Fluids sources in basement-hosted unconformity-uranium ore systems: tourmaline chemistry and boron isotopes from the Patterson Lake corridor deposits, Canada

2021 ◽  
pp. geochem2021-037
Author(s):  
E.G. Potter ◽  
C.J. Kelly ◽  
W.J. Davis ◽  
G. Chi ◽  
S-Y. Jiang ◽  
...  
Keyword(s):  
Shear Zones ◽  
Isotopic Signature ◽  
Strong Interactions ◽  
Content Type ◽  
B Values ◽  
Isotopic Signatures ◽  
Link Type ◽  
Basement Rocks ◽  
Supplementary Material ◽  
Over Time

The Patterson Lake corridor is a new uranium district located on the southwestern margin of the Athabasca Basin. Known resources extend almost one kilometer below the unconformity in graphite- and sulfide-bearing shear zones within highly altered metamorphic rocks. Despite different host rocks and greater depths below the unconformity, alteration assemblages (chlorite, illite, kaolinite, tourmaline and hematite), ore grades and textures are typical of unconformity-related deposits. This alteration includes at least three generations of Mg-rich tourmaline (magnesio-foitite). The boron isotopic composition of magnesio-foitite varies with generation: the earliest generation only observed in shallow samples from the Triple R deposit (Tur 1) contain the heaviest isotopic signature (δ11B ≈ +26 to +19 ‰), whereas subsequent generations (Tur 2, Tur 3) yield lighter and more homogeneous isotopic signatures (δ11B ≈ +17.5 to +19.9 ‰). These results are consistent with precipitation from low temperature, NaCl- and CaCl2-rich brine(s) derived from an isotopically heavy boron source (e.g. evaporated seawater) that interacted with tourmaline and silicates in the basement rocks and/or fluids derived from depth (with low δ11B values). The lower δ11B values in paragenetically later magnesio-foitite reflect greater contributions of basement-derived boron over time whereas minor compositional variations reflect local metal sources (e.g. Cr, V, Ti) and evolving fluid chemistry (decreasing Na and Ca, increasing Mg) over time. The δ11B and chemical variation in magnesio-foitite over time reinforce the strong interactions with basement rocks in these systems while supporting incursion of basinal brines well below the unconformity contact.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.5727555

scholarly journals Basement reservoir plumbing: fracture aperture, length and topology analysis of the Lewisian Complex, NW Scotland

2020 ◽  
Vol 177 (6) ◽  
pp. 1281-1293 ◽  
Author(s):  
K. J. W. McCaffrey ◽  
R. E. Holdsworth ◽  
J. Pless ◽  
B. S. G. Franklin ◽  
K. Hardman
Keyword(s):  
Oil And Gas ◽  
Fractured Reservoirs ◽  
Crystalline Basement ◽  
Fracture Aperture ◽  
Power Law Distribution ◽  
Content Type ◽  
Scaling Properties ◽  
Link Type ◽  
Basement Rocks ◽  
Supplementary Material

Upfaulted ridges of Neoarchean crystalline basement rocks formed in the Faeroe-Shetland basin as a consequence of Mesozoic rift processes and are an active target for oil exploration. We carried out a comprehensive fault and fracture attribute study on the extensive exposures of geologically equivalent crystalline basement rocks onshore in NW Scotland (Lewisian Gneiss Complex) as an analogue for the offshore oil and gas reservoirs of the uplifted Rona Ridge basement high. Our analysis shows a power-law distribution for fracture sizes (aperture and length), with random to clustered spacing and high connectivity indices. Regional variations between the Scottish mainland and the Outer Hebrides are recognized that compare directly with variations observed along the Rona Ridge in the Faeroe-Shetland basin. Here we develop a model for the scaling properties of the fracture systems in which variations in the aperture attributes are a function of the depth of erosion beneath the top basement unconformity. More generally, the combination of size, spatial and connectivity attributes we found in these basement highs demonstrates that they can form highly effective, well-plumbed reservoir systems in their own right.Supplementary material: Additional methods and results are available at: https://doi.org/10.6084/m9.figshare.c.5017139Thematic 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

