An understanding of fault weakening during earthquake slip is essential to comprehend the facilitation of rupture propagation. Argued that these shear zones indicate an east-vergent extensional regime based on the truncation of the Ussuit unit in some of the thrust sheets. This combination of coeval folding and shearing appears best interpreted as continued, https://datingrated.com/blackwink-review/ post-collisional north–south convergence, in which crustal thickening was compensated by east–west escape or collapse . In the Western Alps, the External Crystalline Massifs are key places to investigate the kinematics and thermal structure of a collisional crustal wedge, as their paleo-brittle/ductile transition is now exhumed at the surface.

Basic Concept of IAA and Previous Studies

Subsequently, the crystals were wrapped in an approximately 1 × 1 mm sized platinum capsule and analysed following a two-stage analytical procedure . This is characterised by measuring the 4He extraction, and by analysing the 238U, 232Th and Sm content of the same crystal. During the first step, that was operated by HeLID automation software through a K8000/Poirot interface board, the Pt capsules were degassed in high vacuum by heating with an infrared diode laser. The extracted gas was purified using a SAES Ti-Zr getter at 450°C and the inert noble gases as well as a minor amount of rest gases were measured by a Hiden triple-filter quadrupole mass spectrometer equipped with a positive ion counting detector. Re-extraction was performed for each sample to control the quantitative amount of extracted helium.

Three of them were dated by the AFT and ZHe method. AHe ages were obtained from all samples. And Tagaki, H. Isotopic ages of rocks and intrafault materials along the Median Tectonic Line—An example in the Bungui-toge area, Nagano Prefecture. Journal of Geological Society of Japan, 94, 35–50. Min, K.D., Kim, O.J., Yun, S., Lee, D.S., and Joo, S.H. An applicability of plate tectonics to the post-Late Cretaceous igneous activities and mineralization in the southern part of south Korea .

Fault dating in the Canadian Rocky Mountains: Evidence for late Cretaceous and early Eocene orogenic pulses

& Tagami, T. Timing of brittle deformation within the Nojima fault zone, Japan. Solum, J. G., van der Pluijm, B. A. & Peacor, D. R. Neocrystallization, fabrics and age of clay minerals from an exposure of the Moab Fault, Utah.

This thermal peak is synchronous with crustal shortening documented in the basement. (U–Th–Sm)/He data and thermal modeling point toward a coeval cooling of both massifs, like other ECM, at around 18Ma +/−1Ma. This cooling was related to an exhumation due to the initiation of frontal crustal ramps below the ECM, quite synchronously along the Western Alps arc. Ar–Ar ages in volcanic rocks can be interpreted as the age of effusion as closing temperatures for different mineral species are negligible due to rapid cooling (e.g. McDougall and Harrison 1999).

In any case, the correlation of geological events and K–Ar ages from authigenic illite separates requires a careful consideration of the fundamental assumptions of the K–Ar-illite method (e.g. Clauer and Chaudhuri 1998). Earthquake swarms attributed to subsurface fluid injection are usually assumed to occur on faults destabilized by increased pore-fluid pressures. However, fluid injection could also activate aseismic slip, which might outpace pore-fluid migration and transmit earthquake-triggering stress changes beyond the fluid-pressurized region.

The IC values, which are inversely proportional to the illite crystallinity, are defined after Kübler as half-height width of the 10 Å XRD peak. The values for the illite crystallinity may range from 0.06 Δ°2θ for ideally ordered muscovite up to 1 Δ°2θ for illite/smectite mixed layers (Kübler 1964, 1967, 1968). And Renac, C. Smectite to illite conversion and K-Ar ages. Tanaka, H., Uehara, N., and Itaya, T. Timing of the cataclastic deformation along the Akahashi Tectonic Line, central Japan. Contributions to Mineralogy and Petrology, 120, 150–158.

