352 documents found in 481ms
# 1
Hierold, Johannes • Körting, Friederike • Kollaske, Tina • Rogass, Christian • Harms, Ulrich
Abstract: The International Continental Scientific Drilling Program (ICDP) performed a dual-phase scientific drilling project to investigate mountain-building processes called Collisional Orogeny in the Scandinavian Caledonides (COSC). The borehole COSC-1 was drilled through the Lower Seve Nappe, as the first of two 2.5 km deep drill holes close to Åre, central Sweden. The recovered rocks comprise a 1650 m thick suite of high grade gneisses and amphibolites with clear Seve Nappe affinities, while the lower 850 m comprise rather homogenous mylonitic gneisses with interfingered K-rich phyllonite bands of cm to several m size and some intercalated amphibolites. The different lithologies all crosscut the core in a subhorizontal direction with foliation of gneisses and phyllonites in the same direction. Albite and garnet porphyroblasts with pressure shadows show syn-deformational growth and the same sub-horizontal alignment. The focus of this study was to detect chemical and mineralogical differences in mylonitic and host rocks and to relate these differences to either metasomatism and deformation or inherited source rock variance. Another goal of this work is to compare chemical core scanning instruments. For this purpose two different X-Ray Fluorescence (XRF) techniques, Laser Induced Breakdown Spectroscopy (LIBS) and hyperspectral imaging served to measure seven samples from the lower 850 m of the COSC-1 core. This data publication comprises the datasets gained in the course of this study. The metadata (OF WHAT?) will be presented in an additional file including XRF data from the Avaatech XRF core scanner in a txt.file as well as datasets of the other used devices in original file formats.
# 2
Niemeijer, Andre
Abstract: The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65–75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures.Friction was substantially lower for low-velocity shearing (V<0.3 μm/s) at 600°C, but no transition to normal stress independence was observed. In the framework of rate-and-state friction, earthquake nucleation is most likely at an intermediate temperature of T = 300°C. The velocity-strengthening nature of the Alpine Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions. The data is provided in a .zip folder with 33 subfolders for 33 samples. Detailed information about the files in these subdfolders as well as sensors used, conversions and data specifications is given in the explanatory file Niemeijer-2017-DFDP-explanation-of-folder-structure-and-file-list.pdf.
# 3
Williams, Jack • Toy, Virginia • Massiot, Cecile • McNamara, David
Abstract: The orientations and densities of fractures in the foliated hanging-wall of the Alpine Fault provide insights into the role of a mechanical anisotropy in upper crustal deformation, and the extent to which existing models of fault zone structure can be applied to active plate-boundary faults. Three datasets were used to quantify fracture damage at different distances from the Alpine Fault principal slip zones (PSZs): (1) X-ray computed tomography (CT) images of drill-core collected within 25 m of the PSZs during the first phase of the Deep Fault Drilling Project that were reoriented with respect to borehole televiewer (BHTV) images, (2) field measurements from creek sections at <500 m from the PSZs, and (3) CT images of oriented drill-core collected during the Amethyst Hydro Project at distances of ~500-1400 m from the PSZs. Results show that within 160 m of the PSZs in foliated cataclasites and ultramylonites, gouge-filled fractures exhibit a wide range of orientations. At these distances, fractures are interpreted to form at high confining pressures and/or in rocks that have a weak mechanical anisotropy. Conversley, at distances greater than 160 m from the PSZs, fractures are typically open and subparallel to the mylonitic foliation or schistosity, implying that fracturing occurred at low confining pressures and/or in rocks that are mechanically anisotropic. Fracture density is similar across the ~500 m width of the hanging-wall datasets, indicating that the Alpine Fault does not have a typical “damage zone” defined by decreasing fracture density with distance. Instead, we conclude that the ~160 m-wide zone of intensive gouge-filled fractures provides the best estimate for the width of brittle fault-related damage. This estimate is similar to the 60-200 m wide Alpine Fault low-velocity zone detected through fault zone guided waves, indicating that a majority of its brittle damage occurs within its hanging-wall. The data provided here include CT scan 'core logs' for drill-core from both boreholes of the first phase of the Deep Fault Drilling Project (DFDP-1A and DFDP-1B) and from the Amethyst Hydro Project (AHP), the code to generate 'unrolled' CT images (which is to be run on imageJ), and an overview image of the integration of unrolled DFDP-1B CT images and BHTV images (DFDP-1B_BHTV-CT-Intergration.pdf). The header for the scan log images indicate 'core run-core section-upper depth-lower depth' for DFDP and 'borehole-core run-core section-upper depth-lower depth' for AHP boreholes. CT scan core logs cover the depth range 67.5-91.1 m in DFDP-1A drill-core and all of DFDP-1B drill-core. A classification of fracture type is given in Williams et al (2016). For DFDP-1 CT scan logs, title of each page labelled by: core run - core section - depth range. For AHP CT scan log, header of each page gives: borehole - core run - core section - depth. These are supplementary material to Williams et al. (submitted), in which a methodology for matching unrolled CT and BHTV images is given in Appendix A.
