Fluid evolution along the Patterson Lake corridor in the southwestern Athabasca Basin: constraints from fluid inclusions and implications for unconformity-related uranium mineralization

2021 ◽  
pp. geochem2020-029
Author(s):  
M. Rabiei ◽  
G. Chi ◽  
E.G. Potter ◽  
V. Tschirhart ◽  
C. MacKay ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Fluid Pressure ◽  
Uranium Deposits ◽  
Hydrothermal Conditions ◽  
Content Type ◽  
Athabasca Basin ◽  
Link Type ◽  
Basement Faults ◽  
Supplementary Material

The Patterson Lake corridor (PLC) in the southwestern margin of the Athabasca Basin hosts several high-grade uranium deposits. These deposits are located in the basement up to 900 m below the unconformity surface, raising questions about their affiliation with typical unconformity-related uranium (URU) deposits elsewhere in the basin. Based on cross-cutting relationships four pre- and three syn- to post-mineralization quartz generations were identified. Fluid inclusion analyses indicate that pre-mineralization fluids have salinities ranging from 0.2 to 27.2 Wt% NaCl equiv. (avg. 9.0 Wt%), whereas syn-mineralization fluids have salinities ranging from 8.8 to 33.8 Wt% NaCl + CaCl2 (avg. 25.4 Wt%), with NaCl- and CaCl2-rich varieties. The homogenization temperatures (Th) of fluid inclusions from pre-mineralization quartz range from 80 ° to 244 ℃ (avg. 147 ℃), and from syn-mineralization quartz range from 64 ° to 248 ℃ (avg. 128 ℃). Fluid boiling is indicated by the co-development of liquid-dominated and vapor-dominated fluid inclusions within individual fluid inclusion assemblages (FIA) from the syn-mineralization quartz and is related to episodic fluid pressure drops caused by reactivation of basement faults. Our results indicate that composition and P-T conditions of the ore fluids in the PLC are comparable to those of typical URU deposits in the Athabasca Basin, indicating that the uranium deposits in the PLC formed under similar hydrothermal conditions. Episodic reactivation of basement faults was an important driving force to draw uraniferous fluids from the basin and reducing fluids from the basement to the mineralization sites, forming deep basement-hosted deposits.Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathwaysSupplementary material:https://doi.org/10.6084/m9.figshare.c.5510179

Fluid flow and syntectonic veining in an Ediacaran-Cambrian foreland fold–thrust zone, western margin of the São Francisco Craton, Brazil

2021 ◽  
pp. jgs2020-061
Author(s):  
Melina C. B. Esteves ◽  
Frederico M. Faleiros
Keyword(s):  
Fluid Flow ◽  
Fluid Inclusion ◽  
Analytical Data ◽  
Microstructural Analysis ◽  
Fluid Pressure ◽  
Content Type ◽  
Western Margin ◽  
Metasedimentary Rocks ◽  
Supplementary Material ◽  
Fault Valve

The western margin of the São Francisco Craton, central Brazil presents a 1300 km long foreland fold–thrust belt where Ediacaran-Cambrian (560–520 Ma) metasedimentary rocks from the Bambuí Group were subsequently deformed during post-collisional stages (520–495 Ma) related to Gondwana assembly. This scenario provides an opportunity to quantify fluid flow regimes and fault-related processes that were active in exhumed foreland fold–thrust zones, which were estimated based on structural, microstructural and fluid inclusion studies of syntectonic veins and host rocks. Kaolinite-bearing synkinematic mineral assemblages from metasedimentary rocks, thermodynamic models and grain-scale deformation accommodated by dissolution–precipitation creep and intracrystalline deformation indicate metamorphic and deformational conditions of 250–270°C. Subhorizontal extensional veins formed under subhorizontal shortening and subvertical extension, supporting vein development under a fold–thrust regime that formed regional NW–SE-trending thrust fault zones and megafolds with NW–SE-trending axes. Orientation and growth microstructures indicate that NW–SE-trending subvertical cleavage-parallel veins formed under subhorizontal NE–SW extension, compatible with those inferred to produce mapped kilometre-scale gentle folds with NE–SW-trending traces. Two primary aqueous fluid inclusion assemblages (FIA) are distinguished by salinity variation: 2–21 wt% NaCleq. in subhorizontal veins and 6–0 wt% NaCleq. in cleavage-parallel subvertical veins. Fluid inclusion thermometry and microstructural analysis suggest that veins crystallized between 250 and 270°C under fluid pressure fluctuating within a range of 50–500 MPa (subhorizontal veins) and 80–320 MPa (cleavage-parallel subvertical veins), evidencing fault-valve behaviour. Trends of coupled decreases in salinity and homogenization temperatures in both FIA indicate downward mixing of meteoric fluids, which was more effective in subvertical veins and was in both cases enhanced by fault-valve behaviour. Dominance of moderate salinity and absence of CO2 and CH4 indicate that the fluids are dominated by formation waters. The salinity signature is similar to those of formation waters and metamorphic fluids derived from rocks of shallow marine environments worldwide.Supplementary material: Details of samples and analytical data are available at https://doi.org/10.6084/m9.figshare.c.5275031

