Standard Rocks Research Articles

A new spectral analysis method for determining the joint roughness coefficient of rock joints

We propose a new spectral analysis method for accurate JRC determination. To do this, we first propose an average power index Pf to present the amplitude height of a rock joint profile, which considers both the low and high-frequency components of the profile. Secondly, the modified root mean square of the first deviation of the profile (Z2*) is adopted to better capture the effects of shear direction and the inclination angle of the profile on the rock joint's roughness. Finally, we propose a new roughness parameter, PZ, which combines the Pf and the Z2*; the PZ considers the shear direction, the inclination angle and the amplitude height of a rock joint profile simultaneously. We derived correlations with upper, suggested, and lower bounds between JRC and PZ using 102 rock joint profiles at the sampling interval of 0.4 mm, and compared them with Barton's 10 standard rock joint profiles. We analyzed five sandstone joints from the field to validate the proposed method: Both laser scanning and direct shear tests were conducted on the sandstone joints. Comparing the peak shear strength obtained from experimental tests, the proposed method, and the Z2 method, verified that the proposed method can determine the JRC accurately. In addition, the shear direction influence and sampling interval effect on the rock joint roughness were discussed. The correlations between JRC and PZ were also derived at the sampling intervals of 0.8 mm and 1.2 mm.

On the Features of Sorption Concentration of Ru on Super-Crosslinked Polystyrenes during the Analysis of Rocks by the Method of Inductively Coupled Plasma Mass Spectrometry

New sorption systems based on a series of super-crosslinked polystyrenes of brands HP and Styrosorb for the concentration of Ru from the solutions obtained after decomposition of rocks are studied. To extract Ru according to a reversed-phase mechanism, aromatic amines (methylbenzylamine (MBA), dimethylbenzylamine (DMBA), dibenzylmethylamine (DBMA)), as well as aliphatic tributylamine (TBA), are used for the first time. It is shown that reverse 60% extraction of Ru from the standardized test solution can be reached in the Styrosorb-514–TBA–1M HCl sorption system in ethanol as a desorption agent. An important role of sample preparation of a solid sample is revealed by the analysis of the reference standards (RSs) of ultrabasic and basic rocks. It is found that, for the quantitative (100%) extraction of Ru in the selected sorption system, the only suitable way of transferring a solid sample to a solution is smelting to NiS matte followed by dissolving of the matte in aqua regia and transferring it to concentrated HCl. The influence of Ni during the mass spectrometric determination of Ru by 99Ru in a broad range of concentrations (20–2000 μg/L) is studied; it is shown that the presence of Ni does not make the Ru concentration too high. The conducted experiments have displayed the possibility for using the sorption system based on Styrosorb-514 when estimating the low content of Ru in rock samples, which is confirmed by the analysis of the reference standards of ultrabasic and basic rocks GPt-5, GPt-6, and SARM-7. The obtained data on Ru content in these objects coincide with the certified values within the confidence interval.

Methodical peculiarities of preparation of solid geological samples for multi-element analysis by ICP-MS

The technique of decomposition of samples with a hardly soluble complex matrix (sintering with soda) for subsequent determination of trace element composition by high-resolution mass spectrometry with inductively coupled plasma is improved and tested. Analytical and methodological problems arising in the process of preparation of the samples under analysis for analysis are described, directions for their solution are indicated. The correctness of the developed sample preparation procedure has been verified by means of a comparative analysis of various methods applied to international certified standard rock samples.

Improved protactinium spike calibration method applied to 231Pa–235U age-dating of certified reference materials for nuclear forensics

The application of multiple radiochronometers in a forensic investigation of bulk uranium provides increased confidence for interpreting age-dating results. We have developed a streamlined method for the purification of Pa and Th from bulk uranium and have applied this method in analyzing uranium certified reference materials (CRMs) IRMM-1000 and CRM U100, using the 231Pa–235U and 230Th–234U radiochronometers. Our improved 233Pa spike calibration technique has replaced the time-intensive, conventional calibration using geologic rock standards. Paired Pa–U and Th–U age-dating analyses of CRM U100 produce concordant results. In contrast, analyses of IRMM-1000 demonstrate reproducibly-discordant Th–U and Pa–U age-dates.