# 4
Mills, Steven • Williams, Jack
Abstract: This code (nwrap.ijm) can be used to generate an 'unrolled' circumferential image of a tomographic drill-core scan, such as an X-ray Computed Tomography (CT) scan. The resulting image is analogous to those produced by a DMT CoreScan system®. By comparing such images to geographically references borehole televiewer data, it may be used to reorientate drill-core back into geographic space (Williams et al. submitted). This code should be installed and run as a plugin on ImageJ/Fiji. Full instructions are given in the code and in the Appendix A of Williams et al. (submitted). Examples of unrolled CT scans can be found at Williams et al (2017, http://doi.org/10.5880/ICDP.5052.004).
# 5
Toy, Virginia • Sutherland, Rupert • Townend, John • Allen, Michael • Beecroft, Leeza • (et. al.)
Abstract: These data are supplementary material to “Bedrock Geology of DFDP-2B, Central Alpine Fault, New Zealand” (Toy et al., 2017, http://doi.org/10.1080/00288306.2017.1375533). The data tables SF3 and SF4 are provided as well as Excel as well as CSV and PDF versions (in the zip folder). The table numbers below are referring to Toy et al. (2017): Toy_SF1.pdf (Data Description): Supplementary Data to “Bedrock Geology of DFDP-2B, Central Alpine Fault, New Zealand”, including supplementary methods, Information on reference frames and corrections, and protocols for thin section preparation and scanning electron microscopic analyses. Toy_SF2: Table S1. Time vs. depth during drilling, with lag dip corrections Toy_SF3: Table S2. Energy dispersive spectroscopy (EDS) data acquired using a TESCAN Integrated Mineral Analyzer (TIMA) and phases detected by mineral liberation analysis (MLA) Toy_SF4: Table S3. Electron backscatter diffraction (EBSD) grain sizes.
# 6
Fagel, Natalie • Alleman, Laurent • Granina, L • Hatert, F • Thamo-Boszo, Edit • (et. al.)
Abstract: In order to get a complete geochemical signature, 14 P-rich concretions, chosen among the different cores, were acid digested (Table 3a and Table 3b). In a clean laboratory, 1.7 to 36 mg of concretions were digested overnight in a concentrated mixture of Suprapur acid (3 ml HCl/2 ml HNO3/1 ml HF) at 90 °C in sealed Teflon beakers. After evaporation to dryness, the residue was dissolved in 2.5 ml of 2% HNO3 Suprapur and diluted to 12 ml with Milli-Q water. During the same procedure, we have also dissolved and analysed, for comparison, a pure vivianite from Anlua, Cameroon (tubular crystals, MRAC collection).
# 7
KTB, WG Geochemistry
Abstract: The qualitative and quantitative phase analyses were performed in the KTB field laboratory by x-ray powder diffraction using SIEMENS D 500 diffractometer. During early stages of the KTB project a new method for quantitative phase analysis was developed (see references below). The method is based on the comparison of the diffraction spectrum of the unknown sample with those of pure minerals. The powder diffraction data of the minerals are stored in a database built up of 250 natural minerals separated from various types of igneous and metamorphic rocks. The complete analyses (radiation: Cu K alpha, lambda: 1,5405Å, stepwidth: 0,01°, counting time 2 sec/step, angle 2-80°) was carried out automatically including computations. The results of this quantitative phase analysis were used e.g. to check thin section petrography (and vice versa) and to construct a \"mineralogical rock composition log\".
# 8
Swann, George • Mackay, Anson • Leng, Melanie • Demory, Francois
Abstract: C/N mass ratios remain constant throughout MIS 3 and into MIS 2, with values between 6.3 and 8.9, indicating no significant terrestrial input of organic matter (Fig. 3). Low %TOC values during the interstadial increase from 0.4 to 0.7 between 57.8 and 43.7 kyr BP with a concurrent gradual increase in δ13C(organic) amid oscillations between −23.2‰ and −26.1‰ (Fig. 3). %TOC falls to 0.4 between 40.9 and 39.4 kyr BP whereas δ13C(organic) remains high at c. 24‰ with a peak value of −23.6‰ at 39.4 kyr BP. The subsequent two-stage increase in %TOC from 39 to 37.9 kyr BP and between 37.3 and 36.9 kyr BP is marked by a period of δ13C(organic) lowering to c. −26.6‰ before δ13C(organic) increases after 37.9 kyr BP to −24.8‰, values comparable to those prior to the %TOC decline at 40.9 kyr BP.
# 9
Demory, Francois • Oberhänsli, Hedi • Nowaczyk, Norbert • Gottschalk, Matthias • Wirth, Richard • (et. al.)
Abstract: No significant HIRM change is observed at the transition between oxidising and reducing conditions in the sediment (Fig. 9A). This implies that HIRM is not affected by redox conditions and further confirms that the “hard” magnetic mineral content is the best tracer of detrital input (Peck et al., 1994). On the other hand, the S-ratio seems to be related to the redox conditions in the sediment (see Section 7.2). The ARM has also to be considered with caution as it is mainly influenced by the ferrimagnetic contribution, which is itself influenced by post depositional processes. This is seen in Fig. 9 where ARM variations are partly influenced by S-ratio variations.
# 10
Swann, George • Mackay, Anson • Leng, Melanie • Demory, Francois
Abstract: All diatoms in the analysed section were extensively affected by dissolution with only c. 1% of valves in a “pristine” condition. Diatom concentrations were generally extremely low throughout MIS 3 and across the MIS 3/2 transition with samples containing a mixture of extant and extinct species (Fig. 4).
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