Paleomagnetism of the Flin Flon – Snow Lake Greenstone Belt, Manitoba and Saskatchewan

1975 ◽  
Vol 12 (8) ◽  
pp. 1272-1290 ◽  
Author(s):  
J. K. Park
Keyword(s):  
Greenstone Belt ◽  
Amphibolite Facies ◽  
Retrograde Metamorphism ◽  
General Direction ◽  
Thermoremanent Magnetization ◽  
Flin Flon ◽  
K 12 ◽  
Very High

The Flin Flon – Snow Lake greenstone belt is of Archean or Aphebian age and has been metamorphosed to greenschist or low amphibolite facies during the Hudsonian orogeny. It contains four rock units — the Amisk Group, the Missi Group, metadiorite and metagabbro bodies, and the Boundary Intrusions. The rocks contain two main magnetizations, an early B magnetization and a later A magnetization. Both magnetizations contain reversals. The A magnetization (43 sites, direction 168°, +73°, k = 17, α95 = 5°, pole 24°N, 095°W) is found in all rock units. It can be divided into three parts (1, 2 and 3) which have the same general direction, but which are significantly different from one another. It is suggested that A1 is a viscous partial thermoremanence (vptrm), and A2 possibly a chemical remanence (crm). Both are considered to have been acquired during uplift (1600–1700 m.y.) following the Hudsonian orogeny. A3 is possibly a crm acquired during late fault movements and appears to be carried by hematite developed during retrograde metamorphism. A3 is considered to be about 1600 m.y. old. The B magnetization (7 sites, 129°, +04°, k = 12, α95 = 18°, pole 20°S, 046°W) occurs in all rock units except the Missi. It is particularly well developed in the Boundary Intrusions where it is considered to be a primary thermoremanent magnetization (trm). In other rock units B is considered to be a vptrm acquired during heating at the time of emplacement of the Boundary Intrusions. The B magnetization is considered to be about 1800 m.y. old. Some enigmatic magnetizations with very high blocking temperatures above 700 °C were observed. Formulas for calculating the coercivities in rocks with more than one magnetization are given.

Superimposed Deformations in the Missi Meta-sedimentary Rocks near Flin Flon, Manitoba

1971 ◽  
Vol 8 (2) ◽  
pp. 217-242 ◽  
Author(s):  
Mel R. Stauffer ◽  
Amar Mukherjee
Keyword(s):  
Sedimentary Rocks ◽  
Greenschist Facies ◽  
Axial Plane ◽  
Small Scale ◽  
Second Phase ◽  
Retrograde Metamorphism ◽  
High Angle ◽  
South Side ◽  
Flin Flon

Within the Flin Flon Basin, Precambrian meta-sandstones and conglomerates belonging to the Missi Group have been complexly deformed as a result of three periods of deformation. The first two periods (P1 and P2) involved folding but no apparent faulting, the last (P3) involved both folding and faulting. Progressive metamorphism (M2), within the greenschist facies, occurred during the second phase (P2) and aided in the formation of a pronounced axial-plane foliation (S2). Small-scale folding and retrograde metamorphism (M3) occurred along faults formed during the last phase (P3).The faults in this area all appear to be high angle, oblique-slip reverse faults and can be interpreted as having formed during a single orogenic event (P3) although there is sequence in their initiation. The net-slip directions of different faults are approximately the same, and plunge moderately to the southeast, with either the east or south side upthrown, depending on the attitude of the fault.

Application of various fuzzy inference networks to integrate mineral exploration datasets: Implication for gold prospectivity mapping in Sonakhan greenstone belt, India

2020 ◽  
Author(s):  
Satyabrata Behera ◽  
Mruganka Kumar Panigrahi
Keyword(s):  
Fuzzy Logic ◽  
Greenstone Belt ◽  
Fuzzy Inference ◽  
Mineral Exploration ◽  
Quantitative Information ◽  
Mineral Deposits ◽  
Target Area ◽  
Science Data ◽  
Very High ◽  
Prospectivity Mapping

