Academic literature on the topic 'Hyaloclasite'

Hyaloclastites commonly form high-quality reservoir rocks in volcanic geothermal provinces. Here, we investigated the effects of confinement due to burial following prolonged accumulation of eruptive products on the physical and mechanical evolution of surficial and subsurface (depths of 70 m, 556 m, and 732 m) hyaloclastites from Krafla volcano, Iceland. Upon loading in a hydrostatic cell, the porosity and permeability of the surficial hyaloclastite decreased linearly with mean effective stress, as pores and cracks closed due to elastic (recoverable) compaction up to 22-24 MPa (equivalent to ~1.3 km depth in the reservoir). Beyond this mean effective stress, denoted as P∗, we observed accelerated porosity and permeability reduction with increasing confinement, as the rock underwent permanent inelastic compaction. In comparison, the porosity and permeability of the subsurface core samples were less sensitive to mean effective stress, decreasing linearly with increasing confinement as the samples compacted elastically within the conditions tested (to 40 MPa). Although the surficial material underwent permanent, destructive compaction, it maintained higher porosity and permeability than the subsurface hyaloclastites throughout the experiments. We constrained the evolution of yield curves of the hyaloclastites, subjected to different effective mean stresses in a triaxial press. Surficial hyaloclastites underwent a brittle-ductile transition at an effective mean stress of ~10.5 MPa, and peak strength (differential stress) reached 13 MPa. When loaded to effective mean stresses of 33 and 40 MPa, the rocks compacted, producing new yield curves with a brittle-ductile transition at ~12.5 and ~19 MPa, respectively, but showed limited strength increase. In comparison, the subsurface samples were found to be much stronger, displaying higher strengths and brittle-ductile transitions at higher effective mean stresses (i.e., 37.5 MPa for 70 m sample, >75 MPa for 556 m, and 68.5 MPa for 732 m) that correspond to their lower porosities and permeabilities. Thus, we conclude that compaction upon burial alone is insufficient to explain the physical and mechanical properties of the subsurface hyaloclastites present in the reservoir at Krafla volcano. Mineralogical alteration, quantified using SEM-EDS, is invoked to explain the further reduction of porosity and increase in strength of the hyaloclastite in the active geothermal system at Krafla.

In the present work, we demonstrate how drone surveys coupled with structure-from-motion (SfM) photogrammetry can help to collect huge amounts of very detailed data even in rough terrains where logistics can affect classical field surveys. The area of study is located in the NW part of the Krafla Fissure Swarm (NE Iceland), a volcanotectonic rift composed of eruptive centres, extension fractures, and normal faults. The surveyed sector is characterized by the presence of a hyaloclastite ridge composed of deposits dated, on a stratigraphic basis, to the Weichselian High Glacial (29.1–12.1 ka BP), and a series of lava flows mostly dating back to 11–12 ka BP. The integration of remotely sensed surveys and field inspections enabled us to recognize that this segment of the Krafla rift is made of grabens arranged en-échelon with a left-stepping geometry. A major graben increases in width in correspondence of the hyaloclastite cone; we interpret this geometry as resulting from the mechanical contrast between the stiffer lava succession and the softer hyaloclastites, which favours the development of concentric faults. We also measured a total extension of 16.6 m and 11.2 m along the fractures affecting the lava units, and a total extension in the hyaloclastites of 29.3 m. This produces an extension rate of 1.4 mm/yr in the Holocene lavas and 1.7 ± 0.7 mm/yr in the Weichselian hyaloclastite deposits. The spreading direction we obtained for this area is N97.7° E, resulting from the av. of 568 opening direction values.

