scholarly journals The Orogenic Crixás Gold Deposit, Goiás, Brazil: A Review and New Constraints on the Structural Control of Ore Bodies

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1050
Author(s):  
Stanislav Ulrich ◽  
Steffen Hageman ◽  
Juliana Charão Marques ◽  
Frederico Lana A. R. Figueiredo ◽  
João E. F. Ramires ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Structural Control ◽  
Gold Mineralization ◽  
Current Knowledge ◽  
Current Model ◽  
Regional Scale ◽  
Structural Data ◽  
Stratigraphic Sequence ◽  
Structural Framework ◽  
Ore Bodies

A review of the current knowledge of lithostratigraphy, geochronology, mineralogy, alteration, fluid chemistry and structural data is provided in order to discuss the main controls on mineralization in the Crixás gold deposit and the existing structural framework and evolution. Gold mineralization at Crixás represents orogenic upper mesothermal to lower hypothermal types developed within the overturned Paleoproterozoic (Rhyacian) stratigraphic sequence. The structural data indicates that upright folding of the stratigraphy and formation of a distinct S1 foliation characterizes D1 deformation. This controls the formation of laminated quartz veins, precipitation of Au-rich sulfides, and the development of NW trending orebodies. Localized F2 folding of D1 structures and strong L2 stretching lineations characterizes the D2 event. This localized F2 folding created oreshoots trending W-WNW within distinct orebodies. The D2 deformation is associated with the precipitation of native Au. The ‘bulk plunge’ of these orebodies is a combination of both plunges defined by D1 and D2 deformation events. A critical assessment of lithostratigraphic and structural data reveal two possible tectonic scenarios operating during the Paleoproterozoic. The first possible tectonic scenario considers sagduction and the development of a regional-scale synclinorium, followed by tilting and localized folding of D1 structures. The second scenario, which is similar to the current model, considers accretion producing a synclinorium, followed by thrusting. Based on the current knowledge, both models are considered to be permissible and a series of focused research studies are proposed to test both the current and the new tectonic models.

scholarly journals Structural Control on the Formation of Pb-Zn Deposits: An Example from the Pyrenean Axial Zone

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 489 ◽  
Author(s):  
Alexandre Cugerone ◽  
Emilien Oliot ◽  
Alain Chauvet ◽  
Jordi Gavaldà Bordes ◽  
Angèle Laurent ◽  
...  
Keyword(s):  
Structural Control ◽  
Predominant Role ◽  
Axial Zone ◽  
Regional Deformation ◽  
Structural Framework ◽  
Ore Bodies ◽  
Deformation Event ◽  
Key Parameter

Pb-Zn deposits and specifically Sedimentary-Exhalative (SEDEX) deposits are frequently found in deformed and/or metamorphosed geological terranes. Ore bodies structure is generally difficult to observe and its relationships to the regional structural framework is often lacking. In the Pyrenean Axial Zone (PAZ), the main Pb-Zn mineralizations are commonly considered as Ordovician SEDEX deposits in the literature. New structural field analyzes focusing on the relations between mineralization and regional structures allowed us to classify these Pb-Zn mineralizations into three types: (I) Type 1 corresponds to minor disseminated mineralization, probably syngenetic and from an exhalative source. (II) Type 2a is a stratabound mineralization, epigenetic and synchronous to the Variscan D1 regional deformation event and (III) Type 2b is a vein mineralization, epigenetic and synchronous to the late Variscan D2 regional deformation event. Structural control appears to be a key parameter in concentrating Pb-Zn in the PAZ, as mineralizations occur associated to fold hinges, cleavage, and/or faults. Here we show that the main exploited type 2a and type 2b Pb-Zn mineralizations are intimately controlled by Variscan tectonics. This study demonstrates the predominant role of structural study for unraveling the formation of Pb-Zn deposits especially in deformed/metamorphosed terranes.

scholarly journals Process based inventory of isoprenoid emissions from European forests: model comparisons, current knowledge and uncertainties

2009 ◽  
Vol 9 (2) ◽  
pp. 6147-6206 ◽  
Author(s):  
T. Keenan ◽  
Ü. Niinemets ◽  
S. Sabate ◽  
C. Gracia ◽  
J. Peñuelas
Keyword(s):  
Current Knowledge ◽  
Current Model ◽  
Regional Scale ◽  
Climatic Conditions ◽  
Future Climate ◽  
Interactive Effects ◽  
Future Climate Change ◽  
Model Assessment ◽  
European Forests ◽  
Isoprenoid Emissions

