Rediscovery of the Mattawa Anorthosite Massif, Grenville Province, Quebec

2005 ◽  
Vol 42 (10) ◽  
pp. 1699-1718 ◽  
Author(s):  
Brent E Owens ◽  
Robert F Dymek
Keyword(s):  
Rock Type ◽  
Laboratory Data ◽  
Field Observations ◽  
Plagioclase Composition ◽  
Grenville Province ◽  
The Core ◽  
South Central ◽  
Border Zones ◽  
Anorthosite Massif ◽  
Domal Structure

We present new field observations and laboratory data confirming the presence of the Mattawa Anorthosite Massif (MAT), whose existence in south-central Quebec was hinted at more than 35 years ago. MAT thus represents a newly recognized member of the late- to post-tectonic ~1060–1010 Ma andesine anorthosite belt that includes the Château-Richer, St. Urbain, and Labrieville massifs. The dominant rock type at MAT is foliated andesine anorthosite or leuconorite, and orientations of foliations indicate that the pluton has the shape of a dome. MAT contains separate core and border zones, which are distinguished on the basis of plagioclase composition and concentrations of Ga, Rb, Sr, and Ba. Xenoliths of labradorite anorthosite having Ga, Sr, and Ba concentrations different from those of the host andesine anorthosites occur sporadically throughout the pluton as well. Lastly, rocks enriched in Fe, Ti, and P (jotunite, oxide–apatite gabbronorite, nelsonite, ilmenitite) also occur at MAT, primarily near the core–border transition or at the pluton margins. Compared with other anorthosites in the andesine belt, MAT is compositionally most similar to Labrieville. By analogy with Labrieville, we interpret the concentric zoning of MAT (more sodic core, more calcic border) to reflect polybaric crystallization accompanying upward intrusion as a magmatic diapir, which also produced the overall domal structure. The labradorite xenoliths bear little physical or compositional resemblance to typical Lac St. Jean rocks. Therefore, if the xenoliths were derived from the Lac St. Jean Anorthosite, their present character must reflect considerable modification by the Mattawa magma.

Enhanced and Rock Typing-Based Reservoir Characterization of the Palaeocene Harash Carbonate Reservoir-Zelten Field-Sirte Basin-Libya

2021 ◽  
Author(s):  
Mohamed Masoud ◽  
W. Scott Meddaugh ◽  
Masoud Eljaroshi ◽  
Khaled Elghanduri
Keyword(s):  
Rock Type ◽  
Carbonate Reservoir ◽  
Classification Model ◽  
Reservoir Rocks ◽  
The Core ◽  
Core Samples ◽  
Rock Types ◽  
Rock Typing ◽  
Open Hole ◽  
Type Classification

Abstract The Harash Formation was previously known as the Ruaga A and is considered to be one of the most productive reservoirs in the Zelten field in terms of reservoir quality, areal extent, and hydrocarbon quantity. To date, nearly 70 wells were drilled targeting the Harash reservoir. A few wells initially naturally produced but most had to be stimulated which reflected the field drilling and development plan. The Harash reservoir rock typing identification was essential in understanding the reservoir geology implementation of reservoir development drilling program, the construction of representative reservoir models, hydrocarbons volumetric calculations, and historical pressure-production matching in the flow modelling processes. The objectives of this study are to predict the permeability at un-cored wells and unsampled locations, to classify the reservoir rocks into main rock typing, and to build robust reservoir properties models in which static petrophysical properties and fluid properties are assigned for identified rock type and assessed the existed vertical and lateral heterogeneity within the Palaeocene Harash carbonate reservoir. Initially, an objective-based workflow was developed by generating a training dataset from open hole logs and core samples which were conventionally and specially analyzed of six wells. The developed dataset was used to predict permeability at cored wells through a K-mod model that applies Neural Network Analysis (NNA) and Declustring (DC) algorithms to generate representative permeability and electro-facies. Equal statistical weights were given to log responses without analytical supervision taking into account the significant log response variations. The core data was grouped on petrophysical basis to compute pore throat size aiming at deriving and enlarging the interpretation process from the core to log domain using Indexation and Probabilities of Self-Organized Maps (IPSOM) classification model to develop a reliable representation of rock type classification at the well scale. Permeability and rock typing derived from the open-hole logs and core samples analysis are the main K-mod and IPSOM classification model outputs. The results were propagated to more than 70 un-cored wells. Rock typing techniques were also conducted to classify the Harash reservoir rocks in a consistent manner. Depositional rock typing using a stratigraphic modified Lorenz plot and electro-facies suggest three different rock types that are probably linked to three flow zones. The defined rock types are dominated by specifc reservoir parameters. Electro-facies enables subdivision of the formation into petrophysical groups in which properties were assigned to and were characterized by dynamic behavior and the rock-fluid interaction. Capillary pressure and relative permeability data proved the complexity in rock capillarity. Subsequently, Swc is really rock typing dependent. The use of a consistent representative petrophysical rock type classification led to a significant improvement of geological and flow models.

