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The 3D models in this section represent an ancient iron mining site near the locality of Ferriere (Piacenza) in the Northern Apennines (Italy).
The mines are called "Miniere di Canneto" and are nowadays witnessed by the remains of four entrance tunnels along the Grondana creek, three at the base, right beside the creek, and a forth one further up along the hill side.
The site was known since roman times and mining was developed during several periods until 1950. One period of major activity was in the second half of 15th century, when the nearby village was founded, bearing the suggestive name of "Ferriere", meaning "the site of iron mining".
The mining site is characterized by the presence of rocks called "ophiolites" because of their dark green color, from which magnetites (Fe²O³) and calcopirite (Cu²S + FeS²) minerals were extracted. Ophiolites dark color is typically indicative of the presence of minerals rich in iron (Fe) and other heavy elements that were formed in the depths of the oceans, where new oceanic crust is generated from the solidification of magna raising from the earth mantle.
In fact these rocks are the remains of an ancient ocean ("Piemont-Liguria" or "Alpine" ocean) that developed starting in Jurassic time (180 million years ago) when the former continent of Pangea broke apart and split into the Eurasian and African plates. This ocean reached its full expansion and then gradually closed between the end of Cretaceous and Tertiary times (70-20 million years ago). The fragments that were squeezed between the two converging plates of Eurasia and Africa-Adria became included in the present day Northern Apennines and Alps, in the form of deep marine sediments and ophiolites rocks.
Two 3D models of the Canneto mines are presented:
one general view at lower resolution, showing all four tunnel entrances
one at higher resolution, focussing on the entrances to the three lower tunnels
Location of the Canneto mines, along the Grondana creek, near Ferriere, Piacenza, Italy.
Ophiolites are thought to represent slices of oceanic crust that have been thrust or obducted onto a continental margin during collision. They are characterized by a sequence of rock types consisting of deep sea sediments overlying basaltic pillow lavas, sheeted dykes, gabbros and peridotites.
Ophiolites rocks (basalts, gabbros, peridotites) are mafic and ultramafic rocks, with highest content in ferro-magnesian minerals. This is the reason why they were mined in the Ferriere area.
Studying the origin of Ophiolites helps understanding their distribution in the present day landscape.
For this purpose are necessary a few concepts of petrography and plate tectonic evolution.
Ophiolite rocks sequences have helped interpreting the oceanic crust inner structure and its formation in association with the development of divergent plate boundaries and the opening of new oceans.
A typical ophiolite sequence is represented by:
Pillow basalts: resulting from the rapid cooling of hot, fluid magma that comes into contact with sea water.
Sheeted Dykes: swarms of basaltic dykes, representing the feeder channels for the overlying pillow basalts.
Gabbros: usually banded or layered, resulting from the crystallisation in the magma chamber at the base of the crust.
Peridotites: represent the upper part of the mantle and have usually been hydrated to serpentinites.
Similar processes must have occurred in the formation of the Piemont-Liguria ocean.
This ocean opened between Europe and Africa plates in Jurassic time, closed in Tertiary time and fragments of its crust were included in the Alps and Apennines.
The tectonic evolution of Europe (from Jurassic age to present day) allows to represent the evolution of the Piemont-Liguria ocean (here labeled as "Alpine ocean").
Click on the image to pause the animation and click on the left and right arrows to scroll back and forth.
From the previous animation, here is a summary of the evolution of the Piemont-Liguria ocean (purple stripe):
An ocean fully expanded in Cretaceous age (120 million years ago).
A series of outcrops of deep oceanic rocks squeezed within the present day Alps and Apennines.
Figure (3) shows the distribution of oceanic sediments and ophiolites in the Alps and Apennines, with the Ferriere area highlighted.
The two 3D models are shown below. You can play with them using these commands:
Click on the picture to open the 3D model.
Expand to full screen by clicking on the [ ↕ ] icon in the lower-right corner.
PC mouse: rotate (MB1), pan (MB2 or MB3), zoom (wheel).
Tablet: rotate (one finger), pan (two fingers), zoom (pinch fingers).
See details of each tunnel by clicking on the numbered annotations.
3D model of the three lower tunnels.
3D model panorama including also the upper tunnel.
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