Role of Fluid State Mobilization during Metamorphism of the Henderson Ore Bodies, Chibougamau, Quebec, Canada

1975 ◽  
Vol 12 (9) ◽  
pp. 1516-1523 ◽  
Author(s):  
Jayanta Guha ◽  
Jahak Koo
Keyword(s):  
Shear Zone ◽  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Fluid State ◽  
Ore Bodies ◽  
Calcite Veins ◽  
Intense Deformation ◽  
State Mobilization

The Henderson Cu-Au deposit occurs in discordant structures within the anorthosite zone of the Doré Lake Complex. The Doré Lake Complex is intruded into volcanic rocks of the Chibougamau greenstone belt on the southeastern side of the Superior Province. Massive to disseminated sulfide ores are associated with sericite, carbonate, chlorite and/or chloritoid schists within a large 'shear zone'. These ores show structural and textural evidence of intense deformation, recrystallization, and metamorphic mobilization.The deposit comprises not only sulfide schist ore with alternating sulfide and schist layers, but also 'hydrothermal' vein-type segregation ore. The latter is characterized by sulfide-bearing quartz-calcite veins that occur in the 'shear zone' and in the subsidiary fractures adjacent to it.The sulfide schist and vein types of ores can be attributed to partly solid state mobilization combined with fluid state mobilization from a pre-existing ore, and is an excellent example of extensive fluid state mobilization of sulfides under relatively low-grade regional metamorphism. It is suggested that fluid state mobilization can play an important role during the metamorphism of a pre-existing sulfide body, especially in the presence of differential stress accompanied with rupture. The deformational features of the ore are the important indication for syn- and/or pre-metamorphic origin of the ore.

scholarly journals Geological and geochemical implications of the genesis of the Qolqoleh orogenic gold mineralisation, Kurdistan Province (Iran)

Geologos ◽  
2015 ◽  
Vol 21 (1) ◽  
pp. 31-57 ◽  
Author(s):  
Batoul Taghipour ◽  
Farhad Ahmadnejad
Keyword(s):  
Shear Zone ◽  
Early Stage ◽  
Hanging Wall ◽  
Regional Metamorphism ◽  
Shear Zones ◽  
Northwestern Part ◽  
Type I ◽  
Two Phase ◽  
Mean Values ◽  
Calcite Veins

Abstract The Qolqoleh gold deposit is located in the northwestern part of the Sanandaj-Sirjan Zone (SSZ), within the NE-SW trending Qolqoleh shear zone. Oligocene granitoids, Cretaceous meta-limestones, schists and metavolcanics are the main lithological units. Chondrite-normalised REE patterns of the ore-hosting metavolcanics indicate REE enrichment relative to hanging wall (chlorite-sericite schist) and footwall (meta-limestone) rocks. The pattern also reflects an enrichment in LREE relative to HREE. It seems that the LREE enrichment is related to the circulation of SO42- and CO2-bearing fluids and regional metamorphism in the Qolqoleh shear zone. Both positive and negative Eu anomalies are observed in shear-zone metavolcanics. These anomalies are related to the degree of plagioclase alteration during gold mineralisation and hydrothermal alteration. In progressing from a metavolcanic protomylonite to an ultramylonite, significant changes occurred in the major/trace element and REE concentration. Utilising an Al-Fe-Ti isocon for the ore-hosting metavolcanics shows that Sc, Y, K, U, P, and M-HREE (except Eu) are relatively unchanged; S, As, Ag, Au, Ca, LOI, Rb and LREE are enriched, and Sr, Ba, Eu, Cr, Co and Ni decrease with an increasing degree of deformation. Based on geochemical features and comparison with other well-known shear zones in the world, the study area is best classified as an Isovolume-Gain (IVG) type shear zone and orogenic type gold mineralisation. Based on the number of phases observed at room temperature and their microthermometric behaviour, three fluid inclusion types have been recognised in quartz-sulphide and quartz-calcite veins: Type I monophase aqueous inclusions, Type II two-phase liquid-vapour (L-V) inclusions which are subdivided into two groups based on the homogenisation temperature (Th): a) L-V inclusions with Th from 205 to 255°C and melting temperature of last ice (Tm) from -3 to -9°C. b) L-V inclusions with higher Th from 335 to 385°C and Tm from -11 to -16°C. Type III three-phase carbonic-liquid inclusions (liquid water-liquid CO2-vapour CO2) with Th of 345-385°C. The mean values of the density of ore-forming fluids, pressure and depth of mineralisation have been calculated to be 0.79-0.96 gr/cm3, 2 kbar and 7 km, respectively. The δ18Owater and δD values of the gold-bearing quartz-sulphide veins vary from 7.2‰ to 8‰ and -40.24‰ to -35.28‰, respectively, which are indicative of an isotopically heavy crustal fluid and likely little involvement of meteoric fluid. The δ18Owater values of the quartz-calcite veins have a range of -5.31‰ to -3.35‰, and the δD values of -95.65‰ to -75.31‰, which are clearly lower than those of early-stage quartz-sulphide-gold veins, and are close to the meteoric water line. Based on comparisons of the D-O isotopic systematics, the Qolqoleh ore-mineralising fluids originated from metamorphic devolatilisation of Cretaceous volcano-sedimentary piles. Devolatilisation of these units occurred either synchronously with, or postdates, the development of penetrative (ductile) structures such as shear zones and during overprinting brittle deformation