scholarly journals Softening and instability of natural slopes in highly fissured plastic clay shales

2006 ◽  
Vol 6 (4) ◽  
pp. 529-539 ◽  
Author(s):  
L. Picarelli ◽  
G. Urciuoli ◽  
A. Mandolini ◽  
M. Ramondini
Keyword(s):  
Laboratory Data ◽  
Field Observations ◽  
Plastic Clay ◽  
Clay Shales ◽  
Italian Apennines ◽  
First Time ◽  
Natural Slopes

Abstract. Softening is often considered to be the main cause of first-time slides in OC clay, but so far the mechanics of softening has not been satisfactorily explained. Bearing on laboratory data and field observations about landslides in tectonized highly plastic clay shales of Italian Apennines, the paper describes a process of soil weakening that could explain some failures of natural slopes.

Modeling of Production Decline Caused by Fines Migration in Deepwater Reservoirs

SPE Journal ◽  
2019 ◽  
Vol 25 (01) ◽  
pp. 391-405
Author(s):  
Yunhui Tan ◽  
Yan Li ◽  
Margaretha C. M. Rijken ◽  
Karim Zaki ◽  
Bin Wang ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Critical Velocity ◽  
Laboratory Data ◽  
Permeability Reduction ◽  
Fines Migration ◽  
The Core ◽  
Decline Rate ◽  
Reduction Function ◽  
Reservoir Simulator

Summary Many deepwater wells experience steep productivity declines. Some field observations indicate that this decline is partly attributable to fines-migration effects. In this paper, we present a numerical workflow to simulate the effect (over time) of flow-induced fines migration on production decline in deepwater reservoirs. A permeability-reduction function was extracted from long-term coreflood tests and implemented into a reservoir simulator. Using the permeability-reduction function, production degradation caused by fines migration was simulated in a detailed single-well model. From previous research, it was understood that fines migration does not start until the flow velocity is greater than the critical velocity. After many long-term coreflood tests, or extended fines-migration (EFM) tests, we concluded that the permeability damage induced by fines migration is a function of the pore-volume (PV) throughput (fluid volume flowing through the core divided by the PV of the core). To address these observations, the numerical model was updated such that the interstitial flow velocity was tracked in each individual cell. When the interstitial velocity is greater than the critical velocity, the cell's permeability follows the permeability-reduction trend obtained from laboratory data. Validation of the workflow is performed using a cylinder model to match the laboratory test core-plug data. A detailed 3D model was constructed to study the fines-migration effect in each part of the near-wellbore (e.g., perforation, fracture) region and the reservoir. As expected, fines migration started near the perforation where the flow velocity was the highest. Depending on the permeability-decline rate, the production asymptotes eventually reached a constant value after a certain period. Both the decline rate and the ultimate residual permeability had a strong effect on the final production. Sensitivities were run to study the effect of fines migration in different completions. To the authors’ understanding, this is the first time that laboratory-based fines-migration data were incorporated into a reservoir simulator to predict the production decline using experiment-based fines-migration functions. This workflow will help reservoir engineers predict the damage caused by fines migration, predict production decline, and plan for remediation.

Evolution of the Slocan Syncline in south-central British Columbia

1968 ◽  
Vol 5 (4) ◽  
pp. 851-872 ◽  
Author(s):  
John V. Ross ◽  
P. Kellerhals
Keyword(s):  
British Columbia ◽  
Phase 1 ◽  
Granite Gneiss ◽  
Phase 2 ◽  
Phase 3 ◽  
The Core ◽  
South Central ◽  
Deformation Phase ◽  
Facies Metamorphism ◽  
The One