Research in using Polyurethane Foam to Mitigate Rock Bolt Installation Difficulties

Rock bolts are commonly used on transportation projects to stabilize cut slopes, reinforce undermined or unsupported blocks, and reduce potential for large rock slides. Installing bolts can be challenging. Locations where bolts are useful may not be easily accessible for personnel or large equipment, and targeted blocks generally are marginally stable. In addition, jointed rock with openings and voids, which are typical conditions, complicate hole advancement and full grout encapsulation. These issues can lead to construction delays, claims, reduced corrosion protection, or shorter design life. This paper describes research conducted to address two rock bolting challenges in open-jointed rock: i) advancement of drill holes to design depth, and ii) successful completion of grouting through the application of injected polyurethane foam (PUF). Testing utilized double-stacked concrete blocks aligned in rows to simulate a rock mass with vertical fractures. Steel spacers were placed between the stacks to simulate 2-, 4-, 6-, and 8-inch apertures. A standard rock drill advanced holes using a 3-inch bit. Research showed PUF could: bridge simulated aperture sizes up to 8 inches, survive drilling action during secondary reaming, resist drilling air and grouting pressures, and reduce grout consumption.

Unusual layered order and charge disproportionation in the double-perovskite compound Ca2FeMnO6

While double perovskites A2BB'O6, if ordered, usually form a rock-salt-type structure with a checkerboard B/B' ordering, it is surprising that Ca2FeMnO6 has alternate FeO2 and MnO2 layers in its perovskite structure. Here we demonstrate, using density functional calculations, that this unusual layered ordering facilitates, and is largely helped by, the Fe3+-Fe5+ charge disproportionation (CD) of the formal Fe4+ ions, which would otherwise be frustrated in the common rock salt structure. To further verify the important role of the CD for stabilization of this layered ordering, we carry out a comparative study for the isostructural Ca2TiMnO6 which has a simple Ti4+-Mn4+ state free of the CD. Our calculations indicate that Ca2TiMnO6 instead prefers the standard rock salt structure to the layered one. Thus our study shows a nontrivial interplay between the CD and the type of ion ordering, and proves that the CD is strongly involved in stabilizing the unusual layered order of Ca2FeMnO6.

Influence of moisture content on the LCPC test results and its implications on tool wear in mechanized tunneling

Various testing methods have been proposed to measure rock abrasiveness as an input into the prediction models for estimating the tool wear in mechanized tunneling and mining. Among the proposed tests, LCPC test has been used by many researchers for assessment of rock abrasivity. In this study, 20 rock samples from various locations in Pakistan were subjected to comprehensive testing of various properties. The tests included LCPC (Laboratorie Central des Ponts et Chaussees) rock abrasivity tests as well as a complete suite of standard rock physical and mechanical property tests. Whilst the standard LCPC test is run in dry samples, this study compared the results of the LCPC method in dry and saturated conditions, performed at water contents of 15, 30, 45 and 60%. Overall abrasivity [measured as ABR (g/t)] decreased with the increase in water content with peak values of ABR (g/t) attained at 15% water contents for low porosity rocks and 30% water content for high porosity rocks when compared to dry tests. Similarly, a gradual decrease in the LCPC Breakability Index (BR%) was noted in the case of low porosity rocks with the corresponding increase in water content. However, for high porosity rocks there was a cyclic fall and rise in breakability (BR%) at 15% and 30% moisture levels, respectively. This was in contrast to dry tests. A steady drop in BR% was also observed at higher water contents. This paper discusses the result of the testing as well as practical implications of these measurements on predicted wear of cutting tools used in mechanized excavation in mining and tunneling applications. Preliminary statistical analysis of the data and correlations between ABR, water contents, and petrographic and engineering rock properties are also included in this paper.