A Discussion on global tectonics in Proterozoic times - Early and Middle Proterozoic history of the Great Lakes area, North America

1976 ◽  
Vol 280 (1298) ◽  
pp. 605-628 ◽  
Keyword(s):  
North America ◽  
Plate Tectonics ◽  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Tectonic Event ◽  
Early Proterozoic ◽  
Igneous Activity ◽  
Area North ◽  
Orogenic Belts

Two major supracrustal sequences, the Huronian Supergroup in Ontario and the Marquette Range Supergroup and Animikie Group of Michigan and Minnesota, overlie an Archean basement. These sequences are about 2200—2300 Ma and 1900-2000 Ma old respectively. The major Early Proterozoic tectonic event is the ‘Penokean Orogeny’, which occurred about 1850-1900 Ma ago and included deformation, high-grade regional metamorphism, and extrusive and intrusive igneous activity. This was followed by formation of rhyolitic, ignimbritic volcanic rocks and emplacement of associated granites about 1790 Ma ago. The entire region was subsequently subjected to low-grade regional metamorphism 1650-1700 Ma ago, followed by emplacement of anorogenic quartz-monzonite, in part rapakivi, plutons 1500 Ma ago. Late Proterozoic Grenville and Keweenawan events represent the youngest major Precambrian activity in the region. The rocks involved in the Penokean Orogeny lie along the southern margin of the Archean craton of the Superior Province and are interpreted as representing Early Proterozoic cratonic-margin orogenic activity. The distribution of rocks types and structures associated with the Penokean Orogeny and with similar orogenic belts along the margin of the Archean craton of North America suggest that these orogenic belts may have formed as a result of processes similar to modern plate tectonics, although the data are far from conclusive at present.

The petrochemistry of the basic volcanic rocks of the South Connemara Group (Ordovician), western Ireland

1983 ◽  
Vol 120 (2) ◽  
pp. 141-152 ◽  
Author(s):  
P. D. Ryan ◽  
M. D. Max ◽  
T. Kelly
Keyword(s):  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Major And Trace Elements ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
The South ◽  
Northern Margin ◽  
Southern Side ◽  
Western Ireland ◽  
Basic Volcanic

Summary16 samples of Ordovician basic volcanic rocks of the South Connemara Group, which abut the southern side of the metamorphic rocks of the Connemara massif in western Ireland, have been analysed for both major and trace elements. Although subject to low grade regional metamorphism and subsequently hornfelsed by the Galway Granite (400 Ma), their immobile element contents do not appear to be significantly disturbed. These elements characterise the metabasites of the South Connemara Group as ocean floor basalts having their origins in a marginal basin. The Skird Rocks Fault, separating the South Connemara Group from high grade metamorphic rocks of the Connemara massif, is consequently regarded as the northern margin of the vestiges of the lapetus Ocean which can be traced into, and along, the Southern Uplands Fault.