The Slocan Syncline, located in the center of the Kootenay Arc, south-central British Columbia, is outlined in its core by deformed Triassic sediments—the Slocan Group. These deformed sediments were originally deposited unconformably into a synform developed on the upward-facing limb of a recumbent, eastward-closing anticline, comprising Paleozoic and older rocks.The first phase of deformation resulted in the development of a recumbent anticline closing to the east. This anticline involved a sequence of rocks ranging in age from Windermere (late Precambrian—Horsethief Creek Group) up to Permian (Milford Group) and was originally developed along almost horizontal axes contained in an axial-plane having a shallow westerly dip. The core of this anticline contains granite gneiss, having a history pre-dating the deposition of the Horsethief Creek Group, which is in imbricate relation with the gneiss.Later, phase 2 deformation refolded this recumbent anticline into a synform and a westerly complementary antiform along shallow southeasterly axes contained within axial planes dipping southwesterly at about 45 degrees. Amphibolite-facies metamorphism (the "Shuswap Metamorphism") accompanied these phases of deformation and culminated in phase 2 time. Phase 1 and phase 2 deformation and metamorphism ate dated at post-Milford Group (Permian) and pre-Slocan Group (Triassic).Slocan Group (Triassic) sediments were deposited into the phase 2 synform, whose limbs consist of variable older rocks. A later non-metamorphic deformation, phase 3, along southeasterly striking axial planes dipping steeply to the northeast tightened the earlier phase 1 anticline and the phase 2 synform, and produced the Slocan Syncline. The Triassic sediments exhibit only phase 3 structures and are cut by the Nelson batholith dated at 171 × 106 years (Early Jurassic). Phase 3 deformation is then dated at post-Triassic and pre-Early Jurassic.Structural and stratigraphic evidence suggests that the phase 1 recumbent anticline herein described is but one of a set of nappes disposed structurally above and below the one presently described, and that the Kootenay Arc is an old structure perhaps resulting from interference of phase 1 and phase 2 deformations.

Fault zone migration by footwall shortcut and recumbent folding along an inverted fault: example from the Mosha Fault, Central Alborz, Northern Iran

2014 ◽  
Vol 51 (9) ◽  
pp. 825-836 ◽  
Author(s):  
Mohsen Ehteshami-Moinabadi
Keyword(s):  
Fault Zone ◽  
Structural Data ◽  
Field Observations ◽  
The South ◽  
Northern Iran ◽  
South Central ◽  
Major Mode ◽  
Central Alborz ◽  
Southward Migration ◽  
Mosha Fault

The Mosha Fault is a multiply inverted fault in the Central Alborz. Field observations and structural data from this fault show that a footwall shortcut is the major mode of response of this fault to contractional deformation. Although the Mosha Fault is a basement-involved fault, there is no evidence of involvement of basement along its footwall shortcuts, at least in the study area. Footwall shortcuts along this fault vary in size from several hundreds of metres to tens of kilometres, suggesting that a footwall shortcut can be scale independent. It is proposed that footwall shortcuts can also occur as blind thrusts under fault-related folds in the terrains near the major inverted faults. Similar cases also exist in other regions such as Japan. Some large footwall shortcuts may be the causative fault of devastating earthquakes in the active inverted terrains such as the south Central Alborz. Incompetent layers acting as detachments may play an important role in the development of footwall shortcuts. Recumbent folding in the form of a cover nappe in the footwall of the Mosha Fault is another case of southward migration of deformation along the Mosha Fault by which the fault has responded to the Oligo-Miocene compression. This case can be considered as a newly recognized style of deforming structure that occurred along an inverted fault.

A model for the origin of the Lac St. Jean anorthosite massif

1976 ◽  
Vol 13 (2) ◽  
pp. 389-399 ◽  
Author(s):  
R. A. Frith ◽  
K. L. Currie
Keyword(s):  
Experimental Data ◽  
Partial Melting ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Calc Alkaline ◽  
Grenville Province ◽  
Thermal Event ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Potassic Rocks

An ancient tonalitic complex becomes migmatitic around the Lac St. Jean massif, ultimately losing its identity in the high grade metamorphic rocks surrounding the anorthosite. Field relations suggest extreme metamorphism and anatexis of tonalitic rocks. Experimental data show that extensive partial melting of the tonalite leaves an anorthositic residue. The same process operating on more potassic rocks would leave monzonitic or quartz syenitic residues. Synthesis of experimental data suggests that the process could operate at pressures of 5–8 kbar and temperatures of 800–1000 °C, which are compatible with mineral assemblages around the anorthosite massif. Slightly higher temperatures at the end of the process could generate magmatic anorthosite.Application of the model to the Grenville province as a whole predicts generation of anorthosite during a long-lived thermal event of unusual intensity. Residual anorthosite would occur as a substratum in the crust, overlain by high-grade metamorphic rocks intruded by anorthosite and syenitic rocks, while higher levels in the crust would display abundant calc-alkaline plutons and extrusives.