The pyrite nodules from ore diagenites of the Urals massive sulfide deposits associated with various background sedimentary rocks are studied using optical and electron microscopy and LA-ICP-MS analysis. The nodules are found in sulfide–black shale, sulfide–carbonate–hyaloclastite, and sulfide–serpentinite diagenites of the Saf’yanovskoe, Talgan, and Dergamysh deposits, respectively. The nodules consist of the core made up of early diagenetic fine-crystalline (grained) pyrite and the rim (±intermediate zone) composed of late diagenetic coarse-crystalline pyrite. The nodules are replaced by authigenic sphalerite, chalcopyrite, galena, and fahlores (Saf’yanovskoe), sphalerite, chalcopyrite and galena (Talgan), and pyrrhotite and chalcopyrite (Dergamysh). They exhibit specific accessory mineral assemblages with dominant galena and fahlores, various tellurides and Co–Ni sulfoarsenides in sulfide-black shale, sulfide–hyaloclastite–carbonate, and sulfide-serpentinite diagenites, respectively. The core of nodules is enriched in trace elements in contrast to the rim. The nodules from sulfide–black shale diagenites are enriched in most trace elements due to their effective sorption by associated organic-rich sediments. The nodules from sulfide–carbonate–hyaloclastite diagenites are rich in elements sourced from seawater, hyaloclastites and copper–zinc ore clasts. The nodules from sulfide–serpentinite diagenites are rich in Co and Ni, which are typical trace elements of ultramafic rocks and primary ores from the deposit.

AbstractSubglacially erupted Neogene basaltic hyaloclastites in lava-fed deltas in Antarctica were found to contain putative endolithic microborings preserved in fresh glass along hydrous alteration boundaries. The location and existence over the past 6 Ma of these lava deltas has exposed them to successive interglacials and subsequent percolation of the hyaloclastite with marine water. A statistical study of the hyaloclastites has found that endolithic microborings are distinctly more abundant within samples that show evidence for marine alteration, compared with those that have remained in a strictly freshwater (glacial) environment. Additionally, correlation between elevation and the abundance of microborings shows endolithic activity to be more prolific within lower elevation samples, where the hyaloclastites were influenced by marine fluids. Our study strongly suggests that endolithic microborings form more readily in marine-influenced, rather than freshwater environments. Indeed, marine fluids may be a necessary precondition for the microbial activity responsible. Thus, we suggest that the chemistry and origin of alteration fluids are controlling factors on the formation of endolithic microborings in basaltic glass. The study also contributes to the understanding of how endolithic microborings could be used as a biosignature on Mars, where basaltic lavas and aqueous alteration are known to have existed in the past.

AbstractMassive to lobate volcanic flows and brecciated hyaloclastite units in the Abitibi greenstone belt allow investigation of Late Archæan seafloor alteration and associated incorporation into these rocks of nitrogen (N) biogeochemical signatures. In this suite (the Blake River Group), hyaloclastite units containing putative microbial ichnofossils are particularly enriched in large-ion lithophile elements (K, Rb, Ba, Cs), B, and Li, consistent with their having experienced the greatest fluid–rock interaction during subseafloor hydrothermal alteration. Similarly, silicate-δ18O and δ15N values for samples from the hyaloclastites show the greatest shifts from plausible magmatic values. The chemical and isotopic patterns in these tholeiitic igneous rocks greatly resemble those in modern altered seafloor basalts, consistent with the preservation of an Archæan seafloor alteration signature. The N enrichments and shifts in δ15N appear to reflect stabilization of illite and interaction with fluids carrying sedimentary/organic signatures. Enrichments of N (and the δ15N of this N) in altered glass volcanic rocks on Earth's modern and ancient seafloor point to the potential utility of N for tracing past and present biogeochemical processes in similar rocks at/near the Mars surface.