<p>            Fuzzy modelling of multisource geoscience data and its implications to mineral prospectivity mapping is drawing wide attention of the mineral exploration sector. Mineral deposits are basically end products resulted from optimal combination of certain metallogenetically favourable earth processes which leave their imprints in the associated geological entities at a range of scales that can be interpreted from their direct or indirect manifestation in several geospatial datasets. Therefore, in geologically potential yet under-explored or greenfield areas with no or very few discovered mineral deposits, the qualitative knowledge on the spatial relationship between mineralisation of interest and geoscience data could be an important guide to delineate exploration targets. In such a case, fuzzy set theory aided with Geographic Information System (GIS) is preferred as an effective mechanism for the transformation of subjective knowledge into quantitative information that further helps in modelling of earth science data.</p><p>            The Archaean to Paleo-proterozoic Sonakhan Greenstone Belt (SGB) located in the north-eastern fringe of the Baster Craton in central India is considered as a potential geological terrane for mesothermal gold mineralisation based on its geological and geochemical similarities with other mineralised greenstone belts. In this case study, a part of SGB has been taken as a target area that exposes sequence of metamorphosed mafic to ultramafics rocks and associated metasedimentary units in a gneissic country and younger granites. Since the study area represents a less explored terrane in terms of mineralisation, the objective of this research is to generate gold prospectivity maps using fuzzy logic modelling. A total of 17 multiclass evidential maps were generated using four independent geoscience datasets viz. geological, geochemical, geophysical, and remote sensing. The sources of data include existing databases from the Geological Survey of India (GSI) and published work along with the newly produced exploratory data in this research. Fuzzy membership values (0-1) were assigned to each class of evidential maps based on subjective judgement. The fuzzyfied evidential maps were then combined using fuzzy operators (AND, OR, SUM, PRODUCT, and GAMMA) through a series of logical steps i.e. the fuzzy inference network. Two different fuzzy inference networks were created using several combinations of fuzzy operations and accordingly, two prospectivity maps resulted which were classified as very high, high, moderate, low, very low favourable zones. To further enhance the result, the two maps were intersected to produce the final gold prospectivity map in support of targeting gold exploration in the region. A part of the study area, that is the Baghmara gold block, that was already identified as a gold enriched block based on traditional exploration works, coincides with the very high to high favourable zones predicted in the final map and this ensures the reliability of the gold prospectivity map and the efficiency of the adopted fuzzy logic approach in delineating promising targets for exploration.</p>

Hydrothermal Alteration Mineralogy and Geochemistry of the Archean World-Class Canadian Malartic Disseminated-Stockwork Gold Deposit, Southern Abitibi Greenstone Belt, Quebec, Canada

2019 ◽  
Vol 114 (6) ◽  
pp. 1057-1094 ◽  
Author(s):  
Stéphane De Souza ◽  
Benoît Dubé ◽  
Patrick Mercier-Langevin ◽  
Vicki McNicoll ◽  
Céline Dupuis ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Gold Mineralization ◽  
Amphibolite Facies ◽  
Alteration Zone ◽  
Gold Deposition ◽  
Abitibi Greenstone Belt ◽  
World Class

