Ultrasonic wave velocity, mineralogy, texture analysis, and CT Scan on samples from the Thunderbox gold mine.
Description
INTRODUCTION We report here the results of laboratory measurements conducted on rock samples extracted from the Thunderbox Gold Mine in Western Australia. Laboratory measurements consist of ultrasonic wave velocity at ambient and in-situ pressure, density, mineralogy, CT Scan image, and texture analysis. The key objectives of this work are: (i) document the values of P- and S-wave velocities across the gold mine deposit; (ii) discriminate crack-induced and texture-born anisotropy at depth (realistic confining pressure); (iii) Evaluate the feasibility of using seismic reflection as a sweet-spot indicator in the Thunderbox shear zone. 1-ROCK SAMPLES For this study, 126 cylindrical samples, 50 mm in diameter and 65 to 125 mm in length, were extracted from 16 mine drill-cores recovered at depths ranging between 100 and 450m in the Thunderbox Gold Mine. The samples were selected to represent the major lithological units encountered in the mine: basalt (39 samples), andesite (8 samples), foliated mafic volcaniclastic (15 samples), meta-sandstone (13 samples), lamprophyre (ultramafic) (6 samples), talc schist (shear zone) (4 samples), and dacite (gold host rock) (41 samples). To assess the effect of the hydrothermal alteration associated with gold deposition on the elastic properties, the dacite samples were selected with different levels of hydrothermal alteration. In addition, four samples — including two from the shear zone — were selected to evaluate the pressure and directional dependency of the P-wave velocities. 2-DATA AVAILABLE 2.1-ULTRASONIC WAVE VELOCITY Ambient conditions a) Velocity, bulk density at ambient conditions from over 100 samples. Confining pressure a) Interpreted velocity along multiple propagation directions for 4 samples (dacite, mafic volcaniclastic, and 2 talc schist) at each increment of pressure. b) Interpreted P-wave Time along multiple propagation directions for 4 samples at each increment of pressure. c) File with the geometrical configuration of the array of ultrasonic transducers used in the experiment under confining pressure. d) Raw data 2-2 CT SCAN images from 4 samples that were subjected to the confining pressure (ultrasonic wave velocity measurements) 2-3 Picture of the samples. 2-4 Neutron Diffraction measurements (texture analysis) from 2 talc schist samples (shear zone). 2-5 Mineralogy Qualitative and quantitative identification of the mineral phases from 10 samples. a) raw data; b) identified mineral phases; c) Project TOPAS used to quantify the minerals; This data was used in the paper titled "Laboratory measurements of ultrasonic wave velocities and anisotropy across a gold-hosting structure: a case study of the Thunderbox Gold Mine, Western Australia".