Geothermal fields are prone to temperature fluctuations from natural hydrothermal activity, anthropogenic drilling practices, and magmatic intrusions. These fluctuations may elicit a response from the rocks in terms of their mineralogical, physical (i.e., porosity and permeability), and mechanical properties. Hyaloclastites are a highly variable volcaniclastic rock predominantly formed of glass clasts that are produced during nonexplosive quench-induced fragmentation, in both subaqueous and subglacial eruptive environments. They are common in high-latitude geothermal fields as both weak, highly permeable reservoir rocks and compacted impermeable cap rocks. Basaltic glass is altered through interactions with external water into a clay-dominated matrix, termed palagonite, which acts to cement the bulk rock. The abundant, hydrous phyllosilicate minerals within the palagonite can dehydrate at elevated temperatures, potentially resulting in thermal liability of the bulk rock. Using surficial samples collected from Krafla, northeast Iceland, and a range of petrographic, mineralogical, and mechanical analyses, we find that smectite dehydration occurs at temperatures commonly experienced within geothermal fields. Dehydration events at 130, 185, and 600°C result in progressive mass loss and contraction. This evolution results in a positive correlation between treatment temperature, porosity gain, and permeability increase. Gas permeability measured at 1 MPa confining pressure shows a 3-fold increase following thermal treatment at 600°C. Furthermore, strength measurements show that brittle failure is dependent on porosity and therefore the degree of thermal treatment. Following thermal treatment at 600°C, the indirect tensile strength, uniaxial compressive strength, and triaxial compressive strength (at 5 MPa confining pressure) decrease by up to 68% (1.1 MPa), 63% (7.3 MPa), and 25% (7.9 MPa), respectively. These results are compared with hyaloclastite taken from several depths within the Krafla reservoir, through which the palagonite transitions from smectite- to chlorite-dominated. We discuss how temperature-induced changes to the geomechanical properties of hyaloclastite may impact fluid flow in hydrothermal reservoirs and consider the potential implications for hyaloclastite-hosted intrusions. Ultimately, we show that phyllosilicate-bearing rocks are susceptible to temperature fluctuations in geothermal fields.

AbstractThe failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 109 m3 of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 105 m3 s−1 for the Hyaloclastite outburst flood. This discharge is an order of magnitude greater than the largest known discharge on the Colorado River (1.4 × 104 m3 s−1) and the largest peak discharge resulting from failure of a constructed dam in the USA (6.5 × 104 m3 s−1). Moreover, the Hyaloclastite outburst flood is the oldest documented Quaternary flood and one of the largest to have occurred in the continental USA. The peak discharge for this flood ranks in the top 30 floods (>105 m3 s−1) known worldwide and in the top ten largest floods in North America.

Hydrocarbon gases were monitored in the drilling fluid during deepening of the Lopra-1 well from 2178–3565 m, in which thermogenic, methane-rich gases had been found previously. The mud gas concentration, up to 105 ppm of methane, was generally higher in the hyaloclastite sequence, 2470 m – terminal depth (TD), than in the overlying lavas of the lower basalt formation. The highest concentrations of mud gas in the lower basalt formation were associated with the more porous tuffaceous zones, whereas no simple relationship could be established between measured mud gas concentrations and porosity of the hyaloclastic rocks, which showed less marked porosity variations than the lavas. Chemical (C2+ < 1%) and isotopic (δ13C1: –34 to –39‰) compositions of seven samples of mud gas collected at peak gas concentrations between 2657 m and 3442 m compare well with those of the hydrocarbon gases which had been seeping more or less continuously into the existing well since 1983, suggesting a common origin of the gases. Headspace methane concentrations measured in 135 canned samples of cuttings were scattered between 10 ppm and 6 × 103 ppm, with the exception of six samples from a short interval, 2685– 2745 m, which showed consistently high values > 104 ppm. No particularly gas-rich zones were indicated, however, by the mud gas, nor was any significant change in lithology noted for this interval. It is possible that the technique of turbo-drilling, that had been attempted over a short interval, 2657– 2675 m prior to collection of the high-level methane samples, may have caused enhanced degassing due to the very fine cuttings produced. Chemical and isotopic composition of headspace gas and mud gas indicated the same type of gas throughout the well, although headspace methane tended to be more enriched with respect to the 13C isotope. The origin of the Lopra-1 gas is discussed in the light of recent information obtained from source rock studies of central East Greenland and the Faroe–Shetland Basin.

