Geo Erlebnis Argenthaler Waldsee

About the trail

 

Between the Argenthaler Waldsee and the south-east located Quartzite opencast pit a Geological nature trail leads on a length of about 5,5 km through 20 stages describing the changeful history of this old mining region. The information boards at the stages cover a great variety of aspects, are multiple illustrated and understandingly composed. The trip through all stages will take about 2,5 to 3 hours. Start and end point is the parking area at the Argenthaler Waldsee.
In Summer the Argenthaler Waldsee and the Biergarten are opened for swimming and refreshing (with costs, but supervised) to relax and recreate from the exhausting Geo adventure.

Smelting of ore

Modern ore mining occurs in the Rheinboellerhuette since 1598. At first the ore was taken from the proximity of the Guldenbachtal, later the radius was spread more and more. Until 1860 30 ore pits supplied the Rheinboellerhuette.
In 1893 the last furnace of the Rheinboellerhuette was blown off because the iron and steel production has been moved to Saar and Rhein-Ruhr.

Ore mining

The ore pit 'Grube Neufund' was one of the suppliers of the Rheinboellerhuette. Here Brown Iron Ore (Limonite) was mined in open pit since 1824. It is located under a 2 to 10 meter sized cover. Already in 1889 the mining was temporarily closed for lack of demand.
With the beginning of World War 1 in 1915 mining started again, but to increase rentability it was changed to deep mining. Due to improved machines and better profitability deep mining was changed back to surface mining in 1918. Until 1925 the number of employees of the Grube Neufund rose up to 60.
In 1930 the last mining company, the 'Gewerkschaft Neue Abendsonne' went bankrupt and the technical equipment was removed. In 1935 the last operating was suspended finally.

Iron ore in the Hunsrueck

The are three different deposits of ore in the Hunsrueck: Brown Iron Ore (Limonite), Red Ochre (Hematite) and Magnetic Iron Ore (Magnetite). Hematite and Magnetite basicallly differ from Limonite and are rare. Limonite has been mined in the Hunsrueck in about 200 pits, like in Grube Neufund here, whereas Hematite and Magnetite were dug in only 30 pits.

Limonite

Limonite is a comparatively young rock, it originates in Tertiary about 60 MBP. The continents had almost reached their current position, but temperature was higher than today.

In Oligocene (32 ? 24 MBP) the sea level rose. The Variscan mountains have been weathered strongly and were ablated mostly. So a flat sea propagated here, where the Soonwald was one island in it. Subtropical climate caused thick Laterite soils. Groundwater had little depth and could be saturated with iron and manganese. The acidic rivers transported the dissolved iron to the coast. During the inflow into the sea the iron crystallized and precipitated to the bottom where chunks of 5 to 60 cm were built, containing less than 45% iron.
Limonite is not a true mineral, because of its building processes it's called a 'weathering rock'.

Hematite and Magnetite

In contrast Hematite and Magnetite are very old rocks. Hematite has been built by analogical processes like the Limonite but contains up to 70% iron. Magnetite has volcanic origin and contains more than 70% iron.

In Devonian (417 MBP) most mainland was located in the south of the earth as the continent Gondwana and around Equator the much smaller continent Laurussia (Old Red Sandstone continent).Between Gondwana and Laurussia there were many islands, one of them was the 'Mitteldeutsche Schwelle'. It separated a strait, the Hunsrueck Slate Sea, from the ocean. On Old Red and the Mitteldeutsche Schwelle rose mountains near the coast and their rivers transported much stones into the sea.
During a period of 60 mio. years the bottom of the sea saged, so that strata of about 10 km thickness could be deposited. Because of its own weight these strata compressed itself from Sand to Sandstone and from Clay to Mudstone.

At the end of Devonian the sea went dry and was falted during Carboniferous (325 MBP) to the Variscan Mountains. The two continents Gondwana and Laurussia clashed to the super continent Pangea. At the junction the 'Hunsrueck-Suedrand-Stoerung' occured and in the south of it the 'Saar-Nahe-Basin'. The 'Hunsrueck-Suedrand-Stoerung' marks the ancient subduction zone, where the 'Mitteldeutsche Schwelle' slid on Old Red.
The rocks have been compressed over a period of about 25 mio. years, Sandstone to Quartzite and Mudstone to Slate. During the folding they have been multiply relocated, so that even the oldest strata of Colored Slate were put from the bottom to the top.

Dissolved iron infiltrated fissures an was deposited there by building Hematite.
The super continent Pangea drifted to the North and so the climate changed from tropical-humid in Carboniferous to subtropical-arid in Perm 280 MBP. In the region of the Saar-Nahe-Basin volcanism occured. Credentials are the Donnersberg and the Kreuznacher Rhyolitmassiv with the Rotenfels. During the volcanism the rare Magnetite originated, it is ? compared with the Hematite ? a little bit younger.

Sources

Information panels of the Geo-Erlebnis Argenthal. Further information may be retrieved from Gemeinde Argenthal, Thiergartenstrasse 2, D-55496 Argenthal, Phone +49.6761.965966, Web www.argenthal.de
Paleogeographic maps by Ron Blakey, Department of Geology, Box 4099, Northern Arizona University Flagstaff, AZ 86011, Web http://jan.ucc.nau.edu/~rcb7/index.html

Questions

1. How thick is the Limonite stratus in the Grube Neufund?
2. Which elevation has todays face of the Argenthaler Quartzite quarry?
3. Which of today's unique fish species lived in the flat areas of the Devonic sea and what was it's singularity?
4. Wich cities were connected by the roman trunk road through the Argenthaler Wald?
5. Where have the crude ore been smelted after the closing of the Rheinboellerhuette?
6. Which hourly wages were paid to the miners in the 1920 years?

Log validation

1. To claim this cache as found you have to write an email containing the GC-Code as subject, a valid return address and as body text the answers to the questions to GeoMops@web.de . You will receive an answer with the permission to log if your answers are correct within a few days.
2. Find the Hunsrueck Crocodile take a photo of you on or beside it and attach the picture to your log.

Logs without permission and / or picture will be deleted.

I hope you will enjoy this cache ? have fun!