Field trip registration is now closed. There were not enough bookings for the West Eifel, Nördlinger Ries or Ivrea Zone to run. Delegates who booked places on these trips will be refunded or, if they notify the organisers, transferred to the remaining trips.
The following field trips are offered at Goldschmidt 2007. Full details of each of these trips is given below this table.
Field Trip 1. One day trip to the 13ka Laacher See Volcano and the Quaternary East Eifel Volcanic Field.
Saturday 25 August 2007 - Day Trip
Leader : G. Wörner (Univ. Göttingen; Germany)
Maximum number of participants : ca. 40 (one coach)
Costs (excluding meals and drinks) : 50 Euro per person
Bring food and drinks for the day. The final stop will be the Vulkan-Bräu Restaurant where local beer (Vulkan-Pils) and food will be served.
Logistics: Transport will be by coach from Cologne to the Laacher See Volcano (c. 80 km). Weather permitting, we will take a 4 km hike (half) around crater lake and to a viewing tower. We will visit different large pumice quarries of Laacher See Tephra and well-exposed scoria cones. No field boots are required, but sturdy footwear and rain gear is recommended.
Geology: The East Eifel Volcanic Field and the Laacher See Volcano (13 ka) represent the largest eruptions in Central Europe in Late Quaternary times. The phreato-plinian Laacher See Tephra deposits are exceptionally well exposed in large pumice quarries where different eruptive and depositional facies (plinian fall and flow deposits, phreatomagmatic surges, and transitional) can be observed. The systematic compositional zonation from highly evolved, phenocryst-poor phonolite pumice at the base of the deposit to mafic and hybrid, crystal-rich phonolite represents a textbook example of compositional gradients in shallow magma chambers (see Fig. 5.17 in Understanding the Earth by Brown et al. (eds) Cambridge Univ. Press). Processes of magmatic differentiation and the zonation of the chamber will be discussed based on a systematic collection of pumices and crustal xenoliths. The phonolite is multiply saturated with sanidine, plagioclase, beautiful blue hauyne, amphibole, clinopyroxene, biotite, sphene, apatite, magnetite, zircon (the latter only in the most evolved phonolite). Chemical, mineralogical and isotopic composition of the phonolite pumices and their phenocrysts have been used to quantify igneous processes such as crystal fractionation and assimilation. The erupted c. 6 km3 (d.r.e.) of phonolite magma can thus be related to about 60 km3 of a primitive basanite parent with relatively little crustal assimilation. U-series isotope analyses on minerals from cumulate rocks suggest a time for igneous differentiation of the zoned magma body within 10 to 20 ka with most phenocrysts being coeval with the time of eruption.
Mingled phonolite+cumulate+basanite juvenile clasts from the final stages of the eruption attest to a mafic recharge of the magma system during the eruption.
<9>A variety of contact metamorphic and partially molten crustal xenoliths can be placed within the crustal column below the Eifel and thus constrain the depth of the magma chamber between c. 3 and 10 km.
A hike (partially) around the crater lake will demonstrate the geology of the crater walls and areas of active CO2 degassing into the lake. One of the most beautiful Romanic abbeys in Germany (Maria Laach http://www.maria-laach.de/), built between 1093 and 1156 is located inside the crater and will also be visited.
A deeply dissected scoria cone (Eppelsberg) erupted parental basanite magma and deposited phreatomagmatic surges at the base, constructed the main strombolian cone which is overlain by late surge deposits and layers from Hawaiian fire fountains.
An intermediate hauyne-bearing tephrite has been quarried since Roman times. Quarries expose the top and base of the flow and cut into ancient underground caverns from mining the millstones.
Further information, digital maps, e-prints and a photo gallery of exposures that we will visit will be available from the folder Goldschmidt Conference Eifel Field Trip on the following website http://134.76.75.184
Field Trip 2. A volcanic hike in the Tertiary Siebengebirge explosive subaqueous eruptions, syn-volcanic intrusions and medieval castles
Saturday 25 August 2007 - Day Trip
Guides: Holger Paulick, Melanie Moll (Univ. Bonn; Germany)
Maximum numbers of participants: ca. 40 (one coach)
Costs (excluding meals and drinks): 50 Euro
Walking conditions: The hike is approximately 10 km mainly on well-established hiking tracks. The route includes several steep up and downhill stretches. A moderate level of fitness is required. Adequate footwear and clothing are essential.
Logistics: Transport will be by coach from Cologne to the start of the hike at Magarethenhöhe (Siebengebirge). The route will take the participants from this starting point up to the ruins of the Löwenburg castle and then on through the Siebengebirge National Park including geological and scenic stops. Lunch will be at the Milchhäuschen Restaurant. After a detour to the Ofenkaulen area (Trachyttuff exposures) the route will continue up to the ruins of the Drachenfels located on a trachyte dome with sanidine megacrysts. This is a classical stop frequented by 19th century travelers to the Rhine area. A steep descent is required to meet the coach at the base of the Drachenfels. The final stop is a local vineyard at Oberdollendorf for tasting of local products and evening meal. Return by coach to Cologne.
Geology: The Siebengebirge is one of several areas of volcanic activity in the Tertiary in Germany. It includes mafic to felsic magmas with alkaline affinities that were erupted between 25 and 19 Ma. Post-volcanic erosion was substantial due to the uplift of the Rhenish Massif and the incision of the Rhine valley and many of the volcanic rocks exposed represent the sub-volcanic root zones of volcanoes which perished long ago. Recent volcanological and petrological investigations reveal new insights into the processes of the Siebengebirge volcanism and these results will be presented and discussed during the field trip.
Despite the intense erosion there are remnants of volcanic deposits bearing evidence of the nature of volcanic activity at the time. Importantly, felsic volcanism includes explosive eruptions responsible for the formation of the Trachyte Tuff. This unit was already investigated by natural scientists interested in the solid earth in the 19th century and its volcanic origin was readily established. However, recent investigations reveal that primary pyroclastic rocks, such as fall deposits and ignimbrites, are largely absent and that deposition took place in a subaqueous environment. Textural and sedimentological evidence for this new interpretation will be investigated during this field trip.
Many of the coherent volcanic rocks, responsible for the hilly morphology of the Siebengebirge today, were emplaced as shallow intrusions into the Trachyte Tuff. A classical example is the sanidine megacryst-bearing Drachenfels Trachyte. The orientation of these crystals in 3-D supports the interpretation of a doming magma body. Mafic volcanic rocks are generally present as dikes and irregular sub-volcanic intrusions, however, some relics of effusive eruptions are preserved.
The petrogenesis of the Siebengebirge magmas is complex and still poorly understood. The mafic rocks can be subdivided in Ne-normative basanites, alkali olivine basalts, and olivine basalts. Local occurrences of peridotite xenoliths, high MgO values (>8 wt.%) and upper mantle-like Sr-isotope signature (87Sr/86Sr: 0.7034 - 0.7039) support the interpretation that these rock types represent primary melts. Traditionally, the differentiated volcanic rocks have been subdivided in three suites based on differences in the calculated degree of SiO2 saturation derived from normative mineral assemblages. These suites are: phonotephrite to alkalitrachyte (SiO2 under-saturated); hawaiite to trachyte (SiO2-saturated), and hawaiite to quartz trachyte (SiO2 over-saturated). A positive correlation of increasing SiO2 and 87Sr/86Sr values indicates that differentiation processes included assimilation of continental crust material. More detailed geochemical investigations, including isotopic (Nd, Pb, Hf) analyses are currently underway in order to further constrain the process of magma generation and evolution in the Siebengebirge.