Reservoir characteristics of the Kuhlan sandstones from Habban oilfield in the Sabatayn Basin, Yemen and their relevance to reservoir rock quality and petroleum accumulation

Integrated petrophysical and petrographic analyses were performed on the Kuhlan clastic rocks to evaluate the petrophysical reservoir properties, identify grain sorting along with the clay type and mineral volumes using well logs coupled with core data. Core samples were collected from two key wells and their results were used to determine the reservoir properties and bulk mineralogical composition and, additionally, to calibrate the well log results from three un-cored to the two cored wells.The Kuhlan clastic reservoir rocks have porosity values between 6% and 12%. These porosity values are mainly intergranular primary and secondary porosity. Permeability is likewise variable with values in the range of 78–304 mD. The Kuhlan reservoir rocks also have high hydrocarbon saturation exceeding 70%, with relatively high movable oil. These reservoir properties are achieved from log-derived and core porosity and permeability results.The lithology and mineral composition of the well logs and petrographic studies in this study indicate that the Kuhlan sandstone can be considered as an alternative reservoir rock in the basin. The Kuhlan Formation is primarily composed of sandstone that contains quartz, feldspar (i.e., orthoclase, plagioclase (albite) minerals and illite, and calcite cements. The quartz mineral is dominant followed by feldspar as the second most abundant mineral in this formation. The Kuhlan Formation sandstones are classified (based on standard rock classification schemes) into arkose, sub-arkose and feldspathic lithofacies. The results of petrographic analysis also indicate a continental block transitional source of the Kuhlan Formation sandstones. Petrographically, the Kuhlan sandstones are poorly sorted and range from fine to coarse-grained and contain high percentages of detrital quartz and feldspar-rich grains with a significant amount of rock fragments. The Kuhlan sandstones also contain a variable range of matrix and cement contents.Based on the results of this study, the reservoir quality of the Kuhlan sandstone ranges between good to poor reservoir quality. The Kuhlan Formation has arkosic and sub-arkosic sandstones that result in a good reservoir quality with a significant increase of the permeability and intergranular porosity. This is attributed to the coarse-grained texture, high percentages of detrital quartz, slightly well sorted texture and the low degree of matrix and cements. In contrast, the Kuhlan Formation feldspathic sandstone has poor reservoir quality due to the poor sorting texture, pore space occluding clayey groundmass, and carbonate cement.

High-precision analysis of potassium isotopes by HR-MC-ICPMS

This study presents a method for high-precision stable potassium (K) isotope analysis using High-Resolution Multi-Collector Inductively Coupled Plasma Mass Spectrometry (HR-MC-ICPMS). Dry and cold plasma is used to suppress the formation of argon hydrides that are direct isobaric interferences on K isotopes. The residual 40Ar1H+ beam is resolved from 41K+ by using pseudo-high resolution mode, providing interference-free shoulders of 39K+ and 41K+ for isotopic measurements. Precision of better than 0.06‰ (95% confidence interval) has been routinely achieved based on multiple measurements of pure K standard solutions and rock standards over a six-month period. Mismatches in K concentration (up to 20%) and acid molarity (up to 67%) between samples and bracketing standards, as well as the presence of substantial amount of matrix element Rb, do not significantly affect the analytical precision and accuracy. Our study documents that high-precision K isotope analysis can be routinely achieved for a wide variety of natural samples by HR-MC-ICPMS, which makes it possible for using K isotopes to trace major geological processes.

