Institute of Geological Sciences

Petrology: Research

Metamorphism and orogeny, central Alps

Experimental petrology

Oman meteorites (in German)

Crustal evolution in southern Oman

The ophiolite of Masirah Island in Oman

Metamorphism and orogeny, central Alps

Our research aims to understand fundamental processes of rock metamorphism. This serves primarily to interpret (A) the information stored in individual metamorphic rocks and (B) the significance of that information in orogenic cycles (and other processes of lithospheric scale).

A: To unravel the evolution of individual samples, we analyze them in detail using the petrographic microscope and various analytical tools (EMP, SEM, MS, XRF, XRD,...), and we utilize numerical models rooted in thermodynamics (Domino/Theriak, TWQ, MELTS, ...).

B: In the regional context, quantitative (pressure-temperature-time) results on the conditions of formation, derived from individual samples, are combined with tectonic models. For areas such as the Alps, this provides insight into orogenic dynamics. At lithospheric scale, the analysis of results obtained from many rock samples is again supported by numerical (FEM) simulations, this time of the large-scale (>100 km) thermal evolution in convergent plate settings. The purpose is to identify fundamental mechanisms of regional metamorphism and to characterize their mutual interdependence in space and time. In addition, we are active in experimental petrology to study the stability and chemical reaction relations of mineral solid solutions, and we develop thermodynamic models for these.

Click here for more details about our work in the Alps.

Experimental petrology

Phase equilibria involving rock-forming minerals (recently including: chlorite, ilmenite, garnet, ...) are studied using both hydrothermal cold-seal equipment and a piston-cylinder apparatus. The goal of such experimental work is to provide constraints for thermodynamic models of important solid solutions which in turn serve to compute the stable phase relations under conditions of elevated temperature and pressure (whole range of metamorphism).

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Crustal evolution of the Salalah region in southern Oman

East of Salalah (Dhofar) part of the Neoproterozoic Arabian crystalline basement and its intra-Cambrian sedimentary cover are exposed beneath the Mesozoic and Tertiary sequences. The history of this basement begins around 1000 Ma with the deposition of clastic sediments in an accretionary prism environment, the protoliths of the mica gneisses of the Juffa Group. Between 850 and 820 Ma, mantle derived melts start to intrude the base of the prism, the protoliths of the Banded Gneiss Complex of the Sadh Group. Around 815 Ma penetrative deformation at amphibolite facies conditions affects the rocks of both Juffa and Sadh Group. 15 Ma later, a suite of dioritic to tonalitic calc-alkaline plutons (Main Intrusive Group) intruded the Banded Gneiss Complex. At 750 Ma, a huge mass of granitic dykes intruded along a conjugated set of compressional brittle faults. The last important tectono-magmatic event recorded in the crystalline basement was the emplacement of a calc-alkaline dyke suite and small granitoids bodies favoured by extentional tectonism (ca. 700 Ma). The Neoproterozoic Mirbat Sandstone Formation was unconformably deposited on the fluvial deeply eroded crystalline. This temperate, low latitude glaciomarine sediments were deposited in a tectonically active horst-graben system during the break off of the Late Proterozoic supercontinent.

Detailed information about the studies in the Salalah region will soon appear on the pages of the Rock-Water Interaction group. Recent publications, unpublished theses and maps are currently listed here.

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The ophiolite of Masirah Island in Oman

The geological evolution of the Masirah Island can be subdivided in three major cycles:

Late Jurassic formation of oceanic crust and subsequent pelagic sedimentation.
Mid Cretaceous alkaline magmatism and emersion of the oceanic crust.
Uppermost Cretaceous emplacement of two ophiolitic nappes on the Arabian continental margin.

In the Masirah ophiolite, all members of a "classic" ophiolite sequence are present, although the gabbroic lower crust measures only 200 to 500 m in thickness, making the Masirah ophiolite a good exempla of thin oceanic crust formed at slow spreading regime. A palaeomagnetic reconstruction indicates ridge formation at latitude of 38 ±12°S and a polar wandering together with the Indian plate. After the Late Jurassic crust formation, the sedimentary record shows a continuous deepening below the CCD until the Late Hauterivian, when oceanic crust was uplifted above sea level and platform carbonates were deposited. Simultaneously, alkaline magmatism of OIB affinity developed a suites of small volcanic centres, dikes and small K-feldspar-rich granite bodies all oriented along NE - SW extensional structures. This Middle Cretaceous magmatism is interpreted as the result of intra oceanic rifting related to hotspot activity in response to the rearrangement of the plates in the Southern Hemisphere. The intraoceanic thrusting-resulting in the nappe structure of the Masirah ophiolite- and the obduction between Late Maastrichtian and Paleocene time coincide with the opening of the Carlsberg Ridge. The Middle Miocene block faulting registered on the island of Masirah is correlated with the extentional tectonics caused by the opening of the Gulf of Aden. The Masirah Ophiolite represents an unique example of oceanic crust obducted 100 Ma after formation allowing the reconstruction of the complex history of this portion of the Proto Indian Ocean.

Detailed information about the studies on Masirah Island will soon appear on the pages of the Rock-Water Interaction group. Recent publications, unpublished theses and maps are currently listed here.

Contact for more information.