To determine the polytypism of illite, powder compounds were prepared and scanned in 561 steps in a range of 16–44°2θ, using a scan step of 0.05°2θ and an integration time of 30 s per step. The allocation of peaks to the corresponding polytypes was done as suggested by Grathoff and Moore and Grathoff et al. . The randomness of orientation for the powder sample preparation was checked using the Dollase factor . We tried to quantify the amount of different polytypes by several methods as described by Reynolds ; Maxwell and Hower ; Caillère et al. ; Grathoff and Moore and Grathoff et al. , but due to bad peak shapes none of the used methods yield reasonable data. For this reason the general abundance of the polytypes was estimated as suggested by Grathoff and Moore . The abundance of different polytypes in the analysed samples is sown in Table3.

Lin, A., Shimamoto, T., Maruyama, T., Sigetomi, M., Miyata, T., Takemura, K., Tanaka, H., Uda, S., and Murata, A. Comparative study of cataclastic rocks from a drill core and outcrops of the Nojima fault zone on Awaji Island, Japan. And Liewig, N. Episodic and simultaneous illitization in oil-bearing Brent Group and Fulmar Formation sandstones from the northern and southern North Sea based on illite K-Ar dating. Bulletin of the American Association of Petroleum Geologists, 97, 2149–2171. For this work 2–4 apatite single crystals aliquots from seven samples as well as three zircon single crystals aliquots from four samples were carefully handpicked using a binocular and petrologic microscopes. Only inclusion and fissure-free grains showing a well defined external morphology were used, whereas euhedral crystals were preferred. The shape parameters of each single crystal were determined, e.g. length and width, and archived by digital microphotographs in order to apply the correction of alpha ejection described by Farley et al. .

The mean Dpar values for the three samples range between 1.64 and 1.75 μm . The zircon samples yield (U-Th)/He ages between 276.8 ± 6.4 Ma and 141.5 ± 3.4 Ma showing a positive correlation with elevation (Fig.9). The weighted means of the four samples vary from 263.6 Ma to 198.9 Ma . Schematic sketch of the shallowing Nazca Plate (modified from Kerrich et al. 2000; Urbina 2005). The ages for Cerro Tomolasta and El Morro are from this publication.

Clays and Clay Minerals, 44, 818–824. In this paper, the authors investigate a fault model with spatially variable frictional properties and pore pressure and develop closed-form equations to predict the stability of slip on heterogeneous faults. The mechanochemical effects on the thermal decarbonation of dolomite were determined via TG and DTA (Figs. 2C and 2D). Thermal decarbonation can occur due to thermal heating during slip, unless the strain rate is low. Based on the endothermic reaction accompanying a weight loss of ∼47 wt% at ∼780 °C, the occurrence of single-stage thermal decarbonation in dolomite was confirmed.

The analysed illite fractions are composed mainly of the 1Md and 2M1 polytypes and only subordinate 1 M illite. The 1Md polytype is dominant in the d is also the dominant polytype, except samples APG and APG showing the 2M1 polytype as dominant. The 2–6 μm fractions are mostly made up by 2M1 illite.

A lineament and geological map of the study area, in front of the Greenland ice sheet. Map modified from Garde and Marker . Larsen, B. T., Olaussen, S., Sundvoll, B. & Heeremans, M. The Permo-Carboniferous Oslo Rift through six stages and 65 million years.

Therefore, duplicate or triplicate experiments are required in the K-content analysis process. In addition, methods using natural polytype end-member standards as synthetic mixtures without using WILDFIRE© and methods such as BGMN®, Topas, Profex, AutoQuan, SIROQUANT, etc., based on Rietveld refinement are also used. The Rietveld refinement method is basically a function of domain size, strain, and instrumental factors. Therefore, it does not consider the structural characteristics of clay crystallites, which is a factor of quantitative analysis error. Boles et al. analyzed the results of evaluation experiments of WILDFIRE©-based full-pattern-fitting, End-member Standards Matching and Rietveld whole-pattern matching (BGMN®) quantitative analysis methods for synthetic samples. As a result, it was suggested that the WILDFIRE©-based full-pattern-fitting method is useful for samples with high 1Md illite content, in that it can utilize a data library of simulated patterns generated under various conditions of 1Md polytype .