A continuum between structurally controlled Cu-Au and Au-only systems in northern Sweden

2020 ◽  
Author(s):  
Tobias Bauer
Keyword(s):  
Shear Zone ◽  
Lower Order ◽  
Regional Metamorphism ◽  
Massive Sulfide ◽  
Northern Sweden ◽  
Quartz Veins ◽  
Ore Bodies ◽  
Open Question ◽  
Back Arc ◽  
Order Structures

<p>Northern Sweden is dominated by supracrustal and related intrusive rocks formed and deformed during the Svecofennian orogeny (1.90-1.78 Ga). The orogeny comprises several phases of crustal extension and shortening, resulting from subduction and repeated arc-accretion events. An early-Svecofennian extensional phase (c. 1.90-1.88) Ga results in the formation of iron oxide-apatite deposits (IOA, e.g. Kiruna and Malmberget) in the back-arc region and volcanogenic massive sulfide deposits (VMS, e.g. Kristineberg) in the arc. These deposits have been subjected to deformation and regional metamorphism resulting in transposition and re-mobilisation of ore bodies. The latest phase of the Svecofennian orogeny (1.80-1.78 Ga) is characterized by a distinct E-W-directed crustal shortening at high crustal levels representing the last continental assembly resulting from late arc-accretion and followed by a post-orogenic collapse. This leads to folding of early metamorphic fabrics and mainly brittle to brittle-ductile shear zone re-activation. A general N-S gradient from deeper-crustal conditions in Northern Norrbotten (north) to higher-crustal conditions in Västerbotten (south) is observable. The emplacement of syn-tectonic, felsic and mafic intrusive bodies causes high temperature conditions while pressures remain low. Such conditions are favorable for driving fluids and leading to the formation of structurally controlled, Au-bearing deposits in 3<sup>rd</sup> and 4<sup>th</sup> order structures of large, crustal-scale, re-activated shear zone complexes. Deposits in Northern Norrbotten that are related to this late-Svecofennian phase show both ductile and brittle features and host Cu and Au, hence often assigned to the IOCG group of deposits. Deposits that formed during the same phase in Västerbotten are typically characterized by Au-bearing quartz veins that formed as lower-order structures, hence often classified as orogenic Au-deposits. Weather these deposits are entirely newly formed or just represent various grades of re-mobilization of older mineralization remains an open question. Looking at these deposits on a crustal-scale, they represent structurally-controlled deposits, hosted by lower-order structures in re-activated shear zone complexes whereas differences in mineralogy and hydrothermal alteration assemblages are an effect of different crustal levels during formation and differences in host rock compositions.</p>

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

The Role of Epicardial Adipose Tissue Lymphocytes in Low-Grade Inflammation and Coronary Artery Disease

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 469-P
Author(s):  
MILOS MRAZ ◽  
ANNA CINKAJZLOVA ◽  
ZDENA LACINOVÁ ◽  
JANA KLOUCKOVA ◽  
HELENA KRATOCHVILOVA ◽  
...  
Keyword(s):  
Coronary Artery Disease ◽  
Adipose Tissue ◽  
Coronary Artery ◽  
Epicardial Adipose Tissue ◽  
Low Grade ◽  
Artery Disease ◽  
Low Grade Inflammation

scholarly journals Evaluating Targeted Therapies in Ovarian Cancer Metabolism: Novel Role for PCSK9 and Second Generation mTOR Inhibitors

Cancers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 3727
Author(s):  
Dafne Jacome Sanz ◽  
Juuli Raivola ◽  
Hanna Karvonen ◽  
Mariliina Arjama ◽  
Harlan Barker ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Lipid Metabolism ◽  
Cell Survival ◽  
Drug Testing ◽  
Cancer Metabolism ◽  
Ex Vivo ◽  
Specific Inhibitor ◽  
Low Grade ◽  
Serous Ovarian Cancer

Background: Dysregulated lipid metabolism is emerging as a hallmark in several malignancies, including ovarian cancer (OC). Specifically, metastatic OC is highly dependent on lipid-rich omentum. We aimed to investigate the therapeutic value of targeting lipid metabolism in OC. For this purpose, we studied the role of PCSK9, a cholesterol-regulating enzyme, in OC cell survival and its downstream signaling. We also investigated the cytotoxic efficacy of a small library of metabolic (n = 11) and mTOR (n = 10) inhibitors using OC cell lines (n = 8) and ex vivo patient-derived cell cultures (PDCs, n = 5) to identify clinically suitable drug vulnerabilities. Targeting PCSK9 expression with siRNA or PCSK9 specific inhibitor (PF-06446846) impaired OC cell survival. In addition, overexpression of PCSK9 induced robust AKT phosphorylation along with increased expression of ERK1/2 and MEK1/2, suggesting a pro-survival role of PCSK9 in OC cells. Moreover, our drug testing revealed marked differences in cytotoxic responses to drugs targeting metabolic pathways of high-grade serous ovarian cancer (HGSOC) and low-grade serous ovarian cancer (LGSOC) PDCs. Our results show that targeting PCSK9 expression could impair OC cell survival, which warrants further investigation to address the dependency of this cancer on lipogenesis and omental metastasis. Moreover, the differences in metabolic gene expression and drug responses of OC PDCs indicate the existence of a metabolic heterogeneity within OC subtypes, which should be further explored for therapeutic improvements.