Geochronology of Himalayan shear zones: unravelling the timing of thrusting from structurally complex fault rocks

2021 ◽  
pp. jgs2020-235
Author(s):  
Chiara Montemagni ◽  
Igor M. Villa
Keyword(s):  
Shear Zones ◽  
Main Central Thrust ◽  
Fault Rocks ◽  
Isotopic Dating ◽  
Content Type ◽  
Link Type ◽  
Complex Fault ◽  
Thrust Zone ◽  
Supplementary Material ◽  
Average Bond

Dating structurally complex fault rocks often results in internally inconsistent ages, as several mineral generations are intergrown at scales << 10 µm and almost always altered to various degrees. Firstly, electron probe microanalysis is necessary to assess both inventory and spatial distribution of minerals and their retrogression/alteration phases. We then used 40Ar/39Ar stepheating combining two independent indicators that allow the discrimination of coexisting mica generations from each other: (i) mica stoichiometry, which is proxied by 39Ar concentration in combination with 37Ar/39Ar and 38Ar/39Ar (Ca/K and Cl/K) ratios; (ii) furnace temperature, at which the degassing peak accompanying dehydration and structural collapse is observed. As dehydration rates depend on average bond strength in the crystal structure, it is predicted and observed that the temperature of the differential Ar release peak is variable among different minerals. We observe that the Ca/Cl/K signatures of pure micas coincide with the Ar release peak. The Main Central Thrust zone in the Garhwal Himalaya records a protracted history. Foliation of Vaikrita Thrust formed at 15-8 Ma, followed by static decompression at 7 Ma; foliation of structurally lower Munsiari Thrust formed around 5 Ma. Our elaborate and time-consuming petrochronological procedure should become routine whenever analysing polydeformed metamorphic rocks.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5357212Thematic collection: This article is part of the Isotopic Dating collection available at: https://www.lyellcollection.org/cc/isotopic-dating-of-deformation

Jurassic–Cretaceous arc magmatism along the Shyok–Bangong Suture from NW Himalaya: Formation of the peri-Gondwana basement to the Ladakh Arc

2021 ◽  
pp. jgs2021-035
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Renjie Zhou
Keyword(s):  
Late Cretaceous ◽  
Nw Himalaya ◽  
Content Type ◽  
Magmatic Arc ◽  
Basement Rocks ◽  
Ladakh Himalaya ◽  
Accreted Terranes ◽  
Volcaniclastic Rocks ◽  
Supplementary Material ◽  
Depositional Age

The Jurassic–Cretaceous Tsoltak Formation from the eastern borderlands of Ladakh Himalaya consists of conglomerates, sandstones and shales, and is intruded by norite sills. It is the oldest sequence of continent-derived sedimentary rocks within the Shyok Suture. It also represents a rare outcrop of the basement rocks to the voluminous Late Cretaceous–Eocene Ladakh Batholith. The Shyok Formation is a younger sequence of volcaniclastic rocks that overlie the Tsoltak Formation and record the Late Cretaceous closure of the Mesotethys Ocean. The petrogenesis of these formations, ophiolite-related harzburgites and norite sill is investigated through petrography, whole-rock geochemistry and U–Pb zircon geochronology. The youngest detrital zircon grains from the Tsoltak Formation indicate Early Cretaceous maximum depositional age and distinctly Gondwanan, Lhasa microcontinent-related provenance with no Eurasian input. The Shyok Formation has Late Cretaceous maximum depositional age and displays a distinct change in provenance to igneous detritus characteristic of the Jurassic–Cretaceous magmatic arc along the southern margin of Eurasia. This is interpreted as a sign of collision of the Lhasa microcontinent and the Shyok ophiolite with Eurasia along the once continuous Shyok–Bangong Suture. The accreted terranes became the new southernmost margin of Eurasia and the basement to the Trans-Himalayan Batholith associated with the India-Eurasia convergence.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5633162

Geochemical evaluation of the in-situ regolith of Madengi hills of Dodoma, Tanzania. Implication on bedrock mapping and delineating gold mineralization target

