The Upper Visean Magdalen Islands Basalts of Eastern Quebec, Canada: A Complex Assemblage of Contrasting Mafic Rock Types Erupted in Peak Stages of Transtensional Basin Development above a Mantle Plume

2019 ◽  
Vol 127 (5) ◽  
pp. 505-526
Author(s):  
Pierre Jutras ◽  
Jaroslav Dostal
Keyword(s):  
Mantle Plume ◽  
Mafic Rock ◽  
Rock Types ◽  
Basin Development ◽  
Magdalen Islands

Crustal architecture and tectonic assembly of the Central Gneiss Belt, southwestern Grenville Province, Canada: a new interpretation

2000 ◽  
Vol 37 (2-3) ◽  
pp. 217-234 ◽  
Author(s):  
J WF Ketchum ◽  
A Davidson
Keyword(s):  
Structural Model ◽  
Hanging Wall ◽  
Mafic Rock ◽  
Grenville Province ◽  
The North ◽  
Rock Types ◽  
Structural Barrier ◽  
New Interpretation ◽  
Central Gneiss Belt ◽  
Tectonic Boundary

The Central Gneiss Belt, southwestern Grenville Province, is characterized by parautochthonous crust in the north and allochthonous lithotectonic domains in the south. Despite nearly two decades of study, the basal décollement to allochthonous domains transported from the southeast, known as the allochthon boundary thrust, has not been precisely located throughout much of the belt. Between Lake Nipissing and Georgian Bay where its surface trace is known, it separates 1.24 Ga Sudbury metadiabase in the footwall from eclogite remnants and 1.17-1.15 Ga coronitic olivine metagabbro confined to its hanging wall. On the premise that this relationship can be used to trace the allochthon boundary thrust elsewhere in the Central Gneiss Belt, we have sought to extend the known distribution of these mafic rock types, making use of field, petrographic, and geochemical criteria to identify them. New occurrences of all three mafic types are identified in a region extending from south of Lake Nipissing to western Quebec, and the mutually exclusive pattern of occurrence is maintained within this region. Structural trends and reconnaissance mapping of high-strain zones that appear to represent a structural barrier to the mafic suites suggest that the allochthon boundary thrust lies well to the north of its previously suggested location. Our preferred surface trace for it passes around the southern end of the Powassan batholith and through the town of North Bay before turning east to join up with the Lac Watson shear zone in western Quebec. This suggests that a large segment of "parautochthonous" crust lying north of, and including, the Algonquin domain is in fact allochthonous. The mutually exclusive distribution of the mafic suites points to significant separation of allochthonous and parautochthonous components prior to the Grenvillian orogeny, in accord with models of pre-Grenvillian continental rifting proposed by others. Despite a relative abundance of geological and geochronological data for the Central Gneiss Belt and a mafic rock distribution that appears to successfully locate a major tectonic boundary, we emphasize the need for additional field and laboratory work aimed at testing our structural model.

Correlation of Pore Structure and Permeability by SEM-Image Analysis

1990 ◽  
Vol 48 (1) ◽  
pp. 428-429
Author(s):  
C. A. Callender ◽  
Wm. C. Dawson ◽  
J. J. Funk
Keyword(s):  
Image Analysis ◽  
Pore Structure ◽  
Imaging System ◽  
Pore Space ◽  
Simulation Models ◽  
Image Analyzer ◽  
Imaging Data ◽  
Sem Images ◽  
Thin Sections ◽  
Rock Types

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.Analytical SchemeOur sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.

EVIDENCE OF NEOPROTEROZOIC BACKARC BASIN DEVELOPMENT IN THE CENTRAL RIBEIRA BELT, SOUTHEASTERN BRAZIL: NEW GEOCHRONOLOGICAL AND GEOCHEMICAL CONSTRAINTS FROM THE SÃO ROQUE - AÇUNGUI GROUPS

2000 ◽  
Vol 30 (1) ◽  
pp. 110-114 ◽  
Author(s):  
PETER CHRISTIAN HACKSPACHER ◽  
ELTON LUIZ DANTAS ◽  
ANGELO SPOLADORE ◽  
ALLEN HUTCHESON FETTER ◽  
MARCOS AURÉLIO FARIA DE OLIVEIRA
Keyword(s):  
Southeastern Brazil ◽  
Backarc Basin ◽  
Basin Development ◽  
Geochemical Constraints