Geophysical characteristics of the continental crust along the Lithoprobe Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT): a review

2002 ◽  
Vol 39 (5) ◽  
pp. 569-587 ◽  
Author(s):  
Jeremy Hall ◽  
Keith E Louden ◽  
Thomas Funck ◽  
Sharon Deemer
Keyword(s):  
Normal Incidence ◽  
Shear Zones ◽  
Canadian Shield ◽  
P Wave ◽  
Seismic Profiles ◽  
Grenville Province ◽  
Core Zone ◽  
The Core ◽  
Geodynamic Processes ◽  
Archean Crust

The Eastern Canadian Shield Onshore–Offshore Transect (ECSOOT) of the Lithoprobe program included 1200 km of normal-incidence seismic profiles and seven wide-angle seismic profiles across Archean and Proterozoic rocks of Labrador, northern Quebec, and the surrounding marine areas. Archean crust is 33–44 km thick. P-wave velocity increases downwards from 6.0 to 6.9 km/s. There is moderate crustal reflectivity, but the reflection Moho is unclear. Archean crust that stabilized in the Proterozoic is similar except for greater reflectivity and a well-defined Moho. Proterozoic crust has similar or greater thickness, variable lower crustal velocities, and strong crustal reflectivity. Geodynamic processes of Paleoproterozoic growth of the Canadian Shield are similar to those observed in modern collisional orogens. The suturing of the Archean Core Zone and Superior provinces involved whole-crustal shearing (top to west) in the Core Zone, linked to thin-skinned deformation in the New Quebec Orogen. The Torngat Orogen sutures the Nain Province to the Core Zone and reveals a crustal root, in which Moho descends to 55 km. It formed by transpression and survived because of the lack of postorogenic heating. Accretion of the Makkovik Province to the Nain Province involves delamination at the Moho and distributed strain in the juvenile arcs. Delamination within the lower crust characterizes the accretion of Labradorian crust in the southeastern Grenville Province. Thinning of the crust northwards across the Grenville Front is accentuated by Mesozoic extension that reactivates Proterozoic shear zones. The intrusion of the Mesoproterozoic Nain Plutonic Suite is attributed to a mantle plume ponding at the base of the crust.

scholarly journals Examining Flexibility in Space Use in Architectural Designs of Public Core Housing Schemes in Anambra State of Nigeria

2021 ◽  
Vol 4 (2) ◽  
pp. 39-85
Author(s):  
Okoye N.B.C.D. ◽  
Onyegiri I. ◽  
Okafor M.
Keyword(s):  
Mixed Method ◽  
Architectural Design ◽  
Space Use ◽  
Housing Affordability ◽  
Field Observations ◽  
Architectural Drawings ◽  
Personal Interview ◽  
Anambra State ◽  
The Core ◽  
Method Approach

Studies indicate flexibility in space use in architectural design as enhancing core housing affordability. Despite this and the notion that intended residents cannot afford core houses, it is not yet documented what constitutes this attribute, and whether they featured in the core house designs. This information, required as a check for future designs, is lacking. Study examined flexibility in space use in architectural designs of existing public core housing schemes in Anambra State, Nigeria, using Mixed Method approach (data sourced from architectural drawings of existing prototypes, field observations and personal interview protocols). Observation schedule with “Yes” and “No” ratings was used in ascertaining reflection of the attribute in each of the 7 prototypes studied. The attribute was found featuring only in 1 out of the 7 prototypes. For affordability improvement, the paper recommends consideration of the variables constituting flexibility in space use in future core housing designs in Anambra State.

scholarly journals The colour analysis method applied to homogeneous rocks

Geologos ◽  
2015 ◽  
Vol 21 (4) ◽  
pp. 233-239
Author(s):  
Amadé Halász ◽  
Ákos Halmai
Keyword(s):  
Radioactive Waste ◽  
Rock Type ◽  
Cost Effective ◽  
Analysis Method ◽  
The Core ◽  
Cost Effective Method ◽  
Natural Gamma ◽  
Computer Aided ◽  
High Level

Abstract Computer-aided colour analysis can facilitate cyclostratigraphic studies. Here we report on a case study involving the development of a digital colour analysis method for examination of the Boda Claystone Formation which is the most suitable in Hungary for the disposal of high-level radioactive waste. Rock type colours are reddish brown or brownish red, or any shade between brown and red. The method presented here could be used to differentiate similar colours and to identify gradual transitions between these; the latter are of great importance in a cyclostratigraphic analysis of the succession. Geophysical well-logging has demonstrated the existence of characteristic cyclic units, as detected by colour and natural gamma. Based on our research, colour, natural gamma and lithology correlate well. For core Ib-4, these features reveal the presence of orderly cycles with thicknesses of roughly 0.64 to 13 metres. Once the core has been scanned, this is a time- and cost-effective method.

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