We use the remarkable similarity between microstructures preserved in naturally and experimentally deformed quartzites as a basis to evaluate quartzite flow laws and their application to natural conditions. The precision of this analysis is relatively high because of the well-constrained deformation history of naturally deformed rocks from the Ruby Gap duplex, Central Australia. The external state variables during deformation in the duplex are well constrained by a combination of thermochronological, microstructural and structural observations. Using a flow law with the form _ e Af m H 2 O s n exp ÀQ=RT , our analysis indicates that values of log (A)=±11.20.6 MPa ±n /s and Q=135 15 kJ/mol provide the best description of the combined natural and experimental constraints with values of m=1 and n=4. Motivated by the results of our analysis, we also evaluated the influence of water fugacity on strain rate determined in the laboratory. In this case, we concur with a previously published suggestion that the measured effect of water fugacity (_ e G f 2 H 2 O ) is likely a manifestation of a change in deformation process with increasing stress. The results of this study provide further support for the application of quartzite flow laws to understand deformation conditions in the Earth, and emphasize the important insights that can be gained by analyzing deformation microstructures in naturally deformed rocks.

Study of geochemistry, examination of isotope ages of detrital minerals, palaeomagnetic analysis, and a study of the trilobites were performed to provide constraints on the palaeogeographical position of the Holy Cross Mountains in Late Ediacaran–Early Palaeozoic time. The geochemical results indicate an active continental margin or continental island arc provenance of the Ediacaran sediments. Sediments from a passive continental margin were deposited here during the Cambrian and Ordovician. The palaeomagnetic pole isolated from Cambrian rocks of the Małopolska region of the Holy Cross Mountains corresponds to the Cambrian segment of the Baltic apparent polar wander path. Isotope age estimations indicate that Cambrian sediments of the Małopolska region contain detritus not only from a latest Neoproterozoic source but also from sources with ages of c . 0.8–0.9 Ga, 1.5 Ga and 1.8 Ga. The Małopolska, Brunosilesia, Dobrugea and Moesia terranes, which originally developed near the present southern edge of Baltica and were partly involved in the Cadomian orogen, were dextrally relocated along its Trans-European Suture Zone margin. The first stage of this movement took place as early as latest Ediacaran time, while Baltica rotated anticlockwise. Anticlockwise rotation of Baltica at the Cambrian–Ordovician boundary implies further dextral movement of the Małopolska block.