scholarly journals Evolution of a sand-rich submarine channel-lobe system and impact of mass-transport and transitional flow deposits on reservoir heterogeneity: Magnus Field, northern North Sea

2021 ◽  
pp. petgeo2020-095
Author(s):  
Michael J. Steventon ◽  
Christopher A-L. Jackson ◽  
Howard D. Johnson ◽  
David M. Hodgson ◽  
Sean Kelly ◽  
...  
Keyword(s):  
Mass Transport ◽  
North Sea ◽  
Fluid Pressure ◽  
Transitional Flow ◽  
Rock Properties ◽  
Sweep Efficiency ◽  
Content Type ◽  
Supplementary Material ◽  
Northern North Sea ◽  
The Impact

The geometry, distribution, and rock properties (i.e. porosity and permeability) of turbidite reservoirs, and the processes associated with turbidity current deposition, are relatively well known. However, less attention has been given to the equivalent properties resulting from laminar sediment gravity-flow deposition, with most research limited to cogenetic turbidite-debrites (i.e. transitional flow deposits) or subsurface studies that focus predominantly on seismic-scale mass-transport deposits (MTDs). Thus, we have a limited understanding of the ability of sub-seismic MTDs to act as hydraulic seals and their effect on hydrocarbon production, and/or carbon storage. We investigate the gap between seismically resolvable and sub-seismic MTDs, and transitional flow deposits on long-term reservoir performance in this analysis of a small (<10 km radius submarine fan system), Late Jurassic, sandstone-rich stacked turbidite reservoir (Magnus Field, northern North Sea). We use core, petrophysical logs, pore fluid pressure, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), and 3D seismic-reflection datasets to quantify the type and distribution of sedimentary facies and rock properties. Our analysis is supported by a relatively long (c. 37 years) and well-documented production history. We recognise a range of sediment gravity deposits: (i) thick-/thin- bedded, structureless and structured turbidite sandstone, constituting the primary productive reservoir facies (c. porosity = 22%, permeability = 500 mD), (ii) a range of transitional flow deposits, and (iii) heterogeneous mud-rich sandstones interpreted as debrites (c. porosity = <10%, volume of clay = 35%, up to 18 m thick). Results from this study show that over the production timescale of the Magnus Field, debrites act as barriers, compartmentalising the reservoir into two parts (upper and lower reservoir), and transitional flow deposits act as baffles, impacting sweep efficiency during production. Prediction of the rock properties of laminar and transitional flow deposits, and their effect on reservoir distribution, has important implications for: (i) exploration play concepts, particularly in predicting the seal potential of MTDs, (ii) pore pressure prediction within turbidite reservoirs, and (iii) the impact of transitional flow deposits on reservoir quality and sweep efficiency.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5313860

scholarly journals Environmental variability in response to abrupt climatic change during the Last Glacial–Interglacial Transition (16–8 cal ka BP): evidence from Mainland, Orkney

2019 ◽  
Vol 56 (1) ◽  
pp. 30-46 ◽  
Author(s):  
Ashley M. Abrook ◽  
Ian P. Matthews ◽  
Alice M. Milner ◽  
Ian Candy ◽  
Adrian P. Palmer ◽  
...  
Keyword(s):  
Early Career ◽  
Early Holocene ◽  
Content Type ◽  
Last Glacial ◽  
Principal Curve ◽  
Link Type ◽  
Supplementary Material ◽  
Career Research ◽  
The Last Glacial ◽  
Millennial Scale

The Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene.Supplementary material: All raw data associated with this publication: raw pollen counts, charcoal data, Principal Curve and Rate of Change outputs and the age-model output are available at https://doi.org/10.6084/m9.figshare.c.4725269Thematic collection: This article is part of the ‘Early Career Research’ available at: https://www.lyellcollection.org/cc/SJG-early-career-research

scholarly journals The naming of the Permian System

2021 ◽  
pp. jgs2021-037
Author(s):  
Michael J. Benton ◽  
Andrey G. Sennikov
Keyword(s):  
System Level ◽  
Naming Time ◽  
Content Type ◽  
Red Sandstone ◽  
Link Type ◽  
Permian System ◽  
Urgent Task ◽  
Great Leader ◽  
Supplementary Material ◽  
Access To Documents

The naming of the Permian by Roderick Murchison in 1841 is well known. This is partly because he ‘completed’ the stratigraphic column at system level, but also because of the exotic aspects of his extended fieldwork in remote parts of Russia and Murchison's reputed character. Here, we explore several debated and controversial aspects of this act, benefiting from access to documents and reports notably from Russian sources. Murchison or Sedgwick could have provided a name for the unnamed lower New Red Sandstone in 1835 based on British successions or those in Germany, so perhaps the Imperial aim of naming time from British geology was not the urgent task some have assumed. Murchison has been painted as arrogant and Imperialistic, which was doubtless true, but at the time many saw him as a great leader, even an attractive individual. Others suggest he succeeded because he stood on the shoulders of local geologists; however, his abilities at brilliant and rapid geological synthesis are undoubted. Two unexpected consequences of his work are that this arch conservative is revered in Russia as a hero of geological endeavours, and, for all his bombast, his ‘Permian’ was not widely accepted until 100 years after its naming.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5412079

scholarly journals Dating protracted fault activities: microstructures, microchemistry and geochronology of the Vaikrita Thrust, Main Central Thrust zone, Garhwal Himalaya, NW India

2018 ◽  
Vol 481 (1) ◽  
pp. 127-146 ◽  
Author(s):  
Chiara Montemagni ◽  
Chiara Montomoli ◽  
Salvatore Iaccarino ◽  
Rodolfo Carosi ◽  
Arvind K. Jain ◽  
...  
Keyword(s):  
Electron Microprobe ◽  
Garhwal Himalaya ◽  
Main Central Thrust ◽  
Content Type ◽  
Mylonitic Foliation ◽  
Link Type ◽  
Thrust Zone ◽  
Supplementary Material ◽  
Structural Boundary

AbstractThe timing of shearing along the Vaikrita Thrust, the upper structural boundary of the Main Central Thrust Zone in the Garhwal Himalaya, was constrained by combined microstructural, microchemical and geochronological investigations. Three different biotite–muscovite growth and recrystallization episodes were observed: a relict mica-1; mica-2 along the main mylonitic foliation; and mica-3 in coronitic structures around garnet during its breakdown. Electron microprobe analyses of biotite showed chloritization and a bimodal composition of biotite-2 in one sample. Muscovite-2 and muscovite-3 differed in composition from each other. Biotite and muscovite 39Ar–40Ar age spectra from all samples showed both inter- and intra-sample discrepancies. Biotite step-ages ranged between 8.6 and 16 Ma and muscovite step-ages between 3.6 and 7.8 Ma. These ages cannot be interpreted as ‘cooling ages’ because samples from the same outcrop cooled simultaneously. Instead, the Ar systematics reflect sample-specific recrystallization markers. Intergrown impurities were diagnosed by the Ca/K ratios. The age data of biotite were interpreted as a mixture of true biotite-2 (9.00 ± 0.10 Ma) and two alteration products. The negative Cl/K–age correlation identified a Cl-poor muscovite-2 (>7 Ma) and a Cl-rich, post-deformational, coronitic muscovite-3 grown at ≤5.88 ± 0.03 Ma. The Vaikrita Thrust was active at least from 9 to 6 Ma at c. 600°C; its movement had ended by 6 Ma.Supplementary material: Thermometric and 39Ar–40Ar data are available at https://doi.org/10.6084/m9.figshare.c.4069076

