Montalegre and Boticas.
Chaves is one of the six municipalities of the Alto Tâmega, situated in the district of Vila Real, strategically positioned in the northwest of the Iberian peninsula and accessed by important international highways.

The region is dominated by the Quaternary Chaves sedimentary basin, a graben aligned on a north-northeast to south-southwest orientation bounded by the Hercynian massif and metamorphic schistose formations.
Mixed with the schistose complex, there are bands of graphitic slates, mainly in the southern part of the urbanized area of Chaves and south-east of Faiões.
To the north, and into Galicia, the basin extends into the depression of the Verin Basin.
One of the oldest formations in the region, it dates back to the Ordovician period ( between 488.3±1.7 to 443.7±1.5 million years ago), is composed of schist and graywacke deposits.
During the Ordovician-Silurian geological periods quartzites and schists were formed, metamorphosed by Hercynian granitic intrusions, at the end of the Paleozoic.

The Alpine orogeny was the main cause of extensive tectonic activities and it was responsible for the formation of the hydrothermal field within the region.
The Chaves graben was formed by the relative motion of the block with different types of sediments being settled.
The most recent formations are a sedimentary series (lacustrine, alluvial, colluvial, detritic, etc.)
with variable thickness that had their origin during the Miocene.
Two main faults cross and influence the tectonic activities: the north-northeast by south-southeast Chaves-Verin Fault and a fault system crossing near Faiões and Santo Estêvão.
The first fault developed from late Hercynian tectonic episode occurring between 280 and 300 million years ago, that developed into an almost north-south direction into the lithosphere.
Intense neotectonic activity reactivated these old fractures, originating in a complex pattern of faults in the sedimentary basin.
Chaves is in the extreme north of Portugal, bounded on the north by Galicia (Spain), on the east by the municipalities of Vinhais and Valpaços, on the south by the municipality of Vila Pouca de Aguiar and on the west by the municipalities of Montalegre and Boticas. Chaves is one of the six municipalities of the Alto Tâmega, situated in the district of Vila Real, strategically positioned in the northwest of the Iberian peninsula and accessed by important international highways.
The region is dominated by the Quaternary Chaves sedimentary basin, a graben aligned on a north-northeast to south-southwest orientation bounded by the Hercynian massif and metamorphic schistose formations. Mixed with the schistose complex, there are bands of graphitic slates, mainly in the southern part of the urbanized area of Chaves and south-east of Faiões. To the north, and into Galicia, the basin extends into the depression of the Verin Basin. One of the oldest formations in the region, it dates back to the Ordovician period ( between 488.3±1.7 to 443.7±1.5 million years ago), is composed of schist and graywacke deposits. During the Ordovician-Silurian geological periods quartzites and schists were formed, metamorphosed by Hercynian granitic intrusions, at the end of the Paleozoic.
The Alpine orogeny was the main cause of extensive tectonic activities and it was responsible for the formation of the hydrothermal field within the region. The Chaves graben was formed by the relative motion of the block with different types of sediments being settled. The most recent formations are a sedimentary series (lacustrine, alluvial, colluvial, detritic, etc.) with variable thickness that had their origin during the Miocene. Two main faults cross and influence the tectonic activities: the north-northeast by south-southeast Chaves-Verin Fault and a fault system crossing near Faiões and Santo Estêvão. The first fault developed from late Hercynian tectonic episode occurring between 280 and 300 million years ago, that developed into an almost north-south direction into the lithosphere. Intense neotectonic activity reactivated these old fractures, originating in a complex pattern of faults in the sedimentary basin.
Chaves, Portugal