Overprinting of early, redistributed Fe and Pb–Zn mineralization by late-stage Au–Ag–Cu deposition at the Dumagami mine, Bousquet district, Abitibi, Quebec

1990 ◽  
Vol 27 (12) ◽  
pp. 1651-1671 ◽  
Author(s):  
P. Marquis ◽  
C. Hubert ◽  
A. C. Brown ◽  
D. M. Rigg
Keyword(s):  
Hydrothermal Alteration ◽  
Narrow Band ◽  
Early Stage ◽  
Hydrothermal Activity ◽  
Structural Features ◽  
White Mica ◽  
Ductile Deformation ◽  
Sulphide Mineralization ◽  
Abitibi Greenstone Belt ◽  
Two Stages

The Dumagami Au–Ag–Cu deposits are hosted by strongly deformed and altered Archean felsic metavolcanites of the Blake River Group (BRG), southern Abitibi greenstone belt, Canada. Textural and structural features recorded within the lithologies of the BRG at Dumagami indicate that two stages of hydrothermal alteration, separated by a dynamometamorphic event, have affected the volcanic protoliths in the deposit area. Advanced argillic and sericitic alteration zones, massive pyrite bodies, and massive sphalerite–galena bodies resulted from the first stage of hydrothermal activity. Sericitic shells surround peraluminous cores, which host the massive pyrite bodies and massive sphalerite–galena bodies within the altered zones.This early-stage alteration was followed by a dynamometamorphic event that reached the greenschist–amphibolite grade and almost completely recrystallized both fresh and altered rocks and the enclosed massive sulphide bodies. White-mica schists and andalusite–kyanite schists represent the dynamometamorphic equivalents of the earlier sericitic and advanced argillic zones. Mesoscopic and microscopic structures and textures attest to the ductile behaviour of the massive pyrite bodies during this deformation and accompanying metamorphism.Portions of the deformed and metamorphosed altered zones are characterized by a late cataclastic deformation and by the development of fractures postdating the ductile deformation. The late hydrothermal alteration is concentrated within these cataclastic rocks and is characterized by the retrogression of the greenschist–amphibolite assemblages. Andalusite and kyanite are replaced by diaspore, kaolinite, and pyrophyllite assemblages, and pyrite is replaced by chalcopyrite–gold, chalcopyrite–bornite–gold, and bornite–stromeyerite assemblages. The concentration of the pre-dynamometamorphic alteration and sulphide mineralization within a narrow band along the southern BRG could indicate that this part of the BRG was the locus of a major Archean synvolcanic fault zone.

Structural deformation-metamorphism and exhumation processes of Yuanmou metamorphic complex, Yunnan, China

2021 ◽  
Author(s):  
Xuemei Cheng ◽  
Shuyun Cao
Keyword(s):  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Early Stage ◽  
Structural Features ◽  
Detachment Fault ◽  
Ductile Deformation ◽  
Structural Deformation ◽  
Subsequent Stage ◽  
Metamorphic Complex ◽  
South Central

<p>Within orogenic zone and continental extensional area, it often developed metamorphic complex or metamorphic gneiss dome that widely exposed continental mid-lower crustal rocks, which is an ideal place to study exhumation processes of deep-seated metamorphic complex and rheology. The Yuanmou metamorphic complex is located in the south-central part of the "Kangdian Axis" in the western margin of Qiangtang Block and Yangtze Block, which is a part of the anticline of the Sichuan-Yunnan platform. Many research works mainly focus on the discussion of intrusion ages, aeromagnetic anomalies, and polymetallic deposits. However, the exhumation process and mechanism of the Yuanmou metamorphic complex are rarely discussed and still unclear. This study, based on detailed field geological observations, optical microscopy (OM), cathodoluminescence (CL), electron backscatter diffraction (EBSD) and electron probe (EMPA) were performed to illustrate the geological structure features, deformation-metamorphic evolution process and its tectonic significance of Yuanmou metamorphic complex during the exhumation process. All these analysis results indicate that the Yuanmou metamorphic complex generally exhibits a dome structure with deep metamorphic rocks and deformed rocks of varying degrees widely developed. Mylonitic gneiss and granitic intrusions are located in the footwall of the Yuanmou, which have suffered high-temperature shearing. The mylonitic fabrics and mineral stretching lineations in the deformed rock are strongly developed, forming typical S-L or L-shaped structural features. The high-temperature ductile deformation-metamorphism environment is high amphibolite facies, that is, the temperature range is between 620 ~ 690 ℃ and the pressure is between 0.8 ~ 0.95 Gpa. In the deformed rocks closed to the detachment fault, some of the mylonite fabric features are retained, but most of them have experienced a strongly overprinted retrogression metamorphism and deformation. At the top of the detachment fault zone, it is mainly composed of cataclasites and fault gouge. The comprehensive macro- and microstructural characteristics, geometry, kinematics, and mineral (amphibole, quartz and calcite) EBSD textures indicate that the Yuanmou metamorphic complex has undergone a progressive exhumation process during regional extension, obvious high-temperature plastic deformation-metamorphism in the early stage, and superimposed of low-temperature plastic-brittle and brittle deformation in the subsequent stage, which is also accompanied by strong fluid activities during the exhumation process.</p>