Palaeolatitudinal distribution of the Ediacaran macrobiota

2021 ◽  
pp. jgs2021-030
Author(s):  
Catherine E. Boddy ◽  
Emily G. Mitchell ◽  
Andrew Merdith ◽  
Alexander G. Liu
Keyword(s):  
Taxonomic Composition ◽  
Supplementary Information ◽  
Cambrian Explosion ◽  
Content Type ◽  
Link Type ◽  
Environmental Perturbations ◽  
Significant Difference ◽  
Evolutionary Trajectories ◽  
Cambrian Radiation ◽  
Supplementary Material

Macrofossils of the late Ediacaran Period (c. 579–539 Ma) document diverse, complex multicellular eukaryotes, including early animals, prior to the Cambrian radiation of metazoan phyla. To investigate the relationships between environmental perturbations, biotic responses and early metazoan evolutionary trajectories, it is vital to distinguish between evolutionary and ecological controls on the global distribution of Ediacaran macrofossils. The contributions of temporal, palaeoenvironmental and lithological factors in shaping the observed variations in assemblage taxonomic composition between Ediacaran macrofossil sites are widely discussed, but the role of palaeogeography remains ambiguous. Here we investigate the influence of palaeolatitude on the spatial distribution of Ediacaran macrobiota through the late Ediacaran Period using two leading palaeogeographical reconstructions. We find that overall generic diversity was distributed across all palaeolatitudes. Among specific groups, the distributions of candidate ‘Bilateral’ and Frondomorph taxa exhibit weakly statistically significant and statistically significant differences between low and high palaeolatitudes within our favoured palaeogeographical reconstruction, respectively, whereas Algal, Tubular, Soft-bodied and Biomineralizing taxa show no significant difference. The recognition of statistically significant palaeolatitudinal differences in the distribution of certain morphogroups highlights the importance of considering palaeolatitudinal influences when interrogating trends in Ediacaran taxon distributions.Supplementary material: Supplementary information, data and code are available at https://doi.org/10.6084/m9.figshare.c.5488945Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion

Diamondiferous lamproites of Ingashi field, Siberian craton

2021 ◽  
pp. SP513-2020-274
Author(s):  
S. I. Kostrovitsky ◽  
D. A. Yakovlev ◽  
I. S. Sharygin ◽  
D. P. Gladkochub ◽  
T. V. Donskaya ◽  
...  
Keyword(s):  
Trace Element ◽  
Siberian Craton ◽  
Major Elements ◽  
Primary Sources ◽  
Content Type ◽  
Link Type ◽  
Ultramafic Lamprophyre ◽  
Dating Methods ◽  
Supplementary Material

AbstractIngashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Russia) and the only non-kimberlitic one in the Siberian craton. Ingashi lamproite field placed in Urik-Iya graben within Prisayan uplift of Siberian craton. Phlogopite-olivine lamproites contain olivine, talc, phlogopite, serpentine, chlorite, olivine, garnet, chromite, orthopyroxene, clinopyroxene as well as Sr-F-apatite, monazite, zircon, armolcolite, priderite, potassium Mg-arfvedsonite, Mn-ilmenite, Nb-rutile, and diamond. The only one ultramafic lamprophyre dyke is composed mainly of serpentinized olivine and phlogopite in the talc-carbonate groundmass and similar (to Ingashi lamproites) accessory assemblage with the same major elements compositions. Trace element and Sr-Nd isotopic relationships of the Ingashi lamproites are similar to classic lamproites. Different dating methods have provided the ages of lamproites: 1481 Ma (Ar-Ar phlogopite), 1268 Ma (Rb-Sr whole rock) and 300 Ma (U-Pb zircon). Ingashi lamproite ages are controversial and require additional study. Calculated pressure of 3.5 GPamax for clinopyroxenes indicating that lamproite magma originated deeper than 100 km. Cr-in-garnet barometer (Grutter et al., 2006) shows a 3.7-4.3 GPamin and derivation of Ingashi lamproites deeper than 120 km depth. Based on the range of typical cratonic geotherms and presence of diamonds, the Ingashi lamproite magma originated at a depth greater than 155 km.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5493128