Er, Yb, and Hf isotopic compositions of refractory inclusions: An integrated isotopic fingerprint of the Solar System's earliest reservoir

The oldest dated solids in our Solar System, calcium–aluminum-rich inclusions (CAIs), contain isotopic anomalies in a whole suite of elements relative to later formed Solar System materials. Previous work has reported differences in the proportions of nucleosynthetic components between CAIs and terrestrial rocks as a function of mass. However, the nucleosynthetic fingerprint of the CAI-forming region is still lacking significant data in the heavier mass range (A > 154). Therefore, we present the first erbium (Er) and ytterbium (Yb) isotopic data along with hafnium (Hf) isotopic compositions in a wide variety of CAIs derived from a variety of CV and CK chondrites. This work presents new methods for Er and Yb isotopic investigation that were explored using both thermal ionization mass spectrometry (TIMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Relative to terrestrial rock standards, CAIs—regardless of host rock, petrologic or chemical classification—have uniform and resolvable Er, Yb, and Hf isotopic compositions. The CAI isotopic patterns correspond to r-process deficits (or s-process excesses) relative to terrestrial values of 9 ppm for Er, 18 ppm for Yb, and 17 ppm for Hf. This new Er, Yb, and Hf data help complete the nucleosynthetic fingerprint of the CAI-forming region, further highlighting the systematic difference between the CAIs and later formed bulk planetary bodies. Such a systematic difference between CAIs and terrestrial rocks cannot be caused by different amounts of any known single presolar phase but is likely the result of a well-mixed reservoir made of diverse stellar sources.

No 182W excess in the Ontong Java Plateau source

Small-scale W isotope variations in ancient and modern terrestrial rocks provide insights into Earth's accretion and early differentiation history as well as the long-term evolution of the Earth's mantle. Tungsten isotope studies on such rocks have exploited advances in mass spectrometry, both NTIMS and MC-ICPMS, which now permit the determination of W isotope ratios at unprecedented precision. While W isotope studies performed in different labs by MC-ICPMS and NTIMS generally exhibit excellent agreement, obtaining accurate W isotope data at this level of precision remains analytically challenging. For example, a recent NTIMS study reported a relatively large, +24 ppm excess in 182W/184W for a Phanerozoic sample from the Ontong Java Plateau (OJP), but no such 182W/184W anomaly was found in another study by MC-ICPMS. The present study aims to resolve the discrepancy between these two previous studies, and more generally to evaluate the agreement between different recent W isotope studies by NTIMS and MC-ICPMS. To this end, we report new W isotope data for OJP drill core samples obtained by MC-ICPMS. The OJP samples analyzed here exhibit no resolvable 182W/184W excess relative to the standards and most terrestrial rocks. Moreover, the OJP samples as well as the terrestrial rock standards analyzed here exhibit small but variable W isotope variations for ratios involving 183W, producing coupled variations in both ‘radiogenic’ (i.e., 182W/183W) and ‘non-radiogenic’ (i.e., 183W/184W) ratios. These W isotope variations are analytical in origin, induced during sample preparation, and very likely caused by a nuclear field shift isotope fractionation affecting primarily the odd isotope (183W). The recently reported 182W excess for an OJP sample may result from this nuclear field shift effect, as the NTIMS analyses had to rely on a double normalization involving the 183W/184W ratio. More generally, these results demonstrate that using 183W data from any MC-ICPMS or NTIMS study requires a careful quantification of any potential analytical 183W effect. Nevertheless, once such effects are taken into account, then both 182W/184W and 183W/184W can accurately be determined to a very high level of precision.

Isotopic coherence of refractory inclusions from CV and CK meteorites: Evidence from multiple isotope systems

Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials in the Solar System and numerous previous studies have revealed nucleosynthetic anomalies relative to terrestrial rock standards in many isotopic systems. However, most of the isotopic data from CAIs has been limited to the Allende meteorite and a handful of other CV3 chondrites. To better constrain the isotopic composition of the CAI-forming region, we report the first Sr, Mo, Ba, Nd, and Sm isotopic compositions of two CAIs hosted in the CK3 desert meteorites NWA 4964 and NWA 6254 along with two CAIs from the CV3 desert meteorites NWA 6619 and NWA 6991. After consideration of neutron capture processes and the effects of hot-desert weathering, the Sr, Mo, Ba, Nd, and Sm stable isotopic compositions of the samples show clearly resolvable nucleosynthetic anomalies that are in agreement with previous results from Allende and other CV meteorites. The extent of neutron capture, as manifested by shifts in the observed 149Sm-150Sm isotopic composition of the CAIs is used to estimate the neutron fluence experienced by some of these samples and ranges from 8.40 × 1013 to 2.11 × 1015 n/cm2. Overall, regardless of CAI type or host meteorite, CAIs from CV and CK chondrites have similar nucleosynthetic anomalies within analytical uncertainty. We suggest the region that CV and CK CAIs formed was largely uniform with respect to Sr, Mo, Ba, Nd, and Sm isotopes when CAIs condensed and that CAIs hosted in CV and CK meteorites are derived from the same isotopic reservoir.