Abstract. Large uncertainties exist in our knowledge of regional emissions of non-methane biogenic volatile organic compounds (BVOC). We address these uncertainties through a two-pronged approach by compiling a state of the art database of the emissions potentials for 80 European forest species, and by a model assessment and inter-comparison, both at the local and regional scale, under present and projected future climatic conditions. We coupled three contrasting isoprenoid models with the ecophysiological forest model GOTILWA+ to explore the interactive effects of climate, vegetation distribution, and productivity, on leaf and ecosystem isoprenoid emissions, and to consider model behaviour in present climate and under projected future climate change conditions. Hourly, daily and annual isoprene emissions as simulated by the models were evaluated against flux measurements. The validation highlighted a general model capacity to capture gross fluxes but inefficiencies in capturing short term variability. A regional inventory of isoprenoid emissions for European forests was created using each of the three modelling approaches. The models agreed on an average European emissions budget of 1.03 TgC a−1 for isoprene and 0.97 TgC a−1 for monoterpenes for the period 1960–1990, which was dominated by a few species with largest aerial coverage. Species contribution to total emissions depended both on species emission potential and geographical distribution. For projected future climate conditions, however, emissions budgets proved highly model dependent, illustrating the current uncertainty associated with isoprenoid emissions responses to potential future conditions. These results suggest that current model estimates of isoprenoid emissions concur well, but future estimates are highly uncertain. We conclude that development of reliable models is highly urgent, but for the time being, future BVOC emission scenario estimates should consider results from an ensemble of available emission models.

Fluid Inclusions and their Geological Significance of Huajian Gold Deposit, Hebei Province, China

2014 ◽  
Vol 962-965 ◽  
pp. 277-281
Author(s):  
Cheng Long Shi ◽  
Yang Song ◽  
Jian Zhong Hu
Keyword(s):  
Gold Deposit ◽  
North China ◽  
Gold Mineralization ◽  
Hebei Province ◽  
North China Block ◽  
Quartz Veins ◽  
Low Salinity ◽  
The North ◽  
Ore Bodies ◽  
Metallogenic Belt

The Huajian gold deposit is located in the metallogenic belt of the northern part of the North China block. This deposit's ore bodies are mainly hosted in metamorphosed Neoarchean and Mesoproterozoic sedimentary rocks, of which Mesozoic volcano-intrusive complexes are closely associated with the Gold mineralization. The FIs of the Huajian deposit are primarily aqueous FIs with minor gas FIs. The pure gas or liquid FIs are very few. The ore-forming fluids were characterised by moderate–low temperature, low salinity and high oxygen fugacity and belonged to an H2O–NaCl ± CO2system. The FIs in quartz veins primarily developed in temperature intervals of 202–380°C, 191–407°C and 170–307°C., corresponding to salinities of 3.85wt.% to 11.23 wt.%, 3.69wt.% to 10.99 wt.% and 2.06wt.% to 17 wt.% NaCl eq.., respectively. The trapping pressures of the FIs from high temperature fluids in the quartz veins are 10-90 MPa, corresponding to depths of 1.0–10 km, assuming a density of the overlying rocks of 0.54 g/cm3–0.98 g/cm3. Multiple stages of phase separation or immiscibility of ore-forming fluid was critical for the formation of the Huajian deposit.

The Saidu Gold Deposit of Southern Altai, China: Mineralizing Stages and Ore-Forming Fluids Evolution

2013 ◽  
Vol 734-737 ◽  
pp. 215-218
Author(s):  
Guo Rui Zhang ◽  
Jiu Hua Xu ◽  
Li Hua Shan ◽  
Hui Zhang ◽  
Xiao Feng Wei
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Tectonic Zone ◽  
Low Salinity ◽  
Ore Bodies ◽  
Evolution Characteristics ◽  
Homogenization Temperatures

The Saidu gold deposit is located in the northwest part of Ertix Tectonic Zone in Xinjiang. The ore bodies occur in altered mylonite zones within the Mar-kakol giant fault zone and are controlled by the ductile shear zone. The structural-metallogenic fluids of the early stage are characterized by mesothermal-hydrothermal CO2-N2-rich fluids, with homogenization temperatures of fluid inclusions being 252~408°C. The tectonic-metallogenic fluids at the middle stage are characterized by CO2-H2O fluids, with homogenization temperatures being 203~326°C. The fluids at the late stage were epithermal-mesothermal low salinity aqueous solutions, with homogenization temperatures being 120~221°C. The main gold mineralization was related to the post-orogenic extension environment, with the evolution characteristics corresponding to the evolution of shear zones.

scholarly journals Process based inventory of isoprenoid emissions from European forests: model comparisons, current knowledge and uncertainties