Abstract The Canadian Malartic stockwork-disseminated gold deposit is an Archean world-class deposit located in the southern Abitibi greenstone belt. It contains over 332.8 tonnes (t; 10.7 Moz) of Au at a grade of 0.97 ppm, in addition to 160 t (5.14 Moz) of past production (1935–1981). Although the deposit is partly situated within the Larder Lake-Cadillac fault zone, most of the ore occurs up to ~1.5 km to the south of the fault zone. The main hosts of the mineralized zones are greenschist facies turbiditic graywacke and mudstone of the Pontiac Group (~2685–2682 Ma) and predominantly subalkaline ~2678 Ma porphyritic quartz monzodiorite and granodiorite. These intrusions were emplaced during an episode of clastic sedimentation and alkaline to subalkaline magmatism known as the Timiskaming assemblage (<2680–2670 Ma in the southern Abitibi). The orebodies define two main mineralized trends, which are oriented subparallel to the NW-striking S2 cleavage and the E-striking, S-dipping Sladen fault zone. This syn- to post-D2 ductile-brittle to brittle Sladen fault zone is mineralized for more than 3 km along strike. The ore mainly consists of disseminated pyrite in stockworks and replacement zones, with subordinate auriferous quartz veins and breccia. Gold is associated with pyrite and traces of tellurides defining an Au-Te-W ± Ag-Bi-Mo-Pb signature. The orebodies are zoned outward, and most of the higher-grade (>1 ppm Au) ore was deposited as a result of iron sulfidation from silicates and oxides and Na-K metasomatism in carbonatized rocks. The alteration footprint comprises a proximal alteration envelope (K- or Na-feldspar-dolomite-calcite-pyrite ± phlogopite). This proximal alteration zone transitions to an outer shell of altered rocks (biotite-calcite-phengitic white mica), which hosts sub-ppm gold grades and reflects decreasing carbonatization, sulfidation, and aNa+/aH+ or aK+/aH+ of the ore fluid. Gold mineralization, with an inferred age of ~2664 Ma (Re-Os molybdenite), was contemporaneous with syn- to late-D2 peak metamorphism in the Pontiac Group; it postdates sedimentation of the Timiskaming assemblage along the Larder Lake-Cadillac fault zone (~2680–2669 Ma) and crystallization of the quartz monzodiorite. These chronological relationships agree with a model of CO2-rich auriferous fluid generation in amphibolite facies rocks of the Pontiac Group and gold deposition in syn- to late-D2 structures in the upper greenschist to amphibolite facies. The variable geometry, rheology, and composition of the various intrusive and sedimentary rocks have provided strain heterogeneities and chemical gradients for the formation of structural and chemical traps that host the gold. The Canadian Malartic deposit corresponds to a mesozonal stockwork-disseminated replacement-type deposit formed within an orogenic setting. The predominance of disseminated replacement ore over fault-fill and extensional quartz-carbonate vein systems suggests that the mineralized fracture networks remained relatively permeable and that fluids circulated at a near-constant hydraulic gradient during the main phase of auriferous hydrothermal alteration.

Tectonic stacking of metamorphic zones in Cheticamp River area, Cape Breton Highlands, Nova Scotia

1984 ◽  
Vol 21 (11) ◽  
pp. 1229-1244 ◽  
Author(s):  
D. Craw
Keyword(s):  
High Strain ◽  
Amphibolite Facies ◽  
Lower Limbs ◽  
Low Grade ◽  
Metamorphic Peak ◽  
Cape Breton ◽  
Gneiss Complex ◽  
Show Evidence ◽  
Penetrative Foliation ◽  
Very High

Metabasic and quartzo-feldspathic schists and gneisses of the Cheticamp River area can be subdivided into three north–south-trending metamorphic belts. The westernmost belt, the low-grade belt, has been metamorphosed to transitional greenschist–amphibolite facies with development of one penetrative foliation. The central medium-grade belt has been metamorphosed to amphibolite facies with development of two penetrative foliations. The eastern high-grade belt has been metamorphosed to amphibolite facies accompanied by development of strong gneissic segregation and nonanatectic migmatite leucosomes during formation of two penetrative foliations.Deformation has been inhomogeneous in each of these belts. Most rocks in each belt show evidence of post-tectonic porphyroblast growth. However, deformation continued after the metamorphic peak in localized zones. Very high strain occurred in many of these zones during and after the metamorphic peak, so that early formed fold axes were rotated towards the stretching direction. Locally, dynamically recrystallized mylonite has formed. The three belts were juxtaposed under waning metamorphic conditions by relative movement on these high-strain zones. The schist and gneiss complex thus consists of stacked metamorphic zones with the lowest grade rocks lying at the bottom of the stack. Stacking occurred by east to west thrusting of tight macroscopic ductile folds whose lower limbs have been sheared off.There are many lithologic similarities between the three metamorphic belts. The rocks may have been derived from the same protolith and have since been variably deformed and metamorphosed before later juxtaposition. There is no evidence for involvement of an older "basement complex" in the stacking tectonics in the studied area.The schist and gneiss complex has been intruded by post-tectonic plutonic rocks, and locally affected by post-metamorphic brittle deformation.

