Section compiled by Sabine Husch.

"The calculations of the Professor were perfectly correct. We were already six thousand feet deeper down in the bowels of the earth than anyone had ever been before. The lowest known depth to which man had hitherto penetrated was in the mines of Kitzbuhel, in the Tirol, and those of Wurttemberg."
Jules Verne, "Journey to the Center of the Earth" (1864):

This report documents the field observations conducted during a two-day reconnaissance of the Röhrerbühel licence area, which is under the ownership of Ekometall Exploration Ltd (EMEX). The survey was carried out by Anna Rasch- Christensen and Sabine Husch in August 2023. It also includes historical data related to the mining activities in the region.

Location


The Röhrerbühel licence area is situated north of the town Kitzbühel in Tirol in a low hilly countryside known as Bühlbach. It covers the east-west extending historic mining area from the Kitzbühler Ache valley to the Reiter Ache valley, a strip 2 km wide and 7 km long. Presently, this area is mostly covered with dense forests and undergrowth. The village of Röhrerbichl and a rural road can be found within the licence area. Extensions to the current licence are under application to the north and west.

Figure 1: Overview map of the Röhrerbühel licence area acquired in 2023 showing the outline of the historic mining area and the location of the historic mining heaps.

 

Historic Data


The Röhrerbühel area has been intermittently mined for silver and copper since the 1500s. Remarkably, it held the record for the world’s deepest shafts at 886 metres until 1872. The most important documents regarding mining activity include the concession maps for the ore heap cuttings – these maps also still contain the locations of the old shafts. All historic shafts, except for one, are collapsed today with little to no trace of their former existence on the surface. The only shaft still visible at the surface originates from a more recent 1952-55 Röhrerbühel prospecting campaign. Figure 2 depicts the mining shafts and tunnels as documented in a 1930 report by Otto Santo-Passo, following a prospecting campaign in this historic mining area.

Figure 2: (2x maps) Overview of the historic Röhrerbühel mine, as mapped by Otto Santo-Passo in 1930. The positions of the shafts "Daniel Schacht," "Geisterschacht," "Schurfschacht," and "Gröllenbauschacht" are indicated on this map.

A more comprehensive depiction of the specific shaft locations is provided by a mine map created in 1789 by Ignartz Karl Miller. Figure 3 presents enlarged sections of this map, offering precise details regarding the individual shaft positions.

Based on these maps, the historic shafts were located during the on-site reconnaissance.

Figure 3: Overview of the precise locations of all shafts from the 1789 mining activities in Röhrerbühel mapped by Ignartz Karl Miller.

Figure 4 depicts a more recent georeferencing work by Gerd Kohler, including the mining map of the operations between 1952 and 1955 as outlined in red. Notably, the prospecting shaft "Schurfschacht 52" remains the sole visible shaft at the surface.

Figure 5: Plan of the mine workings in Röhrerbühel from 1789 (blue) and 1952 (red) with the locations of the shafts
(by Gerd Kohler).

Geology


Detailed geological investigations were carried out during the prospecting work in the old mining site Röhrerbühel from 1952 to 1955. According to Hans Helfrich, the geological setting can be outlined as follows:

The ores are situated within weakly metamorphosed, sandy-shale sedimentary rocks (phyllite stage), which have been transformed into Falbenschiefer, a regional lithological term for chlorite- and titanite-rich quartz-sericite-phyllite, near the ore-bearing vicinity. Petrographically, these sediments can be classified into the Wildschönau Series of the North Tyrolean Graywacke Zone.

The tectonic style is characterised by a gently overturned folding structure trending towards the north. In the vicinity of its crest, a deep-seated, steeply inclined mylonite zone with an ENE orientation is exposed. This mylonite zone was formed prior to the mineralisation of the deposit. Connected to them are cataclastic, mylonitic structures-generating processes that strongly disrupted the surround- ing host rock. The Falbenschiefer is the result of the interplay between these movements and the deposition of ascending hydrothermal solutions. From these solutions pyrite was initially deposited, which in turn, due to a tectonic phase, was separated from ores deposited at a later stage – these ores being fahlore, chalcopy- rite and bornite. Primarily, these ores are associated with the Falbenschiefer.

Younger para-post-mineral tectonic movements created a variety of tectonic boundary forms for the ore bodies. Eastern striking faults resulted in the stepped offsets visible in the deposit today. The attachment to a regional ENE- oriented geological structure, which has been altered by more recent block displace-ments, characterises the position of the deposit within the northern greywacke zone.

Mineralisation


Generally, the mineralisation in the Röhrerbühel licence area can be classified into two ore formation groups:

  • Fahlore-dominated ore bodies exist in the forms of blocks, lenses, veins, seams, and impregnations.
  • Chalcopyrite-dominated ore bodies occur as veins and lenses.

Most ore formations belong to the Fahlore-dominated group (a). They consist of tectonically bounded blocks and lenses, typically up to 30 cm thick, which are interpreted as fragmented remnants of a once continuous vein body. Additionally, there are thin ore seams, less than 1 cm thick, creating a mesh-like pattern. Microscopically, distinct discrepancies are observed between the ore formation and relict sedimentary structures. These structures are clearly intersected by transverse ore formations.

Local infiltration of ore formation into the bedding and schistosity of the ore-bearing rocks creates a vein network. Genuine vein mylonite formation is also noted in the ore deposit area, intersecting all minor folding structures and positioned as a dome rift. Individual ore bodies now align parallel to an s-plane. Mylonitization movements continued after mineralisation, influenced by the harder Falbenschiefer and ore bodies, which guided the course of the younger generation. The mineralisation in this area is predominantly Fahlore, with copper, sulphur, iron, antimony, and mercury present. Silver content historically motivated extensive mining operations. Chalcopyrite, bornite, and potentially other copper minerals gain economic importance. Pyrite, often the oldest mineral, maintains its original shape despite intense tectonic activity.

The ore-bearing rock, Falbenschiefer, contains anatase-rutile pseudomorphs along- side titanite dust and graphite. Quartz, iron-rich carbonate, barite, anhydrite, and gypsum appear as accompanying minerals, along with oxidation minerals like malachite, limonite, and azurite.