2009 ◽  
Vol 9 (12) ◽  
pp. 4053-4076 ◽  
Author(s):  
T. Keenan ◽  
Ü. Niinemets ◽  
S. Sabate ◽  
C. Gracia ◽  
J. Peñuelas
Keyword(s):  
Current Knowledge ◽  
Current Model ◽  
Regional Scale ◽  
Climatic Conditions ◽  
Future Climate ◽  
Future Climate Change ◽  
Model Assessment ◽  
Climate Conditions ◽  
European Forests ◽  
Isoprenoid Emissions

Abstract. Large uncertainties exist in our knowledge of regional emissions of non-methane biogenic volatile organic compounds (BVOC). We address these uncertainties through a two-pronged approach by compiling a state of the art database of the emissions potentials for 80 European forest species, and by a model assessment and inter-comparison, both at the local and regional scale, under present and projected future climatic conditions. We coupled three contrasting isoprenoid models with the ecophysiological forest model GOTILWA+ to evaluate leaf and ecosystem isoprenoid emissions, build an emissions inventory for European forests, and to consider model behaviour in present climate and under projected future climate change conditions. Hourly, daily and annual isoprene emissions as simulated by the models were evaluated against flux measurements. The validation highlighted a general model capacity to capture gross fluxes but inefficiencies in capturing short term variability. A regional inventory of isoprenoid emissions for European forests was created using each of the three modelling approaches. The models agreed on an average European emissions budget of 1.03 TgC a−1 for isoprene and 0.97 TgC a−1 for monoterpenes for the period 1960–1990, which was dominated by a few species with largest aerial coverage. Species contribution to total emissions depended both on species emission potential and geographical distribution. For projected future climate conditions, however, emissions budgets proved highly model dependent, illustrating the current uncertainty associated with isoprenoid emissions responses to potential future conditions. These results suggest that current model estimates of isoprenoid emissions concur well, but future estimates are highly uncertain. We conclude that development of reliable models is highly urgent, but for the time being, future BVOC emission scenario estimates should consider results from an ensemble of available emission models.

scholarly journals EPITHERMAL SYSTEMS AND GOLD MINERALIZATION IN WESTERN THRACE (NORTHERN GREECE)

2004 ◽  
Vol 36 (1) ◽  
pp. 416 ◽  
Author(s):  
C. Michael
Keyword(s):  
Gold Deposit ◽  
Structural Control ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Northern Greece ◽  
High Sulfidation ◽  
Epithermal System ◽  
Argillic Alteration ◽  
Low Sulfidation ◽  
Quartz Monzodiorites

Extensive epithermal systems occur within the Tertiary volcanosedimentary basins of western Thrace northern Greece. Gold deposits or perspective gold districts, related to the above epithermal systems have been recently found in the area. The gold mineralization is of the high – sulfidation type and is associated to a diversity in composition and style volcanic activity. Sappes epithermal system is the most important (Saint Demetrios and Viper deposits) and has developed in volcanic "ocks of intermediate composition accompanied by subvolcanic intrusives (dacite - andésites) and plutonio rocks (quartz - monzodiorites). Saint Demetrios and Viper gold deposits are flat lying and of high sulfidation type mineralizations hosted in hydrothermal breccia zones. Petrota epithermal system has developed in volcanoclastic and epiclastic rocks (Perama Hill gold deposit), in rhyolites (location Othontoto) and within hyaloclastites and crystal tuffs (location Mavrokoryfi). The mineralized epithermal zones have strong structural control. Perama gold deposit occurs at the intersection of NS and NW trending epithermal zones. These structures represent the higher grade "feeder" system. Pefka epithermal system is hosted in more acid volcanic vocks (dacites, rhyodacites) and at its southern part (Pasa lofos area) the system is associated with a more alkaline suit (shoshonitic rocks). The mineralized silicifid zones at Pefka mine would correspond to concentric fractures (sheeted fracturing) parallel to the margin of the breccia pipe. The gold mineralization occurs in veins. In general gold occurs in the form of native gold, gold tellurides or it is associated with enargite, luzonite, tetrahedhte. Advanced argillic alteration and intense silicification are very important for the epithermal systems in western Thrace. A unique low - sulfidation occurrence was found at the central and southern part of Sappes area. Adularla was found in veinlets overlapping argillic alteration zones of high - sulfidation system.