scholarly journals Impact of sex in the prevalence and progression of glioblastomas: the role of gonadal steroid hormones

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Claudia Bello-Alvarez ◽  
Ignacio Camacho-Arroyo
Keyword(s):  
Cell Proliferation ◽  
Steroid Hormones ◽  
Physiological State ◽  
Migration And Invasion ◽  
Low Grade ◽  
Main Body ◽  
Protective Effects ◽  
Gonadal Steroid Hormones ◽  
Gonadal Steroid

Abstract Background As in other types of cancers, sex is an essential factor in the origin and progression of glioblastomas. Research in the field of endocrinology and cancer suggests that gonadal steroid hormones play an important role in the progression and prevalence of glioblastomas. In the present review, we aim to discuss the actions and mechanism triggered by gonadal steroid hormones in glioblastomas. Main body Glioblastoma is the most common malignant primary brain tumor. According to the epidemiological data, glioblastomas are more frequent in men than in women in a 1.6/1 proportion both in children and adults. This evidence, and the knowledge about sex influence over the prevalence of countless diseases, suggest that male gonadal steroid hormones, such as testosterone, promote glioblastomas growth. In contrast, a protective role of female gonadal steroid hormones (estradiol and progesterone) against glioblastomas has been questioned. Several pieces of evidence demonstrate a variety of effects induced by female and male gonadal steroid hormones in glioblastomas. Several studies indicate that pregnancy, a physiological state with the highest progesterone and estradiol levels, accelerates the progression of low-grade astrocytomas to glioblastomas and increases the symptoms associated with these tumors. In vitro studies have demonstrated that progesterone has a dual role in glioblastoma cells: physiological concentrations promote cell proliferation, migration, and invasion while very high doses (out physiological range) reduce cell proliferation and increases cell death. Conclusion Gonadal steroid hormones can stimulate the progression of glioblastomas through the increase in proliferation, migration, and invasion. However, the effects mentioned above depend on the concentrations of these hormones and the receptor involved in hormone actions. Estradiol and progesterone can exert promoter or protective effects while the role of testosterone has been always associated to glioblastomas progression.

scholarly journals Inflammatory Mediators and Insulin Resistance in Obesity: Role of Nuclear Receptor Signaling in Macrophages

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Lucía Fuentes ◽  
Tamás Rőszer ◽  
Mercedes Ricote
Keyword(s):  
Insulin Resistance ◽  
Nuclear Receptor ◽  
Cytokine Production ◽  
Current Knowledge ◽  
Liver Steatosis ◽  
Visceral Obesity ◽  
M2 Macrophage ◽  
Low Grade ◽  
The Impact

Visceral obesity is coupled to a general low-grade chronic inflammatory state characterized by macrophage activation and inflammatory cytokine production, leading to insulin resistance (IR). The balance between proinflammatory M1 and antiinflammatory M2 macrophage phenotypes within visceral adipose tissue appears to be crucially involved in the development of obesity-associated IR and consequent metabolic abnormalities. The ligand-dependent transcription factors peroxisome proliferator activated receptors (PPARs) have recently been implicated in the determination of the M1/M2 phenotype. Liver X receptors (LXRs), which form another subgroup of the nuclear receptor superfamily, are also important regulators of proinflammatory cytokine production in macrophages. Disregulation of macrophage-mediated inflammation by PPARs and LXRs therefore underlies the development of IR. This review summarizes the role of PPAR and LXR signaling in macrophages and current knowledge about the impact of these actions in the manifestation of IR and obesity comorbidities such as liver steatosis and diabetic osteopenia.

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