scholarly journals Heritage Stone 8. Formation of Pinolitic Magnesite at Quartz Creek, British Columbia, Canada: Inferences from Preliminary Petrographic, Geochemical and Geochronological Studies

2021 ◽  
Vol 48 (3) ◽  
Author(s):  
Alexandria Littlejohn-Regular ◽  
John D. Greenough ◽  
Kyle Larson
Keyword(s):  
British Columbia ◽  
Sedimentary Environment ◽  
Dimension Stone ◽  
Fine Grained ◽  
Sedimentary Environments ◽  
Bedding Planes ◽  
Low Concentrations ◽  
Igneous Activity ◽  
Local Host ◽  
Host Rocks

Rocks in the Late Proterozoic Horsethief Creek Group at Quartz Creek in British Columbia display rare ‘pinolitic’ textures resembling those described in some sparry magnesite deposits elsewhere in the world. Elongated white magnesite crystals up to 30 cm long occur in a contrasting, dark, fine-grained matrix of dolomite, chlorite, organic material, clay minerals and pyrite. The rocks are aesthetically appealing for use in sculpture and as dimension stone. The term ‘pinolite’ is derived from the superficial similarities between these unusual textures and pinecones. Petrographic examination indicates that these textures formed when metasomatic fluids replaced primary sedimentary dolomite with magnesite. Fluids moved along fractures and bedding planes with repeated fracturing yielding magnesite crystals oriented in opposite directions on either side of annealed fractures, and broken magnesite crystals adjacent to later fractures. Magnesite contains dolomite microinclusions and has elevated Ca contents that are consistent with its formation by replacement of dolomite. Low concentrations of Cr, Ni, Co, Ti, Sr, and Ba in magnesite also imply formation in a metasomatic rather than a sedimentary environment. The rare earth element (REE) concentrations in the Quartz Creek magnesite are higher than those in most evaporitic magnesite and REE patterns lack the Ce and Eu anomalies that characterize carbonate rocks from sedimentary environments. Enrichment in light REE relative to heavy REE, and the similarities between dolomite, chlorite, and magnesite REE profiles, imply that metasomatic fluids modified the original sedimentary geochemical signature of the dolostones during formation of the pinolite rocks. A Late Ordovician to Early Silurian U–Pb age (433 ± 12 Ma), for titanite in the black matrix surrounding the sparry magnesite is younger than the local host rocks, and also younger than the Mesoproterozoic to Middle Cambrian stratigraphic ages of the host rocks for nearby magnesite deposits. The ca. 433 Ma titanite overlaps the ages for numerous fault-associated diatremes and volcaniclastic deposits in the area. Possibly the igneous activity furnished heat for, and/or was the source for, metasomatic fluids that produced the pinolite deposits.

New U–Pb age constraints on latest Cretaceous magmatism and associated mineralization in the Fawnie Range, Nechako Plateau, central British Columbia

2001 ◽  
Vol 38 (4) ◽  
pp. 619-637 ◽  
Author(s):  
R M Friedman ◽  
L J Diakow ◽  
R A Lane ◽  
J K Mortensen
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Western Margin ◽  
Fine Grained ◽  
The North ◽  
Continental Arc ◽  
Igneous Activity ◽  
Minimum Age ◽  
Plateau Central ◽  
Cretaceous Magmatism

New U–Pb ages and K–Ar dates, primarily for rocks proximal to mineral occurrences in the Fawnie Range of central British Columbia, document latest Cretaceous (ca. 74–66 Ma) continental-arc igneous activity and date associated base and precious metal mineralization. U–Pb ages of ca. 73–69 Ma for the Capoose pluton and hypabyssal to extrusive garnet rhyolites at the Capoose prospect demonstrate a latest Cretaceous age for mineralization and a likely plutonic source for mineralizing fluids. A U–Pb age of ca. 67 Ma for a late mineralized felsic dyke and two K–Ar dates (ca. 70 and 68 Ma) for hornfelsed Jurassic volcanic rocks at the Blackwater–Davidson prospect constrain a latest Cretaceous age for mineralization. A U–Pb age of ca. 74 Ma for a fine grained diorite sill that cuts a significant epithermal gold vein at the Tsacha prospect places a minimum age on mineralization at this probable Jura-Cretaceous deposit and documents latest Cretaceous magmatism. Latest Cretaceous K–Ar dates are reported for an andesite flow adjacent to the Eocene Holy Cross deposit (ca. 66 Ma), about 35 km north of the Fawnie Range, and a Kasalka Group rhyolite (ca. 68 Ma) exposed near the western margin of the Nechako Plateau. Latest Cretaceous magmatism and mineralization in the Fawnie Range represent the waning stages of Bulkley suite magmatism and porphyry-style mineralization, which was concentrated along the western margin of the Nechako Plateau at circa 88–70 Ma. The distribution of latest Cretaceous arc igneous rocks along the North American Cordilleran is reviewed and tectonic implications discussed.