Geochronology and structural relationships of mesothermal gold mineralization in the Palaeoproterozoic Jokisivu prospect, southern Finland

2010 ◽  
Vol 147 (4) ◽  
pp. 551-569 ◽  
Author(s):  
K. SAALMANN ◽  
I. MÄNTTÄRI ◽  
P. PELTONEN ◽  
M. J. WHITEHOUSE ◽  
P. GRÖNHOLM ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Regional Scale ◽  
Shear Zones ◽  
Quartz Veins ◽  
Structural Framework ◽  
Structural Relationships ◽  
Three Samples ◽  
Minimum Age ◽  
Zone Development ◽  
Granite Magmatism

AbstractThe palaeoproterozoic Svecofennian orogen in southern Finland contains a number of orogenic gold occurrences. The Jokisivu gold deposit, comprising auriferous quartz veins, is hosted by syn-tectonic quartz diorites to gabbros. Mineralization occurs in approximately WNW–ESE- and WSW–ENE-trending shear zones, which probably branch from regional-scale NW–SE-trending shears. Ore zone fabrics post-date regional-scale folding and the metamorphic peak, and can be correlated with late Svecofennian regional shear tectonics (D6; 1.83–1.78 Ga), indicating that mineralization formed during the late stages of orogenic evolution. SIMS and TIMS U–Pb dating of three samples place tight constraints on the age of gold mineralization. Zircons from both unaltered and altered quartz diorites have ages of 1884±4 Ma and 1881±3 Ma, respectively. These are interpreted as the crystallization age of the rock and as providing the maximum age for mineralization. Zircon rims from an altered quartz diorite from the ore zone give ages of c. 1802±15 Ma, which overlap with the 1801±18 Ma titanite (mean Pb–Pb) age from the ore zone. The ages are similar to the age of the pegmatite dyke that cuts the ore zone and whose zircon age of 1807±3 Ma is approximately the same as the 1791±2 Ma monazite age (TIMS) giving the minimum age of the gold mineralization. The mineralization and its structural framework can be correlated with coeval late Svecofennian shear tectonics related to WNW–ESE-oriented shortening in southern Finland. Extensive c. 1.8 Ga granite magmatism, shear zone development and associated gold mineralization are of regional importance also in the northern and western Fennoscandian Shield (Finnish Lapand and Sweden). A Cordilleran-type setting can explain the widespread distribution of magmatism and gold mineralization associated with shortening, as well as the required heat source triggering hydrothermal fluid flow along shear zones.

The glycomes of Caenorhabditis elegans and other model organisms

2002 ◽  
Vol 69 ◽  
pp. 117-134 ◽  
Author(s):  
Stuart M. Haslam ◽  
David Gems ◽  
Howard R. Morris ◽  
Anne Dell
Keyword(s):  
Caenorhabditis Elegans ◽  
Current Knowledge ◽  
Structural Data ◽  
Model Organisms ◽  
Entire Genome ◽  
C Elegans ◽  
The Face ◽  
Area Of Concern ◽  
Nematode Worm

There is no doubt that the immense amount of information that is being generated by the initial sequencing and secondary interrogation of various genomes will change the face of glycobiological research. However, a major area of concern is that detailed structural knowledge of the ultimate products of genes that are identified as being involved in glycoconjugate biosynthesis is still limited. This is illustrated clearly by the nematode worm Caenorhabditis elegans, which was the first multicellular organism to have its entire genome sequenced. To date, only limited structural data on the glycosylated molecules of this organism have been reported. Our laboratory is addressing this problem by performing detailed MS structural characterization of the N-linked glycans of C. elegans; high-mannose structures dominate, with only minor amounts of complex-type structures. Novel, highly fucosylated truncated structures are also present which are difucosylated on the proximal N-acetylglucosamine of the chitobiose core as well as containing unusual Fucα1–2Gal1–2Man as peripheral structures. The implications of these results in terms of the identification of ligands for genomically predicted lectins and potential glycosyltransferases are discussed in this chapter. Current knowledge on the glycomes of other model organisms such as Dictyostelium discoideum, Saccharomyces cerevisiae and Drosophila melanogaster is also discussed briefly.

scholarly journals Re–Os Pyrite Geochronological Evidence of Three Mineralization Styles within the Jinchang Gold Deposit, Yanji–Dongning Metallogenic Belt, Northeast China

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 448 ◽  
Author(s):  
Shun-Da Li ◽  
Zhi-Gao Wang ◽  
Ke-Yong Wang ◽  
Wen-Yan Cai ◽  
Da-Wei Peng ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Northeast China ◽  
Gold Mineralization ◽  
Metallogenic Belt ◽  
Isotopic Analyses ◽  
Mantle Sources ◽  
Stage 1 ◽  
Geochronological Evidence ◽  
Gold Bearing

The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources.

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