The Importance of Eurekan Mountains on Cenozoic Sediment Routing on the Western Barents Shelf

The importance of topography generated by Eocene Eurekan deformation as a sediment source for sandstones deposited on the western Barents Shelf margin is evaluated through a sediment provenance study conducted on wellbore materials retrieved from Spitsbergen and from the Vestbakken Volcanic Province and the Sørvestsnaget Basin in the southwest Barents Sea. A variety of complementary techniques record a provenance change across the Paleocene-Eocene boundary in wellbore BH 10-2008, which samples Paleogene strata of the Central Tertiary Basin in Spitsbergen. Sandstones containing K-feldspar with radiogenic Pb isotopic compositions, chrome spinel in the heavy mineral assemblage, and detrital zircons and rutiles with prominent Palaeoproterozoic and Late Palaeozoic—Early Mesozoic U-Pb age populations are up-section replaced by sandstone containing albitic plagioclase feldspar, metasedimentary schist rock fragments, a heavy mineral assemblage with abundant chloritoid, metamorphic apatite with low REE contents, metapelitic rutile with Silurian U-Pb ages and zircons with predominantly Archaean and Palaeoproterozoic U-Pb age populations. Our results clearly demonstrate the well-known regional change in source area from an exposed Barents Shelf terrain east of the Central Tertiary Basin during the Paleocene to the emerging Eurekan mountains west and north of the Central Tertiary Basin during the Eocene. Eocene sandstones deposited in the marginal basins of the southwestern Barents Shelf, which were sampled in wellbores 7316/5-1 and 7216/11-1S, contain elements of both the Eurekan and the eastern Barents Shelf provenance signatures. The mixing of the two sand types and delivery to the southwest margin of the Barents Shelf is consistent with a fill and spill model for the Central Teritary Basin, with transport of Eurekan-derived sediment east then south hundreds of kilometres across the Shelf

Multi-scale formation evaluation of tight gas resources

Tight unconventional rocks have become an increasingly common target for hydrocarbon production. Exploitation of these resources requires a comprehensive reservoir description and characterization program to accurately estimate reserves and identify properties which control production. In particular this requires mapping the porosity at multiple scales and understanding the coupled contributions of fractures, variable pore types, microporosity and mineral heterogeneity to petrophysical response and reserves assessment. This paper describes the application of a formation characterization study based on the integrated analysis of data in 2D and 3D at multiple scales on plugs from two sets of unconventional tight gas samples. Heterogeneity and geological rock typing is considered at the core scale via classical 3D imaging techniques. Mineralogy and secondary microporosity characterization is mapped at the plug scale with different modes of 3D X-ray micro-CT analysis coupled with SEM and SEM-EDS analysis. In particular the pore connectivity and production potential is probed. FIBSEM imaging can then used to reveal the porous microstructure of the key phases at the nano-scale. This information, collected at multiple scales, is integrated to provide an understanding and quantification of the pore structure and connectivity of these complex rocks. Petrophysical properties which impact the storage capacity and production characteristics are then computed for each key phase and data up-scaled to the plug scale using standard procedures. Results compare favourably with available core analysis data. The methodology illustrates the value of integrating conventional geological rock typing with plug/core scale petrophysical characterization to better understand rock properties characteristic of heterogeneous "unconventional" resources

Ultrafast Phase Mapping of Thin-Sections from An Apollo 16 Drive Tube - a New Visualisation of Lunar Regolith

Polished thin-sections of samples extracted from Apollo drive tubes provide unique insights into the structure of the Moon's regolith at various landing sites. In particular, they allow the mineralogy and texture of the regolith to be studied as a function of depth. Much has been written about such thin-sections based on optical, SEM and EPMA studies, in terms of their essential petrographic features, but there has been little attempt to quantify these aspects from a spatial perspective. In this study, we report the findings of experimental analysis of two thin-sections (64002, 6019, depth range 5.0 - 8.0 cm & 64001, 6031, depth range 50.0 - 53.1 cm), from a single Apollo 16 drive tube using QEMSCAN . A key feature of the method is phase identification by ultrafast energy dispersive x-ray mapping on a pixel-by-pixel basis. By selecting pixel resolutions ranging from 1 - 5 microns, typically 8,500,000 individual measurement points can be collected on a thin-section. The results we present include false colour digital images of both thin-sections. From these images, information such as phase proportions (major, minor and trace phases), particle textures, packing densities, and particle geometries, has been quantified. Parameters such as porosity and average phase density, which are of geomechanical interest, can also be calculated automatically. This study is part of an on-going investigation into spatial variation of lunar regolith and NASA's ISRU Lunar Simulant Development Project