Lead, zinc and arsenic contamination of pit lake waters in the Zeida abandoned mine (High Moulouya, Morocco)

2021 ◽  
pp. geochem2021-009
Author(s):  
Lamiae EL ALAOUI ◽  
Abdelilah Dekayir ◽  
Mohammed Rouai ◽  
EL Mehdi Benyassine
Keyword(s):  
Organic Matter ◽  
Iron Oxides ◽  
Environmental Issues ◽  
Abandoned Mine ◽  
Equal Proportion ◽  
Pit Lake ◽  
Content Type ◽  
Link Type ◽  
Supplementary Material ◽  
Lake Waters

In the Zeida abandoned mine, pit lake waters exhibit alkaline pH and high conductivity. The concentrations of the total dissolved lead and zinc are very low due to their adsorption on clay minerals and iron oxyhydroxides. Conversely, arsenic concentrations in two lakes (ZL1 and ZA) exceeded WHO water quality guidelines. The As content is relatively high in ZL1 lake and exists mainly as As(V). In ZA lake, As(III) occurs in low concentration compared to the total dissolved arsenic, while dimethylarsenic acid [H2AsO2(CH3)2, DMA) prevails. This means that arsenic was methylated by organic matter produced by microorganisms such as chlorella. The sequential extraction of floor sediments in two lakes shows that the bioavailable arsenic contents change between the two lakes. In ZA lake, the sediments show high concentrations of lead and arsenic compared to ZL1 sediment since it is surrounded by mining waste tailings, which are rich in such chemical elements. An arsenic leaching test of ZA sediment shows that bioavailable arsenic is distributed in equal proportion between clay/carbonates, sulfide-organic matter, and iron oxides (HFO) phases, while in ZL1, most of the arsenic is linked to hydrous iron oxides (HFO).Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issuesSupplementary material:https://doi.org/10.6084/m9.figshare.c.5545316

scholarly journals The nature and origins of decametre-scale porosity in Ordovician carbonate rocks, Halahatang oilfield, Tarim Basin, China

2020 ◽  
Vol 177 (5) ◽  
pp. 1074-1091
Author(s):  
Estibalitz Ukar ◽  
Vinyet Baqués ◽  
Stephen E. Laubach ◽  
Randall Marrett
Keyword(s):  
Tarim Basin ◽  
Velocity Gradient ◽  
Fractured Reservoirs ◽  
Gradient Tensor ◽  
Fault Rocks ◽  
Content Type ◽  
Velocity Gradient Tensor ◽  
Link Type ◽  
Isotopic Analyses ◽  
Supplementary Material

At >7 km depths in the Tarim Basin, hydrocarbon reservoirs in Ordovician rocks of the Yijianfang Formation contain large cavities (c. 10 m or more), vugs, fractures and porous fault rocks. Although some Yijianfang Formation outcrops contain shallow (formed near surface) palaeokarst features, cores from the Halahatang oilfield lack penetrative palaeokarst evidence. Outcrop palaeokarst cavities and opening-mode fractures are mostly mineral filled but some show evidence of secondary dissolution and fault rocks are locally highly (c. 30%) porous. Cores contain textural evidence of repeated formation of dissolution cavities and subsequent filling by cement. Calcite isotopic analyses indicate depths between c. 220 and 2000 m. Correlation of core and image logs shows abundant cement-filled vugs associated with decametre-scale fractured zones with open cavities that host hydrocarbons. A Sm–Nd isochron age of 400 ± 37 Ma for fracture-filling fluorite indicates that cavities in core formed and were partially cemented prior to the Carboniferous, predating Permian oil emplacement. Repeated creation and filling of vugs, timing constraints and the association of vugs with large cavities suggest dissolution related to fractures and faults. In the current high-strain-rate regime, corroborated by velocity gradient tensor analysis of global positioning system (GPS) data, rapid horizontal extension could promote connection of porous and/or solution-enlarged fault rock, fractures and cavities.Supplementary material: Stable isotopic analyses and the velocity gradient tensor and principal direction and magnitude calculation are available at https://doi.org/10.6084/m9.figshare.c.4946046Thematic collection: This article is part of the The Geology of Fractured Reservoirs collection available at: https://www.lyellcollection.org/cc/the-geology-of-fractured-reservoirs

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