Postglacial Diatom Stratigraphy in Relation to the Recession of Glacial Lake Agassiz

1975 ◽  
Vol 5 (4) ◽  
pp. 529-540 ◽  
Author(s):  
J.C. Ritchie ◽  
L.K. Koivo
Keyword(s):  
Sandy Beach ◽  
Sedimentary Environment ◽  
Glacial Lake ◽  
Lake Agassiz ◽  
Organic Detritus ◽  
Sedimentary Environments ◽  
Grand Rapids ◽  
Glacial Lake Agassiz ◽  
Diatom Stratigraphy ◽  
Beach Sands

The sediment and diatom stratigraphy of a small pond on The Pas moraine, near Grand Rapids, Manitoba, reveals a change in sedimentary environment related directly to the last stages of Glacial Lake Agassiz. Beach sands were replaced by clay 7300 14C y. a., then by organic silt and, at 4000 14C y. a. by coarse organic detritus; the corresponding diatom assemblages were (I) a predominantly planktonic spectrum in beach sands, (II) a rich assemblage of nonplanktonic forms, and (III) a distinctly nonplanktonic acidophilous spectrum. These results confirm Elson's (1967) reconstruction of the extent and chronology of the final (Pipun) stage of Glacial Lake Agassiz. The sedimentary environments change from a sandy beach of a large lake at 7300 BP to a small, shallow eutrophic pond with clay and silt deposition from 7000 to 4000 BP. From 4000 BP to the present, organic detritus was deposited in a shallow pond that tended toward dystrophy.

Telluride Mineralogy of the Deer Horn Au-Ag-Te-(Bi-Pb-W) Deposit, British Columbia: Implications for the Generation of Tellurides

2021 ◽  
Author(s):  
Jordan A. Roberts ◽  
Lee A. Groat ◽  
Paul G. Spry ◽  
Jan Cempírek
Keyword(s):  
British Columbia ◽  
Fluid Inclusions ◽  
Hanging Wall ◽  
Oscillatory Zoning ◽  
Stage Iii ◽  
Fine Grained ◽  
Melting Temperatures ◽  
Homogenization Temperatures ◽  
Intrusive Suite ◽  
Cathodoluminescence Imaging

ABSTRACT The Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions. The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.

scholarly journals Theoretical Interpretation of the Exceptional Sediment Transport of Fine-grained Dispersal Systems Associated with Bedform Categories

2018 ◽  
Author(s):  
Tian Zhao ◽  
Qian Yu ◽  
Yunwei Wang ◽  
Shu Gao
Keyword(s):  
Sediment Transport ◽  
Regime Shift ◽  
Sedimentary Environment ◽  
Sediment Flux ◽  
Theoretical Interpretation ◽  
Fine Grained ◽  
Transport Regime ◽  
Source To Sink ◽  
Bed Roughness ◽  
Set Up

Abstract. Being a widespread source-to-sink sedimentary environment, the fine-grained dispersal system (FGDS) features remarkably high sediment flux, interacting closely with local morphology and ecosystem. Such exceptional transport is believed to be associated with changes in bedform geometry, which further demands theoretical interpretation. Using van Rijn (2007a) bed roughness predictor, we set up a simple numerical model to calculate sediment transport, classify sediment transport behaviors into dune and (mega-)ripple dominant regimes, and discuss the causes of the sediment transport regime shift linked with bedform categories. Both regimes show internally consistent transport behaviors, and the latter, associated with FGDSs, exhibits considerably higher sediment transport rate than the previous. Between lies the coexistence zone, the sediment transport regime shift accompanied by degeneration of dune roughness, which can considerably reinforce sediment transport and is further highlighted under greater water depth. This study can be applied to modeling of sediment transport and morphodynamics.