Identifikasi Potensi Air Tanah untuk Kebutuhan Penyediaan Air Bersih dengan Metode Geolistrik: Studi Kasus di Kawasan Geostech, Puspiptek Serpong

2020 ◽  
Vol 21 (2) ◽  
pp. 204-212
Author(s):  
Heru Sri Naryanto ◽  
Puspa Khaerani ◽  
Syakira Trisnafiah ◽  
Achmad Fakhrus Shomim ◽  
Wisyanto Wisyanto ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Groundwater Potential ◽  
Clean Water ◽  
Rock Types ◽  
Groundwater Aquifers ◽  
Groundwater Aquifer ◽  
Groundwater Origin ◽  
Laboratory Facility ◽  
Potential Groundwater ◽  
Lower Depth

ABSTRACTGeostech Building, as an office and laboratory facility, requires a source of clean water from groundwater related to the limited supply of clean water from the PDAM. Due to the needs of freshwater from groundwater origin, data and information are needed regarding the potential groundwater in the area, including aquifer configuration, depth, and groundwater potential. The presence of groundwater is not distributed through every area, and it's related to the geological and geohydrological conditions. One of the geophysical methods that can describe subsurface is 2D geoelectric methods. This method can distinguish and analyze rock types, geological structures, groundwater aquifers, and other important information based on the characteristics of the electricity of rocks by looking at the value of the type of resistance. In this measurement, the Wenner Alpha configuration has been used, where the arrangement of A-B current electrodes and M-N potential electrodes have constant spacing. From the measurement results, it can be interpreted that there is a low resistivity layer containing porous groundwater as an aquifer. Based on regional geological data, it has been estimated that this layer is in the form of sandy tuff (0-1.5 ohm-m). The exploitation of groundwater with drilling is expected to reach the aquifer's upper layer at depth, starting from 11.5-13 meters. The groundwater aquifer thickness cannot be ascertained because of the penetration of the lower depth of 2D geoelectric measurements truncated by the constraint of a maximum stretch of cable. The upper layer of the aquifer contains a turned layer of fine tufa and medium tuff, which is impermeable, coarse tuff, and mixed soil with varying thickness at the upper layer.Keywords: 2D geoelectric, aquifer, potential groundwater, Geostech  ABSTRAKGedung Geostech sebagai sarana perkantoran dan laboratorium memerlukan sumber air bersih dari air tanah terkait dengan terbatasnya suplai air bersih dari PDAM. Kebutuhan air bersih berasal dari air tanah, maka diperlukan data dan informasi mengenai kondisi potensi air tanah di kawasan tersebut termasuk konfigurasi akuifer, kedalaman, dan potensi air tanahnya. Keberadaan air tanah tidaklah merata untuk setiap tempat dan sangat terkait dengan kondisi geologi dan geohidrologinya. Salah satu metode geofisika yang dapat memberikan gambaran kondisi bawah permukaan adalah dengan metode geolistrik 2D. Metode ini dapat membedakan dan menganalisis jenis batuan, struktur geologi, akuifer air tanah, dan informasi penting lainnya berdasarkan sifat kelistrikan batuan dengan melihat nilai tahanan jenisnya. Dalam pengukuran ini digunakan konfigurasi Wenner Alpha, dimana susunan elektroda arus A dan B dan elektroda potensial M dan N mempunyai spasi yang konstan. Dari hasil pengukuran dapat diinterpretasikan adanya lapisan dengan resistivitas rendah yang mengandung air tanah dan bersifat porous sebagai akuifer. Berdasarkan data geologi regional diperkirakan lapisan ini berupa tuf pasiran (0-1,5 ohm-m). Pengambilan air tanah dengan pemboran diperkirakan akan mengenai batas atas lapisan akuifer pada kedalaman 11,5-13 meter. Ketebalan akuifer air tanah tidak bisa dihitung karena penetrasi kedalaman pengukuran geolistrik 2D terbatasi oleh bentangan elektroda di permukaan. Lapisan di atas akuifer merupakan lapisan selang-seling tuf halus dan tuf sedang yang kedap air, tuf kasar, dan pada bagian paling atas merupakan tanah urugan dengan ketebalan bervariasi.Kata kunci: Geolistrik 2D, akuifer, potensi air tanah, Geostech  

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