Density determinations of basic volcanic rocks of the Yellowknife supergroup by gravity measurements in mine shafts—Yellowknife, Northwest Territories

Geophysics ◽  
1980 ◽  
Vol 45 (1) ◽  
pp. 18-31 ◽  
Author(s):  
R. A. Gibb ◽  
M. D. Thomas
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Mine Shaft ◽  
Average Interval ◽  
Basaltic Rocks ◽  
Surface Samples ◽  
Gravity Measurements ◽  
Vertical Density ◽  
Basic Volcanic

Gravity measurements were made in two gold mine shafts sunk in the Archean Yellowknife greenstone belt to determine the in‐situ densities of basic volcanic rocks of the Kam formation, Yellowknife supergroup. Thirteen stations were occupied between the surface and a depth of 608 m at an average interval of about 50 m in the C shaft of Giant Yellowknife Mines Limited, and 14 stations were occupied between the surface and a depth of 1598 m at an average interval of about 120 m in the Robertson shaft of Con mine, Cominco Limited. Densities were computed using the terminology of borehole gravimetry with appropriate corrections for surface terrain and underground voids such as shafts, drifts, and stopes. Weighted mean in‐situ densities of [Formula: see text] (36 to 608 m depth) and [Formula: see text] (surface to 1598 m depth) were obtained from the gravity measurements for the Giant and Robertson sections, respectively; these values compare with mean densities of 2.82 and [Formula: see text] obtained from rock samples collected at the underground gravity stations. Sheared specimens and massive specimens collected at both underground and surface gravity stations have mean densities of 2.80 and [Formula: see text], respectively. Unaltered surface samples collected at stratigraphic intervals of about 150 m throughout the entire volcanic sequence have a mean density of [Formula: see text]. Core samples obtained from holes drilled from the bottom of C shaft extend the vertical density profile for the Giant section from a depth of 608 to 1416 m; the mean density of these samples is [Formula: see text]. The lower bulk densities obtained from the mine shaft experiments reflect in part the high proportion of sheared rocks and in part the presence of lower‐density members of the Kam formation (andesite, dacite, tuff, breccia, and agglomerate) in the vicinity of the shafts, as opposed to purely massive basaltic rocks. A density of [Formula: see text] based on the proportion of low‐ and high‐density rocks in the volcanic belt is considered to be more representative of the Kam formation as a whole.

Geochemistry of Siluro-Devonian Tobique volcanic belt in northern and central New Brunswick (Canada): tectonic implications

1989 ◽  
Vol 26 (6) ◽  
pp. 1282-1296 ◽  
Author(s):  
J. Dostal ◽  
R. A. Wilson ◽  
J. D. Keppie
Keyword(s):  
New Brunswick ◽  
Mantle Source ◽  
Upper Mantle ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Continental Rift ◽  
Basaltic Rocks ◽  
Incompatible Elements ◽  
Tectonic Implications

Siluro-Devonian volcanic rocks of the northwestern mainland Appalachians are found mainly in the Tobique belt of New Brunswick where they consist predominantly of bimodal mafic–felsic suites erupted in a continental-rift environment. The axis of the Tobique rift trends north-northeast – south-southwest, obliquely to the regional northeast–southwest trend of the Appalachians. These geometric relationships are interpreted as being the result of rifting in a sinistral shear regime produced during emplacement of the Avalon terrene. The basaltic rocks are continental tholeiites and transitional basalts derived from a heterogeneous upper-mantle source that was enriched in incompatible elements relative to the primordial mantle. The mantle source was probably affected by the subduction processes.

Discerning asthenospheric, lithospheric, and crustal influences on the geochemistry of Quaternary basalts from the Iskut–Unuk rivers area, northwestern British Columbia

1995 ◽  
Vol 32 (9) ◽  
pp. 1451-1461 ◽  
Author(s):  
Brian L. Cousens ◽  
Mary Lou Bevier
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Volcanic Field ◽  
Northwest Pacific ◽  
Small Range ◽  
Geochemical Composition ◽  
Basaltic Rocks ◽  
Depleted Mantle ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