Geotechnical investigations undertaken by GHD Pty Ltd uncovered a previously undescribed rock type in the suburbs of Footscray and Alphington approximately 5 km west and 6.5 km east of Melbourne CBD respectively. The rock encountered appeared to be a breccia type rock with angular high strength fine gravel to boulder sized fragments of relatively unweathered grey to dark grey basalt surrounded by a matrix of orangish brown fine grained brittle material resembling hard clay. Pillow basalts were also encountered in the deposits in the form of 0.6 m or larger globular but highly fractured basalt bodies within the rock mass. The rock was eventually identified as a hyaloclastite, a rock type formed when basalt lava flows into water bodies and is quench fragmented. The debris forms piles of basalt and volcanic glass fragments. The volcanic glass fragments are thermodynamically unstable and are altered to palagonite within as little as 20 years from initial deposition. No prior reference to the occurrence of hyaloclastite in the Melbourne region could be found. As such, the location, extent and geotechnical properties of this rock type are unknown, posing a potential risk to infrastructure and construction projects. This study aimed to investigate the possible origins of the hyaloclastite; develop a theory of emplacement/origin; identify other locations where this rock type may exist; determine the geotechnical properties and engineering geological behaviour of the rock; and develop a classification system for the rocks encountered. A variety of methods were used to gather sufficient information to allow the occurrences and geological and geotechnical nature of hyaloclastites and pillow basalts in the Melbourne area to be better understood. Samples of the rock were obtained during the geotechnical investigations undertaken in Footscray and Alphington and outcrop mapping was completed on exposures identified during the course of this study. Historical borehole logs and as built drawings were obtained to assist in the understanding of the previous description terminology associated with the rock now identified as hyaloclastite. Standard and “non-standard” laboratory testing was undertaken as well as classification testing. The field of block-in-matrix rocks “bimrocks” was assessed as a possible method to assist in the understanding of the behaviour and geotechnical properties of the hyaloclastite rock with or without pillow basalts. The RMR, Q-System and GSI rock mass classification systems were used to help understand the rockmass characteristics. A weak rock classification system, a weathered rock characterisation system and a ground behaviour characterisation system were also used to provide information on the possible behaviour of the hyaloclastite type rocks. Development of both 2D and 3D geological models of the two sites indicate that the hyaloclastites encountered in Melbourne were deposited in “lava-deltas”. The hyaloclastites were deposited on advancing subaqueous delta fronts with an overlying layer of subaerial basalt above what has been termed the “passage zone” which represents the historical level of water into which the lava flowed. Strength testing undertaken on the various samples suggested that the hyaloclastite should be classified as a weak rock, with UCS values of ranging from approximately 1 MPa to 10 MPa, and a median UCS value of 1.37 MPa. Using the compiled UCS data and PLT data an estimate of the PLT Is50 to UCS conversion factor “k” was calculated as 10.4. The results of jar slake testing and weatherability index testing were variable: whilst the majority of samples showed no sign of slaking, one sample showed a strong reaction. The samples of disaggregated rock were classified as sandy gravel as per AS1726:1995. Whilst the fine to medium gravel was of subangular grains of basalt the sand was found to be made up of angular fragments of palagonite. Plasticity index and XRD testing of fines obtained from the disaggregation process indicated that the fines are comprised of illite and smectite clay minerals and behave as a high plasticity silt. Several categorisation methods utilised indicated that the hyaloclastite type rockmass strength parameters are controlled partly by the strength of the matrix and partly by the discontinuities and that the rock mass strength is dominated by the pillow basalt behaviour (typical hard rock type behaviours) only once the content of these structures in these rocks exceeds a volume content of 75% pillows to 25% hyaloclastite. Rock mass strength and deformation calculations indicate that the hyaloclastite rock mass is both very weak and also highly deformable (rock mass modulus <100 MPa) when compared with the highly weathered subaerial basalt (~500 MPa) and the fresh/slightly weathered basalt (~15000 MPa). A value of petrographic constant mi used in the Generalised Hoek Brown Criterion was also determined to be 7.01. This is considerably different to the values suggested for “breccia” in the literature of 19±8. A modulus ratio of 150 was also estimated using testing data from Melbourne and also Iceland. The extent of hyaloclastite in the Melbourne region remains unknown. Whilst the location of these deposits is associated with the base of palaeovalleys now infilled by volcanic products, hyaloclastite does not occur in the base of all the palaeovalleys and is expected to be controlled by sea level change and also disruption of drainage lines by damming caused by earlier subaerial flows. Geotechnical practitioners must be aware of the potential occurrence of hyaloclastite as both the hyaloclastite and hyaloclastites with pillow basalt rock masses were found to be significantly weaker and more deformable than the highly weathered subaerial basalt rock. Misidentification of the rock as highly weathered basalt during geotechnical investigation may result in significant under-design. In addition, rock mass behaviour categorisation indicates that block-falls of pillow basalt from excavation walls and roofs may be a risk. Increased excavation effort to remove the pillow basalt structures should also be factored in to projects. To aid identification and understanding of the potential hazards associated with hyaloclastite type rocks, a series of reference sheets has been developed. These reference sheets aim to increase practitioners’ knowledge of hyaloclastites, and the implications for excavation and construction. The reference sheets also provide geomechanical details. Three-dimensional simplified engineering geological block models have also been included to provide graphical information on the relationships and possible geohazards of the various rock types. Future research should aim to further define the extent and engineering properties of hyaloclastites in the Melbourne region and to further define the petrographic constant mi, a better estimate of modulus ratio based on instrumented UCS tests. It is also hoped that now this rock has been recognised in Melbourne that the geotechnical community will reassess previous projects and start to build knowledge on the whereabouts of hyaloclastite and pillow basalt type rocks in the Melbourne area.