U–Pb evidence of late Archean tectono-thermal activity in the southern São Francisco shield, Brazil

1992 ◽  
Vol 29 (11) ◽  
pp. 2341-2346 ◽  
Author(s):  
N. Machado ◽  
M. Carneiro
Keyword(s):  
South America ◽  
Greenstone Belt ◽  
Granite Gneiss ◽  
Amphibolite Facies ◽  
Thermal Activity ◽  
Metamorphic Complex ◽  
Zircon Core ◽  
Eastern Brazil ◽  
Quadrilátero Ferrífero ◽  
Minimum Age

The São Francisco craton in eastern Brazil is one of the major shield areas in South America. In the Quadrilátero Ferrífero area (southern sector of the craton) the Archean Rio das Velhas greenstone belt is surrounded by granite–gneiss terrane and is overlain by Proterozoic sedimentary successions. The Bonfim Metamorphic Complex is the only area of the granite–gneiss terrane adjacent to the greenstone belt that has been mapped. It comprises two gneissic units, tonalites, and late granitic dykes, which crosscut the regional north–south shear fabric. Samples of gneiss, two tonalites and a granitic dyke were dated by U–Pb. A zircon core from the Alberto Flores gneiss yielded a minimum age of 2920 Ma, whereas the overgrowth is concordant at 2772 ± 6 Ma. Two tonalites from the vicinity of Serra da Moeda are [Formula: see text] old, and a late dyke yielded an age of [Formula: see text]. These data, together with previously published U–Pb ages, show that (i) greenstone belt volcanism was coeval with granitoid intrusion and with metamorphism of older units in the granite–gneiss terrane at ca. 2780 Ma and (ii) the main crust-forming event in the Quadrilátero Ferrífero area is about 2780 Ma old. Clear evidence is now available indicating that older magmatism is 2.8–3.2 Ga old. In addition, the last Archean deformation must have occurred in the interval 2780–2703 Ma. Finally, the presence of 2774 ± 6 Ma titanite in the tonalites indicates that the metamorphism associated with the Trans-Amazonian orogeny (ca. 2.0 Ga) did not reach amphibolite facies in the study area.

scholarly journals Implicating the Glutathione-Gated Potassium Efflux System as a Cause of Electrophile-Induced Activated Sludge Deflocculation

2004 ◽  
Vol 70 (9) ◽  
pp. 5569-5578 ◽  
Author(s):  
Charles B. Bott ◽  
Nancy G. Love
Keyword(s):  
Activated Sludge ◽  
Causal Mechanism ◽  
Potassium Efflux ◽  
Shock Loads ◽  
Floc Structure ◽  
High K ◽  
Pure Cultures ◽  
K 12 ◽  
Microbial Stress ◽  
Very High

ABSTRACT The glutathione-gated K+ efflux (GGKE) system represents a protective microbial stress response that is activated by electrophilic or thiol-reactive stressors. It was hypothesized that efflux of cytoplasmic K+ occurs in activated sludge communities in response to shock loads of industrially relevant electrophilic chemicals and results in significant deflocculation. Novosphingobium capsulatum, a bacterium consistent with others found in activated sludge treatment systems, responded to electrophilic thiol reactants with rapid efflux of up to 80% of its cytoplasmic K+ pool. Furthermore, N. capsulatum and activated sludge cultures exhibited dynamic efflux-uptake-efflux responses very similar to those observed by others in Escherichia coli K-12 exposed to the electrophilic stressors N-ethylmaleimide and 1-chloro-2,4-dinitrobenzene and the reducing agent dithiothreitol. Fluorescent LIVE/DEAD stains were used to show that cell lysis was not the cause of electrophile-induced K+ efflux. Nigericin was used to artificially stimulate K+ efflux from N. capsulatum and activated sludge cultures as a comparison to electrophile-induced K+ efflux and showed that cytoplasmic K+ efflux by both means corresponded with activated sludge deflocculation. These results parallel those of previous studies with pure cultures in which GGKE was shown to cause cytoplasmic K+ efflux and implicate the GGKE system as a probable causal mechanism for electrophile-induced, activated sludge deflocculation. Calculations support the notion that shock loads of electrophilic chemicals result in very high K+ concentrations within the activated sludge floc structure, and these K+ levels are comparable to that which caused deflocculation by external (nonphysiological) KCl addition.

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