Structural control of ore deposits: The role of pre-existing structures on the formation of mineralized vein systems. Structural control on the formation of Pb-Zn deposits: An example from the Pyrenean axis zone.
Editorial for Special Issue “Structural Control of Mineral Deposits: Theory and Reality”
The example chosen came from the copper deposit of the Tongling Ore District in eastern China. The regional transpressive shear zone of Hajjar (Guemassa massif, Morocco): consequences for the deformation of the massive base metal sulfide ore minerals 2018.8, 435.
Structural Control of Ore Deposits: The Role of Pre-Existing Structures on the Formation of
Introduction
Structural Control of Ore Deposits: The Role of Preexisting Structures in the Formation of. The reuse of some previously formed structures has, in that case, an important but passive role in relation to the formation of the economic feature.
Methodology: Structural Analysis Applied to Metallogeny
In this case, the crack is caused by liquid overpressure and crystallization occurs immediately after the opening with a unique free direction for crystal growth—the vein center. The nature and shape of the fragments (circularity, size, distribution, fabrics, monogenic or polygenic, lithological nature);.
Vein Formation Process and Tectonics: Examples from Ore Deposit Study 1. Gold Concentration during Collapse Tectonics
The first event is the formation of tourmaline-rich haloes in the limestone shale core. In the center of the vein and after the crystallization of ridge quartz (hydrothermal stage), we find a thin fracture in which small white micas, recrystallized quartz and sulfides (essentially arsenopyrite and pyrite) appear.
Discussion and Conclusions
On the distribution of solid inclusions in fibrous vessels and the role of the crack sealing mechanism.J. Structural control and K/Ar dating of Au-Ag epithermal veins in the Cordillera Shila, southern Peru.C.
Structural Control on the Formation of Pb-Zn
Deposits: An Example from the Pyrenean Axial Zone
- Geological Setting
- Structural Analysis of Three Pb-Zn Districts in the Bossòst Anticlinorium
- Comparison with the Pierrefitte Anticlinorium: Pierrefitte and Arre-Anglas-Uzious Districts The Pierrefitte anticlinorium is a 25 × 10 km NNW-SSE anticlinorium located in the western
- Ore Petrology and Microstructures
- Discussion
- Conclusions
The location of the cross-section is shown in Figure 3a (modified from Garcia-Sansegundo and Alonso [56]). It corresponds to the main episode of Pb-Zn mineralization in the PAZ (~95% of the total amount of ore recovered).
Structural Controls of Ore Mineralization in a Polydeformed Basement: Field Examples from the
Geological and Ore Deposits Outline of Baccu Locci Mine District 1. Regional Geology
Lower Permian leucogranitic rocks crop out close to the study area in the Quirra sector [9]; they belong to a calc-alkaline, ferroan, F-bearing, ilmenite-series intrusion, part of a magmatic suite dated at 286±2 Ma [10]. The oldest tectonic features recognizable in the Baccu Locci mining district involve the Lower Carboniferous rocks and are related to the Varic orogeny.
Materials and Methods
Only type (a) and (b) ores are present in the study area, and therefore will be examined in detail in this paper.
Results
The main dip of the mineralized lenses is up to 20◦ towards N 140◦, so more or less in the dip direction of the axis. Swarms of quartz-As-Pb (Zn, Cu, Ag, Au) sulphide hydrothermal veins occur frequently in the Baccu Locci mine area and in several nearby localities along the highly mineralized Baccu Locci shear zone. From the structure map (Figure 3) it is clear that the mineralized faults are parallel to the LD1 antiform axis and are mainly located in the hinge zone.
The dashed box in the small image indicates the location of the outcrop relative to the entire lens-shaped orebody.
Discussion
The aore type is hosted in mylonites that characterize the Baccu Locci shear zone and is located at the top of the hinge of a large LD1 antiform that folds together bedding, D1 fold axial-plane foliation, and mylonitic foliation. From the definition of the Baccu Locci mylonitic shear zone [3], it is well established that the Zn-Cu sulphide lenses developed parallel to the Variscan D1 foliation, both in the axial and mylonitic planes (Figure 6a). There, the availability of detailed mining plans allowed recognition of the tectonic relationship and highlighted the occurrence of large dilatational runs (Figure 13).
This is likely due to a change in D1 foliation posture in the inverted limbs of D2 recumbent folds or to a change in the local stress field.
