The Granites of the Nantais
The Nantais stands apart from the other main regions of the Loire Valley in that there is no one defining rock here. The Central Vineyards not to mention the leading appellations of Touraine and Saumur all champion limestone, and regardless of all the spilite, quartz and phthanite complexities found in Anjou, this region is most famed for its schist. Here in the Nantais, however, many the interlocking geological jigsaw that is the Massif Armoricain gives the vignerons many different terroirs to work with, all of which bring something different to the table. Granite can bring structure, gabbro can bring acidity and energy, amphibolite can bring a light-footed vigour, each one creating wines of equal interest and value.
So where should any examination of the region’s geology and its impact on wine begin?
There is no right or wrong choice, but it seems to me that granite is the obvious place to start. It is granite that has given me some of the best experiences with Muscadet over the years, and while in many cases this was with relevant cru communal wines (which I will explore in more detail in my pages on the Muscadet Crus Communaux) it was also with any number of wines wearing the traditional Muscadet Sèvre et Maine sur lie appellation, such as Clos des Briords (more recently simplified to Briords) from Marc Ollivier (pictured) at Domaine de la Pépière. Granite has also provided some of the best examples of aged Muscadet I have encountered, with the L d’Or from Domaine Luneau-Papin (which comes from a mix of granite and gneiss terroirs, admittedly) drinking well at twenty or even thirty years of age.
So it is with granite we begin, but I will not focus on it exclusively, as its sister rock granodiorite also deserves consideration here. Other forms of igneous rock such as gabbro and rhyolite, however, I will leave for the next instalment of this guide.
Granite & Granodiorite
Granite is an igneous rock, which means it formed from the cooling of molten minerals, and it has not undergone any subsequent metamorphosis. Being more specific, it is a plutonic (or ‘intrusive’) rock; this rather unusual term tells us that the molten rock cooled and crystallised when still deep underground, as I have described and illustrated my introduction to the geology of this region. Plutonic rocks are distinct from volcanic (or ‘extrusive’) rocks, those formed when the molten rock cools after reaching the earth’s surface, after having escaped as lava. There are few examples volcanic igneous rocks in the Nantais though, the only significant example which springs to mind being rhyolite. You have to go to the other end of the Loire, to the vineyards of the Massif Central such as the Côte Roannaise and Côtes du Forez, to find broad expanses of volcanic rock, in the shape of basalt.