Pleistocene- to Holocene-age basaltic rocks of the Iskut–Unuk rivers volcanic field, at the southern terminus of the Stikine Volcanic Belt in the northern Canadian Cordillera, provide information on the geochemical composition of the underlying mantle and processes that have modified parental magmas. Basaltic rocks from four of the six eruptive centres are moderately evolved (MgO = 5.7–6.8%) alkaline basalts with chondrite-normalized La/Sm = 1.6–1.8, 87Sr/86Sr = 0.70336–0.70361, εNd = +4.4 to +5.9, and 206Pb/204Pb = 19.07–19.22. The small range of isotopic compositions and incompatible element ratios imply a common "depleted" mantle source for the basalts, similar to the sources of enriched mid-ocean ridge basalts from northwest Pacific spreading centres or alkali olivine basalts from the western Yukon. Positive Ba and negative Nb anomalies that increase in size with increasing SiO2 and 87Sr/86Sr indicate that the basalts are contaminated by Mesozoic-age, arc-related, Stikine Terrane crust or lithospheric mantle through which the magmas passed. Lavas from a fifth volcanic centre, Cinder Mountain, have undergone greater amounts of fractional crystallization and are relatively enriched in incompatible elements, but are isotopically identical to least-contaminated Iskut–Unuk rivers basalts. Iskut–Unuk rivers lavas share many of the geochemical characteristics of volcanic rocks from other Stikine Belt and Anahim Belt centres, as well as alkali olivine basalts from the Fort Selkirk volcanic centres of the western Yukon.

Bio-signatures in metabasaltic glass of a Caledonian ophiolite, West Norway

2002 ◽  
Vol 139 (6) ◽  
pp. 601-608 ◽  
Author(s):  
HARALD FURNES ◽  
KARLIS MUEHLENBACHS ◽  
TERJE TORSVIK ◽  
OLE TUMYR ◽  
LANG SHI
Keyword(s):  
Organic Matter ◽  
Early Stage ◽  
Volcanic Rocks ◽  
Present Evidence ◽  
X Ray ◽  
Basaltic Rocks ◽  
Facies Metamorphism ◽  
Reducing Bacteria ◽  
Greenschist Facies Metamorphism

Evidence of bioalteration of natural basaltic rocks, presently receiving much attention, has so far been restricted to in situ oceanic crust and ophiolites in which fresh glass is still present. Here we present evidence of preserved bio-signatures in the chilled margin of pillow lavas of an old (443 Ma) ophiolite that has suffered pervasive lower greenschist facies metamorphism and deformation. X-ray mapping of initial alteration zones shows the remains of organic carbon associated with highly-concentrated Fe and S. Bioproduction of CO2 is further reflected in the low δ13C values of calcite extracted from pillow rims, compatible with microbe-induced fractionation during oxidation of organic matter. We attribute these effects to growth of sulphate-reducing bacteria at the early stage of ophiolite formation. During energy metabolism these bacteria reduce sulphate to H2S and oxidize organic matter to CO2 . Hydrogen sulphide will eventually react with iron and form pyrite, and carbon dioxide is precipitated as calcium carbonate. The results of this study may thus trigger the search for bio-signatures in glassy volcanic rocks of any age.

A CONFIRMATION BY GRAVITY MEASUREMENTS OF AN UNDERGROUND DENSITY PROFILE BASED ON CORE DENSITIES

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1108-1132 ◽  
Author(s):  
Thane H. McCulloh
Keyword(s):  
Sedimentary Rocks ◽  
Core Sample ◽  
Mine Shaft ◽  
Density Profiles ◽  
Sample Density ◽  
Gravity Measurements ◽  
Natural Density ◽  
Bulk Volume ◽  
Gravity Variations

Accurate laboratory measurements of dry bulk densities of 79 samples of Paleozoic sedimentary rocks from a 2,851‐ft deep core hole near Barberton, Ohio, are the basis of a vertical profile of “natural” density which differs on the average [Formula: see text] or less from a profile of in‐situ density calculated from gravity variations observed using a LaCoste and Romberg gravimeter in an adjacent 2,247‐ft‐deep vertical mine shaft. Both profiles agree well with the most meaningful Barberton core sample densities reported by Hammer (1950, Fig. 3), but are significantly lower than in‐situ interval densities calculated by Hammer from gravity variations observed in the shaft using a Gulf gravimeter. The [Formula: see text] average discrepancy between the old and new in‐situ density profiles is probably attributable to a 12‐percent error in calibration of the Gulf gravimeter. The close agreement between the new profiles of “natural” and in‐situ density suggests that changes in bulk volume of compact sedimentary rocks that occur during or following the coring process are probably ordinarily so small that properly constructed core sample density profiles are reproducible and reliable even when small numbers of samples of aged cores are used. If they are to be used for determination of in‐situ density, underground gravity measurements must be accurate as well as precise.