This thesis aims to document hyaloclastite deposits in different depositional environments from field outcrops in Iceland to characterise lithofacies heterogeneity enabling comparison to subsurface datasets. Field hyaloclastite datasets from Stóri-Núpur (subaerial-marine transition) and Hjörleifshöfði (an emergent Surtseyan volcano) are used to support the interpretation of hyaloclastite and associated volcanic deposits in core, borehole image logs and wire-line log datasets from Hawaii (Hawaiian Scientific Drilling Project II – HSDP II borehole) and the Faroe-Shetland Basin (LOPRA1/1A well and the Rosebank field). This study provides additional constraints on lava delta formation in predominantly basaltic systems where hyaloclastite depositional profiles reflect localised extrusion pathways and syn-sediment reworking which control 3D lithofacies architecture. Furthermore this thesis documents the evolution of Hjörleifshöfði using field mapping and major/trace element geochemistry. Hjörleifshöfði can split into five phases of deposition charting the submarine to emergent building of the volcano, unique as it also records a phase of silicic volcanism (Sólheimar Ignimbrite) which dates late stage volcanism to no earlier than 12,383 C14 years BP. Petrophysical and petrographic observations suggest hyaloclastite deposits are unique in terms of their velocity/density and P and S wave relationships due to palagonite formation, basalt clast support, phenocryst and zeolite component amongst others which impacts on depth conversion and the calculation of reflection coefficients. Wire-line log response gamma-ray (GR), resistivity (RES), P-wave sonic velocity (Vp) is also closely linked to the dominant interstitial secondary minerals and phenocryst components of sideromelane glass. Borehole image log analysis of mixed volcanic and volcaniclastic rocks allows the accurate characterisation of distinct internal lava flow features, contact relationships and joint networks enabling better characterisation of volcanic sequences in the subsurface via careful comparison with field examples. Field, core and wire-line log data is combined to form a multidisciplinary assessment of hyaloclastite deposits in the subsurface suggesting that the complexity and scaling issues in hyaloclastite rocks is generally overlooked which may impact on future petroleum exploration in volcanic basins.