scholarly journals Geochemical Features of Redox-Sensitive Trace Metals in Sediments under Oxygen-Depleted Marine Environments

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1021
Author(s):  
Moei Yano ◽  
Kazutaka Yasukawa ◽  
Kentaro Nakamura ◽  
Minoru Ikehara ◽  
Yasuhiro Kato
Keyword(s):  
Sedimentary Environment ◽  
Organic Matter Content ◽  
Oxygen Depletion ◽  
Major And Trace Elements ◽  
Matter Content ◽  
Open Ocean ◽  
Chemical Compositions ◽  
Marine Environments ◽  
High Productivity ◽  
Sedimentary Environments

Organic- and sulfide-rich sediments have formed in oxygen-depleted environments throughout Earth’s history. The fact that they are generally enriched in redox-sensitive elements reflects the sedimentary environment at the time of deposition. Although the modern ocean is well oxidized, oxygen depletion occurs in certain areas such as restricted basins and high-productivity zones. We measured bulk chemical compositions (major and trace elements, total organic carbon, and total sulfur) of organic- and sulfide-rich sediments collected from eight areas having oxygen-depleted water to discuss relationships between geochemical features and sedimentary environments. Major elemental compositions generally show mixtures of terrigenous detritus and biogenic carbonate. Some redox-sensitive elements might be controlled by organic matter content, whereas others could be contained in sulfide minerals in sediments. In particular, Mo and U show a characteristic trend; areas with higher Mo and U—at least partially owing to a depositional process called the “particulate shuttle”—generally correspond to regions influenced by the open ocean. In contrast, areas with lower Mo and U are more restricted marine environments. This suggests that the degree of Mo and U enrichment reflects the geography in terms of proximity to the open ocean, or the degree of the supply of these elements from the open ocean.

Age and sedimentary environments of uranium host rocks, Colorado Plateau

1955 ◽  
Vol 50 (2) ◽  
pp. 127-134 ◽  
Author(s):  
Yngvar William Isachsen ◽  
Thomas Wilson Mitcham ◽  
Hiram Bud Wood
Keyword(s):  
Colorado Plateau ◽  
Sedimentary Environments ◽  
Host Rocks

Sedimentary environment prediction of grain-size data based on machine learning approach

2020 ◽  
Vol 8 (3) ◽  
pp. SL71-SL78
Author(s):  
Qiao Su ◽  
Yanhui Zhu ◽  
Fang Hu ◽  
Xingyong Xu
Keyword(s):  
Machine Learning ◽  
Grain Size ◽  
Prediction Model ◽  
Sedimentary Environment ◽  
Machine Learning Algorithms ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Data Set ◽  
Sedimentary Environments ◽  
Size Data

Grain size is one of the most important records for sedimentary environment, and researchers have made remarkable progress in the interpretation of sedimentary environments by grain size analysis in the past few decades. However, these advances often depend on the personal experience of the scholars and combination with other methods used together. Here, we constructed a prediction model using the K-nearest neighbors algorithm, one of the machine learning methods, which can predict the sedimentary environments of one core through a known core. Compared to the results of other studies based on the comprehensive data set of grain size and four other indicators, this model achieved a high precision value only using the grain size data. We have also compared our prediction model with other mainstream machine learning algorithms, and the experimental results of six evaluation metrics shed light on that this prediction model can achieve the higher precision. The main errors of the model reflect the length of the conversation area of sedimentary environment, which is controlled by the sedimentary dynamics. This model can provide a quick comparison method of the cores in a similar environment; thus, it may point out the preliminary guidance for further study.

scholarly journals ORGANIC COMPOUNDS AS PROXIES OF THE SEDIMENTARY ENVIRONMENTAL QUALITY OF THE MARICÁ-GUARAPINA LAGOON SYSTEM (SE, BRAZIL)