Analysis of Lunar Highland Regolith Samples from Apollo 16 Drive Core 64001/2 and Lunar Regolith Simulants - An Expanding Comparative Database

We present modal data from QEMSCAN(registered TradeMark) beam analysis of Apollo 16 samples from drive core 64001/2. The analyzed lunar samples are thin sections 64002,6019 (5.0-8.0 cm depth) and 64001,6031 (50.0-53.1 cm depth) and sieved grain mounts 64002,262 and 64001,374 from depths corresponding to the thin sections, respectively. We also analyzed lunar highland regolith simulants NU-LHT-1M, -2M, and OB-1, low-Ti mare simulants JSC-1, -lA, -1AF, and FJS-1, and high-Ti mare simulant MLS-1. The preliminary results comprise the beginning of an internally consistent database of lunar regolith and regolith simulant mineral and glass information. This database, combined with previous and concurrent studies on phase chemistry, bulk chemistry, and with data on particle shape and size distribution, will serve to guide lunar scientists and engineers in choosing simulants for their applications. These results are modal% by phase rather than by particle type, so they are not directly comparable to most previously published lunar data that report lithic fragments, monomineralic particles, agglutinates, etc. Of the highland simulants, 08-1 has an integrated modal composition closer than NU-LHT-1M to that of the 64001/2 samples, However, this and other studies show that NU-LHT-1M and -2M have minor and trace mineral (e.g., Fe-Ti oxides and phosphates) populations and mineral and glass chemistry closer to these lunar samples. The finest fractions (0-20 microns) in the sieved lunar samples are enriched in glass relative to the integrated compositions by approx.30% for 64002,262 and approx.15% for 64001,374. Plagioclase, pyroxene, and olivine are depleted in these finest fractions. This could be important to lunar dust mitigation efforts and astronaut health - none of the analyzed simulants show this trend. Contrary to previously reported modal analyses of monomineralic grains in lunar regolith, these area% modal analyses do not show a systematic increase in plagiociase/pyroxene as size fraction decreases

New Insights into the Composition and Texture of Lunar Regolith Using Ultrafast Automated Electron-Beam Analysis

Sieved grain mounts of Apollo 16 drive tube samples have been examined using QEMSCAN - an innovative electron beam technology. By combining multiple energy-dispersive X-ray detectors, fully automated control, and off-line image processing, to produce digital mineral maps of particles exposed on polished surfaces, the result is an unprecedented quantity of mineralogical and petrographic data, on a particle-by-particle basis. Experimental analysis of four size fractions (500-250 microns, 150-90 microns, 75-45 microns and < 20 microns), prepared from two samples (64002,374 and 64002,262), has produced a robust and uniform dataset which allows for the quantification of mineralogy; texture; particle shape, size and density; and the digital classification of distinct particle types in each measured sample. These preliminary data show that there is a decrease in plagioclase modal content and an opposing increase in glass modal content, with decreasing particle size. These findings, together with data on trace phases (metals, sulphides, phosphates, and oxides), provide not only new insights into the make-up of lunar regolith at the Apollo 16 landing site, but also key physical parameters which can be used to design lunar simulants, and compute Figures of Merit for each material produced

Comparability of heavy mineral data – the first interlaboratory round robin test

Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore, standard methods used in evaluation of round robin tests are not feasible. In our case the ‘true’ compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses following multiple, pragmatic and robust criteria. The range of these three values is taken as best approximation of the ‘true’ composition. The reported grain percentages were evaluated according to (i) their overall scatter relative to the most likely composition, (ii) the number of identified components that were part of the test samples, (iii) the total amount of mistakenly identified mineral grains that were actually not added to the samples, and (iv) the number of major components, which match the reference values with 95% confidence. Results indicate that the overall comparability of the analyses is reasonable. However, there are several issues with respect to methods and/or operators. Optical methods yield the poorest results with respect to the scatter of the data. This, however, is not considered inherent to the method as demonstrated by a significant number of optical analyses fulfilling the criteria for the best-match average. Training of the operators is thus considered paramount for optical analyses. Electron-beam methods yield satisfactory results, but problems in the identification of polymorphs and the discrimination of chain silicates are evident. Labs refining their electron-beam results by optical analysis practically tackle this issue. Raman methods yield the best results as indicated by the highest number of major components correctly quantified with 95% confidence and the fact that all laboratories and operators fulfil the criteria for the best-match average. However, a number of problems must be solved before the full potential of the automated high-throughput techniques in heavy mineral analysis can be achieved