L'Ile de La Réunion est un système océanique volcanique dont l'essentiel du volume est immergé. Sa structure interne est investiguée par approches géophysiques, gravimétrique, magnétique et électromagnétique, offrant un modèle du système à grande échelle. La couverture gravimétrique du Piton de la Fournaise permet de distinguer les sources superficielles et profondes. Des variations gravimétriques associées à l'effondrement du Dolomieu en 2007 sont étudiées en termes de déplacements de masse au sein de l'édifice. Le Piton des Neiges apparaît comme un immense volcan organisé autour d'un système hypovolcanique de grande extension. La corrélation entre sa morphologie et la topographie suggère une relation entre la subsidence du complexe et celle des dépressions sus-jacentes. La couverture de formations récentes, incomplète, présente des épaisseurs variables et permet de reconstruire la morphologie de l'île à la transition Brunhes-Matuyama. A l'échelle du système immergé, la morphologie de deux larges zones de constructions volcaniques anciennes est proposée, à l'E et au SO de l'île, remettant en question les interprétations sismiques. La morphologie générale de l'édifice construit est reconstituée. Le plateau côtier est interprété en termes d'accumulation de hyaloclastites et de pillow lavas. Les quatre excroissances sous-marines sont principalement composées d'accumulation de dépôts d'avalanches de débris, dont les contrastes internes de densité peuvent être corrélés avec certaines unités géologiques observées en surface. Une étude comparative entre l'édifice de La Réunion et d'autres îles océaniques met en lumière les analogies et dissemblances morphologiques, structurales et géophysiques entre différents systèmes volcaniques océaniques.

La singularité volcanologique de l’Islande réside dans les interactions entre magmas et glaciers, conduisant à la mise en place d’édifices sous-glaciaires de type tuya ou ride de hyaloclastites. Les datations K-Ar et Ar-Ar testent l’hypothèse d’un lien éventuel entre la décompression intervenant en période de déglaciation et l’augmentation des taux de fusion partielle, conduisant à une production magmatique accrue.

Lithological facies classification using well logs is essential in the reservoir characterization. The facies are manually classified from characteristic log responses derived, which is challenging and time consuming for geologically complex reservoirs due to high variation of log responses for each facies. To overcome such a challenge, machine learning (ML) is helpful to determine characteristic log responses. In this study, we classified the lithofacies by applying ML to the conventional well logs for the volcanic formation, onshore, northeast Japan. The volcanic formation of the Yurihara oil field is petrologically classified into five lithofacies: mudstone, hyaloclastite, pillow lava, sheet lava, and dolerite, with pillow lava being predominant reservoir. The former four lithofacies are the members of the volcanic system in Miocene, and dolerite randomly intruded later into those. Understanding the distribution of omnidirectional tight dykes at the well location is important for the estimation of potential near-lateral seal distribution compartmentalizing the reservoir. The facies are best classified by core data, which are unfortunately available in a limited number of wells. The conventional logs, with the help of the borehole image log, have been used for the facies classification in most of the wells. However, distinguishing dolerite from sheet lava by manual classification is very ambiguous, as they appear similar in these logs. Therefore, automated clustering of well logs with ML was attempted for the facies classification. All the available log data was audited in the target well prior to applying ML. A total of 10 well logs are available in the reservoir depth interval. To prioritize the logs for the clustering, the information of each log was first analyzed by Principal Component Analysis (PCA). The dimension of variable space was reduced from 10 to 5 using PCA. Final set of 5 variables, gamma-ray, density, formation photoelectric factor, neutron porosity, and laterolog resistivity, were used for the next clustering process. ML was applied to the selected 5 logs for automated clustering. Cross-Entropy Clustering (CEC) was first initialized using k-means++ algorithm. Multiple initialization processes were randomly conducted to find the global minimum of cost function, which automatically derived the optimized number of classes. The resulting classes were further refined by the Gaussian Mixture Model (GMM) and subsequently by the Hidden Markov Model (HMM), which takes the serial dependency of the classes between successive depths into account. Resulting 14 classes were manually merged into 5 classes referring to the lithofacies defined by the borehole image log analysis. The difference of the log responses between basaltic sheet lava and dolerite was too subtle to be captured with confidence by the conventional manual workflow, while the ML technique could successfully capture it. The result was verified by the petrological analyses on sidewall cores (SWCs) and cuttings. In this study, the automated clustering with the combination of several ML algorithms was demonstrated more efficient and reasonable facies classification. The unsupervised learning approach would provide supportive information to reveal the regional facies distribution when it is applied in the other wells, and to comprehend the dynamic behavior of the fluids in the reservoir.