A novel sample loading method and protocol for monitoring sample fractionation for high precision Ca stable isotope ratio measurements using double-spike TIMS

The external reproducibility (2σSD) of Ca stable isotope ratio measurements (δ44/40Ca) using double-spike (43Ca–48Ca) thermal ionization mass spectrometry (TIMS) is better than 0.08 ‰ using our proposed loading technique.

Emulation of the Curiosity rover alpha particle X-ray spectrometer with accelerator-based PIXE: Implications for calibration

Abstract A 2.5 MeV broad-beam PIXE system was designed to emulate the alpha particle X-ray spectrometer (APXS) of the Curiosity rover. APXS measurements of the light elements (sodium, magnesium and aluminum) in powdered rock standards showed systematic deviations arising from the rock’s violation of the assumption of atomic scale sample homogeneity. These deviations, which are dependent on the iron concentration of the sample, were confirmed with high-accuracy accelerator-based PIXE measurements. Systematically low iron concentrations, not seen in APXS measurements, were present in the PIXE results. These are unlikely to arise due to violation of the homogeneity assumption. Measured particle-size distributions suggest that they are more likely due to the grain size distribution of iron-bearing minerals in the powdered standards. Terrestrial analogs to recently discovered Martian rock types were used to extend the calibration to include high iron and high-alkali samples.

Calculation of parameters of combined frame and roof bolting

The paper presents the method of calculation of the combined frame and roof bolting. Recommendations on providing joint operation of roof bolting with steel support frames are given. Graphs for determining standard rock movement, as well as for defining proof load on the yielding support, were developed.

The distribution, hydrocarbon potential, and development of the Lower Cretaceous black shales in coastal southeastern China

Lower Cretaceous black shales in coastal southeastern China are of significance to the geological study of the Tethys and Pacific realms and to hydrocarbon exploration of southeastern China and East China Sea. However, the stratigraphic correlation, distribution patterns and hydrocarbon potential of the black shales have not been well constrained so far. In this study, the zircon U–Pb ages, organic petrologic and geochemical analyses were performed for representative outcrop sections in the region. Zircon U–Pb ages demonstrate that the Lower Cretaceous black shales in coastal southeastern China can be divided into two regional-scale sets. The first set was deposited during the early stage of the Early Cretaceous (K11, Berriasian–Hauterivian). The second set was deposited during the late stage of the Early Cretaceous (K12), and might extend to the Taiwan Strait. Detailed organic geochemical analyses including organic matter abundance, type and maturity of the Lower Cretaceous black shales demonstrate that the organic matter abundance of the sources reached medium to good quality by the hydrocarbon source rock standards, and the average TOC values and the chloroform bitumen “A” of the K11 black shales are higher. The type of organic matter is mainly type III, type II can also be found from the K12 black shales. The thermal maturity of most samples is high to overmature. A relatively comprehensive hydrocarbon resource evaluation indicates that favorable regions are in the northern Guangdong Province for the K11 and in the coastal region of Zhejiang Province and the western Fujian Province for the K12. Sedimentology studies on the Shipu section for the K11 black shales illuminated that the K12 black shales in coastal southeastern China were mainly deposited during transgressive period. The relative sea level changes controlled the sequential development pattern of the K12 black shales.