Conclusions
Internal structure and geochronology of the Gerrei Unit in the Flumendosa area, Variscan External Nappe Zone, Sardinia, Italy. Geology of the Varic basement of the Laconi-Asuni area (central Sardinia, Italy): The core of a regional antiform enveloping a tectonic nappe stack.J. Invisible gold in arsenopyrite from the Variscan Au-Sb Brecca mineralization (Gerrei district, southeastern Sardinia). Geol.
Spatial and temporal distribution of the orogenic gold deposits in the Late Paleozoic Variscides and Southern Tianshan: how orogenic are they? Ore Geol.
Multi-Stage Deformation of the Khangalas Ore Cluster (Verkhoyansk-Kolyma Folded Region,
Materials and Methods
Structural-kinematic studies in the Khangalas Ore Cluster were performed using modern methods [13–17]. Structural data was statistically analyzed and plotted on the upper hemisphere of the Wulff stereographic net. The studies allowed to refine the general architecture of the region, uncover the particularities of the ore-holding structures, identify major structural elements, reconstruct the chronology of deformation events and mineralization, and establish their relationship with regional geodynamic events in Northeast Asia to set.
Geology of the southeastern part of the Kular-Nera shale belt and the Khangalas ore cluster The Kular-Nera shale belt (KNSB) is located in the central part of the Verkhoyansk-Kolyma fold.
Geology of the Southeastern Part of the Kular-Nera Slate Belt and the Khangalas Ore Cluster The Kular-Nera slate belt (KNSB) is situated in the central part of the Verkhoyansk-Kolyma folded
In the central part of the KOC, northward of the Klich-Kontrolnoye occurrence, the Dvoinoy fault adjoins the Khangalas fault. The first field occurs in the southeast of the ore cluster and includes the Khangalas deposit and the Ozhidaniye deposit. Geological sketch map, sections and location of gold deposits and occurrence of the Khangalas ore cluster, modified and supplemented from [2].
Khangalas fault (A) and types of mineralization in the Khangalas ore cluster (KOC):. B) concordant veins, Centralnaya zone of the Khangalas deposit; (C) vein-vein mineralization;.
Deformation Structures of Key Deposits and Localities of the Khangalas Ore Cluster
Analysis of the attitude of quartz veins and spikelets revealed five differently oriented systems (Figures 2 and 3). The deposit is located in the northwestern part of the KOC within the Duk ore field (Figure 5). Kinematic reconstructions of the vein systems revealed their relationship with dextral strike-slip movements (Figure 8H).
Figure 9 shows the stereograms of the main structural elements of the KOC (bedding, rift, quartz veins and veins, as well as mineralized fault zones).
Tectonic Control, Reconstruction and Preservation of the Tiegelongnan Porphyry and Epithermal
Overprinting Cu (Au) Deposit, Central Tibet, China
- The Duolong District
- Tiegelongnan Alteration and Mineralization
- Structures
- Post-Mineral Weathering and Erosion
- Implications and Conclusions
Sericite-pyrite-quartz (phyllic) alteration is widespread in the Tiegelongnan deposit, where most of the ore minerals occur. This could be one of the reasons that porphyry mineralization is overprinted by epithermal mineralization in the Tiegelongnan deposit. In the following excavation rate calculations, the youngest age of formation of the Tiegelongnan deposit was used.
Discovery of the Epithermal Deposition of Cu(Au-Ag) in the Duolong Ore Concentration Area, Tibet.Acta Geosci.
The Jbel Saghro Au(–Ag, Cu) and Ag–Hg
Metallogenetic Province: Product of a Long-Lived Ediacaran Tectono-Magmatic Evolution in the
Geological Overview of the Anti-Atlas Mountains
In the eastern Anti-Atlas of interest, Jbel Saghro, Paleoproterozoic terranes are not exposed (Figures 1b and 2), so the oldest rock outcrops consist of middle Neoproterozoic (Cryogene) metasedimentary rocks [91,92]. Thus, many authors suggest, for example, that brittle deformations associated with Variscan compression occur throughout the Anti-Atlas and reactive structures from the Precambrian basement. Ductile deformation associated with Variscan tectonics has not yet been described in the Anti-Atlas.
However, with a maximum thickness of only 4 km, such ductile deformations seem excluded in the Eastern Anti-Atlas.