2019 ◽  
Vol 4 (2) ◽  
pp. 159-173 ◽  
Author(s):  
Lazaro Laut ◽  
Maria Virgina Alves Martins ◽  
Pierre Belart ◽  
Maria Lucia Lorini ◽  
Iara Clemente ◽  
...  
Keyword(s):  
Organic Matter ◽  
Rio De Janeiro ◽  
Sedimentary Environment ◽  
Environmental Parameters ◽  
Geochemical Data ◽  
Fine Grained ◽  
Lagoon System ◽  
Se Brazil ◽  
Anthropogenic Contribution

Bottom sediment is a natural trap for organic matter and different kinds of pollutants. The accumulation of large amount of organic matter gives rise to the eutrophication of the aquatic ecosystems. The analyses of the quantity and quality of the organic matter (biopolymers) help to determine the trophic status of coastal ecosystems. The Maricá-Guarapina Lagoon System (MGLS) is located in Rio de Janeiro and is composed by four connected lagoons: Maricá, Barra, Padre and Guarapina. It has been suffering impacts due to the intense and uncontrolled property speculation. Based on this problem, this study aimed to characterize the organic matter (OM) amount and quality in sediments and the relation with the impacted areas in this lagoon system. The collected sediment samples were analyzed for geochemical data combined with grain size and physical-chemical environmental parameters of the bottom water. Statistical results evidenced that the sedimentary environment of the MGLS is heterogenous. The organic matter supplied to the MGLS is provided from different sources but the autochthonous contribution (phytoplanktonic productivity and vegetal detritus from the mangrove fringe) prevails. The anthropogenic contribution was more evident in Padre Lagoon, where the sediments had relatively low TOC contents (0.1-0.8%). The MGLS is accumulating mainly aged organic matter. The most impacted zones were found in Guarapina, Barra and Maricá lagoons, in bottoms of fine-grained sediments, with relatively high TOC and labile biopolymeric compounds (proteins, carbohydrates and lipids) contents, which should evolve into an ever-increasing stage of eutrophication. COMPOSTOS ORGÂNICOS USADOS COMO INDICADORES DA QUALIDADE AMBIENTAL SEDIMENTAR DO SISTEMA LAGUNAR MARICÁ-GUARAPINA (SE DO BRASIL)ResumoO sedimento de fundo constitui uma armadilha natural para a matéria orgânica e diferentes tipos de poluentes. O acúmulo de grande quantidade de matéria orgânica dá origem à eutrofização dos ecossistemas aquáticos. Estimativas de quantidade e qualidade da matéria orgânica (biopolímeros) podem ajudar a determinar o estado trófico dos ecossistemas costeiros. O Sistema Lagunar de Maricá-Guarapina (MGLS), localizado no Estado do Rio de Janeiro (SE do Brasil), é composto por quatro lagunas interconectadas: Maricá, Barra, Padre e Guarapina. Este sistema tem sofrido impactos devido à intensa e descontrolada especulação imobiliária. Neste contexto, este estudo teve como objetivo caracterizar a quantidade e qualidade de matéria orgânica (MO) dos sedimentos do MGLS. Foram obtidos dados geoquímicos e confrontados com resultados granulométricos em amostras de sedimentos coletados em 22 estações de amostragem e analisados parâmetros físico-químicos da água. Os resultados estatísticos evidenciaram que o ambiente sedimentar do MGLS é heterogêneo. Este sistema recebe matéria orgânica de diferentes fontes, sendo, porém, prevalecente a contribuição autóctone (produtividade fitoplanctônica e detritos vegetais dos manguezais existentes na região). A contribuição antropogênica de matéria orgânica foi mais evidente na Lagoa do Padre, onde os sedimentos apresentaram teores de COT relativamente baixos (0,1-0,8%). As zonas mais impactadas foram encontradas em fundos de sedimentos finos, com teores relativamente elevados de COT e de compostos biopoliméricos lábeis (proteínas, carboidratos e lipídios), nas lagunas de Guarapina, Barra e Maricá. Os resultados obtidos revelam também que o MGLS está acumulando principalmente matéria orgânica envelhecida e permitem prever que as referidas áreas podem evoluir para um estágio de cada vez maior grau de eutrofização.Palavras-chave: Lagunas Costeiras Tropicais. Biopolímeros. Eutrofização. Dinâmica Sedimentar.

Sign in / Sign up

Export Citation Format

Share Document