A New Approach to the Selection of Materials for Engineered Barriers and Appropriate Host Rocks for High Level Waste Disposal

1994 ◽  
Vol 353 ◽  
Author(s):  
B.I. Omelianenko ◽  
B.S. Nikonov ◽  
B.I. Ryzhov ◽  
N.D. Shikina ◽  
S.V. Yudintsev
Keyword(s):  
Volcanic Rocks ◽  
High Level Waste ◽  
Sorptive Capacity ◽  
Basaltic Rocks ◽  
Distribution Study ◽  
Deep Wells ◽  
Basic Volcanic ◽  
High Level ◽  
Host Rocks ◽  
Basic Rocks

AbstractSorptive properties of weathered dunites, gabbro-diabases and basic volcanic rocks for Sr and Cs were studied. The results show that the sorptive capacities of these rocks are equivalent to or, in some cases, superior to industrial sorptive materials. Results of a uranium distribution study by fission-track radiography suggest that material from weathered basic rocks is characterized by high sorptive properties for uranium also. One can assume that other radionuclides of the transuranic group will be intensely sor-bed by the residuum of weathered basic rocks. Low-temperature hyd-rothermal transformation leads to sealing fissures of the basic rocks with highly sorptive minerals, for example, smectite, chlorite, serpentine, talc, zeolite, hydroxides of Fe, Ti, Mn. The process results in contemporaneous decreasing hydraulic conductivity and increasing sorptive capacity of the rocks. HLW disposal at the radiochemical plant “Mayak” is expected to be produced in deep wells situated in basaltic rocks. The safety of disposal is based on high sorptive properties of the crust of weathering and protective capacities of volcanic rocks. This method is not expensive and may allow the disposal of HLW in the near future.

scholarly journals Evidence from the Kyrenia Range, Cyprus, of the northerly active margin of the Southern Neotethys during Late Cretaceous–Early Cenozoic time

2011 ◽  
Vol 149 (2) ◽  
pp. 264-290 ◽  
Author(s):  
ALASTAIR H. F. ROBERTSON ◽  
KEMAL TASLI ◽  
NURDAN İNAN
Keyword(s):  
Continental Margin ◽  
Carbonate Platform ◽  
Middle Eocene ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Basaltic Rocks ◽  
Tectonic Model ◽  
The North ◽  
Basic Volcanic ◽  
Upper Maastrichtian

AbstractSedimentary geology and planktonic foraminiferal biostratigraphy have shed light on the geological development of the northern, active continental margin of the Southern Neotethys in the Kyrenia Range. Following regional Triassic rifting, a carbonate platform developed during Jurassic–Cretaceous time, followed by its regional burial, deformation and greenschist-facies metamorphism. The platform was exhumed by Late Maastrichtian time and unconformably overlain by locally derived carbonate breccias, passing upwards into Upper Maastrichtian pelagic carbonates. In places, the pelagic carbonates are interbedded with sandstone turbidites derived from mixed continental, basic volcanic, neritic carbonate and pelagic lithologies. In addition, two contrasting volcanogenic sequences are exposed in the western-central Kyrenia Range, separated by a low-angle tectonic contact. The first is a thickening-upward sequence of Campanian–Lower Maastrichtian(?) pelagic carbonates, silicic tuffs, silicic lava debris flows and thick-bedded to massive rhyolitic lava flows. The second sequence comprises two intervals of basaltic extrusive rocks interbedded with pelagic carbonates. The basaltic rocks unconformably overlie the metamorphosed carbonate platform whereas no base to the silicic volcanic rocks is exposed. Additional basaltic lavas are exposed throughout the Kyrenia Range where they are dated as Late Maastrichtian and Late Paleocene–Middle Eocene in age. In our proposed tectonic model, related to northward subduction of the Southern Neotethys, the Kyrenia platform was thrust beneath a larger Tauride microcontinental unit to the north and then was rapidly exhumed prior to Late Maastrichtian time. Pelagic carbonates and sandstone turbidites of mixed, largely continental provenance then accumulated along a deeply submerged continental borderland during Late Maastrichtian time. The silicic and basaltic volcanogenic rocks erupted in adjacent areas and were later tectonically juxtaposed. The Campanian–Early Maastrichtian(?) silicic volcanism reflects continental margin-type arc magmatism. In contrast, the Upper Maastrichtian and Paleocene–Middle Eocene basaltic volcanic rocks erupted in an extensional (or transtensional) setting likely to relate to the anticlockwise rotation of the Troodos microplate.

