Prof. Dr. L. (Leo) M. Kriegsman

Research interests

My main professional interests are in Structural Geology, Metamorphic Petrology, Geochronology and Tectonics, with a strong focus on high-temperature processes, including partial melting, in continental crust. Some key issues:

• Structural evolution and tectonic settings of metamorphic belts
• Global scale correlations of Precambrian orogenic belts
• Quantitative structural and kinematic analyses
• Developing and applying techniques to unravel pressure-temperature paths through mineral reactions and applied thermodynamics
• Fluid-rock and restite-melt interaction

On-going projects

1. Structural evolution, petrology and tectonics of the Pinjarra Orogen, Western Australia

Project in cooperation with Prof. Bas J. Hensen (School of Geology, University of New South Wales (Sydney, Australia) and Dr. Andreas Möller (now at the Institute of Earth Sciences, Geology, Johannes Gutenberg University, Mainz, Germany) and Dr. Dave Nelson (Geological Survey of Western Australia and Curtin University, Perth, Australia). Project aims are: (i) to trace the tectonic evolution of the Pinjarra Orogen (Northampton Block and Leeuwin Complex) during Pan-African (~750-500 million years) and Grenvillean (~1100-900 million years) times; and (ii) to improve models on the relation between Western Australia and other areas in Gondwana. Current results are: (i) an improved structural framework of the Pinjarra Orogen; (ii) the derivation of the P-T-deformation path of the Northampton Block; (iii) geochronological constraints from zircon and monazite U-Pb SHRIMP dating in Perth; (iv) evidence for back reaction between restite and in situ crystallizing melt (see 3.). One paper appeared 1998 (Kriegsman and Hensen, 1998), two have been delayed, but are now close to submission.

2. Fluid-rock interaction in granulites

This project involving Prof. Jacques Touret and Ph.D. researcher Lieselotte Bolder-Schrijver (Free University of Amsterdam) establishes the peak metamorphic fluid composition in (i) silica-undersaturated rocks during high-T (>850 oC) granulite facies metamorphism in Sri Lanka (Bolder-Schrijver et al. 2000); (ii) high-T calcsilicates from the Oonagalabi domain, Arunta Inlier, central Australia.

3. Back reaction between restite and in situ crystallizing partial melt

Melt extraction from migmatites is generally incomplete, leading to back reaction between in situ crystallizing melt and the restite upon cooling. This process has significant implications for (i) geothermobarometry; (ii) the derivation of pressure-temperature (P-T) paths; (iii) liquid compositions deduced from leucosomes; (iv) the inferred tectonic settings; (v) geophysical models using petrological data as input. Early project activities were:

• One paper published in Geology.
• A European Exploratory Workshop on this topic, funded by the ESF, was held in Turku, 23-25 August 1999.
• A review paper on this process has appeared in 2001 (Kriegsman, 2001); another paper is in review.

This project has been continued as a PhD project (Annika Nyström, 1.1.2000-31.3.2004), funded by the Academy of Finland. The implications of restite-melt back reaction are being assessed for trace element distributions in migmatites, for zircon and monazite morphology and U-Pb dates (Nyström and Kriegsman, 2003; Kriegsman and Nyström, 2003). LASER Ablation-ICP-MS analyses have been carried out at the EU-funded Geochemical Facility in Bristol, UK, October & December 2000. More LA-ICP-MS work will be done in Clausthal University, in cooperation with Dr. Kurt Mengel. In situ trace element and oxygen isotope analyses will be carried out at the NORDSIMS ion probe facility in Stockholm, late 2003, in order to trace prograde and retrograde zoning patterns in garnets and monazites.

4. Tectonometamorphic evolution and Nd isotope mapping of Pan-African South India, and correlation with Sri Lanka

Research project in collaboration with Dr. Ingo Braun and PhD researcher Bénédicte Cenki (University of Bonn, Germany), Dr. Ravindra Kumar (University of Trivandrum, India) and an M.Sc. student from the Free University of Amsterdam (Matthijs van der Gugten) supervised by me. Bénédicte Cenki succesfully defended her thesis on 30 January 2003. One paper appeared in 2002 (Cenki et al. 2002) on melt-producing and melt-consuming reactions, with general implications for the construction of P-T paths; a review paper on India and Sri Lanka in Gondwana was published this year (Braun and Kriegsman, 2003); a paper on the tectonic evolution is in review. Braun and Kriegsman are currently writing a new DFG proposal to continue further north, in the Palghat-Cauvery Shear Zone.

5. Numerical modelling of melt production, melt transfer and crustal rheology

Research project in collaboration with Prof. Jean Louis Vigneresse (CREGU, Nancy). The first aim is to examine crustal melting through numerical modelling, using cellular automata to reproduce numerically experimental melting and melt segregation under the influence of deformation (pure and/or simple shear). The second aim is to improve the phyical-mathemical basis for the rheological behaviour of partly molten crustal segments and to construct a physical basis for the extrapolation from small scale structures to large scale rheology. One paper close to submission

6. The role of fluorine in orthoamphibole dominated Cu-Zn-Pb deposits

Project on fluid-rock interaction with emphasis on: the role of fluorine in Cu-Zn-Pb deposits; how to assess original fluorine contents in metasomatically altered orthoamphibole-dominated deposits later subjected to metamorphism; and improving the use of fluorine as a pathfinder element. Original M.Sc project now extended as a PhD project of Leena Rajavuori (Turku University) through funding by the Renlund Foundation, Finland (started July 2000 and lasts until Dec 2004). Microchemical analyses carried out at the EU-funded Large-Scale Geochemical Facility, University of Bristol, UK through several grants, including one Marie Curie Fellowship. Papers published so far: Rajavuori and Kriegsman, 2002.

7. New developments of cathodoluminescence in mineralogy

PhD project of Joachim Lindblomi (Turku University; intended to improve applications of luminescence spectroscopy in mineralogy. Funded by the Renlund Foundation and the Graduate School of Geology in Finland (started July 2001, lasts until June 2005).

8. Partial melting of restitic xenoliths

Crustal melting can be studied along several lines of research: (i) petrological characterization of natural migmatite and granulite complexes (see projects 1-3); (ii) experimental simulation at varying physical and chemical parameters; (iii) numerical modelling (see project 5); and (iv) the study of small fragments of crustal rocks undergoing partial melting that were rapidly brought to the Earth's surface by volcanic eruptions and now occur as xenoliths within lavas. In this field, I cooperate with Dr. Ingo Braun in Bonn (ref. 8) and, more recently, with PhD researcher Antonio Alvarez M.Sc. and Dr. Bernardo Cesare (University of Padova, Italy). The latter PhD project uses abundant crustal xenoliths in dacitic lavas of the Neogene Volcanic province in southeastern Spain, and in particular those of Mazarron. Project aims are: 1) the definition of the various reactions of partial melting that produce garnet, cordierite, hercynite, orthopyroxene and ilmenite; 2) the geochemical characterization of minerals and melts; (3) evaluation of P-T conditions and mode of melting (e.g., equilibrium or disequilibrium).Project with intended to improve applications of luminescence spectroscopy in mineralogy.