scholarly journals High Fat Diet Induces Adhesion of Platelets to Endothelium in Two Models of Dyslipidemia

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Jaime Gonzalez ◽  
Wendy Donoso ◽  
Natalia Díaz ◽  
María Eliana Albornoz ◽  
Ricardo Huilcaman ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Early Stage ◽  
Endothelial Activation ◽  
Mice Model ◽  
High Fat ◽  
Early Stages ◽  
Endothelial Surface ◽  
Two Stages ◽  
Adhesion Of Platelets

Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE−/−mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE−/−mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cellsin vivo. These findings support studying the participation of platelets in the formation of atheromatous plate.

Narrow-band UVB in the treatment of early stage mycosis fungoides: report of 16 patients

2005 ◽  
Vol 30 (4) ◽  
pp. 376-378 ◽  
Author(s):  
S. Z. Ghodsi ◽  
Z. Hallaji ◽  
K. Balighi ◽  
F. Safar ◽  
C. Chams-Davatchi
Keyword(s):  
Mycosis Fungoides ◽  
Narrow Band ◽  
Early Stage

scholarly journals Observations on the Nutrition of Maggots of Australian Blow-Flies

1933 ◽  
Vol 10 (3) ◽  
pp. 237-246
Author(s):  
M. J. MACKERRAS ◽  
M. R. FRENEY
Keyword(s):  
Early Stage ◽  
Wool Fibre ◽  
Initial Growth ◽  
Full Development ◽  
Adequate Food ◽  
Acid Reaction ◽  
Keratin Hydrolysis ◽  
The Moment ◽  
The Masses ◽  
Two Stages

1. Larvae of L. cuprina and Ch. rufifacies are capable of liquefying and digesting protein media without the intervention of bacteria. Both species and L. sericata secrete tryptic and peptic enzymes and at least L. cuprina does so from the moment of hatching. Tryptase is more abundant than peptase. Predatory activity, though a normal habit of Ch. rufifacies, is not necessary for any of these species and did not occur in the masses of Lucilia larvae used for extraction of the enzymes, although they were kept for periods up to 24 hours without food. 2. Partial development of larvae occurred in sheep dung, faeces-stained wool and in the products of keratin hydrolysis. Complete development took place in wool containing a "gummy crust" of dried exudate and in some samples of faeces-stained wool. Some of the samples of faeces-stained wool and those containing a "crust" have been demonstrated serologically by Dr I. M. Mackerras to have an increased content of soluble sheep protein as compared with normal wool. A marked increase of soluble protein has been demonstrated in struck wool both chemically and serologically. 3. Moisture, warmth, shelter and aeration are essential physical conditions for larval development. In addition, an alkaline reaction is relatively favourable and an acid reaction relatively unfavourable. 4. There are normally two stages in the development of a primary strike, the first stage being from hatching up to the time the larvae attack the skin, the outer layer or epidermis of which is approximately 36µ thick (Whitnall, 1931). During this stage they must feed, if at all, on materials already present. The second stage is from the commencement of an actual skin lesion up to full development of the maggots. During this stage there is a more or less copious serous exudation, which has been shown to be an adequate food for the full development of the maggots. Faeces-staining, presence of exudate due to a prior lesion, and products of wool hydrolysis have been shown to be adequate to carry the larvae through the first stage. Wool hydrolysis on the living sheep is probably not an important factor, judging by an examination of wool samples, but we have isolated organisms which, when growing on a nutrient medium, are capable of disintegrating wool fibre. 5. The rôle of bacterial activity in strike is complex and appears to be substantially as follows: (a) to produce substances which attract the flies and stimulate them to oviposit; (b) to provide food for the initial growth of the maggots, either by rendering assimilable the inert proteins, or by causing a skin reaction with a serous exudation. 6. The immediate work for the future is a more exact determination of: (a) the nature of the food of the larvae in the early stage of growth on the living sheep; (b) the factors which influence its production; and (c) the mechanism by which the larvae invade the skin.