scholarly journals Lithostratigraphy and lithogeochemistry of Ediacaran alkaline basaltic rocks of the Musgravetown Group, Bonavista Peninsula, northeastern Newfoundland, Canada: an extensional volcanogenic basin in the type-Avalon terrane

2021 ◽  
Vol 57 ◽  
pp. 207-234
Author(s):  
Andrea Mills ◽  
Hamish Sandeman
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Geodynamic Setting ◽  
Alkaline Basalt ◽  
Fine Grained ◽  
Basaltic Rocks ◽  
Slab Rollback ◽  
Low Degree ◽  
Magmatic Underplating ◽  
Head Formation

Volcanic rocks of the Ediacaran Musgravetown Group on Bonavista Peninsula, Avalon terrane, Newfoundland, include basal ca. 600 Ma calc-alkaline basalt succeeded by continental tholeiite and alkaline rhyolite of the ca. 592 Ma Plate Cove volcanic belt (Bull Arm  Formation), indicating a change from subduction-related to extensionrelated tectonic regimes during that interval. Alkalic basalts on northeastern (Dam Pond area) and southwestern (British Harbour area) Bonavista Peninsula occur below and above, respectively, the  ca. 580 Ma glacial Trinity facies. Dam Pond basalt occurs in a structural dome intercalated with and flanked by fine-grained, siliciclastic deposits (Big Head Formation) overlain by Trinity facies. The British Harbour basalt occurs above the Trinity facies, in an upward- coarsening sandstone sequence (Rocky Harbour Formation) overlain by red beds of the Crown Hill Formation (uppermost Musgravetown Group). The Rocky Harbour and Big Head formations are likely stratigraphically interfingered proximal and distal  deposits, respectively, derived from erosion of the Bull Arm Formation and older Avalonian assemblages.The Big Head basalts have lower SiO2, Zr, FeOT, P2O5, TiO2 and higher Mg#, Cr, V, Co and Ni contents, and are therefore more primitive than the more FeOT-, TiO2-, and P2O5-rich British Harbour basalts. Large-ionlithophile and rare-earth-element concentrations and ratios indicate that both suites originated from low degree partial melts of deep, weakly garnet-bearing, undepleted asthenospheric peridotite sources, with magma conduits likely focused along regional extensional faults. The protracted and episodic extension-related volcanic activity is consistent with a geodynamic setting that evolved from a mature arc into extensional basins with slowly waning magmatism, possibly involving slab rollback and delamination followed by magmatic underplating. The duration and variation of both volcanism and sedimentation indicate that the Musgravetown Group should be elevated to a Supergroup in  order to facilitate  future correlation of its constituent parts with other Avalonian basins.

scholarly journals Evaluation of Stiffness and Dynamic Properties of a Mine Shaft Steelwork Structure through In Situ Tests and Numerical Simulations

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 664
Author(s):  
Jacek Jakubowski ◽  
Przemysław Fiołek
Keyword(s):  
Numerical Simulations ◽  
Dynamic Properties ◽  
Vertical Motion ◽  
Load Test ◽  
Mode Shapes ◽  
Dynamic Amplification Factor ◽  
In Situ Tests ◽  
Mine Shaft ◽  
Numerical Investigations

A mine shaft steelwork is a three-dimensional frame that directs the vertical motion of conveyances in mine shafts. Here, we conduct field and numerical investigations on the stiffness and dynamic properties of these structures. Based on the design documentation of the shaft, materials data, and site inspection, the steelwork’s finite element model, featuring material and geometric non-linearities, was developed in Abaqus. Static load tests of steelwork were carried out in an underground mine shaft. Numerical simulations reflecting the load test conditions showed strong agreement with the in situ measurements. The validated numerical model was used to assess the dynamic characteristics of the structure. Dynamic linear and non-linear analyses delivered the natural frequencies, mode shapes, and structural response to dynamic loads. The current practices and regulations regarding shaft steelwork design and maintenance do not account for the stiffness of guide-to-bunton connections and disregard dynamic factors. Our experimental and numerical investigations show that these connections provide considerable stiffness, which leads to the redistribution and reduction in bending moments and increased stiffness of the construction. The results also show a high dynamic amplification factor. The omission of these features implicates an incorrect assessment of the design loads and can lead to over- or under-sized structures and ultimately to shortened design working life or failure.

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