Measurement of geologic nitrogen using mass spectrometry, colorimetry, and a newly adapted fluorometry technique

Abstract. Long viewed as a mostly noble, atmospheric species, recent work demonstrates that nitrogen in fact cycles throughout the Earth system, including the atmosphere, biosphere, oceans, and solid Earth. Despite this new-found behaviour, more thorough investigation of N in geologic materials is limited due to its low concentration (one to tens of parts per million) and difficulty in analysis. In addition, N can exist in multiple species (NO3−, NH4+, N2, organic N), and determining which species is actually quantified can be difficult. In rocks and minerals, NH4+ is the most stable form of N over geologic timescales. As such, techniques designed to measure NH4+ can be particularly useful.We measured a number of geochemical rock standards using three different techniques: elemental analyzer (EA) mass spectrometry, colorimetry, and fluorometry. The fluorometry approach is a novel adaptation of a technique commonly used in biologic science, applied herein to geologic NH4+. Briefly, NH4+ can be quantified by HF dissolution, neutralization, addition of a fluorescing reagent, and analysis on a standard fluorometer. We reproduce published values for several rock standards (BCR-2, BHVO-2, and G-2), especially if an additional distillation step is performed. While it is difficult to assess the quality of each method, due to lack of international geologic N standards, fluorometry appears better suited to analyzing mineral-bound NH4+ than EA mass spectrometry and is a simpler, quicker alternative to colorimetry.To demonstrate a potential application of fluorometry, we calculated a continental crust N budget based on new measurements. We used glacial tills as a proxy for upper crust and analyzed several poorly constrained rock types (volcanics, mid-crustal xenoliths) to determine that the continental crust contains ∼ 2 × 1018 kg N. This estimate is consistent with recent budget estimates and shows that fluorometry is appropriate for large-scale questions where high sample throughput is helpful.Lastly, we report the first δ15N values of six rock standards: BCR-2 (1. 05 ± 0. 4 ‰), BHVO-2 (−0. 3 ± 0. 2 ‰), G-2 (1. 23 ± 1. 32 ‰), LKSD-4 (3. 59 ± 0. 1 ‰), Till-4 (6. 33 ± 0. 1 ‰), and SY-4 (2. 13 ± 0. 5 ‰). The need for international geologic N standards is crucial for further investigation of the Earth system N cycle, and we suggest that existing rock standards may be suited to this need.

New Capabilities of Multichannel Spectrometer “Kolibri-2” for Analysis of Geological Samples

A method of sample preparation is developed for geological samples of various compositions to provide simultaneous determination of cesium and other alkali metals (Na, K, Li and Rb) on a multichannel spectrometer “Kolibri-2” using flame photometry. The lower limit of cesium determination is close to its average abundance. The procedures of sample preparation and calibrations using reference material standards (RMS)of rocks, soils, sediments and coal ash provided the following ranges of the determinable contents (% wt.): Na 0.025 - 7.4; K 0.085 - 15.0; Li 0.00025 - 0.33; Rb 0.0005 -0.15; Cs 0.0002-0.0070. The accuracy of the results for cesium is confirmed in analysis of RMS and spiking tests. The reduction of time spent for each stage of analysis compared to existing techniques increases the efficiency of the proposed flame photometric technique of determination of alkali metals on a spectrometer “Kolibri-2” and diminishes the time of the classical silicate analysis.

Method peculiarities of multielemental analysis of rocks with inductively-coupled plasma mass spectrometry

Decomposition of samples with a poorly soluble complex matrix for the analysis of the trace-element composition with high-resolution inductively-coupled plasma mass spectrometry was designed and tested. Analytical and method problems of the selection and preparation of samples are described and their solutions are proposed. The correctness of sample preparation was verified using analysis of standard rock samples.

A new method for TIMS high precision analysis of Ba and Sr isotopes for cosmochemical studies

A new protocol using Eichron™ Sr-resin for high-resolution Sr and Ba isotope measurements using thermal ionization mass spectrometry for cosmochemical samples.