Barrovian-type metamorphism in the western domain of the Cordillera Darwin Metamorphic Complex, Fuegian Andes

2021 ◽  
Author(s):  
Mauricio Calderon ◽  
Catalina Zúñiga ◽  
Francisco Hervé ◽  
Thomas Theye ◽  
Gonzalo Galaz ◽  
...  
Keyword(s):  
Geothermal Gradient ◽  
White Mica ◽  
Burial Depth ◽  
Metamorphic Complex ◽  
Constant Composition ◽  
Magmatic Arc ◽  
Garnet Core ◽  
Late Generation ◽  
Si Content ◽  
Two Stages

<p>The Cordillera de Darwin Metamorphic Complex (CDMC) comprise metamorphosed supracrustal rocks and metaplutonic suites which records a unique tectonic evolution among the metamorphic complexes of the southernmost Andes. The pressure (P) and temperature (T) conditions determined in garnet-bearing schists in the Central Domain of the CDMC indicate a clockwise P-T path of metamorphism reaching burial depth as high as 12 kbar at ca. 620°C. This metamorphic event has been related to the closure of a marginal back-arc basin (Rocas Verdes Basin) and collision of an ensialic magmatic arc with the continent in the late Cretaceous. We focus on garnet-biotite schists intercalated within a huge block consisting of repeated sequences of metabasalts and amphibolites (Rocas Verdes Ophiolites), located in the Western Domain of the CDMC, at Seno Martínez. The chemical zonation of small garnet porphyroblasts (diameter of ca. 300 um) record two stages of metamorphism. Garnet is almost almandine in composition with lesser amounts of Ca, Mn and Mg.  The concentric zonation is characterized by relatively lower contents of Fe-Mg and higher contents of Ca-Mn in the core. Garnet bear tiny inclusions of clinozoisite, which is also present as isolated grains in the foliated matrix. Laths of biotite define the main foliation and have a nearly constant composition characterized by X<sub>Fe</sub> of ca. 0.6. Two generations of phengitic white mica are identified on basis of Si content (a.pf.u.) varying between 3.20-3.30 (early generation) and of ca. 3.15 (late generation). To reconstruct the P-T conditions of metamorphism through thermodynamic modeling using the Perple_X software package, the bulk rock and mineral composition were considered. Using compositional isopleths of X<sub>Fe</sub>, X<sub>Mg</sub>, X<sub>Ca</sub> and X<sub>Mn</sub> in zoned garnet, Si content in white mica and X<sub>Fe</sub> in biotite allow the constrain two stages of metamorphism (M1 and M2). The P-T conditions of M1, represented by the composition of the garnet core, are restricted to ca. 8 kbar and 400°C. M2 is restricted to ca. 7.5 kbar at 480°C, determined with the composition of the garnet rim, X<sub>Fe</sub> in biotite and Si content in late phengitic white mica. Our preliminary results indicate that ophiolitic rocks and interleaved garnet-bearing schists were tectonically buried and metamorphosed in a relatively hot subduction interface characterized by a geothermal gradient of ca. 16°C/km, prior to the collision of the ensialic magmatic arc. Acknowledgements. This study was supported by the Fondecyt grant 1161818.</p>

Geology, Structural Analysis, and Paragenesis of the Arrow Uranium Deposit, Western Athabasca Basin, Saskatchewan, Canada: Implications for the Development of the Patterson Lake Corridor

