Michał Śmigielski

Exhumation history of the Tatry Mountains, Western Carpathians, constrained by low-temperature thermochronology

This study tests alternative models for the growth of the Tatry Mountains (Central Western Carpathians) by the application of low temperature thermochronology. Zircon (U + Th)/He ages from the north of the range are mostly between 48 to 37 Ma and indicate cooling prior to the onset of forearc sedimentation in the region (42–39 Ma). In contrast, zircon (U + Th)/He ages in the south of the range are around 22 Ma. Apatite fission track ages across the sampled sites range from 20 to 15 Ma. Apatite (U + Th)/He ages range from 18 to 14 Ma with little variation with elevation or horizontal location. Based on thermal modelling and tectonic reconstructions, these Miocene ages are interpreted as cooling in the hanging-wall of a northward dipping thrust ramp in the current location of the sub-Tatric fault with cooling rates of ~20 °C/Myr at ~22-14 Ma. Modeled cooling histories require an abrupt deceleration in cooling after ~14 Ma to <5 °C/Myr. This is associated with termination of deformation in the Outer Carpathians, and is synchronous with the transition of the Pannonian Basin from a syn-rift to a post-rift stage, and with termination of N-S compression in the northern part of the Central Western Carpathians. Overall, the timing of shortening and exhumation is synchronous with the formation of the Outer Carpathian orogen and so the Miocene exhumation of the Tatry record retro-vergent thrusting at the northern margin of the Alcapa microplate.

CHOMIK: a multi-method approach for studying Phobos

CHOMIK is the name of a penetrator constructed for sampling and retrieval of Phobos surface material. It formed an integral part of the Phobos Sample Return Mission. In this paper we present its construction and intended mode of operation, since the concept is still viable for future missions either to Phobos or to other small bodies of similar dimensions. We take Phobos as an example to describe the science case for such an instrument and how it might be utilized to resolve important open issues regarding the origin of the Martian moons. Concerning the latter, we place emphasis on measurement techniques and analysis tools for mapping trace element concentrations in returned sample.

Self-Similar Pattern of Crystal Growth from Heterogeneous Magmas: 3D Depiction of LA-ICP-MS Data

Crystals grown from mixed magmas are characterized by extreme geochemical heterogeneity. The system is self-similar which is reflected in a complex pattern of element distribution in the crystal. New tools are required to show the complexity. 3D depiction (digital concentration-distribution models DC-DMs) combined with fractal statistics is an ideal tool for the identification and description of any subsequent change occurring due to the chaotic processes. LA-ICP-MS analysis gives simultaneous information on the concentration of many elements from the same analysed crystal volume. Thus the data collected are an ideal basis for the calculation of both DC-DMs and fractals. Simultaneous information retrieved by LA-ICP -MS on both compatible and incompatible elements and further data processing allow the determination of the process dynamics in terms of element behavior: antipersistent/persistent, being incorporated according to Henry’s Law or beyond it. The multi-method approach can be used for any system showing geochemical variability.

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Abstract An alkali feldspar megacryst from a protomylonite has been studied using laser ablation-ICP-mass spectrometry combined with cathodoluminescence imaging, Raman spectroscopy, and electron probe microanalysis. The aim was to determine the original (magmatic) geochemical pattern of the crystal and the changes introduced by protomylonitization. Digital concentration-distribution models, derivative gradient models, and fractal statistics, e.g., Hurst-exponent values are used in a novel way to reveal subtle changes in the trace-element composition of the feldspar. Formation of the crystal is reflected in a slightly chaotic trace-element (Ba, Sr, and Rb) distribution pattern that is more or less characterized by continuous development from a fairly homogeneous environment. Derivative gradient models demonstrate a microdomain pattern. Fractal statistics show that element behavior was changeable, with Ba and Sr always more persistent (continuing) and Rb always less persistent, with the latter showing a tendency to migrate. The variations in the Hurst exponent are, however, too large to be explained by magmatic differentiation alone. The observed element behavior may be explained by structural changes revealed by Raman spectroscopy and CL. In high-strain domains, T–O–T modes become stronger for Si–O–Al than Al–O–Al linkages. Increasing amounts of Al–O−–Al defects are demonstrated by cathodoluminescence. Both may result from small-distance diffusion creep, making the crystal geochemical pattern slightly patchy. In turn, the marginal part of the megacryst has a mosaic of randomly orientated, newly crystallized K-feldspars. The re-growth is confirmed by trace-element distribution patterns and fractal statistics which identify an abrupt change in the transformation environment. The novel set of tools used in this study reveals a complicated history of megacryst formation and transformation that otherwise would be difficult to unravel and decipher.