2021 ◽  
pp. geochem2021-074
Author(s):  
Godson Godfray
Keyword(s):  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Soil Geochemistry ◽  
Residual Soils ◽  
Content Type ◽  
Geochemical Evaluation ◽  
Supplementary Material ◽  
Pathfinder Elements

Successful gold exploration projects depend on a piece of clear information on the association between gold, trace elements, and mineralization controlling factors. The use of soil geochemistry has been an important tool in pinpointing exploration targets during the early stage of exploration. This study aimed to establish the gold distribution, the elemental association between gold and its pathfinder elements such as Cu, Zn, Ag, Ni, Co, Mn, Fe, Cd, V, Cr, Ti, Sc, In, and Se and identify lithologies contributing to the overlying residual soils. From cluster analysis, a high similarity level of 53.93% has been shown with Ag, Cd, and Se at a distance level of 0.92. Au and Se have a similarity level of 65.87% and a distance level of 0.68, hence is proposed to be the most promising pathfinder element. PCA, FA, and the Pearson's correlation matrix of transformed data of V, Cu, Ni, Fe, Mn, Cr, and Co and a stronger correlation between Pb and U, Th, Na, K, Sn, Y, Ta and Be shows that source gold mineralization might be associated with both hornblende gneisses interlayered with quartzite, tonalite, and tonalitic orthogneiss. From the contour map and gridded map of Au and its pathfinder elements, it has been noted that their anomalies and target generated are localized in the Northern part of the area. The targets trend ESE to WNW nearly parallel to the shear zones as a controlling factor of Au mineralization emplacement.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5721965

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

scholarly journals Stenotrophomonas maltophilia phenotypic and genotypic features through 4-year cystic fibrosis lung colonization

2020 ◽  
Author(s):  
Eliana Alcaraz ◽  
Daniela Centrón ◽  
Gabriela Camicia ◽  
María Paula Quiroga ◽  
José Di Conza ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Adult Patient ◽  
Virulence Factors ◽  
Stenotrophomonas Maltophilia ◽  
Type Species ◽  
Mutation Frequency ◽  
Content Type ◽  
Link Type ◽  
Clonal Relatedness ◽  
Over Time

Introduction. Stenotrophomonas maltophilia has emerged as one of the most common multi-drug-resistant pathogens isolated from people with cystic fibrosis (CF). However, its adaptation over time to CF lungs has not been fully established. Hypothesis. Sequential isolates of S. maltophilia from a Brazilian adult patient are clonally related and show a pattern of adaptation by loss of virulence factors. Aim. To investigate antimicrobial susceptibility, clonal relatedness, mutation frequency, quorum sensing (QS) and selected virulence factors in sequential S. maltophilia isolates from a Brazilian adult patient attending a CF referral centre in Buenos Aires, Argentina, between May 2014 and May 2018. Methodology. The antibiotic resistance of 11 S. maltophilia isolates recovered from expectorations of an adult female with CF was determined. Clonal relatedness, mutation frequency, QS variants (RpfC–RpfF), QS autoinducer (DSF) and virulence factors were investigated in eight viable isolates. Results. Seven S. maltophilia isolates were resistant to trimethoprim–sulfamethoxazole and five to levofloxacin. All isolates were susceptible to minocycline. Strong, weak and normomutators were detected, with a tendency to decreased mutation rate over time. XbaI PFGE revealed that seven isolates belong to two related clones. All isolates were RpfC–RpfF1 variants and DSF producers. Only two isolates produced weak biofilms, but none displayed swimming or twitching motility. Four isolates showed proteolytic activity and amplified stmPr1 and stmPr2 genes. Only the first three isolates were siderophore producers. Four isolates showed high resistance to oxidative stress, while the last four showed moderate resistance. Conclusion. The present study shows the long-time persistence of two related S. maltophilia clones in an adult female with CF. During the adaptation of the prevalent clones to the CF lungs over time, we identified a gradual loss of virulence factors that could be associated with the high amounts of DSF produced by the evolved isolates. Further, a decreased mutation rate was observed in the late isolates. The role of all these adaptations over time remains to be elucidated from a clinical perspective, probably focusing on the damage they can cause to CF lungs.

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

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