2020 ◽  
Author(s):  
Sean Hillacre ◽  
Kevin Ansdell ◽  
Brian McEwan
Keyword(s):  
Structural Analysis ◽  
Uranium Deposit ◽  
Regional Scale ◽  
Structural Features ◽  
White Mica ◽  
Uranium Mineralization ◽  
Fault System ◽  
Thin Sections ◽  
Athabasca Basin ◽  
Quartz Veins

Abstract Recent significant discoveries of uranium mineralization in the southwestern Athabasca basin, northern Saskatchewan, Canada, have been associated with a series of geophysical conductors along a NE- to SW-trending structural zone, termed the Patterson Lake corridor. The Arrow deposit (indicated mineral resource: 256.6 Mlb U3O8; grade 4.03% U3O8) is along this trend, hosted exclusively in basement orthogneisses of the Taltson domain, and is the largest undeveloped uranium deposit in the basin. This study is the first detailed analysis of a deposit along this corridor and examines the relationships between the ductile framework and brittle reactivation of structures, mineral paragenesis, and uranium mineralization. Paragenetic information from hundreds of drill core samples and thin sections was integrated with structural analysis utilizing over 18,000 measurements of various structural features. The structural system at Arrow is interpreted as a partitioned, strike-slip–dominated, brittle-ductile fault system of complex Riedel-style geometry. The system developed along subvertical, NE- to SW-trending dextral high-strain zones formed syn- to post-D3 deformation, which were the focus of extensive premineralization metasomatism (quartz flooding, sericitization, chloritization), within the limb domain of a regional-scale fold structure. These zones evolved through post-Athabasca dextral and sinistral reactivation events, creating brittle fault linkages and dilation zones, allowing for hydrothermal fluid migration and resulting uraninite precipitation and associated alteration (white mica, chlorite, kaolinite, hematite, quartz veins). This study of the structural context of Arrow is important as it emphasizes that protracted reactivation of deep-seated structures and their subsidiaries was a fundamental control on uranium mineralization in the southwestern Athabasca basin.

Geological evolution of the Manitouwadge greenstone belt and Wawa-Quetico subprovince boundary, Superior Province, Ontario, constrained by U-Pb zircon dates of supracrustal and plutonic rocks

1999 ◽  
Vol 36 (6) ◽  
pp. 945-966 ◽  
Author(s):  
Eva Zaleski ◽  
Otto van Breemen ◽  
Virginia L Peterson
Keyword(s):  
Hydrothermal Alteration ◽  
Greenstone Belt ◽  
Boundary Region ◽  
Detrital Zircons ◽  
Ductile Deformation ◽  
Superior Province ◽  
Geological Evolution ◽  
Hydrothermal Alteration Zones ◽  
Depositional Age ◽  
East West

Fifty million years of Archean evolution is recorded in the Manitouwadge greenstone belt and the Wawa-Quetico boundary region, from ca. 2720 Ma volcanism and subvolcanic plutonism associated with massive sulphide deposits and hydrothermal alteration zones, to 2689-2687 Ma and 2680-2677 Ma synkinematic plutonism. In the greenstone belt, greywackes were deposited after 2693 Ma, post-dating local volcanism by at least 25 Ma, and requiring that the volcanic-sedimentary contact is an unconformity or a fault. In migmatitic greywackes in the Quetico subprovince, detrital zircons limit the depositional age to <2690 Ma, permitting correlation of greywackes across the Wawa-Quetico subprovince boundary. Upward-facing inclined F2 folds that deform the volcanic-sedimentary contact are bracketed by the 2687 ± 2 Ma Loken Lake pluton, which shows strong D2 fabrics, and by 2680+4-3 Ma foliated granite which cuts D2 fabrics. Dextral transpression producing regional F3 folds and the overall east-west trends of the Wawa-Quetico boundary region post-dated the 2680 ± 2 Ma Nama Creek pluton. Field relationships and isotopic ages support correlation of greywackes across the subprovince boundary, and demonstrate that most or all of the ductile deformation post-dated sedimentation. Ductile structures, especially those associated with dextral transpression, are not directly related to juxtaposition of the Wawa and Quetico subprovinces, as these were already contiguous, either through sedimentation on a volcanic substrate or as a result of earlier cryptic structures. Our results imply that the belt-like configuration of the subprovinces, emphasized in accretionary models of the Superior Province, is a relatively late feature that overprints older, tectonically significant structures.

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