Tectono-Magmatic Evolution of the Jbel Saghro
The structural boundary of the proposed Qal'at Mgouna caldera can be traced over 5–6 km. To the north, the intracaldera sequence disappears beneath the young sedimentary rocks of the Dadès valley (Figure 5). In the vicinity of Awrir-n-Tamgalount (Figure 5), the extra-caldera sequences are made up of two units overlain by the Tamgalount tuff (Figure 7d,e).
By analogy with the Isk-n-Alla monzogranite in the central part of Jbel Saghro (Fig. 2), they may have been emplaced around 555 Ma [29,106].
Characteristics of Ore Deposits
The age of the mineralizations in the Jbel Saghro remains limited due to the lack of absolute dating. The distribution of the Central Iapetus Magmatic Province (CIMP) in West African craton: U-Pb dating, geochemistry and petrology from Douar Eç-çour and imiter mafic Dyke Swarms (High and Anti-Atlas, Morocco). Petrography and geochemistry of the Bou Teglimt, Taouzzakt and Igoudrane intrusions in the Eastern Saghro (Anti Atlas, Morocco).
New data for the geotectonic evolution of the Pan-African belt in the eastern Anti-Atlas (Morocco). Ore Geol.
Fault Zone Evolution and Development of
Geological Setting 1. Regional Geological Setting
The Kiggavik area is located on the eastern margin of the Proterozoic intracratonic Thelon Basin (ca Ma, [32,33]) in Nunavut, Canada, within Churchill Province. The Thelon Basin is one analogue of the Athabasca Basin and the Kiggavik area exhibits several economically significant uranium orebodies: Four of the deposits yield calculated resources of 48,953 t of uranium at a grade of 0.47% U [35]. At the end of the Trans-Hudsonian orogeny, the Baker Lake basin developed as a result of (retro-arc) extensional to transtensional rift tectonics [36], and was filled with sedimentary and bi-modal volcanic-sedimentary rocks (Baker Lake and Wharton Grps, ca Ma, [37,38]).
These rocks, together with overlying Paleoproterozoic Ma) rocks of the Ketyet River Group [53], comprise a prominent unit of orthoquartzite [52].
Sampling and Methods
Groups bearing veins of the QB are observed in the sandstones of the Thelon Formation. The quartz veins of the QB were observed in several places cutting across the cataclasites (Figure 4B). The clarity of the latest generation of quartz (ie euhedral quartz-filling vugs and open fractures) is dark blue with rare concentric zoning.
250◦C (i.e., the range of temperatures detected from low-salinity fluid inclusions), to be representative of the quartz generations of the QB, and 100–200◦C, on average.
Interpretation of Results and Discussion 1. Origin and Nature of Silicifying Fluids
Fault zone processes leading to the formation of the QB: cataclasis, silicification and hydraulic breccia. This boiling process is aided by the monophasic liquid inclusions in the quartz generations of the QB. Uranium minerals and associated specific luminescence are only observed in the vicinity of the QB.
Petrography, fluid inclusion analysis and geochronology of the final uranium deposit, Kiggavik, Nunavut, Canada. Miner.
Structural Control on Clay Mineral Authigenesis in Faulted Arkosic Sandstone of the Rio do Peixe
Basin, Brazil
Geological Background of the Rio do Peixe Basin
The basin was created during the reactivation of Precambrian basement shear zones during the opening of the South Atlantic Ocean [27-30]. The formation consists of siliciclastic fluvial deposits that are exposed in large and continuous outcrops in different sectors of the basin (Figure 1). The Rio Piranhas Formation is the main unit and consists of conglomerates and coarse sandstones interbedded with sandy mudstones [ 32 ].
Simplified geological map of the Rio do Peixe basin, showing major faults and the lithostratigraphic units.
Methods and Materials
The fracture zones studied show three major structural domains (Figure 2): (1) the host rock, that is, the undeformed sandstones and conglomerates without any significant deformation features; 2) the core of the fracture, where most of the fracture is located; and (3) the surrounding base wall and hanging wall damage zones, located between the host rock and the fault core, and composed of deformation bands. The damage zone is the deformed rock volume adjacent to the fault core with single or clusters of deformation bands (sites 2, 3 and 4 in this study). Schematic profile and compositional classification of the host rock (Antenor Navarro Formation) in the Rio do Peixe basin, site 1. A) Photograph of an outcrop showing sedimentary structures in the river with tabular and lenticular forms of fine sandstone and trough festoon conglomerates.
In the fault cores, the visual porosity determined using the optical microscope is practically zero due to the presence of the cataclastic matrix (Figure 6F).
